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Simulation and analysis of asteroid force closure anchoring performance based on discrete element method

Chinese Journal of Aeronautics 2023年第8期36卷 381-394页

作者： Tingzhang WANG Qiquan QUAN Hongshuai GAO Mengxue LI Dewei TANG Zongquan DENG State Key Laboratory of Robotics and System Harbin Institute of TechnologyHarbin 150001China

Asteroid exploration is significant for studying the origin of the solar system,establishing planetary defenses,and alleviating the resource crisis of the *** anchoring is the basis of in-situ exploration and resource development and ***,the performance of asteroid force-closure anchoring is investigated using the discrete element *** micro parameters of the simulated materials are calibrated with angle of repose and uniaxial compression experiments,based on which the regional modeling method is adopted to establish the anchoring discrete element *** anchoring experiments are conducted on a self-developed microgravity simulation platform to verify the accuracy of the simulation *** asteroid anchoring simulations are performed to investigate the influence of external force on the anchoring *** analysis of anchoring force varying with time and the interaction between the anchor and regolith particles reveals the influence mechanism of external force direction on the anchoring *** external force direction affects the critical anchoring force by influencing the failure of the force-closure *** comprehensive analysis of simulation results clarifies the variation of the critical anchoring force with the external ***,a stable anchoring region is established,beneficial for asteroid anchoring device design.

关键词： Anchoringforce Asteroid exploration Discrete element method Force closureanchoring Simulationverification

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Capillary Interactions between a Probe Tip and a Nanoparticle

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Chinese Physics Letters 2008年第5期25卷 1795-1798页

作者：孙立宁王乐锋荣伟彬 State Key Laboratory of Robotics and System Harbin Institute of Technology Harbin 150080

To understand capillary interactions between probe tips and nanoparticles under ambient conditions, a theoretical model of capillary forces between them is developed based on the geometric relations. It is found that the contribution of surface tension force to the total capillary force attains to similar order of magnitude as the capillary pressure force in many cases. It is also shown that the tip shape and the radial distance of the meniscus have great influence on the capillary force. The capillary force decreases with the increasing separation distances, and the variance of the contact angles may change the magnitudes of capillary forces several times at large radial distances. The applicability of the symmetric meniscus approximation is discussed.

关键词： ATOMIC-FORCE MICROSCOPE SURFACE NANOMANIPULATION STICTION MEMS

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Autonomous planning and control strategy for space manipulators with dynamics uncertainty based on learning from demonstrations

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Science China(Technological Sciences) 2021年第12期64卷 2662-2675页

作者： LI ChongYang LI ZhiQi JIANG ZaiNan CUI ShiPeng LIU Hong CAI HeGao State Key Laboratory of Robotics and System Harbin Institute of TechnologyHarbin 150001China

Autonomous planning is a significant development direction of the space manipulator,and learning from demonstrations(LfD)is a potential strategy for complex tasks in the ***,separating control from planning may cause large torque fluctuations and energy consumptions,even instability or danger in control of space manipulators,especially for the planning based on the human ***,we present an autonomous planning and control strategy for space manipulators based on LfD and focus on the dynamics uncertainty problem,a common problem of actual *** process can be divided into three stages:firstly,we reproduced the stochastic directed trajectory based on the Gaussian process-based LfD;secondly,we built the model of the stochastic dynamics of the actual manipulator with Gaussian process;thirdly,we designed an optimal controller based on the dynamics model to obtain the improved commanded torques and trajectory,and used the separation theorem to deal with stochastic characteristics during *** evaluated the strategy with locating pre-screwed bolts experiment by Tiangong-2 manipulator system on the *** result showed that,compared with other strategies,the strategy proposed in this paper could significantly reduce torque fluctuations and energy consumptions,and its precision can meet the task requirements.

关键词： space manipulator optimal control dynamics uncertainty learning from demonstrations

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Multi-optimizationofasphericalmechanismforminimallyinvasivesurgery

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Journal of Central South University 2017年第6期24卷 1406-1417页

作者： NIU Guo-jun PAN Bo ZHANG Fu-hai FENG Hai-bo FU Yi-li State Key Laboratory of Robotics and System Harbin Institute of TechnologyHarbin 150001China

In order to obtain the remote center motion(RCM) mechanism with better performance indexes and avoid the collision of multi-manipulators in minimally invasive surgery(MIS), a novel multi-objective optimization model was presented. There were two optimization objectives: a global kinematic performance index and a comprehensive stiffness index. Other indexes to characterize the design requirements such as collision probability, workspace, mechanism parameter, mass, and wall thickness were considered as constraints. Angles between two adjacent joints and cross-section dimensions of links were chosen as the design variables. The non-dominated sorting genetic algorithm II(NSGA-II) was adopted to solve the complex multi-objective optimization problem. Then, a 3-degree of freedom(DoF) MIS robotic prototype based on optimization results has been built up. The experiments to test the spatial position change of the remote center point and to test the absolute position accuracy and repetitive position accuracy of the MIS robot were achieved, and the experimental results meet the requirements of MIS.

