Sensors

Editorial

Jump to: Research, Review, Other

4 pages, 152 KiB

Open AccessEditorial

Sensors for Indoor Mapping and Navigation

by Kourosh Khoshelham and Sisi Zlatanova

Sensors 2016, 16(5), 655; https://doi.org/10.3390/s16050655 - 9 May 2016

Cited by 28 | Viewed by 9964

Abstract

With the growth of cities and increased urban population there is a growing demand for spatial information of large indoor environments.[...] Full article

(This article belongs to the Special Issue Sensors for Indoor Mapping and Navigation)

Research

Jump to: Editorial, Review, Other

12 pages, 3219 KiB

Open AccessArticle

Remote Evaluation of Rotational Velocity Using a Quadrant Photo-Detector and a DSC Algorithm

by Xiangkai Zeng, Zhixiong Zhu and Yang Chen

Sensors 2016, 16(5), 587; https://doi.org/10.3390/s16050587 - 25 Apr 2016

Cited by 7 | Viewed by 4837

Abstract

This paper presents an approach to remotely evaluate the rotational velocity of a measured object by using a quadrant photo-detector and a differential subtraction correlation (DSC) algorithm. The rotational velocity of a rotating object is determined by two temporal-delay numbers at the minima [...] Read more.

This paper presents an approach to remotely evaluate the rotational velocity of a measured object by using a quadrant photo-detector and a differential subtraction correlation (DSC) algorithm. The rotational velocity of a rotating object is determined by two temporal-delay numbers at the minima of two DSCs that are derived from the four output signals of the quadrant photo-detector, and the sign of the calculated rotational velocity directly represents the rotational direction. The DSC algorithm does not require any multiplication operations. Experimental calculations were performed to confirm the proposed evaluation method. The calculated rotational velocity, including its amplitude and direction, showed good agreement with the given one, which had an amplitude error of ~0.3%, and had over 1100 times the efficiency of the traditional cross-correlation method in the case of data number N > 4800. The confirmations have shown that the remote evaluation of rotational velocity can be done without any circular division disk, and that it has much fewer error sources, making it simple, accurate and effective for remotely evaluating rotational velocity. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

19 pages, 10383 KiB

Open AccessArticle

Robust Stability of Scaled-Four-Channel Teleoperation with Internet Time-Varying Delays

by Emma Delgado, Antonio Barreiro, Pablo Falcón and Miguel Díaz-Cacho

Sensors 2016, 16(5), 593; https://doi.org/10.3390/s16050593 - 26 Apr 2016

Cited by 8 | Viewed by 5714

Abstract

We describe the application of a generic stability framework for a teleoperation system under time-varying delay conditions, as addressed in a previous work, to a scaled-four-channel (γ-4C) control scheme. Described is how varying delays are dealt with by means of dynamic encapsulation, giving [...] Read more.

We describe the application of a generic stability framework for a teleoperation system under time-varying delay conditions, as addressed in a previous work, to a scaled-four-channel (γ-4C) control scheme. Described is how varying delays are dealt with by means of dynamic encapsulation, giving rise to mu-test conditions for robust stability and offering an appealing frequency technique to deal with the stability robustness of the architecture. We discuss ideal transparency problems and we adapt classical solutions so that controllers are proper, without single or double differentiators, and thus avoid the negative effects of noise. The control scheme was fine-tuned and tested for complete stability to zero of the whole state, while seeking a practical solution to the trade-off between stability and transparency in the Internet-based teleoperation. These ideas were tested on an Internet-based application with two Omni devices at remote laboratory locations via simulations and real remote experiments that achieved robust stability, while performing well in terms of position synchronization and force transparency. Full article

(This article belongs to the Special Issue Advances on Resources Management for Multi-Platform Infrastructures)

► Show Figures

Graphical abstract

25 pages, 17673 KiB

Open AccessArticle

A Comparative Analysis of Machine Learning with WorldView-2 Pan-Sharpened Imagery for Tea Crop Mapping

by Yung-Chung Matt Chuang and Yi-Shiang Shiu

Sensors 2016, 16(5), 594; https://doi.org/10.3390/s16050594 - 26 Apr 2016

Cited by 41 | Viewed by 8879

Abstract

Tea is an important but vulnerable economic crop in East Asia, highly impacted by climate change. This study attempts to interpret tea land use/land cover (LULC) using very high resolution WorldView-2 imagery of central Taiwan with both pixel and object-based approaches. A total [...] Read more.

Tea is an important but vulnerable economic crop in East Asia, highly impacted by climate change. This study attempts to interpret tea land use/land cover (LULC) using very high resolution WorldView-2 imagery of central Taiwan with both pixel and object-based approaches. A total of 80 variables derived from each WorldView-2 band with pan-sharpening, standardization, principal components and gray level co-occurrence matrix (GLCM) texture indices transformation, were set as the input variables. For pixel-based image analysis (PBIA), 34 variables were selected, including seven principal components, 21 GLCM texture indices and six original WorldView-2 bands. Results showed that support vector machine (SVM) had the highest tea crop classification accuracy (OA = 84.70% and KIA = 0.690), followed by random forest (RF), maximum likelihood algorithm (ML), and logistic regression analysis (LR). However, the ML classifier achieved the highest classification accuracy (OA = 96.04% and KIA = 0.887) in object-based image analysis (OBIA) using only six variables. The contribution of this study is to create a new framework for accurately identifying tea crops in a subtropical region with real-time high-resolution WorldView-2 imagery without field survey, which could further aid agriculture land management and a sustainable agricultural product supply. Full article

(This article belongs to the Special Issue Sensors for Agriculture)

► Show Figures

Graphical abstract

17 pages, 4085 KiB

Open AccessArticle

Static and Wind-on Performance of Polymer-Based Pressure-Sensitive Paints Using Platinum and Ruthenium as the Luminophore

by Kin Hing Lo and Konstantinos Kontis

Sensors 2016, 16(5), 595; https://doi.org/10.3390/s16050595 - 26 Apr 2016

Cited by 15 | Viewed by 5889

Abstract

An experimental study has been conducted to investigate the static and wind-on performance of two in-house-developed polymer-based pressure-sensitive paints. Platinum tetrakis (pentafluorophenyl) porphyrin and tris-bathophenanthroline ruthenium II are used as the luminophores of these two polymer-based pressure-sensitive paints. The pressure and temperature sensitivity [...] Read more.

An experimental study has been conducted to investigate the static and wind-on performance of two in-house-developed polymer-based pressure-sensitive paints. Platinum tetrakis (pentafluorophenyl) porphyrin and tris-bathophenanthroline ruthenium II are used as the luminophores of these two polymer-based pressure-sensitive paints. The pressure and temperature sensitivity and the photo-degradation rate of these two pressure-sensitive paints have been investigated. In the wind tunnel test, it was observed that the normalised intensity ratio of both polymer-based pressure-sensitive paints being studied decreases with increasing the number of wind tunnel runs. The exact reason that leads to the occurrence of this phenomenon is unclear, but it is deduced that the luminophore is either removed or deactivated by the incoming flow during a wind tunnel test. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

20 pages, 8726 KiB

Open AccessArticle

Smartphone-Based Indoor Localization with Bluetooth Low Energy Beacons

by Yuan Zhuang, Jun Yang, You Li, Longning Qi and Naser El-Sheimy

Sensors 2016, 16(5), 596; https://doi.org/10.3390/s16050596 - 26 Apr 2016

Cited by 411 | Viewed by 21541

Abstract

Indoor wireless localization using Bluetooth Low Energy (BLE) beacons has attracted considerable attention after the release of the BLE protocol. In this paper, we propose an algorithm that uses the combination of channel-separate polynomial regression model (PRM), channel-separate fingerprinting (FP), outlier detection and [...] Read more.

Indoor wireless localization using Bluetooth Low Energy (BLE) beacons has attracted considerable attention after the release of the BLE protocol. In this paper, we propose an algorithm that uses the combination of channel-separate polynomial regression model (PRM), channel-separate fingerprinting (FP), outlier detection and extended Kalman filtering (EKF) for smartphone-based indoor localization with BLE beacons. The proposed algorithm uses FP and PRM to estimate the target’s location and the distances between the target and BLE beacons respectively. We compare the performance of distance estimation that uses separate PRM for three advertisement channels (i.e., the separate strategy) with that use an aggregate PRM generated through the combination of information from all channels (i.e., the aggregate strategy). The performance of FP-based location estimation results of the separate strategy and the aggregate strategy are also compared. It was found that the separate strategy can provide higher accuracy; thus, it is preferred to adopt PRM and FP for each BLE advertisement channel separately. Furthermore, to enhance the robustness of the algorithm, a two-level outlier detection mechanism is designed. Distance and location estimates obtained from PRM and FP are passed to the first outlier detection to generate improved distance estimates for the EKF. After the EKF process, the second outlier detection algorithm based on statistical testing is further performed to remove the outliers. The proposed algorithm was evaluated by various field experiments. Results show that the proposed algorithm achieved the accuracy of <2.56 m at 90% of the time with dense deployment of BLE beacons (1 beacon per 9 m), which performs 35.82% better than <3.99 m from the Propagation Model (PM) + EKF algorithm and 15.77% more accurate than <3.04 m from the FP + EKF algorithm. With sparse deployment (1 beacon per 18 m), the proposed algorithm achieves the accuracies of <3.88 m at 90% of the time, which performs 49.58% more accurate than <8.00 m from the PM + EKF algorithm and 21.41% better than <4.94 m from the FP + EKF algorithm. Therefore, the proposed algorithm is especially useful to improve the localization accuracy in environments with sparse beacon deployment. Full article

(This article belongs to the Special Issue Data in the IoT: from Sensing to Meaning)

► Show Figures

Graphical abstract

23 pages, 8971 KiB

Open AccessArticle

Streetlight Control System Based on Wireless Communication over DALI Protocol

by Francisco José Bellido-Outeiriño, Francisco Javier Quiles-Latorre, Carlos Diego Moreno-Moreno, José María Flores-Arias, Isabel Moreno-García and Manuel Ortiz-López

Sensors 2016, 16(5), 597; https://doi.org/10.3390/s16050597 - 27 Apr 2016

Cited by 44 | Viewed by 13137

Abstract

Public lighting represents a large part of the energy consumption of towns and cities. Efficient management of public lighting can entail significant energy savings. This work presents a smart system for managing public lighting networks based on wireless communication and the DALI protocol. [...] Read more.

Public lighting represents a large part of the energy consumption of towns and cities. Efficient management of public lighting can entail significant energy savings. This work presents a smart system for managing public lighting networks based on wireless communication and the DALI protocol. Wireless communication entails significant economic savings, as there is no need to install new wiring and visual impacts and damage to the facades of historical buildings in city centers are avoided. The DALI protocol uses bidirectional communication with the ballast, which allows its status to be controlled and monitored at all times. The novelty of this work is that it tackles all aspects related to the management of public lighting: a standard protocol, DALI, was selected to control the ballast, a wireless node based on the IEEE 802.15.4 standard with a DALI interface was designed, a network layer that considers the topology of the lighting network has been developed, and lastly, some user-friendly applications for the control and maintenance of the system by the technical crews of the different towns and cities have been developed. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2016)

► Show Figures

Graphical abstract

9 pages, 2400 KiB

Open AccessArticle

Enhanced Tissue Ablation Efficiency with a Mid-Infrared Nonlinear Frequency Conversion Laser System and Tissue Interaction Monitoring Using Optical Coherence Tomography

by Bongkyun Kim and Dae Yu Kim

Sensors 2016, 16(5), 598; https://doi.org/10.3390/s16050598 - 26 Apr 2016

Cited by 15 | Viewed by 6672

Abstract

We report development of optical parametric oscillator (OPO)-based mid-infrared laser system that utilizes a periodically poled nonlinear crystal pumped by a near-infrared (NIR) laser. We obtained a mid-infrared average output of 8 W at an injection current of 20 A from a quasi-phase-matched [...] Read more.

We report development of optical parametric oscillator (OPO)-based mid-infrared laser system that utilizes a periodically poled nonlinear crystal pumped by a near-infrared (NIR) laser. We obtained a mid-infrared average output of 8 W at an injection current of 20 A from a quasi-phase-matched OPO using an external cavity configuration. Laser tissue ablation efficiency is substantially affected by several parameters, including an optical fluence rate, wavelength of the laser source, and the optical properties of target tissue. Dimensions of wavelength and radiant exposure dependent tissue ablation are quantified using Fourier domain optical coherence tomography and the ablation efficiency was compared to a non-converted NIR laser system. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

26 pages, 7729 KiB

Open AccessArticle

Traffic Congestion Detection System through Connected Vehicles and Big Data

by Néstor Cárdenas-Benítez, Raúl Aquino-Santos, Pedro Magaña-Espinoza, José Aguilar-Velazco, Arthur Edwards-Block and Aldo Medina Cass

Sensors 2016, 16(5), 599; https://doi.org/10.3390/s16050599 - 28 Apr 2016

Cited by 76 | Viewed by 17365

Abstract

This article discusses the simulation and evaluation of a traffic congestion detection system which combines inter-vehicular communications, fixed roadside infrastructure and infrastructure-to-infrastructure connectivity and big data. The system discussed in this article permits drivers to identify traffic congestion and change their routes accordingly, [...] Read more.

This article discusses the simulation and evaluation of a traffic congestion detection system which combines inter-vehicular communications, fixed roadside infrastructure and infrastructure-to-infrastructure connectivity and big data. The system discussed in this article permits drivers to identify traffic congestion and change their routes accordingly, thus reducing the total emissions of CO₂ and decreasing travel time. This system monitors, processes and stores large amounts of data, which can detect traffic congestion in a precise way by means of a series of algorithms that reduces localized vehicular emission by rerouting vehicles. To simulate and evaluate the proposed system, a big data cluster was developed based on Cassandra, which was used in tandem with the OMNeT++ discreet event network simulator, coupled with the SUMO (Simulation of Urban MObility) traffic simulator and the Veins vehicular network framework. The results validate the efficiency of the traffic detection system and its positive impact in detecting, reporting and rerouting traffic when traffic events occur. Full article

(This article belongs to the Special Issue Data in the IoT: from Sensing to Meaning)

► Show Figures

Graphical abstract

15 pages, 2666 KiB

Open AccessArticle

Numerical Simulation of Output Response of PVDF Sensor Attached on a Cantilever Beam Subjected to Impact Loading

by Cao Vu Dung and Eiichi Sasaki

Sensors 2016, 16(5), 601; https://doi.org/10.3390/s16050601 - 27 Apr 2016

Cited by 29 | Viewed by 11338

Abstract

Polyvinylidene Flouride (PVDF) is a film-type polymer that has been used as sensors and actuators in various applications due to its mechanical toughness, flexibility, and low density. A PVDF sensor typically covers an area of the host structure over which mechanical stress/strain is [...] Read more.

Polyvinylidene Flouride (PVDF) is a film-type polymer that has been used as sensors and actuators in various applications due to its mechanical toughness, flexibility, and low density. A PVDF sensor typically covers an area of the host structure over which mechanical stress/strain is averaged and converted to electrical energy. This study investigates the fundamental “stress-averaging” mechanism for dynamic strain sensing in the in-plane mode. A numerical simulation was conducted to simulate the “stress-averaging” mechanism of a PVDF sensor attached on a cantilever beam subjected to an impact loading, taking into account the contribution of piezoelectricity, the cantilever beam’s modal properties, and electronic signal conditioning. Impact tests and FEM analysis were also carried out to verify the numerical simulation results. The results of impact tests indicate the excellent capability of the attached PVDF sensor in capturing the fundamental natural frequencies of the cantilever beam. There is a good agreement between the PVDF sensor’s output voltage predicted by the numerical simulation and that obtained in the impact tests. Parametric studies were conducted to investigate the effects of sensor size and sensor position and it is shown that a larger sensor tends to generate higher output voltage than a smaller one at the same location. However, the effect of sensor location seems to be more significant for larger sensors due to the cancelling problem. Overall, PVDF sensors exhibit excellent sensing capability for in-plane dynamic strain induced by impact loading. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Graphical abstract

19 pages, 2567 KiB

Open AccessArticle

Hydrophobin-Based Surface Engineering for Sensitive and Robust Quantification of Yeast Pheromones

by Stefan Hennig, Gerhard Rödel and Kai Ostermann

Sensors 2016, 16(5), 602; https://doi.org/10.3390/s16050602 - 27 Apr 2016

Cited by 19 | Viewed by 7562

Abstract

Detection and quantification of small peptides, such as yeast pheromones, are often challenging. We developed a highly sensitive and robust affinity-assay for the quantification of the α-factor pheromone of Saccharomyces cerevisiae based on recombinant hydrophobins. These small, amphipathic proteins self-assemble into highly stable [...] Read more.

Detection and quantification of small peptides, such as yeast pheromones, are often challenging. We developed a highly sensitive and robust affinity-assay for the quantification of the α-factor pheromone of Saccharomyces cerevisiae based on recombinant hydrophobins. These small, amphipathic proteins self-assemble into highly stable monolayers at hydrophilic-hydrophobic interfaces. Upon functionalization of solid supports with a combination of hydrophobins either lacking or exposing the α-factor, pheromone-specific antibodies were bound to the surface. Increasing concentrations of the pheromone competitively detached the antibodies, thus allowing for quantification of the pheromone. By adjusting the percentage of pheromone-exposing hydrophobins, the sensitivity of the assay could be precisely predefined. The assay proved to be highly robust against changes in sample matrix composition. Due to the high stability of hydrophobin layers, the functionalized surfaces could be repeatedly used without affecting the sensitivity. Furthermore, by using an inverse setup, the sensitivity was increased by three orders of magnitude, yielding a novel kind of biosensor for the yeast pheromone with the lowest limit of detection reported so far. This assay was applied to study the pheromone secretion of diverse yeast strains including a whole-cell biosensor strain of Schizosaccharomyces pombe modulating α-factor secretion in response to an environmental signal. Full article

(This article belongs to the Section Biosensors)

► Show Figures

Graphical abstract

13 pages, 4170 KiB

Open AccessArticle

Prediction of the Strain Response of Poly-AlN/(100)Si Surface Acoustic Wave Resonator and Experimental Analysis

by Shuo Chen and Zheng You

Sensors 2016, 16(5), 603; https://doi.org/10.3390/s16050603 - 27 Apr 2016

Cited by 3 | Viewed by 6091

Abstract

The strain sensitivity of the Aluminum Nitride (AlN)/Silicon (Si) surface acoustic wave resonator (SAWR) is predicted based on a modeling method introduced in this work, and further compared with experimental results. The strain influence on both the period of the inter-digital transducer (IDT) [...] Read more.

The strain sensitivity of the Aluminum Nitride (AlN)/Silicon (Si) surface acoustic wave resonator (SAWR) is predicted based on a modeling method introduced in this work, and further compared with experimental results. The strain influence on both the period of the inter-digital transducer (IDT) and the sound velocity is taken into consideration when modeling the strain response. From the modeling results, AlN and Si have opposite responses to strain; hence, for the AlN/Si-based SAWR, both a positive and a negative strain coefficient factor can be achieved by changing the thickness of the AlN layer, which is confirmed by strain response testing based on a silicon cantilever structure with two AlN configurations (1 μm and 3 μm in thickness, respectively). Full article

(This article belongs to the Special Issue Resonator Sensors)

► Show Figures

Figure 1

21 pages, 5091 KiB

Open AccessArticle

Theoretical Design of a Depolarized Interferometric Fiber-Optic Gyroscope (IFOG) on SMF-28 Single-Mode Standard Optical Fiber Based on Closed-Loop Sinusoidal Phase Modulation with Serrodyne Feedback Phase Modulation Using Simulation Tools for Tactical and Industrial Grade Applications

by Ramón José Pérez, Ignacio Álvarez and José María Enguita

Sensors 2016, 16(5), 604; https://doi.org/10.3390/s16050604 - 27 Apr 2016

Cited by 10 | Viewed by 13203

Abstract

This article presents, by means of computational simulation tools, a full analysis and design of an Interferometric Fiber-Optic Gyroscope (IFOG) prototype based on a closed-loop configuration with sinusoidal bias phase- modulation. The complete design of the different blocks, optical and electronic, is presented, [...] Read more.

This article presents, by means of computational simulation tools, a full analysis and design of an Interferometric Fiber-Optic Gyroscope (IFOG) prototype based on a closed-loop configuration with sinusoidal bias phase- modulation. The complete design of the different blocks, optical and electronic, is presented, including some novelties as the sinusoidal bias phase-modulation and the use of an integrator to generate the serrodyne phase-modulation signal. The paper includes detailed calculation of most parameter values, and the plots of the resulting signals obtained from simulation tools. The design is focused in the use of a standard single-mode optical fiber, allowing a cost competitive implementation compared to commercial IFOG, at the expense of reduced sensitivity. The design contains an IFOG model that accomplishes tactical and industrial grade applications (sensitivity ≤ 0.055 °/h). This design presents two important properties: (1) an optical subsystem with advanced conception: depolarization of the optical wave by means of Lyot depolarizers, which allows to use a sensing coil made by standard optical fiber, instead by polarization maintaining fiber, which supposes consequent cost savings and (2) a novel and simple electronic design that incorporates a linear analog integrator with reset in feedback chain, this integrator generating a serrodyne voltage-wave to apply to Phase-Modulator (PM), so that it will be obtained the interferometric phase cancellation. This particular feedback design with sawtooth-wave generated signal for a closed-loop configuration with sinusoidal bias phase modulation has not been reported till now in the scientific literature and supposes a considerable simplification with regard to previous designs based on similar configurations. The sensing coil consists of an 8 cm average diameter spool that contains 300 m of standard single-mode optical-fiber (SMF-28 type) realized by quadrupolar winding. The working wavelength will be 1310 nm. The theoretical calculated values of threshold sensitivity and dynamic range for this prototype are 0.052 °/h and 101.38 dB (from ±1.164 × 10⁻⁵ °/s up to ±78.19 °/s), respectively. The Scale-Factor (SF) non-linearity for this model is 5.404% relative to full scale, this value being obtained from data simulation results. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2015)

► Show Figures

Graphical abstract

21 pages, 3214 KiB

Open AccessArticle

Quaternion-Based Gesture Recognition Using Wireless Wearable Motion Capture Sensors

by Shamir Alavi, Dennis Arsenault and Anthony Whitehead

Sensors 2016, 16(5), 605; https://doi.org/10.3390/s16050605 - 28 Apr 2016

Cited by 43 | Viewed by 11215

Abstract

This work presents the development and implementation of a unified multi-sensor human motion capture and gesture recognition system that can distinguish between and classify six different gestures. Data was collected from eleven participants using a subset of five wireless motion sensors (inertial measurement [...] Read more.

This work presents the development and implementation of a unified multi-sensor human motion capture and gesture recognition system that can distinguish between and classify six different gestures. Data was collected from eleven participants using a subset of five wireless motion sensors (inertial measurement units) attached to their arms and upper body from a complete motion capture system. We compare Support Vector Machines and Artificial Neural Networks on the same dataset under two different scenarios and evaluate the results. Our study indicates that near perfect classification accuracies are achievable for small gestures and that the speed of classification is sufficient to allow interactivity. However, such accuracies are more difficult to obtain when a participant does not participate in training, indicating that more work needs to be done in this area to create a system that can be used by the general population. Full article

(This article belongs to the Special Issue Sensors for Entertainment)

► Show Figures

Graphical abstract

14 pages, 3176 KiB

Open AccessArticle

Sorption and Diffusion of Water Vapor and Carbon Dioxide in Sulfonated Polyaniline as Chemical Sensing Materials

by Qiuhua Liang, Junke Jiang, Huaiyu Ye, Ning Yang, Miao Cai, Jing Xiao and Xianping Chen

Sensors 2016, 16(5), 606; https://doi.org/10.3390/s16050606 - 27 Apr 2016

Cited by 19 | Viewed by 6636

Abstract

A hybrid quantum mechanics (QM)/molecular dynamics (MD) simulation is performed to investigate the effect of an ionizable group (–SO₃⁻Na⁺) on polyaniline as gas sensing materials. Polymers considered for this work include emeraldine base of polyaniline (EB-PANI) and its [...] Read more.

A hybrid quantum mechanics (QM)/molecular dynamics (MD) simulation is performed to investigate the effect of an ionizable group (–SO₃⁻Na⁺) on polyaniline as gas sensing materials. Polymers considered for this work include emeraldine base of polyaniline (EB-PANI) and its derivatives (Na-SPANI (I), (II) and (III)) whose rings are partly monosubstituted by –SO₃⁻Na⁺. The hybrid simulation results show that the adsorption energy, Mulliken charge and band gap of analytes (CO₂ and H₂O) in polyaniline are relatively sensitive to the position and the amounts of –SO₃⁻Na⁺, and these parameters would affect the sensitivity of Na-SPANI/EB-PANI towards CO₂. The sensitivity of Na-SPANI (III)/EB-PANI towards CO₂ can be greatly improved by two orders of magnitude, which is in agreement with the experimental study. In addition, we also demonstrate that introducing –SO₃⁻Na⁺ groups at the rings can notably affect the gas transport properties of polyaniline. Comparative studies indicate that the effect of ionizable group on polyaniline as gas sensing materials for the polar gas molecule (H₂O) is more significant than that for the nonpolar gas molecule (CO₂). These findings contribute in the functionalization-induced variations of the material properties of polyaniline for CO₂ sensing and the design of new polyaniline with desired sensing properties. Full article

(This article belongs to the Special Issue The Use of New and/or Improved Materials for Sensing Applications)

► Show Figures

Graphical abstract

19 pages, 1205 KiB

Open AccessArticle

An Embedded Sensor Node Microcontroller with Crypto-Processors

by Goran Panić, Oliver Stecklina and Zoran Stamenković

Sensors 2016, 16(5), 607; https://doi.org/10.3390/s16050607 - 27 Apr 2016

Cited by 10 | Viewed by 7032

Abstract

Wireless sensor network applications range from industrial automation and control, agricultural and environmental protection, to surveillance and medicine. In most applications, data are highly sensitive and must be protected from any type of attack and abuse. Security challenges in wireless sensor networks are [...] Read more.

Wireless sensor network applications range from industrial automation and control, agricultural and environmental protection, to surveillance and medicine. In most applications, data are highly sensitive and must be protected from any type of attack and abuse. Security challenges in wireless sensor networks are mainly defined by the power and computing resources of sensor devices, memory size, quality of radio channels and susceptibility to physical capture. In this article, an embedded sensor node microcontroller designed to support sensor network applications with severe security demands is presented. It features a low power 16-bitprocessor core supported by a number of hardware accelerators designed to perform complex operations required by advanced crypto algorithms. The microcontroller integrates an embedded Flash and an 8-channel 12-bit analog-to-digital converter making it a good solution for low-power sensor nodes. The article discusses the most important security topics in wireless sensor networks and presents the architecture of the proposed hardware solution. Furthermore, it gives details on the chip implementation, verification and hardware evaluation. Finally, the chip power dissipation and performance figures are estimated and analyzed. Full article

(This article belongs to the Special Issue Security and Privacy in Sensor Networks)

► Show Figures

Graphical abstract

14 pages, 2860 KiB

Open AccessArticle

The DEPFET Sensor-Amplifier Structure: A Method to Beat 1/f Noise and Reach Sub-Electron Noise in Pixel Detectors

by Gerhard Lutz, Matteo Porro, Stefan Aschauer, Stefan Wölfel and Lothar Strüder

Sensors 2016, 16(5), 608; https://doi.org/10.3390/s16050608 - 28 Apr 2016

Cited by 12 | Viewed by 9297

Abstract

Depleted field effect transistors (DEPFET) are used to achieve very low noise signal charge readout with sub-electron measurement precision. This is accomplished by repeatedly reading an identical charge, thereby suppressing not only the white serial noise but also the usually constant 1/f noise. [...] Read more.

Depleted field effect transistors (DEPFET) are used to achieve very low noise signal charge readout with sub-electron measurement precision. This is accomplished by repeatedly reading an identical charge, thereby suppressing not only the white serial noise but also the usually constant 1/f noise. The repetitive non-destructive readout (RNDR) DEPFET is an ideal central element for an active pixel sensor (APS) pixel. The theory has been derived thoroughly and results have been verified on RNDR-DEPFET prototypes. A charge measurement precision of 0.18 electrons has been achieved. The device is well-suited for spectroscopic X-ray imaging and for optical photon counting in pixel sensors, even at high photon numbers in the same cell. Full article

(This article belongs to the Special Issue Photon-Counting Image Sensors)

► Show Figures

Graphical abstract

22 pages, 1601 KiB

Open AccessArticle

Exponential Arithmetic Based Self-Healing Group Key Distribution Scheme with Backward Secrecy under the Resource-Constrained Wireless Networks

by Hua Guo, Yandong Zheng, Xiyong Zhang and Zhoujun Li

Sensors 2016, 16(5), 609; https://doi.org/10.3390/s16050609 - 28 Apr 2016

Cited by 9 | Viewed by 5479

Abstract

In resource-constrained wireless networks, resources such as storage space and communication bandwidth are limited. To guarantee secure communication in resource-constrained wireless networks, group keys should be distributed to users. The self-healing group key distribution (SGKD) scheme is a promising cryptographic tool, which can [...] Read more.

In resource-constrained wireless networks, resources such as storage space and communication bandwidth are limited. To guarantee secure communication in resource-constrained wireless networks, group keys should be distributed to users. The self-healing group key distribution (SGKD) scheme is a promising cryptographic tool, which can be used to distribute and update the group key for the secure group communication over unreliable wireless networks. Among all known SGKD schemes, exponential arithmetic based SGKD (E-SGKD) schemes reduce the storage overhead to constant, thus is suitable for the the resource-constrained wireless networks. In this paper, we provide a new mechanism to achieve E-SGKD schemes with backward secrecy. We first propose a basic E-SGKD scheme based on a known polynomial-based SGKD, where it has optimal storage overhead while having no backward secrecy. To obtain the backward secrecy and reduce the communication overhead, we introduce a novel approach for message broadcasting and self-healing. Compared with other E-SGKD schemes, our new E-SGKD scheme has the optimal storage overhead, high communication efficiency and satisfactory security. The simulation results in Zigbee-based networks show that the proposed scheme is suitable for the resource-restrained wireless networks. Finally, we show the application of our proposed scheme. Full article

(This article belongs to the Special Issue Security and Privacy in Sensor Networks)

► Show Figures

Figure 1

23 pages, 10706 KiB

Open AccessArticle

Assistant Personal Robot (APR): Conception and Application of a Tele-Operated Assisted Living Robot

by Eduard Clotet, Dani Martínez, Javier Moreno, Marcel Tresanchez and Jordi Palacín

Sensors 2016, 16(5), 610; https://doi.org/10.3390/s16050610 - 28 Apr 2016

Cited by 49 | Viewed by 9946

Abstract

This paper presents the technical description, mechanical design, electronic components, software implementation and possible applications of a tele-operated mobile robot designed as an assisted living tool. This robotic concept has been named Assistant Personal Robot (or APR for short) and has been designed [...] Read more.

This paper presents the technical description, mechanical design, electronic components, software implementation and possible applications of a tele-operated mobile robot designed as an assisted living tool. This robotic concept has been named Assistant Personal Robot (or APR for short) and has been designed as a remotely telecontrolled robotic platform built to provide social and assistive services to elderly people and those with impaired mobility. The APR features a fast high-mobility motion system adapted for tele-operation in plain indoor areas, which incorporates a high-priority collision avoidance procedure. This paper presents the mechanical architecture, electrical fundaments and software implementation required in order to develop the main functionalities of an assistive robot. The APR uses a tablet in order to implement the basic peer-to-peer videoconference and tele-operation control combined with a tactile graphic user interface. The paper also presents the development of some applications proposed in the framework of an assisted living robot. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2015)

► Show Figures

Graphical abstract

15 pages, 1440 KiB

Open AccessArticle

Logarithmic Laplacian Prior Based Bayesian Inverse Synthetic Aperture Radar Imaging

by Shuanghui Zhang, Yongxiang Liu, Xiang Li and Guoan Bi

Sensors 2016, 16(5), 611; https://doi.org/10.3390/s16050611 - 28 Apr 2016

Cited by 5 | Viewed by 5791

Abstract

This paper presents a novel Inverse Synthetic Aperture Radar Imaging (ISAR) algorithm based on a new sparse prior, known as the logarithmic Laplacian prior. The newly proposed logarithmic Laplacian prior has a narrower main lobe with higher tail values than the Laplacian prior, [...] Read more.

