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Design Schemes and Comparison Research of the End-effector of Large Space Manipulator

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Chinese Journal of Mechanical Engineering 2012年第4期25卷 674-687页

作者： FENG Fei LIU Yiwei LIU Hong CAI Hegao State Key Laboratory of Robotics and system Harbin Institute of Technology Harbin 150080 China

The end-effector of the large space manipulator is employed to assist the manipulator in handling and manipulating large payloads on ***,there are few researches about the end-effector,and the existing end-effectors have some disadvantages,such as poor misalignment tolerance capability and complex mechanical *** to the end positioning errors and the residual vibration characters of the large space manipulators,two basic performance requirements of the end-effector which include the capabilities of misalignment tolerance and soft capture are *** the end-effector should accommodate the following misalignments of the mechanical *** translation misalignments in axial and radial directions and the angular misalignments in roll,pitch and yaw are ±100 mm,100 mm,±10°,±15°,±15°,*** end-effector schemes are presented and the capabilities of misalignment tolerance and soft capture are analyzed *** three fingers-three petals end-effector and the steel cable-snared end-effector are the most feasible schemes among the seven schemes,and they are designed in *** capabilities of misalignment tolerance and soft capture are validated and evaluated,through the experiment on the micro-gravity simulating device and the dynamic analysis in ADAMS *** results show that the misalignment tolerance capabilities of these two schemes could satisfy the *** the translation misalignment tolerances in axial and radial directions and the angular misalignment tolerances in roll,pitch and yaw of the steel cable-snared end-effector are 30mm,15mm,6°,3° and 3° larger than those of the three fingers-three petals end-effector,*** the contact force of the steel cable-snared end-effector is smaller and smoother than that of the three fingers-three petals *** end-effector schemes and research methods are beneficial to the developments of the large space manipulator end-effctor and t

关键词： end-effector large space manipulator docking mechanism soft capture misalignment tolerance passive compliance active compliance

A policy iteration method for improving robot assembly trajectory efficiency

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Chinese Journal of Aeronautics 2023年第3期36卷 436-448页

作者： Qi ZHANG Zongwu XIE Baoshi CAO Yang LIU State Key Laboratory of Robotics and system Harbin Institute of TechnologyHarbin 150001China

Bolt assembly by robots is a vital and difficult task for replacing astronauts in extravehicular activities(EVA),but the trajectory efficiency still needs to be improved during the wrench insertion into hex hole of *** this paper,a policy iteration method based on reinforcement learning(RL)is proposed,by which the problem of trajectory efficiency improvement is constructed as an issue of RL-based objective ***,the projection relation between raw data and state-action space is established,and then a policy iteration initialization method is designed based on the projection to provide the initialization policy for *** iteration based on the protective policy is applied to continuously evaluating and optimizing the action-value function of all state-action pairs till the convergence is *** verify the feasibility and effectiveness of the proposed method,a noncontact demonstration experiment with human supervision is *** results show that the initialization policy and the generated policy can be obtained by the policy iteration method in a limited number of demonstrations.A comparison between the experiments with two different assembly tolerances shows that the convergent generated policy possesses higher trajectory efficiency than the conservative *** addition,this method can ensure safety during the training process and improve utilization efficiency of demonstration data.

关键词： Bolt assembly Policy initialization Policy iteration Reinforcement learning(RL) Robotic assembly Trajectory efficiency

EXISTENCE OF A GROUND STATE SOLUTION FOR THE CHOQUARD EQUATION WITH NONPERIODIC POTENTIALS

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Acta Mathematica Scientia 2023年第1期43卷 303-323页

作者：罗缘圆高冬梅王俊 institute of Applied system Analysis Jiangsu UniversityZhenjiang212013China

We study the Choquard equation-Δu+V(x)u-b(x)∫R3|u(y)|2/|x-y|dyu,x∈R3,where V(x)=V1(x),b(x)=b1(x)for x1>0 and V(x)=V2(x),b(x)=b2(x)for x1<0,and V1,V2,b1and b2are periodic in each coordinate *** some suitable assumptions,we prove the existence of a ground state solution of the ***,we find some sufficient conditions to guarantee the existence and nonexistence of a ground state solution of the equation.

