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Special Issue "Motion Detectors"

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A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Physical Sensors".

Deadline for manuscript submissions: closed (31 December 2009)

Special Issue Editor

Guest Editor
Prof. Dr. Scott E. Crouter

Department of Exercise and Health Sciences, University of Massachusetts Boston, 100 Morrissey Blvd., Boston, MA 02125, USA
Interests: motion sensors; physical activity measurement; heart rate; exercise physiology

Keywords

  • motion detectors
  • motion sensors
  • accelerometers
  • physical sensors
  • mobile sensors
  • tracking devices

Published Papers (12 papers)

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Research

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Open AccessArticle A Bayesian Framework for Human Body Pose Tracking from Depth Image Sequences
Sensors 2010, 10(5), 5280-5293; doi:10.3390/s100505280
Received: 7 April 2010 / Revised: 19 May 2010 / Accepted: 20 May 2010 / Published: 25 May 2010
Cited by 21 | PDF Full-text (1855 KB) | HTML Full-text | XML Full-text
Abstract
This paper addresses the problem of accurate and robust tracking of 3D human body pose from depth image sequences. Recovering the large number of degrees of freedom in human body movements from a depth image sequence is challenging due to the need [...] Read more.
This paper addresses the problem of accurate and robust tracking of 3D human body pose from depth image sequences. Recovering the large number of degrees of freedom in human body movements from a depth image sequence is challenging due to the need to resolve the depth ambiguity caused by self-occlusions and the difficulty to recover from tracking failure. Human body poses could be estimated through model fitting using dense correspondences between depth data and an articulated human model (local optimization method). Although it usually achieves a high accuracy due to dense correspondences, it may fail to recover from tracking failure. Alternately, human pose may be reconstructed by detecting and tracking human body anatomical landmarks (key-points) based on low-level depth image analysis. While this method (key-point based method) is robust and recovers from tracking failure, its pose estimation accuracy depends solely on image-based localization accuracy of key-points. To address these limitations, we present a flexible Bayesian framework for integrating pose estimation results obtained by methods based on key-points and local optimization. Experimental results are shown and performance comparison is presented to demonstrate the effectiveness of the proposed approach. Full article
(This article belongs to the Special Issue Motion Detectors)
Open AccessArticle Non-Linearity Analysis of Depth and Angular Indexes for Optimal Stereo SLAM
Sensors 2010, 10(4), 4159-4179; doi:10.3390/s100404159
Received: 22 March 2010 / Revised: 19 April 2010 / Accepted: 20 April 2010 / Published: 26 April 2010
Cited by 4 | PDF Full-text (607 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this article, we present a real-time 6DoF egomotion estimation system for indoor environments using a wide-angle stereo camera as the only sensor. The stereo camera is carried in hand by a person walking at normal walking speeds 3–5 km/h. We present [...] Read more.
In this article, we present a real-time 6DoF egomotion estimation system for indoor environments using a wide-angle stereo camera as the only sensor. The stereo camera is carried in hand by a person walking at normal walking speeds 3–5 km/h. We present the basis for a vision-based system that would assist the navigation of the visually impaired by either providing information about their current position and orientation or guiding them to their destination through different sensing modalities. Our sensor combines two different types of feature parametrization: inverse depth and 3D in order to provide orientation and depth information at the same time. Natural landmarks are extracted from the image and are stored as 3D or inverse depth points, depending on a depth threshold. This depth threshold is used for switching between both parametrizations and it is computed by means of a non-linearity analysis of the stereo sensor. Main steps of our system approach are presented as well as an analysis about the optimal way to calculate the depth threshold. At the moment each landmark is initialized, the normal of the patch surface is computed using the information of the stereo pair. In order to improve long-term tracking, a patch warping is done considering the normal vector information. Some experimental results under indoor environments and conclusions are presented. Full article
(This article belongs to the Special Issue Motion Detectors)
Open AccessArticle Optical Flow in a Smart Sensor Based on Hybrid Analog-Digital Architecture
Sensors 2010, 10(4), 2975-2994; doi:10.3390/s100402975
Received: 20 January 2010 / Revised: 5 March 2010 / Accepted: 17 March 2010 / Published: 30 March 2010
Cited by 4 | PDF Full-text (1002 KB) | HTML Full-text | XML Full-text
Abstract
The purpose of this study is to develop a motion sensor (delivering optical flow estimations) using a platform that includes the sensor itself, focal plane processing resources, and co-processing resources on a general purpose embedded processor. All this is implemented on a [...] Read more.
The purpose of this study is to develop a motion sensor (delivering optical flow estimations) using a platform that includes the sensor itself, focal plane processing resources, and co-processing resources on a general purpose embedded processor. All this is implemented on a single device as a SoC (System-on-a-Chip). Optical flow is the 2-D projection into the camera plane of the 3-D motion information presented at the world scenario. This motion representation is widespread well-known and applied in the science community to solve a wide variety of problems. Most applications based on motion estimation require work in real-time; hence, this restriction must be taken into account. In this paper, we show an efficient approach to estimate the motion velocity vectors with an architecture based on a focal plane processor combined on-chip with a 32 bits NIOS II processor. Our approach relies on the simplification of the original optical flow model and its efficient implementation in a platform that combines an analog (focal-plane) and digital (NIOS II) processor. The system is fully functional and is organized in different stages where the early processing (focal plane) stage is mainly focus to pre-process the input image stream to reduce the computational cost in the post-processing (NIOS II) stage. We present the employed co-design techniques and analyze this novel architecture. We evaluate the system’s performance and accuracy with respect to the different proposed approaches described in the literature. We also discuss the advantages of the proposed approach as well as the degree of efficiency which can be obtained from the focal plane processing capabilities of the system. The final outcome is a low cost smart sensor for optical flow computation with real-time performance and reduced power consumption that can be used for very diverse application domains. Full article
(This article belongs to the Special Issue Motion Detectors)
Figures

