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Mobility,Constraint Singularity and Isotropy of the 3-R Translational parallel Mechanism

Chinese Journal of Mechanical Engineering 2009年第6期22卷 841-848页

作者： CHEN Qiaohong LI Qinchuan WU Chuanyu LI Yi Provincial Key Laboratory of Modern Textile Machinery Zhejiang Sci-Tech University Hangzhou 310018 China

The non-overconstrained 3-degrees of freedom（DOF） translational parallel mechanism（TPM） has received much attention due to its advantages in reduced cost of fabrication and assembly. Researches are being conducted in the area of type synthesis, kinematic analysis and dimensional synthesis. Mobility, constraint singularity and isotropy of a 3-PRRRR non-overconstrained TPM are studied, where P denote the prismatic pair, R the revolute pair and the overline indicates the same axis direction of the kinematic pair The different arrangements of the three limbs affect the kinematic performance of this kind of TPM. First, the mobility analysis, actuation selection, and the constraint singularity of the general 3-PRRRR TPM are conducted based on screw theory. For a general 3-PRRRR TPM, the three prismatic pairs cannot be chosen as actuators and two kinds of constraint singularities are identified. In the first constraint singularity, the moving platform has four instantaneous DOFs. In the second constraint singularity, the moving platform has five instantaneous DOFs. Then, an orthogonal 3-PRRRR TPM is proposed, which can be actuated by three prismatic pairs and has no constraint singularities. Further, the forward and inverse kinematic analysis of the orthogonal TPM are presented. The input-output equations of the orthogonal TPM are totally decoupled. The full isotropy of the orthogonal TPM is proved by establishing the Jacobian matrix , which is an identity 3x3 diagonal matrix in the whole workspace. The orthogonal 3-PRRRR TPM has great potential in application like fast pick-and-place manipulator, parallel machine and micro-motion manipulator.

关键词： parallel manipulator kinematics screw theory

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Kinematics and Dynamics Hessian Matrices of manipulators Based on Screw Theory

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Chinese Journal of Mechanical Engineering 2015年第2期28卷 226-235页

作者： ZHAO Tieshi GENG Mingchao CHEN Yuhang LI Erwei YANG Jiantao Hebei Provincial Key Laboratory of parallel Robot and Mechatronic System Yanshan University Key Laboratory of Advanced Forging & Stamping Technology and Science of Ministry of Education Yanshan University

The complexity of the kinematics and dynamics of a manipulator makes it necessary to simplify the modeling ***,the traditional representations cannot achieve this because of the absence of coordinate ***,the coordinate invariant method is an important research ***,the rigid-body acceleration,the time derivative of the twist,is proved to be a screw,and its physical meaning is *** on the twist and the rigid-body acceleration,the acceleration of the end-effector is expressed as a linear-bilinear form,and the kinematics Hessian matrix of the manipulator（represented by Lie bracket）is ***,Newton-Euler＇s equation is rewritten as a linear-bilinear form,from which the dynamics Hessian matrix of a rigid body is *** formulae and the dynamics Hessian matrix are proved to be coordinate *** to the principle of virtual work,the dynamics Hessian matrix of the parallel manipulator is gotten and the detailed dynamic model is *** index of dynamical coupling based on dynamics Hessian matrix is *** the end,a foldable parallel manipulator is taken as an example to validate the deduced kinematics and dynamics *** screw theory based method can simplify the kinematics and dynamics of a manipulator,also the corresponding dynamics Hessian matrix can be used to evaluate the dynamical coupling of a manipulator.