This paper presents a novel Inverse Synthetic Aperture Radar Imaging (ISAR) algorithm based on a new sparse prior, known as the logarithmic Laplacian prior. The newly proposed logarithmic Laplacian prior has a narrower main lobe with higher tail values than the Laplacian prior, which helps to achieve performance improvement on sparse representation. The logarithmic Laplacian prior is used for ISAR imaging within the Bayesian framework to achieve better focused radar image. In the proposed method of ISAR imaging, the phase errors are jointly estimated based on the minimum entropy criterion to accomplish autofocusing. The maximum a posterior (MAP) estimation and the maximum likelihood estimation (MLE) are utilized to estimate the model parameters to avoid manually tuning process. Additionally, the fast Fourier Transform (FFT) and Hadamard product are used to minimize the required computational efficiency. Experimental results based on both simulated and measured data validate that the proposed algorithm outperforms the traditional sparse ISAR imaging algorithms in terms of resolution improvement and noise suppression. Full article

(This article belongs to the Special Issue Synthetic Aperture Radars: Models, Algorithms, Techniques and Tools for Data Exploitation)

► Show Figures

Figure 1

15 pages, 6158 KiB

Open AccessArticle

A Flexible Fringe Projection Vision System with Extended Mathematical Model for Accurate Three-Dimensional Measurement

by Suzhi Xiao, Wei Tao and Hui Zhao

Sensors 2016, 16(5), 612; https://doi.org/10.3390/s16050612 - 28 Apr 2016

Cited by 11 | Viewed by 5966

Abstract

In order to acquire an accurate three-dimensional (3D) measurement, the traditional fringe projection technique applies complex and laborious procedures to compensate for the errors that exist in the vision system. However, the error sources in the vision system are very complex, such as [...] Read more.

In order to acquire an accurate three-dimensional (3D) measurement, the traditional fringe projection technique applies complex and laborious procedures to compensate for the errors that exist in the vision system. However, the error sources in the vision system are very complex, such as lens distortion, lens defocus, and fringe pattern nonsinusoidality. Some errors cannot even be explained or rendered with clear expressions and are difficult to compensate directly as a result. In this paper, an approach is proposed that avoids the complex and laborious compensation procedure for error sources but still promises accurate 3D measurement. It is realized by the mathematical model extension technique. The parameters of the extended mathematical model for the ’phase to 3D coordinates transformation’ are derived using the least-squares parameter estimation algorithm. In addition, a phase-coding method based on a frequency analysis is proposed for the absolute phase map retrieval to spatially isolated objects. The results demonstrate the validity and the accuracy of the proposed flexible fringe projection vision system on spatially continuous and discontinuous objects for 3D measurement. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

16 pages, 6810 KiB

Open AccessArticle

Optimal Design of a Center Support Quadruple Mass Gyroscope (CSQMG)

by Tian Zhang, Bin Zhou, Peng Yin, Zhiyong Chen and Rong Zhang

Sensors 2016, 16(5), 613; https://doi.org/10.3390/s16050613 - 28 Apr 2016

Cited by 32 | Viewed by 8850

Abstract

This paper reports a more complete description of the design process of the Center Support Quadruple Mass Gyroscope (CSQMG), a gyro expected to provide breakthrough performance for flat structures. The operation of the CSQMG is based on four lumped masses in a circumferential [...] Read more.

This paper reports a more complete description of the design process of the Center Support Quadruple Mass Gyroscope (CSQMG), a gyro expected to provide breakthrough performance for flat structures. The operation of the CSQMG is based on four lumped masses in a circumferential symmetric distribution, oscillating in anti-phase motion, and providing differential signal extraction. With its 4-fold symmetrical axes pattern, the CSQMG achieves a similar operation mode to Hemispherical Resonant Gyroscopes (HRGs). Compared to the conventional flat design, four Y-shaped coupling beams are used in this new pattern in order to adjust mode distribution and enhance the synchronization mechanism of operation modes. For the purpose of obtaining the optimal design of the CSQMG, a kind of applicative optimization flow is developed with a comprehensive derivation of the operation mode coordination, the pseudo mode inhibition, and the lumped mass twisting motion elimination. The experimental characterization of the CSQMG was performed at room temperature, and the center operation frequency is 6.8 kHz after tuning. Experiments show an Allan variance stability 0.12°/h (@100 s) and a white noise level about 0.72°/h/√Hz, which means that the CSQMG possesses great potential to achieve navigation grade performance. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2016)

► Show Figures

Figure 1

11 pages, 3306 KiB

Open AccessArticle

A New Methodology for 3D Target Detection in Automotive Radar Applications

by Fabio Baselice, Giampaolo Ferraioli, Sergyi Lukin, Gianfranco Matuozzo, Vito Pascazio and Gilda Schirinzi

Sensors 2016, 16(5), 614; https://doi.org/10.3390/s16050614 - 29 Apr 2016

Cited by 6 | Viewed by 5469

Abstract

Today there is a growing interest in automotive sensor monitoring systems. One of the main challenges is to make them an effective and valuable aid in dangerous situations, improving transportation safety. The main limitation of visual aid systems is that they do not [...] Read more.

Today there is a growing interest in automotive sensor monitoring systems. One of the main challenges is to make them an effective and valuable aid in dangerous situations, improving transportation safety. The main limitation of visual aid systems is that they do not produce accurate results in critical visibility conditions, such as in presence of rain, fog or smoke. Radar systems can greatly help in overcoming such limitations. In particular, imaging radar is gaining interest in the framework of Driver Assistance Systems (DAS). In this manuscript, a new methodology able to reconstruct the 3D imaged scene and to detect the presence of multiple targets within each line of sight is proposed. The technique is based on the use of Compressive Sensing (CS) theory and produces the estimation of multiple targets for each line of sight, their range distance and their reflectivities. Moreover, a fast approach for 2D focus based on the FFT algorithm is proposed. After the description of the proposed methodology, different simulated case studies are reported in order to evaluate the performances of the proposed approach. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Graphical abstract

18 pages, 12063 KiB

Open AccessArticle

Self-Sensing Composites: In-Situ Detection of Fibre Fracture

by Shoaib A. Malik, Liwei Wang, Paul T. Curtis and Gerard F. Fernando

Sensors 2016, 16(5), 615; https://doi.org/10.3390/s16050615 - 28 Apr 2016

Cited by 11 | Viewed by 6787

Abstract

The primary load-bearing component in a composite material is the reinforcing fibres. This paper reports on a technique to study the fracture of individual reinforcing fibres or filaments in real-time. Custom-made small-diameter optical fibres with a diameter of 12 (±2) micrometres were used [...] Read more.

The primary load-bearing component in a composite material is the reinforcing fibres. This paper reports on a technique to study the fracture of individual reinforcing fibres or filaments in real-time. Custom-made small-diameter optical fibres with a diameter of 12 (±2) micrometres were used to detect the fracture of individual filaments during tensile loading of unreinforced bundles and composites. The unimpregnated bundles were end-tabbed and tensile tested to failure. A simple technique based on resin-infusion was developed to manufacture composites with a negligible void content. In both cases, optical fibre connectors were attached to the ends of the small-diameter optical fibre bundles to enable light to be coupled into the bundle via one end whilst the opposite end was photographed using a high-speed camera. The feasibility of detecting the fracture of each of the filaments in the bundle and composite was demonstrated. The in-situ damage detection technique was also applied to E-glass bundles and composites; this will be reported in a subsequent publication. Full article

(This article belongs to the Special Issue Integrated Structural Health Monitoring in Polymeric Composites)

► Show Figures

Figure 1

16 pages, 6598 KiB

Open AccessArticle

Guidelines for Designing Surface Ion Traps Using the Boundary Element Method

by Seokjun Hong, Minjae Lee, Hongjin Cheon, Taehyun Kim and Dong-il “Dan” Cho

Sensors 2016, 16(5), 616; https://doi.org/10.3390/s16050616 - 28 Apr 2016

Cited by 24 | Viewed by 9827

Abstract

Ion traps can provide both physical implementation of quantum information processing and direct observation of quantum systems. Recently, surface ion traps have been developed using microfabrication technologies and are considered to be a promising platform for scalable quantum devices. This paper presents detailed [...] Read more.

Ion traps can provide both physical implementation of quantum information processing and direct observation of quantum systems. Recently, surface ion traps have been developed using microfabrication technologies and are considered to be a promising platform for scalable quantum devices. This paper presents detailed guidelines for designing the electrodes of surface ion traps. First, we define and explain the key specifications including trap depth, q-parameter, secular frequency, and ion height. Then, we present a numerical-simulation-based design procedure, which involves determining the basic assumptions, determining the shape and size of the chip, designing the dimensions of the radio frequency (RF) electrode, and analyzing the direct current (DC) control voltages. As an example of this design procedure, we present a case study with tutorial-like explanations. The proposed design procedure can provide a practical guideline for designing the electrodes of surface ion traps. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

31 pages, 7757 KiB

Open AccessArticle

Analysis and Calibration of Sources of Electronic Error in PSD Sensor Response

by David Rodríguez-Navarro, José Luis Lázaro-Galilea, Ignacio Bravo-Muñoz, Alfredo Gardel-Vicente and Georgios Tsirigotis

Sensors 2016, 16(5), 619; https://doi.org/10.3390/s16050619 - 29 Apr 2016

Cited by 31 | Viewed by 7498

Abstract

In order to obtain very precise measurements of the position of agents located at a considerable distance using a sensor system based on position sensitive detectors (PSD), it is necessary to analyze and mitigate the factors that generate substantial errors in the system’s [...] Read more.

In order to obtain very precise measurements of the position of agents located at a considerable distance using a sensor system based on position sensitive detectors (PSD), it is necessary to analyze and mitigate the factors that generate substantial errors in the system’s response. These sources of error can be divided into electronic and geometric factors. The former stem from the nature and construction of the PSD as well as the performance, tolerances and electronic response of the system, while the latter are related to the sensor’s optical system. Here, we focus solely on the electrical effects, since the study, analysis and correction of these are a prerequisite for subsequently addressing geometric errors. A simple calibration method is proposed, which considers PSD response, component tolerances, temperature variations, signal frequency used, signal to noise ratio (SNR), suboptimal operational amplifier parameters, and analog to digital converter (ADC) quantitation SNR_Q, etc. Following an analysis of these effects and calibration of the sensor, it was possible to correct the errors, thus rendering the effects negligible, as reported in the results section. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

10 pages, 2564 KiB

Open AccessArticle

A Magnetic Field Sensor Based on a Magnetic Fluid-Filled FP-FBG Structure

by Ji Xia, Fuyin Wang, Hong Luo, Qi Wang and Shuidong Xiong

Sensors 2016, 16(5), 620; https://doi.org/10.3390/s16050620 - 29 Apr 2016

Cited by 91 | Viewed by 9131

Abstract

Based on the characteristic magnetic-controlled refractive index property, in this paper, a magnetic fluid is used as a sensitive medium to detect the magnetic field in the fiber optic Fabry-Perot (FP) cavity. The temperature compensation in fiber Fabry-Perot magnetic sensor is demonstrated and [...] Read more.

Based on the characteristic magnetic-controlled refractive index property, in this paper, a magnetic fluid is used as a sensitive medium to detect the magnetic field in the fiber optic Fabry-Perot (FP) cavity. The temperature compensation in fiber Fabry-Perot magnetic sensor is demonstrated and achieved. The refractive index of the magnetic fluid varies with the applied magnetic field and external temperature, and a cross-sensitivity effect of the temperature and magnetic field occurs in the Fabry-Perot magnetic sensor and the accuracy of magnetic field measurements is affected by the thermal effect. In order to overcome this problem, we propose a modified sensor structure. With a fiber Bragg grating (FBG) written in the insert fiber end of the Fabry-Perot cavity, the FBG acts as a temperature compensation unit for the magnetic field measurement and it provides an effective solution to the cross-sensitivity effect. The experimental results show that the sensitivity of magnetic field detection improves from 0.23 nm/mT to 0.53 nm/mT, and the magnetic field measurement resolution finally reaches 37.7 T. The temperature-compensated FP-FBG magnetic sensor has obvious advantages of small volume and high sensitivity, and it has a good prospect in applications in the power industry and national defense technology areas. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Graphical abstract

17 pages, 3919 KiB

Open AccessArticle

An Improved Alignment Method for the Strapdown Inertial Navigation System (SINS)

by Meng Liu, Yanbin Gao, Guangchun Li, Xingxing Guang and Shutong Li

Sensors 2016, 16(5), 621; https://doi.org/10.3390/s16050621 - 29 Apr 2016

Cited by 40 | Viewed by 8368

Abstract

In this paper, an innovative inertial navigation system (INS) mechanization and the associated Kalman filter (KF) are developed to implement a fine alignment for the strapdown INS (SINS) on stationary base. The improved mechanization is established in the pseudo-geographic frame, which is rebuilt [...] Read more.

In this paper, an innovative inertial navigation system (INS) mechanization and the associated Kalman filter (KF) are developed to implement a fine alignment for the strapdown INS (SINS) on stationary base. The improved mechanization is established in the pseudo-geographic frame, which is rebuilt based on the initial position. The new mechanization eliminates the effects of linear movement errors on the heading by decoupling. Compared with the traditional local-level mechanization, it has more advantages. The proposed algorithm requires lower coarse alignment accuracy in both the open-loop and closed-loop KFs and hence can improve the system reliability and decrease the total alignment time. Moreover, for the closed-loop KF, it can decrease oscillation caused by the system errors and improve the closed-loop system stability. In addition, the proposed algorithm can also be applied to polar alignment. The performance of the proposed algorithm is verified by both simulations and experiments and the results exhibit the superior performance of the proposed approach. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2016)

► Show Figures

Figure 1

22 pages, 3548 KiB

Open AccessArticle

A Small Acoustic Goniometer for General Purpose Research

by Michael L. Pook and Sin Ming Loo

Sensors 2016, 16(5), 622; https://doi.org/10.3390/s16050622 - 29 Apr 2016

Viewed by 4856

Abstract

Understanding acoustic events and monitoring their occurrence is a useful aspect of many research projects. In particular, acoustic goniometry allows researchers to determine the source of an event based solely on the sound it produces. The vast majority of acoustic goniometry research projects [...] Read more.

Understanding acoustic events and monitoring their occurrence is a useful aspect of many research projects. In particular, acoustic goniometry allows researchers to determine the source of an event based solely on the sound it produces. The vast majority of acoustic goniometry research projects used custom hardware targeted to the specific application under test. Unfortunately, due to the wide range of sensing applications, a flexible general purpose hardware/firmware system does not exist for this purpose. This article focuses on the development of such a system which encourages the continued exploration of general purpose hardware/firmware and lowers barriers to research in projects requiring the use of acoustic goniometry. Simulations have been employed to verify system feasibility, and a complete hardware implementation of the acoustic goniometer has been designed and field tested. The results are reported, and suggested areas for improvement and further exploration are discussed. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

17 pages, 480 KiB

Open AccessArticle

Effective Sensor Selection and Data Anomaly Detection for Condition Monitoring of Aircraft Engines

by Liansheng Liu, Datong Liu, Yujie Zhang and Yu Peng

Sensors 2016, 16(5), 623; https://doi.org/10.3390/s16050623 - 29 Apr 2016

Cited by 36 | Viewed by 8191

Abstract

In a complex system, condition monitoring (CM) can collect the system working status. The condition is mainly sensed by the pre-deployed sensors in/on the system. Most existing works study how to utilize the condition information to predict the upcoming anomalies, faults, or failures. [...] Read more.

In a complex system, condition monitoring (CM) can collect the system working status. The condition is mainly sensed by the pre-deployed sensors in/on the system. Most existing works study how to utilize the condition information to predict the upcoming anomalies, faults, or failures. There is also some research which focuses on the faults or anomalies of the sensing element (i.e., sensor) to enhance the system reliability. However, existing approaches ignore the correlation between sensor selecting strategy and data anomaly detection, which can also improve the system reliability. To address this issue, we study a new scheme which includes sensor selection strategy and data anomaly detection by utilizing information theory and Gaussian Process Regression (GPR). The sensors that are more appropriate for the system CM are first selected. Then, mutual information is utilized to weight the correlation among different sensors. The anomaly detection is carried out by using the correlation of sensor data. The sensor data sets that are utilized to carry out the evaluation are provided by National Aeronautics and Space Administration (NASA) Ames Research Center and have been used as Prognostics and Health Management (PHM) challenge data in 2008. By comparing the two different sensor selection strategies, the effectiveness of selection method on data anomaly detection is proved. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Graphical abstract

26 pages, 3157 KiB

Open AccessArticle

Implementation Strategies for a Universal Acquisition and Tracking Channel Applied to Real GNSS Signals

by Marc-Antoine Fortin and René Landry, Jr.

Sensors 2016, 16(5), 624; https://doi.org/10.3390/s16050624 - 2 May 2016

Cited by 6 | Viewed by 7229

Abstract

This paper presents a universal GNSS receiver channel capable of tracking any civil GNSS signal. This fundamentally differs from dedicated channels, each customized for a given signal. A mobile device could integrate fewer universal channels to harvest all available signals. This would allow [...] Read more.

This paper presents a universal GNSS receiver channel capable of tracking any civil GNSS signal. This fundamentally differs from dedicated channels, each customized for a given signal. A mobile device could integrate fewer universal channels to harvest all available signals. This would allow securing signal availability, while minimizing power consumption and chip size, thus maximizing battery lifetime. In fact, the universal channel allows sequential acquisition and tracking of any chipping rate, carrier frequency, FDMA channel, modulation, or constellation, and is totally configurable (any integration time, any discriminator, etc.). It can switch from one signal to another in 1.07 ms, making it possible for the receiver to rapidly adapt to its sensed environment. All this would consume 3.5 mW/channel in an ASIC implementation, i.e., with a slight overhead compared to the original GPS L1 C/A dedicated channel from which it was derived. After extensive surveys on GNSS signals and tracking channels, this paper details the implementation strategies that led to the proposed universal channel architecture. Validation is achieved using GNSS signals issued from different constellations, frequency bands, modulations and spreading code schemes. A discussion on acquisition approaches and conclusive remarks follow, which open up a new signal selection challenge, rather than satellite selection. Full article

(This article belongs to the Special Issue Advances on Resources Management for Multi-Platform Infrastructures)

► Show Figures

Figure 1

9 pages, 1265 KiB

Open AccessArticle

In Situ Representation of Soil/Sediment Conductivity Using Electrochemical Impedance Spectroscopy

by Xiaojing Li, Xin Wang, Qian Zhao, Yueyong Zhang and Qixing Zhou

Sensors 2016, 16(5), 625; https://doi.org/10.3390/s16050625 - 30 Apr 2016

Cited by 34 | Viewed by 10001

Abstract

The electrical conductivity (EC) of soil is generally measured after soil extraction, so this method cannot represent the in situ EC of soil (e.g., EC of soils with different moisture contents) and therefore lacks comparability in some cases. Using a resistance measurement apparatus [...] Read more.

The electrical conductivity (EC) of soil is generally measured after soil extraction, so this method cannot represent the in situ EC of soil (e.g., EC of soils with different moisture contents) and therefore lacks comparability in some cases. Using a resistance measurement apparatus converted from a configuration of soil microbial fuel cell, the in situ soil EC was evaluated according to the Ohmic resistance (R_s) measured using electrochemical impedance spectroscopy. The EC of soils with moisture content from 9.1% to 37.5% was calculated according to R_s. A significant positive correlation (R² = 0.896, p < 0.01) between the soil EC and the moisture content was observed, which demonstrated the feasibility of the approach. This new method can not only represent the actual soil EC, but also does not need any pretreatment. Thus it may be used widely in the measurement of the EC for soils and sediments. Full article

(This article belongs to the Special Issue Sensors for Environmental Monitoring 2016)

► Show Figures

Graphical abstract

10 pages, 2101 KiB

Open AccessArticle

A Rapid In Situ Colorimetric Assay for Cobalt Detection by the Naked Eye

by Sung-Min Kang, Sung-Chan Jang, Gi Yong Kim, Chang-Soo Lee, Yun Suk Huh and Changhyun Roh

Sensors 2016, 16(5), 626; https://doi.org/10.3390/s16050626 - 2 May 2016

Cited by 22 | Viewed by 11480

Abstract

A simple, rapid, and convenient colorimetric chemosensor of a specific target toward the end user is still required for on-site detection and real-time monitoring applications. In this study, we developed a rapid in situ colorimetric assay for cobalt detection using the naked eye. [...] Read more.

A simple, rapid, and convenient colorimetric chemosensor of a specific target toward the end user is still required for on-site detection and real-time monitoring applications. In this study, we developed a rapid in situ colorimetric assay for cobalt detection using the naked eye. Interestingly, a yellow to light orange visual color transition was observed within 3 s when a Chrysoidine G (CG) chemosensor was exposed to cobalt. Surprisingly, the CG chemosensor had great selectivity toward cobalt without any interference of other metal ions. Under optimized conditions, a lower detection limit of 0.1 ppm via a spectrophotometer and a visual detection limit of 2 ppm with a linear range from 0.4 to 1 ppm (R² = 0.97) were determined. Moreover, the CG chemosensor is reversible and maintains its functionality after treatment with chelating agents. In conclusion, we show the superior capabilities of the CG chemosensor, which has the potential to provide extremely facile handling, high sensitivity, and a fast response time for applications of on-site detection to real-time cobalt monitoring for the general public. Full article

(This article belongs to the Special Issue Colorimetric and Fluorescent Sensor)

► Show Figures

Figure 1

22 pages, 10686 KiB

Open AccessArticle

Tracking Architecture Based on Dual-Filter with State Feedback and Its Application in Ultra-Tight GPS/INS Integration

by Xi Zhang, Lingjuan Miao and Haijun Shao

Sensors 2016, 16(5), 627; https://doi.org/10.3390/s16050627 - 2 May 2016

Cited by 11 | Viewed by 4779

Abstract

If a Kalman Filter (KF) is applied to Global Positioning System (GPS) baseband signal preprocessing, the estimates of signal phase and frequency can have low variance, even in highly dynamic situations. This paper presents a novel preprocessing scheme based on a dual-filter structure. [...] Read more.

If a Kalman Filter (KF) is applied to Global Positioning System (GPS) baseband signal preprocessing, the estimates of signal phase and frequency can have low variance, even in highly dynamic situations. This paper presents a novel preprocessing scheme based on a dual-filter structure. Compared with the traditional model utilizing a single KF, this structure avoids carrier tracking being subjected to code tracking errors. Meanwhile, as the loop filters are completely removed, state feedback values are adopted to generate local carrier and code. Although local carrier frequency has a wide fluctuation, the accuracy of Doppler shift estimation is improved. In the ultra-tight GPS/Inertial Navigation System (INS) integration, the carrier frequency derived from the external navigation information is not viewed as the local carrier frequency directly. That facilitates retaining the design principle of state feedback. However, under harsh conditions, the GPS outputs may still bear large errors which can destroy the estimation of INS errors. Thus, an innovative integrated navigation filter is constructed by modeling the non-negligible errors in the estimated Doppler shifts, to ensure INS is properly calibrated. Finally, field test and semi-physical simulation based on telemetered missile trajectory validate the effectiveness of methods proposed in this paper. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

10 pages, 3799 KiB

Open AccessArticle

Multi-Mode Electromagnetic Ultrasonic Lamb Wave Tomography Imaging for Variable-Depth Defects in Metal Plates

by Songling Huang, Yu Zhang, Shen Wang and Wei Zhao

Sensors 2016, 16(5), 628; https://doi.org/10.3390/s16050628 - 2 May 2016

Cited by 19 | Viewed by 5755

Abstract

This paper proposes a new cross-hole tomography imaging (CTI) method for variable-depth defects in metal plates based on multi-mode electromagnetic ultrasonic Lamb waves (LWs). The dispersion characteristics determine that different modes of LWs are sensitive to different thicknesses of metal plates. In this [...] Read more.

This paper proposes a new cross-hole tomography imaging (CTI) method for variable-depth defects in metal plates based on multi-mode electromagnetic ultrasonic Lamb waves (LWs). The dispersion characteristics determine that different modes of LWs are sensitive to different thicknesses of metal plates. In this work, the sensitivities to thickness variation of A0- and S0-mode LWs are theoretically studied. The principles and procedures for the cooperation of A0- and S0-mode LW CTI are proposed. Moreover, the experimental LW imaging system on an aluminum plate with a variable-depth defect is set up, based on A0- and S0-mode EMAT (electromagnetic acoustic transducer) arrays. For comparison, the traditional single-mode LW CTI method is used in the same experimental platform. The imaging results show that the computed thickness distribution by the proposed multi-mode method more accurately reflects the actual thickness variation of the defect, while neither the S0 nor the A0 single-mode method was able to distinguish thickness variation in the defect region. Moreover, the quantification of the defect’s thickness variation is more accurate with the multi-mode method. Therefore, theoretical and practical results prove that the variable-depth defect in metal plates can be successfully quantified and visualized by the proposed multi-mode electromagnetic ultrasonic LW CTI method. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

11 pages, 1937 KiB

Open AccessArticle

Feedback Robust Cubature Kalman Filter for Target Tracking Using an Angle Sensor

by Hao Wu, Shuxin Chen, Binfeng Yang and Kun Chen

Sensors 2016, 16(5), 629; https://doi.org/10.3390/s16050629 - 9 May 2016

Cited by 12 | Viewed by 5598

Abstract

The direction of arrival (DOA) tracking problem based on an angle sensor is an important topic in many fields. In this paper, a nonlinear filter named the feedback M-estimation based robust cubature Kalman filter (FMR-CKF) is proposed to deal with measurement outliers from [...] Read more.

The direction of arrival (DOA) tracking problem based on an angle sensor is an important topic in many fields. In this paper, a nonlinear filter named the feedback M-estimation based robust cubature Kalman filter (FMR-CKF) is proposed to deal with measurement outliers from the angle sensor. The filter designs a new equivalent weight function with the Mahalanobis distance to combine the cubature Kalman filter (CKF) with the M-estimation method. Moreover, by embedding a feedback strategy which consists of a splitting and merging procedure, the proper sub-filter (the standard CKF or the robust CKF) can be chosen in each time index. Hence, the probability of the outliers’ misjudgment can be reduced. Numerical experiments show that the FMR-CKF performs better than the CKF and conventional robust filters in terms of accuracy and robustness with good computational efficiency. Additionally, the filter can be extended to the nonlinear applications using other types of sensors. Full article

► Show Figures

Figure 1

10 pages, 2370 KiB

Open AccessArticle

Nitrogen-Doped Carbon Dots as A New Substrate for Sensitive Glucose Determination

by Hanxu Ji, Feng Zhou, Jiangjiang Gu, Chen Shu, Kai Xi and Xudong Jia

Sensors 2016, 16(5), 630; https://doi.org/10.3390/s16050630 - 4 May 2016

Cited by 57 | Viewed by 10073

Abstract

Nitrogen-doped carbon dots are introduced as a novel substrate suitable for enzyme immobilization in electrochemical detection metods. Nitrogen-doped carbon dots are easily synthesised from polyacrylamide in just one step. With the help of the amino group on chitosan, glucose oxidase is immobilized on [...] Read more.

Nitrogen-doped carbon dots are introduced as a novel substrate suitable for enzyme immobilization in electrochemical detection metods. Nitrogen-doped carbon dots are easily synthesised from polyacrylamide in just one step. With the help of the amino group on chitosan, glucose oxidase is immobilized on nitrogen-doped carbon dots-modified carbon glassy electrodes by amino-carboxyl reactions. The nitrogen-induced charge delocalization at nitrogen-doped carbon dots can enhance the electrocatalytic activity toward the reduction of O₂. The specific amino-carboxyl reaction provides strong and stable immobilization of GO_x on electrodes. The developed biosensor responds efficiently to the presence of glucose in serum samples over the concentration range from 1 to 12 mM with a detection limit of 0.25 mM. This novel biosensor has good reproducibility and stability, and is highly selective for glucose determination under physiological conditions. These results indicate that N-doped quantum dots represent a novel candidate material for the construction of electrochemical biosensors. Full article

(This article belongs to the Special Issue Glucose Sensors: Revolution in Diabetes Management 2016)

► Show Figures

Graphical abstract

11 pages, 4594 KiB

Open AccessArticle

Automatic Recognition of Aggressive Behavior in Pigs Using a Kinect Depth Sensor

by Jonguk Lee, Long Jin, Daihee Park and Yongwha Chung

Sensors 2016, 16(5), 631; https://doi.org/10.3390/s16050631 - 2 May 2016

Cited by 149 | Viewed by 13017

Abstract

Aggression among pigs adversely affects economic returns and animal welfare in intensive pigsties. In this study, we developed a non-invasive, inexpensive, automatic monitoring prototype system that uses a Kinect depth sensor to recognize aggressive behavior in a commercial pigpen. The method begins by [...] Read more.

Aggression among pigs adversely affects economic returns and animal welfare in intensive pigsties. In this study, we developed a non-invasive, inexpensive, automatic monitoring prototype system that uses a Kinect depth sensor to recognize aggressive behavior in a commercial pigpen. The method begins by extracting activity features from the Kinect depth information obtained in a pigsty. The detection and classification module, which employs two binary-classifier support vector machines in a hierarchical manner, detects aggressive activity, and classifies it into aggressive sub-types such as head-to-head (or body) knocking and chasing. Our experimental results showed that this method is effective for detecting aggressive pig behaviors in terms of both cost-effectiveness (using a low-cost Kinect depth sensor) and accuracy (detection and classification accuracies over 95.7% and 90.2%, respectively), either as a standalone solution or to complement existing methods. Full article

(This article belongs to the Special Issue Sensors for Agriculture)

► Show Figures

Figure 1

20 pages, 7865 KiB

Open AccessArticle

Quantitative Index and Abnormal Alarm Strategy Using Sensor-Dependent Vibration Data for Blade Crack Identification in Centrifugal Booster Fans

by Jinglong Chen, Hailiang Sun, Shuai Wang and Zhengjia He

Sensors 2016, 16(5), 632; https://doi.org/10.3390/s16050632 - 9 May 2016

Cited by 6 | Viewed by 5310

Abstract

Centrifugal booster fans are important equipment used to recover blast furnace gas (BFG) for generating electricity, but blade crack faults (BCFs) in centrifugal booster fans can lead to unscheduled breakdowns and potentially serious accidents, so in this work quantitative fault identification and an [...] Read more.

Centrifugal booster fans are important equipment used to recover blast furnace gas (BFG) for generating electricity, but blade crack faults (BCFs) in centrifugal booster fans can lead to unscheduled breakdowns and potentially serious accidents, so in this work quantitative fault identification and an abnormal alarm strategy based on acquired historical sensor-dependent vibration data is proposed for implementing condition-based maintenance for this type of equipment. Firstly, three group dependent sensors are installed to acquire running condition data. Then a discrete spectrum interpolation method and short time Fourier transform (STFT) are applied to preliminarily identify the running data in the sensor-dependent vibration data. As a result a quantitative identification and abnormal alarm strategy based on compound indexes including the largest Lyapunov exponent and relative energy ratio at the second harmonic frequency component is proposed. Then for validation the proposed blade crack quantitative identification and abnormality alarm strategy is applied to analyze acquired experimental data for centrifugal booster fans and it has successfully identified incipient blade crack faults. In addition, the related mathematical modelling work is also introduced to investigate the effects of mistuning and cracks on the vibration features of centrifugal impellers and to explore effective techniques for crack detection. Full article

► Show Figures

Figure 1

8 pages, 9094 KiB

Open AccessArticle

Interferometric Sensor of Wavelength Detuning Using a Liquid Crystalline Polymer Waveplate

by Paweł Wierzba

Sensors 2016, 16(5), 633; https://doi.org/10.3390/s16050633 - 9 May 2016

Cited by 3 | Viewed by 4858

Abstract

Operation of a polarization interferometer for measurement of the wavelength changes of a tunable semiconductor laser was investigated. A λ/8 waveplate made from liquid crystalline polymer is placed in one of interferometers’ arms in order to generate two output signals in quadrature. [...] Read more.

Operation of a polarization interferometer for measurement of the wavelength changes of a tunable semiconductor laser was investigated. A λ/8 waveplate made from liquid crystalline polymer is placed in one of interferometers’ arms in order to generate two output signals in quadrature. Wavelength was measured with resolution of 2 pm in the wavelength range 628–635 nm. Drift of the interferometer, measured in the period of 500 s, was 8 nm, which corresponded to the change in the wavelength of 1.3 pm. If needed, wavelength-dependent Heydemann correction can be used to expand the range of operation of such interferometer. Full article

(This article belongs to the Special Issue Infrared and THz Sensing and Imaging)

► Show Figures

Figure 1

13 pages, 6449 KiB

Open AccessArticle

Large Out-of-Plane Displacement Bistable Electromagnetic Microswitch on a Single Wafer

by Xiaodan Miao, Xuhan Dai, Yi Huang, Guifu Ding and Xiaolin Zhao

Sensors 2016, 16(5), 634; https://doi.org/10.3390/s16050634 - 5 May 2016

Cited by 8 | Viewed by 6315

Abstract

This paper presents a bistable microswitch fully batch-fabricated on a single glass wafer, comprising of a microactuator, a signal transformer, a microspring and a permanent magnet. The bistable mechanism of the microswitch with large displacement of 160 μm depends on the balance of [...] Read more.

This paper presents a bistable microswitch fully batch-fabricated on a single glass wafer, comprising of a microactuator, a signal transformer, a microspring and a permanent magnet. The bistable mechanism of the microswitch with large displacement of 160 μm depends on the balance of the magnetic force and elastic force. Both the magnetic force and elastic force were optimized by finite-element simulation to predict the reliable of the device. The prototype was fabricated and characterized. By utilizing thick laminated photoresist sacrificial layer, the large displacement was obtained to ensure the insulation of the microswitch. The testing results show that the microswitch realized the bistable mechanism at a 3–5 V input voltage and closed in 0.96 ms, which verified the simulation. Full article

(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering)

► Show Figures

Figure 1

15 pages, 1046 KiB

Open AccessArticle

BDS/GPS Dual Systems Positioning Based on the Modified SR-UKF Algorithm

by JaeHyok Kong, Xuchu Mao and Shaoyuan Li

Sensors 2016, 16(5), 635; https://doi.org/10.3390/s16050635 - 3 May 2016

Cited by 15 | Viewed by 5285

Abstract

The Global Navigation Satellite System can provide all-day three-dimensional position and speed information. Currently, only using the single navigation system cannot satisfy the requirements of the system’s reliability and integrity. In order to improve the reliability and stability of the satellite navigation system, [...] Read more.