Open AccessArticle Real-Time Estimation of Pathological Tremor Parameters from Gyroscope Data
Sensors 2010, 10(3), 2129-2149; doi:10.3390/s100302129
Received: 25 January 2010 / Revised: 26 February 2010 / Accepted: 1 March 2010 / Published: 16 March 2010
Cited by 29 | PDF Full-text (1176 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a two stage algorithm for real-time estimation of instantaneous tremor parameters from gyroscope recordings. Gyroscopes possess the advantage of providing directly joint rotational speed, overcoming the limitations of traditional tremor recording based on accelerometers. The proposed algorithm first extracts [...] Read more.
This paper presents a two stage algorithm for real-time estimation of instantaneous tremor parameters from gyroscope recordings. Gyroscopes possess the advantage of providing directly joint rotational speed, overcoming the limitations of traditional tremor recording based on accelerometers. The proposed algorithm first extracts tremor patterns from raw angular data, and afterwards estimates its instantaneous amplitude and frequency. Real-time separation of voluntary and tremorous motion relies on their different frequency contents, whereas tremor modelling is based on an adaptive LMS algorithm and a Kalman filter. Tremor parameters will be employed to drive a neuroprosthesis for tremor suppression based on biomechanical loading. Full article
(This article belongs to the Special Issue Motion Detectors)
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Open AccessArticle A Multiscale Region-Based Motion Detection and Background Subtraction Algorithm
Sensors 2010, 10(2), 1041-1061; doi:10.3390/s100201041
Received: 1 December 2009 / Revised: 15 January 2010 / Accepted: 22 January 2010 / Published: 28 January 2010
Cited by 30 | PDF Full-text (2303 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a region-based method for background subtraction. It relies on color histograms, texture information, and successive division of candidate rectangular image regions to model the background and detect motion. Our proposed algorithm uses this principle and combines it with Gaussian [...] Read more.
This paper presents a region-based method for background subtraction. It relies on color histograms, texture information, and successive division of candidate rectangular image regions to model the background and detect motion. Our proposed algorithm uses this principle and combines it with Gaussian Mixture background modeling to produce a new method which outperforms the classic Gaussian Mixture background subtraction method. Our method has the advantages of filtering noise during image differentiation and providing a selectable level of detail for the contour of the moving shapes. The algorithm is tested on various video sequences and is shown to outperform state-of-the-art background subtraction methods. Full article
(This article belongs to the Special Issue Motion Detectors)
Open AccessArticle Real-Time Accumulative Computation Motion Detectors
Sensors 2009, 9(12), 10044-10065; doi:10.3390/s91210044
Received: 28 October 2009 / Revised: 24 November 2009 / Accepted: 30 November 2009 / Published: 10 December 2009
Cited by 6 | PDF Full-text (1024 KB) | HTML Full-text | XML Full-text
Abstract
The neurally inspired accumulative computation (AC) method and its application to motion detection have been introduced in the past years. This paper revisits the fact that many researchers have explored the relationship between neural networks and finite state machines. Indeed, finite state [...] Read more.
The neurally inspired accumulative computation (AC) method and its application to motion detection have been introduced in the past years. This paper revisits the fact that many researchers have explored the relationship between neural networks and finite state machines. Indeed, finite state machines constitute the best characterized computational model, whereas artificial neural networks have become a very successful tool for modeling and problem solving. The article shows how to reach real-time performance after using a model described as a finite state machine. This paper introduces two steps towards that direction: (a) A simplification of the general AC method is performed by formally transforming it into a finite state machine. (b) A hardware implementation in FPGA of such a designed AC module, as well as an 8-AC motion detector, providing promising performance results. We also offer two case studies of the use of AC motion detectors in surveillance applications, namely infrared-based people segmentation and color-based people tracking, respectively. Full article
(This article belongs to the Special Issue Motion Detectors)
Open AccessArticle Segment Tracking via a Spatiotemporal Linking Process including Feedback Stabilization in an n-D Lattice Model
Sensors 2009, 9(11), 9355-9379; doi:10.3390/s91109355
Received: 7 August 2009 / Revised: 5 November 2009 / Accepted: 9 November 2009 / Published: 20 November 2009
Cited by 8 | PDF Full-text (1301 KB) | HTML Full-text | XML Full-text
Abstract
Model-free tracking is important for solving tasks such as moving-object tracking and action recognition in cases where no prior object knowledge is available. For this purpose, we extend the concept of spatially synchronous dynamics in spin-lattice models to the spatiotemporal domain to [...] Read more.
Model-free tracking is important for solving tasks such as moving-object tracking and action recognition in cases where no prior object knowledge is available. For this purpose, we extend the concept of spatially synchronous dynamics in spin-lattice models to the spatiotemporal domain to track segments within an image sequence. The method is related to synchronization processes in neural networks and based on superparamagnetic clustering of data. Spin interactions result in the formation of clusters of correlated spins, providing an automatic labeling of corresponding image regions. The algorithm obeys detailed balance. This is an important property as it allows for consistent spin-transfer across subsequent frames, which can be used for segment tracking. Therefore, in the tracking process the correct equilibrium will always be found, which is an important advance as compared with other more heuristic tracking procedures. In the case of long image sequences, i.e., movies, the algorithm is augmented with a feedback mechanism, further stabilizing segment tracking. Full article
(This article belongs to the Special Issue Motion Detectors)
Figures

