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Chinese Journal of Mechanical Engineering 2014年第5期27卷 919-927页

作者： LU Yi LI Xuepeng College of Mechanical Engineering Yanshan University Key Laboratory of parallel Robot and Mechatronic System of Hebei Province Key Laboratory of Advanced Forging & Stamping Technology and Science of Ministry of National Education

It is significant to develop a robot hand with high rigidity by a 6-DOF parallel manipulator（PM）.However,the existing6-DOF PMs include spherical joint which has less capability of pulling force bearing,less rotation range and lower precision under alternately heavy loads.A novel 6-DOF PM with three planar limbs and equipped with three fingers is proposed and its kinematics and statics are analyzed systematically.A 3-dimension simulation mechanism of the proposed manipulator is constructed and its structure characteristics is *** kinematics formulae for solving the displacement,velocity,acceleration of the platform,the active legs and the fingers are *** statics formulae are derived for solving the active forces of PM and the finger *** analytic example is given for solving the kinematics and statics of proposed manipulator and the analytic solved results are verified by the simulation *** is proved from the error analysis of analytic solutions and simulation solutions that the derived analytic formulae are correct and provide the theoretical and technical foundations for its manufacturing,control and application.

关键词： parallel manipulator planar limbs finger kinematics statics

Singularity Analysis of a 3-RPS parallel manipulator Using Geometric Algebra

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Chinese Journal of Mechanical Engineering 2015年第6期28卷 1204-1212页

作者： LI Qinchuan XIANG Ji'nan CHAI Xinxue WU Chuanyu Mechatronic Institute Zhejiang Sci-Tech University

Singular configurations must be avoided in path planning and control of a parallel manipulator. However, most studies rarely focus on an overall singularity loci distribution of lower-mobility parallel mechanisms. Geometric algebra is employed in analysis of singularity of a 3-RPS parallel manipulator. Twist and wrench in screw theory are represented in geometric algebra. Linear dependency of twists and wrenches are described by outer product in geometric algebra. Reciprocity between twists and constraint wrenches are reflected by duality. To compute the positions of the three spherical joints of the 3-RPS parallel manipulator, Tilt-and-Torsion angles are used to describe the orientation of the moving platform. The outer product of twists and constraint wrenches is used as an index for closeness to singularity（ICS） of the 3-RPS parallel manipulator. An overall and thorough perspective of the singularity loci distribution of the 3-RPS parallel manipulator is disclosed, which is helpful to design, trajectory planning and control of this kind of parallel manipulator.

关键词： singularity parallel manipulator geometric algebra

Reciprocal Screw Theory Based Singularity Analysis of a Novel 3-DOF parallel manipulator

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Chinese Journal of Mechanical Engineering 2012年第4期25卷 647-653页

作者： FANG Hairong FANG Yuefa ZHANG Ketao School of Mechanical Electronic and Control engineering Beijing Jiaotong University Beijing 100044 China

Singularity analysis is an essential issue for the development and application of parallel *** of the existing researches focus on the singularity of parallel manipulators are carried out based on the study of Jacobian matrices.A 3-DOF parallel manipulator with symmetrical structure is *** novel parallel manipulator employs only revolute joints and consists of four closed-loop subchains connecting to both base and platform via revolute *** closed-loop subchain in each chain-leg is a spherical 6R *** motion characteristics of the output link in the spherical 6R linkage with symmetrical structure are analyzed based on the interrelationships between screw *** constraints that are exerted on the platform by each chain-leg are investigated applying the concept of generalized kinematic pair in terms of equivalent screw *** the geometric characteristics of the parallel manipulator,the singularity criteria of the parallel manipulator corresponding to different configurations are revealed based on the dependency of screw system and line *** existing conditions of certain configuration that a singularity must occur are *** paper presents a new way of singularity analysis based on disposition of constraint forces on the geometrically identified constraint plane and the proposed approach is capable of avoiding the complexity in solving the Jacobian matrices.

关键词： parallel manipulator singularity screw theory grassmann line geometry

Traversing the singularity hypersurface by applying the input disturbances to 6-SPS parallel manipulator

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第11期9卷 1539-1551页

作者： Yu-tong LI Yu-xin WANG Shuang-xia PAN Rui-qin GUO College of Mechanical Engineering and Energy Zhejiang University Hangzhou 310027 China Department of Mechanical Engineering Tongji University Shanghai 200092 China

The singular points of a 6-SPS Stewart platform are distributed on the multi-dimensional singularity hypersurface in the task-space, which divides the workspace of the manipulator into several singularity-free regions. Because of the motion un- certainty at singular points, while the manipulator traverses this kind of hypersurface from one singularity-free region to another, its motion cannot be predetermined. In this paper, a detailed approach for the manipulator to traverse the singularity hypersurface with its non-persistent configuration is presented. First, the singular point transfer disturbance and the pose disturbance, which make the perturbed singular point transfer horizontally and vertically, respectively, are constructed. Through applying these disturbances into the input parameters within the maximum loss control domain, the perturbed persistent configuration is transformed into its corresponding non-persistent one. Under the action of the disturbances, the manipulator can traverse the singularity hypersurface from one singularity-flee region to another with a desired configuration.

