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Fall preventive gait trajectory planning of a lower limb rehabilitation exoskeleton based on capture point theory Research Article

Mei-ying Deng, Zhang-yi Ma, Ying-nan Wang, Han-song Wang, Yi-bing Zhao, Qian-xiao Wei, Wei Yang, Can-jun Yang,ycj@zju.edu.cn

Frontiers of Information Technology & Electronic Engineering 2019, Volume 20, Issue 10, Pages 1322-1330 doi: 10.1631/FITEE.1800777

Abstract: We study the balance problem caused by forward leaning of the wearer’s upper body during rehabilitation training with a lower limb rehabilitation exoskeleton. The instantaneous is obtained by modeling the human-exoskeleton system and using the theory. By comparing the stability region with instantaneous s of different gait phases, the balancing characteristics of different gait phases and changes to the equilibrium state in the gait process are analyzed. Based on a model of the human-exoskeleton system and the condition of balance of different phases, a trajectory correction strategy is proposed for the instability of the human-exoskeleton system caused by forward leaning of the wearer’s upper body. Finally, the reliability of the trajectory correction strategy is verified by carrying out experiments on the Zhejiang University . The proposed trajectory correction strategy can respond to forward leaning of the upper body in a timely manner. Additionally, in the process of the center of gravity transferred from a double-support phase to a single-support phase, the ratio of gait cycle to zero moment point transfer is reduced correspondingly, and the gait stability is improved.

Keywords：下肢机器人；捕获点；步态相位；人机系统平衡

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A partition approach for robust gait recognition based on gait template fusion Research Articles

Kejun Wang, Liangliang Liu, Xinnan Ding, Kaiqiang Yu, Gang Hu,heukejun@126.com,liuliangliang@hrbeu.edu.cn,dingxinnan@hrbeu.edu.cn,yukaiqiang@hrbeu.edu.cn,hugang@hrbeu.edu.cn

Frontiers of Information Technology & Electronic Engineering 2021, Volume 22, Issue 5, Pages 615-766 doi: 10.1631/FITEE.2000377

Abstract: has significant potential for remote human identification, but it is easily influenced by identity-unrelated factors such as clothing, carrying conditions, and view angles. Many have been presented that can effectively represent gait features. Each gait template has its advantages and can represent different prominent information. In this paper, gait template fusion is proposed to improve the classical representative gait template (such as a ) which represents incomplete information that is sensitive to changes in contour. We also present a partition method to reflect the different gait habits of different body parts of each pedestrian. The fused template is cropped into three parts (head, trunk, and leg regions) depending on the human body, and the three parts are then sent into the convolutional neural network to learn merged features. We present an extensive empirical evaluation of the CASIA-B dataset and compare the proposed method with existing ones. The results show good accuracy and robustness of the proposed method for .

Keywords：步态识别；分块算法；步态模板；步态分析；步态能量图；深度卷积神经网络；生物特征识别；模式识别

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Phase problems in optical imaging Review

Guo-hai SITU, Hai-chao WANG

Frontiers of Information Technology & Electronic Engineering 2017, Volume 18, Issue 9, Pages 1277-1287 doi: 10.1631/FITEE.1700298

Abstract: Because the phase contains more information about the fieldcompared to the amplitude, measurement of the phase is encounteredin many branches of modern science and engineering. Direct measurementof the phase is difficult in the visible regime of the electromagneticwave. One must employ computational techniques to calculate the phasefrom the captured intensity. In this paper, we provide a review ofour recent work on iterative phase retrieval techniques and theirapplications in optical imaging.

Keywords： Phase retrieval Phase imaging Computational imaging Gerchberg-Saxton algorithm Optical encryption Computer-generated hologram

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Sensor-guided gait-synchronization lower-extremity-exoskeleton for potential application on unilateral knee-injured people Research Articles

Donghai WANG

Frontiers of Information Technology & Electronic Engineering 2022, Volume 23, Issue 6, Pages 920-936 doi: 10.1631/FITEE.2000465

Abstract:

This paper presents a gait-synchronization system to help potential unilateral knee-injured people walk normally with a ed (LEE). This relieves the body weight loading on the knee-injured leg and synchronizes its motion with that of the healthy leg during the swing phase of walking. The gait-synchronization system is integrated with a designed to sense the motion/gait of the healthy leg. Guided by the measured joint-angle trajectories, the motorized hip joint lifts the links during walking and synchronizes the knee-injured gait with the healthy gait by a half-cycle delay. The effectiveness of the LEE is illustrated experimentally. We compare the measured joint-angle trajectories between the healthy and knee-injured legs, the simulated knee forces, and the human-exoskeleton interaction forces. The results indicate that the motorized hip-controlled LEE can synchronize the motion/gait of the combined body-ed LEE and injured leg with that of the healthy leg.