Open AccessArticle Measuring Gait Using a Ground Laser Range Sensor
Sensors 2009, 9(11), 9133-9146; doi:10.3390/s91109133
Received: 7 August 2009 / Revised: 20 October 2009 / Accepted: 24 October 2009 / Published: 17 November 2009
Cited by 18 | PDF Full-text (288 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes a measurement system designed to register the displacement of the legs using a two-dimensional laser range sensor with a scanning plane parallel to the ground and extract gait parameters. In the proposed methodology, the position of the legs is [...] Read more.
This paper describes a measurement system designed to register the displacement of the legs using a two-dimensional laser range sensor with a scanning plane parallel to the ground and extract gait parameters. In the proposed methodology, the position of the legs is estimated by fitting two circles with the laser points that define their contour and the gait parameters are extracted applying a step-line model to the estimated displacement of the legs to reduce uncertainty in the determination of the stand and swing phase of the gait. Results obtained in a range up to 8 m shows that the systematic error in the location of one static leg is lower than 10 mm with and standard deviation lower than 8 mm; this deviation increases to 11 mm in the case of a moving leg. The proposed measurement system has been applied to estimate the gait parameters of six volunteers in a preliminary walking experiment. Full article
(This article belongs to the Special Issue Motion Detectors)
Figures

Open AccessArticle Classifying Human Leg Motions with Uniaxial Piezoelectric Gyroscopes
Sensors 2009, 9(11), 8508-8546; doi:10.3390/s91108508
Received: 10 August 2009 / Revised: 21 September 2009 / Accepted: 28 September 2009 / Published: 27 October 2009
Cited by 18 | PDF Full-text (2075 KB) | HTML Full-text | XML Full-text
Abstract
This paper provides a comparative study on the different techniques of classifying human leg motions that are performed using two low-cost uniaxial piezoelectric gyroscopes worn on the leg. A number of feature sets, extracted from the raw inertial sensor data in different [...] Read more.
This paper provides a comparative study on the different techniques of classifying human leg motions that are performed using two low-cost uniaxial piezoelectric gyroscopes worn on the leg. A number of feature sets, extracted from the raw inertial sensor data in different ways, are used in the classification process. The classification techniques implemented and compared in this study are: Bayesian decision making (BDM), a rule-based algorithm (RBA) or decision tree, least-squares method (LSM), k-nearest neighbor algorithm (k-NN), dynamic time warping (DTW), support vector machines (SVM), and artificial neural networks (ANN). A performance comparison of these classification techniques is provided in terms of their correct differentiation rates, confusion matrices, computational cost, and training and storage requirements. Three different cross-validation techniques are employed to validate the classifiers. The results indicate that BDM, in general, results in the highest correct classification rate with relatively small computational cost. Full article
(This article belongs to the Special Issue Motion Detectors)
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Open AccessArticle REMOTE, a Wireless Sensor Network Based System to Monitor Rowing Performance
Sensors 2009, 9(9), 7069-7082; doi:10.3390/s90907069
Received: 15 July 2009 / Revised: 5 August 2009 / Accepted: 3 September 2009 / Published: 4 September 2009
Cited by 9 | PDF Full-text (4066 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we take a hard look at the performance of REMOTE, a sensor network based application that provides a detailed picture of a boat movement, individual rower performance, or his/her performance compared with other crew members. The application analyzes data [...] Read more.
