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Open AccessEditorial Sensors: New Challenges in Spain

Sensors 2010, 10(5), 5028-5030; doi:10.3390/s100505028

Received: 6 April 2010 / Published: 19 May 2010

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Abstract

The main goal of this special issue was to explore sensor technology and its applications in Spain. It is well-known that a reciprocal interrelation exists between sensor technology and the demand for solutions to different problems. Indeed, when a new sensor is [...] Read more.

The main goal of this special issue was to explore sensor technology and its applications in Spain. It is well-known that a reciprocal interrelation exists between sensor technology and the demand for solutions to different problems. Indeed, when a new sensor is developed, it offers a solution to a problem, but also if a problem requires a solution perhaps new sensors or technologies based on existing sensors could be developed. [...] Full article

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

Research

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Open AccessArticle Diffused Matrix Format: A New Storage and Processing Format for Airborne Hyperspectral Sensor Images

by Pablo Martínez, Alejandro Cristo, Magaly Koch, Rosa Mª. Pérez, Thomas Schmid and Luz M. Hernández

Sensors 2010, 10(5), 4996-5013; doi:10.3390/s100504996

Received: 12 March 2010 / Revised: 27 April 2010 / Accepted: 6 May 2010 / Published: 18 May 2010

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Abstract

At present, hyperspectral images are mainly obtained with airborne sensors that are subject to turbulences while the spectrometer is acquiring the data. Therefore, geometric corrections are required to produce spatially correct images for visual interpretation and change detection analysis. This paper analyzes [...] Read more.

At present, hyperspectral images are mainly obtained with airborne sensors that are subject to turbulences while the spectrometer is acquiring the data. Therefore, geometric corrections are required to produce spatially correct images for visual interpretation and change detection analysis. This paper analyzes the data acquisition process of airborne sensors. The main objective is to propose a new data format called Diffused Matrix Format (DMF) adapted to the sensor's characteristics including its spectral and spatial information. The second objective is to compare the accuracy of the quantitative maps derived by using the DMF data structure with those obtained from raster images based on traditional data structures. Results show that DMF processing is more accurate and straightforward than conventional image processing of remotely sensed data with the advantage that the DMF file structure requires less storage space than other data formats. In addition the data processing time does not increase when DMF is used. Full article

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

Open AccessArticle State-of-the-Art Sensor Technology in Spain: Invasive and Non-Invasive Techniques for Monitoring Respiratory Variables

by Christian Domingo, Lluis Blanch, Gaston Murias and Manel Luján

Sensors 2010, 10(5), 4655-4674; doi:10.3390/s100504655

Received: 4 March 2010 / Revised: 29 March 2010 / Accepted: 15 April 2010 / Published: 5 May 2010

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Abstract

The interest in measuring physiological parameters (especially arterial blood gases) has grown progressively in parallel to the development of new technologies. Physiological parameters were first measured invasively and at discrete time points; however, it was clearly desirable to measure them continuously and [...] Read more.

The interest in measuring physiological parameters (especially arterial blood gases) has grown progressively in parallel to the development of new technologies. Physiological parameters were first measured invasively and at discrete time points; however, it was clearly desirable to measure them continuously and non-invasively. The development of intensive care units promoted the use of ventilators via oral intubation ventilators via oral intubation and mechanical respiratory variables were progressively studied. Later, the knowledge gained in the hospital was applied to out-of-hospital management. In the present paper we review the invasive and non-invasive techniques for monitoring respiratory variables. Full article

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

Open AccessArticle Decentralized Sensor Fusion for Ubiquitous Networking Robotics in Urban Areas

by Alberto Sanfeliu, Juan Andrade-Cetto, Marco Barbosa, Richard Bowden, Jesús Capitán, Andreu Corominas, Andrew Gilbert, John Illingworth, Luis Merino, Josep M. Mirats, Plínio Moreno, Aníbal Ollero, João Sequeira and Matthijs T. J. Spaan

Sensors 2010, 10(3), 2274-2314; doi:10.3390/s100302274

Received: 12 January 2010 / Revised: 2 February 2010 / Accepted: 28 February 2010 / Published: 19 March 2010

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Abstract

In this article we explain the architecture for the environment and sensors that has been built for the European project URUS (Ubiquitous Networking Robotics in Urban Sites), a project whose objective is to develop an adaptable network robot architecture for cooperation between [...] Read more.

In this article we explain the architecture for the environment and sensors that has been built for the European project URUS (Ubiquitous Networking Robotics in Urban Sites), a project whose objective is to develop an adaptable network robot architecture for cooperation between network robots and human beings and/or the environment in urban areas. The project goal is to deploy a team of robots in an urban area to give a set of services to a user community. This paper addresses the sensor architecture devised for URUS and the type of robots and sensors used, including environment sensors and sensors onboard the robots. Furthermore, we also explain how sensor fusion takes place to achieve urban outdoor execution of robotic services. Finally some results of the project related to the sensor network are highlighted. Full article

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

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Open AccessArticle Concurrent Initialization for Bearing-Only SLAM

by Rodrigo Munguía and Antoni Grau

Sensors 2010, 10(3), 1511-1534; doi:10.3390/s100301511

Received: 18 December 2009 / Revised: 15 February 2010 / Accepted: 24 February 2010 / Published: 1 March 2010

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Abstract

Simultaneous Localization and Mapping (SLAM) is perhaps the most fundamental problem to solve in robotics in order to build truly autonomous mobile robots. The sensors have a large impact on the algorithm used for SLAM. Early SLAM approaches focused on the use [...] Read more.

Simultaneous Localization and Mapping (SLAM) is perhaps the most fundamental problem to solve in robotics in order to build truly autonomous mobile robots. The sensors have a large impact on the algorithm used for SLAM. Early SLAM approaches focused on the use of range sensors as sonar rings or lasers. However, cameras have become more and more used, because they yield a lot of information and are well adapted for embedded systems: they are light, cheap and power saving. Unlike range sensors which provide range and angular information, a camera is a projective sensor which measures the bearing of images features. Therefore depth information (range) cannot be obtained in a single step. This fact has propitiated the emergence of a new family of SLAM algorithms: the Bearing-Only SLAM methods, which mainly rely in especial techniques for features system-initialization in order to enable the use of bearing sensors (as cameras) in SLAM systems. In this work a novel and robust method, called Concurrent Initialization, is presented which is inspired by having the complementary advantages of the Undelayed and Delayed methods that represent the most common approaches for addressing the problem. The key is to use concurrently two kinds of feature representations for both undelayed and delayed stages of the estimation. The simulations results show that the proposed method surpasses the performance of previous schemes. Full article

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

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Open AccessArticle Evaluating the Consistency of the 1982–1999 NDVI Trends in the Iberian Peninsula across Four Time-series Derived from the AVHRR Sensor: LTDR, GIMMS, FASIR, and PAL-II

by Domingo Alcaraz-Segura, Elisa Liras, Siham Tabik, José Paruelo and Javier Cabello

Sensors 2010, 10(2), 1291-1314; doi:10.3390/s100201291

Received: 30 December 2009 / Revised: 14 January 2010 / Accepted: 19 January 2010 / Published: 8 February 2010

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Abstract

Successive efforts have processed the Advanced Very High Resolution Radiometer (AVHRR) sensor archive to produce Normalized Difference Vegetation Index (NDVI) datasets (i.e., PAL, FASIR, GIMMS, and LTDR) under different corrections and processing schemes. Since NDVI datasets are used to evaluate [...] Read more.