关键词： parallel manipulator Singularity hypersurface Singularity-free moving region

PARAMETRIC IDENTIFICATION OF parallel manipulator WITH REDUNDANCY DRIVEN BY PNEUMATIC MUSCLES

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Chinese Journal of Mechanical Engineering 2008年第1期21卷 66-71页

作者： ZHU Xiaocong TAO Guoliang CAO Jian State Key Laboratory of Fluid Power Transmission and Control Zhejiang University Hangzhou 310027 China

A new parameter estimation algorithm is proposed for parametric identification of a parallel manipulator driven by pneumatic muscles with redundancy. Due to the special physical properties of the parallel manipulator studied, the regression model for parametric identification is characterized by multieollinearity, which will result in unreliable and inaccurate parameter estimations with large eovarianee if the conventional parameter estimation algorithm based on single error minimizing criterion is used. To improve the quality of parameter estimation and achieve high precise posture trajectory tracking control of the parallel manipulator, a new parameter estimation algorithm based on composite error minimizing criterion is developed in need of theoretical contractive forces of pneumatic muscles. The experimental results indicate that the proposed algorithm integrated with adaptive robust control could provide reliable parametric identification and greatly enhance the control accuracy in the trajectory tracking control of the parallel manipulator, and that the variation of known theoretical contractive forces of pneumatic muscles has slight influence on the control performance.

关键词： Pneumatic muscle parallel manipulator Redundancy Parameter estimation

Three-degree-of-freedom parallel manipulator to Track the Sun for Concentrated Solar Power Systems

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Chinese Journal of Mechanical Engineering 2015年第4期28卷 793-800页

作者： ASHITH SHYAM R B GHOSAL A Robotics and Design Lab Indian Institute of Science

In concentrated solar power（CSP） generating stations, incident solar energy is reflected from a large number of mirrors or heliostats to a faraway receiver. In typical CSP installations, the mirror needs to be moved about two axes independently using two actuators in series with the mirror effectively mounted at a single point. A three degree-of-freedom parallel manipulator, namely the 3-RPS parallel manipulator, is proposed to track the sun. The proposed 3-RPS parallel manipulator supports the load of the mirror, structure and wind loading at three points resulting in less deflection, and thus a much larger mirror can be moved with the required tracking accuracy and without increasing the weight of the support structure. The kinematics equations to determine motion of the actuated prismatic joints in the 3-RPS parallel manipulator such that the sun＇s rays are reflected on to a stationary receiver are developed. Using finite element analysis, it is shown that for same sized mirror, wind loading and maximum deflection requirement, the weight of the support structure is between 15% and 60% less with the 3-RPS parallel manipulator when compared to azimuth-elevation or the target-aligned configurations.

关键词： 3-RPS parallel manipulator Heliostat Solar tracking

Inertia Match of a 3-RRR Reconfigurable Planar parallel manipulator

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Chinese Journal of Mechanical Engineering 2009年第6期22卷 791-799页

作者： SHAO Zhufeng TANG Xiaoqiang CHEN Xu WANG Liping Department of Precision Instruments and Mechanology Tsinghua University Beijing 100084 China

Inertia match of the parallel manipulator means the ratio of the inertial load of the parallel manipulator converted to each actuator shaft and the moment of inertia of the actuator is kept within a reasonable range. Currently there are many studies on parallel manipulators, but few mention inertia parameters and inertia match of parallel manipulators. This paper focuses on the inertia characteristics of the 3-RRR reconfigurable planar parallel manipulator. On the basis of the inverse dynamic formulations deduced with the principle of virtual work, the inertia matrix of the 3-RRR planar parallel manipulator in the actuator space is obtained in algebraic form. Then, by unifying the dimension and averaging diagonal elements of the inertia matrix, the equivalent inertia of the parallel manipulator, which is the inertial load of the parallel manipulator converted to each actuator shaft, is determined. By transforming the inertia problem of the 3-RRR parallel manipulator into that of the serial multi-bar manipulator, the practicality of the equivalent inertia deduced by inverse dynamics is demonstrated. According to the physical meaning of the inertia equation, the manipulator is divided in to three parts. Further analysis is carried out on the contribution of each part to the equivalent inertia and their distributions in the required workspace, revealing that the passive links cannot ignored in calculating the equivalent inertia of the parallel manipulator. Finally, the inertia match for the 3-RRR reconfigurable parallel manipulator under three configurations is accomplished, and reducers are selected. The equivalent inertia calculation and the inertial match results illustrate that the inertia math is a necessary step to the design of the parallel manipulator, and inertia parameters dramatically affect dynamic performances of parallel manipulators. Besides, the equivalent inertia and inertial match principles, proposed in the paper, can be widely applied in the dynamic