In this paper, we take a hard look at the performance of REMOTE, a sensor network based application that provides a detailed picture of a boat movement, individual rower performance, or his/her performance compared with other crew members. The application analyzes data gathered with a WSN strategically deployed over a boat to obtain information on the boat and oar movements. Functionalities of REMOTE are compared to those of RowX [1] outdoor instrument, a commercial wired sensor instrument designed for similar purposes. This study demonstrates that with smart geometrical configuration of the sensors, rotation and translation of the oars and boat can be obtained. Three different tests are performed: laboratory calibration allows us to become familiar with the accelerometer readings and validate the theory, ergometer tests which help us to set the acquisition parameters, and on boat tests shows the application potential of this technologies in sports. Full article
(This article belongs to the Special Issue Motion Detectors)
Open AccessArticle Adaptive Momentum-Based Motion Detection Approach and Its Application on Handoff in Wireless Networks
Sensors 2009, 9(7), 5715-5739; doi:10.3390/s90705715
Received: 15 June 2009 / Revised: 3 July 2009 / Accepted: 15 July 2009 / Published: 17 July 2009
Cited by 5 | PDF Full-text (838 KB) | HTML Full-text | XML Full-text
Abstract
Positioning and tracking technologies can detect the location and the movement of mobile nodes (MNs), such as cellular phone, vehicular and mobile sensor, to predict potential handoffs. However, most motion detection mechanisms require additional hardware (e.g., GPS and directed antenna), costs (e.g., [...] Read more.
Positioning and tracking technologies can detect the location and the movement of mobile nodes (MNs), such as cellular phone, vehicular and mobile sensor, to predict potential handoffs. However, most motion detection mechanisms require additional hardware (e.g., GPS and directed antenna), costs (e.g., power consumption and monetary cost) and supply systems (e.g., network fingerprint server). This paper proposes a Momentum of Received Signal Strength (MRSS) based motion detection method and its application on handoff. MRSS uses the exponentially weighted moving average filter with multiple moving average window size to analyze the received radio signal. With MRSS, an MN can predict its motion state and make a handoff trigger at the right time without any assistance from positioning systems. Moreover, a novel motion state dependent MRSS scheme called Dynamic MRSS (DMRSS) algorithm is proposed to adjust the motion detection sensitivity. In our simulation, the MRSSand DMRSS-based handoff algorithms can reduce the number of unnecessary handoffs up to 44% and save battery power up to 75%. Full article
(This article belongs to the Special Issue Motion Detectors)

Review

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Open AccessReview Visual Pathways Serving Motion Detection in the Mammalian Brain
Sensors 2010, 10(4), 3218-3242; doi:10.3390/s100403218
Received: 5 February 2010 / Revised: 16 March 2010 / Accepted: 17 March 2010 / Published: 1 April 2010
Cited by 4 | PDF Full-text (449 KB) | HTML Full-text | XML Full-text
Abstract
Motion perception is the process through which one gathers information on the dynamic visual world, in terms of the speed and movement direction of its elements. Motion sensation takes place from the retinal light sensitive elements, through the visual thalamus, the primary [...] Read more.
Motion perception is the process through which one gathers information on the dynamic visual world, in terms of the speed and movement direction of its elements. Motion sensation takes place from the retinal light sensitive elements, through the visual thalamus, the primary and higher visual cortices. In the present review we aim to focus on the extrageniculo-extrastriate cortical and subcortical visual structures of the feline and macaque brain and discuss their functional role in visual motion perception. Special attention is paid to the ascending tectofugal system that may serve for detection of the visual environment during self-motion. Full article
(This article belongs to the Special Issue Motion Detectors)

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