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Virtual Constraint Based Control of Bounding Gait of Quadruped Robots

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Journal of Bionic Engineering 2017年第2期14卷 218-231页

作者： Qingyu Liu Xuedong Chen Bin Han zhiwei luo Xin luo State Key Laboratory of Digital Manufacturing Equipment and Technology Huazhong University of Science and Technology Wuhan 430074 China

This paper presents a control approach for bounding gait of quadruped robots by applying the concept of Virtual Constraints （VCs）. A VC is a relative motion relation between two related joints imposed to the robots in terms of a specified gait, which can drive the robot to run with desired gait. To determine VCs for highly dynamic bounding gait, the limit cycle motions of the passive dynamic model of bounding gait are analyzed. The leg length and hip/shoulder angle trajectories corresponding to the limit cycles are parameterized by leg angles using 4 th-order polynomials. In order to track the calculated periodic motions, the polynomials are imposed on the robot as virtual motion constraints by a high-level state machine controller. A bounding speed feedback strategy is introduced to stabilize the robot running speed and enhance the stability. The control approach was applied to a newly designed lightweight bioinspired quadruped robot, AgiDog. The experimental results demonstrate that the robot can bound at a frequency up to 5 Hz and bound at a maximum speed of 1.2 m·s^-1 in sagittal plane with a Froude number approximating to 1.

关键词： bioinspired quadruped bounding gait virtual constraints passive dynamics

Learning Control of Quadruped Robot Galloping

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Journal of Bionic Engineering 2018年第2期15卷 329-340页

作者： Qingyu Liu Xuedong Chen Bin Han zhiwei luo Xin luo State Key Laboratory of Digital Manufacturing Equipment and Technology Huazhong University of Science and Technology Wuhan 430074 China

Achieving galloping gait in quadruped robots is challenging, because the galloping gait exhibits complex dynamical behaviors of a hybrid nonlinear under-actuated dynamic system. This paper presents a learning approach to quadruped robot galloping control. The control function is obtained through directly approximating real gait data by learning algorithm, without consideration of robot＇s model and environment where the robot is located. Three motion control parameters are chosen to determine the galloping process, and the deduced control function is learned iteratively with modified Locally Weighted Projection Regression （LWPR） algorithm. Experiments conducted upon the bioinspired quadruped robot, AgiDog, indicate that the robot can improve running performance continuously along the learning process, and adapt itself to model and environment uncertainties.

关键词： quadruped gallop dynamic running LWPR learning bioinspiration

Formation of defects in selective laser melted Inconel 718 and its correlation with mechanical properties through dimensionless numbers

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Science China(Physics,Mechanics & Astronomy) 2022年第5期65卷 58-74页

作者： zhiwei luo Zekun Wang Zhenyu Yan Jing Chen Shuguang Li Moubin Liu Capital Aerospace Machinery Co.Ltd. Beijing 100706China State Key Laboratory for Turbulence and Complex Systems Department of Mechanics and Engineering SciencePeking UniversityBeijing 100871China College of Engineering Peking UniversityBeijing 100187China Nanchang Innovation Institute Peking UniversityNanchang 330008China

This paper presents a profound study on the formation of three typical types of defects(i.e.,lack of fusion,keyholes,and gas pores)observed in selective laser melting(SLM)printed Inconel 718 samples,along with their correlations with mechanical properties of the *** tomography,scanning electron microscopy,and mechanical property tests revealed that the three types of defects fall into three stages of porosity evolution classified by recently-proposed dimensionless numbersηm(melting efficiency)andηv(vaporization efficiency).Meanwhile,experimental tests verified that the mechanical properties of products,such as strength and elongation,are remarkably sensitive to lack of ***,these properties are slightly affected by the keyholes and gas *** optimal process window characterized by dimensionless numbers is realized by adjusting the processing parameters and employing different *** process window allows products to have relatively low defects and high mechanical performances.A quantitative relation between processing parameters,dimensionless numbers,defects,and mechanical properties is established based on these *** relation,along with the optimal process window,is believed to enhance the quality of SLM products of Inconel 718 alloy and can be further extended to SLM with other metal materials.

