Journal of Sensors The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Denoising Method Based on Sparse Representation for WFT Signal Thu, 13 Feb 2014 12:33:16 +0000 Affected by external noise and various nature disturbances, Wheel Force Transducer (WFT) signal may be completely submerged, and the sensitivity and the reliability of measurement can be strongly decreased. In this paper, a new wavelet packet denoising method based on sparse representation is proposed to remove the noises from WFT signal. In this method, the problem of recovering the noiseless signal is converted into an optimization problem of recovering the sparsity of their wavelet package coefficients, and the wavelet package coefficients of the noiseless signals can be obtained by the augmented Lagrange optimization method. Then the denoised WFT signal can be reconstructed by wavelet packet reconstruction. The experiments on simulation signal and WFT signal show that the proposed denoising method based on sparse representation is more effective for denoising WFT signal than the soft and hard threshold denoising methods. Xu Chen, Guoyu Lin, and Yuxin Zhang Copyright © 2014 Xu Chen et al. All rights reserved. A Self-Oscillating System to Measure the Conductivity and the Permittivity of Liquids within a Single Triangular Signal Thu, 13 Feb 2014 08:34:38 +0000 We present a methodology and a circuit to extract liquid resistance and capacitance simultaneously from the same output signal using interdigitated sensing electrodes. The principle consists in the generation of a current square wave and its application to the sensor to create a triangular output voltage which contains both the conductivity and permittivity parameters in a single periodic segment. This concept extends the Triangular Waveform Voltage (TWV) signal generation technique and is implemented by a system which consists in a closed-loop current-controlled oscillator and only requires DC power to operate. The system interface is portable and only a small number of electrical components are used to generate the expected signal. Conductivities of saline NaCl and KCl solutions, being first calibrated by commercial equipment, are characterized by a system prototype. The results show excellent linearity and prove the repeatability of the measurements. Experiments on water-glycerol mixtures validate the proposed sensing approach to measure the permittivity and the conductivity simultaneously. We discussed and identified the sources of measurement errors as circuit parasitic capacitances, switching clock feedthrough, charge injection, bandwidth, and control-current quality. Sylvain Druart, Denis Flandre, and Laurent A. Francis Copyright © 2014 Sylvain Druart et al. All rights reserved. Identification of Wheat Varieties with a Parallel-Plate Capacitance Sensor Using Fisher’s Linear Discriminant Analysis Thu, 06 Feb 2014 13:20:45 +0000 Fisher’s linear discriminant (FLD) models for wheat variety classification were developed and validated. The inputs to the FLD models were the capacitance (), impedance (), and phase angle (), measured at two frequencies. Classification of wheat varieties was obtained as output of the FLD models. and of a parallel-plate capacitance system, holding the wheat samples, were measured using an impedance meter, and the value was computed. The best model developed classified the wheat varieties, with accuracy of 95.4%, over the six wheat varieties tested. This method is simple, rapid, and nondestructive and would be useful for the breeders and the peanut industry. C. V. K. Kandala, K. N. Govindarajan, N. Puppala, V. Settaluri, and R. S. Reddy Copyright © 2014 C. V. K. Kandala et al. All rights reserved. Energy Balance Routing Algorithm Based on Virtual MIMO Scheme for Wireless Sensor Networks Thu, 02 Jan 2014 13:19:43 +0000 Wireless sensor networks are usually energy limited and therefore an energy-efficient routing algorithm is desired for prolonging the network lifetime. In this paper, we propose a new energy balance routing algorithm which has the following three improvements over the conventional LEACH algorithm. Firstly, we propose a new cluster head selection scheme by taking into consideration the remaining energy and the most recent energy consumption of the nodes and the entire network. In this way, the sensor nodes with smaller remaining energy or larger energy consumption will be much less likely to be chosen as cluster heads. Secondly, according to the ratio of remaining energy to distance, cooperative nodes are selected to form virtual MIMO structures. It mitigates the uneven distribution of clusters and the unbalanced energy consumption of the