关键词： minimally invasive surgery medical robot multi-objective optimization remote centre motion

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A Synthetic Framework for Evaluating and Designing an Anthropomorphic Prosthetic Hand

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Journal of Bionic Engineering 2018年第1期15卷 69-82页

作者： Li Jiang Yuan Liu Dapeng Yang Hong Liu State Key Laboratory of Robotics and System Harbin Institute of Technology Harbin 150080 China

The mimic of aesthetics, fianction, and rehabilitation application makes the prosthetic hand design an interdisciplinary, synthetic work. Prosthetic hands should be designed in a comprehensive consideration with a synthetic framework from multiple areas. In this case, a synthetic framework containing 12 anthropomorphism indexes is established and utilized to understand the human hand characteristic and quantifiably evaluate the anthropomorphism of a prosthetic hand. Our quantified evaluation results show that a Global Anthropomorphic Score （GAS） of the current commercial prosthetic hands is only 45.2%. The compliance, coupling speed ratio and configuration of the Degrees Of Freedom （DOF） are found to be the lowest three anthropomorphism evaluation indexes in all 12 indexes. In addition, a design priority is proposed based on the quantified evaluation results and contributes to a prosthetic hand design. Moreover, our correlation analysis results between each index and GAS show that, compared with the conventional evaluation index-grasp gesture, the rotation axis distribution index has a stronger distinguishing capability to the hand performance. Finally, a flowchart of prosthetic hand design was presented for a designer to design a prosthetic hand with a high anthropomorphism.

关键词： prosthetic hand anthropomorphism quantified evaluation bionic design mechanical implementation rehabilitation

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Three-line structured light vision system for non-cooperative satellites in proximity operations

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Chinese Journal of Aeronautics 2020年第5期33卷 1494-1504页

作者： Yang LIU Zongwu XIE Hong LIU State Key Laboratory of Robotics and System Harbin Institute of TechnologyHarbin 150000China

Adapter ring is a commonly used component in non-cooperative satellites,which has high strength and is suitable to be recognized and grasped by the space *** proximity operations,this circle feature may be occluded by the robot arm or limited field of ***,the captured images may be underexposed when there is not enough *** address these problems,this paper presents a structured light vision system with three line lasers and a monocular *** lasers project lines onto the surface of the satellite,and six break points are formed along both sides of the adapter ring.A closed-form solution for real-time pose estimation is given using these break ***,a virtual structured light platform is constructed to simulate synthetic images of the target *** with the predefined camera parameters and relative positions,the proposed method is demonstrated to be more effective,especially at a close ***,a physical space verification system is set up to prove the effectiveness and robustness of our method under different light *** results indicate that it is a practical and effective method for the pose measurement of on-orbit tasks.

关键词： Adapter ring Line detection Non-cooperative target Pose measurement Space robot Structured light

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A rotary ultrasonic motor using radial bending mode of ring with nested PZT excitation

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2012年第3期13卷 189-196页

作者： Ying-xiang LIU Jun-kao LIU Wei-shan CHEN Xiao-hui YANG State Key Laboratory of Robotics and System Harbin Institute of Technology Horbin 150001 China

This study presents and verifies a new idea for constructing a rotary traveling wave ultrasonic motor （USM） that uses the radial bending mode of a ring. In the new design, 20 trapezoid cross section slots are cut symmetrically in the outer surface of a thick duralumin alloy ring, where 20 PZT stacks are nested. In each slot, two wedging blocks are set between the PZT stack and the two sides of the slot respectively to apply preloading on the PZT ceramics. Two radial bending modes of the stator that have a phase difference of a quarter wavelength on space are generated by using the d33 operating mode of the PZT elements, and then a flexural traveling wave is formed by the superimposing of two standing waves whose amplitudes are equal and phases are different by 90~ temporally. Two conical rotors are pressed to each end of the ring type stator by a coiled spring. The finite element method （FEM） simulation is developed to validate the feasibility of the proposed motor. The maximal speed and torque of the prototype are tested to be 126 r/rain and 0.8 N＇m, respectively.