The Global Navigation Satellite System can provide all-day three-dimensional position and speed information. Currently, only using the single navigation system cannot satisfy the requirements of the system’s reliability and integrity. In order to improve the reliability and stability of the satellite navigation system, the positioning method by BDS and GPS navigation system is presented, the measurement model and the state model are described. Furthermore, the modified square-root Unscented Kalman Filter (SR-UKF) algorithm is employed in BDS and GPS conditions, and analysis of single system/multi-system positioning has been carried out, respectively. The experimental results are compared with the traditional estimation results, which show that the proposed method can perform highly-precise positioning. Especially when the number of satellites is not adequate enough, the proposed method combine BDS and GPS systems to achieve a higher positioning precision. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

15 pages, 1553 KiB

Open AccessArticle

Performance Comparison of Fuzzy ARTMAP and LDA in Qualitative Classification of Iranian Rosa damascena Essential Oils by an Electronic Nose

by Abbas Gorji-Chakespari, Ali Mohammad Nikbakht, Fatemeh Sefidkon, Mahdi Ghasemi-Varnamkhasti, Jesús Brezmes and Eduard Llobet

Sensors 2016, 16(5), 636; https://doi.org/10.3390/s16050636 - 4 May 2016

Cited by 23 | Viewed by 7359

Abstract

Quality control of essential oils is an important topic in industrial processing of medicinal and aromatic plants. In this paper, the performance of Fuzzy Adaptive Resonant Theory Map (ARTMAP) and linear discriminant analysis (LDA) algorithms are compared in the specific task of quality [...] Read more.

Quality control of essential oils is an important topic in industrial processing of medicinal and aromatic plants. In this paper, the performance of Fuzzy Adaptive Resonant Theory Map (ARTMAP) and linear discriminant analysis (LDA) algorithms are compared in the specific task of quality classification of Rosa damascene essential oil samples (one of the most famous and valuable essential oils in the world) using an electronic nose (EN) system based on seven metal oxide semiconductor (MOS) sensors. First, with the aid of a GC-MS analysis, samples of Rosa damascene essential oils were classified into three different categories (low, middle, and high quality, classes C1, C2, and C3, respectively) based on the total percent of the most crucial qualitative compounds. An ad-hoc electronic nose (EN) system was implemented to sense the samples and acquire signals. Forty-nine features were extracted from the EN sensor matrix (seven parameters to describe each sensor curve response). The extracted features were ordered in relevance by the intra/inter variance criterion (Vr), also known as the Fisher discriminant. A leave-one-out cross validation technique was implemented for estimating the classification accuracy reached by both algorithms. Success rates were calculated using 10, 20, 30, and the entire selected features from the response of the sensor array. The results revealed a maximum classification accuracy of 99% when applying the Fuzzy ARTMAP algorithm and 82% for LDA, using the first 10 features in both cases. Further classification results explained that sub-optimal performance is likely to occur when all the response features are applied. It was found that an electronic nose system employing a Fuzzy ARTMAP classifier could become an accurate, easy, and inexpensive alternative tool for qualitative control in the production of Rosa damascene essential oil. Full article

(This article belongs to the Special Issue E-noses: Sensors and Applications)

► Show Figures

Figure 1

24 pages, 10850 KiB

Open AccessArticle

Performance Analysis of ICA in Sensor Array

by Xin Cai, Xiang Wang, Zhitao Huang and Fenghua Wang

Sensors 2016, 16(5), 637; https://doi.org/10.3390/s16050637 - 5 May 2016

Cited by 20 | Viewed by 5317

Abstract

As the best-known scheme in the field of Blind Source Separation (BSS), Independent Component Analysis (ICA) has been intensively used in various domains, including biomedical and acoustics applications, cooperative or non-cooperative communication, etc. While sensor arrays are involved in most of the applications, [...] Read more.

As the best-known scheme in the field of Blind Source Separation (BSS), Independent Component Analysis (ICA) has been intensively used in various domains, including biomedical and acoustics applications, cooperative or non-cooperative communication, etc. While sensor arrays are involved in most of the applications, the influence on the performance of ICA of practical factors therein has not been sufficiently investigated yet. In this manuscript, the issue is researched by taking the typical antenna array as an illustrative example. Factors taken into consideration include the environment noise level, the properties of the array and that of the radiators. We analyze the analytic relationship between the noise variance, the source variance, the condition number of the mixing matrix and the optimal signal to interference-plus-noise ratio, as well as the relationship between the singularity of the mixing matrix and practical factors concerned. The situations where the mixing process turns (nearly) singular have been paid special attention to, since such circumstances are critical in applications. Results and conclusions obtained should be instructive when applying ICA algorithms on mixtures from sensor arrays. Moreover, an effective countermeasure against the cases of singular mixtures has been proposed, on the basis of previous analysis. Experiments validating the theoretical conclusions as well as the effectiveness of the proposed scheme have been included. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Graphical abstract

20 pages, 5608 KiB

Open AccessArticle

Rapid Multi-Damage Identification for Health Monitoring of Laminated Composites Using Piezoelectric Wafer Sensor Arrays

by Liang Si and Qian Wang

Sensors 2016, 16(5), 638; https://doi.org/10.3390/s16050638 - 4 May 2016

Cited by 13 | Viewed by 5209

Abstract

Through the use of the wave reflection from any damage in a structure, a Hilbert spectral analysis-based rapid multi-damage identification (HSA-RMDI) technique with piezoelectric wafer sensor arrays (PWSA) is developed to monitor and identify the presence, location and severity of damage in carbon [...] Read more.

Through the use of the wave reflection from any damage in a structure, a Hilbert spectral analysis-based rapid multi-damage identification (HSA-RMDI) technique with piezoelectric wafer sensor arrays (PWSA) is developed to monitor and identify the presence, location and severity of damage in carbon fiber composite structures. The capability of the rapid multi-damage identification technique to extract and estimate hidden significant information from the collected data and to provide a high-resolution energy-time spectrum can be employed to successfully interpret the Lamb waves interactions with single/multiple damage. Nevertheless, to accomplish the precise positioning and effective quantification of multiple damage in a composite structure, two functional metrics from the RMDI technique are proposed and used in damage identification, which are the energy density metric and the energy time-phase shift metric. In the designed damage experimental tests, invisible damage to the naked eyes, especially delaminations, were detected in the leftward propagating waves as well as in the selected sensor responses, where the time-phase shift spectra could locate the multiple damage whereas the energy density spectra were used to quantify the multiple damage. The increasing damage was shown to follow a linear trend calculated by the RMDI technique. All damage cases considered showed completely the developed RMDI technique potential as an effective online damage inspection and assessment tool. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

25 pages, 11655 KiB

Open AccessArticle

Damage Detection Based on Power Dissipation Measured with PZT Sensors through the Combination of Electro-Mechanical Impedances and Guided Waves

by Enrique Sevillano, Rui Sun and Ricardo Perera

Sensors 2016, 16(5), 639; https://doi.org/10.3390/s16050639 - 5 May 2016

Cited by 42 | Viewed by 6946

Abstract

The use of piezoelectric ceramic transducers (such as Lead-Zirconate-Titanate—PZT) has become more and more widespread for Structural Health Monitoring (SHM) applications. Among all the techniques that are based on this smart sensing solution, guided waves and electro-mechanical impedance techniques have found wider acceptance, [...] Read more.

The use of piezoelectric ceramic transducers (such as Lead-Zirconate-Titanate—PZT) has become more and more widespread for Structural Health Monitoring (SHM) applications. Among all the techniques that are based on this smart sensing solution, guided waves and electro-mechanical impedance techniques have found wider acceptance, and so more studies and experimental works can be found containing these applications. However, even though these two techniques can be considered as complementary to each other, little work can be found focused on the combination of them in order to define a new and integrated damage detection procedure. In this work, this combination of techniques has been studied by proposing a new integrated damage indicator based on Electro-Mechanical Power Dissipation (EMPD). The applicability of this proposed technique has been tested through different experimental tests, with both lab-scale and real-scale structures. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2015)

► Show Figures

Graphical abstract

25 pages, 8415 KiB

Open AccessArticle

3D Visual Data-Driven Spatiotemporal Deformations for Non-Rigid Object Grasping Using Robot Hands

by Carlos M. Mateo, Pablo Gil and Fernando Torres

Sensors 2016, 16(5), 640; https://doi.org/10.3390/s16050640 - 5 May 2016

Cited by 10 | Viewed by 6196

Abstract

Sensing techniques are important for solving problems of uncertainty inherent to intelligent grasping tasks. The main goal here is to present a visual sensing system based on range imaging technology for robot manipulation of non-rigid objects. Our proposal provides a suitable visual perception [...] Read more.

Sensing techniques are important for solving problems of uncertainty inherent to intelligent grasping tasks. The main goal here is to present a visual sensing system based on range imaging technology for robot manipulation of non-rigid objects. Our proposal provides a suitable visual perception system of complex grasping tasks to support a robot controller when other sensor systems, such as tactile and force, are not able to obtain useful data relevant to the grasping manipulation task. In particular, a new visual approach based on RGBD data was implemented to help a robot controller carry out intelligent manipulation tasks with flexible objects. The proposed method supervises the interaction between the grasped object and the robot hand in order to avoid poor contact between the fingertips and an object when there is neither force nor pressure data. This new approach is also used to measure changes to the shape of an object’s surfaces and so allows us to find deformations caused by inappropriate pressure being applied by the hand’s fingers. Test was carried out for grasping tasks involving several flexible household objects with a multi-fingered robot hand working in real time. Our approach generates pulses from the deformation detection method and sends an event message to the robot controller when surface deformation is detected. In comparison with other methods, the obtained results reveal that our visual pipeline does not use deformations models of objects and materials, as well as the approach works well both planar and 3D household objects in real time. In addition, our method does not depend on the pose of the robot hand because the location of the reference system is computed from a recognition process of a pattern located place at the robot forearm. The presented experiments demonstrate that the proposed method accomplishes a good monitoring of grasping task with several objects and different grasping configurations in indoor environments. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2015)

► Show Figures

Graphical abstract

16 pages, 11423 KiB

Open AccessArticle

Machine Learning and Computer Vision System for Phenotype Data Acquisition and Analysis in Plants

by Pedro J. Navarro, Fernando Pérez, Julia Weiss and Marcos Egea-Cortines

Sensors 2016, 16(5), 641; https://doi.org/10.3390/s16050641 - 5 May 2016

Cited by 39 | Viewed by 8826

Abstract

Phenomics is a technology-driven approach with promising future to obtain unbiased data of biological systems. Image acquisition is relatively simple. However data handling and analysis are not as developed compared to the sampling capacities. We present a system based on machine learning (ML) [...] Read more.

Phenomics is a technology-driven approach with promising future to obtain unbiased data of biological systems. Image acquisition is relatively simple. However data handling and analysis are not as developed compared to the sampling capacities. We present a system based on machine learning (ML) algorithms and computer vision intended to solve the automatic phenotype data analysis in plant material. We developed a growth-chamber able to accommodate species of various sizes. Night image acquisition requires near infrared lightning. For the ML process, we tested three different algorithms: k-nearest neighbour (kNN), Naive Bayes Classifier (NBC), and Support Vector Machine. Each ML algorithm was executed with different kernel functions and they were trained with raw data and two types of data normalisation. Different metrics were computed to determine the optimal configuration of the machine learning algorithms. We obtained a performance of 99.31% in kNN for RGB images and a 99.34% in SVM for NIR. Our results show that ML techniques can speed up phenomic data analysis. Furthermore, both RGB and NIR images can be segmented successfully but may require different ML algorithms for segmentation. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2015)

► Show Figures

Figure 1

10 pages, 3755 KiB

Open AccessArticle

Fano Resonance Based on Metal-Insulator-Metal Waveguide-Coupled Double Rectangular Cavities for Plasmonic Nanosensors

by Zhidong Zhang, Liang Luo, Chenyang Xue, Wendong Zhang and Shubin Yan

Sensors 2016, 16(5), 642; https://doi.org/10.3390/s16050642 - 5 May 2016

Cited by 151 | Viewed by 8145

Abstract

A refractive index sensor based on metal-insulator-metal (MIM) waveguides coupled double rectangular cavities is proposed and investigated numerically using the finite element method (FEM). The transmission properties and refractive index sensitivity of various configurations of the sensor are systematically investigated. An asymmetric Fano [...] Read more.

A refractive index sensor based on metal-insulator-metal (MIM) waveguides coupled double rectangular cavities is proposed and investigated numerically using the finite element method (FEM). The transmission properties and refractive index sensitivity of various configurations of the sensor are systematically investigated. An asymmetric Fano resonance lineshape is observed in the transmission spectra of the sensor, which is induced by the interference between a broad resonance mode in one rectangular and a narrow one in the other. The effect of various structural parameters on the Fano resonance and the refractive index sensitivity of the system based on Fano resonance is investigated. The proposed plasmonic refractive index sensor shows a maximum sensitivity of 596 nm/RIU. Full article

(This article belongs to the Special Issue Resonator Sensors)

► Show Figures

Figure 1

26 pages, 9343 KiB

Open AccessArticle

On the Feasibility of Wireless Multimedia Sensor Networks over IEEE 802.15.5 Mesh Topologies

by Antonio-Javier Garcia-Sanchez, Fernando Losilla, David Rodenas-Herraiz, Felipe Cruz-Martinez and Felipe Garcia-Sanchez

Sensors 2016, 16(5), 643; https://doi.org/10.3390/s16050643 - 5 May 2016

Cited by 12 | Viewed by 7758

Abstract

Wireless Multimedia Sensor Networks (WMSNs) are a special type of Wireless Sensor Network (WSN) where large amounts of multimedia data are transmitted over networks composed of low power devices. Hierarchical routing protocols typically used in WSNs for multi-path communication tend to overload nodes [...] Read more.

Wireless Multimedia Sensor Networks (WMSNs) are a special type of Wireless Sensor Network (WSN) where large amounts of multimedia data are transmitted over networks composed of low power devices. Hierarchical routing protocols typically used in WSNs for multi-path communication tend to overload nodes located within radio communication range of the data collection unit or data sink. The battery life of these nodes is therefore reduced considerably, requiring frequent battery replacement work to extend the operational life of the WSN system. In a wireless sensor network with mesh topology, any node may act as a forwarder node, thereby enabling multiple routing paths toward any other node or collection unit. In addition, mesh topologies have proven advantages, such as data transmission reliability, network robustness against node failures, and potential reduction in energy consumption. This work studies the feasibility of implementing WMSNs in mesh topologies and their limitations by means of exhaustive computer simulation experiments. To this end, a module developed for the Synchronous Energy Saving (SES) mode of the IEEE 802.15.5 mesh standard has been integrated with multimedia tools to thoroughly test video sequences encoded using H.264 in mesh networks. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2015)

► Show Figures

Graphical abstract

15 pages, 5257 KiB

Open AccessArticle

A Reliable Wireless Control System for Tomato Hydroponics

by Hirofumi Ibayashi, Yukimasa Kaneda, Jungo Imahara, Naoki Oishi, Masahiro Kuroda and Hiroshi Mineno

Sensors 2016, 16(5), 644; https://doi.org/10.3390/s16050644 - 5 May 2016

Cited by 51 | Viewed by 11892

Abstract

Agricultural systems using advanced information and communication (ICT) technology can produce high-quality crops in a stable environment while decreasing the need for manual labor. The system collects a wide variety of environmental data and provides the precise cultivation control needed to produce high [...] Read more.

Agricultural systems using advanced information and communication (ICT) technology can produce high-quality crops in a stable environment while decreasing the need for manual labor. The system collects a wide variety of environmental data and provides the precise cultivation control needed to produce high value-added crops; however, there are the problems of packet transmission errors in wireless sensor networks or system failure due to having the equipment in a hot and humid environment. In this paper, we propose a reliable wireless control system for hydroponic tomato cultivation using the 400 MHz wireless band and the IEEE 802.15.6 standard. The 400 MHz band, which is lower than the 2.4 GHz band, has good obstacle diffraction, and zero-data-loss communication is realized using the guaranteed time-slot method supported by the IEEE 802.15.6 standard. In addition, this system has fault tolerance and a self-healing function to recover from faults such as packet transmission failures due to deterioration of the wireless communication quality. In our basic experiments, the 400 MHz band wireless communication was not affected by the plants’ growth, and the packet error rate was less than that of the 2.4 GHz band. In summary, we achieved a real-time hydroponic liquid supply control with no data loss by applying a 400 MHz band WSN to hydroponic tomato cultivation. Full article

(This article belongs to the Special Issue Sensors for Agriculture)

► Show Figures

Figure 1

17 pages, 3094 KiB

Open AccessArticle

An Integrated Simulation Module for Cyber-Physical Automation Systems

by Francesco Ferracuti, Alessandro Freddi, Andrea Monteriù and Mariorosario Prist

Sensors 2016, 16(5), 645; https://doi.org/10.3390/s16050645 - 5 May 2016

Cited by 20 | Viewed by 9506

Abstract

The integration of Wireless Sensors Networks (WSNs) into Cyber Physical Systems (CPSs) is an important research problem to solve in order to increase the performances, safety, reliability and usability of wireless automation systems. Due to the complexity of real CPSs, emulators and simulators [...] Read more.

The integration of Wireless Sensors Networks (WSNs) into Cyber Physical Systems (CPSs) is an important research problem to solve in order to increase the performances, safety, reliability and usability of wireless automation systems. Due to the complexity of real CPSs, emulators and simulators are often used to replace the real control devices and physical connections during the development stage. The most widespread simulators are free, open source, expandable, flexible and fully integrated into mathematical modeling tools; however, the connection at a physical level and the direct interaction with the real process via the WSN are only marginally tackled; moreover, the simulated wireless sensor motes are not able to generate the analogue output typically required for control purposes. A new simulation module for the control of a wireless cyber-physical system is proposed in this paper. The module integrates the COntiki OS JAva Simulator (COOJA), a cross-level wireless sensor network simulator, and the LabVIEW system design software from National Instruments. The proposed software module has been called “GILOO” (Graphical Integration of Labview and cOOja). It allows one to develop and to debug control strategies over the WSN both using virtual or real hardware modules, such as the National Instruments Real-Time Module platform, the CompactRio, the Supervisory Control And Data Acquisition (SCADA), etc. To test the proposed solution, we decided to integrate it with one of the most popular simulators, i.e., the Contiki OS, and wireless motes, i.e., the Sky mote. As a further contribution, the Contiki Sky DAC driver and a new “Advanced Sky GUI” have been proposed and tested in the COOJA Simulator in order to provide the possibility to develop control over the WSN. To test the performances of the proposed GILOO software module, several experimental tests have been made, and interesting preliminary results are reported. The GILOO module has been applied to a smart home mock-up where a networked control has been developed for the LED lighting system. Full article

(This article belongs to the Special Issue Enabling the Move from Wireless Sensor Networks to Internet of Things and Cyber-Physical Systems)

► Show Figures

Graphical abstract

11 pages, 1326 KiB

Open AccessArticle

Reliability of Sleep Measures from Four Personal Health Monitoring Devices Compared to Research-Based Actigraphy and Polysomnography

by Janna Mantua, Nickolas Gravel and Rebecca M. C. Spencer

Sensors 2016, 16(5), 646; https://doi.org/10.3390/s16050646 - 5 May 2016

Cited by 260 | Viewed by 20300

Abstract

Polysomnography (PSG) is the “gold standard” for monitoring sleep. Alternatives to PSG are of interest for clinical, research, and personal use. Wrist-worn actigraph devices have been utilized in research settings for measures of sleep for over two decades. Whether sleep measures from commercially [...] Read more.

Polysomnography (PSG) is the “gold standard” for monitoring sleep. Alternatives to PSG are of interest for clinical, research, and personal use. Wrist-worn actigraph devices have been utilized in research settings for measures of sleep for over two decades. Whether sleep measures from commercially available devices are similarly valid is unknown. We sought to determine the validity of five wearable devices: Basis Health Tracker, Misfit Shine, Fitbit Flex, Withings Pulse O2, and a research-based actigraph, Actiwatch Spectrum. We used Wilcoxon Signed Rank tests to assess differences between devices relative to PSG and correlational analysis to assess the strength of the relationship. Data loss was greatest for Fitbit and Misfit. For all devices, we found no difference and strong correlation of total sleep time with PSG. Sleep efficiency differed from PSG for Withings, Misfit, Fitbit, and Basis, while Actiwatch mean values did not differ from that of PSG. Only mean values of sleep efficiency (time asleep/time in bed) from Actiwatch correlated with PSG, yet this correlation was weak. Light sleep time differed from PSG (nREM1 + nREM2) for all devices. Measures of Deep sleep time did not differ from PSG (SWS + REM) for Basis. These results reveal the current strengths and limitations in sleep estimates produced by personal health monitoring devices and point to a need for future development. Full article

(This article belongs to the Special Issue Wearable Biomedical Sensors)

► Show Figures

Figure 1

10 pages, 2478 KiB

Open AccessArticle

Electrochemical Detection of Hydrazine Using Poly(dopamine)-Modified Electrodes

by Ji Young Lee, Truc Ly Nguyen, Jun Hui Park and Byung-Kwon Kim

Sensors 2016, 16(5), 647; https://doi.org/10.3390/s16050647 - 5 May 2016

Cited by 35 | Viewed by 7880

Abstract

We have developed a simple and selective method for the electrochemical detection of hydrazine (HZ) using poly(dopamine) (pDA)-modified indium tin oxide (ITO) electrodes. Modification with pDA was easily achieved by submerging the ITO electrode in a DA solution for 30 min. The electrocatalytic [...] Read more.

We have developed a simple and selective method for the electrochemical detection of hydrazine (HZ) using poly(dopamine) (pDA)-modified indium tin oxide (ITO) electrodes. Modification with pDA was easily achieved by submerging the ITO electrode in a DA solution for 30 min. The electrocatalytic oxidation of HZ on the pDA-modified ITO electrode was measured by cyclic voltammetry. In buffer solution, the concentration range for linear HZ detection was 100 µM–10 mM, and the detection limit was 1 µM. The proposed method was finally used to determine HZ in tap water to simulate the analysis of real samples. This method showed good recovery (94%–115%) and was not affected by the other species present in the tap water samples. Full article

(This article belongs to the Section Chemical Sensors)

► Show Figures

Graphical abstract

14 pages, 4420 KiB

Open AccessArticle

Development of a Near Ground Remote Sensing System

by Yanchao Zhang, Yuzhao Xiao, Zaichun Zhuang, Liping Zhou, Fei Liu and Yong He

Sensors 2016, 16(5), 648; https://doi.org/10.3390/s16050648 - 6 May 2016

Cited by 11 | Viewed by 5985

Abstract

Unmanned Aerial Vehicles (UAVs) have shown great potential in agriculture and are increasingly being developed for agricultural use. There are still a lot of experiments that need to be done to improve their performance and explore new uses, but experiments using UAVs are [...] Read more.

Unmanned Aerial Vehicles (UAVs) have shown great potential in agriculture and are increasingly being developed for agricultural use. There are still a lot of experiments that need to be done to improve their performance and explore new uses, but experiments using UAVs are limited by many conditions like weather and location and the time it takes to prepare for a flight. To promote UAV remote sensing, a near ground remote sensing platform was developed. This platform consists of three major parts: (1) mechanical structures like a horizontal rail, vertical cylinder, and three axes gimbal; (2) power supply and control parts; (3) onboard application components. This platform covers five degrees of freedom (DOFs): horizontal, vertical, pitch, roll, yaw. A stm32 ARM single chip was used as the controller of the whole platform and another stm32 MCU was used to stabilize the gimbal. The gimbal stabilizer communicates with the main controller via a CAN bus. A multispectral camera was mounted on the gimbal. Software written in C++ language was developed as the graphical user interface. Operating parameters were set via this software and the working status was displayed in this software. To test how well the system works, a laser distance meter was used to measure the slide rail’s repeat accuracy. A 3-axis vibration analyzer was used to test the system stability. Test results show that the horizontal repeat accuracy was less than 2 mm; vertical repeat accuracy was less than 1 mm; vibration was less than 2 g and remained at an acceptable level. This system has high accuracy and stability and can therefore be used for various near ground remote sensing studies. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Graphical abstract

16 pages, 3352 KiB

Open AccessArticle

Frequency Optimization for Enhancement of Surface Defect Classification Using the Eddy Current Technique

by Mengbao Fan, Qi Wang, Binghua Cao, Bo Ye, Ali Imam Sunny and Guiyun Tian

Sensors 2016, 16(5), 649; https://doi.org/10.3390/s16050649 - 7 May 2016

Cited by 35 | Viewed by 7151

Abstract

Eddy current testing is quite a popular non-contact and cost-effective method for nondestructive evaluation of product quality and structural integrity. Excitation frequency is one of the key performance factors for defect characterization. In the literature, there are many interesting papers dealing with wide [...] Read more.

Eddy current testing is quite a popular non-contact and cost-effective method for nondestructive evaluation of product quality and structural integrity. Excitation frequency is one of the key performance factors for defect characterization. In the literature, there are many interesting papers dealing with wide spectral content and optimal frequency in terms of detection sensitivity. However, research activity on frequency optimization with respect to characterization performances is lacking. In this paper, an investigation into optimum excitation frequency has been conducted to enhance surface defect classification performance. The influences of excitation frequency for a group of defects were revealed in terms of detection sensitivity, contrast between defect features, and classification accuracy using kernel principal component analysis (KPCA) and a support vector machine (SVM). It is observed that probe signals are the most sensitive on the whole for a group of defects when excitation frequency is set near the frequency at which maximum probe signals are retrieved for the largest defect. After the use of KPCA, the margins between the defect features are optimum from the perspective of the SVM, which adopts optimal hyperplanes for structure risk minimization. As a result, the best classification accuracy is obtained. The main contribution is that the influences of excitation frequency on defect characterization are interpreted, and experiment-based procedures are proposed to determine the optimal excitation frequency for a group of defects rather than a single defect with respect to optimal characterization performances. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Graphical abstract

13 pages, 3671 KiB

Open AccessArticle

A Magnetoresistive Tactile Sensor for Harsh Environment Applications

by Ahmed Alfadhel, Mohammed Asadullah Khan, Susana Cardoso, Diana Leitao and Jürgen Kosel

Sensors 2016, 16(5), 650; https://doi.org/10.3390/s16050650 - 7 May 2016

Cited by 44 | Viewed by 12559

Abstract

A magnetoresistive tactile sensor is reported, which is capable of working in high temperatures up to 140 °C. Hair-like bioinspired structures, known as cilia, made out of permanent magnetic nanocomposite material on top of spin-valve giant magnetoresistive (GMR) sensors are used for tactile [...] Read more.

A magnetoresistive tactile sensor is reported, which is capable of working in high temperatures up to 140 °C. Hair-like bioinspired structures, known as cilia, made out of permanent magnetic nanocomposite material on top of spin-valve giant magnetoresistive (GMR) sensors are used for tactile sensing at high temperatures. The magnetic nanocomposite, consisting of iron nanowires incorporated into the polymer polydimethylsiloxane (PDMS), is very flexible, biocompatible, has high remanence, and is also resilient to antagonistic sensing ambient. When the cilia come in contact with a surface, they deflect in compliance with the surface topology. This yields a change of the GMR sensor signal, enabling the detection of extremely fine features. The spin-valve is covered with a passivation layer, which enables adequate performance in spite of harsh environmental conditions, as demonstrated in this paper for high temperature. Full article

(This article belongs to the Special Issue Magnetoresistive Sensors under Extreme Conditions)

► Show Figures

Graphical abstract

20 pages, 3392 KiB

Open AccessArticle

Improved Reconstruction of Radio Holographic Signal for Forward Scatter Radar Imaging

by Cheng Hu, Changjiang Liu, Rui Wang and Tao Zeng

Sensors 2016, 16(5), 651; https://doi.org/10.3390/s16050651 - 7 May 2016

Cited by 5 | Viewed by 5639

Abstract

Forward scatter radar (FSR), as a specially configured bistatic radar, is provided with the capabilities of target recognition and classification by the Shadow Inverse Synthetic Aperture Radar (SISAR) imaging technology. This paper mainly discusses the reconstruction of radio holographic signal (RHS), which is [...] Read more.

Forward scatter radar (FSR), as a specially configured bistatic radar, is provided with the capabilities of target recognition and classification by the Shadow Inverse Synthetic Aperture Radar (SISAR) imaging technology. This paper mainly discusses the reconstruction of radio holographic signal (RHS), which is an important procedure in the signal processing of FSR SISAR imaging. Based on the analysis of signal characteristics, the method for RHS reconstruction is improved in two parts: the segmental Hilbert transformation and the reconstruction of mainlobe RHS. In addition, a quantitative analysis of the method’s applicability is presented by distinguishing between the near field and far field in forward scattering. Simulation results validated the method’s advantages in improving the accuracy of RHS reconstruction and imaging. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Graphical abstract

18 pages, 3599 KiB

Open AccessArticle

Fuzzy-Based Hybrid Control Algorithm for the Stabilization of a Tri-Rotor UAV

by Zain Anwar Ali, Daobo Wang and Muhammad Aamir

Sensors 2016, 16(5), 652; https://doi.org/10.3390/s16050652 - 9 May 2016

Cited by 44 | Viewed by 7834

Abstract

In this paper, a new and novel mathematical fuzzy hybrid scheme is proposed for the stabilization of a tri-rotor unmanned aerial vehicle (UAV). The fuzzy hybrid scheme consists of a fuzzy logic controller, regulation pole-placement tracking (RST) controller with model reference adaptive control [...] Read more.

In this paper, a new and novel mathematical fuzzy hybrid scheme is proposed for the stabilization of a tri-rotor unmanned aerial vehicle (UAV). The fuzzy hybrid scheme consists of a fuzzy logic controller, regulation pole-placement tracking (RST) controller with model reference adaptive control (MRAC), in which adaptive gains of the RST controller are being fine-tuned by a fuzzy logic controller. Brushless direct current (BLDC) motors are installed in the triangular frame of the tri-rotor UAV, which helps maintain control on its motion and different altitude and attitude changes, similar to rotorcrafts. MRAC-based MIT rule is proposed for system stability. Moreover, the proposed hybrid controller with nonlinear flight dynamics is shown in the presence of translational and rotational velocity components. The performance of the proposed algorithm is demonstrated via MATLAB simulations, in which the proposed fuzzy hybrid controller is compared with the existing adaptive RST controller. It shows that our proposed algorithm has better transient performance with zero steady-state error, and fast convergence towards stability. Full article

(This article belongs to the Special Issue UAV-Based Remote Sensing)

► Show Figures

Figure 1

21 pages, 544 KiB

Open AccessArticle

Cubature Information SMC-PHD for Multi-Target Tracking

by Zhe Liu, Zulin Wang and Mai Xu

Sensors 2016, 16(5), 653; https://doi.org/10.3390/s16050653 - 9 May 2016

Cited by 8 | Viewed by 4787

Abstract

In multi-target tracking, the key problem lies in estimating the number and states of individual targets, in which the challenge is the time-varying multi-target numbers and states. Recently, several multi-target tracking approaches, based on the sequential Monte Carlo probability hypothesis density (SMC-PHD) filter, [...] Read more.

In multi-target tracking, the key problem lies in estimating the number and states of individual targets, in which the challenge is the time-varying multi-target numbers and states. Recently, several multi-target tracking approaches, based on the sequential Monte Carlo probability hypothesis density (SMC-PHD) filter, have been presented to solve such a problem. However, most of these approaches select the transition density as the importance sampling (IS) function, which is inefficient in a nonlinear scenario. To enhance the performance of the conventional SMC-PHD filter, we propose in this paper two approaches using the cubature information filter (CIF) for multi-target tracking. More specifically, we first apply the posterior intensity as the IS function. Then, we propose to utilize the CIF algorithm with a gating method to calculate the IS function, namely CISMC-PHD approach. Meanwhile, a fast implementation of the CISMC-PHD approach is proposed, which clusters the particles into several groups according to the Gaussian mixture components. With the constructed components, the IS function is approximated instead of particles. As a result, the computational complexity of the CISMC-PHD approach can be significantly reduced. The simulation results demonstrate the effectiveness of our approaches. Full article

(This article belongs to the Special Issue UAV-Based Remote Sensing)

► Show Figures

Graphical abstract

24 pages, 1635 KiB

Open AccessArticle

Extrinsic Calibration of Camera Networks Based on Pedestrians

by Junzhi Guan, Francis Deboeverie, Maarten Slembrouck, Dirk Van Haerenborgh, Dimitri Van Cauwelaert, Peter Veelaert and Wilfried Philips

Sensors 2016, 16(5), 654; https://doi.org/10.3390/s16050654 - 9 May 2016

Cited by 23 | Viewed by 5685

Abstract

In this paper, we propose a novel extrinsic calibration method for camera networks by analyzing tracks of pedestrians. First of all, we extract the center lines of walking persons by detecting their heads and feet in the camera images. We propose an easy [...] Read more.