whole network. Thirdly, we construct a comprehensive energy consumption model, which can reflect more realistically the practical energy consumption. Numerical simulations analyze the influences of cooperative node numbers and cluster head node numbers on the network lifetime. It is shown that the energy consumption of the proposed routing algorithm is lower than the conventional LEACH algorithm and for the simulation example the network lifetime is prolonged about 25%. Jianpo Li, Xue Jiang, and I-Tai Lu Copyright © 2014 Jianpo Li et al. All rights reserved. Vapor Phase Sensing Using Metal Nanorod Thin Films Grown by Cryogenic Oblique Angle Deposition Mon, 23 Dec 2013 19:27:23 +0000 We demonstrate the chemical sensing capability of silver nanostructured films grown by cryogenic oblique angle deposition (OAD). For comparison, the films are grown side by side at cryogenic (~100 K) and at room temperature (~300 K) by e-beam evaporation. Based on the observed structural differences, it was hypothesized that the cryogenic OAD silver films should show an increased surface enhanced Raman scattering (SERS) sensitivity. COMSOL simulation results are presented to validate this hypothesis. Experimental SERS results of 4-aminobenzenethiol (4-ABT) Raman test probe molecules in vapor phase show good agreement with the simulation and indicate promising SERS applications for these nanostructured thin films. Piyush Shah, Dongquan Ju, Xiaoxu Niu, and Andrew M. Sarangan Copyright © 2013 Piyush Shah et al. All rights reserved. Damage Detection of Closed Crack in a Metallic Plate Using Nonlinear Ultrasonic Time Reversal Method Wed, 11 Dec 2013 14:38:26 +0000 Initial cracks in metallic structures incline to be closed at rest. Such incipient damage generally fails to be detected and located with traditional linear ultrasonic techniques because ultrasonic waves penetrate the contact area of the closed crack. In this paper, an imaging algorithm based on nonlinear ultrasonic time reversal method is proposed to detect closed cracks in aluminum plates. Two surface-bonded piezoelectric transducer arrays are used to generate, receive, and reemit ultrasonic wave signals. The closed crack is simulated by tightening a bolt on the aluminum plate. By applying large amplitude excitation voltage on the PZT transducers, the closed crack could be opened and closed. The transmitted waves recorded by PZT array contain nonlinear components, the signals are time reversed and emitted back, and the tone burst reconstructions are achieved. The linear reciprocity and the time reversibility break down due to the presence of the nonlinear components. The correlation coefficient between the original excitation signal and the reconstructed signal is calculated to define the damage index for individual sensing path and is used to develop an imaging algorithm to locate the closed crack on the plate. The experimental results demonstrate that incident wave signals and their reconstructed signals can be used to accurately detect and locate closed cracks. Wang Zhang, Weiliang Wu, Xiaoyi Sun, Li Xiao, and Wenzhong Qu Copyright © 2013 Wang Zhang et al. All rights reserved. Implicit Active Contours Driven by Local and Global Image Fitting Energy for Image Segmentation and Target Localization Wed, 27 Nov 2013 10:27:56 +0000 We propose a novel active contour model in a variational level set formulation for image segmentation and target localization. We combine a local image fitting term and a global image fitting term to drive the contour evolution. Our model can efficiently segment the images with intensity inhomogeneity with the contour starting anywhere in the image. In its numerical implementation, an efficient numerical schema is used to ensure sufficient numerical accuracy. We validated its effectiveness in numerous synthetic images and real images, and the promising experimental results show its advantages in terms of accuracy, efficiency, and robustness. Xiaosheng Yu, Yuanchen Qi, Ziwei Lu, and Nan Hu Copyright © 2013 Xiaosheng Yu et al. All rights reserved. Sensors for Robotics Mon, 25 Nov 2013 09:16:14 +0000 Aiguo Song, Guangming Song, Daniela Constantinescu, Lei Wang, and Quanjun Song Copyright © 2013 Aiguo Song et al. All rights reserved. Routing Protocols for Wireless Multimedia Sensor Network: A Survey Sun, 24 Nov 2013 15:40:34 +0000 Multimedia applications have become an essential part of our daily lives, and their use is flourishing day by day. The area of wireless sensor network is not an exception where the multimedia sensors are attracting the attention of the researchers increasingly, and it has shifted the focus from traditional scalar sensors to