关键词： Choquard equation ground state solution critical points variational methods

Capillary bridges and capillary forces between two axisymmetric power-law particles

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Particuology 2016年第4期14卷 122-127页

作者： Lefeng Wang Fengting Su Huichao Xu Weibin Rong Hui Xie State Key Laboratory of Robotics and system Harbin Institute of Technology Harbin 150080 China

Capillary interactions are fundamentally important in many scientific and industrial fields. However, most existing models of the capillary bridges and capillary forces between two solids with a mediated liquid, are based on extremely simple geometrical configurations, such as sphere-plate, sphere-sphere, and plate-plate. The capillary bridge and capillary force between two axisymmetric power-law profile particles with a mediated constant-volume liquid are investigated in this study. A dimensionless method is adopted to calculate the capillary bridge shape between two power-law profile particles based on the Young-Laplace equation. The critical rupture criterion of the liquid bridge is shown in four forms that produce consistent results. It was found that the dimensionless rupture distance changes little when the shape index is larger than 2. The results show that the power-law index has a significant influence on the capillary force between two power-law particles. This is directly attributed to the different shape profiles of power-law particles with different indices. Effects of various other parameters such as ratio of the particle equivalent radii, liquid contact angle, liquid volume, and interparticle distance on the capillary force between two power-law particles are also examined.

关键词： Capillary force Power-law profile particles Power-law index Rupture distance

Damping Characteristic Analysis and Optimization of Wind-thermal-bundled Power Transmission by LCC-HVDC systems

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Journal of Modern Power systems and Clean Energy 2024年第1期12卷 299-312页

作者： Liwen Zheng Shiying Ma the Power system Department China Electric Power Research InstituteBeijing 100192China

With the rapid development of renewable energy,wind-thermal-bundled power transmission by line-commutated converter based high-voltage direct current(LCC-HVDC)systems has been widely *** dynamic interaction mechanisms among permanent magnet synchronous generators(PMSGs),synchronous generators(SGs),and LCC-HVDC system become *** deal with this issue,a path analysis method(PAM)is proposed to study the dynamic interaction mechanism,and the damping reconstruction is used to analyze the damping characteristic of the ***,based on the modular modeling,linearized models for the PMSG subsystem,the LCC-HVDC subsystem,and the SG subsystem are ***,based on the closed-loop transfer function diagram of the system,the disturbance transfer path and coupling relationship among subsystems are analyzed by the PAM,and the damping characteristic analysis of the SG-dominated oscillation mode is studied based on the damping *** with the PAM,the small-signal model of the system is obtained and eigenvalue analysis results are ***,the effect of the control parameters on the damping characteristic is analyzed and the conclusions are verified by time-domain ***,the penalty functions of the oscillation modes and decay modes are taken as the objective function,and an optimization strategy based on the Monte Carlo method is proposed to solve the parameter optimization *** simulation results are presented to validate the effectiveness of the proposed strategy.

关键词： Wind-thermal-bundled power transmission line-commutated converter based high-voltage direct current(LCC-HVDC) path analysis method(PAM) damping characteristic analysis Monte Carlo method

Time-Varying Channel Estimation Based on Air-Ground Channel Modelling and Modulated Learning Networks

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Chinese Journal of Electronics 2022年第3期31卷 430-441页

作者： LIU Chunhui WANG Meilin DONG Zanliang WANG Pei institute of Unmanned system Beihang University School of Electronic and Information Engineering Beihang University

To improve the time-varying channel estimation accuracy of orthogonal frequency division multiplexing air-ground datalink in complex environment, this paper proposes a time-varying air-ground channel estimation algorithm based on the modulated learning networks,termed as MB-Chan Est-TV. The algorithm integrates the modulated convolutional neural networks(MCNN) with the bidirectional long short term memory(Bi-LSTM),where the MCNN subnetworks accomplish channel interpolation in frequency domain and compress the network model while the Bi-LSTM subnetworks achieve channel prediction in time domain. Considering the unique characteristics of airframe shadowing for unmanned aircraft systems, we propose to combine the classical 2-ray channel model with the tapped delay line model and present a more realistic channel impulse response samples generation approach, whose code and dataset have been made publicly available. We demonstrate the effectiveness of our proposed approach on the generated dataset, where experimental results indicate that the MB-Chan Est-TV model outperforms existing state-of-the-art methods with a lower estimation error and better bit error ratio performance under different signal to noise ratio *** also analyze the effect of roll angle of the aircraft and the duration percentage of the airframe shadow on the channel estimation.