In this paper, we propose a novel extrinsic calibration method for camera networks by analyzing tracks of pedestrians. First of all, we extract the center lines of walking persons by detecting their heads and feet in the camera images. We propose an easy and accurate method to estimate the 3D positions of the head and feet w.r.t. a local camera coordinate system from these center lines. We also propose a RANSAC-based orthogonal Procrustes approach to compute relative extrinsic parameters connecting the coordinate systems of cameras in a pairwise fashion. Finally, we refine the extrinsic calibration matrices using a method that minimizes the reprojection error. While existing state-of-the-art calibration methods explore epipolar geometry and use image positions directly, the proposed method first computes 3D positions per camera and then fuses the data. This results in simpler computations and a more flexible and accurate calibration method. Another advantage of our method is that it can also handle the case of persons walking along straight lines, which cannot be handled by most of the existing state-of-the-art calibration methods since all head and feet positions are co-planar. This situation often happens in real life. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

19 pages, 394 KiB

Open AccessArticle

CoR-MAC: Contention over Reservation MAC Protocol for Time-Critical Services in Wireless Body Area Sensor Networks

by Jeongseok Yu, Laihyuk Park, Junho Park, Sungrae Cho and Changsup Keum

Sensors 2016, 16(5), 656; https://doi.org/10.3390/s16050656 - 9 May 2016

Cited by 28 | Viewed by 5288

Abstract

Reserving time slots for urgent data, such as life-critical information, seems to be very attractive to guarantee their deadline requirements in wireless body area sensor networks (WBASNs). On the other hand, this reservation imposes a negative impact on performance for the utilization of [...] Read more.

Reserving time slots for urgent data, such as life-critical information, seems to be very attractive to guarantee their deadline requirements in wireless body area sensor networks (WBASNs). On the other hand, this reservation imposes a negative impact on performance for the utilization of a channel. This paper proposes a new channel access scheme referred to as the contention over reservation MAC (CoR-MAC) protocol for time-critical services in wireless body area sensor networks. CoR-MAC uses the dual reservation; if the reserved time slots are known to be vacant, other nodes can access the time slots by contention-based reservation to maximize the utilization of a channel and decrease the delay of the data. To measure the effectiveness of the proposed scheme against IEEE 802.15.4 and IEEE 802.15.6, we evaluated their performances with various performance indexes. The CoR-MAC showed 50% to 850% performance improvement in terms of the delay of urgent and time-critical data according to the number of nodes. Full article

(This article belongs to the Special Issue Intelligent Internet of Things (IoT) Networks)

► Show Figures

Figure 1

13 pages, 4667 KiB

Open AccessArticle

Dynamic Response Analysis of Microflow Electrochemical Sensors with Two Types of Elastic Membrane

by Qiuzhan Zhou, Chunhui Wang, Yongzhi Chen, Shuozhang Chen and Jun Lin

Sensors 2016, 16(5), 657; https://doi.org/10.3390/s16050657 - 9 May 2016

Cited by 4 | Viewed by 4918

Abstract

The Molecular Electric Transducer (MET), widely applied for vibration measurement, has excellent sensitivity and dynamic response at low frequencies. The elastic membrane in the MET is a significant factor with an obvious effect on the performance of the MET in the low frequency [...] Read more.

The Molecular Electric Transducer (MET), widely applied for vibration measurement, has excellent sensitivity and dynamic response at low frequencies. The elastic membrane in the MET is a significant factor with an obvious effect on the performance of the MET in the low frequency domain and is the focus of this paper. In simulation experiments, the elastic membrane and the reaction cavity of the MET were analysed in a model based on the multiphysics finite element method. Meanwhile, the effects caused by the elastic membrane elements are verified in this paper. With the numerical simulation and practical experiments, a suitable elastic membrane can be designed for different cavity structures. Thus, the MET can exhibit the best dynamic response characteristics to measure the vibration signals. With the new method presented in this paper, it is possible to develop and optimize the characteristics of the MET effectively, and the dynamic characteristics of the MET can be improved in a thorough and systematic manner. Full article

(This article belongs to the Section Chemical Sensors)

► Show Figures

Figure 1

12 pages, 3540 KiB

Open AccessArticle

Fluoride Anion Recognition by a Multifunctional Urea Derivative: An Experimental and Theoretical Study

by Jana Schiller, Raúl Pérez-Ruiz, Diego Sampedro, Eugenia Marqués-López, Raquel P. Herrera and David Díaz Díaz

Sensors 2016, 16(5), 658; https://doi.org/10.3390/s16050658 - 9 May 2016

Cited by 14 | Viewed by 9293

Abstract

In this work we demonstrate the ability of a multifaceted N,N′-disubstituted urea to selectively recognize fluoride anion (F⁻) among other halides. This additional function is now added to its already reported organocatalytic and organogelator properties. The signaling mechanism [...] Read more.

In this work we demonstrate the ability of a multifaceted N,N′-disubstituted urea to selectively recognize fluoride anion (F⁻) among other halides. This additional function is now added to its already reported organocatalytic and organogelator properties. The signaling mechanism relies on the formation of a charge-transfer (CT) complex between the urea-based sensor and F¯ in the ground state with a high association constant as demonstrated by absorption and fluorescence spectroscopy. The nature of the hydrogen bonding interaction between the sensor and F¯ was established by ¹H-NMR studies and theoretical calculations. Moreover, the recovery of the sensor was achieved by addition of methanol. Full article

(This article belongs to the Special Issue Colorimetric and Fluorescent Sensor)

► Show Figures

Graphical abstract

11 pages, 1937 KiB

Open AccessArticle

Investigation of Hemoglobin/Gold Nanoparticle Heterolayer on Micro-Gap for Electrochemical Biosensor Application

by Taek Lee, Tae-Hyung Kim, Jinho Yoon, Yong-Ho Chung, Ji Young Lee and Jeong-Woo Choi

Sensors 2016, 16(5), 660; https://doi.org/10.3390/s16050660 - 9 May 2016

Cited by 11 | Viewed by 7800

Abstract

In the present study, we fabricated a hemoglobin/gold nanoparticle (Hb/GNP) heterolayer immobilized on the Au micro-gap to confirm H₂O₂ detection with a signal-enhancement effect. The hemoglobin which contained the heme group catalyzed the reduction of H₂O₂. [...] Read more.

In the present study, we fabricated a hemoglobin/gold nanoparticle (Hb/GNP) heterolayer immobilized on the Au micro-gap to confirm H₂O₂ detection with a signal-enhancement effect. The hemoglobin which contained the heme group catalyzed the reduction of H₂O₂. To facilitate the electron transfer between hemoglobin and Au micro-gap electrode, a gold nanoparticle was introduced. The Au micro-gap electrode that has gap size of 5 µm was fabricated by conventional photolithographic technique to locate working and counter electrodes oppositely in a single chip for the signal sensitivity and reliability. The hemoglobin was self-assembled onto the Au surface via chemical linker 6-mercaptohexanoic acid (6-MHA). Then, the gold nanoparticles were adsorbed onto hemoglobin/6-MHA heterolayers by the layer-by-layer (LbL) method. The fabrication of the Hb/GNP heterolayer was confirmed by atomic force microscopy (AFM) and surface-enhanced Raman spectroscopy (SERS). The redox property and H₂O₂ detection of Hb/GNP on the micro-gap electrode was investigated by a cyclic voltammetry (CV) experiment. Taken together, the present results show that the electrochemical signal-enhancement effect of a hemoglobin/nanoparticle heterolayer was well confirmed on the micro-scale electrode for biosensor applications. Full article

► Show Figures

Figure 1

15 pages, 1023 KiB

Open AccessArticle

Determination of the Optimum Harvest Window for Apples Using the Non-Destructive Biospeckle Method

by Anna Skic, Monika Szymańska-Chargot, Beata Kruk, Monika Chylińska, Piotr Mariusz Pieczywek, Andrzej Kurenda, Artur Zdunek and Krzysztof P. Rutkowski

Sensors 2016, 16(5), 661; https://doi.org/10.3390/s16050661 - 10 May 2016

Cited by 39 | Viewed by 7708

Abstract

Determination of the optimum harvest window plays a key role in the agro-food chain as the quality of fruit depends on the right harvesting time and appropriate storage conditions during the postharvest period. Usually, indices based on destructive measurements are used for this [...] Read more.

Determination of the optimum harvest window plays a key role in the agro-food chain as the quality of fruit depends on the right harvesting time and appropriate storage conditions during the postharvest period. Usually, indices based on destructive measurements are used for this purpose, like the De Jager Index (PFW-1), FARS index and the most popular Streif Index. In this study, we proposed a biospeckle method for the evaluation of the optimum harvest window (OHW) of the “Ligol” and “Szampion” apple cultivars. The experiment involved eight different maturity stages, of which four were followed by long cold storage and shelf life to assist the determination of the optimum harvest window. The biospeckle activity was studied in relation to standard quality attributes (firmness, acidity, starch, soluble solids content, Streif Index) and physiological parameters (respiration and ethylene emission) of both apple cultivars. Changes of biospeckle activity (BA) over time showed moderate relationships with biochemical changes during apple maturation and ripening. The harvest date suggested by the Streif Index and postharvest quality indicators matched with characteristic decrease in BA. The ability of biospeckle method to characterize the biological state of apples was confirmed by significant correlations of BA with firmness, starch index, total soluble solids and Streif Index, as well as good match with changes in carbon dioxide and ethylene emission. However, it should be noted that correlations between variables changing over time are not as meaningful as independent observations. Also, it is a well-known property of the Pearson’s correlation that its value is highly susceptible to outlier data. Due to its non-selective nature the BA reflected only the current biological state of the fruit and could be affected by many other factors. The investigations showed that the optimum harvest window for apples was indicated by the characteristic drop of BA during pre-harvest development. Despite this, at the current state of development the BA method cannot be used as an indicator alone. Due to rather poor results for prediction in OHW the BA measurements should be supported by other destructive methods to compensate its low selectivity. Full article

(This article belongs to the Special Issue Sensors for Agriculture)

► Show Figures

Figure 1

11 pages, 7602 KiB

Open AccessArticle

An Efficient Seam Elimination Method for UAV Images Based on Wallis Dodging and Gaussian Distance Weight Enhancement

by Jinyan Tian, Xiaojuan Li, Fuzhou Duan, Junqian Wang and Yang Ou

Sensors 2016, 16(5), 662; https://doi.org/10.3390/s16050662 - 10 May 2016

Cited by 22 | Viewed by 5945

Abstract

The rapid development of Unmanned Aerial Vehicle (UAV) remote sensing conforms to the increasing demand for the low-altitude very high resolution (VHR) image data. However, high processing speed of massive UAV data has become an indispensable prerequisite for its applications in various industry [...] Read more.

The rapid development of Unmanned Aerial Vehicle (UAV) remote sensing conforms to the increasing demand for the low-altitude very high resolution (VHR) image data. However, high processing speed of massive UAV data has become an indispensable prerequisite for its applications in various industry sectors. In this paper, we developed an effective and efficient seam elimination approach for UAV images based on Wallis dodging and Gaussian distance weight enhancement (WD-GDWE). The method encompasses two major steps: first, Wallis dodging was introduced to adjust the difference of brightness between the two matched images, and the parameters in the algorithm were derived in this study. Second, a Gaussian distance weight distribution method was proposed to fuse the two matched images in the overlap region based on the theory of the First Law of Geography, which can share the partial dislocation in the seam to the whole overlap region with an effect of smooth transition. This method was validated at a study site located in Hanwang (Sichuan, China) which was a seriously damaged area in the 12 May 2008 enchuan Earthquake. Then, a performance comparison between WD-GDWE and the other five classical seam elimination algorithms in the aspect of efficiency and effectiveness was conducted. Results showed that WD-GDWE is not only efficient, but also has a satisfactory effectiveness. This method is promising in advancing the applications in UAV industry especially in emergency situations. Full article

(This article belongs to the Special Issue UAV-Based Remote Sensing)

► Show Figures

Graphical abstract

17 pages, 2578 KiB

Open AccessArticle

Analysis of Subthreshold Current Reset Noise in Image Sensors

by Nobukazu Teranishi

Sensors 2016, 16(5), 663; https://doi.org/10.3390/s16050663 - 10 May 2016

Cited by 5 | Viewed by 8937

Abstract

To discuss the reset noise generated by slow subthreshold currents in image sensors, intuitive and simple analytical forms are derived, in spite of the subthreshold current nonlinearity. These solutions characterize the time evolution of the reset noise during the reset operation. With soft [...] Read more.

To discuss the reset noise generated by slow subthreshold currents in image sensors, intuitive and simple analytical forms are derived, in spite of the subthreshold current nonlinearity. These solutions characterize the time evolution of the reset noise during the reset operation. With soft reset, the reset noise tends to

\sqrt{m k T / 2 C_{P D}}

when

t \to \infty

, in full agreement with previously published results. In this equation,

C_{P D}

is the photodiode (PD) capacitance and m is a constant. The noise has an asymptotic time dependence of

t^{- 1}

, even though the asymptotic time dependence of the average (deterministic) PD voltage is as slow as

\log t

. The flush reset method is effective because the hard reset part eliminates image lag, and the soft reset part reduces the noise to soft reset level. The feedback reset with reverse taper control method shows both a fast convergence and a good reset noise reduction. When the feedback amplifier gain, A, is larger, even small value of capacitance,

C_{P}

, between the input and output of the feedback amplifier will drastically decrease the reset noise. If the feedback is sufficiently fast, the reset noise limit when

t \to \infty

, becomes

\frac{m k T {(C_{P D} + C_{P 1})}^{2}}{2 q^{2} A (C_{P D} + (1 + A) C_{P})}

in terms of the number of electron in the PD. According to this simple model, if C_PD = 10 fF, C_P/C_PD = 0.01, and A = 2700 are assumed, deep sub-electron rms reset noise is possible. Full article

(This article belongs to the Special Issue Photon-Counting Image Sensors)

► Show Figures

Graphical abstract

18 pages, 7191 KiB

Open AccessArticle

Classification of Horse Gaits Using FCM-Based Neuro-Fuzzy Classifier from the Transformed Data Information of Inertial Sensor

by Jae-Neung Lee, Myung-Won Lee, Yeong-Hyeon Byeon, Won-Sik Lee and Keun-Chang Kwak

Sensors 2016, 16(5), 664; https://doi.org/10.3390/s16050664 - 10 May 2016

Cited by 16 | Viewed by 6938

Abstract

In this study, we classify four horse gaits (walk, sitting trot, rising trot, canter) of three breeds of horse (Jeju, Warmblood, and Thoroughbred) using a neuro-fuzzy classifier (NFC) of the Takagi-Sugeno-Kang (TSK) type from data information transformed by a wavelet packet (WP). The [...] Read more.

In this study, we classify four horse gaits (walk, sitting trot, rising trot, canter) of three breeds of horse (Jeju, Warmblood, and Thoroughbred) using a neuro-fuzzy classifier (NFC) of the Takagi-Sugeno-Kang (TSK) type from data information transformed by a wavelet packet (WP). The design of the NFC is accomplished by using a fuzzy c-means (FCM) clustering algorithm that can solve the problem of dimensionality increase due to the flexible scatter partitioning. For this purpose, we use the rider’s hip motion from the sensor information collected by inertial sensors as feature data for the classification of a horse’s gaits. Furthermore, we develop a coaching system under both real horse riding and simulator environments and propose a method for analyzing the rider’s motion. Using the results of the analysis, the rider can be coached in the correct motion corresponding to the classified gait. To construct a motion database, the data collected from 16 inertial sensors attached to a motion capture suit worn by one of the country’s top-level horse riding experts were used. Experiments using the original motion data and the transformed motion data were conducted to evaluate the classification performance using various classifiers. The experimental results revealed that the presented FCM-NFC showed a better accuracy performance (97.5%) than a neural network classifier (NNC), naive Bayesian classifier (NBC), and radial basis function network classifier (RBFNC) for the transformed motion data. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

21 pages, 904 KiB

Open AccessArticle

Optimizing Retransmission Threshold in Wireless Sensor Networks

by Ran Bi, Yingshu Li, Guozhen Tan and Liang Sun

Sensors 2016, 16(5), 665; https://doi.org/10.3390/s16050665 - 10 May 2016

Cited by 5 | Viewed by 4797

Abstract

The retransmission threshold in wireless sensor networks is critical to the latency of data delivery in the networks. However, existing works on data transmission in sensor networks did not consider the optimization of the retransmission threshold, and they simply set the same retransmission [...] Read more.

The retransmission threshold in wireless sensor networks is critical to the latency of data delivery in the networks. However, existing works on data transmission in sensor networks did not consider the optimization of the retransmission threshold, and they simply set the same retransmission threshold for all sensor nodes in advance. The method did not take link quality and delay requirement into account, which decreases the probability of a packet passing its delivery path within a given deadline. This paper investigates the problem of finding optimal retransmission thresholds for relay nodes along a delivery path in a sensor network. The object of optimizing retransmission thresholds is to maximize the summation of the probability of the packet being successfully delivered to the next relay node or destination node in time. A dynamic programming-based distributed algorithm for finding optimal retransmission thresholds for relay nodes along a delivery path in the sensor network is proposed. The time complexity is

O (n Δ \cdot {max}_{1 \leq i \leq n} {u_{i}})

, where

u_{i}

is the given upper bound of the retransmission threshold of sensor node i in a given delivery path, n is the length of the delivery path and Δ is the given upper bound of the transmission delay of the delivery path. If Δ is greater than the polynomial, to reduce the time complexity, a linear programming-based

(1 + p_{m i n})

-approximation algorithm is proposed. Furthermore, when the ranges of the upper and lower bounds of retransmission thresholds are big enough, a Lagrange multiplier-based distributed

O (1)

-approximation algorithm with time complexity

O (1)

is proposed. Experimental results show that the proposed algorithms have better performance. Full article

(This article belongs to the Special Issue Identification, Information & Knowledge in the Internet of Things)

► Show Figures

Figure 1

17 pages, 3190 KiB

Open AccessArticle

Enabling UAV Navigation with Sensor and Environmental Uncertainty in Cluttered and GPS-Denied Environments

by Fernando Vanegas and Felipe Gonzalez

Sensors 2016, 16(5), 666; https://doi.org/10.3390/s16050666 - 10 May 2016

Cited by 45 | Viewed by 12697

Abstract

Unmanned Aerial Vehicles (UAV) can navigate with low risk in obstacle-free environments using ground control stations that plan a series of GPS waypoints as a path to follow. This GPS waypoint navigation does however become dangerous in environments where the GPS signal is [...] Read more.

Unmanned Aerial Vehicles (UAV) can navigate with low risk in obstacle-free environments using ground control stations that plan a series of GPS waypoints as a path to follow. This GPS waypoint navigation does however become dangerous in environments where the GPS signal is faulty or is only present in some places and when the airspace is filled with obstacles. UAV navigation then becomes challenging because the UAV uses other sensors, which in turn generate uncertainty about its localisation and motion systems, especially if the UAV is a low cost platform. Additional uncertainty affects the mission when the UAV goal location is only partially known and can only be discovered by exploring and detecting a target. This navigation problem is established in this research as a Partially-Observable Markov Decision Process (POMDP), so as to produce a policy that maps a set of motion commands to belief states and observations. The policy is calculated and updated on-line while flying with a newly-developed system for UAV Uncertainty-Based Navigation (UBNAV), to navigate in cluttered and GPS-denied environments using observations and executing motion commands instead of waypoints. Experimental results in both simulation and real flight tests show that the UAV finds a path on-line to a region where it can explore and detect a target without colliding with obstacles. UBNAV provides a new method and an enabling technology for scientists to implement and test UAV navigation missions with uncertainty where targets must be detected using on-line POMDP in real flight scenarios. Full article

(This article belongs to the Special Issue UAV Sensors for Environmental Monitoring)

► Show Figures

Figure 1

32 pages, 9659 KiB

Open AccessArticle

A Dual-Field Sensing Scheme for a Guidance System for the Blind

by Qing Lin and Youngjoon Han

Sensors 2016, 16(5), 667; https://doi.org/10.3390/s16050667 - 11 May 2016

Cited by 7 | Viewed by 6973

Abstract

An electronic guidance system is very helpful in improving blind people’s perceptions in a local environment. In our previous work “Lin, Q.; Han, Y. A Context-Aware-Based Audio Guidance System for Blind People Using a Multimodal Profile Model. Sensors 2014, 14, 18670–18700”, a context-aware [...] Read more.

An electronic guidance system is very helpful in improving blind people’s perceptions in a local environment. In our previous work “Lin, Q.; Han, Y. A Context-Aware-Based Audio Guidance System for Blind People Using a Multimodal Profile Model. Sensors 2014, 14, 18670–18700”, a context-aware guidance system using a combination of a laser scanner and a camera was proposed. By using a near-field graphical model, the proposed system could interpret a near-field scene in very high resolution. In this paper, our work is extended by adding a far-field graphical model. The integration of the near-field and the far-field models constitutes a dual-field sensing scheme. In the near-field range, reliable inference of the ground and object status is obtained by fusing range data and image data using the near-field graphical model. In the far-field range, which only the camera can cover, the far-field graphical model is proposed to interpret far-field image data based on appearance and spatial prototypes built using the near-field interpreted data. The dual-field sensing scheme provides a solution for the guidance systems to optimise their scene interpretation capability using simple sensor configurations. Experiments under various local conditions were conducted to show the efficiency of the proposed scheme in improving blind people’s perceptions in urban environments. Full article

(This article belongs to the Collection Sensors for Globalized Healthy Living and Wellbeing)

► Show Figures

Figure 1

20 pages, 5171 KiB

Open AccessArticle

A High Sensitivity IDC-Electronic Tongue Using Dielectric/Sensing Membranes with Solvatochromic Dyes

by Md. Rajibur Rahaman Khan, Alireza Khalilian and Shin-Won Kang

Sensors 2016, 16(5), 668; https://doi.org/10.3390/s16050668 - 10 May 2016

Cited by 17 | Viewed by 9651

Abstract

In this paper, an electronic tongue/taste sensor array containing different interdigitated capacitor (IDC) sensing elements to detect different types of tastes, such as sweetness (glucose), saltiness (NaCl), sourness (HCl), bitterness (quinine-HCl), and umami (monosodium glutamate) is proposed. We present for the first time [...] Read more.

In this paper, an electronic tongue/taste sensor array containing different interdigitated capacitor (IDC) sensing elements to detect different types of tastes, such as sweetness (glucose), saltiness (NaCl), sourness (HCl), bitterness (quinine-HCl), and umami (monosodium glutamate) is proposed. We present for the first time an IDC electronic tongue using sensing membranes containing solvatochromic dyes. The proposed highly sensitive (30.64 mV/decade sensitivity) IDC electronic tongue has fast response and recovery times of about 6 s and 5 s, respectively, with extremely stable responses, and is capable of linear sensing performance (R² ≈ 0.985 correlation coefficient) over the wide dynamic range of 1 µM to 1 M. The designed IDC electronic tongue offers excellent reproducibility, with a relative standard deviation (RSD) of about 0.029. The proposed device was found to have better sensing performance than potentiometric-, cascoded compatible lateral bipolar transistor (C-CLBT)-, Electronic Tongue (SA402)-, and fiber-optic-based taste sensing systems in what concerns dynamic range width, response time, sensitivity, and linearity. Finally, we applied principal component analysis (PCA) to distinguish between various kinds of taste in mixed taste compounds. Full article

(This article belongs to the Section Biosensors)

► Show Figures

Graphical abstract

11 pages, 2888 KiB

Open AccessArticle

A High-Performance Fluorescence Immunoassay Based on the Relaxation of Quenching, Exemplified by Detection of Cardiac Troponin I

by Seung-Wan Kim, Il-Hoon Cho, Ji-Na Park, Sung-Min Seo and Se-Hwan Paek

Sensors 2016, 16(5), 669; https://doi.org/10.3390/s16050669 - 10 May 2016

Cited by 16 | Viewed by 8961

Abstract

The intramolecular fluorescence self-quenching phenomenon is a major drawback in developing high-performance fluorometric biosensors which use common fluorophores as signal generators. We propose two strategies involving liberation of the fluorescent molecules by means of enzymatic fragmentation of protein or dehybridization of double-stranded DNA. [...] Read more.

The intramolecular fluorescence self-quenching phenomenon is a major drawback in developing high-performance fluorometric biosensors which use common fluorophores as signal generators. We propose two strategies involving liberation of the fluorescent molecules by means of enzymatic fragmentation of protein or dehybridization of double-stranded DNA. In the former, bovine serum albumin (BSA) was coupled with the fluorescent BODIPY dye (Red BSA), and then immobilized on a solid surface. When the insolubilized Red BSA was treated with proteinase K (10 units/mL) for 30 min, the fluorescent signal was significantly increased (3.5-fold) compared to the untreated control. In the second case, fluorophore-tagged DNA probes were linked to gold nanoparticles by hybridization with capture DNA strands densely immobilized on the surface. The quenched fluorescence signal was recovered (3.7-fold) by thermal dehybridization, which was induced with light of a specific wavelength (e.g., 530 nm) for less than 1 min. We next applied the Red BSA self-quenching relaxation technique employing enzymatic fragmentation to a high-performance immunoassay of cardiac troponin I (cTnI) in a microtiter plate format. The detection limit was 0.19 ng/mL cTnI, and the fluorescent signal was enhanced approximately 4.1-fold compared with the conventional method of direct measurement of the fluorescent signal from a non-fragmented fluorophore-labeled antibody. Full article

(This article belongs to the Section Biosensors)

► Show Figures

Figure 1

22 pages, 3009 KiB

Open AccessArticle

Model-Driven Approach for Body Area Network Application Development

by Algimantas Venčkauskas, Vytautas Štuikys, Nerijus Jusas and Renata Burbaitė

Sensors 2016, 16(5), 670; https://doi.org/10.3390/s16050670 - 12 May 2016

Cited by 7 | Viewed by 6408

Abstract

This paper introduces the sensor-networked IoT model as a prototype to support the design of Body Area Network (BAN) applications for healthcare. Using the model, we analyze the synergistic effect of the functional requirements (data collection from the human body and transferring it [...] Read more.

This paper introduces the sensor-networked IoT model as a prototype to support the design of Body Area Network (BAN) applications for healthcare. Using the model, we analyze the synergistic effect of the functional requirements (data collection from the human body and transferring it to the top level) and non-functional requirements (trade-offs between energy-security-environmental factors, treated as Quality-of-Service (QoS)). We use feature models to represent the requirements at the earliest stage for the analysis and describe a model-driven methodology to design the possible BAN applications. Firstly, we specify the requirements as the problem domain (PD) variability model for the BAN applications. Next, we introduce the generative technology (meta-programming as the solution domain (SD)) and the mapping procedure to map the PD feature-based variability model onto the SD feature model. Finally, we create an executable meta-specification that represents the BAN functionality to describe the variability of the problem domain though transformations. The meta-specification (along with the meta-language processor) is a software generator for multiple BAN-oriented applications. We validate the methodology with experiments and a case study to generate a family of programs for the BAN sensor controllers. This enables to obtain the adequate measure of QoS efficiently through the interactive adjustment of the meta-parameter values and re-generation process for the concrete BAN application. Full article

(This article belongs to the Special Issue Security and Privacy in Sensor Networks)

► Show Figures

Figure 1

6 pages, 603 KiB

Open AccessArticle

On the Probabilistic Deployment of Smart Grid Networks in TV White Space

by Angela Sara Cacciapuoti, Marcello Caleffi and Luigi Paura

Sensors 2016, 16(5), 671; https://doi.org/10.3390/s16050671 - 10 May 2016

Cited by 12 | Viewed by 4001

Abstract

To accommodate the rapidly increasing demand for wireless broadband communications in Smart Grid (SG) networks, research efforts are currently ongoing to enable the SG networks to utilize the TV spectrum according to the Cognitive Radio paradigm. To this aim, in this letter, we [...] Read more.

To accommodate the rapidly increasing demand for wireless broadband communications in Smart Grid (SG) networks, research efforts are currently ongoing to enable the SG networks to utilize the TV spectrum according to the Cognitive Radio paradigm. To this aim, in this letter, we develop an analytical framework for the optimal deployment of multiple closely-located SG Neighborhood Area Networks (NANs) concurrently using the same TV spectrum. The objective is to derive the optimal values for both the number of NANs and their coverage. More specifically, regarding the number of NANs, we derive the optimal closed-form expression, i.e., the closed-form expression that assures the deployment of the maximum number of NANs in the considered region satisfying a given collision constraint on the transmissions of the NANs. Regarding the NAN coverage, we derive the optimal closed-form expression, i.e., the closed-form expression of the NAN transmission range that assures the maximum coverage of each NAN in the considered region satisfying the given collision constraint. All the theoretical results are derived by adopting a stochastic approach. Finally, numerical results validate the theoretical analysis. Full article

(This article belongs to the Section Sensor Networks)

► Show Figures

Figure 1

10 pages, 3038 KiB

Open AccessArticle

Modeling of a Single-Notch Microfiber Coupler for High-Sensitivity and Low Detection-Limit Refractive Index Sensing

by Jiali Zhang, Lei Shi, Song Zhu, Xinbiao Xu and Xinliang Zhang

Sensors 2016, 16(5), 672; https://doi.org/10.3390/s16050672 - 11 May 2016

Cited by 6 | Viewed by 5822

Abstract

A highly sensitive refractive index sensor with low detection limit based on an asymmetric optical microfiber coupler is proposed. It is composed of a silica optical microfiber and an As₂Se₃ optical microfiber. Due to the asymmetry of the microfiber materials, [...] Read more.

A highly sensitive refractive index sensor with low detection limit based on an asymmetric optical microfiber coupler is proposed. It is composed of a silica optical microfiber and an As₂Se₃ optical microfiber. Due to the asymmetry of the microfiber materials, a single-notch transmission spectrum is demonstrated by the large refractive index difference between the two optical microfibers. Compared with the symmetric coupler, the bandwidth of the asymmetric structure is over one order of magnitude narrower than that of the former. Therefore, the asymmetric optical microfiber coupler based sensor can reach over one order of magnitude smaller detection limit, which is defined as the minimal detectable refractive index change caused by the surrounding analyte. With the advantage of large evanescent field, the results also show that a sensitivity of up to 3212 nm per refractive index unit with a bandwidth of 12 nm is achieved with the asymmetric optical microfiber coupler. Furthermore, a maximum sensitivity of 4549 nm per refractive index unit can be reached while the radii of the silica optical microfiber and As₂Se₃ optical microfiber are 0.5 μm and a 0.128 μm, respectively. This sensor component may have important potential for low detection-limit physical and biochemical sensing applications. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2016)

► Show Figures

Figure 1

15 pages, 3925 KiB

Open AccessArticle

Wearable Multi-Frequency and Multi-Segment Bioelectrical Impedance Spectroscopy for Unobtrusively Tracking Body Fluid Shifts during Physical Activity in Real-Field Applications: A Preliminary Study

by Federica Villa, Alessandro Magnani, Martina A. Maggioni, Alexander Stahn, Susanna Rampichini, Giampiero Merati and Paolo Castiglioni

Sensors 2016, 16(5), 673; https://doi.org/10.3390/s16050673 - 11 May 2016

Cited by 26 | Viewed by 9598

Abstract

Bioelectrical Impedance Spectroscopy (BIS) allows assessing the composition of body districts noninvasively and quickly, potentially providing important physiological/clinical information. However, neither portable commercial instruments nor more advanced wearable prototypes simultaneously satisfy the demanding needs of unobtrusively tracking body fluid shifts in different segments [...] Read more.

Bioelectrical Impedance Spectroscopy (BIS) allows assessing the composition of body districts noninvasively and quickly, potentially providing important physiological/clinical information. However, neither portable commercial instruments nor more advanced wearable prototypes simultaneously satisfy the demanding needs of unobtrusively tracking body fluid shifts in different segments simultaneously, over a broad frequency range, for long periods and with high measurements rate. These needs are often required to evaluate exercise tests in sports or rehabilitation medicine, or to assess gravitational stresses in aerospace medicine. Therefore, the aim of this work is to present a new wearable prototype for monitoring multi-segment and multi-frequency BIS unobtrusively over long periods. Our prototype guarantees low weight, small size and low power consumption. An analog board with current-injecting and voltage-sensing electrodes across three body segments interfaces a digital board that generates square-wave current stimuli and computes impedance at 10 frequencies from 1 to 796 kHz. To evaluate the information derivable from our device, we monitored the BIS of three body segments in a volunteer before, during and after physical exercise and postural shift. We show that it can describe the dynamics of exercise-induced changes and the effect of a sit-to-stand maneuver in active and inactive muscular districts separately and simultaneously. Full article

(This article belongs to the Special Issue Selected Papers from the 2nd International Electronic Conference on Sensors and Applications)

► Show Figures

Graphical abstract

20 pages, 1357 KiB

Open AccessArticle

Bootstrapping Security Policies for Wearable Apps Using Attributed Structural Graphs

by Ana I. González-Tablas and Juan E. Tapiador

Sensors 2016, 16(5), 674; https://doi.org/10.3390/s16050674 - 11 May 2016

Viewed by 5129

Abstract

We address the problem of bootstrapping security and privacy policies for newly-deployed apps in wireless body area networks (WBAN) composed of smartphones, sensors and other wearable devices. We introduce a framework to model such a WBAN as an undirected graph whose vertices correspond [...] Read more.