sensors equipped with multimedia devices. The multimedia sensors have the ability to capture video, image, audio, and scalar sensor data and deliver the multimedia content through sensors network. Due to the resource constraints nature of WSN introducing multimedia will add more challenges, so the protocols designed for multimedia wireless sensor network should be aware of the resource constraints nature of WSN and multimedia transmission requirement. This paper discusses the design challenges of routing protocols proposed for WMSN. A survey and comprehensive discussion are given for proposed protocols of WMSN followed by their limitations and features. Mohammed Abazeed, Norshiela Faisal, Suleiman Zubair, and Adel Ali Copyright © 2013 Mohammed Abazeed et al. All rights reserved. Mobile Visual Recognition on Smartphones Tue, 19 Nov 2013 15:43:06 +0000 This paper addresses the recognition of large-scale outdoor scenes on smartphones by fusing outputs of inertial sensors and computer vision techniques. The main contributions can be summarized as follows. Firstly, we propose an ORD (overlap region divide) method to plot image position area, which is fast enough to find the nearest visiting area and can also reduce the search range compared with the traditional approaches. Secondly, the vocabulary tree-based approach is improved by introducing GAGCC (gravity-aligned geometric consistency constraint). Our method involves no operation in the high-dimensional feature space and does not assume a global transform between a pair of images. Thus, it substantially reduces the computational complexity and memory usage, which makes the city scale image recognition feasible on the smartphone. Experiments on a collected database including 0.16 million images show that the proposed method demonstrates excellent recognition performance, while maintaining the average recognition time about 1 s. Zhenwen Gui, Yongtian Wang, Yue Liu, and Jing Chen Copyright © 2013 Zhenwen Gui et al. All rights reserved. System-Level Design Considerations for Carbon Nanotube Electromechanical Resonators Tue, 05 Nov 2013 10:37:11 +0000 Despite an evermore complete plethora of complex domain-specific semiempirical models, no succinct recipe for large-scale carbon nanotube electromechanical systems design has been formulated. To combine the benefits of these highly sensitive miniaturized mechanical sensors with the vast functionalities available in electronics, we identify a reduced key parameter set of carbon nanotube properties, nanoelectromechanical system design, and operation that steers the sensor’s performance towards system applications, based on open- and closed-loop topologies. Suspended single-walled carbon nanotubes are reviewed in terms of their electromechanical properties with the objective of evaluating orders of magnitude of the electrical actuation and detection mechanisms. Open-loop time-averaging and 1ω or 2ω mixing methods are completed by a new 4ω actuation and detection technique. A discussion on their extension to closed-loop topologies and system applications concludes the analysis, covering signal-to-noise ratio, and the capability to spectrally isolate the motional information from parasitical feedthrough by contemporary electronic read-out techniques. Christian Kauth, Marc Pastre, Jean-Michel Sallese, and Maher Kayal Copyright © 2013 Christian Kauth et al. All rights reserved. Augmented Reality to Support On-Field Post-Impact Maintenance Operations on Thin Structures Thu, 31 Oct 2013 18:40:52 +0000 This paper proposes an augmented reality (AR) strategy in which a Lamb waves based impact detection methodology dynamically interacts with a head portable visualization device allowing the inspector to see the estimated impact position (with its uncertainty) and impact energy directly on the plate-like structure. The impact detection methodology uses a network of piezosensors bonded on the structure to be monitored and a signal processing algorithm (the Warped Frequency Transform) able to compensate for dispersion the acquired waveforms. The compensated waveforms yield to a robust estimation of Lamb waves difference in distance of propagation (DDOP), used to feed hyperbolic algorithms for impact location determination, and allow an estimation of the uncertainty of the impact positioning as well as of the impact energy. The outputs of the impact methodology are passed to a visualization technology that yielding their representation in Augmented Reality (AR) is meant to support the inspector during the on-field inspection/diagnosis as well as the maintenance operations. The inspector, in fact, can see interactively in real time the impact data directly on the surface of the structure. To validate the proposed approach, tests on an aluminum plate are presented. Results confirm the feasibility of the method and its exploitability in maintenance practice. Luca De Marchi, Alessandro Ceruti, Alessandro Marzani, and Alfredo Liverani Copyright © 2013 Luca De Marchi et al. All rights reserved. Development and Application of the Single-Spiral Inductive-Capacitive Resonant Circuit Sensor for Wireless, Real-Time Characterization of Moisture in Sand Sat, 26 Oct 2013 13:52:47 +0000 A wireless, passive embedded sensor was designed and fabricated for monitoring moisture in sand. The sensor, consisted of an inductive-capacitive (LC) resonant circuit, was made of a printed spiral inductor embedded inside sand. When exposed to an electromagnetic field, the sensor resonated at a specific frequency dependent on the inductance of the inductor and its parasitic capacitance. Since the permittivity of water was much higher than dry sand, moisture in sample increased the parasitic capacitance, thus decreasing the sensor’s resonant frequency. Therefore, the internal moisture level of the sample could be easily measured through tracking the resonant frequency using a detection coil. The fabrication process of this sensor is much simpler compared to LC sensors that contain both capacitive and inductive elements, giving it an economical advantage. A study was conducted to investigate the drying rate of sand samples of different grain sizes. The experimental data showed a strong correlation with the actual moisture content in the samples. The described sensor technology can be applied for long term monitoring of localized water content inside soils and sands to understand the environmental health in these media, or monitoring moisture levels within concrete supports and road pavement. Andrew J. DeRouin, Zhanping You, Morgan Hansen, Aboelkasim Diab, and Keat Ghee Ong Copyright © 2013 Andrew J. DeRouin et al. All rights reserved. Radio Context Awareness and Applications Sun, 22 Sep 2013 11:16:40 +0000 The context refers to “any information that can be used to characterize the situation of an entity, where an entity can be a person, place, or physical object.” Radio context awareness is defined as the ability of detecting and estimating a system state or parameter, either globally or concerning one of its components, in a radio system for enhancing performance at the physical, network, or application layers. In this paper, we review the fundamentals of context awareness and the recent advances in the main radio techniques that increase the context awareness and smartness, posing challenges and renewed opportunities to added-value applications in the context of the next generation of wireless networks. Luca Reggiani, Jocelyn Fiorina, Sinan Gezici, Simone Morosi, and Montse Najar Copyright © 2013 Luca Reggiani et al. All rights reserved. Cooperative Spectrum Sensing and Localization in Cognitive Radio Systems Using Compressed Sensing Tue, 03 Sep 2013 11:22:13 +0000 We propose to fuse two main enabling features in cognitive radio systems (CRS): spectrum sensing and location awareness in a single compressed sensing based formalism. In this way, we exploit sparse characteristics of primary units to be detected, both in terms of spectrum used and location occupied. The compressed sensing approach also allows to overcome hardware limitations, in terms of the incapacity to acquire measurements and signals at the Nyquist rate when the spectrum to be scanned is large. Simulation results for realistic network topologies and different compressed sensing reconstruction algorithms testify to the performance and the feasibility of the proposed technique to enable in a single formalism the two main features of cognitive sensor networks. Wael Guibène and Dirk Slock Copyright © 2013 Wael Guibène and Dirk Slock. All rights reserved. A Tent Map Based Conversion Circuit for Robot Tactile Sensor Wed, 28 Aug 2013 15:17:47 +0000 Force and tactile sensors are basic elements for robot perception and control, which call for large range and high-accuracy amplifier. In this paper, a novel conversion circuit for array tactile sensor is proposed by using nonlinear tent map phenomenon, which is characterized by sensitivity to small signal and nonlinear amplifying function. The tent map based conversion circuits can simultaneously realize amplifying and converting functions. The proposed circuit is not only simple but also easy to integrate and produce. It is very suited for multipath signal parallel sampling and converting of large array tactile sensor. Jianxin Liu, Xuan Zhang, Zhiming Li, and Xuling Li Copyright © 2013 Jianxin Liu et al. All rights reserved. Low-Cost MEMS-Based Pedestrian Navigation Technique for GPS-Denied Areas Thu, 22 Aug 2013 12:33:29 +0000 The progress in the micro electro mechanical system (MEMS) sensors technology in size, cost, weight, and power consumption allows for new research opportunities in the navigation field. Today, most of smartphones, tablets, and other handheld devices are fully packed with the required sensors for any navigation system such as GPS, gyroscope, accelerometer, magnetometer, and pressure sensors. For seamless navigation, the sensors’ signal quality and the sensors availability are major challenges. Heading estimation is a fundamental challenge in the GPS-denied environments; therefore, targeting accurate attitude estimation is considered significant contribution to the overall navigation error. For that end, this research targets an improved pedestrian navigation by developing sensors fusion technique to exploit the gyroscope, magnetometer, and accelerometer data for device attitude estimation in the different environments based on quaternion mechanization. Results indicate that the improvement in the traveled distance and the heading estimations is capable of reducing the overall position error to be less than 15 m in the harsh environments. Abdelrahman Ali and Naser El-Sheimy Copyright © 2013 Abdelrahman Ali and Naser El-Sheimy. All rights reserved. Rapid 3D Modeling and Parts Recognition on Automotive Vehicles Using a Network of RGB-D Sensors for Robot Guidance Wed, 21 Aug 2013 13:01:39 +0000 This paper presents an approach for the automatic detection and fast 3D profiling of lateral body panels of vehicles. The work introduces a method to integrate raw streams from depth sensors in the task of 3D profiling and reconstruction and a methodology for the extrinsic calibration of a network of Kinect sensors. This sensing framework is intended for rapidly providing a robot with enough spatial information to interact with automobile panels using various tools. When a vehicle is positioned inside the defined scanning area, a collection of reference parts on the bodywork are automatically recognized from a mosaic of color images collected by a network of Kinect sensors distributed around the vehicle and a global frame of reference is set up. Sections of the depth information on one side of the vehicle are then collected, aligned, and merged into a global RGB-D model. Finally, a 3D triangular mesh modelling the body panels of the vehicle is automatically built. The approach has applications in the intelligent transportation industry, automated vehicle inspection, quality control, automatic car wash systems, automotive production lines, and scan alignment and interpretation. Alberto Chávez-Aragón, Rizwan Macknojia, Pierre Payeur, and Robert Laganière Copyright © 2013 Alberto Chávez-Aragón et al. All rights reserved. Dynamic Compensation for Two-Axis Robot Wrist Force Sensors Sun, 21 Jul 2013 14:11:15 +0000 To improve the dynamic characteristic of two-axis force sensors, a dynamic compensation method is proposed. The two-axis force sensor system is assumed to be a first-order system. The operation frequency of the system is expanded by a digital filter with backward difference network. To filter high-frequency noises, a low-pass filter is added after the dynamic compensation network. To avoid overcompensation, parameters of the proposed dynamic compensation method are defined by trial and error. Step response methods are utilized in dynamic calibration experiments. Compared to experiment data without compensation, the response time of the dynamic compensated data is reduced by 30%~40%. Experiments results demonstrate the effectiveness of our method. Junqing Ma, Aiguo Song, and Dongcheng Pan Copyright © 2013 Junqing Ma et al. All rights reserved. Whole Cell Biosensor Using Anabaena torulosa with Optical Transduction for Environmental Toxicity Evaluation Sun, 21 Jul 2013 12:51:40 +0000 A whole cell-based biosensor using Anabaena torulosa for the detection of heavy metals (Cu, Pb, and Cd), 2,4-dichlorophenoxyacetate (2,4-D), and chlorpyrifos was constructed. The cyanobacteria were entrapped on a cellulose membrane through filtration. Then, the membrane was dried and fixed into a cylindrical well, which was designed to be attached to an optical probe. The probe was connected to fluorescence spectrometer with optical fibre. The presence of the toxicants was indicated by the change of fluorescence emission, before and after the exposure. The linear detection ranges for Cu, Pb, and Cd were 2.5–10.0 µg/L, 0.5–5.0 µg/L, and 0.5–10.0 µg/L, respectively, while 2,4-D and chlorpyrifos shared similar linear ranges of 0.05–0.75 µg/L. The biosensor showed good sensitivity with the lowest limits of detection (LLD) for Cu, Pb, Cd, 2,4-D and chlorpyrifos determined at 1.195 µg/L, 0.100 µg/L, 0.027 µg/L, 0.025 µg/L, and 0.025 µg/L, respectively. The overall reproducibility of the biosensor () was <±6.35%. The biosensor had been tested with different combinations of toxicants, with the results showing predominantly antagonistic responses. The results confirmed that the biosensor constructed in this report is suitable to be used in quantitative and qualitative detections of heavy metals and pesticides. Ling Shing Wong, Yook Heng Lee, and Salmijah Surif Copyright © 2013 Ling Shing Wong et al. All rights reserved. Modeling a Sensor to Improve Its Efficacy Wed, 17 Jul 2013 15:32:27 +0000 Robots rely on sensors to provide them with information about their surroundings. However, high-quality sensors can be extremely expensive and cost-prohibitive. Thus many robotic systems must make due with lower-quality sensors. Here we demonstrate via a case study how modeling a sensor can improve its efficacy when employed within a Bayesian inferential framework. As a test bed we employ a robotic arm that is designed to autonomously take its own measurements using an inexpensive LEGO light sensor to estimate the position and radius of a white circle on a black field. The light sensor integrates the light arriving from a spatially distributed region within its field of view weighted by its spatial sensitivity function (SSF). We demonstrate that by incorporating an accurate model of the light sensor SSF into the likelihood function of a Bayesian inference engine, an autonomous system can make improved inferences about its surroundings. The method presented here is data based, fairly general, and made with plug-and-play in mind so that it could be implemented in similar problems. Nabin K. Malakar, Daniil Gladkov, and Kevin H. Knuth Copyright © 2013 Nabin K. Malakar et al. All rights reserved. AAL Middleware Infrastructure for Green Bed Activity Monitoring Wed, 17 Jul 2013 09:11:44 +0000 This paper describes a service-oriented middleware platform for ambient assisted living and its use in two different bed activity services: bedsore prevention and sleeping monitoring. A detailed description of the middleware platform, its elements and interfaces, as well as a service that is able to classify some typical user's positions in the bed is presented. Wireless sensor networks are supposed to be widely deployed in indoor settings and on people's bodies in tomorrow's pervasive computing environments. The key idea of this work is to leverage their presence by collecting the received signal strength measured among fixed general-purpose wireless sensor devices, deployed in the environment, and wearable ones. The RSS measurements are used to classify a set of user's positions in the bed, monitoring the activities of the user, and thus supporting the bedsores and the sleep monitoring issues. Moreover, the proposed services are able to decrease the energy consumption by exploiting the context information coming from the proposed middleware. Filippo Palumbo, Paolo Barsocchi, Francesco Furfari, and Erina Ferro Copyright © 2013 Filippo Palumbo et al. All rights reserved. A Multimodal Learning System for Individuals with Sensorial, Neuropsychological, and Relational Impairments Sun, 14 Jul 2013 09:22:07 +0000 This paper presents a system for an interactive multimodal environment able (i) to train the listening comprehension in various populations of pupils, both Italian and immigrants, having different disabilities and (ii) to assess speech production and discrimination. The proposed system is the result of a research project focused on pupils with sensorial, neuropsychological, and relational impairments. The project involves innovative technological systems that the users (speech terabits psychologists and preprimary and primary schools teachers) could adopt for training and assessment of language and speech. Because the system is used in a real scenario (the Italian schools are often affected by poor funding for education and teachers without informatics skills), the guidelines adopted are low-cost technology; usability; customizable system; robustness. Sergio Canazza and Gian Luca Foresti Copyright © 2013 Sergio Canazza and Gian Luca Foresti. All rights reserved. Robust Modeling of Low-Cost MEMS Sensor Errors in Mobile Devices Using Fast Orthogonal Search Wed, 10 Jul 2013 12:00:17 +0000 Accessibility to inertial navigation systems (INS) has been severely limited by cost in the past. The introduction of low-cost microelectromechanical system-based INS to be integrated with GPS in order to provide a reliable positioning solution has provided more wide spread use in mobile devices. The random errors of the MEMS inertial sensors may deteriorate the overall system accuracy in mobile devices. These errors are modeled stochastically and are included in the error model of the estimated techniques used such as Kalman filter or Particle filter. First-order Gauss-Markov model is usually used to describe the stochastic nature of these errors. However, if the autocorrelation sequences of these random components are examined, it can be determined that first-order Gauss-Markov model is not adequate to describe such stochastic behavior. A robust modeling technique based on fast orthogonal search is introduced to remove MEMS-based inertial sensor errors inside mobile devices that are used for several location-based services. The proposed method is applied to MEMS-based gyroscopes and accelerometers. Results show that the proposed method models low-cost MEMS sensors errors with no need for denoising techniques and using smaller model order and less computation, outperforming traditional methods by two orders of magnitude. M. Tamazin, A. Noureldin, and M. J. Korenberg Copyright © 2013 M. Tamazin et al. All rights reserved. Growth and Characterization of Single Crystalline Bi4Ge3O12 Fibers for Electrooptic High Voltage Sensors Wed, 10 Jul 2013 09:16:32 +0000 The micro-pulling-down technique for crystalline fiber growth is employed to grow fibers and thin rods of bismuth germanate, Bi4Ge3O12 (BGO), for use in electrooptic high voltage sensors. The motivation is the growth of fibers that are considerably longer than the typical lengths (100–250 mm) that are achieved by more conventional growth techniques like the Czochralski technique. At a given voltage (several hundred kilovolts in high voltage substation applications) longer sensors result in lower electric field strengths and therefore more compact and simpler electric insulation. BGO samples with lengths up to 850 mm and thicknesses from 300 μm to 3 mm were grown. Particular challenges in the growth of BGO fibers are addressed. The relevant optical properties of the fibers are characterized, and the electrooptic response is investigated at voltages up to . Stephan Wildermuth, Klaus Bohnert, Hubert Brändle, Jean-Marie Fourmigue, and Didier Perrodin Copyright © 2013 Stephan Wildermuth et al. All rights reserved. Supervised Expert System for Wearable MEMS Accelerometer-Based Fall Detector Mon, 01 Jul 2013 10:56:58 +0000 Falling is one of the main causes of trauma, disability, and death among older people. Inertial sensors-based devices are able to detect falls in controlled environments. Often this kind of solution presents poor performances in real conditions. The aim of this work is the development of a computationally low-cost algorithm for feature extraction and the implementation of a machine-learning scheme for people fall detection, by using a triaxial MEMS wearable wireless accelerometer. The proposed approach allows to generalize the detection of fall events in several practical conditions. It appears invariant to the age, weight, height of people, and to the relative positioning area (even in the upper part of the waist), overcoming the drawbacks of well-known threshold-based approaches in which several parameters need to be manually estimated according to the specific features of the end user. In order to limit the workload, the specific study on posture analysis has been avoided, and a polynomial kernel function is used while maintaining high performances in terms of specificity and sensitivity. The supervised clustering step is achieved by implementing an one-class support vector machine classifier in a stand-alone PC. Gabriele Rescio, Alessandro Leone, and Pietro Siciliano Copyright © 2013 Gabriele Rescio et al. All rights reserved. Feasibility Investigation of Obstacle-Avoiding Sensors Unit without Image Processing Tue, 25 Jun 2013 10:56:26 +0000 Feasibility of a simple method to detect step height, slope angle, and trench width using four infrared-light-source PSD range sensors is examined, and the reproducibility and accuracy of characteristic parameter detection are also examined. Detection error of upward slope angle is within 2.5 degrees, while it is shown that the detection error of downward slope angle exceeding 20 degrees is very large. In order to reduce such errors, a method to improve range-voltage performance of a range sensor is proposed, and its availability is demonstrated. We also show that increase in trial frequency is a better way, although so as not to increase the detection delay. Step height is identified with an error of ±1.5 mm. It is shown that trench width cannot be reliably measured at this time. It is suggested that an additional method is needed if we have to advance the field of obstacle detection. Yasuhisa Omura, Hiroshi Masuda, and Yoshio Mimura Copyright © 2013 Yasuhisa Omura et al. All rights reserved. Decision Making in Reinforcement Learning Using a Modified Learning Space Based on the Importance of Sensors Wed, 19 Jun 2013 14:02:31 +0000 Many studies have been conducted on the application of reinforcement learning (RL) to robots. A robot which is made for general purpose has redundant sensors or actuators because it is difficult to assume an environment that the robot will face and a task that the robot must execute. In this case, -space on RL contains redundancy so that the robot must take much time to learn a given task. In this study, we focus on the importance of sensors with regard to a robot’s performance of a particular task. The sensors that are applicable to a task differ according to the task. By using the importance of the sensors, we try to adjust the state number of the sensors and to reduce the size of -space. In this paper, we define the measure of importance of a sensor for a task with the correlation between the value of each sensor and reward. A robot calculates the importance of the sensors and makes the size of -space smaller. We propose the method which reduces learning space and construct the learning system by putting it in RL. In this paper, we confirm the effectiveness of our proposed system with an experimental robot. Yasutaka Kishima, Kentarou Kurashige, and Toshihisa Kimura Copyright © 2013 Yasutaka Kishima et al. All rights reserved. Multiple Harmonics Fitting Algorithms Applied to Periodic Signals Based on Hilbert-Huang Transform Thu, 06 Jun 2013 08:25:57 +0000 A new generation of multipurpose measurement equipment is transforming the role of computers in instrumentation. The new features involve mixed devices, such as kinds of sensors, analog-to-digital and digital-to-analog converters, and digital signal processing techniques, that are able to substitute typical discrete instruments like multimeters and analyzers. Signal-processing applications frequently use least-squares (LS) sine-fitting algorithms. Periodic signals may be interpreted as a sum of sine waves with multiple frequencies: the Fourier series. This paper describes a new sine fitting algorithm that is able to fit a multiharmonic acquired periodic signal. By means of a “sinusoidal wave” whose amplitude and phase are both transient, the “triangular wave” can be reconstructed on the basis of Hilbert-Huang transform (HHT). This method can be used to test effective number of bits (ENOBs) of analog-to-digital converter (ADC), avoiding the trouble of selecting initial value of the parameters and working out the nonlinear equations. The simulation results show that the algorithm is precise and efficient. In the case of enough sampling points, even under the circumstances of low-resolution signal with the harmonic distortion existing, the root mean square (RMS) error between the sampling data of original “triangular wave” and the corresponding points of fitting “sinusoidal wave” is marvelously small. That maybe means, under the circumstances of any periodic signal, that ENOBs of high-resolution ADC can be tested accurately. Hui Wang, Zhengshi Liu, Bin Zhu, and Quanjun Song Copyright © 2013 Hui Wang et al. All rights reserved. Evaluation of Circle Diameter by Distributed Tactile Information in Active Tracing Mon, 03 Jun 2013 15:55:11 +0000 Active touch with voluntary movement on the surface of an object is important for human to obtain the local and detailed features on it. In addition, the active touch is considered to enhance the human spatial resolution. In order to improve dexterity performance of multifinger robotic hands, it is necessary to study an active touch method for robotic hands. In this paper, first, we define four requirements of a tactile sensor for active touch and design a distributed tactile sensor model, which can measure a distribution of compressive deformation. Second, we suggest a measurement process with the sensor model, a synthesis method of distributed deformations. In the experiments, a five-finger robotic hand with tactile sensors traces on the surface of cylindrical objects and evaluates the diameters. We confirm that the hand can obtain more information of the diameters by tracing the finger. Hiroyuki Nakamoto, Futoshi Kobayashi, and Fumio Kojima Copyright © 2013 Hiroyuki Nakamoto et al. All rights reserved.