关键词： kinematics dynamics Hessian matrix parallel manipulator screw theory

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Design and Analysis for a Three-Rotational-DOF Flight Simulator of Fighter-Aircraft

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Chinese Journal of Mechanical Engineering 2018年第3期31卷 48-59页

作者： Chang-Chun Zhou Yue-Fa Fang Robot Research Center Beijing Jiaotong University

Most of researchers focused on traditional six degrees of freedom(DOF) Stewart flight simulator,which can not be adaptive in fighter?aircraft flight simulator. A three rotational DOF flight simulator of fighter?aircraft based on dou?ble parallel manipulator and hybrid structure is presented. The flight simulator is composed of two identical 3?RRS(revolute?revolute?spherical) spherical parallel manipulators and one cabin,called Twins. The cabin has an additional independent DOF for 360° continuous rotation,so it can be applied as a flight simulator for a fighter?aircraft to achieve spin maneuvering. Because of the introduction of the hybrid structure and double parallel manipulator of themechanism,the redundancy exists with respect to both kinematics and actuation. Kinematics is carried out and Jaco?bian matrix is established by means of screw theory. The inverse kinematics is given out by the analytical method. 64 groups inverse solutions are showed in a table by permutation. Forward kinematics is solved by an e ectively numeri?cal method. The forward numerical method is realized based on the analytically inverse kinematics and Jacobian matrix. The numerical examples show that the forward numerical method can be used in real?time control. The rollingmotion is considered in forward kinematics and a numerical example is given out. The proposed flight simulator can spin and there are three rotational DOF with a hybrid structure so that the novel flight simulator can be used in the field of the fighter?aircraft for pilots to train.

关键词： parallel manipulator Hybrid mechanisms Actuation redundancy Flight simulator Kinematics Screw theory Jacobian matrix

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Design and Control of an Assistive Device for the Study of the Post-stroke Sit-To-Stand Movement

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Journal of Bionic Engineering 2018年第4期15卷 647-660页

作者： Benyamine Allouche Amal Saade Antoine Dequidt Laurent Vermeiren Olivier Remy-Neris LAMIH UMR CNRS 8201 Valenciennes University Le Mont Houy 59313 Valenciennes Cedex 9 France Brest hospital Department of Physical Medicine and Rehabilitation 2 Avenue Foch 29200 Brest France

Every year more than 5 million people worldwide become hemiplegic as a direct consequence of stroke. This neurological deficiency, often leads to a partial or a total loss of standing up abilities and/or ambulation skills. In order to propose new supporting solutions lying between the wheelchair and the walker, this paper presents a technological strategy for designing an assistive device for a biomechanical study of the Sit-To-Stand movement （STS）. The control algorithms are implemented in TwinCAT runtime environment. The communi- cation between the component and the control computer is ensured via the EtherCAT fieldbus. The aim of this architecture lies in the fact that it allows a quick development of a research prototype with the same safety issues found on an industrial machine. An experimental test of the STS strategy is presented and discussed in order to evaluate the strategy.

关键词： sit-to-stand parallel manipulator EtherCAT fieldbus assistive device rehabilitation stroke

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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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Optimal Design of Stewart Platform Safety Mechanism

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Chinese Journal of Aeronautics 2007年第4期20卷 370-377页

作者： Chen Hua Chen Weishan Liu Junkao School of Mechatronics Engineering Harbin Institute of Technology Harbin 150001 China

A safety mechanism capable of moving at will within the range of its whole link lengths is designed based on the link space. Sixteen extreme poses are obtained in a Stewart platform. The singular points of the extreme poses are solved by using homotopy method as well as the judgment condition of singular points, and thereby the maximum link lengths are achieved. The rotation angles of joints and the distances between two neighboring links are analyzed in a calculation example in which that the mechanism moves among the extreme poses is assumed. Then an algorithm to test the safety mechanism is presented taking the constraint conditions into account. A safety mechanism having optimal properties of global movement is worked out by optimizing all structural parameters through minimizing the average condition number of extreme poses.

关键词： parallel manipulator safety mechanism optimal design Stewart platform

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Singular Assembly Configurations and Configuration Bifurcation Characteristics of the Semi-regular Hexagons 6-6 Gough-Stewart manipulator

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Chinese Journal of Mechanical Engineering 2009年第6期22卷 810-821页

作者： LI Yutong WANG Yuxin HUANG Zhen PAN Shuangxia Institute of Mechanical Design Zhejiang University Hangzhou 310027 China Robotic Research Center Yanshan University Qinhuangdao 066004 China