Successive efforts have processed the Advanced Very High Resolution Radiometer (AVHRR) sensor archive to produce Normalized Difference Vegetation Index (NDVI) datasets (i.e., PAL, FASIR, GIMMS, and LTDR) under different corrections and processing schemes. Since NDVI datasets are used to evaluate carbon gains, differences among them may affect nations’ carbon budgets in meeting international targets (such as the Kyoto Protocol). This study addresses the consistency across AVHRR NDVI datasets in the Iberian Peninsula (Spain and Portugal) by evaluating whether their 1982–1999 NDVI trends show similar spatial patterns. Significant trends were calculated with the seasonal Mann-Kendall trend test and their spatial consistency with partial Mantel tests. Over 23% of the Peninsula (N, E, and central mountain ranges) showed positive and significant NDVI trends across the four datasets and an additional 18% across three datasets. In 20% of Iberia (SW quadrant), the four datasets exhibited an absence of significant trends and an additional 22% across three datasets. Significant NDVI decreases were scarce (croplands in the Guadalquivir and Segura basins, La Mancha plains, and Valencia). Spatial consistency of significant trends across at least three datasets was observed in 83% of the Peninsula, but it decreased to 47% when comparing across the four datasets. FASIR, PAL, and LTDR were the most spatially similar datasets, while GIMMS was the most different. The different performance of each AVHRR dataset to detect significant NDVI trends (e.g., LTDR detected greater significant trends (both positive and negative) and in 32% more pixels than GIMMS) has great implications to evaluate carbon budgets. The lack of spatial consistency across NDVI datasets derived from the same AVHRR sensor archive, makes it advisable to evaluate carbon gains trends using several satellite datasets and, whether possible, independent/additional data sources to contrast. Full article

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

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Open AccessArticle A Device for Automatically Measuring and Supervising the Critical Care Patient’S Urine Output

by Abraham Otero, Francisco Palacios, Teodor Akinfiev and Roemi Fernández

Sensors 2010, 10(1), 934-951; doi:10.3390/s100100934

Received: 14 December 2009 / Revised: 15 January 2010 / Accepted: 18 January 2010 / Published: 26 January 2010

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Abstract

Critical care units are equipped with commercial monitoring devices capable of sensing patients’ physiological parameters and supervising the achievement of the established therapeutic goals. This avoids human errors in this task and considerably decreases the workload of the healthcare staff. However, at [...] Read more.

Critical care units are equipped with commercial monitoring devices capable of sensing patients’ physiological parameters and supervising the achievement of the established therapeutic goals. This avoids human errors in this task and considerably decreases the workload of the healthcare staff. However, at present there still is a very relevant physiological parameter that is measured and supervised manually by the critical care units’ healthcare staff: urine output. This paper presents a patent-pending device capable of automatically recording and supervising the urine output of a critical care patient. A high precision scale is used to measure the weight of a commercial urine meter. On the scale’s pan there is a support frame made up of Bosch profiles that isolates the scale from force transmission from the patient’s bed, and guarantees that the urine flows properly through the urine meter input tube. The scale’s readings are sent to a PC via Bluetooth where an application supervises the achievement of the therapeutic goals. The device is currently undergoing tests at a research unit associated with the University Hospital of Getafe in Spain. Full article

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

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Open AccessArticle An Efficient Pipeline Wavefront Phase Recovery for the CAFADIS Camera for Extremely Large Telescopes

by Eduardo Magdaleno, Manuel Rodríguez and José Manuel Rodríguez-Ramos

Sensors 2010, 10(1), 1-15; doi:10.3390/s100100001

Received: 30 November 2009 / Revised: 22 December 2009 / Accepted: 23 December 2009 / Published: 24 December 2009

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Abstract

In this paper we show a fast, specialized hardware implementation of the wavefront phase recovery algorithm using the CAFADIS camera. The CAFADIS camera is a new plenoptic sensor patented by the Universidad de La Laguna (Canary Islands, Spain): international patent PCT/ES2007/000046 (WIPO [...] Read more.

In this paper we show a fast, specialized hardware implementation of the wavefront phase recovery algorithm using the CAFADIS camera. The CAFADIS camera is a new plenoptic sensor patented by the Universidad de La Laguna (Canary Islands, Spain): international patent PCT/ES2007/000046 (WIPO publication number WO/2007/082975). It can simultaneously measure the wavefront phase and the distance to the light source in a real-time process. The pipeline algorithm is implemented using Field Programmable Gate Arrays (FPGA). These devices present architecture capable of handling the sensor output stream using a massively parallel approach and they are efficient enough to resolve several Adaptive Optics (AO) problems in Extremely Large Telescopes (ELTs) in terms of processing time requirements. The FPGA implementation of the wavefront phase recovery algorithm using the CAFADIS camera is based on the very fast computation of two dimensional fast Fourier Transforms (FFTs). Thus we have carried out a comparison between our very novel FPGA 2D-FFTa and other implementations. Full article

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

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Open AccessArticle A Focusing Method in the Calibration Process of Image Sensors Based on IOFBs

by Pedro R. Fernández, José L. Lázaro, Alfredo Gardel, Ángel E. Cano and Ignacio Bravo

Sensors 2010, 10(1), 47-60; doi:10.3390/s100100047

Received: 29 October 2009 / Revised: 14 November 2009 / Accepted: 27 November 2009 / Published: 24 December 2009

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Abstract

A focusing procedure in the calibration process of image sensors based on Incoherent Optical Fiber Bundles (IOFBs) is described using the information extracted from fibers. These procedures differ from any other currently known focusing method due to the non spatial in-out correspondence [...] Read more.

A focusing procedure in the calibration process of image sensors based on Incoherent Optical Fiber Bundles (IOFBs) is described using the information extracted from fibers. These procedures differ from any other currently known focusing method due to the non spatial in-out correspondence between fibers, which produces a natural codification of the image to transmit. Focus measuring is essential prior to carrying out calibration in order to guarantee accurate processing and decoding. Four algorithms have been developed to estimate the focus measure; two methods based on mean grey level, and the other two based on variance. In this paper, a few simple focus measures are defined and compared. Some experimental results referred to the focus measure and the accuracy of the developed methods are discussed in order to demonstrate its effectiveness. Full article

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

Open AccessArticle A Cluster-Based Architecture to Structure the Topology of Parallel Wireless Sensor Networks

by Jaime Lloret, Miguel Garcia, Diana Bri and Juan R. Diaz

Sensors 2009, 9(12), 10513-10544; doi:10.3390/s91210513

Received: 23 November 2009 / Revised: 2 December 2009 / Accepted: 10 December 2009 / Published: 23 December 2009

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Abstract

A wireless sensor network is a self-configuring network of mobile nodes connected by wireless links where the nodes have limited capacity and energy. In many cases, the application environment requires the design of an exclusive network topology for a particular case. Cluster-based [...] Read more.

A wireless sensor network is a self-configuring network of mobile nodes connected by wireless links where the nodes have limited capacity and energy. In many cases, the application environment requires the design of an exclusive network topology for a particular case. Cluster-based network developments and proposals in existence have been designed to build a network for just one type of node, where all nodes can communicate with any other nodes in their coverage area. Let us suppose a set of clusters of sensor nodes where each cluster is formed by different types of nodes (e.g., they could be classified by the sensed parameter using different transmitting interfaces, by the node profile or by the type of device: laptops, PDAs, sensor etc.) and exclusive networks, as virtual networks, are needed with the same type of sensed data, or the same type of devices, or even the same type of profiles. In this paper, we propose an algorithm that is able to structure the topology of different wireless sensor networks to coexist in the same environment. It allows control and management of the topology of each network. The architecture operation and the protocol messages will be described. Measurements from a real test-bench will show that the designed protocol has low bandwidth consumption and also demonstrates the viability and the scalability of the proposed architecture. Our ccluster-based algorithm is compared with other algorithms reported in the literature in terms of architecture and protocol measurements. Full article

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

Open AccessArticle Field Measurements and Guidelines for the Application of Wireless Sensor Networks to the Environment and Security

by Víctor P. Gil Jiménez and Ana García Armada

Sensors 2009, 9(12), 10309-10325; doi:10.3390/s91210309

Received: 23 November 2009 / Revised: 4 December 2009 / Accepted: 7 December 2009 / Published: 18 December 2009

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Abstract

Frequently, Wireless Sensor Networks (WSN) are designed focusing on applications and omitting transmission problems in these wireless networks. In this paper, we present a measurement campaign that has been carried out using one of the most commonly used WSN platforms, the micaZ [...] Read more.