We address the problem of bootstrapping security and privacy policies for newly-deployed apps in wireless body area networks (WBAN) composed of smartphones, sensors and other wearable devices. We introduce a framework to model such a WBAN as an undirected graph whose vertices correspond to devices, apps and app resources, while edges model structural relationships among them. This graph is then augmented with attributes capturing the features of each entity together with user-defined tags. We then adapt available graph-based similarity metrics to find the closest app to a new one to be deployed, with the aim of reusing, and possibly adapting, its security policy. We illustrate our approach through a detailed smartphone ecosystem case study. Our results suggest that the scheme can provide users with a reasonably good policy that is consistent with the user’s security preferences implicitly captured by policies already in place. Full article

(This article belongs to the Special Issue Security and Privacy in Sensor Networks)

► Show Figures

Figure 1

12 pages, 3299 KiB

Open AccessArticle

Image Quality Analysis and Optical Performance Requirement for Micromirror-Based Lissajous Scanning Displays

by Weiqi Du, Gaofei Zhang and Liangchen Ye

Sensors 2016, 16(5), 675; https://doi.org/10.3390/s16050675 - 11 May 2016

Cited by 10 | Viewed by 5434

Abstract

Micromirror-based scanning displays have been the focus of a variety of applications. Lissajous scanning displays have advantages in terms of power consumption; however, the image quality is not good enough. The main reason for this is the varying size and the contrast ratio [...] Read more.

Micromirror-based scanning displays have been the focus of a variety of applications. Lissajous scanning displays have advantages in terms of power consumption; however, the image quality is not good enough. The main reason for this is the varying size and the contrast ratio of pixels at different positions of the image. In this paper, the Lissajous scanning trajectory is analyzed and a new method based on the diamond pixel is introduced to Lissajous displays. The optical performance of micromirrors is discussed. A display system demonstrator is built, and tests of resolution and contrast ratio are conducted. The test results show that the new Lissajous scanning method can be used in displays by using diamond pixels and image quality remains stable at different positions. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Graphical abstract

15 pages, 5231 KiB

Open AccessArticle

Spectrum and Image Texture Features Analysis for Early Blight Disease Detection on Eggplant Leaves

by Chuanqi Xie and Yong He

Sensors 2016, 16(5), 676; https://doi.org/10.3390/s16050676 - 11 May 2016

Cited by 60 | Viewed by 9002

Abstract

This study investigated both spectrum and texture features for detecting early blight disease on eggplant leaves. Hyperspectral images for healthy and diseased samples were acquired covering the wavelengths from 380 to 1023 nm. Four gray images were identified according to the effective wavelengths [...] Read more.

This study investigated both spectrum and texture features for detecting early blight disease on eggplant leaves. Hyperspectral images for healthy and diseased samples were acquired covering the wavelengths from 380 to 1023 nm. Four gray images were identified according to the effective wavelengths (408, 535, 624 and 703 nm). Hyperspectral images were then converted into RGB, HSV and HLS images. Finally, eight texture features (mean, variance, homogeneity, contrast, dissimilarity, entropy, second moment and correlation) based on gray level co-occurrence matrix (GLCM) were extracted from gray images, RGB, HSV and HLS images, respectively. The dependent variables for healthy and diseased samples were set as 0 and 1. K-Nearest Neighbor (KNN) and AdaBoost classification models were established for detecting healthy and infected samples. All models obtained good results with the classification rates (CRs) over 88.46% in the testing sets. The results demonstrated that spectrum and texture features were effective for early blight disease detection on eggplant leaves. Full article

(This article belongs to the Special Issue Sensors for Agriculture)

► Show Figures

Figure 1

22 pages, 2219 KiB

Open AccessArticle

Carrying Position Independent User Heading Estimation for Indoor Pedestrian Navigation with Smartphones

by Zhi-An Deng, Guofeng Wang, Ying Hu and Yang Cui

Sensors 2016, 16(5), 677; https://doi.org/10.3390/s16050677 - 11 May 2016

Cited by 19 | Viewed by 5799

Abstract

This paper proposes a novel heading estimation approach for indoor pedestrian navigation using the built-in inertial sensors on a smartphone. Unlike previous approaches constraining the carrying position of a smartphone on the user’s body, our approach gives the user a larger freedom by [...] Read more.

This paper proposes a novel heading estimation approach for indoor pedestrian navigation using the built-in inertial sensors on a smartphone. Unlike previous approaches constraining the carrying position of a smartphone on the user’s body, our approach gives the user a larger freedom by implementing automatic recognition of the device carrying position and subsequent selection of an optimal strategy for heading estimation. We firstly predetermine the motion state by a decision tree using an accelerometer and a barometer. Then, to enable accurate and computational lightweight carrying position recognition, we combine a position classifier with a novel position transition detection algorithm, which may also be used to avoid the confusion between position transition and user turn during pedestrian walking. For a device placed in the trouser pockets or held in a swinging hand, the heading estimation is achieved by deploying a principal component analysis (PCA)-based approach. For a device held in the hand or against the ear during a phone call, user heading is directly estimated by adding the yaw angle of the device to the related heading offset. Experimental results show that our approach can automatically detect carrying positions with high accuracy, and outperforms previous heading estimation approaches in terms of accuracy and applicability. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2016)

► Show Figures

Figure 1

40 pages, 1195 KiB

Open AccessArticle

An in-Depth Survey of Visible Light Communication Based Positioning Systems

by Trong-Hop Do and Myungsik Yoo

Sensors 2016, 16(5), 678; https://doi.org/10.3390/s16050678 - 12 May 2016

Cited by 303 | Viewed by 18768

Abstract

While visible light communication (VLC) has become the candidate for the wireless technology of the 21st century due to its inherent advantages, VLC based positioning also has a great chance of becoming the standard approach to positioning. Within the last few years, many [...] Read more.

While visible light communication (VLC) has become the candidate for the wireless technology of the 21st century due to its inherent advantages, VLC based positioning also has a great chance of becoming the standard approach to positioning. Within the last few years, many studies on VLC based positioning have been published, but there are not many survey works in this field. In this paper, an in-depth survey of VLC based positioning systems is provided. More than 100 papers ranging from pioneering papers to the state-of-the-art in the field were collected and classified based on the positioning algorithms, the types of receivers, and the multiplexing techniques. In addition, current issues and research trends in VLC based positioning are discussed. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

10 pages, 3561 KiB

Open AccessArticle

Assessment of Aliasing Errors in Low-Degree Coefficients Inferred from GPS Data

by Na Wei and Rongxin Fang

Sensors 2016, 16(5), 679; https://doi.org/10.3390/s16050679 - 11 May 2016

Cited by 6 | Viewed by 3926

Abstract

With sparse and uneven site distribution, Global Positioning System (GPS) data is just barely able to infer low-degree coefficients in the surface mass field. The unresolved higher-degree coefficients turn out to introduce aliasing errors into the estimates of low-degree coefficients. To reduce the [...] Read more.

With sparse and uneven site distribution, Global Positioning System (GPS) data is just barely able to infer low-degree coefficients in the surface mass field. The unresolved higher-degree coefficients turn out to introduce aliasing errors into the estimates of low-degree coefficients. To reduce the aliasing errors, the optimal truncation degree should be employed. Using surface displacements simulated from loading models, we theoretically prove that the optimal truncation degree should be degree 6–7 for a GPS inversion and degree 20 for combing GPS and Ocean Bottom Pressure (OBP) with no additional regularization. The optimal truncation degree should be decreased to degree 4–5 for real GPS data. Additionally, we prove that a Scaled Sensitivity Matrix (SSM) approach can be used to quantify the aliasing errors due to any one or any combination of unresolved higher degrees, which is beneficial to identify the major error source from among all the unresolved higher degrees. Results show that the unresolved higher degrees lower than degree 20 are the major error source for global inversion. We also theoretically prove that the SSM approach can be used to mitigate the aliasing errors in a GPS inversion, if the neglected higher degrees are well known from other sources. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

9 pages, 7057 KiB

Open AccessArticle

Absolute Position Sensing Based on a Robust Differential Capacitive Sensor with a Grounded Shield Window

by Yang Bai, Yunfeng Lu, Pengcheng Hu, Gang Wang, Jinxin Xu, Tao Zeng, Zhengkun Li, Zhonghua Zhang and Jiubin Tan

Sensors 2016, 16(5), 680; https://doi.org/10.3390/s16050680 - 11 May 2016

Cited by 23 | Viewed by 6144

Abstract

A simple differential capacitive sensor is provided in this paper to measure the absolute positions of length measuring systems. By utilizing a shield window inside the differential capacitor, the measurement range and linearity range of the sensor can reach several millimeters. What is [...] Read more.

A simple differential capacitive sensor is provided in this paper to measure the absolute positions of length measuring systems. By utilizing a shield window inside the differential capacitor, the measurement range and linearity range of the sensor can reach several millimeters. What is more interesting is that this differential capacitive sensor is only sensitive to one translational degree of freedom (DOF) movement, and immune to the vibration along the other two translational DOFs. In the experiment, we used a novel circuit based on an AC capacitance bridge to directly measure the differential capacitance value. The experimental result shows that this differential capacitive sensor has a sensitivity of 2 × 10⁻⁴ pF/μm with 0.08 μm resolution. The measurement range of this differential capacitive sensor is 6 mm, and the linearity error are less than 0.01% over the whole absolute position measurement range. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Graphical abstract

10 pages, 2123 KiB

Open AccessArticle

Self-Mixing Demodulation for Coherent Phase-Sensitive OTDR System

by Haijun He, Li-Yang Shao, Zonglei Li, Zhiyong Zhang, Xihua Zou, Bin Luo, Wei Pan and Lianshan Yan

Sensors 2016, 16(5), 681; https://doi.org/10.3390/s16050681 - 12 May 2016

Cited by 47 | Viewed by 11587

Abstract

Phase-sensitive optical time domain reflectometry (Ф-OTDR) attracts much attention due to its capability of telling the type and position of an intrusion simultaneously. In recent decades, coherent Ф-OTDR has been demonstrated to realize long-distance detection. For coherent Ф-OTDR, there are three typical demodulation [...] Read more.

Phase-sensitive optical time domain reflectometry (Ф-OTDR) attracts much attention due to its capability of telling the type and position of an intrusion simultaneously. In recent decades, coherent Ф-OTDR has been demonstrated to realize long-distance detection. For coherent Ф-OTDR, there are three typical demodulation schemes in the reported studies. However, they still cannot realize real-time monitoring to satisfy practical demands. A simple and effective demodulation method based on self-mixing has been put forward to demodulate the beat signal in coherent Ф-OTDR. It not only saves a local electrical oscillator and frequency locked loop, but also demodulates the beat signal without residual frequency. Several vibrations with different frequency were separately applied at the same location of a 42.5 km fiber. The spatial resolution of 10 m and frequency response range from 8 Hz to 980 Hz have been achieved. The precise location with signal-to-noise ratio of 21.4 dB and broadband measurement demonstrate the self-mixing scheme can demodulate the coherent Ф-OTDR signal effectively. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

19 pages, 7375 KiB

Open AccessArticle

Coupled Integration of CSAC, MIMU, and GNSS for Improved PNT Performance

by Lin Ma, Zheng You, Tianyi Liu and Shuai Shi

Sensors 2016, 16(5), 682; https://doi.org/10.3390/s16050682 - 12 May 2016

Cited by 21 | Viewed by 5748

Abstract

Positioning, navigation, and timing (PNT) is a strategic key technology widely used in military and civilian applications. Global navigation satellite systems (GNSS) are the most important PNT techniques. However, the vulnerability of GNSS threatens PNT service quality, and integrations with other information are [...] Read more.

Positioning, navigation, and timing (PNT) is a strategic key technology widely used in military and civilian applications. Global navigation satellite systems (GNSS) are the most important PNT techniques. However, the vulnerability of GNSS threatens PNT service quality, and integrations with other information are necessary. A chip scale atomic clock (CSAC) provides high-precision frequency and high-accuracy time information in a short time. A micro inertial measurement unit (MIMU) provides a strap-down inertial navigation system (SINS) with rich navigation information, better real-time feed, anti-jamming, and error accumulation. This study explores the coupled integration of CSAC, MIMU, and GNSS to enhance PNT performance. The architecture of coupled integration is designed and degraded when any subsystem fails. A mathematical model for a precise time aiding navigation filter is derived rigorously. The CSAC aids positioning by weighted linear optimization when the visible satellite number is four or larger. By contrast, CSAC converts the GNSS observations to range measurements by “clock coasting” when the visible satellite number is less than four, thereby constraining the error divergence of micro inertial navigation and improving the availability of GNSS signals and the positioning accuracy of the integration. Field vehicle experiments, both in open-sky area and in a harsh environment, show that the integration can improve the positioning probability and accuracy. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

19 pages, 5840 KiB

Open AccessArticle

Mobile Laser Scanning Systems for Measuring the Clearance Gauge of Railways: State of Play, Testing and Outlook

by Sławomir Mikrut, Piotr Kohut, Krystian Pyka, Regina Tokarczyk, Tomasz Barszcz and Tadeusz Uhl

Sensors 2016, 16(5), 683; https://doi.org/10.3390/s16050683 - 12 May 2016

Cited by 37 | Viewed by 7792

Abstract

The paper contains a survey of mobile scanning systems for measuring the railway clearance gauge. The research was completed as part of the project carried out for the PKP (PKP Polish Railway Lines S.A., Warsaw, Poland) in 2011–2013. The authors conducted experiments, including [...] Read more.

The paper contains a survey of mobile scanning systems for measuring the railway clearance gauge. The research was completed as part of the project carried out for the PKP (PKP Polish Railway Lines S.A., Warsaw, Poland) in 2011–2013. The authors conducted experiments, including a search for the latest solutions relating to mobile measurement systems that meet the basic requirement. At the very least, these solutions needed to be accurate and have the ability for quick retrieval of data. In the paper, specifications and the characteristics of the component devices of the scanning systems are described. Based on experiments, the authors did some examination of the selected mobile systems to be applied for measuring the clearance gauge. The Riegl (VMX-250) and Z+F (Zoller + Fröhlich) Solution were tested. Additional test measurements were carried out within a 30-kilometer section of the Warsaw-Kraków route. These measurements were designed so as to provide various elements of the railway infrastructure, the track geometry and the installed geodetic control network. This ultimately made it possible to reduce the time for the preparation of geodetic reference measurements for the testing of the accuracy of the selected systems. Reference measurements included the use of the polar method to select profiles perpendicular to the axis of the track. In addition, the coordinates selected were well defined as measuring points of the objects of the infrastructure of the clearance gauge. All of the tested systems meet the accuracy requirements initially established (within the range of 2 cm as required by the PKP). The tested systems have shown their advantages and disadvantages. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

26 pages, 4310 KiB

Open AccessArticle

Communication Range Dynamics and Performance Analysis for a Self-Adaptive Transmission Power Controller

by Néstor Lucas Martínez, José-Fernán Martínez Ortega, Vicente Hernández Díaz and Raúl M. Del Toro Matamoros

Sensors 2016, 16(5), 684; https://doi.org/10.3390/s16050684 - 12 May 2016

Cited by 1 | Viewed by 5182

Abstract

The deployment of the nodes in a Wireless Sensor and Actuator Network (WSAN) is typically restricted by the sensing and acting coverage. This implies that the locations of the nodes may be, and usually are, not optimal from the point of view of [...] Read more.

The deployment of the nodes in a Wireless Sensor and Actuator Network (WSAN) is typically restricted by the sensing and acting coverage. This implies that the locations of the nodes may be, and usually are, not optimal from the point of view of the radio communication. Additionally, when the transmission power is tuned for those locations, there are other unpredictable factors that can cause connectivity failures, like interferences, signal fading due to passing objects and, of course, radio irregularities. A control-based self-adaptive system is a typical solution to improve the energy consumption while keeping good connectivity. In this paper, we explore how the communication range for each node evolves along the iterations of an energy saving self-adaptive transmission power controller when using different parameter sets in an outdoor scenario, providing a WSAN that automatically adapts to surrounding changes keeping good connectivity. The results obtained in this paper show how the parameters with the best performance keep a k-connected network, where k is in the range of the desired node degree plus or minus a specified tolerance value. Full article

(This article belongs to the Special Issue Selected Papers from the 2nd International Electronic Conference on Sensors and Applications)

► Show Figures

Graphical abstract

13 pages, 8105 KiB

Open AccessArticle

An Energy Saving System for a Beam Pumping Unit

by Hongqiang Lv, Jun Liu, Jiuqiang Han and An Jiang

Sensors 2016, 16(5), 685; https://doi.org/10.3390/s16050685 - 13 May 2016

Cited by 31 | Viewed by 8260

Abstract

Beam pumping units are widely used in the oil production industry, but the energy efficiency of this artificial lift machinery is generally low, especially for the low-production well and high-production well in the later stage. There are a number of ways for energy [...] Read more.

Beam pumping units are widely used in the oil production industry, but the energy efficiency of this artificial lift machinery is generally low, especially for the low-production well and high-production well in the later stage. There are a number of ways for energy savings in pumping units, with the periodic adjustment of stroke speed and rectification of balance deviation being two important methods. In the paper, an energy saving system for a beam pumping unit (ESS-BPU) based on the Internet of Things (IoT) was proposed. A total of four types of sensors, including load sensor, angle sensor, voltage sensor, and current sensor, were used to detect the operating conditions of the pumping unit. Data from these sensors was fed into a controller installed in an oilfield to adjust the stroke speed automatically and estimate the degree of balance in real-time. Additionally, remote supervision could be fulfilled using a browser on a computer or smartphone. Furthermore, the data from a practical application was recorded and analyzed, and it can be seen that ESS-BPU is helpful in reducing energy loss caused by unnecessarily high stroke speed and a poor degree of balance. Full article

(This article belongs to the Special Issue Data in the IoT: from Sensing to Meaning)

► Show Figures

Figure 1

23 pages, 1207 KiB

Open AccessArticle

Wireless Sensor Array Network DoA Estimation from Compressed Array Data via Joint Sparse Representation

by Kai Yu, Ming Yin, Ji-An Luo, Yingguan Wang, Ming Bao, Yu-Hen Hu and Zhi Wang

Sensors 2016, 16(5), 686; https://doi.org/10.3390/s16050686 - 23 May 2016

Cited by 8 | Viewed by 6317

Abstract

A compressive sensing joint sparse representation direction of arrival estimation (CSJSR-DoA) approach is proposed for wireless sensor array networks (WSAN). By exploiting the joint spatial and spectral correlations of acoustic sensor array data, the CSJSR-DoA approach provides reliable DoA estimation using randomly-sampled acoustic [...] Read more.

A compressive sensing joint sparse representation direction of arrival estimation (CSJSR-DoA) approach is proposed for wireless sensor array networks (WSAN). By exploiting the joint spatial and spectral correlations of acoustic sensor array data, the CSJSR-DoA approach provides reliable DoA estimation using randomly-sampled acoustic sensor data. Since random sampling is performed at remote sensor arrays, less data need to be transmitted over lossy wireless channels to the fusion center (FC), and the expensive source coding operation at sensor nodes can be avoided. To investigate the spatial sparsity, an upper bound of the coherence of incoming sensor signals is derived assuming a linear sensor array configuration. This bound provides a theoretical constraint on the angular separation of acoustic sources to ensure the spatial sparsity of the received acoustic sensor array signals. The Cram

\overset{´}{e}

r–Rao bound of the CSJSR-DoA estimator that quantifies the theoretical DoA estimation performance is also derived. The potential performance of the CSJSR-DoA approach is validated using both simulations and field experiments on a prototype WSAN platform. Compared to existing compressive sensing-based DoA estimation methods, the CSJSR-DoA approach shows significant performance improvement. Full article

(This article belongs to the Special Issue Advances in Multi-Sensor Information Fusion: Theory and Applications)

► Show Figures

Figure 1

14 pages, 3570 KiB

Open AccessArticle

Retrieving Land Surface Temperature from Hyperspectral Thermal Infrared Data Using a Multi-Channel Method

by Xinke Zhong, Xing Huo, Chao Ren, Jelila Labed and Zhao-Liang Li

Sensors 2016, 16(5), 687; https://doi.org/10.3390/s16050687 - 13 May 2016

Cited by 12 | Viewed by 5303

Abstract

Land Surface Temperature (LST) is a key parameter in climate systems. The methods for retrieving LST from hyperspectral thermal infrared data either require accurate atmospheric profile data or require thousands of continuous channels. We aim to retrieve LST for natural land surfaces from [...] Read more.

Land Surface Temperature (LST) is a key parameter in climate systems. The methods for retrieving LST from hyperspectral thermal infrared data either require accurate atmospheric profile data or require thousands of continuous channels. We aim to retrieve LST for natural land surfaces from hyperspectral thermal infrared data using an adapted multi-channel method taking Land Surface Emissivity (LSE) properly into consideration. In the adapted method, LST can be retrieved by a linear function of 36 brightness temperatures at Top of Atmosphere (TOA) using channels where LSE has high values. We evaluated the adapted method using simulation data at nadir and satellite data near nadir. The Root Mean Square Error (RMSE) of the LST retrieved from the simulation data is 0.90 K. Compared with an LST product from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on Meteosat, the error in the LST retrieved from the Infared Atmospheric Sounding Interferometer (IASI) is approximately 1.6 K. The adapted method can be used for the near-real-time production of an LST product and to provide the physical method to simultaneously retrieve atmospheric profiles, LST, and LSE with a first-guess LST value. The limitations of the adapted method are that it requires the minimum LSE in the spectral interval of 800–950 cm⁻¹ larger than 0.95 and it has not been extended for off-nadir measurements. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

17 pages, 7706 KiB

Open AccessArticle

Particle and Photon Detection: Counting and Energy Measurement

by James Janesick and John Tower

Sensors 2016, 16(5), 688; https://doi.org/10.3390/s16050688 - 12 May 2016

Cited by 9 | Viewed by 9667

Abstract

Fundamental limits for photon counting and photon energy measurement are reviewed for CCD and CMOS imagers. The challenges to extend photon counting into the visible/nIR wavelengths and achieve energy measurement in the UV with specific read noise requirements are discussed. Pixel flicker and [...] Read more.

Fundamental limits for photon counting and photon energy measurement are reviewed for CCD and CMOS imagers. The challenges to extend photon counting into the visible/nIR wavelengths and achieve energy measurement in the UV with specific read noise requirements are discussed. Pixel flicker and random telegraph noise sources are highlighted along with various methods used in reducing their contribution on the sensor’s read noise floor. Practical requirements for quantum efficiency, charge collection efficiency, and charge transfer efficiency that interfere with photon counting performance are discussed. Lastly we will review current efforts in reducing flicker noise head-on, in hopes to drive read noise substantially below 1 carrier rms. Full article

(This article belongs to the Special Issue Photon-Counting Image Sensors)

► Show Figures

Graphical abstract

24 pages, 5736 KiB

Open AccessArticle

Comprehensive Comparisons of Satellite Data, Signals, and Measurements between the BeiDou Navigation Satellite System and the Global Positioning System

by Shau-Shiun Jan and An-Lin Tao

Sensors 2016, 16(5), 689; https://doi.org/10.3390/s16050689 - 13 May 2016

Cited by 18 | Viewed by 7513

Abstract

The Chinese BeiDou navigation satellite system (BDS) aims to provide global positioning service by 2020. The combined use of BDS and Global Positioning System (GPS) is proposed to provide navigation service with more stringent requirements. Actual satellite data, signals and measurements were collected [...] Read more.

The Chinese BeiDou navigation satellite system (BDS) aims to provide global positioning service by 2020. The combined use of BDS and Global Positioning System (GPS) is proposed to provide navigation service with more stringent requirements. Actual satellite data, signals and measurements were collected for more than one month to analyze the positioning service qualities from both BDS and GPS. In addition to the conversions of coordinate and timing system, five data quality analysis (DQA) methods, three signal quality analysis (SQA) methods, and four measurement quality analysis (MQA) methods are proposed in this paper to improve the integrated positioning performance of BDS and GPS. As shown in the experiment results, issues related to BDS and GPS are resolved by the above proposed quality analysis methods. Thus, the anomalies in satellite data, signals and measurements can be detected by following the suggested resolutions to enhance the positioning performance of the combined use of BDS and GPS in the Asia Pacific region. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

16 pages, 2436 KiB

Open AccessArticle

Wind Tunnel Analysis of the Airflow through Insect-Proof Screens and Comparison of Their Effect When Installed in a Mediterranean Greenhouse

by Alejandro López, Francisco D. Molina-Aiz, Diego L. Valera and Araceli Peña

Sensors 2016, 16(5), 690; https://doi.org/10.3390/s16050690 - 12 May 2016

Cited by 19 | Viewed by 6543

Abstract

The present work studies the effect of three insect-proof screens with different geometrical and aerodynamic characteristics on the air velocity and temperature inside a Mediterranean multi-span greenhouse with three roof vents and without crops, divided into two independent sectors. First, the insect-proof screens [...] Read more.

The present work studies the effect of three insect-proof screens with different geometrical and aerodynamic characteristics on the air velocity and temperature inside a Mediterranean multi-span greenhouse with three roof vents and without crops, divided into two independent sectors. First, the insect-proof screens were characterised geometrically by analysing digital images and testing in a low velocity wind tunnel. The wind tunnel tests gave screen discharge coefficient values of C_d,φ of 0.207 for screen 1 (10 × 20 threads·cm⁻²; porosity φ = 35.0%), 0.151 for screen 2 (13 × 30 threads·cm⁻²; φ = 26.3%) and 0.325 for screen 3 (10 × 20 threads·cm⁻²; porosity φ = 36.0%), at an air velocity of 0.25 m·s⁻¹. Secondly, when screens were installed in the greenhouse, we observed a statistical proportionality between the discharge coefficient at the openings and the air velocity u_i measured in the centre of the greenhouse, u_i = 0.856 C_d + 0.062 (R² = 0.68 and p-value = 0.012). The inside-outside temperature difference ΔT_io diminishes when the inside velocity increases following the statistically significant relationship ΔT_io = (−135.85 + 57.88/u_i)^0.5 (R² = 0.85 and p-value = 0.0011). Different thread diameters and tension affects the screen thickness, and means that similar porosities may well be associated with very different aerodynamic characteristics. Screens must be characterised by a theoretical function C_d,φ = [(2eμ/K_pρ)·(1/u_s) + (2eY/K_p^0.5)]^−0.5 that relates the discharge coefficient of the screen C_d,φ with the air velocity u_s. This relationship depends on the three parameters that define the aerodynamic behaviour of porous medium: permeability K_p, inertial factor Y and screen thickness e (and on air temperature that determine its density ρ and viscosity μ). However, for a determined temperature of air, the pressure drop-velocity relationship can be characterised only with two parameters: ΔP = au_s² + bu_s. Full article

(This article belongs to the Special Issue Sensors for Agriculture)

► Show Figures

Figure 1

9 pages, 4695 KiB

Open AccessArticle

Planar Position Sensor Based on Mono Sensing Electrode and Hybrid-Frequency Excitation

by Hongxiang Yu, Yu Zhang, Mengfeng Shen, Hongli Zhang, Zhao Gao and Dongyun Wang

Sensors 2016, 16(5), 691; https://doi.org/10.3390/s16050691 - 13 May 2016

Cited by 6 | Viewed by 4515

Abstract

A new way of measuring planar position for micrometric and sub-micrometric applications is presented with a mono sensing electrode and hybrid-frequency excitation. The sensing theory and operation principle are described and summarized, and a printed circuit board (PCB) sensor prototype is built and [...] Read more.

A new way of measuring planar position for micrometric and sub-micrometric applications is presented with a mono sensing electrode and hybrid-frequency excitation. The sensing theory and operation principle are described and summarized, and a printed circuit board (PCB) sensor prototype is built and tested. It is shown by the experimental results that a very simple structure and geometric relationship are achieved. Meanwhile, displacement sensitivity on an order of 1.50 mV per micron and measurement repeatability better than 0.002 mm are easily fulfilled for a square zone of 256 mm², making it a valuable alternative measurement device candidate for flexible and low-cost planar position detection. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

16 pages, 1957 KiB

Open AccessArticle

A Nonlinear Framework of Delayed Particle Smoothing Method for Vehicle Localization under Non-Gaussian Environment

by Zhu Xiao, Vincent Havyarimana, Tong Li and Dong Wang

Sensors 2016, 16(5), 692; https://doi.org/10.3390/s16050692 - 13 May 2016

Cited by 22 | Viewed by 5783

Abstract

In this paper, a novel nonlinear framework of smoothing method, non-Gaussian delayed particle smoother (nGDPS), is proposed, which enables vehicle state estimation (VSE) with high accuracy taking into account the non-Gaussianity of the measurement and process noises. Within the proposed method, the multivariate [...] Read more.

In this paper, a novel nonlinear framework of smoothing method, non-Gaussian delayed particle smoother (nGDPS), is proposed, which enables vehicle state estimation (VSE) with high accuracy taking into account the non-Gaussianity of the measurement and process noises. Within the proposed method, the multivariate Student’s t-distribution is adopted in order to compute the probability distribution function (PDF) related to the process and measurement noises, which are assumed to be non-Gaussian distributed. A computation approach based on Ensemble Kalman Filter (EnKF) is designed to cope with the mean and the covariance matrix of the proposal non-Gaussian distribution. A delayed Gibbs sampling algorithm, which incorporates smoothing of the sampled trajectories over a fixed-delay, is proposed to deal with the sample degeneracy of particles. The performance is investigated based on the real-world data, which is collected by low-cost on-board vehicle sensors. The comparison study based on the real-world experiments and the statistical analysis demonstrates that the proposed nGDPS has significant improvement on the vehicle state accuracy and outperforms the existing filtering and smoothing methods. Full article

(This article belongs to the Special Issue Scalable Localization in Wireless Sensor Networks)

► Show Figures

Figure 1

13 pages, 3135 KiB

Open AccessArticle

The Real-Valued Sparse Direction of Arrival (DOA) Estimation Based on the Khatri-Rao Product

by Tao Chen, Huanxin Wu and Zhongkai Zhao

Sensors 2016, 16(5), 693; https://doi.org/10.3390/s16050693 - 14 May 2016

Cited by 13 | Viewed by 5087

Abstract

There is a problem that complex operation which leads to a heavy calculation burden is required when the direction of arrival (DOA) of a sparse signal is estimated by using the array covariance matrix. The solution of the multiple measurement vectors (MMV) model [...] Read more.

There is a problem that complex operation which leads to a heavy calculation burden is required when the direction of arrival (DOA) of a sparse signal is estimated by using the array covariance matrix. The solution of the multiple measurement vectors (MMV) model is difficult. In this paper, a real-valued sparse DOA estimation algorithm based on the Khatri-Rao (KR) product called the L₁-RVSKR is proposed. The proposed algorithm is based on the sparse representation of the array covariance matrix. The array covariance matrix is transformed to a real-valued matrix via a unitary transformation so that a real-valued sparse model is achieved. The real-valued sparse model is vectorized for transforming to a single measurement vector (SMV) model, and a new virtual overcomplete dictionary is constructed according to the KR product’s property. Finally, the sparse DOA estimation is solved by utilizing the idea of a sparse representation of array covariance vectors (SRACV). The simulation results demonstrate the superior performance and the low computational complexity of the proposed algorithm. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

26 pages, 3453 KiB

Open AccessArticle

Current Developments on Optical Feedback Interferometry as an All-Optical Sensor for Biomedical Applications

by Julien Perchoux, Adam Quotb, Reza Atashkhooei, Francisco J. Azcona, Evelio E. Ramírez-Miquet, Olivier Bernal, Ajit Jha, Antonio Luna-Arriaga, Carlos Yanez, Jesus Caum, Thierry Bosch and Santiago Royo

Sensors 2016, 16(5), 694; https://doi.org/10.3390/s16050694 - 13 May 2016

Cited by 46 | Viewed by 8567

Abstract

Optical feedback interferometry (OFI) sensors are experiencing a consistent increase in their applications to biosensing due to their contactless nature, low cost and compactness, features that fit very well with current biophotonics research and market trends. The present paper is a review of [...] Read more.

Optical feedback interferometry (OFI) sensors are experiencing a consistent increase in their applications to biosensing due to their contactless nature, low cost and compactness, features that fit very well with current biophotonics research and market trends. The present paper is a review of the work in progress at UPC-CD6 and LAAS-CNRS related to the application of OFI to different aspects of biosensing, both in vivo and ex vivo. This work is intended to present the variety of opportunities and potential applications related to OFI that are available in the field. The activities presented are divided into two main sensing strategies: The measurement of optical path changes and the monitoring of flows, which correspond to sensing strategies linked to the reconstruction of changes of amplitude from the interferometric signal, and to classical Doppler frequency measurements, respectively. For optical path change measurements, measurements of transient pulses, usual in biosensing, together with the measurement of large displacements applied to designing palliative care instrumentation for Parkinson disease are discussed. Regarding the Doppler-based approach, progress in flow-related signal processing and applications in real-time monitoring of non-steady flows, human blood flow monitoring and OFI pressure myograph sensing will be presented. In all cases, experimental setups are discussed and results presented, showing the versatility of the technique. The described applications show the wide capabilities in biosensing of the OFI sensor, showing it as an enabler of low-cost, all-optical, high accuracy biomedical applications. Full article

(This article belongs to the Special Issue Infrared and THz Sensing and Imaging)

► Show Figures

Figure 1

12 pages, 2601 KiB

Open AccessArticle

Determination of Ignitable Liquids in Fire Debris: Direct Analysis by Electronic Nose

by Marta Ferreiro-González, Gerardo F. Barbero, Miguel Palma, Jesús Ayuso, José A. Álvarez and Carmelo G. Barroso

Sensors 2016, 16(5), 695; https://doi.org/10.3390/s16050695 - 13 May 2016

Cited by 37 | Viewed by 8121

Abstract

Arsonists usually use an accelerant in order to start or accelerate a fire. The most widely used analytical method to determine the presence of such accelerants consists of a pre-concentration step of the ignitable liquid residues followed by chromatographic analysis. A rapid analytical [...] Read more.