It is well known that singular configurations are inherent to parallel manipulators and have serious influences on their properties. Therefore, these singular configurations should be avoided in the design and application of mechanisms. The researches on the singularity identification and distribution have revealed the relations among the six configuration parameters at singular points. Few works have dealt with the relation between the singularity and the input parameters, as wcll as the properties of the manipulator nearby the singularity. In this paper, taking the semi-regular hexagons 6-6 Gough-Stewart manipulator （SRHGSMP） as an example, the configuration bifurcation characteristics going with the input parameters, the assembly configurations at singular points, and the reasons to cause the singularity are analyzed. The research reveals that the number and the combination of the input parameters have great influences on the complexity of the singularity and the curvature radiuses of the configuration curves. Under different number of input parameters, the dimensional-utmost singularity, line vectors correlation singularity and Jacobian matrix correlation singularity can occur individually or jointly. Choosing the adjacent input parameters, the simple singularity and the large singularity-free input parameters zones can be obtained. And selecting multiple input parameters, the self-motion regions and the singularity avoidance errors can be reduced. These new discoveries are valuable and of significance for the trajectory design, the singularity avoidance, and the self-motion control of the parallel manipulator.

关键词： parallel manipulator singular assembly configuration configuration curve

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INVERSE DYNAMIC FORMULATION OF A NOVEL HYBRID MACHINE TOOL

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Chinese Journal of Mechanical Engineering 2003年第2期16卷 184-189页

作者： XieShunqiang WangJinsong WangLiping LongYunjia ZhangLanxia DepartmentofMathematics&Physics HebeiVocational&TechnicalTeachereCollegeQinhuangdao066004China DepartmentofPrecisionInstruments TsinghuaUniversityBeijing100084China CollegeofBasicSciencesandTechnology ChinaAgriculturalUniversityBeijing100083China DepartmentofMathematics&Physics HebeiVocational&TechnicalTeachersCollegeQinhuangdao066004China

In recent years, hybrid devices have increasingly received more ***, few of researchers studied the dynamic analysis. The inverse dynamic analysis of a novelhybrid machine tool designed in Tsinghua University is presented. The hybrid machine tool underconsideration consists of parallel and serial structures, which is based on a new 2-DOF parallelplatform and serial orientations. The kinematics and the dynamic equations are studied first for theparallel structure through Newton-Euler approach. And then, the dynamic analysis for serialstructures is conducted. Finally, a closed-form inverse dynamic formulation is derived by using someelimination techniques. Some simulation results are also given.

关键词： dynamics parallel manipulator hybrid machine tool

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METH0D USED IN SINGULARITY RESEARCH BASED 0N KINEMATICS AND ITS EXAMPLE IN APPLICATION

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Chinese Journal of Mechanical Engineering 2004年第2期17卷 161-165页

作者： Li Yanwen Huang Zhen Robotics Research Center,Yanshan University,Qinhuangdao 066004, China Robotics Research Center Yanshan University Qinhuangdao 066004

First the kinematic principle of singularity is proved, that is theintersecting point of three normal planes of three velocities at three non-collinear points in arigid body lying in the plane determined by the three corresponding points. It is a sufficient andnecessary condition that the velocities of three non-collinear points in a rigid body can determinea screw motion of the body. Based on this principle, a simple and direct new method to distinguishthe singularity of the parallel manipulator is derived. With this new kinematic method, the 3-RPSparallel manipulator is studied. Its singularity loci are obtained for some orientations for thefirst time and verified with Grassmann line geometry and screw theory and the force Jacobian matrix.

关键词： parallel manipulator 3-RPS Kinematic method Singularity

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KINEMATICS OF 3-DOF PYRAMID manipulator BY PRINCIPAL SCREWS

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Chinese Journal of Mechanical Engineering 2001年第2期14卷 116-120页

作者： Huang Zhen Wang Jing Robotics Research Center, Yanshan University 燕山大学机器人研究中心河北秦皇岛

Kinematics of a 3 RPS parallel pyramid manipulator are investigated by principal screw. Firstly, the principal screws are identified by quadric degeneration. The planar conics representing the relations between the pitches and the three linear inputs are described, and the three dimensional distribution of the axes of all the twists is illustrated. Finally, a numerical example is given successfully.

关键词： parallel manipulator Kinematics Principal screw

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