Frequently, Wireless Sensor Networks (WSN) are designed focusing on applications and omitting transmission problems in these wireless networks. In this paper, we present a measurement campaign that has been carried out using one of the most commonly used WSN platforms, the micaZ from Crossbow^© . Based on these measurements, some guidelines to deploy a robust and reliable WSN are provided. The results are focused on security and environmental applications but can also be extrapolated to other scenarios. A main conclusion that can be extracted is that, from the transmission point of view, a dense WSN is one of the best choices to overcome many of the transmission problems such as the existence of a transitional region, redundance, forwarding, obstructions or interference with other systems. Full article

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

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Open AccessArticle Sonar Sensor Models and Their Application to Mobile Robot Localization

by Antoni Burguera, Yolanda González and Gabriel Oliver

Sensors 2009, 9(12), 10217-10243; doi:10.3390/s91210217

Received: 2 November 2009 / Revised: 18 November 2009 / Accepted: 14 December 2009 / Published: 17 December 2009

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Abstract

This paper presents a novel approach to mobile robot localization using sonar sensors. This approach is based on the use of particle filters. Each particle is augmented with local environment information which is updated during the mission execution. An experimental characterization of [...] Read more.

This paper presents a novel approach to mobile robot localization using sonar sensors. This approach is based on the use of particle filters. Each particle is augmented with local environment information which is updated during the mission execution. An experimental characterization of the sonar sensors used is provided in the paper. A probabilistic measurement model that takes into account the sonar uncertainties is defined according to the experimental characterization. The experimental results quantitatively evaluate the presented approach and provide a comparison with other localization strategies based on both the sonar and the laser. Some qualitative results are also provided for visual inspection. Full article

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

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Open AccessArticle A Multi-Agent System Architecture for Sensor Networks

by Rubén Fuentes-Fernández, María Guijarro and Gonzalo Pajares

Sensors 2009, 9(12), 10244-10269; doi:10.3390/s91210244

Received: 13 October 2009 / Revised: 4 December 2009 / Accepted: 8 December 2009 / Published: 17 December 2009

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Abstract

The design of the control systems for sensor networks presents important challenges. Besides the traditional problems about how to process the sensor data to obtain the target information, engineers need to consider additional aspects such as the heterogeneity and high number of [...] Read more.

The design of the control systems for sensor networks presents important challenges. Besides the traditional problems about how to process the sensor data to obtain the target information, engineers need to consider additional aspects such as the heterogeneity and high number of sensors, and the flexibility of these networks regarding topologies and the sensors in them. Although there are partial approaches for resolving these issues, their integration relies on ad hoc solutions requiring important development efforts. In order to provide an effective approach for this integration, this paper proposes an architecture based on the multi-agent system paradigm with a clear separation of concerns. The architecture considers sensors as devices used by an upper layer of manager agents. These agents are able to communicate and negotiate services to achieve the required functionality. Activities are organized according to roles related with the different aspects to integrate, mainly sensor management, data processing, communication and adaptation to changes in the available devices and their capabilities. This organization largely isolates and decouples the data management from the changing network, while encouraging reuse of solutions. The use of the architecture is facilitated by a specific modelling language developed through metamodelling. A case study concerning a generic distributed system for fire fighting illustrates the approach and the comparison with related work. Full article

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

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Open AccessArticle Distance and Cable Length Measurement System

by Sergio Elias Hernández, Leopoldo Acosta and Jonay Toledo

Sensors 2009, 9(12), 10190-10200; doi:10.3390/s91210190

Received: 30 October 2009 / Revised: 2 December 2009 / Accepted: 7 December 2009 / Published: 16 December 2009

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Abstract

A simple, economic and successful design for distance and cable length detection is presented. The measurement system is based on the continuous repetition of a pulse that endlessly travels along the distance to be detected. There is a pulse repeater at both [...] Read more.

A simple, economic and successful design for distance and cable length detection is presented. The measurement system is based on the continuous repetition of a pulse that endlessly travels along the distance to be detected. There is a pulse repeater at both ends of the distance or cable to be measured. The endless repetition of the pulse generates a frequency that varies almost inversely with the distance to be measured. The resolution and distance or cable length range could be adjusted by varying the repetition time delay introduced at both ends and the measurement time. With this design a distance can be measured with centimeter resolution using electronic system with microsecond resolution, simplifying classical time of flight designs which require electronics with picosecond resolution. This design was also applied to position measurement. Full article

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

Open AccessArticle Remote Sensing and Skywave Digital Communication from Antarctica

by Pau Bergadà, Marc Deumal, Carles Vilella, Joan R. Regué, David Altadill and Santi Marsal

Sensors 2009, 9(12), 10136-10157; doi:10.3390/s91210136

Received: 16 October 2009 / Revised: 30 November 2009 / Accepted: 7 December 2009 / Published: 14 December 2009

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Abstract

This paper presents an overview of the research activities undertaken by La Salle and the Ebro Observatory in the field of remote sensing. On 2003 we started a research project with two main objectives: implement a long-haul oblique ionospheric sounder and transmit [...] Read more.

This paper presents an overview of the research activities undertaken by La Salle and the Ebro Observatory in the field of remote sensing. On 2003 we started a research project with two main objectives: implement a long-haul oblique ionospheric sounder and transmit the data from remote sensors located at the Spanish Antarctic station Juan Carlos I to Spain. The paper focuses on a study of feasibility of two possible physical layer candidates for the skywave link between both points. A DS-SS based solution and an OFDM based solution are considered to achieve a reliable low-power low-rate communication system between Antarctica and Spain. Full article

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

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Open AccessArticle New Passive Instruments Developed for Ocean Monitoring at the Remote Sensing Lab—Universitat Politècnica de Catalunya

by Adriano Camps, Xavier Bosch-Lluis, Isaac Ramos-Perez, Juan F. Marchán-Hernández, Nereida Rodríguez, Enric Valencia, Jose M. Tarongi, Albert Aguasca and René Acevo

Sensors 2009, 9(12), 10171-10189; doi:10.3390/s91210171

Received: 12 November 2009 / Revised: 24 November 2009 / Accepted: 25 November 2009 / Published: 14 December 2009

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Abstract

Lack of frequent and global observations from space is currently a limiting factor in many Earth Observation (EO) missions. Two potential techniques that have been proposed nowadays are: (1) the use of satellite constellations, and (2) the use of Global Navigation Satellite [...] Read more.

Lack of frequent and global observations from space is currently a limiting factor in many Earth Observation (EO) missions. Two potential techniques that have been proposed nowadays are: (1) the use of satellite constellations, and (2) the use of Global Navigation Satellite Signals (GNSS) as signals of opportunity (no transmitter required). Reflectometry using GNSS opportunity signals (GNSS-R) was originally proposed in 1993 by Martin-Neira (ESA-ESTEC) for altimetry applications, but later its use for wind speed determination has been proposed, and more recently to perform the sea state correction required in sea surface salinity retrievals by means of L-band microwave radiometry (T_B). At present, two EO space-borne missions are currently planned to be launched in the near future: (1) ESA’s SMOS mission, using a Y-shaped synthetic aperture radiometer, launch date November 2nd, 2009, and (2) NASA-CONAE AQUARIUS/SAC-D mission, using a three beam push-broom radiometer. In the SMOS mission, the multi-angle observation capabilities allow to simultaneously retrieve not only the surface salinity, but also the surface temperature and an “effective” wind speed that minimizes the differences between observations and models. In AQUARIUS, an L-band scatterometer measuring the radar backscatter (σ₀) will be used to perform the necessary sea state corrections. However, none of these approaches are fully satisfactory, since the effective wind speed captures some sea surface roughness effects, at the expense of introducing another variable to be retrieved, and on the other hand the plots (T_B-σ₀) present a large scattering. In 2003, the Passive Advance Unit for ocean monitoring (PAU) project was proposed to the European Science Foundation in the frame of the EUropean Young Investigator Awards (EURYI) to test the feasibility of GNSS-R over the sea surface to make sea state measurements and perform the correction of the L-band brightness temperature. This paper: (1) provides an overview of the Physics of the L-band radiometric and GNSS reflectometric observations over the ocean, (2) describes the instrumentation that has been (is being) developed in the frame of the EURYI-funded PAU project, (3) the ground-based measurements carried out so far, and their interpretation in view of placing a GNSS-reflectometer as secondary payload in future SMOS follow-on missions. Full article

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

Open AccessArticle A Neuro-Fuzzy System for Extracting Environment Features Based on Ultrasonic Sensors

by Graciliano Nicolás Marichal, Angela Hernández, Leopoldo Acosta and Evelio José González

Sensors 2009, 9(12), 10023-10043; doi:10.3390/s91210023

Received: 4 November 2009 / Revised: 23 November 2009 / Accepted: 30 November 2009 / Published: 9 December 2009

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Abstract

In this paper, a method to extract features of the environment based on ultrasonic sensors is presented. A 3D model of a set of sonar systems and a workplace has been developed. The target of this approach is to extract in a [...] Read more.