Arsonists usually use an accelerant in order to start or accelerate a fire. The most widely used analytical method to determine the presence of such accelerants consists of a pre-concentration step of the ignitable liquid residues followed by chromatographic analysis. A rapid analytical method based on headspace-mass spectrometry electronic nose (E-Nose) has been developed for the analysis of Ignitable Liquid Residues (ILRs). The working conditions for the E-Nose analytical procedure were optimized by studying different fire debris samples. The optimized experimental variables were related to headspace generation, specifically, incubation temperature and incubation time. The optimal conditions were 115 °C and 10 min for these two parameters. Chemometric tools such as hierarchical cluster analysis (HCA) and linear discriminant analysis (LDA) were applied to the MS data (45–200 m/z) to establish the most suitable spectroscopic signals for the discrimination of several ignitable liquids. The optimized method was applied to a set of fire debris samples. In order to simulate post-burn samples several ignitable liquids (gasoline, diesel, citronella, kerosene, paraffin) were used to ignite different substrates (wood, cotton, cork, paper and paperboard). A full discrimination was obtained on using discriminant analysis. This method reported here can be considered as a green technique for fire debris analyses. Full article

(This article belongs to the Special Issue Olfactory and Gustatory Sensors)

► Show Figures

Figure 1

15 pages, 417 KiB

Open AccessArticle

Stability-Aware Geographic Routing in Energy Harvesting Wireless Sensor Networks

by Tran Dinh Hieu, Le The Dung and Byung-Seo Kim

Sensors 2016, 16(5), 696; https://doi.org/10.3390/s16050696 - 14 May 2016

Cited by 42 | Viewed by 5581

Abstract

A new generation of wireless sensor networks that harvest energy from environmental sources such as solar, vibration, and thermoelectric to power sensor nodes is emerging to solve the problem of energy limitation. Based on the photo-voltaic model, this research proposes a stability-aware geographic [...] Read more.

A new generation of wireless sensor networks that harvest energy from environmental sources such as solar, vibration, and thermoelectric to power sensor nodes is emerging to solve the problem of energy limitation. Based on the photo-voltaic model, this research proposes a stability-aware geographic routing for reliable data transmissions in energy-harvesting wireless sensor networks (EH-WSNs) to provide a reliable routes selection method and potentially achieve an unlimited network lifetime. Specifically, the influences of link quality, represented by the estimated packet reception rate, on network performance is investigated. Simulation results show that the proposed method outperforms an energy-harvesting-aware method in terms of energy consumption, the average number of hops, and the packet delivery ratio. Full article

(This article belongs to the Section Sensor Networks)

► Show Figures

Graphical abstract

9 pages, 2221 KiB

Open AccessArticle

Measurement of Moisture in Wood for Application in the Restoration of Old Buildings

by Carlos Moron, Luisa Garcia-Fuentevilla, Alfonso Garcia and Alberto Moron

Sensors 2016, 16(5), 697; https://doi.org/10.3390/s16050697 - 14 May 2016

Cited by 33 | Viewed by 6592

Abstract

There are many historic buildings whose construction is based on timber frame walls. Most buildings built during the nineteenth and early twentieth centuries were based on timber frame walls with vertical support elements. These timber frame elements are affected by their moisture content [...] Read more.

There are many historic buildings whose construction is based on timber frame walls. Most buildings built during the nineteenth and early twentieth centuries were based on timber frame walls with vertical support elements. These timber frame elements are affected by their moisture content and by the passage of time. If the interaction of the timber frame walls with hygrothermal fluctuations were known, the maintenance of these buildings could be improved significantly. To determine the moisture content of wood there are two types of meters on the market: on the one hand, capacitance meters which consist of two side ends and where the moisture content is measured locally between two peaks. On the other hand, there are meters based on the variation of electromagnetic transmittance of timber, which depends on the moisture of timber. The second ones are very expensive and difficult to handle. This work presents a new non-intrusive capacitive sensor that measures the global moisture content in a section of the timber frame walls and therefore its accuracy is similar to the accuracy that can be obtained with electromagnetic transmittance meters. Additionally, as it is a capacitive sensor, it is low cost and easy to operate. Full article

(This article belongs to the Special Issue Selected Papers from the 2nd International Electronic Conference on Sensors and Applications)

► Show Figures

Figure 1

17 pages, 18115 KiB

Open AccessArticle

A Novel Method for Proximity Detection of Moving Targets Using a Large-Scale Planar Capacitive Sensor System

by Yong Ye, Jiahao Deng, Sanmin Shen, Zhuo Hou and Yuting Liu

Sensors 2016, 16(5), 699; https://doi.org/10.3390/s16050699 - 16 May 2016

Cited by 33 | Viewed by 9047

Abstract

A novel method for proximity detection of moving targets (with high dielectric constants) using a large-scale (the size of each sensor is 31 cm × 19 cm) planar capacitive sensor system (PCSS) is proposed. The capacitive variation with distance is derived, and a [...] Read more.

A novel method for proximity detection of moving targets (with high dielectric constants) using a large-scale (the size of each sensor is 31 cm × 19 cm) planar capacitive sensor system (PCSS) is proposed. The capacitive variation with distance is derived, and a pair of electrodes in a planar capacitive sensor unit (PCSU) with a spiral shape is found to have better performance on sensitivity distribution homogeneity and dynamic range than three other shapes (comb shape, rectangular shape, and circular shape). A driving excitation circuit with a Clapp oscillator is proposed, and a capacitance measuring circuit with sensitivity of 0.21

V_{p - p} / pF

is designed. The results of static experiments and dynamic experiments demonstrate that the voltage curves of static experiments are similar to those of dynamic experiments; therefore, the static data can be used to simulate the dynamic curves. The dynamic range of proximity detection for three projectiles is up to 60 cm, and the results of the following static experiments show that the PCSU with four neighboring units has the highest sensitivity (the sensitivities of other units are at least 4% lower); when the attack angle decreases, the intensity of sensor signal increases. This proposed method leads to the design of a feasible moving target detector with simple structure and low cost, which can be applied in the interception system. Full article

(This article belongs to the Special Issue Non-Contact Sensing)

► Show Figures

Figure 1

19 pages, 4191 KiB

Open AccessArticle

Extracting Objects for Aerial Manipulation on UAVs Using Low Cost Stereo Sensors

by Pablo Ramon Soria, Robert Bevec, Begoña C. Arrue, Aleš Ude and Aníbal Ollero

Sensors 2016, 16(5), 700; https://doi.org/10.3390/s16050700 - 14 May 2016

Cited by 23 | Viewed by 8371

Abstract

Giving unmanned aerial vehicles (UAVs) the possibility to manipulate objects vastly extends the range of possible applications. This applies to rotary wing UAVs in particular, where their capability of hovering enables a suitable position for in-flight manipulation. Their manipulation skills must be suitable [...] Read more.

Giving unmanned aerial vehicles (UAVs) the possibility to manipulate objects vastly extends the range of possible applications. This applies to rotary wing UAVs in particular, where their capability of hovering enables a suitable position for in-flight manipulation. Their manipulation skills must be suitable for primarily natural, partially known environments, where UAVs mostly operate. We have developed an on-board object extraction method that calculates information necessary for autonomous grasping of objects, without the need to provide the model of the object’s shape. A local map of the work-zone is generated using depth information, where object candidates are extracted by detecting areas different to our floor model. Their image projections are then evaluated using support vector machine (SVM) classification to recognize specific objects or reject bad candidates. Our method builds a sparse cloud representation of each object and calculates the object’s centroid and the dominant axis. This information is then passed to a grasping module. Our method works under the assumption that objects are static and not clustered, have visual features and the floor shape of the work-zone area is known. We used low cost cameras for creating depth information that cause noisy point clouds, but our method has proved robust enough to process this data and return accurate results. Full article

(This article belongs to the Special Issue Imaging: Sensors and Technologies)

► Show Figures

Figure 1

12 pages, 2297 KiB

Open AccessArticle

Influences of Probe’s Morphology for Metal Ion Detection Based on Light-Addressable Potentiometric Sensors

by Chen Shao, Shuang Zhou, Xuebo Yin, Yajun Gu and Yunfang Jia

Sensors 2016, 16(5), 701; https://doi.org/10.3390/s16050701 - 14 May 2016

Cited by 11 | Viewed by 5116

Abstract

The sensing mechanism of binding Hg²⁺ into thymine-thymine (T-T) mismatched base pairs was introduced into a light-addressable potentiometric sensor (LAPS) with anti-Hg²⁺ aptamer as the sensing units. Three kinds of T-rich single-strand DNA (ssDNA) chains with different spacer lengths, from 0 [...] Read more.

The sensing mechanism of binding Hg²⁺ into thymine-thymine (T-T) mismatched base pairs was introduced into a light-addressable potentiometric sensor (LAPS) with anti-Hg²⁺ aptamer as the sensing units. Three kinds of T-rich single-strand DNA (ssDNA) chains with different spacer lengths, from 0 to 12 –CH₂ groups, were designed to investigate surface charge and morphological effects on the LAPS’ output. First, by comparing the responding of LAPS modified with three kinds of ssDNA, it was found that the best performance for Hg²⁺ sensing was exhibited by the probe without –CH₂ groups. The detection limit of Hg²⁺ ion was 1 ppt under the optimal condition. Second, the cooperative effects of surface charge and morphology on the output were observed by the controlled experiments. The two effects were the negative charge balanced by metal cations and the morphological changing caused by the formation of T-Hg²⁺-T structure. In conclusion, not only the influences of the aptamer probe’s morphology and surface charge was investigated on the platform of LAPS, but also sensing Hg²⁺ ions was achieved for the first time by the presented aptamer LAPS. Full article

(This article belongs to the Section Chemical Sensors)

► Show Figures

Figure 1

25 pages, 7781 KiB

Open AccessArticle

Methods and Best Practice to Intercompare Dissolved Oxygen Sensors and Fluorometers/Turbidimeters for Oceanographic Applications

by Sara Pensieri, Roberto Bozzano, M. Elisabetta Schiano, Manolis Ntoumas, Emmanouil Potiris, Constantin Frangoulis, Dimitrios Podaras and George Petihakis

Sensors 2016, 16(5), 702; https://doi.org/10.3390/s16050702 - 17 May 2016

Cited by 10 | Viewed by 9328

Abstract

In European seas, ocean monitoring strategies in terms of key parameters, space and time scale vary widely for a range of technical and economic reasons. Nonetheless, the growing interest in the ocean interior promotes the investigation of processes such as oxygen consumption, primary [...] Read more.

In European seas, ocean monitoring strategies in terms of key parameters, space and time scale vary widely for a range of technical and economic reasons. Nonetheless, the growing interest in the ocean interior promotes the investigation of processes such as oxygen consumption, primary productivity and ocean acidity requiring that close attention is paid to the instruments in terms of measurement setup, configuration, calibration, maintenance procedures and quality assessment. To this aim, two separate hardware and software tools were developed in order to test and simultaneously intercompare several oxygen probes and fluorometers/turbidimeters, respectively in the same environmental conditions, with a configuration as close as possible to real in-situ deployment. The chamber designed to perform chlorophyll-a and turbidity tests allowed for the simultaneous acquisition of analogue and digital signals of several sensors at the same time, so it was sufficiently compact to be used in both laboratory and onboard vessels. Methodologies and best practice committed to the intercomparison of dissolved oxygen sensors and fluorometers/turbidimeters have been used, which aid in the promotion of interoperability to access key infrastructures, such as ocean observatories and calibration facilities. Results from laboratory tests as well as field tests in the Mediterranean Sea are presented. Full article

(This article belongs to the Special Issue Sensors for Environmental Monitoring 2016)

► Show Figures

Graphical abstract

8 pages, 3516 KiB

Open AccessArticle

Anchoring of FRET Sensors—A Requirement for Spatiotemporal Resolution

by Elena V. Ivanova, Ricardo A. Figueroa, Tom Gatsinzi, Einar Hallberg and Kerstin Iverfeldt

Sensors 2016, 16(5), 703; https://doi.org/10.3390/s16050703 - 16 May 2016

Cited by 3 | Viewed by 5610

Abstract

FRET biosensors have become a routine tool for investigating mechanisms and components of cell signaling. Strategies for improving them for particular applications are continuously sought. One important aspect to consider when designing FRET probes is the dynamic distribution and propagation of signals within [...] Read more.

FRET biosensors have become a routine tool for investigating mechanisms and components of cell signaling. Strategies for improving them for particular applications are continuously sought. One important aspect to consider when designing FRET probes is the dynamic distribution and propagation of signals within living cells. We have addressed this issue by directly comparing an anchored (taFS) to a non-anchored (naFS) cleavable FRET sensor. We chose a microtubule-associated protein tau as an anchor, as microtubules are abundant throughout the cytosol of cells. We show that tau-anchored FRET sensors are concentrated at the cytoskeleton and enriched in the neurite-like processes of cells, providing high intensity of the total signal. In addition, anchoring limits the diffusion of the sensor, enabling spatiotemporally resolved monitoring of subcellular variations in enzyme activity. Thus, anchoring is an important aspect to consider when designing FRET sensors for deeper understanding of cell signaling. Full article

(This article belongs to the Special Issue FRET Biosensors)

► Show Figures

Graphical abstract

15 pages, 875 KiB

Open AccessArticle

Kinect-Based Virtual Game for the Elderly that Detects Incorrect Body Postures in Real Time

by Zelai Saenz-de-Urturi and Begonya Garcia-Zapirain Soto

Sensors 2016, 16(5), 704; https://doi.org/10.3390/s16050704 - 16 May 2016

Cited by 50 | Viewed by 9043

Abstract

Poor posture can result in loss of physical function, which is necessary to preserving independence in later life. Its decline is often the determining factor for loss of independence in the elderly. To avoid this, a system to correct poor posture in the [...] Read more.

Poor posture can result in loss of physical function, which is necessary to preserving independence in later life. Its decline is often the determining factor for loss of independence in the elderly. To avoid this, a system to correct poor posture in the elderly, designed for Kinect-based indoor applications, is proposed in this paper. Due to the importance of maintaining a healthy life style in senior citizens, the system has been integrated into a game which focuses on their physical stimulation. The game encourages users to perform physical activities while the posture correction system helps them to adopt proper posture. The system captures limb node data received from the Kinect sensor in order to detect posture variations in real time. The DTW algorithm compares the original posture with the current one to detect any deviation from the original correct position. The system was tested and achieved a successful detection percentage of 95.20%. Experimental tests performed in a nursing home with different users show the effectiveness of the proposed solution. Full article

(This article belongs to the Special Issue Sensors for Entertainment)

► Show Figures

Figure 1

21 pages, 2564 KiB

Open AccessArticle

Xurography as a Rapid Fabrication Alternative for Point-of-Care Devices: Assessment of Passive Micromixers

by J. Israel Martínez-López, Mauricio Mojica, Ciro A. Rodríguez and Héctor R. Siller

Sensors 2016, 16(5), 705; https://doi.org/10.3390/s16050705 - 16 May 2016

Cited by 47 | Viewed by 9976

Abstract

Despite the copious amount of research on the design and operation of micromixers, there are few works regarding manufacture technology aimed at implementation beyond academic environments. This work evaluates the viability of xurography as a rapid fabrication tool for the development of ultra-low [...] Read more.

Despite the copious amount of research on the design and operation of micromixers, there are few works regarding manufacture technology aimed at implementation beyond academic environments. This work evaluates the viability of xurography as a rapid fabrication tool for the development of ultra-low cost microfluidic technology for extreme Point-of-Care (POC) micromixing devices. By eschewing photolithographic processes and the bulkiness of pumping and enclosure systems for rapid fabrication and passively driven operation, xurography is introduced as a manufacturing alternative for asymmetric split and recombine (ASAR) micromixers. A T-micromixer design was used as a reference to assess the effects of different cutting conditions and materials on the geometric features of the resulting microdevices. Inspection by stereographic and confocal microscopy showed that it is possible to manufacture devices with less than 8% absolute dimensional error. Implementation of the manufacturing methodology in modified circular shape- based SAR microdevices (balanced and unbalanced configurations) showed that, despite the precision limitations of the xurographic process, it is possible to implement this methodology to produce functional micromixing devices. Mixing efficiency was evaluated numerically and experimentally at the outlet of the microdevices with performances up to 40%. Overall, the assessment encourages further research of xurography for the development of POC micromixers. Full article

(This article belongs to the Special Issue Microfluidics-Based Microsystem Integration Research)

► Show Figures

Graphical abstract

11 pages, 2574 KiB

Open AccessArticle

A Plasmonic Temperature-Sensing Structure Based on Dual Laterally Side-Coupled Hexagonal Cavities

by Yiyuan Xie, Yexiong Huang, Weihua Xu, Weilun Zhao and Chao He

Sensors 2016, 16(5), 706; https://doi.org/10.3390/s16050706 - 17 May 2016

Cited by 53 | Viewed by 6398

Abstract

A plasmonic temperature-sensing structure, based on a metal-insulator-metal (MIM) waveguide with dual side-coupled hexagonal cavities, is proposed and numerically investigated by using the finite-difference time-domain (FDTD) method in this paper. The numerical simulation results show that a resonance dip appears in the transmission [...] Read more.

A plasmonic temperature-sensing structure, based on a metal-insulator-metal (MIM) waveguide with dual side-coupled hexagonal cavities, is proposed and numerically investigated by using the finite-difference time-domain (FDTD) method in this paper. The numerical simulation results show that a resonance dip appears in the transmission spectrum. Moreover, the full width of half maximum (FWHM) of the resonance dip can be narrowed down, and the extinction ratio can reach a maximum value by tuning the coupling distance between the waveguide and two cavities. Based on a linear relationship between the resonance dip and environment temperature, the temperature-sensing characteristics are discussed. The temperature sensitivity is influenced by the side length and the coupling distance. Furthermore, for the first time, two concepts—optical spectrum interference (OSI) and misjudge rate (MR)—are introduced to study the temperature-sensing resolution based on spectral interrogation. This work has some significance in the design of nanoscale optical sensors with high temperature sensitivity and a high sensing resolution. Full article

(This article belongs to the Special Issue Resonator Sensors)

► Show Figures

Figure 1

20 pages, 6158 KiB

Open AccessArticle

A Low-Noise Transimpedance Amplifier for BLM-Based Ion Channel Recording

by Marco Crescentini, Marco Bennati, Shimul Chandra Saha, Josip Ivica, Maurits De Planque, Hywel Morgan and Marco Tartagni

Sensors 2016, 16(5), 709; https://doi.org/10.3390/s16050709 - 19 May 2016

Cited by 5 | Viewed by 11582

Abstract

High-throughput screening (HTS) using ion channel recording is a powerful drug discovery technique in pharmacology. Ion channel recording with planar bilayer lipid membranes (BLM) is scalable and has very high sensitivity. A HTS system based on BLM ion channel recording faces three main [...] Read more.

High-throughput screening (HTS) using ion channel recording is a powerful drug discovery technique in pharmacology. Ion channel recording with planar bilayer lipid membranes (BLM) is scalable and has very high sensitivity. A HTS system based on BLM ion channel recording faces three main challenges: (i) design of scalable microfluidic devices; (ii) design of compact ultra-low-noise transimpedance amplifiers able to detect currents in the pA range with bandwidth >10 kHz; (iii) design of compact, robust and scalable systems that integrate these two elements. This paper presents a low-noise transimpedance amplifier with integrated A/D conversion realized in CMOS 0.35 μm technology. The CMOS amplifier acquires currents in the range ±200 pA and ±20 nA, with 100 kHz bandwidth while dissipating 41 mW. An integrated digital offset compensation loop balances any voltage offsets from Ag/AgCl electrodes. The measured open-input input-referred noise current is as low as 4 fA/√Hz at ±200 pA range. The current amplifier is embedded in an integrated platform, together with a microfluidic device, for current recording from ion channels. Gramicidin-A, α-haemolysin and KcsA potassium channels have been used to prove both the platform and the current-to-digital converter. Full article

(This article belongs to the Section Biosensors)

► Show Figures

Figure 1

17 pages, 15406 KiB

Open AccessArticle

A Mobile and Low-Cost System for Environmental Monitoring: A Case Study

by Alejandro Velasco, Renato Ferrero, Filippo Gandino, Bartolomeo Montrucchio and Maurizio Rebaudengo

Sensors 2016, 16(5), 710; https://doi.org/10.3390/s16050710 - 17 May 2016

Cited by 49 | Viewed by 8422

Abstract

Northern Italy has one of the highest air pollution levels in the European Union. This paper describes a mobile wireless sensor network system intended to complement the already existing official air quality monitoring systems of the metropolitan town of Torino. The system is [...] Read more.

Northern Italy has one of the highest air pollution levels in the European Union. This paper describes a mobile wireless sensor network system intended to complement the already existing official air quality monitoring systems of the metropolitan town of Torino. The system is characterized by a high portability and low cost, in both acquisition and maintenance. The high portability of the system aims to improve the spatial distribution and resolution of the measurements from the official static monitoring stations. Commercial PM

_{10}

and O

_{3}

sensors were incorporated into the system and were subsequently tested in a controlled environment and in the field. The test in the field, performed in collaboration with the local environmental agency, revealed that the sensors can provide accurate data if properly calibrated and maintained. Further tests were carried out by mounting the system on bicycles in order to increase their mobility. Full article

(This article belongs to the Special Issue Sensors for Environmental Monitoring 2016)

► Show Figures

Graphical abstract

16 pages, 4947 KiB

Open AccessArticle

Self-Locking Avoidance and Stiffness Compensation of a Three-Axis Micromachined Electrostatically Suspended Accelerometer

by Yonggang Yin, Boqian Sun and Fengtian Han

Sensors 2016, 16(5), 711; https://doi.org/10.3390/s16050711 - 18 May 2016

Cited by 21 | Viewed by 6265

Abstract

A micromachined electrostatically-suspended accelerometer (MESA) is a kind of three-axis inertial sensor based on fully-contactless electrostatic suspension of the proof mass (PM). It has the potential to offer broad bandwidth, high sensitivity, wide dynamic range and, thus, would be perfectly suited for land [...] Read more.

A micromachined electrostatically-suspended accelerometer (MESA) is a kind of three-axis inertial sensor based on fully-contactless electrostatic suspension of the proof mass (PM). It has the potential to offer broad bandwidth, high sensitivity, wide dynamic range and, thus, would be perfectly suited for land seismic acquisition. Previous experiments showed that it is hard to lift up the PM successfully during initial levitation as the mass needs to be levitated simultaneously in all six degrees of freedom (DoFs). By analyzing the coupling electrostatic forces and torques between three lateral axes, it is found there exists a self-locking zone due to the cross-axis coupling effect. To minimize the cross-axis coupling and solve the initial levitation problem, this paper proposes an effective control scheme by delaying the operation of one lateral actuator. The experimental result demonstrates that the PM can be levitated up with six-DoF suspension operation at any initial position. We also propose a feed-forward compensation approach to minimize the negative stiffness effect inherent in electrostatic suspension. The experiment results demonstrate that a more broadband linear amplitude-frequency response and higher suspension stiffness can be achieved, which is crucial to maintain high vector fidelity for potential use as a three-component MEMS geophone. The preliminary performance tests of the three-axis linear accelerometer were conducted under normal atmospheric pressure and room temperature. The main results and noise analysis are presented. It is shown that vacuum packaging of the MEMS sensor is essential to extend the bandwidth and lower the noise floor, especially for low-noise seismic data acquisition. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2016)

► Show Figures

Figure 1

30 pages, 34833 KiB

Open AccessArticle

Tools to Perform Local Dense 3D Reconstruction of Shallow Water Seabed

by Loïca Avanthey, Laurent Beaudoin, Antoine Gademer and Michel Roux

Sensors 2016, 16(5), 712; https://doi.org/10.3390/s16050712 - 17 May 2016

Cited by 8 | Viewed by 5485

Abstract

Tasks such as distinguishing or identifying individual objects of interest require the production of dense local clouds at the scale of these individual objects of interest. Due to the physical and dynamic properties of an underwater environment, the usual dense matching algorithms must [...] Read more.

Tasks such as distinguishing or identifying individual objects of interest require the production of dense local clouds at the scale of these individual objects of interest. Due to the physical and dynamic properties of an underwater environment, the usual dense matching algorithms must be rethought in order to be adaptive. These properties also imply that the scene must be observed at close range. Classic robotized acquisition systems are oversized for local studies in shallow water while the systematic acquisition of data is not guaranteed with divers. We address these two major issues through a multidisciplinary approach. To efficiently acquire on-demand stereoscopic pairs using simple logistics in small areas of shallow water, we devised an agile light-weight dedicated system which is easy to reproduce. To densely match two views in a reliable way, we devised a reconstruction algorithm that automatically accounts for the dynamics, variability and light absorption of the underwater environment. Field experiments in the Mediterranean Sea were used to assess the results. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

13 pages, 3979 KiB

Open AccessArticle

Field-Based Optimal Placement of Antennas for Body-Worn Wireless Sensors

by Łukasz Januszkiewicz, Paolo Di Barba and Sławomir Hausman

Sensors 2016, 16(5), 713; https://doi.org/10.3390/s16050713 - 17 May 2016

Cited by 13 | Viewed by 6337

Abstract

We investigate a case of automated energy-budget-aware optimization of the physical position of nodes (sensors) in a Wireless Body Area Network (WBAN). This problem has not been presented in the literature yet, as opposed to antenna and routing optimization, which are relatively well-addressed. [...] Read more.

We investigate a case of automated energy-budget-aware optimization of the physical position of nodes (sensors) in a Wireless Body Area Network (WBAN). This problem has not been presented in the literature yet, as opposed to antenna and routing optimization, which are relatively well-addressed. In our research, which was inspired by a safety-critical application for firefighters, the sensor network consists of three nodes located on the human body. The nodes communicate over a radio link operating in the 2.4 GHz or 5.8 GHz ISM frequency band. Two sensors have a fixed location: one on the head (earlobe pulse oximetry) and one on the arm (with accelerometers, temperature and humidity sensors, and a GPS receiver), while the position of the third sensor can be adjusted within a predefined region on the wearer’s chest. The path loss between each node pair strongly depends on the location of the nodes and is difficult to predict without performing a full-wave electromagnetic simulation. Our optimization scheme employs evolutionary computing. The novelty of our approach lies not only in the formulation of the problem but also in linking a fully automated optimization procedure with an electromagnetic simulator and a simplified human body model. This combination turns out to be a computationally effective solution, which, depending on the initial placement, has a potential to improve performance of our example sensor network setup by up to about 20 dB with respect to the path loss between selected nodes. Full article

(This article belongs to the Special Issue Components of Mechatronics and Micro-Electro-Mechanical-Systems (MEMS) – Modeling and Design)

► Show Figures

Graphical abstract

13 pages, 4281 KiB

Open AccessArticle

Error Ellipsoid Analysis for the Diameter Measurement of Cylindroid Components Using a Laser Radar Measurement System

by Zhengchun Du, Zhaoyong Wu and Jianguo Yang

Sensors 2016, 16(5), 714; https://doi.org/10.3390/s16050714 - 19 May 2016

Cited by 12 | Viewed by 5409

Abstract

The use of three-dimensional (3D) data in the industrial measurement field is becoming increasingly popular because of the rapid development of laser scanning techniques based on the time-of-flight principle. However, the accuracy and uncertainty of these types of measurement methods are seldom investigated. [...] Read more.

The use of three-dimensional (3D) data in the industrial measurement field is becoming increasingly popular because of the rapid development of laser scanning techniques based on the time-of-flight principle. However, the accuracy and uncertainty of these types of measurement methods are seldom investigated. In this study, a mathematical uncertainty evaluation model for the diameter measurement of standard cylindroid components has been proposed and applied to a 3D laser radar measurement system (LRMS). First, a single-point error ellipsoid analysis for the LRMS was established. An error ellipsoid model and algorithm for diameter measurement of cylindroid components was then proposed based on the single-point error ellipsoid. Finally, four experiments were conducted using the LRMS to measure the diameter of a standard cylinder in the laboratory. The experimental results of the uncertainty evaluation consistently matched well with the predictions. The proposed uncertainty evaluation model for cylindrical diameters can provide a reliable method for actual measurements and support further accuracy improvement of the LRMS. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

18 pages, 7210 KiB

Open AccessArticle

Reduction of Motion Artifacts and Improvement of R Peak Detecting Accuracy Using Adjacent Non-Intrusive ECG Sensors

by Minho Choi, Jae Jin Jeong, Seung Hun Kim and Sang Woo Kim

Sensors 2016, 16(5), 715; https://doi.org/10.3390/s16050715 - 17 May 2016

Cited by 27 | Viewed by 7394

Abstract

Non-intrusive electrocardiogram (ECG) monitoring has many advantages: easy to measure and apply in daily life. However, motion noise in the measured signal is the major problem of non-intrusive measurement. This paper proposes a method to reduce the noise and to detect the R [...] Read more.

Non-intrusive electrocardiogram (ECG) monitoring has many advantages: easy to measure and apply in daily life. However, motion noise in the measured signal is the major problem of non-intrusive measurement. This paper proposes a method to reduce the noise and to detect the R peaks of ECG in a stable manner in a sitting arrangement using non-intrusive sensors. The method utilizes two capacitive ECG sensors (cECGs) to measure ECG, and another two cECGs located adjacent to the sensors for ECG are added to obtain the information on motion. Then, active noise cancellation technique and the motion information are used to reduce motion noise. To verify the proposed method, ECG was measured indoors and during driving, and the accuracy of the detected R peaks was compared. After applying the method, the sum of sensitivity and positive predictivity increased 8.39% on average and 26.26% maximally in the data. Based on the results, it was confirmed that the motion noise was reduced and that more reliable R peak positions could be obtained by the proposed method. The robustness of the new ECG measurement method will elicit benefits to various health care systems that require noninvasive heart rate or heart rate variability measurements. Full article

(This article belongs to the Special Issue Wearable Biomedical Sensors)

► Show Figures

Figure 1

24 pages, 11024 KiB

Open AccessArticle

Travel Mode Detection with Varying Smartphone Data Collection Frequencies

by Muhammad Awais Shafique and Eiji Hato

Sensors 2016, 16(5), 716; https://doi.org/10.3390/s16050716 - 18 May 2016

Cited by 60 | Viewed by 8846

Abstract

Smartphones are becoming increasingly popular day-by-day. Modern smartphones are more than just calling devices. They incorporate a number of high-end sensors that provide many new dimensions to smartphone experience. The use of smartphones, however, can be extended from the usual telecommunication field to [...] Read more.

Smartphones are becoming increasingly popular day-by-day. Modern smartphones are more than just calling devices. They incorporate a number of high-end sensors that provide many new dimensions to smartphone experience. The use of smartphones, however, can be extended from the usual telecommunication field to applications in other specialized fields including transportation. Sensors embedded in the smartphones like GPS, accelerometer and gyroscope can collect data passively, which in turn can be processed to infer the travel mode of the smartphone user. This will solve most of the shortcomings associated with conventional travel survey methods including biased response, no response, erroneous time recording, etc. The current study uses the sensors’ data collected by smartphones to extract nine features for classification. Variables including data frequency, moving window size and proportion of data to be used for training, are dealt with to achieve better results. Random forest is used to classify the smartphone data among six modes. An overall accuracy of 99.96% is achieved, with no mode less than 99.8% for data collected at 10 Hz frequency. The accuracy is observed to decrease with decrease in data frequency, but at the same time the computation time also decreases. Full article

(This article belongs to the Special Issue Data in the IoT: from Sensing to Meaning)

► Show Figures

Figure 1

22 pages, 4825 KiB

Open AccessArticle

Evaluation of MPEG-7-Based Audio Descriptors for Animal Voice Recognition over Wireless Acoustic Sensor Networks

by Joaquín Luque, Diego F. Larios, Enrique Personal, Julio Barbancho and Carlos León

Sensors 2016, 16(5), 717; https://doi.org/10.3390/s16050717 - 18 May 2016

Cited by 24 | Viewed by 7375

Abstract

Environmental audio monitoring is a huge area of interest for biologists all over the world. This is why some audio monitoring system have been proposed in the literature, which can be classified into two different approaches: acquirement and compression of all audio patterns [...] Read more.

