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Analysis and Application of the Singularity Locus of the Stewart Platform

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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Gecko-Like Dry Adhesive Surfaces and Their Applications: A Review

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Journal of Bionic Engineering 2021年第5期18卷 1011-1044页

作者： Wei Wang Yang Liu Zongwu Xie State Key Laboratory of Robotics and System Harbin Institute of TechnologyHarbin 150001China

Gecko has the ability to climb flexibly on various natural surfaces because of its fine layered adhesion system of foot,which has motivated researchers to carry out a lot of researches on *** progresses have been made in the gecko-like dry adhesive surfaces in the past 2 decades,such as the mechanical measurement of adhesive characteristics,the theoretical modeling of adhesive mechanism and the production of synthetic dry adhesive *** application researches have been carried out as *** paper focuses on the investigations made in recent years on the gecko-like dry adhesive surfaces,so as to lay the foundation for further research ***,the adhesion system of gecko’s foot and its excellent adhesive characteristics are reviewed,and the adhesive models describing the gecko adhesion are summarily reviewed according to the diff erent contact ***,some gecko-like dry adhesive surfaces with outstanding adhesive characteristics are ***,some application researches based on the gecko-like dry adhesive surfaces are ***,the full text is summarized and the problems to be solved on the gecko-like dry adhesive surfaces are prospected.

关键词： Gecko adhesion Gecko-like dry adhesive surfaces Climbing robot Robot gripper Medical adhesive tape

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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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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

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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

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Experimental Study on Frog-inspired Swimming Robot Based on Articulated Pneumatic Soft Actuator

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Journal of Bionic Engineering 2020年第2期17卷 270-280页

作者： Jizhuang Fan Shuqi Wang Qingguo Yu Yanhe Zhu State Key Laboratory of Robotics and System Harbin Institute of TechnologyHarbin 150001China

This paper presents a frog-inspired swimming robot based on articulated pneumatic soft *** realize the miniaturization of the robot and enhance its environmental adaptability,combined with the advantages and characteristics of soft materials,an articulated pneumatic soft actuator is designed based on analysis of a frog's propulsion characteristics.A structural model is established to analyse the mechanical properties of the soft *** the goal of making full use of the driving torque of the actuator and enhancing the propulsion efficiency of the robot,the motion trajectories of each joint of the robot are *** on the trajectory planning,the control strategy of the soft actuator is determined to realize the frog-like swimming of the *** torso size after assembly is 0.175 m×0.100 m×0.060 m,which realizes the miniaturization of the frog-inspired *** the movement of the robot,the torso moves stably and flexibly,and can realize continuous linear and turning *** rationality of the structure and trajectory planning are verified by prototype experiments.

关键词： bionic robotic frog articulated pneumatic soft actuator trajectory planning prototype experiment

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Hybrid Static-dynamic Sensation Electrotactile Feedback for Hand Prosthesis Tactile and Proprioception Feedback

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Journal of Bionic Engineering 2023年第1期20卷 267-277页

作者： Bin Yang Li Jiang State Key Laboratory of Robotics and System Harbin Institute of TechnologyHarbin150001China

Tactile and proprioception feedback are essential to myoelectric hand prostheses control for regaining functionality of lost hands of *** studies focus on tactile feedback,while the lack of appropriate multisensory feedback,especially proprioception feedback,limits the grasping ***,a typical non-invasive stimulation scheme for sensation feedback uses stimulation on the stationary site of the skin continuously,which can lead to fatigue and adaptation of sensation,further reduces the feedback consistency,and increases the cognitive burden for the *** the sensitivity and modality matching of sensation,this study presented a multimodal sensations feedback scheme based on hybrid static-dynamic sensation elicited by multisite Transcutaneous Electrical Nerve Stimulation(TENS)to deliver grasping force and joint position *** the proposed scheme,stimulation of single electrode produced only in-loco tactile sensation under the electrode,and the sensation intensity was adjusted according to grasping force;sequential activation of multi-electrodes produced an illusion dynamic sensation of a stimulus moving,and the velocity and direction of movement were adjusted according to finger joint *** test results demonstrated the identifiability of stimulus in the proposed ***,prosthetic hand closed-loop grasping tasks evaluate the effectiveness of the proposed feedback *** results showed that the proposed feedback scheme could substantially improve the grasping accuracy and *** addition,the study outcomes also demonstrated the benefit of artificial proprioception feedback in grasping rapidity and security.