In this paper, a method to extract features of the environment based on ultrasonic sensors is presented. A 3D model of a set of sonar systems and a workplace has been developed. The target of this approach is to extract in a short time, while the vehicle is moving, features of the environment. Particularly, the approach shown in this paper has been focused on determining walls and corners, which are very common environment features. In order to prove the viability of the devised approach, a 3D simulated environment has been built. A Neuro-Fuzzy strategy has been used in order to extract environment features from this simulated model. Several trials have been carried out, obtaining satisfactory results in this context. After that, some experimental tests have been conducted using a real vehicle with a set of sonar systems. The obtained results reveal the satisfactory generalization properties of the approach in this case. Full article

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

Open AccessArticle A Featured-Based Strategy for Stereovision Matching in Sensors with Fish-Eye Lenses for Forest Environments

by Pedro Javier Herrera, Gonzalo Pajares, Maria Guijarro, José J. Ruz, Jesús M. Cruz and Fernando Montes

Sensors 2009, 9(12), 9468-9492; doi:10.3390/s91209468

Received: 23 September 2009 / Revised: 30 October 2009 / Accepted: 16 November 2009 / Published: 26 November 2009

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Abstract

This paper describes a novel feature-based stereovision matching process based on a pair of omnidirectional images in forest stands acquired with a stereovision sensor equipped with fish-eye lenses. The stereo analysis problem consists of the following steps: image acquisition, camera modelling, feature [...] Read more.

This paper describes a novel feature-based stereovision matching process based on a pair of omnidirectional images in forest stands acquired with a stereovision sensor equipped with fish-eye lenses. The stereo analysis problem consists of the following steps: image acquisition, camera modelling, feature extraction, image matching and depth determination. Once the depths of significant points on the trees are obtained, the growing stock volume can be estimated by considering the geometrical camera modelling, which is the final goal. The key steps are feature extraction and image matching. This paper is devoted solely to these two steps. At a first stage a segmentation process extracts the trunks, which are the regions used as features, where each feature is identified through a set of attributes of properties useful for matching. In the second step the features are matched based on the application of the following four well known matching constraints, epipolar, similarity, ordering and uniqueness. The combination of the segmentation and matching processes for this specific kind of sensors make the main contribution of the paper. The method is tested with satisfactory results and compared against the human expert criterion. Full article

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

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Open AccessArticle Acoustic Sensor Planning for Gunshot Location in National Parks: A Pareto Front Approach

by Francisco Javier González-Castaño, Javier Vales Alonso, Enrique Costa-Montenegro, Pablo López-Matencio, Francisco Vicente-Carrasco, Francisco J. Parrado-García, Felipe Gil-Castiñeira and Sergio Costas-Rodríguez

Sensors 2009, 9(12), 9493-9512; doi:10.3390/91209493

Received: 9 October 2009 / Revised: 13 November 2009 / Accepted: 16 November 2009 / Published: 26 November 2009

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Abstract

In this paper, we propose a solution for gunshot location in national parks. In Spain there are agencies such as SEPRONA that fight against poaching with considerable success. The DiANa project, which is endorsed by Cabañeros National Park and the SEPRONA service, [...] Read more.

In this paper, we propose a solution for gunshot location in national parks. In Spain there are agencies such as SEPRONA that fight against poaching with considerable success. The DiANa project, which is endorsed by Cabañeros National Park and the SEPRONA service, proposes a system to automatically detect and locate gunshots. This work presents its technical aspects related to network design and planning. The system consists of a network of acoustic sensors that locate gunshots by hyperbolic multi-lateration estimation. The differences in sound time arrivals allow the computation of a low error estimator of gunshot location. The accuracy of this method depends on tight sensor clock synchronization, which an ad-hoc time synchronization protocol provides. On the other hand, since the areas under surveillance are wide, and electric power is scarce, it is necessary to maximize detection coverage and minimize system cost at the same time. Therefore, sensor network planning has two targets, i.e., coverage and cost. We model planning as an unconstrained problem with two objective functions. We determine a set of candidate solutions of interest by combining a derivative-free descent method we have recently proposed with a Pareto front approach. The results are clearly superior to random seeding in a realistic simulation scenario. Full article

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

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Open AccessArticle Improving Security for SCADA Sensor Networks with Reputation Systems and Self-Organizing Maps

by José M. Moya, Álvaro Araujo, Zorana Banković, Juan-Mariano De Goyeneche, Juan Carlos Vallejo, Pedro Malagón, Daniel Villanueva, David Fraga, Elena Romero and Javier Blesa

Sensors 2009, 9(11), 9380-9397; doi:10.3390/s91109380

Received: 9 October 2009 / Revised: 30 October 2009 / Accepted: 4 November 2009 / Published: 20 November 2009

Cited by 16 | PDF Full-text (644 KB) | HTML Full-text | XML Full-text

Abstract

The reliable operation of modern infrastructures depends on computerized systems and Supervisory Control and Data Acquisition (SCADA) systems, which are also based on the data obtained from sensor networks. The inherent limitations of the sensor devices make them extremely vulnerable to cyberwarfare/cyberterrorism [...] Read more.

The reliable operation of modern infrastructures depends on computerized systems and Supervisory Control and Data Acquisition (SCADA) systems, which are also based on the data obtained from sensor networks. The inherent limitations of the sensor devices make them extremely vulnerable to cyberwarfare/cyberterrorism attacks. In this paper, we propose a reputation system enhanced with distributed agents, based on unsupervised learning algorithms (self-organizing maps), in order to achieve fault tolerance and enhanced resistance to previously unknown attacks. This approach has been extensively simulated and compared with previous proposals. Full article

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

Open AccessArticle Testing Multivariate Adaptive Regression Splines (MARS) as a Method of Land Cover Classification of TERRA-ASTER Satellite Images

by Elia Quirós, Ángel M. Felicísimo and Aurora Cuartero

Sensors 2009, 9(11), 9011-9028; doi:10.3390/s91109011

Received: 24 September 2009 / Revised: 1 November 2009 / Accepted: 2 November 2009 / Published: 13 November 2009

Cited by 13 | PDF Full-text (639 KB) | HTML Full-text | XML Full-text

Abstract

This work proposes a new method to classify multi-spectral satellite images based on multivariate adaptive regression splines (MARS) and compares this classification system with the more common parallelepiped and maximum likelihood (ML) methods. We apply the classification methods to the land cover [...] Read more.

This work proposes a new method to classify multi-spectral satellite images based on multivariate adaptive regression splines (MARS) and compares this classification system with the more common parallelepiped and maximum likelihood (ML) methods. We apply the classification methods to the land cover classification of a test zone located in southwestern Spain. The basis of the MARS method and its associated procedures are explained in detail, and the area under the ROC curve (AUC) is compared for the three methods. The results show that the MARS method provides better results than the parallelepiped method in all cases, and it provides better results than the maximum likelihood method in 13 cases out of 17. These results demonstrate that the MARS method can be used in isolation or in combination with other methods to improve the accuracy of soil cover classification. The improvement is statistically significant according to the Wilcoxon signed rank test. Full article

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

Open AccessArticle A Robust Head Tracking System Based on Monocular Vision and Planar Templates

by Fernando Caballero, Iván Maza, Roberto Molina, David Esteban and Aníbal Ollero

Sensors 2009, 9(11), 8924-8943; doi:10.3390/s91108924

Received: 7 September 2009 / Revised: 9 October 2009 / Accepted: 15 October 2009 / Published: 11 November 2009

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Abstract

This paper details the implementation of a head tracking system suitable for its use in teleoperation stations or control centers, taking into account the limitations and constraints usually associated to those environments. The paper discusses and justifies the selection of the different [...] Read more.