关键词： OFDM modulation channel prediction realistic channel impulse response samples generation approach modulated learning networks Bi-LSTM subnetworks telecommunication computing air-ground datalink wireless channels 2-ray channel model convolutional neural nets interpolation time-varying channels MB-ChanEst-TV model air-ground channel modelling frequency domain error statistics recurrent neural nets channel estimation modulated convolutional neural networks bidirectional long short term memory learning (artificial intelligence) time-varying air-ground channel estimation algorithm network model channel interpolation MCNN tapped delay line model lower estimation error time-varying channel estimation accuracy

Puncture site decision method for venipuncture robot based on near-infrared vision and multiobjective optimization

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Science China(Technological Sciences) 2023年第1期66卷 13-23页

作者： HE TianBao GUO ChuangQiang JIANG Li State Key Laboratory of Robotics and system Harbin Institute of TechnologyHarbin 150001China

Venipuncture robots have superior perception and stability to humans and are expected to replace manual ***, their use is greatly restricted because they cannot make decisions regarding the puncture sites. Thus, this study presents a multi-information fusion method for determining puncture sites for venipuncture robots to improve their autonomy in the case of limited resources. Here, numerous images have been gathered and processed to establish an image dataset of human forearms for training the U-Net with the soft attention mechanism(SAU-Net) for vein segmentation. Then, the veins are segmented from the images, feature information is extracted based on near-infrared vision, and a multiobjective optimization model for puncture site decision is provided by considering the depth, diameter, curvature, and length of the vein to determine the optimal puncture site. Experiments demonstrate that the method achieves a segmentation accuracy of 91.2% and a vein extraction rate of 86.7%while achieving the Pareto solution set(average time: 1.458 s) and optimal results for each vessel. Finally, a near-infrared camera is applied to the venipuncture robot to segment veins and determine puncture sites in real time, with the results transmitted back to the robot for an attitude adjustment. Consequently, this method can enhance the autonomy of venipuncture robots if implemented dramatically.

关键词： puncture site decision vein extraction near-infrared vision venipuncture robot

Singularity analysis and avoidance for an SSRMS-type reconfigurable space manipulator with a non-spherical wrist and two lockable passive telescopic links

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Chinese Journal of Aeronautics 2024年第8期37卷 435-459页

作者： Zhiyuan ZHAO Xiaohang YANG Yuntao LI Zichun XU Jingdong ZHAO Hong LIU State Key Laboratory of Robotics and system Harbin Institute of TechnologyHarbin 150001China

This study focuses on addressing kinematic singularity analysis and avoidance issues for a space station remote manipulator system(SSRMS)-type reconfigurable space *** manipulator is equipped with a non-spherical wrist and two lockable passive telescopic links(LPTLs),which enable it to have both active revolute and passive prismatic joints and operate in two distinct *** begin with the kinematic singularity analysis,the study derives the differential kinematic equations for the manipulator and identifies the dominant Jacobian matrix that causes ***,an in-depth analysis of singularities from multiple perspectives is ***,a kinematic singularity map method is proposed to capture the distribution of singularities within the reachable ***,the influence of the two LPTLs on singularities is thoroughly ***,a new method based on the matrix rank equivalence principle is introduced to determine singularity conditions,enabling the identification of all the singular configurations for the SSRMS-type reconfigurable ***,this method significantly reduces computational complexity,and the singularity conditions obtained have more concise *** the singularity avoidance problem,a novel method is developed,which simultaneously addresses the requirements of real-time performance,high precision,and the avoidance of both kinematic singularities and joint limit *** from these excellent properties,the proposed method can effectively resolve the singularity issues encountered separately by the SSRMS-type reconfigurable manipulator in its two operational *** typical simulations validate the utility of all the proposed methods.

关键词： Reconfigurable space manipulator Redundant manipulator Kinematics Singularity analysis Singularity avoidance

A Rhythmic Motion Control Method Inspired by Board Shoe Racing for a Weight-Bearing Exoskeleton

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Journal of Bionic Engineering 2022年第2期19卷 403-415页

作者： Tianshuo Wang Jie Zhao Dongbao Sui Sikai Zhao Yanhe Zhu State Key Laboratory of Robotics and system Harbin Institute of TechnologyHarbin 150001China

To ensure the flexible walking of the weight-bearing exoskeleton robot,most researchers control the exoskeleton to follow the wearer’s movements and provide force to maintain the current dynamic ***,due to the limitation of sensing information and computing power,it is difficult for the exoskeleton to provide the wearer reasonable and stable force only based on the dynamic model,especially in switching between swing phase and stance *** by China’s traditional sport named board shoe racing,a walking control method based on the cooperation of the human and the exoskeleton is proposed in this paper for a lower-limb exoskeleton named *** certain conditions,the exoskeleton itself can walk stably depending on the rhythm signals generated by the Central Pattern Generator(CPG).With certain initiative during walking,it can make proper adjustments according to the human *** the help of dynamic simulation software and Genetic Algorithm(GA),the optimized CPG parameters are *** control is introduced to increase the comfort of the *** impedance parameters as well as the CPG parameters are tuned in real time based on *** experiments were conducted with *** results demonstrate that PALExo can effectively assist the wearer walking with a 45-kg payload benefiting from the proposed method.

关键词： Exoskeleton robot Central pattern generator Walking control method