关键词： selective laser melting defects formation mechanical properties similarity criterion

Interaction of fatigue crack with vibration and ultrasound in metallic rod and its use for quantitative characterization

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Chinese Journal of Acoustics 2016年第2期35卷 155-166页

作者： LIU Bin GANG Tie WAN Chuhao luo zhiwei LUAN Yilin State Key Laboratory of Advanced Welding and Joining Harbin Institute of Technology School of Materials Science and Engineering Heilongjiang University of Science and Technology

According to the principle of synchronous demodulation, the modulation informa- tion in the output signal of vibro-acoustic modulation test was investigated and the nonlinear interaction of sound and vibration with the crack interface in a metallic rod was analyzed. A swept signal excitation was used to obtain a proper high frequency parameter in the test of alu- minum rod samples with different sizes of cracks and the modulation information in the output signal was analyzed. It was found that the ultrasound wave in the structure can be separated into two parts. One is the wave which passes through the crack interface modulated by the low frequency vibration, and other wave has no any changes. The nonlinear modulation model was modified and a quantitative method for crack detection was proposed. It is demonstrated by comparing with the ultrasonic C-scanning that this method can be used to estimate the fatigue crack size in the metallic rod.

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Passive Velocity Field Control of a Redundant Cable-Driven Robot with Tension Limitations

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Journal of Mechanics Engineering and Automation 2017年第3期7卷 132-144页

作者： CAOSheng luo zhiwei QUAN Changqin Graduate School of System Informatics Kobe University 1-1 Rokkodai-cho Nada-ku Kobe 65 7-8501 Japan

This paper proposes a novel dynamic control approach for a cable-driven robot with high redundant actuation and cable tension limitations to perform tracking task while interacting with environment. In order for a cable-driven exoskeleton robot to execute the task smoothly and safely, it is necessary to consider the tracking motion performance as well as passivity when interacting with the environment under the conditions of the actuation cables＇ redundancy and the pulling limitation. With the additional consideration of the maximum limitation of the cable tension, cable-driven robot actually can only apply a certain range of feasible wrench on the external environment, which makes the task executed by robot be restricted. In order to make designed wrench be feasible and keep the desired trajectory tracking ability, we present a new control method by extending PVFC （passive velocity field control） method considering tracking stability and passivity. The approach augmented a higher dimensional virtual flywheel dynamics in a specific orthogonal complement space of the cable＇s actuation space. After the final adjustment of the designed wrench with respect to the cable＇s constraint, this method is capable of driving the cable robot to complete the trajectory tracking task and realize the passivity.

关键词： Passivity impedance control model uncertainties.

Impacts and Utilization of Electric Vehicles Integration Into Power Systems

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中国电机工程学报 2012年第4期32卷 I0001-I0026页

作者： HUZechun SONG Yonghua XU zhiwei luo Zhuowei ZHAN Kaiqiao JIA Long Tsinghua University

未来电动汽车(plug-in electric vehicle,PEV)的大规模接入,将给电力系统规划和运行带来不可忽视的影响。从电动汽车充电负荷建模与仿真计算、电动汽车接入对电力系统的影响、电动汽车的充放电控制与利用3大方面,讨论电动汽车接入电网... 详细信息

未来电动汽车(plug-in electric vehicle,PEV)的大规模接入,将给电力系统规划和运行带来不可忽视的影响。从电动汽车充电负荷建模与仿真计算、电动汽车接入对电力系统的影响、电动汽车的充放电控制与利用3大方面,讨论电动汽车接入电网的研究现状。指出电动汽车充电负荷分析应考虑的主要因素;总结电动汽车接入对电源发展、电网运行、充电设施与配电网规划方面的影响,并分析电动汽车有序充电及与电网互动(vehicle to grid,V2G)的研究现状和应用难点。最后,对今后的研究方向进行讨论。

关键词：电力系统规划电动汽车集成电动车辆储能装置 EVS 普及率

An fNIRS Research on Prefrontal Cortex Activity Response to Pleasant Taste

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Journal of Behavioral and Brain Science 2013年第8期3卷 617-623页

作者： Chenghong Hu Yoshiko Kato zhiwei luo Graduate School of Human Development and Environment Kobe University Kobe Japan Graduate School of System Informatics Kobe University Kobe Japan

Functional Near-Infrared Spectroscopy (fNIRS), as a non-invasive neuroimaging technique, was used to monitor the activation of prefrontal lobe on human brain during sweet taste processing. The primary aim of the present study was to find the region of interest (ROI) which is related to sweetness, and make further understanding of the central organization of taste. Based on event-related design, the experiments were performed with 16 volunteers by sweet taste stimulus. It was confirmed that the prefrontal cortex (PFC) is involved in sweet taste processing and fNIRS provided an alternative way for studying taste-related brain function under more natural conditions. This study might be effective for detecting the accession area in the cortex of sweet taste and helpful for studying on human feeding and taste disease like taste dyspepsia or disorder.

关键词： Near-Infrared Spectroscopy Gustation Sweet Taste Prefrontal Cortex

Activation of Human Prefrontal Cortex to Pleasant and Aversive Taste Using Functional Near-Infrared Spectroscopy

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Food and Nutrition Sciences 2014年第2期5卷 236-244页

作者： Chenghong Hu Yoshiko Kato zhiwei luo Graduate School of Human Development and Environment Kobe University Kobe Japan. Graduate School of System Informatics Kobe University Kobe Japan

The aim of the study was to investigate the representation of taste in human prefrontal cortex (PFC), in particular, to compare the representation of a pleasant and an aversive taste using functional near-infrared spectroscopy (fNIRS), so as to obtain further understanding of the taste preference mechanism. The pleasant stimulus used was sweet taste (10% sucrose), and the unpleasant stimulus was sour taste (1% critic acid). Based on event-related design, the experiments were performed with 16 healthy volunteers using the OEG-16 fNIRS sensor. A general linear model was used to analyze the collected data. For the concentration change of oxygenated hemoglobin (ΔoxyHb), we found that significant deactivation was induced by sweetness and sourness in parts of the frontopolar area, orbitofrontal area and dorsolateral prefrontal cortex in bilateral hemisphere of human brain. And the right PFC showed different levels of activation between sweetness and sourness. In addition, brain activities were more sensitive to sourness than sweetness. Finally, we confirmed that the PFC was involved in sweet and sour taste processing, and fNIRS provided an alternative way for studying taste-related brain function under more natural conditions.

关键词： fNIRS Gustatory Sweetness Sourness Prefrontal Cortex

On Energy-based Robust Passive Impedance Control of a Robot Manipulator

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Journal of Mechanics Engineering and Automation 2017年第2期7卷 65-70页

作者： CAO Sheng luo zhiwei QUAN Changqin Graduate School of System Informatics Kobe University 1-1 Rokkodai-cho Nada-ku Kobe 657-8501 Japan

Passivity is an important requirement for a robot to interact with human or other dynamic environments stably and safely as in robotic rehabilitations. Considering the time-varying objective impedance center, under the condition that the robot＇s dynamics is known, previous research has already proposed a passive impedance control approach which adjusts a scaling parameter of the robot＇s desired velocity with respect to the robot＇s mechanic energy so as to maintain the robot＇s passivity. In this research, we furture take into account of the robot＇s dynamical model uncertainties and propose a robust passive impedance control. Computer simulations of a 2-link manipulator interacting with a dynamic wall show the effectiveness of our robust control approach.

关键词： Passivity impedance control model uncertainties.