This paper details the implementation of a head tracking system suitable for its use in teleoperation stations or control centers, taking into account the limitations and constraints usually associated to those environments. The paper discusses and justifies the selection of the different methods and sensors to build the head tracking system, detailing also the processing steps of the system in operation. A prototype to validate the proposed approach is also presented along with several tests in a real environment with promising results. Full article

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

Open AccessArticle Sensor for Distance Measurement Using Pixel Grey-Level Information

by José L. Lázaro, Angel E. Cano, Pedro R. Fernández and Yamilet Pompa

Sensors 2009, 9(11), 8896-8906; doi:10.3390/s91108896

Received: 30 September 2009 / Revised: 29 October 2009 / Accepted: 4 November 2009 / Published: 6 November 2009

Cited by 6 | PDF Full-text (303 KB) | HTML Full-text | XML Full-text

Abstract

An alternative method for distance measurement is presented, based on a radiometric approach to the image formation process. The proposed methodology uses images from an infrared emitting diode (IRED) to estimate the distance between the camera and the IRED. Camera output grey-level [...] Read more.

An alternative method for distance measurement is presented, based on a radiometric approach to the image formation process. The proposed methodology uses images from an infrared emitting diode (IRED) to estimate the distance between the camera and the IRED. Camera output grey-level intensities are a function of the accumulated image irradiance, which is also related by inverse distance square law to the distance between the camera and the IRED. Analyzing camera-IRED distance, magnitudes that affected image grey-level intensities, and therefore accumulated image irradiance, were integrated into a differential model which was calibrated and used for distance estimation over a 200 to 600 cm range. In a preliminary model, the camera and the emitter were aligned. Full article

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

Open AccessArticle A Wireless Sensor Network Deployment for Rural and Forest Fire Detection and Verification

by Jaime Lloret, Miguel Garcia, Diana Bri and Sandra Sendra

Sensors 2009, 9(11), 8722-8747; doi:10.3390/s91108722

Received: 29 September 2009 / Revised: 15 October 2009 / Accepted: 20 October 2009 / Published: 30 October 2009

Cited by 77 | PDF Full-text (2286 KB) | HTML Full-text | XML Full-text

Abstract

Forest and rural fires are one of the main causes of environmental degradation in Mediterranean countries. Existing fire detection systems only focus on detection, but not on the verification of the fire. However, almost all of them are just simulations, and very [...] Read more.

Forest and rural fires are one of the main causes of environmental degradation in Mediterranean countries. Existing fire detection systems only focus on detection, but not on the verification of the fire. However, almost all of them are just simulations, and very few implementations can be found. Besides, the systems in the literature lack scalability. In this paper we show all the steps followed to perform the design, research and development of a wireless multisensor network which mixes sensors with IP cameras in a wireless network in order to detect and verify fire in rural and forest areas of Spain. We have studied how many cameras, sensors and access points are needed to cover a rural or forest area, and the scalability of the system. We have developed a multisensor and when it detects a fire, it sends a sensor alarm through the wireless network to a central server. The central server selects the closest wireless cameras to the multisensor, based on a software application, which are rotated to the sensor that raised the alarm, and sends them a message in order to receive real-time images from the zone. The camera lets the fire fighters corroborate the existence of a fire and avoid false alarms. In this paper, we show the test performance given by a test bench formed by four wireless IP cameras in several situations and the energy consumed when they are transmitting. Moreover, we study the energy consumed by each device when the system is set up. The wireless sensor network could be connected to Internet through a gateway and the images of the cameras could be seen from any part of the world. Full article

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

Open AccessArticle A Topology Reorganization Scheme for Reliable Communication in Underwater Wireless Sensor Networks Affected by Shadow Zones

by Mari Carmen Domingo

Sensors 2009, 9(11), 8684-8708; doi:10.3390/s91108684

Received: 31 August 2009 / Revised: 8 October 2009 / Accepted: 19 October 2009 / Published: 29 October 2009

Cited by 7 | PDF Full-text (2590 KB) | HTML Full-text | XML Full-text

Abstract

Effective solutions should be devised to handle the effects of shadow zones in Underwater Wireless Sensor Networks (UWSNs). An adaptive topology reorganization scheme that maintains connectivity in multi-hop UWSNs affected by shadow zones has been developed in the context of two Spanish-funded [...] Read more.

Effective solutions should be devised to handle the effects of shadow zones in Underwater Wireless Sensor Networks (UWSNs). An adaptive topology reorganization scheme that maintains connectivity in multi-hop UWSNs affected by shadow zones has been developed in the context of two Spanish-funded research projects. A mathematical model has been proposed to find the optimal location for sensors with two objectives: the minimization of the transmission loss and the maintenance of network connectivity. The theoretical analysis and the numerical evaluations reveal that our scheme reduces the transmission loss under all propagation phenomena scenarios for all water depths in UWSNs and improves the signal-to-noise ratio. Full article

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

Open AccessArticle Acoustic Sensor Network for Relative Positioning of Nodes

by Carlos De Marziani, Jesus Ureña, Álvaro Hernandez, Manuel Mazo, Juan Jesús García, Ana Jimenez, M. Carmen Pérez Rubio, Fernando Álvarez and José Manuel Villadangos

Sensors 2009, 9(11), 8490-8507; doi:10.3390/s91108490

Received: 17 August 2009 / Revised: 21 September 2009 / Accepted: 15 October 2009 / Published: 27 October 2009

Cited by 13 | PDF Full-text (833 KB) | HTML Full-text | XML Full-text

Abstract

In this work, an acoustic sensor network for a relative localization system is analyzed by reporting the accuracy achieved in the position estimation. The proposed system has been designed for those applications where objects are not restricted to a particular environment and [...] Read more.

In this work, an acoustic sensor network for a relative localization system is analyzed by reporting the accuracy achieved in the position estimation. The proposed system has been designed for those applications where objects are not restricted to a particular environment and thus one cannot depend on any external infrastructure to compute their positions. The objects are capable of computing spatial relations among themselves using only acoustic emissions as a ranging mechanism. The object positions are computed by a multidimensional scaling (MDS) technique and, afterwards, a least-square algorithm, based on the Levenberg-Marquardt algorithm (LMA), is applied to refine results. Regarding the position estimation, all the parameters involved in the computation of the temporary relations with the proposed ranging mechanism have been considered. The obtained results show that a fine-grained localization can be achieved considering a Gaussian distribution error in the proposed ranging mechanism. Furthermore, since acoustic sensors require a line-of-sight to properly work, the system has been tested by modeling the lost of this line-of-sight as a non-Gaussian error. A suitable position estimation has been achieved even if it is considered a bias of up to 25 of the line-of-sight measurements among a set of nodes. Full article

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

Open AccessArticle A Distributed Sensor Network for the Control of a Bioclimatic House in Spain

by Álvaro Gutiérrez, Javier Jiménez-Leube and Luis Magdalena

Sensors 2009, 9(10), 8197-8214; doi:10.3390/s91008197

Received: 11 June 2009 / Revised: 5 October 2009 / Accepted: 12 October 2009 / Published: 19 October 2009

Cited by 6 | PDF Full-text (1408 KB) | HTML Full-text | XML Full-text

Abstract

The XXI century home should be a digital habitat, a connected residence, but at the same time it should be involved in sustainability and the environment. The location of new technologies at home, and its acceptance by the user, requires, among other [...] Read more.

The XXI century home should be a digital habitat, a connected residence, but at the same time it should be involved in sustainability and the environment. The location of new technologies at home, and its acceptance by the user, requires, among other actions, a significant diffusion and activity to be undertaken. This work proposes the development of a Smart House network designed for its integration into a sustainable and bioclimatic solar house. The paper focuses on a specific aspect of the house design, the control system bus, developed for the management of the different parameters, variables, sensors and actuators which coexist at home. Finally, the system has been installed in a laboratory bioclimatic house. Environmental variable experiments based on the control of passive elements, such as phase shift gels, are presented. Experimental results show that the system is able to benefit from the bioclimatic elements in the house by taking into account the user preferences. Full article

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

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Open AccessArticle A Real-Time Tool Positioning Sensor for Machine-Tools

by Antonio Ramon Jimenez Ruiz, Jorge Guevara Rosas, Fernando Seco Granja, Jose Carlos Prieto Honorato, Jose Juan Esteve Taboada, Vicente Mico Serrano and Teresa Molina Jimenez

Sensors 2009, 9(10), 7622-7647; doi:10.3390/s91007622

Received: 4 August 2009 / Revised: 2 September 2009 / Accepted: 3 September 2009 / Published: 28 September 2009

Cited by 8 | PDF Full-text (3201 KB) | HTML Full-text | XML Full-text

Abstract

In machining, natural oscillations, and elastic, gravitational or temperature deformations, are still a problem to guarantee the quality of fabricated parts. In this paper we present an optical measurement system designed to track and localize in 3D a reference retro-reflector close to [...] Read more.