关键词： Rotary ultrasonic motor Radial bending mode Traveling wave Wedging block clamped structure

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Analysis of reaction torque-based control of a redundant free-floating space robot

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Chinese Journal of Aeronautics 2017年第5期30卷 1765-1776页

作者： Minghe JIN Cheng ZHOU Yechao LIU Hong LIU State Key Laboratory of Robotics and System Harbin Institute of Technology Harbin 150001 China

Owing to the dynamics coupling between a free-floating base and a manipulator, the non-stationary base of a space robot will face the issue of base disturbance due to a manipulator＇s motion. The reaction torque acted on the satellite base＇s centroid is an important index to measure the satellite base＇s disturbance. In this paper, a comprehensive analysis of the reaction torque is made, and a novel way to derive the analytical form of the reaction torque is proposed. In addition,the reaction torque null-space is derived, in which the manipulator＇s joint motion is dynamically decoupled from the motion of the satellite base, and its novel expression demonstrates the equivalence between the reaction torque null-space and the reaction null-space. Furthermore, the reaction torque acted as an optimization index can be utilized to achieve satellite base disturbance minimization in the generalized Jacobian-based end-effector Cartesian path tracking task. Besides, supposing that the redundant degrees of freedom are abundant to achieve reaction torque-based active control, the reaction torque can be used to realize satellite base attitude control, that is, base attitude adjustment or maintenance. Moreover, because reaction torque-based control is a second-order control scheme, joint torque minimization can be regarded as the optimization task in reaction torque-based active or in-active control. A real-time simulation system of a 7-DOF space robot under Linux/RTAI is developed to verify and test the feasibility and reliability of the proposed ideas. Our extensive empirical results demonstrate that the corresponding analysis about the reaction torque is correct and the proposed methods are feasible.

关键词： Attitude control Base disturbance Dynamics modeling Reaction torque Real time simulator Space robot

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Analysis and Application of the Singularity Locus of the Stewart Platform

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Chinese Journal of Mechanical Engineering 2011年第1期24卷 133-140页

作者： MA Jianming HUANG Qitao XIONG Haiguo HAN Junwei State Key Laboratory of Robotics and System Harbin Institute of Technology Harbin 150001 China

The direct use of the determinant of Jacobian matrix being equal to zero for the singularity analysis is generally difficult which is due to complexity of the Jacobian matrix of 6-DOF parallel manipulators,especially for Stewart ***,several scholars make their great contribution to the effective solution of this problem,but neither of them find the right *** paper gives a brief analysis of the kinematics of the Stewart platform and derives the Jacobian matrices of the system through the velocity *** the basis of the traditional classification of singularities,the second type of singularity is *** assumption of any three of the six variables of the Stewart platform as constant is made,then the analytical expression of singularity locus equation of the second type singularity which contains another three pose variables is *** singularity locus is represented in the three-dimensional space through the derived *** correctness and validity of the proposed method are verified through ***,the singularity analysis of an electric Stewart platform in its desired workspace and reachable workspace is ***,one can easily identify whether singularity exists in a given workspace of a Stewart platform and determine whether the existed singularity can be avoided through the proposed *** proposed method also provides theoretical principle for the design and application of the Stewart platform and has great significance for the trajectory planning and control.

关键词： parallel manipulator Stewart platform Jacobian matrix singularity locus workspace

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Adding Sub-chain Method for Structural Synthesis of Planar Closed Kinematic Chains

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Chinese Journal of Mechanical Engineering 2012年第2期25卷 206-213页

作者： DENG Zongquan YANG Fei TAO Jianguo State Key Laboratory of Robotics and System Harbin Institute of TechnologyHarbin 150080China

For at least the past five decades,structural synthesis has been used as a main means of finding better mechanisms with some predefined *** structural synthesis,isomorphism identification is still a problem unsolved well,and to solve this problem is very significant to the design of new *** to the given degree of freedom（DOF） and link connection property of planar closed chain mechanisms,vertex assortment is *** solving the isomorphism problem,a method of the adding sub-chains is proposed with the detailed steps and algorithms in the synthesizing *** this method,the identification code and formation code of every topological structure are achieved,therefore many isomorphic structures could be eliminated in time during structural synthesis by comparing those codes among different topological graphs,resulting in the improvement of synthesizing efficiency and accuracy,and the approach for eliminating rigid sub-chains in and after the synthesizing process is also *** examples are given,including how to add sub-chains,how to detect simple rigid sub-chains and how to obtain identification codes and formulation codes et *** the adding sub-chain method,the relative information of some common topological graphs is given in the form of *** comparison result is coincident with many literatures,so the correctness of the adding sub-chain method is *** method will greatly improve the synthesizing efficiency and accuracy,and has a good potential for application.

关键词： structural synthesis adding sub-chain method identification code formation code rigid sub-chains

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