Keywords： Sensor-guided Lower-extremity-exoskeleton Body sensor network Gait synchronization Weight-support

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Joint compressed sensing imaging and phase adjustment via an iterative method for multistatic passive radar None

Jue WANG, Jun WANG

Frontiers of Information Technology & Electronic Engineering 2018, Volume 19, Issue 4, Pages 557-568 doi: 10.1631/FITEE.1601423

Abstract: The resolution of the multistatic passive radar imaging system (MPRIS) is poor due to the narrow bandwidth of the signal transmitted by illuminators of opportunity. Moreover, the inaccuracies caused by the inaccurate tracking system or the error position measurement of illuminators or receivers can deteriorate the quality of an image. To improve the performance of an MPRIS, an imaging method based on the tomographic imaging principle is presented. Then the compressed sensing technique is extended to the MPRIS to realize high-resolution imaging. Furthermore, a phase correction technique is developed for compen-sating for phase errors in an MPRIS. Phase errors can be estimated by iteratively solving an equation that is derived by minimizing the mean recovery error of the reconstructed image based on the principle of fixed-point iteration technique. The technique is nonparametric and can be used to estimate phase errors of any form. The effectiveness and convergence of the technique are confirmed by numerical simulations.

Keywords： Multistatic passive radar Compressed sensing Phase adjustment Fixed-point iteration technique

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Recognition of walking environments and gait period by surface electromyography Special Feature on Intelligent Robats

Seulki KYEONG, Wonseok SHIN, Minjin YANG, Ung HEO, Ji-rou FENG, Jung KIM

Frontiers of Information Technology & Electronic Engineering 2019, Volume 20, Issue 3, Pages 342-352 doi: 10.1631/FITEE.1800601

Abstract:

Recognizing and predicting the movement and intention of the wearer in control of an exoskeleton robot is very challenging. It is difficult for exoskeleton robots, which measure and drive human movements, to interact with humans. Therefore, many different types of sensors are needed. When using various sensors, a data design is needed for effective sensing. An electromyographic (EMG) signal can be used to identify intended motion before the actual movement, and the delay time can be shortened via control of the exoskeleton robot. Before using a lower limb exoskeleton to help in walking, the aim of this work is to distinguish the walking environment and gait period using various sensors, including the surface electromyography (sEMG) sensor. For this purpose, a gait experiment was performed on four subjects using the ground reaction force, human–robot interaction force, and position sensors with sEMG sensors. The purpose of this paper is to show progress with the use of sEMG when recognizing walking environments and the gait period with other sensors. For effective data design, we used a combination of sensor types, sEMG sensor locations, and sEMG features. The results obtained using an individual mechanical sensor together with sEMG showed improvement compared to the case of using an individual sensor, and the combination of sEMG and position information showed the best performance in the same number of combinations of three sensors. When four sensor combinations were used, the environment classification accuracy was 96.1%, and the gait period classification accuracy was 97.8%. Vastus medialis (VM) and gastrocnemius (GAS) were the most effective combinations of two muscle types among the five sEMG sensor locations on the legs, and the results were 74.4% in pre-heel contact (preHC) and 71.7% in pre-toe-off (preTO) for environment classification, and 68.0% for gait period classification, when using only the sEMG sensor. The two effective sEMG feature combinations were “mean absolute value (MAV), zero crossings (ZC)” and “MAV, waveform length (WL)”, and the “MAV, ZC” results were 80.0%, 77.1%, and 75.5%. These results suggest that the sEMG signal can be effectively used to control an exoskeleton robot.

Keywords： Walking environment Gait Period Surface electromyography (sEMG) Exoskeleton

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Stepped frequency chirp signal imaging radar jamming using two-dimensional nonperiodic phase modulation Research Article

Qihua WU, Feng ZHAO, Tiehua ZHAO, Xiaobin LIU, Junjie WANG, Shunping XIAO

Frontiers of Information Technology & Electronic Engineering 2023, Volume 24, Issue 3, Pages 433-446 doi: 10.1631/FITEE.2200298

Abstract: obtains high-resolution radar images by synthesizing multiple narrowband chirp pulses. It has been one of the most commonly used waveforms due to its lower demand for radar instant bandwidth. In this paper, we propose a method using two-dimensional against imaging radar. Using the unique property of , the proposed method can generate high-level sidelobes that perform as a special blanket jamming along both the range and azimuth directions and make the target unrecognizable. Then, the influence of different modulation parameters, such as the code width and duty ratio, are further discussed. Based on this, the corresponding parameter design principles are presented. Finally, the validity of the proposed method is demonstrated by the Yake-42 plane data simulation and measured unmanned aerial vehicle data experiment.

Keywords： Radar jamming Stepped frequency chirp signal Nonperiodic phase modulation Wideband radar

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DARPA Robotics Grand Challenge Participation and Ski-Type Gait for Rough-Terrain Walking Article

Hongfei Wang, Shimeng Li, Yuan F. Zheng

Engineering 2015, Volume 1, Issue 1, Pages 36-45 doi: 10.15302/J-ENG-2015006

Abstract:

In this paper, we briefly introduce the history of the Defense Advanced Research Projects Agency (DARPA) Grand Challenge programs with particular focus on the 2012 Robotics Challenge. As members of team DRC-HUBO, we propose different approaches for the Rough-Terrain task, such as enlarged foot pedals and a transformation into quadruped walking. We also introduce a new gait for humanoid robot locomotion to improve stability performance, called the Ski-Type gait. We analyze the stability performance of this gait and use the stability margin to choose between two candidate step sequences, Crawl-1 and Crawl-2. Next, we perform a force/torque analysis for the redundant closed-chain system in the Ski-Type gait, and determine the joint torques by minimizing the total energy consumption. Based on the stability and force/torque analysis, we design a cane length to support a feasible and stable Crawl-2 gait on the HUBO2 humanoid robot platform. Finally, we compare our experimental results with biped walking to validate the Ski-Type gait. We also present our team performance in the trials of the Robotics Challenge.

Keywords： humanoid robot DARPA robotics challenge (DRC) rough-terrain walking Ski-Type gait

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Control strategy for gait transition of an underactuated 3Dbipedal robot Research Articles

Hai-hui YUAN, Yi-min GE, Chun-biao GAN

Frontiers of Information Technology & Electronic Engineering 2019, Volume 20, Issue 8, Pages 1026-1035 doi: 10.1631/FITEE.1800206

Abstract: Significant research interest has recently been attracted to the study of bipedal robots due to the wide variety of their potential applications. In reality, bipedal robots are often required to perform gait transitions to achieve flexible walking. In this paper, we consider the gait transition of a five-link underactuated three-dimensional (3D) bipedal robot, and propose a two-layer control strategy. The strategy consists of a unique, event-based, feedback controller whose feedback gain in each step is updated by an adaptive control law, and a transition controller that guides the robot from the current gait to a neighboring point of the target gait so that the state trajectory can smoothly converge to the target gait. Compared with previous works, the transition controller is parameterized and its control parameters are obtained by solving an optimization problem to guarantee the physical constraints in the transition process. Finally, the effectiveness of the control strategy is illustrated on the underactuated 3D bipedal robot.

Keywords： Gait transition Underactuated three-dimensional biped Event-based feedback controller Adaptive control law

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Studies on Precise Spacecraft Navigation and Positioning Using GPS

Xiang Kaiheng,Qu Guangji

Strategic Study of CAE 2004, Volume 6, Issue 1, Pages 86-91

Abstract:

In this paper, GPS measurement technology, Encke method to solve satellite orbit perturbation and generalized Kalman filtering technology are organically combined together, and an innovative solution— carrier phase & pseudorange integrated dynamic orbit determination (CPPIDOD) for low earth orbit spacecraft on-board autonomous precise navigation and positioning using GPS is presented. Difficult problems of dynamically resolving of integer ambiguities and amendment of cycle slips in the application of GPS carrier phase have been solved. Based on all these, technique of carrier phase & pseudorange integrated dynamic differential relative navigation between two spacecrafts is brought forward. Results of numerical simulation analyses and semi-physical simulation tests show that the solutions presented in this paper are feasible. They can significantly improve the performance of GPS positioning, and their models, algorithms and software are practical for engineering use.

Keywords： spacecraft navigation GPS carrier phase Kalman filtering

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Dual-Comb Ranging Review

Zebin Zhu, Guanhao Wu

Engineering 2018, Volume 4, Issue 6, Pages 772-778 doi: 10.1016/j.eng.2018.10.002

Abstract:

Absolute distance measurement is a fundamental technique in mobile and large-scale dimensional metrology. Dual-comb ranging is emerging as a powerful tool that exploits phase resolution and frequency accuracy for high-precision and fast-rate distance measurement. Using two coherent frequency combs, dual-comb ranging allows time and phase response to be measured rapidly. It breaks through the limitations related to the responsive bandwidth, ambiguity range, and dynamic measurement characteristics of conventional ranging tools. This review introduces dual-comb ranging and summarizes the key techniques for realizing this ranging tool. As optical frequency comb technology progresses, dualcomb ranging shows promise for various professional applications.

Keywords： Ranging Dual-comb interferometer Phase noise Timing jitter Tight-locking Post-correction

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An untethered cable-driven ankle exoskeleton with plantarflexion-dorsiflexion bidirectional movement assistance Research

Tian-miao Wang, Xuan Pei, Tao-gang Hou, Yu-bo Fan, Xuan Yang, Hugh M. Herr, Xing-bang Yang,hherr@media.mit.edu,xingbang@mit.edu

Frontiers of Information Technology & Electronic Engineering 2020, Volume 21, Issue 5, Pages 723-739 doi: 10.1631/FITEE.1900455

Abstract: Lower-limb assisted exoskeletons are widely researched for movement assistance or rehabilitation training. Due to advantages of compliance with human body and lightweight, some prototypes have been developed, but most of these can assist only unidirectional movement. In this paper we present an untethered that can achieve plantarflexion-dorsiflexion bidirectional motion bilaterally using a pair of single motors. The main weights of the exoskeleton, i.e., the motors, power supplement units, and control units, were placed close to the proximity of the human body, i.e., the waist, to reduce the redundant rotation inertia which would apply on the wearer’s leg. A cable force transmission system based on gear-pulley assemblies was designed to transfer the power from the motor to the end-effector effectively. A cable self-tension device on the power output unit was designed to tension the cable during walking. The system based on a foot pressure sensor and an inertial measurement unit (IMU) could identify the gait cycle and gait states efficiently. To validate the power output performance of the exoskeleton, a torque tracking experiment was conducted. When the subject was wearing the exoskeleton with power on, the muscle activity of the soleus was reduced by 5.2% compared to the state without wearing the exoskeleton. This preliminarily verifies the positive assistance effect of our exoskeleton. The study in this paper demonstrates the promising application of a lightweight exoskeleton on human motion augmentation or rehabilitation.

Keywords： Ankle exoskeleton Plantarflexion-dorsiflexion bidirectional assistance Biological gait torque Cable-driven Gait detection

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Orbit determination using incremental phase and TDOA of X-ray pulsar Project supported by the National Natural Science Foundation of China (No. 61401340), the Natural Science Basic Research Plan in Shaanxi Province of China (No. 2016JM6035), the Fundamental Research Funds for the Central Universities, China (No. JB161303), and the Areospace T.T.&C. Innovation Program (No. 201515A) Article

Rong JIAO,Lu-ping XU,Hua ZHANG,Cong LI

Frontiers of Information Technology & Electronic Engineering 2016, Volume 17, Issue 6, Pages 543-552 doi: 10.1631/FITEE.1500365

Abstract: X-ray pulsars offer stable, periodic X-ray pulse sequences that can be used in spacecraft positioning systems. A method using X-ray pulsars to determine the initial orbit of a satellite is presented in this paper. This method suggests only one detector to be equipped on the satellite and assumes that the detector observes three pulsars in turn. To improve the performance, the use of incremental phase in one observation duration is proposed, and the incremental phase is combined with the time difference of arrival (TDOA). Then, a weighted least squares (WLS) algorithm is formulated to calculate the initial orbit. Numerical simulations are performed to assess the proposed orbit determination method.

Keywords： Orbit determination algorithm Single X-ray pulsar detector Phase increment Two-body motion equations Weighted least squares method

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High efficiency spreading spectrum modulation based on double orthogonal complex sequences

Shi Xiaohong

Strategic Study of CAE 2012, Volume 14, Issue 3, Pages 108-112

Abstract:

This paper presents a kind of high efficiency spreading spectrum modulation scheme using double orthogonal complex sequences (DoCS). In this scheme, input data bit-stream is split into many groups with length M. Each group is then mapped into a word of width M and then utilized to select one sequence from 2M-2 DoCS sequences each with length L. After that, the selected sequence is modulated on carrier in QPSK(quadrature phase shift keying) mode. In addition, a novel method named forward phase correction (FPC) is put forward for carrier recovery.

Keywords： modulation and demodulation high efficiency spreading spectrum modulation forward phase correction double orthogonal complex sequences

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Phase synchronization and energy balance between neurons Research Article

Ying XIE, Zhao YAO, Jun MA

Frontiers of Information Technology & Electronic Engineering 2022, Volume 23, Issue 9, Pages 1407-1420 doi: 10.1631/FITEE.2100563

Abstract: A functional neuron has been developed from a simple by incorporating a phototube and a thermistor in different branch circuits. The physical field energy is controlled by the photocurrent across the phototube and the channel current across the thermistor. The firing mode of this neuron is controlled synchronously by external temperature and illumination. There is energy diversity when two functional neurons are exposed to different illumination and temperature conditions. As a result, synapse connections can be created and activated in an adaptive way when field energy is exchanged between neurons. We propose two kinds of criteria to discuss the enhancement of synapse connections to neurons. The energy diversity between neurons determines the increase of the coupling intensity and synaptic current for neurons, and the realization of synchronization is helpful in maintaining energy balance between neurons. The first criterion is similar to the saturation gain scheme in that the coupling intensity is increased with a constant step within a certain period until it reaches energy balance or complete synchronization. The second criterion is that the coupling intensity increases exponentially before reaching energy balance. When two neurons become non-identical, phase synchronization can be controlled during the activation of synapse connections to neurons. For two identical neurons, the second criterion for taming synaptic intensity is effective for reaching complete synchronization and energy balance, even in the presence of noise. This indicates that a synapse connection may prefer to enhance its coupling intensity exponentially. These results are helpful in discovering why synapses are awaken and synaptic current becomes time-varying when any neurons are excited by external stimuli. The potential biophysical mechanism is that energy balance is broken and then synapse connections are activated to maintain an adaptive energy balance between the neurons. These results provide guidance for designing and training intelligent neural networks by taming the coupling channels with gradient energy distribution.

Keywords： Hamilton energy Coupling synchronization Synapse enhancement Neural circuit

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Title Author Date Type Operation

Fall preventive gait trajectory planning of a lower limb rehabilitation exoskeleton based on capture point theory

Mei-ying Deng, Zhang-yi Ma, Ying-nan Wang, Han-song Wang, Yi-bing Zhao, Qian-xiao Wei, Wei Yang, Can-jun Yang,ycj@zju.edu.cn

Journal Article

A partition approach for robust gait recognition based on gait template fusion

Kejun Wang, Liangliang Liu, Xinnan Ding, Kaiqiang Yu, Gang Hu,heukejun@126.com,liuliangliang@hrbeu.edu.cn,dingxinnan@hrbeu.edu.cn,yukaiqiang@hrbeu.edu.cn,hugang@hrbeu.edu.cn

Journal Article

Phase problems in optical imaging

Guo-hai SITU, Hai-chao WANG

Journal Article

Sensor-guided gait-synchronization lower-extremity-exoskeleton for potential application on unilateral knee-injured people

Donghai WANG

Journal Article

Joint compressed sensing imaging and phase adjustment via an iterative method for multistatic passive radar

Jue WANG, Jun WANG

Journal Article

Recognition of walking environments and gait period by surface electromyography

Seulki KYEONG, Wonseok SHIN, Minjin YANG, Ung HEO, Ji-rou FENG, Jung KIM