In machining, natural oscillations, and elastic, gravitational or temperature deformations, are still a problem to guarantee the quality of fabricated parts. In this paper we present an optical measurement system designed to track and localize in 3D a reference retro-reflector close to the machine-tool’s drill. The complete system and its components are described in detail. Several tests, some static (including impacts and rotations) and others dynamic (by executing linear and circular trajectories), were performed on two different machine tools. It has been integrated, for the first time, a laser tracking system into the position control loop of a machine-tool. Results indicate that oscillations and deformations close to the tool can be estimated with micrometric resolution and a bandwidth from 0 to more than 100 Hz. Therefore this sensor opens the possibility for on-line compensation of oscillations and deformations. Full article

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

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Open AccessArticle Multi-Unmanned Aerial Vehicle (UAV) Cooperative Fault Detection Employing Differential Global Positioning (DGPS), Inertial and Vision Sensors

by Guillermo Heredia, Fernando Caballero, Iván Maza, Luis Merino, Antidio Viguria and Aníbal Ollero

Sensors 2009, 9(9), 7566-7579; doi:10.3390/s90907566

Received: 26 August 2009 / Revised: 14 September 2009 / Accepted: 21 September 2009 / Published: 24 September 2009

Cited by 23 | PDF Full-text (530 KB) | HTML Full-text | XML Full-text

Abstract

This paper presents a method to increase the reliability of Unmanned Aerial Vehicle (UAV) sensor Fault Detection and Identification (FDI) in a multi-UAV context. Differential Global Positioning System (DGPS) and inertial sensors are used for sensor FDI in each UAV. The method [...] Read more.

This paper presents a method to increase the reliability of Unmanned Aerial Vehicle (UAV) sensor Fault Detection and Identification (FDI) in a multi-UAV context. Differential Global Positioning System (DGPS) and inertial sensors are used for sensor FDI in each UAV. The method uses additional position estimations that augment individual UAV FDI system. These additional estimations are obtained using images from the same planar scene taken from two different UAVs. Since accuracy and noise level of the estimation depends on several factors, dynamic replanning of the multi-UAV team can be used to obtain a better estimation in case of faults caused by slow growing errors of absolute position estimation that cannot be detected by using local FDI in the UAVs. Experimental results with data from two real UAVs are also presented. Full article

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

Open AccessArticle Modelling and Calibration Technique of Laser Triangulation Sensors for Integration in Robot Arms and Articulated Arm Coordinate Measuring Machines

by Jorge Santolaria, David Guillomía, Carlos Cajal, José A. Albajez and Juan J. Aguilar

Sensors 2009, 9(9), 7374-7396; doi:10.3390/s90907374

Received: 14 July 2009 / Revised: 9 September 2009 / Accepted: 10 September 2009 / Published: 11 September 2009

Cited by 17 | PDF Full-text (1115 KB) | HTML Full-text | XML Full-text

Abstract

A technique for intrinsic and extrinsic calibration of a laser triangulation sensor (LTS) integrated in an articulated arm coordinate measuring machine (AACMM) is presented in this paper. After applying a novel approach to the AACMM kinematic parameter identification problem, by means of [...] Read more.

A technique for intrinsic and extrinsic calibration of a laser triangulation sensor (LTS) integrated in an articulated arm coordinate measuring machine (AACMM) is presented in this paper. After applying a novel approach to the AACMM kinematic parameter identification problem, by means of a single calibration gauge object, a one-step calibration method to obtain both intrinsic―laser plane, CCD sensor and camera geometry―and extrinsic parameters related to the AACMM main frame has been developed. This allows the integration of LTS and AACMM mathematical models without the need of additional optimization methods after the prior sensor calibration, usually done in a coordinate measuring machine (CMM) before the assembly of the sensor in the arm. The experimental tests results for accuracy and repeatability show the suitable performance of this technique, resulting in a reliable, quick and friendly calibration method for the AACMM final user. The presented method is also valid for sensor integration in robot arms and CMMs. Full article

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

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Open AccessArticle Using the Optical Mouse Sensor as a Two-Euro Counterfeit Coin Detector

by Marcel Tresanchez, Tomàs Pallejà, Mercè Teixidó and Jordi Palacín

Sensors 2009, 9(9), 7083-7096; doi:10.3390/s90907083

Received: 7 August 2009 / Revised: 20 August 2009 / Accepted: 21 August 2009 / Published: 4 September 2009

Cited by 13 | PDF Full-text (339 KB) | HTML Full-text | XML Full-text

Abstract

In this paper, the sensor of an optical mouse is presented as a counterfeit coin detector applied to the two-Euro case. The detection process is based on the short distance image acquisition capabilities of the optical mouse sensor where partial images of [...] Read more.

In this paper, the sensor of an optical mouse is presented as a counterfeit coin detector applied to the two-Euro case. The detection process is based on the short distance image acquisition capabilities of the optical mouse sensor where partial images of the coin under analysis are compared with some partial reference coin images for matching. Results show that, using only the vision sense, the counterfeit acceptance and rejection rates are very similar to those of a trained user and better than those of an untrained user. Full article

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

Open AccessArticle Application of Close Range Photogrammetry to Deck Measurement in Recreational Ships

by Celestino Ordóñez, Belén Riveiro, Pedro Arias and Julia Armesto

Sensors 2009, 9(9), 6991-7002; doi:10.3390/s90906991

Received: 13 July 2009 / Revised: 13 August 2009 / Accepted: 31 August 2009 / Published: 3 September 2009

Cited by 7 | PDF Full-text (277 KB) | HTML Full-text | XML Full-text

Abstract

In this article, we present results that demonstrate the utility of close range photogrammetry in the measurement of decks in recreational craft as an alternate measurement system to the one based on direct acquisition of coordinates. The areas of deck covered with [...] Read more.

In this article, we present results that demonstrate the utility of close range photogrammetry in the measurement of decks in recreational craft as an alternate measurement system to the one based on direct acquisition of coordinates. The areas of deck covered with teakwood for aesthetic or security reasons were measured. Both methods were compared in terms of precision of measurements, time consumption, equipment cost, and ease of manipulation and equipment transportation. Based on the results, we conclude that photogrammetry has advantages in almost every aspect with respect to the direct method. Consequently, photogrammetry is suggested as a suitable method for coordinate measurement of decks in recreational ships. However, in some special circumstances, where ships have wide corridors with few obstacles the direct method can be more appropriate than the photogrammetric method. Full article

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

Open AccessArticle On the Application of Different Event-Based Sampling Strategies to the Control of a Simple Industrial Process

by José Sánchez, Miguel Ángel Guarnes and Sebastián Dormido

Sensors 2009, 9(9), 6795-6818; doi:10.3390/s90906795

Received: 7 July 2009 / Revised: 20 August 2009 / Accepted: 24 August 2009 / Published: 27 August 2009

Cited by 39 | PDF Full-text (744 KB) | HTML Full-text | XML Full-text

Abstract

This paper is an experimental study of the utilization of different event-based strategies for the automatic control of a simple but very representative industrial process: the level control of a tank. In an event-based control approach it is the triggering of a [...] Read more.