Environmental audio monitoring is a huge area of interest for biologists all over the world. This is why some audio monitoring system have been proposed in the literature, which can be classified into two different approaches: acquirement and compression of all audio patterns in order to send them as raw data to a main server; or specific recognition systems based on audio patterns. The first approach presents the drawback of a high amount of information to be stored in a main server. Moreover, this information requires a considerable amount of effort to be analyzed. The second approach has the drawback of its lack of scalability when new patterns need to be detected. To overcome these limitations, this paper proposes an environmental Wireless Acoustic Sensor Network architecture focused on use of generic descriptors based on an MPEG-7 standard. These descriptors demonstrate it to be suitable to be used in the recognition of different patterns, allowing a high scalability. The proposed parameters have been tested to recognize different behaviors of two anuran species that live in Spanish natural parks; the Epidalea calamita and the Alytes obstetricans toads, demonstrating to have a high classification performance. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2015)

► Show Figures

Figure 1

11 pages, 3855 KiB

Open AccessArticle

A Tactile Sensor Using Piezoresistive Beams for Detection of the Coefficient of Static Friction

by Taiyu Okatani, Hidetoshi Takahashi, Kentaro Noda, Tomoyuki Takahata, Kiyoshi Matsumoto and Isao Shimoyama

Sensors 2016, 16(5), 718; https://doi.org/10.3390/s16050718 - 18 May 2016

Cited by 31 | Viewed by 8103

Abstract

This paper reports on a tactile sensor using piezoresistive beams for detection of the coefficient of static friction merely by pressing the sensor against an object. The sensor chip is composed of three pairs of piezoresistive beams arranged in parallel and embedded in [...] Read more.

This paper reports on a tactile sensor using piezoresistive beams for detection of the coefficient of static friction merely by pressing the sensor against an object. The sensor chip is composed of three pairs of piezoresistive beams arranged in parallel and embedded in an elastomer; this sensor is able to measure the vertical and lateral strains of the elastomer. The coefficient of static friction is estimated from the ratio of the fractional resistance changes corresponding to the sensing elements of vertical and lateral strains when the sensor is in contact with an object surface. We applied a normal force on the sensor surface through objects with coefficients of static friction ranging from 0.2 to 1.1. The fractional resistance changes corresponding to vertical and lateral strains were proportional to the applied force. Furthermore, the relationship between these responses changed according to the coefficients of static friction. The experimental result indicated the proposed sensor could determine the coefficient of static friction before a global slip occurs. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

26 pages, 4303 KiB

Open AccessArticle

Color Restoration of RGBN Multispectral Filter Array Sensor Images Based on Spectral Decomposition

by Chulhee Park and Moon Gi Kang

Sensors 2016, 16(5), 719; https://doi.org/10.3390/s16050719 - 18 May 2016

Cited by 39 | Viewed by 11444

Abstract

A multispectral filter array (MSFA) image sensor with red, green, blue and near-infrared (NIR) filters is useful for various imaging applications with the advantages that it obtains color information and NIR information simultaneously. Because the MSFA image sensor needs to acquire invisible band [...] Read more.

A multispectral filter array (MSFA) image sensor with red, green, blue and near-infrared (NIR) filters is useful for various imaging applications with the advantages that it obtains color information and NIR information simultaneously. Because the MSFA image sensor needs to acquire invisible band information, it is necessary to remove the IR cut-offfilter (IRCF). However, without the IRCF, the color of the image is desaturated by the interference of the additional NIR component of each RGB color channel. To overcome color degradation, a signal processing approach is required to restore natural color by removing the unwanted NIR contribution to the RGB color channels while the additional NIR information remains in the N channel. Thus, in this paper, we propose a color restoration method for an imaging system based on the MSFA image sensor with RGBN filters. To remove the unnecessary NIR component in each RGB color channel, spectral estimation and spectral decomposition are performed based on the spectral characteristics of the MSFA sensor. The proposed color restoration method estimates the spectral intensity in NIR band and recovers hue and color saturation by decomposing the visible band component and the NIR band component in each RGB color channel. The experimental results show that the proposed method effectively restores natural color and minimizes angular errors. Full article

(This article belongs to the Special Issue Imaging: Sensors and Technologies)

► Show Figures

Graphical abstract

12 pages, 1627 KiB

Open AccessCommunication

A Novel Two-Wire Fast Readout Approach for Suppressing Cable Crosstalk in a Tactile Resistive Sensor Array

by Jianfeng Wu, Yu Wang, Jianqing Li and Aiguo Song

Sensors 2016, 16(5), 720; https://doi.org/10.3390/s16050720 - 18 May 2016

Cited by 22 | Viewed by 6212

Abstract

For suppressing the crosstalk problem due to wire resistances and contacted resistances of the long flexible cables in tactile sensing systems, we present a novel two-wire fast readout approach for the two-dimensional resistive sensor array in shared row-column fashion. In the approach, two [...] Read more.

For suppressing the crosstalk problem due to wire resistances and contacted resistances of the long flexible cables in tactile sensing systems, we present a novel two-wire fast readout approach for the two-dimensional resistive sensor array in shared row-column fashion. In the approach, two wires are used for every driving electrode and every sampling electrode in the resistive sensor array. The approach with a high readout rate, though it requires a large number of wires and many sampling channels, solves the cable crosstalk problem. We also verified the approach’s performance with Multisim simulations and actual experiments. Full article

(This article belongs to the Special Issue Giant Magnetoresistive Sensors)

► Show Figures

Figure 1

16 pages, 971 KiB

Open AccessArticle

On Modeling Eavesdropping Attacks in Underwater Acoustic Sensor Networks

by Qiu Wang, Hong-Ning Dai, Xuran Li, Hao Wang and Hong Xiao

Sensors 2016, 16(5), 721; https://doi.org/10.3390/s16050721 - 18 May 2016

Cited by 33 | Viewed by 7116

Abstract

The security and privacy of underwater acoustic sensor networks has received extensive attention recently due to the proliferation of underwater activities. This paper proposes an analytical model to investigate the eavesdropping attacks in underwater acoustic sensor networks. Our analytical framework considers the impacts [...] Read more.

The security and privacy of underwater acoustic sensor networks has received extensive attention recently due to the proliferation of underwater activities. This paper proposes an analytical model to investigate the eavesdropping attacks in underwater acoustic sensor networks. Our analytical framework considers the impacts of various underwater acoustic channel conditions (such as the acoustic signal frequency, spreading factor and wind speed) and different hydrophones (isotropic hydrophones and array hydrophones) in terms of network nodes and eavesdroppers. We also conduct extensive simulations to evaluate the effectiveness and the accuracy of our proposed model. Empirical results show that our proposed model is quite accurate. In addition, our results also imply that the eavesdropping probability heavily depends on both the underwater acoustic channel conditions and the features of hydrophones. Full article

(This article belongs to the Special Issue Security and Privacy in Sensor Networks)

► Show Figures

Graphical abstract

11 pages, 233 KiB

Open AccessArticle

Matrix Completion Optimization for Localization in Wireless Sensor Networks for Intelligent IoT

by Thu L. N. Nguyen and Yoan Shin

Sensors 2016, 16(5), 722; https://doi.org/10.3390/s16050722 - 18 May 2016

Cited by 34 | Viewed by 6763

Abstract

Localization in wireless sensor networks (WSNs) is one of the primary functions of the intelligent Internet of Things (IoT) that offers automatically discoverable services, while the localization accuracy is a key issue to evaluate the quality of those services. In this paper, we [...] Read more.

Localization in wireless sensor networks (WSNs) is one of the primary functions of the intelligent Internet of Things (IoT) that offers automatically discoverable services, while the localization accuracy is a key issue to evaluate the quality of those services. In this paper, we develop a framework to solve the Euclidean distance matrix completion problem, which is an important technical problem for distance-based localization in WSNs. The sensor network localization problem is described as a low-rank dimensional Euclidean distance completion problem with known nodes. The task is to find the sensor locations through recovery of missing entries of a squared distance matrix when the dimension of the data is small compared to the number of data points. We solve a relaxation optimization problem using a modification of Newton’s method, where the cost function depends on the squared distance matrix. The solution obtained in our scheme achieves a lower complexity and can perform better if we use it as an initial guess for an interactive local search of other higher precision localization scheme. Simulation results show the effectiveness of our approach. Full article

(This article belongs to the Special Issue Intelligent Internet of Things (IoT) Networks)

► Show Figures

Figure 1

13 pages, 1233 KiB

Open AccessArticle

Olive Crown Porosity Measurement Based on Radiation Transmittance: An Assessment of Pruning Effect

by Francisco J. Castillo-Ruiz, Sergio Castro-Garcia, Gregorio L. Blanco-Roldan, Rafael R. Sola-Guirado and Jesus A. Gil-Ribes

Sensors 2016, 16(5), 723; https://doi.org/10.3390/s16050723 - 19 May 2016

Cited by 18 | Viewed by 5996

Abstract

Crown porosity influences radiation interception, air movement through the fruit orchard, spray penetration, and harvesting operation in fruit crops. The aim of the present study was to develop an accurate and reliable methodology based on transmitted radiation measurements to assess the porosity of [...] Read more.

Crown porosity influences radiation interception, air movement through the fruit orchard, spray penetration, and harvesting operation in fruit crops. The aim of the present study was to develop an accurate and reliable methodology based on transmitted radiation measurements to assess the porosity of traditional olive trees under different pruning treatments. Transmitted radiation was employed as an indirect method to measure crown porosity in two olive orchards of the Picual and Hojiblanca cultivars. Additionally, three different pruning treatments were considered to determine if the pruning system influences crown porosity. This study evaluated the accuracy and repeatability of four algorithms in measuring crown porosity under different solar zenith angles. From a 14° to 30° solar zenith angle, the selected algorithm produced an absolute error of less than 5% and a repeatability higher than 0.9. The described method and selected algorithm proved satisfactory in field results, making it possible to measure crown porosity at different solar zenith angles. However, pruning fresh weight did not show any relationship with crown porosity due to the great differences between removed branches. A robust and accurate algorithm was selected for crown porosity measurements in traditional olive trees, making it possible to discern between different pruning treatments. Full article

(This article belongs to the Special Issue Sensors for Agriculture)

► Show Figures

Figure 1

13 pages, 2941 KiB

Open AccessArticle

A Continuous Liquid-Level Sensor for Fuel Tanks Based on Surface Plasmon Resonance

by Antonio M. Pozo, Francisco Pérez-Ocón and Ovidio Rabaza

Sensors 2016, 16(5), 724; https://doi.org/10.3390/s16050724 - 19 May 2016

Cited by 32 | Viewed by 8480

Abstract

A standard problem in large tanks at oil refineries and petrol stations is that water and fuel usually occupy the same tank. This is undesirable and causes problems such as corrosion in the tanks. Normally, the water level in tanks is unknown, with [...] Read more.

A standard problem in large tanks at oil refineries and petrol stations is that water and fuel usually occupy the same tank. This is undesirable and causes problems such as corrosion in the tanks. Normally, the water level in tanks is unknown, with the problems that this entails. We propose herein a method based on surface plasmon resonance (SPR) to detect in real time the interfaces in a tank which can simultaneously contain water, gasoline (or diesel) and air. The plasmonic sensor is composed of a hemispherical glass prism, a magnesium fluoride layer, and a gold layer. We have optimized the structural parameters of the sensor from the theoretical modeling of the reflectance curve. The sensor detects water-fuel and fuel-air interfaces and measures the level of each liquid in real time. This sensor is recommended for inflammable liquids because inside the tank there are no electrical or electronic signals which could cause explosions. The sensor proposed has a sensitivity of between 1.2 and 3.5 RIU⁻¹ and a resolution of between 5.7 × 10⁻⁴ and 16.5 × 10⁻⁴ RIU. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2015)

► Show Figures

Figure 1

11 pages, 2945 KiB

Open AccessArticle

The Conceptual Design of a Mechatronic System to Handle Bedridden Elderly Individuals

by Silva Bruno, Machado José, Soares Filomena, Carvalho Vítor, Matos Demétrio and Bezerra Karolina

Sensors 2016, 16(5), 725; https://doi.org/10.3390/s16050725 - 19 May 2016

Cited by 13 | Viewed by 6163

Abstract

The ever-growing percentage of elderly people in developed countries have made Ambient Assisted Living (AAL) solutions an important subject to be explored and developed. The increase in geriatric care requests are overburdening specialized institutions that cannot cope with the demand for support. Patients [...] Read more.

The ever-growing percentage of elderly people in developed countries have made Ambient Assisted Living (AAL) solutions an important subject to be explored and developed. The increase in geriatric care requests are overburdening specialized institutions that cannot cope with the demand for support. Patients are forced to have to remain at their homes encumbering the spouse or close family members with the caregiver role. This caregiver is not always physically and technically apt to assist the bedridden person with his/her meals and hygiene/bath routine. Consequently, a solution to assist caregivers in these tasks is of the utmost importance. This paper presents an approach for supporting caregivers when moving and repositioning Bedridden Elderly Peoples (BEPs) in home settings by means of a mechatronic system inspired by industrial conveyers. The proposed solution is able to insert itself underneath the patient, due to its low-profile structural properties, and retrieve and reallocate him/her. Ideally, the proposed mechatronic system aims to promote autonomy by reducing handling complexity, alter the role of the caregiver from physically handler of the BEP to an operator/supervisor role, and lessen the amount of effort expended by caregivers and BEPs alike. Full article

(This article belongs to the Special Issue Advanced Robotics and Mechatronics Devices)

► Show Figures

Figure 1

14 pages, 5991 KiB

Open AccessArticle

Measuring Micro-Friction Torque in MEMS Gas Bearings

by Xudong Fang and Huan Liu

Sensors 2016, 16(5), 726; https://doi.org/10.3390/s16050726 - 18 May 2016

Cited by 7 | Viewed by 8151

Abstract

An in situ measurement of micro-friction torque in MEMS gas bearings, which has been a challenging research topic for years, is realized by a system designed in this paper. In the system, a high accuracy micro-force sensor and an electronically-driven table are designed, [...] Read more.

An in situ measurement of micro-friction torque in MEMS gas bearings, which has been a challenging research topic for years, is realized by a system designed in this paper. In the system, a high accuracy micro-force sensor and an electronically-driven table are designed, fabricated and utilized. With appropriate installation of the sensor and bearings on the table, the engine rotor can be driven to rotate with the sensor using a silicon lever beam. One end of the beam is fixed to the shaft of the gas bearing, while the other end is free and in contact with the sensor probe tip. When the sensor begins to rotate with the table, the beam is pushed by the sensor probe to rotate in the same direction. For the beam, the friction torque from the gas bearing is balanced by the torque induced by pushing force from the sensor probe. Thus, the friction torque can be calculated as a product of the pushing force measured by the sensor and the lever arm, which is defined as the distance from the sensor probe tip to the centerline of the bearing. Experimental results demonstrate the feasibility of this system, with a sensitivity of 1.285 mV/μN·m in a range of 0 to 11.76 μN·m when the lever arm is 20 mm long. The measuring range can be modified by varying the length of the lever arm. Thus, this system has wide potential applications in measuring the micro-friction torque of gas bearings in rotating MEMS machines. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

17 pages, 2379 KiB

Open AccessArticle

Whole-Body Human Inverse Dynamics with Distributed Micro-Accelerometers, Gyros and Force Sensing

by Claudia Latella, Naveen Kuppuswamy, Francesco Romano, Silvio Traversaro and Francesco Nori

Sensors 2016, 16(5), 727; https://doi.org/10.3390/s16050727 - 20 May 2016

Cited by 13 | Viewed by 8035

Abstract

Human motion tracking is a powerful tool used in a large range of applications that require human movement analysis. Although it is a well-established technique, its main limitation is the lack of estimation of real-time kinetics information such as forces and torques during [...] Read more.

Human motion tracking is a powerful tool used in a large range of applications that require human movement analysis. Although it is a well-established technique, its main limitation is the lack of estimation of real-time kinetics information such as forces and torques during the motion capture. In this paper, we present a novel approach for a human soft wearable force tracking for the simultaneous estimation of whole-body forces along with the motion. The early stage of our framework encompasses traditional passive marker based methods, inertial and contact force sensor modalities and harnesses a probabilistic computational technique for estimating dynamic quantities, originally proposed in the domain of humanoid robot control. We present experimental analysis on subjects performing a two degrees-of-freedom bowing task, and we estimate the motion and kinetics quantities. The results demonstrate the validity of the proposed method. We discuss the possible use of this technique in the design of a novel soft wearable force tracking device and its potential applications. Full article

(This article belongs to the Special Issue Selected Papers from the 2nd International Electronic Conference on Sensors and Applications)

► Show Figures

Figure 1

16 pages, 1680 KiB

Open AccessArticle

1-RAAP: An Efficient 1-Round Anonymous Authentication Protocol for Wireless Body Area Networks

by Jingwei Liu, Lihuan Zhang and Rong Sun

Sensors 2016, 16(5), 728; https://doi.org/10.3390/s16050728 - 19 May 2016

Cited by 60 | Viewed by 6276

Abstract

Thanks to the rapid technological convergence of wireless communications, medical sensors and cloud computing, Wireless Body Area Networks (WBANs) have emerged as a novel networking paradigm enabling ubiquitous Internet services, allowing people to receive medical care, monitor health status in real-time, analyze sports [...] Read more.

Thanks to the rapid technological convergence of wireless communications, medical sensors and cloud computing, Wireless Body Area Networks (WBANs) have emerged as a novel networking paradigm enabling ubiquitous Internet services, allowing people to receive medical care, monitor health status in real-time, analyze sports data and even enjoy online entertainment remotely. However, because of the mobility and openness of wireless communications, WBANs are inevitably exposed to a large set of potential attacks, significantly undermining their utility and impeding their widespread deployment. To prevent attackers from threatening legitimate WBAN users or abusing WBAN services, an efficient and secure authentication protocol termed 1-Round Anonymous Authentication Protocol (1-RAAP) is proposed in this paper. In particular, 1-RAAP preserves anonymity, mutual authentication, non-repudiation and some other desirable security properties, while only requiring users to perform several low cost computational operations. More importantly, 1-RAAP is provably secure thanks to its design basis, which is resistant to the anonymous in the random oracle model. To validate the computational efficiency of 1-RAAP, a set of comprehensive comparative studies between 1-RAAP and other authentication protocols is conducted, and the results clearly show that 1-RAAP achieves the best performance in terms of computational overhead. Full article

(This article belongs to the Special Issue Security and Privacy in Sensor Networks)

► Show Figures

Figure 1

10 pages, 297 KiB

Open AccessArticle

Systematic Error Modeling and Bias Estimation

by Feihu Zhang and Alois Knoll

Sensors 2016, 16(5), 729; https://doi.org/10.3390/s16050729 - 19 May 2016

Cited by 10 | Viewed by 6643

Abstract

This paper analyzes the statistic properties of the systematic error in terms of range and bearing during the transformation process. Furthermore, we rely on a weighted nonlinear least square method to calculate the biases based on the proposed models. The results show the [...] Read more.

This paper analyzes the statistic properties of the systematic error in terms of range and bearing during the transformation process. Furthermore, we rely on a weighted nonlinear least square method to calculate the biases based on the proposed models. The results show the high performance of the proposed approach for error modeling and bias estimation. Full article

(This article belongs to the Special Issue Advances in Multi-Sensor Information Fusion: Theory and Applications)

► Show Figures

Figure 1

15 pages, 2207 KiB

Open AccessArticle

A Novel Attitude Estimation Algorithm Based on the Non-Orthogonal Magnetic Sensors

by Jianliang Zhu, Panlong Wu and Yuming Bo

Sensors 2016, 16(5), 730; https://doi.org/10.3390/s16050730 - 19 May 2016

Cited by 10 | Viewed by 5012

Abstract

Because the existing extremum ratio method for projectile attitude measurement is vulnerable to random disturbance, a novel integral ratio method is proposed to calculate the projectile attitude. First, the non-orthogonal measurement theory of the magnetic sensors is analyzed. It is found that the [...] Read more.

Because the existing extremum ratio method for projectile attitude measurement is vulnerable to random disturbance, a novel integral ratio method is proposed to calculate the projectile attitude. First, the non-orthogonal measurement theory of the magnetic sensors is analyzed. It is found that the projectile rotating velocity is constant in one spinning circle and the attitude error is actually the pitch error. Next, by investigating the model of the extremum ratio method, an integral ratio mathematical model is established to improve the anti-disturbance performance. Finally, by combining the preprocessed magnetic sensor data based on the least-square method and the rotating extremum features in one cycle, the analytical expression of the proposed integral ratio algorithm is derived with respect to the pitch angle. The simulation results show that the proposed integral ratio method gives more accurate attitude calculations than does the extremum ratio method, and that the attitude error variance can decrease by more than 90%. Compared to the extremum ratio method (which collects only a single data point in one rotation cycle), the proposed integral ratio method can utilize all of the data collected in the high spin environment, which is a clearly superior calculation approach, and can be applied to the actual projectile environment disturbance. Full article

(This article belongs to the Special Issue Magnetoresistive Sensors under Extreme Conditions)

► Show Figures

Figure 1

9 pages, 3770 KiB

Open AccessArticle

Recognizing Physisorption and Chemisorption in Carbon Nanotubes Gas Sensors by Double Exponential Fitting of the Response

by Andrea Calvi, Alberto Ferrari, Luca Sbuelz, Andrea Goldoni and Silvio Modesti

Sensors 2016, 16(5), 731; https://doi.org/10.3390/s16050731 - 19 May 2016

Cited by 29 | Viewed by 8072

Abstract

Multi-walled carbon nanotubes (CNTs) have been grown in situ on a

{SiO}_{2}

substrate and used as gas sensors. For this purpose, the voltage response of the CNTs as a function of time has been used to detect

H_{2}

and [...] Read more.

Multi-walled carbon nanotubes (CNTs) have been grown in situ on a

{SiO}_{2}

substrate and used as gas sensors. For this purpose, the voltage response of the CNTs as a function of time has been used to detect

H_{2}

and

{CO}_{2}

at various concentrations by supplying a constant current to the system. The analysis of both adsorptions and desorptions curves has revealed two different exponential behaviours for each curve. The study of the characteristic times, obtained from the fitting of the data, has allowed us to identify separately chemisorption and physisorption processes on the CNTs. Full article

(This article belongs to the Special Issue Graphene and 2D Material Bionanosensors: Chemistry Matters)

► Show Figures

Figure 1

21 pages, 13382 KiB

Open AccessArticle

GLORI: A GNSS-R Dual Polarization Airborne Instrument for Land Surface Monitoring

by Erwan Motte, Mehrez Zribi, Pascal Fanise, Alejandro Egido, José Darrozes, Amen Al-Yaari, Nicolas Baghdadi, Frédéric Baup, Sylvia Dayau, Remy Fieuzal, Pierre-Louis Frison, Dominique Guyon and Jean-Pierre Wigneron

Sensors 2016, 16(5), 732; https://doi.org/10.3390/s16050732 - 20 May 2016

Cited by 78 | Viewed by 8694

Abstract

Global Navigation Satellite System-Reflectometry (GNSS-R) has emerged as a remote sensing tool, which is complementary to traditional monostatic radars, for the retrieval of geophysical parameters related to surface properties. In the present paper, we describe a new polarimetric GNSS-R system, referred to as [...] Read more.

Global Navigation Satellite System-Reflectometry (GNSS-R) has emerged as a remote sensing tool, which is complementary to traditional monostatic radars, for the retrieval of geophysical parameters related to surface properties. In the present paper, we describe a new polarimetric GNSS-R system, referred to as the GLObal navigation satellite system Reflectometry Instrument (GLORI), dedicated to the study of land surfaces (soil moisture, vegetation water content, forest biomass) and inland water bodies. This system was installed as a permanent payload on a French ATR42 research aircraft, from which simultaneous measurements can be carried out using other instruments, when required. Following initial laboratory qualifications, two airborne campaigns involving nine flights were performed in 2014 and 2015 in the Southwest of France, over various types of land cover, including agricultural fields and forests. Some of these flights were made concurrently with in situ ground truth campaigns. Various preliminary applications for the characterisation of agricultural and forest areas are presented. Initial analysis of the data shows that the performance of the GLORI instrument is well within specifications, with a cross-polarization isolation better than −15 dB at all elevations above 45°, a relative polarimetric calibration accuracy better than 0.5 dB, and an apparent reflectivity sensitivity better than −30 dB, thus demonstrating its strong potential for the retrieval of land surface characteristics. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Graphical abstract

11 pages, 3176 KiB

Open AccessArticle

Theoretical and Experimental: The Synthetic and Anion-Binding Properties of Tripodal Salicylaldehyde Derivatives

by Zhong-Jie Xu and Li-Rong Zhang

Sensors 2016, 16(5), 733; https://doi.org/10.3390/s16050733 - 19 May 2016

Cited by 4 | Viewed by 5628

Abstract

A series of colorimetric anion probes 1–6 containing OH and NO₂ groups were synthesized, and their recognition properties toward various anions were investigated by visual observation, ultraviolet–visible spectroscopy, fluorescence, ¹H nuclear magnetic resonance titration spectra and theoretical investigation. Nanomaterials of three [...] Read more.

A series of colorimetric anion probes 1–6 containing OH and NO₂ groups were synthesized, and their recognition properties toward various anions were investigated by visual observation, ultraviolet–visible spectroscopy, fluorescence, ¹H nuclear magnetic resonance titration spectra and theoretical investigation. Nanomaterials of three compounds 2–4 were prepared successfully. Four compounds 3–6 that contain electron-withdrawing substituents showed a high binding ability for AcO⁻. The host–guest complex formed through a 1:1 binding ratio, and color changes were detectable during the recognition process. Theoretical investigation analysis revealed that an intramolecular hydrogen bond existed in the structures of compounds and the roles of molecular frontier orbitals in molecular interplay. These studies suggested that this series of compounds could be used as colorimetric probes to detect of AcO⁻. Full article

(This article belongs to the Special Issue Colorimetric and Fluorescent Sensor)

► Show Figures

Figure 1

11 pages, 2585 KiB

Open AccessArticle

An All-Fiber-Optic Combined System of Noncontact Photoacoustic Tomography and Optical Coherence Tomography

by Jonghyun Eom, Jun Geun Shin, Soongho Park, Sunghwan Rim and Byeong Ha Lee

Sensors 2016, 16(5), 734; https://doi.org/10.3390/s16050734 - 20 May 2016

Cited by 15 | Viewed by 8570

Abstract

We propose an all-fiber-based dual-modal imaging system that combines noncontact photoacoustic tomography (PAT) and optical coherence tomography (OCT). The PAT remotely measures photoacoustic (PA) signals with a 1550-nm laser on the surface of a sample by utilizing a fiber interferometer as an ultrasound [...] Read more.

We propose an all-fiber-based dual-modal imaging system that combines noncontact photoacoustic tomography (PAT) and optical coherence tomography (OCT). The PAT remotely measures photoacoustic (PA) signals with a 1550-nm laser on the surface of a sample by utilizing a fiber interferometer as an ultrasound detector. The fiber-based OCT, employing a swept-source laser centered at 1310 nm, shares the sample arm of the PAT system. The fiber-optic probe for the combined system was homemade with a lensed single-mode fiber (SMF) and a large-core multimode fiber (MMF). The compact and robust common probe is capable of obtaining both the PA and the OCT signals at the same position without any physical contact. Additionally, the MMF of the probe delivers the short pulses of a Nd:YAG laser to efficiently excite the PA signals. We experimentally demonstrate the feasibility of the proposed dual-modal system with a phantom made of a fishing line and a black polyethylene terephthalate fiber in a tissue mimicking solution. The all-fiber-optic system, capable of providing complementary information about absorption and scattering, has a promising potential in minimally invasive and endoscopic imaging. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2016)

► Show Figures

Graphical abstract

18 pages, 5629 KiB

Open AccessArticle

An Approach to the Prototyping of an Optimized Limited Stroke Actuator to Drive a Low Pressure Exhaust Gas Recirculation Valve

by Christophe Gutfrind, Laurent Dufour, Vincent Liebart, Jean-Claude Vannier and Pierre Vidal

Sensors 2016, 16(5), 735; https://doi.org/10.3390/s16050735 - 20 May 2016

Cited by 3 | Viewed by 8317

Abstract

The purpose of this article is to describe the design of a limited stroke actuator and the corresponding prototype to drive a Low Pressure (LP) Exhaust Gas Recirculation (EGR) valve for use in Internal Combustion Engines (ICEs). The direct drive actuator topology is [...] Read more.

The purpose of this article is to describe the design of a limited stroke actuator and the corresponding prototype to drive a Low Pressure (LP) Exhaust Gas Recirculation (EGR) valve for use in Internal Combustion Engines (ICEs). The direct drive actuator topology is an axial flux machine with two air gaps in order to minimize the rotor inertia and a bipolar surface-mounted permanent magnet in order to respect an 80° angular stroke. Firstly, the actuator will be described and optimized under constraints of a 150 ms time response, a 0.363 N·m minimal torque on an angular range from 0° to 80° and prototyping constraints. Secondly, the finite element method (FEM) using the FLUX-3D^® software (CEDRAT, Meylan, France) will be used to check the actuator performances with consideration of the nonlinear effect of the iron material. Thirdly, a prototype will be made and characterized to compare its measurement results with the analytical model and the FEM model results. With these electromechanical behavior measurements, a numerical model is created with Simulink^® in order to simulate an EGR system with this direct drive actuator under all operating conditions. Last but not least, the energy consumption of this machine will be estimated to evaluate the efficiency of the proposed EGR electromechanical system. Full article

(This article belongs to the Special Issue Components of Mechatronics and Micro-Electro-Mechanical-Systems (MEMS) – Modeling and Design)

► Show Figures

Figure 1

25 pages, 5063 KiB

Open AccessArticle

Design and Implementation of a Novel Compatible Encoding Scheme in the Time Domain for Image Sensor Communication

by Trang Nguyen, Mohammad Arif Hossain and Yeong Min Jang

Sensors 2016, 16(5), 736; https://doi.org/10.3390/s16050736 - 20 May 2016

Cited by 31 | Viewed by 7612

Abstract

This paper presents a modulation scheme in the time domain based on On-Off-Keying and proposes various compatible supports for different types of image sensors. The content of this article is a sub-proposal to the IEEE 802.15.7r1 Task Group (TG7r1) aimed at Optical Wireless [...] Read more.

This paper presents a modulation scheme in the time domain based on On-Off-Keying and proposes various compatible supports for different types of image sensors. The content of this article is a sub-proposal to the IEEE 802.15.7r1 Task Group (TG7r1) aimed at Optical Wireless Communication (OWC) using an image sensor as the receiver. The compatibility support is indispensable for Image Sensor Communications (ISC) because the rolling shutter image sensors currently available have different frame rates, shutter speeds, sampling rates, and resolutions. However, focusing on unidirectional communications (i.e., data broadcasting, beacons), an asynchronous communication prototype is also discussed in the paper. Due to the physical limitations associated with typical image sensors (including low and varying frame rates, long exposures, and low shutter speeds), the link speed performance is critically considered. Based on the practical measurement of camera response to modulated light, an operating frequency range is suggested along with the similar system architecture, decoding procedure, and algorithms. A significant feature of our novel data frame structure is that it can support both typical frame rate cameras (in the oversampling mode) as well as very low frame rate cameras (in the error detection mode for a camera whose frame rate is lower than the transmission packet rate). A high frame rate camera, i.e., no less than 20 fps, is supported in an oversampling mode in which a majority voting scheme for decoding data is applied. A low frame rate camera, i.e., when the frame rate drops to less than 20 fps at some certain time, is supported by an error detection mode in which any missing data sub-packet is detected in decoding and later corrected by external code. Numerical results and valuable analysis are also included to indicate the capability of the proposed schemes. Full article

(This article belongs to the Special Issue Image Sensor Based Optical Wireless Communications– Selected Papers from the 7th International Conference on Ubiquitous and Future Networks and the 3rd International Workshop on Optical-Wireless LED Communication Networks)

► Show Figures

Figure 1

15 pages, 650 KiB

Open AccessArticle

On the Choice of Access Point Selection Criterion and Other Position Estimation Characteristics for WLAN-Based Indoor Positioning

by Elina Laitinen and Elena Simona Lohan

Sensors 2016, 16(5), 737; https://doi.org/10.3390/s16050737 - 20 May 2016

Cited by 28 | Viewed by 5470

Abstract

The positioning based on Wireless Local Area Networks (WLAN) is one of the most promising technologies for indoor location-based services, generally using the information carried by Received Signal Strengths (RSS). One challenge, however, is the huge amount of data in the radiomap database [...] Read more.

The positioning based on Wireless Local Area Networks (WLAN) is one of the most promising technologies for indoor location-based services, generally using the information carried by Received Signal Strengths (RSS). One challenge, however, is the huge amount of data in the radiomap database due to the enormous number of hearable Access Points (AP) that could make the positioning system very complex. This paper concentrates on WLAN-based indoor location by comparing fingerprinting, path loss and weighted centroid based positioning approaches in terms of complexity and performance and studying the effects of grid size and AP reduction with several choices for appropriate selection criterion. All results are based on real field measurements in three multi-floor buildings. We validate our earlier findings concerning several different AP selection criteria and conclude that the best results are obtained with a maximum RSS-based criterion, which also proved to be the most consistent among the different investigated approaches. We show that the weighted centroid based low-complexity method is very sensitive to AP reduction, while the path loss-based method is also very robust to high percentage removals. Indeed, for fingerprinting, 50% of the APs can be removed safely with a properly chosen removal criterion without increasing the positioning error much. Full article

(This article belongs to the Special Issue Scalable Localization in Wireless Sensor Networks)

► Show Figures

Graphical abstract

11 pages, 4099 KiB

Open AccessArticle

Induced Voltage Linear Extraction Method Using an Active Kelvin Bridge for Disturbing Force Self-Sensing

by Yuanyuan Yang, Lei Wang, Jiubin Tan and Bo Zhao

Sensors 2016, 16(5), 739; https://doi.org/10.3390/s16050739 - 20 May 2016

Cited by 6 | Viewed by 5595

Abstract

This paper presents an induced voltage linear extraction method for disturbing force self-sensing in the application of giant magnetostrictive actuators (GMAs). In this method, a Kelvin bridge combined with an active device is constructed instead of a conventional Wheatstone bridge for extraction of [...] Read more.