关键词： TENS-Prosthetic hand control-Bioinspired sensation-Multimodal sensations Proprioception feedback Tactilefeedback Myoelectric control

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Design of Robust Controller for Flexible Joint Robot with Nonlinear Friction Characteristics

引用

Journal of Donghua University(English Edition) 2015年第5期32卷 737-742页

作者：陈健葛连正李瑞峰 State Key Laboratory of Robotics and System Harbin Institute of Technology

A robust controller method for flexible joint robot considering the effect caused by nonlinear friction was *** nonlinear friction was denoted as inverse additive output uncertainty relative to the nominal model in our work,based on which the describing function was analyzed in frequency domain,and the weighting function of nonlinear friction was further calculated as well. By combining the friction uncertainty,the mixed sensitivity H∞optimization was proposed as the benchmark for controller design, which also leaded to good performance of robustness. Furthermore,unstructured perturbation to the system was analyzed so that the stability was guaranteed. Simulation results show that the proposed controller can provide excellent tracking and regulation performance.

关键词： robot joints with flexibility nonlinear friction describing function method robust control

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A fast connected components labeling algorithm for binary images

引用

Journal of Harbin Institute of Technology(New Series) 2012年第3期19卷 81-87页

作者：付宜利韩现伟王树国 State Key Laboratory of Robotics and System Harbin Institute of Technology

A fast label-equivalence-based connected components labeling algorithm is proposed in this *** is a combination of two existing efficient methods,which are pivotal operations in two-pass connected components labeling *** is a fast pixel scan method,and the other is an array-based Union-Find data *** scan procedure assigns each foreground pixel a provisional label according to the location of the *** is to say,it labels the foreground pixels following background pixels and foreground pixels in different ways,which greatly reduces the number of neighbor pixel *** array-based Union-Find data structure resolves the label equivalences between provisional labels by using only a single array with path compression,and it improves the efficiency of the resolving procedure which is very time-consuming in general label-equivalence-based *** experiments on various types of images with different sizes show that the proposed algorithm is superior to other labeling approaches for huge images containing many big connected components.

关键词： binary image connected components labeling algorithm Union-Find label-equivalence

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Motion Planning Algorithms of Redundant Manipulators Based on Self-motion Manifolds

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Chinese Journal of Mechanical Engineering 2010年第1期23卷 80-87页

作者： YAO Yufeng ZHAO Jianwen HUANG Bo State Key Laboratory of Robotics Technique and System Harbin Institute of Technology Harbin 150081 China

The current motion planning approaches for redundant manipulators mainly includes two categories： improved gradient-projection method and some other efficiency numerical methods. The former is excessively sensitive to parameters, which makes adjustment difficult; and the latter treats the motion planning as general task by ignoring the particularity, which has good universal property but reduces the solving speed for on-line real-time planning. In this paper, a novel stepwise solution based on self-motion manifold is proposed for motion planning of redundant manipulators, namely, the chief tasks and secondary tasks are implemented step by step. Firstly, the posture tracking of end-effector is achieved accurately by employing the non-redundant joint. Secondly, the end-effector is set to keep stationary. Finally, self-motion of manipulator is realized via additional work on the gradient of redundant joint displacement. To verify this solution, experiments of round obstacle avoiding are carried out via the planar 3 degree-of-~eedom manipulator. And the experimental results indicate that this motion planning algorithm can effectively achieve obstacle avoiding and posture tracking of the end-effector. Compared with traditional gradient projection method, this approach can accelerate the problem-solving process, and is more applicable to obstacle avoiding and other additional work in displacement level.

关键词： redundant manipulators self-motion motion planning inverse kinematics

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