This paper is an experimental study of the utilization of different event-based strategies for the automatic control of a simple but very representative industrial process: the level control of a tank. In an event-based control approach it is the triggering of a specific event, and not the time, that instructs the sensor to send the current state of the process to the controller, and the controller to compute a new control action and send it to the actuator. In the document, five control strategies based on different event-based sampling techniques are described, compared, and contrasted with a classical time-based control approach and a hybrid one. The common denominator in the time, the hybrid, and the event-based control approaches is the controller: a proportional-integral algorithm with adaptations depending on the selected control approach. To compare and contrast each one of the hybrid and the pure event-based control algorithms with the time-based counterpart, the two tasks that a control strategy must achieve (set-point following and disturbance rejection) are independently analyzed. The experimental study provides new proof concerning the ability of event-based control strategies to minimize the data exchange among the control agents (sensors, controllers, actuators) when an error-free control of the process is not a hard requirement. Full article

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

Open AccessArticle A Self-Referencing Intensity Based Polymer Optical Fiber Sensor for Liquid Detection

by David Sánchez Montero, Carmen Vázquez, Ingo Möllers, Jon Arrúe and Dieter Jäger

Sensors 2009, 9(8), 6446-6455; doi:10.3390/s90806446

Received: 25 June 2009 / Revised: 13 August 2009 / Accepted: 13 August 2009 / Published: 20 August 2009

Cited by 19 | PDF Full-text (806 KB) | HTML Full-text | XML Full-text

Abstract

A novel self-referencing fiber optic intensity sensor based on bending losses of a partially polished polymer optical fiber (POF) coupler is presented. The coupling ratio (K) depends on the external liquid in which the sensor is immersed. It is possible to distinguish [...] Read more.

A novel self-referencing fiber optic intensity sensor based on bending losses of a partially polished polymer optical fiber (POF) coupler is presented. The coupling ratio (K) depends on the external liquid in which the sensor is immersed. It is possible to distinguish between different liquids and to detect their presence. Experimental results for the most usual liquids found in industry, like water and oil, are given. K value increases up to 10% from the nominal value depending on the liquid. Sensor temperature dependence has also been studied for a range from 25 ºC (environmental condition) to 50 ºC. Any sector requiring liquid level measurements in flammable atmospheres can benefit from this intrinsically safe technology. Full article

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

Open AccessArticle Curvature-Based Environment Description for Robot Navigation Using Laser Range Sensors

by Ricardo Vázquez-Martín, Pedro Núñez, Antonio Bandera and Francisco Sandoval

Sensors 2009, 9(8), 5894-5918; doi:10.3390/s90805894

Received: 15 May 2009 / Revised: 22 June 2009 / Accepted: 24 June 2009 / Published: 24 July 2009

Cited by 22 | PDF Full-text (2646 KB) | HTML Full-text | XML Full-text

Abstract

This work proposes a new feature detection and description approach for mobile robot navigation using 2D laser range sensors. The whole process consists of two main modules: a sensor data segmentation module and a feature detection and characterization module. The segmentation module [...] Read more.

This work proposes a new feature detection and description approach for mobile robot navigation using 2D laser range sensors. The whole process consists of two main modules: a sensor data segmentation module and a feature detection and characterization module. The segmentation module is divided in two consecutive stages: First, the segmentation stage divides the laser scan into clusters of consecutive range readings using a distance-based criterion. Then, the second stage estimates the curvature function associated to each cluster and uses it to split it into a set of straight-line and curve segments. The curvature is calculated using a triangle-area representation where, contrary to previous approaches, the triangle side lengths at each range reading are adapted to the local variations of the laser scan, removing noise without missing relevant points. This representation remains unchanged in translation or rotation, and it is also robust against noise. Thus, it is able to provide the same segmentation results although the scene will be perceived from different viewpoints. Therefore, segmentation results are used to characterize the environment using line and curve segments, real and virtual corners and edges. Real scan data collected from different environments by using different platforms are used in the experiments in order to evaluate the proposed environment description algorithm. Full article

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

Open AccessArticle Secure Many-to-One Communications in Wireless Sensor Networks

by Alexandre Viejo, Josep Domingo-Ferrer, Francesc Sebé and Jordi Castellà-Roca

Sensors 2009, 9(7), 5324-5338; doi:10.3390/s90705324

Received: 18 May 2009 / Accepted: 2 July 2009 / Published: 7 July 2009

Cited by 5 | PDF Full-text (184 KB) | HTML Full-text | XML Full-text

Abstract

Wireless Sensor Networks (WSN) are formed by nodes with limited computational and power resources. WSNs are finding an increasing number of applications, both civilian and military, most of which require security for the sensed data being collected by the base station from [...] Read more.

Wireless Sensor Networks (WSN) are formed by nodes with limited computational and power resources. WSNs are finding an increasing number of applications, both civilian and military, most of which require security for the sensed data being collected by the base station from remote sensor nodes. In addition, when many sensor nodes transmit to the base station, the implosion problem arises. Providing security measures and implosion resistance in a resource-limited environment is a real challenge. This article reviews the aggregation strategies proposed in the literature to handle the bandwidth and security problems related to many-to-one transmission in WSNs. Recent contributions to secure lossless many-to-one communication developed by the authors in the context of several Spanish-funded projects are surveyed. Ongoing work on the secure lossy many-to-one communication is also sketched. Full article

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

Review

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Open AccessReview State-of-the-Art of (Bio)Chemical Sensor Developments in Analytical Spanish Groups

by María Reyes Plata, Ana María Contento and Angel Ríos

Sensors 2010, 10(4), 2511-2576; doi:10.3390/s100402511

Received: 23 December 2009 / Revised: 3 February 2010 / Accepted: 28 February 2010 / Published: 24 March 2010

Cited by 13 | PDF Full-text (341 KB) | HTML Full-text | XML Full-text

Abstract

(Bio)chemical sensors are one of the most exciting fields in analytical chemistry today. The development of these analytical devices simplifies and miniaturizes the whole analytical process. Although the initial expectation of the massive incorporation of sensors in routine analytical work has been [...] Read more.

(Bio)chemical sensors are one of the most exciting fields in analytical chemistry today. The development of these analytical devices simplifies and miniaturizes the whole analytical process. Although the initial expectation of the massive incorporation of sensors in routine analytical work has been truncated to some extent, in many other cases analytical methods based on sensor technology have solved important analytical problems. Many research groups are working in this field world-wide, reporting interesting results so far. Modestly, Spanish researchers have contributed to these recent developments. In this review, we summarize the more representative achievements carried out for these groups. They cover a wide variety of sensors, including optical, electrochemical, piezoelectric or electro-mechanical devices, used for laboratory or field analyses. The capabilities to be used in different applied areas are also critically discussed. Full article

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

Open AccessReview Small Fluxgate Magnetometers: Development and Future Trends in Spain

by David Ciudad, Marina Díaz-Michelena, Lucas Pérez and Claudio Aroca

Sensors 2010, 10(3), 1859-1870; doi:10.3390/s100301859

Received: 22 December 2009 / Revised: 22 January 2010 / Accepted: 5 February 2010 / Published: 9 March 2010

Cited by 7 | PDF Full-text (428 KB) | HTML Full-text | XML Full-text

Abstract

In this paper, we give an overview of the research on fluxgate magnetometers carried out in Spain. In particular we focus in the development of the planar-type instruments. We summarize the fabrication processes and signal processing developments as well as their use [...] Read more.

In this paper, we give an overview of the research on fluxgate magnetometers carried out in Spain. In particular we focus in the development of the planar-type instruments. We summarize the fabrication processes and signal processing developments as well as their use in complex systems and space. Full article

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

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Open AccessReview Ultramicroelectrode Array Based Sensors: A Promising Analytical Tool for Environmental Monitoring

by Jahir Orozco, César Fernández-Sánchez and Cecilia Jiménez-Jorquera

Sensors 2010, 10(1), 475-490; doi:10.3390/s100100475

Received: 4 December 2009 / Revised: 16 December 2009 / Accepted: 24 December 2009 / Published: 7 January 2010

Cited by 19 | PDF Full-text (780 KB) | HTML Full-text | XML Full-text

Abstract

The particular analytical performance of ultramicroelectrode arrays (UMEAs) has attracted a high interest by the research community and has led to the development of a variety of electroanalytical applications. UMEA-based approaches have demonstrated to be powerful, simple, rapid and cost-effective analytical tools [...] Read more.

The particular analytical performance of ultramicroelectrode arrays (UMEAs) has attracted a high interest by the research community and has led to the development of a variety of electroanalytical applications. UMEA-based approaches have demonstrated to be powerful, simple, rapid and cost-effective analytical tools for environmental analysis compared to available conventional electrodes and standardised analytical techniques. An overview of the fabrication processes of UMEAs, their characterization and applications carried out by the Spanish scientific community is presented. A brief explanation of theoretical aspects that highlight their electrochemical behavior is also given. Finally, the applications of this transducer platform in the environmental field are discussed. Full article

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

Open AccessReview Survey of Visual and Force/Tactile Control of Robots for Physical Interaction in Spain

by Gabriel J. Garcia, Juan A. Corrales, Jorge Pomares and Fernando Torres

Sensors 2009, 9(12), 9689-9733; doi:10.3390/s91209689

Received: 14 October 2009 / Revised: 17 November 2009 / Accepted: 18 November 2009 / Published: 2 December 2009

Cited by 11 | PDF Full-text (2640 KB) | HTML Full-text | XML Full-text

Abstract

Sensors provide robotic systems with the information required to perceive the changes that happen in unstructured environments and modify their actions accordingly. The robotic controllers which process and analyze this sensory information are usually based on three types of sensors (visual, force/torque [...] Read more.

Sensors provide robotic systems with the information required to perceive the changes that happen in unstructured environments and modify their actions accordingly. The robotic controllers which process and analyze this sensory information are usually based on three types of sensors (visual, force/torque and tactile) which identify the most widespread robotic control strategies: visual servoing control, force control and tactile control. This paper presents a detailed review on the sensor architectures, algorithmic techniques and applications which have been developed by Spanish researchers in order to implement these mono-sensor and multi-sensor controllers which combine several sensors. Full article

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

Open AccessReview Thin Magnetically Soft Wires for Magnetic Microsensors

by Valentina Zhukova, Mihail Ipatov and Arcady Zhukov

Sensors 2009, 9(11), 9216-9240; doi:10.3390/s91109216

Received: 29 September 2009 / Revised: 9 November 2009 / Accepted: 11 November 2009 / Published: 18 November 2009

Cited by 88 | PDF Full-text (833 KB) | HTML Full-text | XML Full-text

Abstract

Recent advances in technology involving magnetic materials require development of novel advanced magnetic materials with improved magnetic and magneto-transport properties and with reduced dimensionality. Therefore magnetic materials with outstanding magnetic characteristics and reduced dimensionality have recently gained much attention. Among these magnetic [...] Read more.

Recent advances in technology involving magnetic materials require development of novel advanced magnetic materials with improved magnetic and magneto-transport properties and with reduced dimensionality. Therefore magnetic materials with outstanding magnetic characteristics and reduced dimensionality have recently gained much attention. Among these magnetic materials a family of thin wires with reduced geometrical dimensions (of order of 1–30 μm in diameter) have gained importance within the last few years. These thin wires combine excellent soft magnetic properties (with coercivities up to 4 A/m) with attractive magneto-transport properties (Giant Magneto-impedance effect, GMI, Giant Magneto-resistance effect, GMR) and an unusual re-magnetization process in positive magnetostriction compositions exhibiting quite fast domain wall propagation. In this paper we overview the magnetic and magneto-transport properties of these microwires that make them suitable for microsensor applications. Full article

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

Open AccessReview Routing Protocols in Wireless Sensor Networks

by Luis Javier García Villalba, Ana Lucila Sandoval Orozco, Alicia Triviño Cabrera and Cláudia Jacy Barenco Abbas

Sensors 2009, 9(11), 8399-8421; doi:10.3390/s91108399

Received: 14 September 2009 / Revised: 28 September 2009 / Accepted: 10 October 2009 / Published: 26 October 2009

Cited by 60 | PDF Full-text (451 KB) | HTML Full-text | XML Full-text

Abstract

The applications of wireless sensor networks comprise a wide variety of scenarios. In most of them, the network is composed of a significant number of nodes deployed in an extensive area in which not all nodes are directly connected. Then, the data [...] Read more.

The applications of wireless sensor networks comprise a wide variety of scenarios. In most of them, the network is composed of a significant number of nodes deployed in an extensive area in which not all nodes are directly connected. Then, the data exchange is supported by multihop communications. Routing protocols are in charge of discovering and maintaining the routes in the network. However, the appropriateness of a particular routing protocol mainly depends on the capabilities of the nodes and on the application requirements. This paper presents a review of the main routing protocols proposed for wireless sensor networks. Additionally, the paper includes the efforts carried out by Spanish universities on developing optimization techniques in the area of routing protocols for wireless sensor networks. Full article

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

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Open AccessReview Magnetic Field Sensors Based on Giant Magnetoresistance (GMR) Technology: Applications in Electrical Current Sensing

by Càndid Reig, María-Dolores Cubells-Beltrán and Diego Ramírez Muñoz

Sensors 2009, 9(10), 7919-7942; doi:10.3390/s91007919

Received: 15 September 2009 / Revised: 25 September 2009 / Accepted: 29 September 2009 / Published: 12 October 2009

Cited by 62 | PDF Full-text (1014 KB) | HTML Full-text | XML Full-text

Abstract

The 2007 Nobel Prize in Physics can be understood as a global recognition to the rapid development of the Giant Magnetoresistance (GMR), from both the physics and engineering points of view. Behind the utilization of GMR structures as read heads for massive [...] Read more.

The 2007 Nobel Prize in Physics can be understood as a global recognition to the rapid development of the Giant Magnetoresistance (GMR), from both the physics and engineering points of view. Behind the utilization of GMR structures as read heads for massive storage magnetic hard disks, important applications as solid state magnetic sensors have emerged. Low cost, compatibility with standard CMOS technologies and high sensitivity are common advantages of these sensors. This way, they have been successfully applied in a lot different environments. In this work, we are trying to collect the Spanish contributions to the progress of the research related to the GMR based sensors covering, among other subjects, the applications, the sensor design, the modelling and the electronic interfaces, focusing on electrical current sensing applications. Full article

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

Open AccessReview On-Line Metrology with Conoscopic Holography: Beyond Triangulation

by Ignacio Álvarez, Jose M. Enguita, María Frade, Jorge Marina and Guillermo Ojea

Sensors 2009, 9(9), 7021-7037; doi:10.3390/s90907021

Received: 23 July 2009 / Revised: 26 August 2009 / Accepted: 28 August 2009 / Published: 4 September 2009

Cited by 14 | PDF Full-text (1757 KB) | HTML Full-text | XML Full-text

Abstract

On-line non-contact surface inspection with high precision is still an open problem. Laser triangulation techniques are the most common solution for this kind of systems, but there exist fundamental limitations to their applicability when high precisions, long standoffs or large apertures are [...] Read more.

On-line non-contact surface inspection with high precision is still an open problem. Laser triangulation techniques are the most common solution for this kind of systems, but there exist fundamental limitations to their applicability when high precisions, long standoffs or large apertures are needed, and when there are difficult operating conditions. Other methods are, in general, not applicable in hostile environments or inadequate for on-line measurement. In this paper we review the latest research in Conoscopic Holography, an interferometric technique that has been applied successfully in this kind of applications, ranging from submicrometric roughness measurements, to long standoff sensors for surface defect detection in steel at high temperatures. Full article

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

Open AccessReview Optical Slot-Waveguide Based Biochemical Sensors

by Carlos Angulo Barrios

Sensors 2009, 9(6), 4751-4765; doi:10.3390/s90604751

Received: 27 May 2009 / Revised: 9 June 2009 / Accepted: 15 June 2009 / Published: 16 June 2009

Cited by 55 | PDF Full-text (791 KB) | HTML Full-text | XML Full-text

Abstract

Slot-waveguides allow light to be guided and strongly confined inside a nanometer-scale region of low refractive index. Thus stronger light-analyte interaction can be obtained as compared to that achievable by a conventional waveguide, in which the propagating beam is confined to the [...] Read more.

Slot-waveguides allow light to be guided and strongly confined inside a nanometer-scale region of low refractive index. Thus stronger light-analyte interaction can be obtained as compared to that achievable by a conventional waveguide, in which the propagating beam is confined to the high-refractive-index core of the waveguide. In addition, slot-waveguides can be fabricated by employing CMOS compatible materials and technology, enabling miniaturization, integration with electronic, photonic and fluidic components in a chip, and mass production. These advantages have made the use of slot-waveguides for highly sensitive biochemical optical integrated sensors an emerging field. In this paper, recent achievements in slot-waveguide based biochemical sensing will be reviewed. These include slot-waveguide ring resonator based refractometric label-free biosensors, label-based optical sensing, and nano-opto-mechanical sensors. Full article

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

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