This paper presents an induced voltage linear extraction method for disturbing force self-sensing in the application of giant magnetostrictive actuators (GMAs). In this method, a Kelvin bridge combined with an active device is constructed instead of a conventional Wheatstone bridge for extraction of the induced voltage, and an additional GMA is adopted as a reference actuator in the self-sensing circuit in order to balance the circuit bridge. The linear fitting of the measurement data is done according to the linear relationship between the disturbing forces and the integral of the induced voltage. The experimental results confirm the good performance of the proposed method, and the self-sensitivity of the disturbing forces is better than 2.0 (mV·s)/N. Full article

(This article belongs to the Special Issue Giant Magnetoresistive Sensors)

► Show Figures

Figure 1

18 pages, 6389 KiB

Open AccessArticle

A Longitudinal Mode Electromagnetic Acoustic Transducer (EMAT) Based on a Permanent Magnet Chain for Pipe Inspection

by Ming Cong, Xinjun Wu and Chunqiao Qian

Sensors 2016, 16(5), 740; https://doi.org/10.3390/s16050740 - 21 May 2016

Cited by 34 | Viewed by 10768

Abstract

A new electromagnetic acoustic transducer (EMAT) design, employing a special structure of the permanent magnet chain, is proposed to generate and receive longitudinal guided waves for pipe inspection based on the magnetostriction mechanism. Firstly, a quantitative analysis of the excitation forces shows the [...] Read more.

A new electromagnetic acoustic transducer (EMAT) design, employing a special structure of the permanent magnet chain, is proposed to generate and receive longitudinal guided waves for pipe inspection based on the magnetostriction mechanism. Firstly, a quantitative analysis of the excitation forces shows the influence of the radial component can be ignored. Furthermore, as the axial component of the static magnetic field is dominant, a method of solenoid testing coils connected in series is adopted to increase the signal amplitude. Then, two EMAT configurations are developed to generate and receive the L(0,2) guided wave mode. The experimental results show the circumferential notch can be identified and located successfully. Finally, a detailed investigation of the performance of the proposed EMATs is given. Compared to the conventional EMAT configuration, the proposed configurations have the advantages of small volume, light weight, easy installation and portability, which is helpful to improve inspection efficiency. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Graphical abstract

15 pages, 1702 KiB

Open AccessArticle

Domotics Project Housing Block

by Carlos Morón, Alejandro Payán, Alfonso García and Francisco Bosquet

Sensors 2016, 16(5), 741; https://doi.org/10.3390/s16050741 - 23 May 2016

Cited by 6 | Viewed by 7163

Abstract

This document develops the study of an implementation project of a home automation system in a housing placed in the town of Galapagar, Madrid. This house, which is going to be occupied by a four-member family, consists of 67 constructed square meters distributed [...] Read more.

This document develops the study of an implementation project of a home automation system in a housing placed in the town of Galapagar, Madrid. This house, which is going to be occupied by a four-member family, consists of 67 constructed square meters distributed in lounge, kitchen, three bedrooms, bath, bathroom and terrace, this being a common arrangement in Spain. Thus, this study will allow extracting conclusions about the adequacy of the home automation in a wide percentage of housing in Spain. In this document, three house automation proposals are developed based on the requirements of the client and the different home automation levels that the Spanish House and Building Automation Association has established, besides two parallel proposals relating to the safety and the technical alarms. The mentioned proposed systems are described by means of product datasheets and descriptions, distribution plans, measurements, budgets and flow charts that describe the functioning of the system in every case. An evaluation of each system is included, based on other studies conclusions on this matter, where expected energy savings from each design, depending on the current cost of lighting, water and gas, as well as the expected economic amortization period is evaluated. Full article

(This article belongs to the Special Issue Selected Papers from the 2nd International Electronic Conference on Sensors and Applications)

► Show Figures

Figure 1

17 pages, 5341 KiB

Open AccessArticle

A Novel Transient Fault Current Sensor Based on the PCB Rogowski Coil for Overhead Transmission Lines

by Yadong Liu, Xiaolei Xie, Yue Hu, Yong Qian, Gehao Sheng and Xiuchen Jiang

Sensors 2016, 16(5), 742; https://doi.org/10.3390/s16050742 - 21 May 2016

Cited by 34 | Viewed by 12221

Abstract

The accurate detection of high-frequency transient fault currents in overhead transmission lines is the basis of malfunction detection and diagnosis. This paper proposes a novel differential winding printed circuit board (PCB) Rogowski coil for the detection of transient fault currents in overhead transmission [...] Read more.

The accurate detection of high-frequency transient fault currents in overhead transmission lines is the basis of malfunction detection and diagnosis. This paper proposes a novel differential winding printed circuit board (PCB) Rogowski coil for the detection of transient fault currents in overhead transmission lines. The interference mechanism of the sensor surrounding the overhead transmission line is analyzed and the guideline for the interference elimination is obtained, and then a differential winding printed circuit board (PCB) Rogowski coil is proposed, where the branch and return line of the PCB coil were designed to be strictly symmetrical by using a joining structure of two semi-rings and collinear twisted pair differential windings in each semi-ring. A serial test is conducted, including the frequency response, linearity, and anti-interference performance as well as a comparison with commercial sensors. Results show that a PCB Rogowski coil has good linearity and resistance to various external magnetic field interferences, thus enabling it to be widely applied in fault-current-collecting devices. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

13 pages, 4608 KiB

Open AccessArticle

Experimental Evaluation of Pulsed Thermography, Lock-in Thermography and Vibrothermography on Foreign Object Defect (FOD) in CFRP

by Bin Liu, Hai Zhang, Henrique Fernandes and Xavier Maldague

Sensors 2016, 16(5), 743; https://doi.org/10.3390/s16050743 - 21 May 2016

Cited by 47 | Viewed by 7038 | Correction

Abstract

In this article, optical excitation thermographic techniques, including pulsed thermography and lock-in thermography, were used to detect foreign object defect (FOD) and delamination in CFRP. Then, vibrothermography as an ultrasonic excitation technique was used to detect these defects for the comparative purposes. Different [...] Read more.

In this article, optical excitation thermographic techniques, including pulsed thermography and lock-in thermography, were used to detect foreign object defect (FOD) and delamination in CFRP. Then, vibrothermography as an ultrasonic excitation technique was used to detect these defects for the comparative purposes. Different image processing methods, including cold image subtraction (CIS), principal component thermography (PCT), thermographic signal reconstruction (TSR) and Fourier transform (FT), were performed. Finally, a comparison of optical excitation thermography and vibrothermography was conducted, and a thermographic probability of detection was given. Full article

(This article belongs to the Special Issue Infrared and THz Sensing and Imaging)

► Show Figures

Figure 1

13 pages, 2332 KiB

Open AccessArticle

Self-Oscillation-Based Frequency Tracking for the Drive and Detection of Resonance Magnetometers

by Zheng Tian, Dahai Ren and Zheng You

Sensors 2016, 16(5), 744; https://doi.org/10.3390/s16050744 - 21 May 2016

Cited by 7 | Viewed by 7990

Abstract

This paper reports a drive and detection method for Micro-Electro-Mechanical System (MEMS)-based Lorentz-force resonance magnetometers. Based on the proposed MEMS magnetometer, a drive and detection method was developed by using self-oscillation to adjust the mismatch between the mechanical resonance frequency and the coil [...] Read more.

This paper reports a drive and detection method for Micro-Electro-Mechanical System (MEMS)-based Lorentz-force resonance magnetometers. Based on the proposed MEMS magnetometer, a drive and detection method was developed by using self-oscillation to adjust the mismatch between the mechanical resonance frequency and the coil drive frequency as affected by temperature fluctuations and vibration amplitude changes. Not only was the signal-to-noise ratio enhanced by the proposed method compared to the traditional method, but the test system automatically reached resonance frequency very rapidly when powered on. Moreover, the linearity and the measurement range were improved by the magnetic feedback generated by the coil. Test results indicated that the sensitivity of the proposed magnetometer is 59.6 mV/μT and its noise level is 0.25 μT. When operating in ±65 μT, its nonlinearity is 2.5‰—only one-tenth of the former prototype. Its power consumption is only about 250 mW and its size is only 28 mm × 28 mm × 10 mm, or about one-eighth of the original sensor; further, unlike the former device, it can distinguish both positive and negative magnetic fields. The proposed method can also be applied in other MEMS sensors such as gyroscopes and micromirrors to enhance their frequency tracking ability. Full article

(This article belongs to the Collection Modeling, Testing and Reliability Issues in MEMS Engineering)

► Show Figures

Figure 1

19 pages, 5069 KiB

Open AccessArticle

A Task-Centric Cooperative Sensing Scheme for Mobile Crowdsourcing Systems

by Ziwei Liu, Xiaoguang Niu, Xu Lin, Ting Huang, Yunlong Wu and Hui Li

Sensors 2016, 16(5), 746; https://doi.org/10.3390/s16050746 - 23 May 2016

Cited by 9 | Viewed by 5234

Abstract

In a densely distributed mobile crowdsourcing system, data collected by neighboring participants often exhibit strong spatial correlations. By exploiting this property, one may employ a portion of the users as active participants and set the other users as idling ones without compromising the [...] Read more.

In a densely distributed mobile crowdsourcing system, data collected by neighboring participants often exhibit strong spatial correlations. By exploiting this property, one may employ a portion of the users as active participants and set the other users as idling ones without compromising the quality of sensing or the connectivity of the network. In this work, two participant selection questions are considered: (a) how to recruit an optimal number of users as active participants to guarantee that the overall sensing data integrity is kept above a preset threshold; and (b) how to recruit an optimal number of participants with some inaccurate data so that the fairness of selection and resource conservation can be achieved while maintaining sufficient sensing data integrity. For question (a), we propose a novel task-centric approach to explicitly exploit data correlation among participants. This subset selection problem is regarded as a constrained optimization problem and we propose an efficient polynomial time algorithm to solve it. For question (b), we formulate this set partitioning problem as a constrained min-max optimization problem. A solution using an improved version of the polynomial time algorithm is proposed based on (a). We validate these algorithms using a publicly available Intel-Berkeley lab sensing dataset and satisfactory performance is achieved. Full article

(This article belongs to the Special Issue Identification, Information & Knowledge in the Internet of Things)

► Show Figures

Figure 1

27 pages, 5936 KiB

Open AccessArticle

Integrated Navigation System Design for Micro Planetary Rovers: Comparison of Absolute Heading Estimation Algorithms and Nonlinear Filtering

by Muhammad Ilyas, Beomjin Hong, Kuk Cho, Seung-Ho Baeg and Sangdeok Park

Sensors 2016, 16(5), 749; https://doi.org/10.3390/s16050749 - 23 May 2016

Cited by 6 | Viewed by 8762

Abstract

This paper provides algorithms to fuse relative and absolute microelectromechanical systems (MEMS) navigation sensors, suitable for micro planetary rovers, to provide a more accurate estimation of navigation information, specifically, attitude and position. Planetary rovers have extremely slow speed (~1 cm/s) and lack conventional [...] Read more.

This paper provides algorithms to fuse relative and absolute microelectromechanical systems (MEMS) navigation sensors, suitable for micro planetary rovers, to provide a more accurate estimation of navigation information, specifically, attitude and position. Planetary rovers have extremely slow speed (~1 cm/s) and lack conventional navigation sensors/systems, hence the general methods of terrestrial navigation may not be applicable to these applications. While relative attitude and position can be tracked in a way similar to those for ground robots, absolute navigation information is hard to achieve on a remote celestial body, like Moon or Mars, in contrast to terrestrial applications. In this study, two absolute attitude estimation algorithms were developed and compared for accuracy and robustness. The estimated absolute attitude was fused with the relative attitude sensors in a framework of nonlinear filters. The nonlinear Extended Kalman filter (EKF) and Unscented Kalman filter (UKF) were compared in pursuit of better accuracy and reliability in this nonlinear estimation problem, using only on-board low cost MEMS sensors. Experimental results confirmed the viability of the proposed algorithms and the sensor suite, for low cost and low weight micro planetary rovers. It is demonstrated that integrating the relative and absolute navigation MEMS sensors reduces the navigation errors to the desired level. Full article

(This article belongs to the Collection Modeling, Testing and Reliability Issues in MEMS Engineering)

► Show Figures

Figure 1

14 pages, 5125 KiB

Open AccessArticle

Sleep Monitoring Based on a Tri-Axial Accelerometer and a Pressure Sensor

by Yunyoung Nam, Yeesock Kim and Jinseok Lee

Sensors 2016, 16(5), 750; https://doi.org/10.3390/s16050750 - 23 May 2016

Cited by 112 | Viewed by 17142

Abstract

Sleep disorders are a common affliction for many people even though sleep is one of the most important factors in maintaining good physiological and emotional health. Numerous researchers have proposed various approaches to monitor sleep, such as polysomnography and actigraphy. However, such approaches [...] Read more.

Sleep disorders are a common affliction for many people even though sleep is one of the most important factors in maintaining good physiological and emotional health. Numerous researchers have proposed various approaches to monitor sleep, such as polysomnography and actigraphy. However, such approaches are costly and often require overnight treatment in clinics. With this in mind, the research presented here has emerged from the question: “Can data be easily collected and analyzed without causing discomfort to patients?” Therefore, the aim of this study is to provide a novel monitoring system for quantifying sleep quality. The data acquisition system is equipped with multimodal sensors, including a three-axis accelerometer and a pressure sensor. To identify sleep quality based on measured data, a novel algorithm, which uses numerous physiological parameters, was proposed. Such parameters include non-REM sleep time, the number of apneic episodes, and sleep durations for dominant poses. To assess the effectiveness of the proposed system, three participants were enrolled in this experimental study for a duration of 20 days. From the experimental results, it can be seen that the proposed monitoring system is effective for quantifying sleep quality. Full article

(This article belongs to the Special Issue Wearable Biomedical Sensors)

► Show Figures

Figure 1

10 pages, 1236 KiB

Open AccessArticle

Atmospheric and Fog Effects on Ultra-Wide Band Radar Operating at Extremely High Frequencies

by Nezah Balal, Gad A. Pinhasi and Yosef Pinhasi

Sensors 2016, 16(5), 751; https://doi.org/10.3390/s16050751 - 23 May 2016

Cited by 28 | Viewed by 6676

Abstract

The wide band at extremely high frequencies (EHF) above 30 GHz is applicable for high resolution directive radars, resolving the lack of free frequency bands within the lower part of the electromagnetic spectrum. Utilization of ultra-wideband signals in this EHF band is of [...] Read more.

The wide band at extremely high frequencies (EHF) above 30 GHz is applicable for high resolution directive radars, resolving the lack of free frequency bands within the lower part of the electromagnetic spectrum. Utilization of ultra-wideband signals in this EHF band is of interest, since it covers a relatively large spectrum, which is free of users, resulting in better resolution in both the longitudinal and transverse dimensions. Noting that frequencies in the millimeter band are subjected to high atmospheric attenuation and dispersion effects, a study of the degradation in the accuracy and resolution is presented. The fact that solid-state millimeter and sub-millimeter radiation sources are producing low power, the method of continuous-wave wideband frequency modulation becomes the natural technique for remote sensing and detection. Millimeter wave radars are used as complementary sensors for the detection of small radar cross-section objects under bad weather conditions, when small objects cannot be seen by optical cameras and infrared detectors. Theoretical analysis for the propagation of a wide “chirped” Frequency-Modulated Continuous-Wave (FMCW) radar signal in a dielectric medium is presented. It is shown that the frequency-dependent (complex) refractivity of the atmospheric medium causes distortions in the phase of the reflected signal, introducing noticeable errors in the longitudinal distance estimations, and at some frequencies may also degrade the resolution. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

13 pages, 2357 KiB

Open AccessArticle

An Improved Measurement Method for the Strength of Radiation of Reflective Beam in an Industrial Optical Sensor Based on Laser Displacement Meter

by Youngchul Bae

Sensors 2016, 16(5), 752; https://doi.org/10.3390/s16050752 - 23 May 2016

Cited by 10 | Viewed by 6815

Abstract

An optical sensor such as a laser range finder (LRF) or laser displacement meter (LDM) uses reflected and returned laser beam from a target. The optical sensor has been mainly used to measure the distance between a launch position and the target. However, [...] Read more.

An optical sensor such as a laser range finder (LRF) or laser displacement meter (LDM) uses reflected and returned laser beam from a target. The optical sensor has been mainly used to measure the distance between a launch position and the target. However, optical sensor based LRF and LDM have numerous and various errors such as statistical errors, drift errors, cyclic errors, alignment errors and slope errors. Among these errors, an alignment error that contains measurement error for the strength of radiation of returned laser beam from the target is the most serious error in industrial optical sensors. It is caused by the dependence of the measurement offset upon the strength of radiation of returned beam incident upon the focusing lens from the target. In this paper, in order to solve these problems, we propose a novel method for the measurement of the output of direct current (DC) voltage that is proportional to the strength of radiation of returned laser beam in the received avalanche photo diode (APD) circuit. We implemented a measuring circuit that is able to provide an exact measurement of reflected laser beam. By using the proposed method, we can measure the intensity or strength of radiation of laser beam in real time and with a high degree of precision. Full article

(This article belongs to the Special Issue Selected Papers From the 16th International Symposium on Advanced Intelligent Systems (ISIS))

► Show Figures

Figure 1

20 pages, 2242 KiB

Open AccessArticle

myBlackBox: Blackbox Mobile Cloud Systems for Personalized Unusual Event Detection

by Junho Ahn and Richard Han

Sensors 2016, 16(5), 753; https://doi.org/10.3390/s16050753 - 23 May 2016

Cited by 2 | Viewed by 7064

Abstract

We demonstrate the feasibility of constructing a novel and practical real-world mobile cloud system, called myBlackBox, that efficiently fuses multimodal smartphone sensor data to identify and log unusual personal events in mobile users’ daily lives. The system incorporates a hybrid architectural design that [...] Read more.

We demonstrate the feasibility of constructing a novel and practical real-world mobile cloud system, called myBlackBox, that efficiently fuses multimodal smartphone sensor data to identify and log unusual personal events in mobile users’ daily lives. The system incorporates a hybrid architectural design that combines unsupervised classification of audio, accelerometer and location data with supervised joint fusion classification to achieve high accuracy, customization, convenience and scalability. We show the feasibility of myBlackBox by implementing and evaluating this end-to-end system that combines Android smartphones with cloud servers, deployed for 15 users over a one-month period. Full article

(This article belongs to the Special Issue Advances in Multi-Sensor Information Fusion: Theory and Applications)

► Show Figures

Graphical abstract

Review

Jump to: Editorial, Research, Other

29 pages, 846 KiB

Open AccessReview

Search Techniques for the Web of Things: A Taxonomy and Survey

by Yuchao Zhou, Suparna De, Wei Wang and Klaus Moessner

Sensors 2016, 16(5), 600; https://doi.org/10.3390/s16050600 - 27 Apr 2016

Cited by 61 | Viewed by 9828

Abstract

The Web of Things aims to make physical world objects and their data accessible through standard Web technologies to enable intelligent applications and sophisticated data analytics. Due to the amount and heterogeneity of the data, it is challenging to perform data analysis directly; [...] Read more.

The Web of Things aims to make physical world objects and their data accessible through standard Web technologies to enable intelligent applications and sophisticated data analytics. Due to the amount and heterogeneity of the data, it is challenging to perform data analysis directly; especially when the data is captured from a large number of distributed sources. However, the size and scope of the data can be reduced and narrowed down with search techniques, so that only the most relevant and useful data items are selected according to the application requirements. Search is fundamental to the Web of Things while challenging by nature in this context, e.g., mobility of the objects, opportunistic presence and sensing, continuous data streams with changing spatial and temporal properties, efficient indexing for historical and real time data. The research community has developed numerous techniques and methods to tackle these problems as reported by a large body of literature in the last few years. A comprehensive investigation of the current and past studies is necessary to gain a clear view of the research landscape and to identify promising future directions. This survey reviews the state-of-the-art search methods for the Web of Things, which are classified according to three different viewpoints: basic principles, data/knowledge representation, and contents being searched. Experiences and lessons learned from the existing work and some EU research projects related to Web of Things are discussed, and an outlook to the future research is presented. Full article

(This article belongs to the Special Issue Identification, Information & Knowledge in the Internet of Things)

► Show Figures

Graphical abstract

12 pages, 1106 KiB

Open AccessReview

Photon Counting Imaging with an Electron-Bombarded Pixel Image Sensor

by Liisa M. Hirvonen and Klaus Suhling

Sensors 2016, 16(5), 617; https://doi.org/10.3390/s16050617 - 28 Apr 2016

Cited by 22 | Viewed by 9746

Abstract

Electron-bombarded pixel image sensors, where a single photoelectron is accelerated directly into a CCD or CMOS sensor, allow wide-field imaging at extremely low light levels as they are sensitive enough to detect single photons. This technology allows the detection of up to hundreds [...] Read more.

Electron-bombarded pixel image sensors, where a single photoelectron is accelerated directly into a CCD or CMOS sensor, allow wide-field imaging at extremely low light levels as they are sensitive enough to detect single photons. This technology allows the detection of up to hundreds or thousands of photon events per frame, depending on the sensor size, and photon event centroiding can be employed to recover resolution lost in the detection process. Unlike photon events from electron-multiplying sensors, the photon events from electron-bombarded sensors have a narrow, acceleration-voltage-dependent pulse height distribution. Thus a gain voltage sweep during exposure in an electron-bombarded sensor could allow photon arrival time determination from the pulse height with sub-frame exposure time resolution. We give a brief overview of our work with electron-bombarded pixel image sensor technology and recent developments in this field for single photon counting imaging, and examples of some applications. Full article

(This article belongs to the Special Issue Photon-Counting Image Sensors)

► Show Figures

Graphical abstract

24 pages, 2763 KiB

Open AccessReview

3-D Imaging Systems for Agricultural Applications—A Review

by Manuel Vázquez-Arellano, Hans W. Griepentrog, David Reiser and Dimitris S. Paraforos

Sensors 2016, 16(5), 618; https://doi.org/10.3390/s16050618 - 29 Apr 2016

Cited by 210 | Viewed by 21884 | Correction

Abstract

Efficiency increase of resources through automation of agriculture requires more information about the production process, as well as process and machinery status. Sensors are necessary for monitoring the status and condition of production by recognizing the surrounding structures such as objects, field structures, [...] Read more.

Efficiency increase of resources through automation of agriculture requires more information about the production process, as well as process and machinery status. Sensors are necessary for monitoring the status and condition of production by recognizing the surrounding structures such as objects, field structures, natural or artificial markers, and obstacles. Currently, three dimensional (3-D) sensors are economically affordable and technologically advanced to a great extent, so a breakthrough is already possible if enough research projects are commercialized. The aim of this review paper is to investigate the state-of-the-art of 3-D vision systems in agriculture, and the role and value that only 3-D data can have to provide information about environmental structures based on the recent progress in optical 3-D sensors. The structure of this research consists of an overview of the different optical 3-D vision techniques, based on the basic principles. Afterwards, their application in agriculture are reviewed. The main focus lays on vehicle navigation, and crop and animal husbandry. The depth dimension brought by 3-D sensors provides key information that greatly facilitates the implementation of automation and robotics in agriculture. Full article

(This article belongs to the Special Issue Sensors for Agriculture)

► Show Figures

Graphical abstract

36 pages, 658 KiB

Open AccessReview

Ultra Wideband Indoor Positioning Technologies: Analysis and Recent Advances

by Abdulrahman Alarifi, AbdulMalik Al-Salman, Mansour Alsaleh, Ahmad Alnafessah, Suheer Al-Hadhrami, Mai A. Al-Ammar and Hend S. Al-Khalifa

Sensors 2016, 16(5), 707; https://doi.org/10.3390/s16050707 - 16 May 2016

Cited by 969 | Viewed by 43382

Abstract

In recent years, indoor positioning has emerged as a critical function in many end-user applications; including military, civilian, disaster relief and peacekeeping missions. In comparison with outdoor environments, sensing location information in indoor environments requires a higher precision and is a more challenging [...] Read more.

In recent years, indoor positioning has emerged as a critical function in many end-user applications; including military, civilian, disaster relief and peacekeeping missions. In comparison with outdoor environments, sensing location information in indoor environments requires a higher precision and is a more challenging task in part because various objects reflect and disperse signals. Ultra WideBand (UWB) is an emerging technology in the field of indoor positioning that has shown better performance compared to others. In order to set the stage for this work, we provide a survey of the state-of-the-art technologies in indoor positioning, followed by a detailed comparative analysis of UWB positioning technologies. We also provide an analysis of strengths, weaknesses, opportunities, and threats (SWOT) to analyze the present state of UWB positioning technologies. While SWOT is not a quantitative approach, it helps in assessing the real status and in revealing the potential of UWB positioning to effectively address the indoor positioning problem. Unlike previous studies, this paper presents new taxonomies, reviews some major recent advances, and argues for further exploration by the research community of this challenging problem space. Full article

(This article belongs to the Special Issue Scalable Localization in Wireless Sensor Networks)

► Show Figures

Figure 1

14 pages, 1228 KiB

Open AccessReview

State of the Art in LP-WAN Solutions for Industrial IoT Services

by Ramon Sanchez-Iborra and Maria-Dolores Cano

Sensors 2016, 16(5), 708; https://doi.org/10.3390/s16050708 - 17 May 2016

Cited by 227 | Viewed by 18576

Abstract

The emergence of low-cost connected devices is enabling a new wave of sensorization services. These services can be highly leveraged in industrial applications. However, the technologies employed so far for managing this kind of system do not fully cover the strict requirements of [...] Read more.

The emergence of low-cost connected devices is enabling a new wave of sensorization services. These services can be highly leveraged in industrial applications. However, the technologies employed so far for managing this kind of system do not fully cover the strict requirements of industrial networks, especially those regarding energy efficiency. In this article a novel paradigm, called Low-Power Wide Area Networking (LP-WAN), is explored. By means of a cellular-type architecture, LP-WAN–based solutions aim at fulfilling the reliability and efficiency challenges posed by long-term industrial networks. Thus, the most prominent LP-WAN solutions are reviewed, identifying and discussing the pros and cons of each of them. The focus is also on examining the current deployment state of these platforms in Spain. Although LP-WAN systems are at early stages of development, they represent a promising alternative for boosting future industrial IIoT (Industrial Internet of Things) networks and services. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2015)

► Show Figures

Figure 1

20 pages, 1297 KiB

Open AccessReview

Contextualising Water Use in Residential Settings: A Survey of Non-Intrusive Techniques and Approaches

by Davide Carboni, Alex Gluhak, Julie A. McCann and Thomas H. Beach

Sensors 2016, 16(5), 738; https://doi.org/10.3390/s16050738 - 20 May 2016

Cited by 31 | Viewed by 8560

Abstract

Water monitoring in households is important to ensure the sustainability of fresh water reserves on our planet. It provides stakeholders with the statistics required to formulate optimal strategies in residential water management. However, this should not be prohibitive and appliance-level water monitoring cannot [...] Read more.

Water monitoring in households is important to ensure the sustainability of fresh water reserves on our planet. It provides stakeholders with the statistics required to formulate optimal strategies in residential water management. However, this should not be prohibitive and appliance-level water monitoring cannot practically be achieved by deploying sensors on every faucet or water-consuming device of interest due to the higher hardware costs and complexity, not to mention the risk of accidental leakages that can derive from the extra plumbing needed. Machine learning and data mining techniques are promising techniques to analyse monitored data to obtain non-intrusive water usage disaggregation. This is because they can discern water usage from the aggregated data acquired from a single point of observation. This paper provides an overview of water usage disaggregation systems and related techniques adopted for water event classification. The state-of-the art of algorithms and testbeds used for fixture recognition are reviewed and a discussion on the prominent challenges and future research are also included. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Graphical abstract

12 pages, 3992 KiB

Open AccessReview

Compact SPAD-Based Pixel Architectures for Time-Resolved Image Sensors

by Matteo Perenzoni, Lucio Pancheri and David Stoppa

Sensors 2016, 16(5), 745; https://doi.org/10.3390/s16050745 - 23 May 2016

Cited by 47 | Viewed by 12922

Abstract

This paper reviews the state of the art of single-photon avalanche diode (SPAD) image sensors for time-resolved imaging. The focus of the paper is on pixel architectures featuring small pixel size (<25 μm) and high fill factor (>20%) as a key enabling technology [...] Read more.

This paper reviews the state of the art of single-photon avalanche diode (SPAD) image sensors for time-resolved imaging. The focus of the paper is on pixel architectures featuring small pixel size (<25 μm) and high fill factor (>20%) as a key enabling technology for the successful implementation of high spatial resolution SPAD-based image sensors. A summary of the main CMOS SPAD implementations, their characteristics and integration challenges, is provided from the perspective of targeting large pixel arrays, where one of the key drivers is the spatial uniformity. The main analog techniques aimed at time-gated photon counting and photon timestamping suitable for compact and low-power pixels are critically discussed. The main features of these solutions are the adoption of analog counting techniques and time-to-analog conversion, in NMOS-only pixels. Reliable quantum-limited single-photon counting, self-referenced analog-to-digital conversion, time gating down to 0.75 ns and timestamping with 368 ps jitter are achieved. Full article

(This article belongs to the Special Issue Photon-Counting Image Sensors)

► Show Figures

Graphical abstract

35 pages, 13031 KiB

Open AccessReview

A Review of Distributed Optical Fiber Sensors for Civil Engineering Applications

by António Barrias, Joan R. Casas and Sergi Villalba

Sensors 2016, 16(5), 748; https://doi.org/10.3390/s16050748 - 23 May 2016

Cited by 721 | Viewed by 30539

Abstract

The application of structural health monitoring (SHM) systems to civil engineering structures has been a developing studied and practiced topic, that has allowed for a better understanding of structures’ conditions and increasingly lead to a more cost-effective management of those infrastructures. In this [...] Read more.

The application of structural health monitoring (SHM) systems to civil engineering structures has been a developing studied and practiced topic, that has allowed for a better understanding of structures’ conditions and increasingly lead to a more cost-effective management of those infrastructures. In this field, the use of fiber optic sensors has been studied, discussed and practiced with encouraging results. The possibility of understanding and monitor the distributed behavior of extensive stretches of critical structures it’s an enormous advantage that distributed fiber optic sensing provides to SHM systems. In the past decade, several R & D studies have been performed with the goal of improving the knowledge and developing new techniques associated with the application of distributed optical fiber sensors (DOFS) in order to widen the range of applications of these sensors and also to obtain more correct and reliable data. This paper presents, after a brief introduction to the theoretical background of DOFS, the latest developments related with the improvement of these products by presenting a wide range of laboratory experiments as well as an extended review of their diverse applications in civil engineering structures. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Graphical abstract

Other

Jump to: Editorial, Research, Review

9 pages, 943 KiB

Open AccessLetter

A Precise Drunk Driving Detection Using Weighted Kernel Based on Electrocardiogram

by Chung Kit Wu, Kim Fung Tsang, Hao Ran Chi and Faan Hei Hung

Sensors 2016, 16(5), 659; https://doi.org/10.3390/s16050659 - 9 May 2016

Cited by 26 | Viewed by 6297

Abstract

Globally, 1.2 million people die and 50 million people are injured annually due to traffic accidents. These traffic accidents cost $500 billion dollars. Drunk drivers are found in 40% of the traffic crashes. Existing drunk driving detection (DDD) systems do not provide accurate [...] Read more.

Globally, 1.2 million people die and 50 million people are injured annually due to traffic accidents. These traffic accidents cost $500 billion dollars. Drunk drivers are found in 40% of the traffic crashes. Existing drunk driving detection (DDD) systems do not provide accurate detection and pre-warning concurrently. Electrocardiogram (ECG) is a proven biosignal that accurately and simultaneously reflects human’s biological status. In this letter, a classifier for DDD based on ECG is investigated in an attempt to reduce traffic accidents caused by drunk drivers. At this point, it appears that there is no known research or literature found on ECG classifier for DDD. To identify drunk syndromes, the ECG signals from drunk drivers are studied and analyzed. As such, a precise ECG-based DDD (ECG-DDD) using a weighted kernel is developed. From the measurements, 10 key features of ECG signals were identified. To incorporate the important features, the feature vectors are weighted in the customization of kernel functions. Four commonly adopted kernel functions are studied. Results reveal that weighted feature vectors improve the accuracy by 11% compared to the computation using the prime kernel. Evaluation shows that ECG-DDD improved the accuracy by 8% to 18% compared to prevailing methods. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures