The Experts below are selected from a list of 16512 Experts worldwide ranked by ideXlab platform
Yoji Okabe - One of the best experts on this subject based on the ideXlab platform.
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novel real time acousto Ultrasonic Sensors using two phase shifted fiber bragg gratings
Journal of Intelligent Material Systems and Structures, 2014Co-Authors: Qi Wu, Yoji OkabeAbstract:A novel real-time acousto-Ultrasonic Sensor system using a phase-shifted fiber Bragg grating rather than a normal fiber Bragg grating was investigated. The spectrum of the phase-shifted fiber Bragg grating was simulated and analyzed, which indicates that a phase-shifted fiber Bragg grating has superior properties when compared to a normal fiber Bragg grating. Based on theoretical considerations, a novel real-time acousto-Ultrasonic Sensor system was proposed. Two identical 5-mm phase-shifted fiber Bragg gratings, with slightly different Bragg wavelengths, were used as the filter and the Sensor. An amplified spontaneous emission light source and an apodized fiber Bragg grating were connected to illuminate the phase-shifted fiber Bragg gratings. The design allows the strain resulting from the Ultrasonic wave to be precisely received and converted to the fluctuation of the output voltage. An Ultrasonic wave generated in a carbon fiber–reinforced plastic plate using a macrofiber composite actuator was detecte...
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Ultrasonic Sensor employing two cascaded phase shifted fiber bragg gratings suitable for multiplexing
Optics Letters, 2012Co-Authors: Qi Wu, Yoji OkabeAbstract:An Ultrasonic Sensor based on two cascaded phase-shifted fiber Bragg gratings (PS-FBGs) is proposed and demonstrated. In place of an external cavity laser, a broadband amplified spontaneous emission light source is used to demonstrate multiplexing ability suitable for Sensor networks. The system has a high sensitivity to Ultrasonic waves generated by a PZT actuator placed 7.5 cm away from the PS-FBG, because of the steep slope in the center of the PS-FBG spectrum. A second advantage of the phase shift is to reduce the effective Sensor length, leading to the achievement of broadband characteristics. A pencil lead break test was performed and all results are compared to a traditional PZT Sensor.
Qi Wu - One of the best experts on this subject based on the ideXlab platform.
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novel real time acousto Ultrasonic Sensors using two phase shifted fiber bragg gratings
Journal of Intelligent Material Systems and Structures, 2014Co-Authors: Qi Wu, Yoji OkabeAbstract:A novel real-time acousto-Ultrasonic Sensor system using a phase-shifted fiber Bragg grating rather than a normal fiber Bragg grating was investigated. The spectrum of the phase-shifted fiber Bragg grating was simulated and analyzed, which indicates that a phase-shifted fiber Bragg grating has superior properties when compared to a normal fiber Bragg grating. Based on theoretical considerations, a novel real-time acousto-Ultrasonic Sensor system was proposed. Two identical 5-mm phase-shifted fiber Bragg gratings, with slightly different Bragg wavelengths, were used as the filter and the Sensor. An amplified spontaneous emission light source and an apodized fiber Bragg grating were connected to illuminate the phase-shifted fiber Bragg gratings. The design allows the strain resulting from the Ultrasonic wave to be precisely received and converted to the fluctuation of the output voltage. An Ultrasonic wave generated in a carbon fiber–reinforced plastic plate using a macrofiber composite actuator was detecte...
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Ultrasonic Sensor employing two cascaded phase shifted fiber bragg gratings suitable for multiplexing
Optics Letters, 2012Co-Authors: Qi Wu, Yoji OkabeAbstract:An Ultrasonic Sensor based on two cascaded phase-shifted fiber Bragg gratings (PS-FBGs) is proposed and demonstrated. In place of an external cavity laser, a broadband amplified spontaneous emission light source is used to demonstrate multiplexing ability suitable for Sensor networks. The system has a high sensitivity to Ultrasonic waves generated by a PZT actuator placed 7.5 cm away from the PS-FBG, because of the steep slope in the center of the PS-FBG spectrum. A second advantage of the phase shift is to reduce the effective Sensor length, leading to the achievement of broadband characteristics. A pencil lead break test was performed and all results are compared to a traditional PZT Sensor.
Cheong Boon Soh - One of the best experts on this subject based on the ideXlab platform.
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A Multi-Path Compensation Method for Ranging in Wearable Ultrasonic Sensor Networks for Human Gait Analysis
MDPI AG, 2019Co-Authors: Karalikkadan Ashhar, Mohammad Omar Khyam, Cheong Boon SohAbstract:Gait analysis in unrestrained environments can be done with a single wearable Ultrasonic Sensor node on the lower limb and four fixed anchor nodes. The accuracy demanded by such systems is very high. Chirp signals can provide better ranging and localization performance in Ultrasonic systems. However, we cannot neglect the multi-path effect in typical indoor environments for Ultrasonic signals. The multi-path components closer to the line of sight component cannot be identified during correlation reception which leads to errors in the estimated range and which in turn affects the localization and tracking performance. We propose a novel method to reduce the multi-path effect in Ultrasonic Sensor networks in typical indoor environments. A gait analysis system with one mobile node attached to the lower limb was designed to test the performance of the proposed system during an indoor treadmill walking experiment. An optical motion capture system was used as a benchmark for the experiments. The proposed method gave better tracking accuracy compared to conventional coherent receivers. The static measurements gave 2.45 mm standard deviation compared to 10.45 mm using the classical approach. The RMSE between the Ultrasonic gait analysis system and the reference system improved from 28.70 mm to 22.28 mm. The gait analysis system gave good performance for extraction of spatial and temporal parameters
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assessment of foot trajectory for human gait phase detection using wireless Ultrasonic Sensor network
IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2016Co-Authors: Cheong Boon Soh, Erry Gunawan, Kay Soon Low, Rijil ThomasAbstract:This paper presents a new highly accurate gait phase detection system using wearable wireless Ultrasonic Sensors, which can be used in gait analysis or rehabilitation applications. The gait phase detection system uses the foot displacement information during walking to extract the following gait phases: heel-strike, heel-off, toe-off, and mid-swing. The displacement of foot-mounted Ultrasonic Sensor is obtained from several passive anchors placed at known locations by employing local spherical positioning technique, which is further enhanced by the combination of recursive Newton–Gauss method and Kalman Filter. The algorithm performance is examined by comparing with a commercial optical motion tracking system with ten healthy subjects and two foot injured subjects. Accurate estimates of gait cycle (with an error of ${-}{\hbox {0.02}} \pm {\hbox {0.01}}$ s), stance phase(with an error of ${\hbox {0.04}}\pm {\hbox {0.03}}$ s), and swing phase (with an error of ${-}{\hbox {0.05}}\pm {\hbox {0.03}}$ s) compared to the reference system are obtained. We have also investigated the influence of walking velocities on the performance of the proposed gait phase detection algorithm. Statistical analysis shows that there is no significant difference between both systems during different walking speeds. Moreover, we have tested and discussed the possibility of the proposed system for clinical applications by analyzing the experimental results for both healthy and injured subjects. The experiments show that the estimated gait phases have the potential to become indicators for sports and rehabilitation engineering.
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ambulatory measurement of three dimensional foot displacement during treadmill walking using wearable wireless Ultrasonic Sensor network
IEEE Journal of Biomedical and Health Informatics, 2015Co-Authors: Cheong Boon Soh, Erry Gunawan, Kay Soon LowAbstract:Techniques that could be used to monitor human motion precisely are helpful in various applications such as rehabilitation, gait analysis, and athletic performance analysis. This paper focuses on the 3-D foot trajectory measurements based on a wearable wireless Ultrasonic Sensor network. The system consists of an Ultrasonic transmitter (mobile) and several receivers (anchors) with fixed known positions. In order not to restrict the movement of subjects, a radio frequency (RF) module is used for wireless data transmission. The RF module also provides the synchronization clock between mobile and anchors. The proposed system measures the time-of-arrival (TOA) of the Ultrasonic signal from mobile to anchors. Together with the knowledge of the anchor's position, the absolute distance that the signal travels can be computed. Then, the range information defines a circle centered at this anchor with radius equal to the measured distance, and the mobile resides within the intersections of several such circles. Based on the TOA-based tracking technique, the 3-D foot trajectories are validated against a camera-based motion capture system for ten healthy subjects walking on a treadmill at slow, normal, and fast speeds. The experimental results have shown that the Ultrasonic system has sufficient accuracy of net root-mean-square error ( $4.2$ cm) for 3-D displacement, especially for foot clearance with accuracy and standard deviation ( $0.62 \pm 7.48$ mm) compared to the camera-based motion capture system. The small form factor and lightweight feature of the proposed system make it easy to use. Such a system is also much lower in cost compared to the camera-based tracking system.
Peng Yuan - One of the best experts on this subject based on the ideXlab platform.
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directional sensitivity of a mems based fiber optic extrinsic fabry perot Ultrasonic Sensor for partial discharge detection
Sensors, 2018Co-Authors: Peng YuanAbstract:Extrinsic Fabry⁻Perot (FP) interferometric Sensors are being intensively applied for partial discharge (PD) detection and localization. Previous research work has mainly focused on novel structures and materials to improve the sensitivity and linear response of these Sensors. However, the directional response behavior of an FP Ultrasonic Sensor is also of particular importance in localizing the PD source, which is rarely considered. Here, the directional sensitivity of a microelectromechanical system (MEMS)-based FP Ultrasonic Sensor with a 5-mm-thick micromechanical vibrating diaphragm is experimentally investigated. Ultrasonic signals from a discharge source with varying incident angles and linear distances are measured and analyzed. The results show that the Sensor has a 5.90 dB amplitude fluctuation over a ±60d incident range and an exciting capability to detect weak PD signals from 3 m away due to its high signal⁻noise ratio. The findings are expected to optimize the configuration of a Sensor array and accurately localize the PD source.
Ming Han - One of the best experts on this subject based on the ideXlab platform.
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laser frequency noise cancelation in a phase shifted fiber bragg grating Ultrasonic Sensor system using a reference grating channel
IEEE Photonics Journal, 2016Co-Authors: Guigen Liu, Yupeng Zhu, Xiangyu Luo, Ming HanAbstract:In an Ultrasonic Sensor system based on $\pi$ phase-shifted fiber Bragg gratings $(\pi\text{FBGs})$ , a cost-effective way for Sensor demodulation is to set the laser wavelength at the center of the steep spectral slope of the $\pi\text{FBG}$ refection spectrum. Frequency noise of the laser source ultimately limits the signal-to-noise ratio (SNR) of the Sensor system. Here, we demonstrate a noise cancelation method based on a pair of $\pi\text{FBGs}$ , which is capable of improving the SNR of system beyond the limitation set by the laser frequency noise. In this method, one of the gratings is used as the Sensor to detect the acoustic signal, and the other grating, isolated from the signal, is used as a reference that gives the noise information. Employing a data postprocessing method, the noise is subtracted from the original detected signal. We show that the SNR of the Sensor system can be improved by up to 20 dB using this method.
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Adaptive Ultrasonic Sensor using a fiber ring laser with tandem fiber Bragg gratings
Opt. Lett., 2014Co-Authors: Tongqing Liu, Lingling Hu, Ming HanAbstract:We propose and demonstrate an intensity-demodulated fiber-optic Ultrasonic Sensor system that can be self-adaptive to large quasi-static background strain perturbations. The Sensor system is based on a fiber ring laser (FRL) whose laser cavity includes a pair of fiber Bragg gratings (FBGs). Self-adaptive Ultrasonic detection is achieved by a tandem design where the two FBGs are engineered to have differential spectral responses to Ultrasonic waves and are installed side-by-side at the same location on a structure. As a result, Ultrasonic waves lead to relative spectral shifts of the FBGs and modulations to the cold-cavity loss of the FRL. Ultrasonic waves can then be detected directly from the laser intensity variations in response to the cold-cavity loss modulation. The Sensor system is insensitive to quasi-static background strains because they lead to identical responses of the tandem FBGs. Based on the principle, a FRL Sensor system was demonstrated and tested for adaptive Ultrasonic detection when large static strains as well as dynamic sinusoidal vibrations were applied to the Sensor.