关键词： inertia match equivalent inertia inverse dynamics parallel manipulator

Kinematic Calibration and Forecast Error Compensation of a 2-DOF Planar parallel manipulator

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Chinese Journal of Mechanical Engineering 2011年第6期24卷 992-998页

作者： CHANG Peng LI Chengrong LI Tiemin Hi-tech Innovation Center Institute of AutomationChinese Academy of SciencesBeijing 100190China Department of Precision Instruments and Mechanology Tsinghua UniversityBeijing 100084China

Due to large workspace,heavy-duty and over-constrained mechanism,a small deformation is caused and the precision of the 2-DOF planar parallel manipulator is *** kinematic calibration cannot compensate the end-effector errors caused by the small *** paper presents a method combined step kinematic calibration and linear forecast real-time error compensation in order to enhance the precision of a two degree-of-freedom(DOF) planar parallel manipulator of a hybrid machine *** the step kinematic calibration phase of the method,the end-effector errors caused by the errors of major constant geometrical parameters is *** step kinematic calibration is based on the minimal linear combinations(MLCs) of the error *** simple and feasible measurements in practice are given,and identification analysis of the set of the MLCs for each measurement is carried *** to identification analysis results,both measurement costs and observability are considered,and a step calibration including step measurement,step identification and step error compensation is *** linear forecast real-time error compensation is used to compensate the end-effector errors caused by other parameters after the step kinematic *** the advantages of the step kinematic calibration and the linear forecast real-time error compensation,a method for improving the precision of the 2-DOF planar parallel manipulator is *** results show that the proposed method is robust and effective,so that the position errors are kept to the same order of the measurement *** presented method is attractive for the 2-DOF planar parallel manipulator and can be also applied to other parallel manipulators with fewer than six DOFs.

关键词： parallel manipulator kinematic calibration error compensation minimal linear combinations (MLCs)

Dynamic Feedforward Control of a Novel 3-PSP 3-DOF parallel manipulator

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Chinese Journal of Mechanical Engineering 2011年第4期24卷 676-684页

作者： HAO Qi GUAN Liwen WANG Jinsong WANG Liping Department of Precision Instruments and Mechanology Tsinghua University Beijing 100084 China Department of Helicopter Mechanical Engineering Institute of Army Aviation Beijing 101123 China

parallel manipulators with less than six degrees of freedom （DOF） have been increasingly used in high-speed hybrid machine tools. The structural features of parallel manipulators are dynamic, a characteristic that is particularly significant when these manipulators are used in high-speed machine tools. However, normal kinematic control method cannot satisfy the requirements of the control system. Many researchers use model-based dynamic control methods, such as the dynamic feedforward control method. However, these methods are rarely used in hybrid machine tools because of the complex dynamic model of the parallel manipulator. In order to study the dynamic control method of parallel manipulators, the dynamic feedforward control method is used in the dynamic control system of a 3-PSP （prismatic-spherical-prismatic） 3-DOF spatial parallel manipulator used as a spindle head in a high-speed hybrid machine tool. Using kinematic analysis as basis and the Newton-Euler method, we derive the dynamic model of the parallel manipulator. Furthermore, a model-based dynamic feedforward control system consisting of both kinematic control and dynamic control subsystems is established. The dynamic control subsystem consists of two modules. One is used to eliminate the influence of the dynamic characteristics of high-speed movement, and the other is used to eliminate the dynamic disturbances in the milling process. Finally, the simulation model of the dynamic feedforward control system of the 3-PSP parallel manipulator is constructed in Matlab/Simulink. The simulations of the control system eliminating the influence of the dynamic characteristics and dynamic disturbances are conducted. A comparative study between the simulations and the normal kinematic control method is also *** simulations prove that the dynamic feedforward control method effectively eliminates the influence of the dynamic disturbances and dynamic characteristics of the parallel manipulator on high-speed m

关键词： parallel manipulator dynamic feedforward control high-speed hybrid machine tool

Trajectory Tracking of a Planer parallel manipulator by Using Computed Force Control Method

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Chinese Journal of Mechanical Engineering 2017年第2期30卷 449-458页

作者： Atilla BAYRAM Department of Mechanical Engineering Yuzuncu YilUniversityVanTurkey

Despite small workspace, parallel manipulators have some advantages over their serial counterparts in terms of higher speed, acceleration, rigidity, accuracy, manufacturing cost and payload. Accordingly, this type of manipulators can be used in many applications such as in high-speed machine tools, tuning machine for feeding, sensitive cutting, assembly and packaging. This paper presents a special type of planar parallel manipulator with three degrees of freedom. It is constructed as a variable geometry truss generally known planar Stewart platform. The reachable and orientation workspaces are obtained for this manipulator. The inverse kinematic analysis is solved for the trajectory tracking according to the redundancy and joint limit avoidance. Then, the dynamics model of the manipulator is established by using Virtual Work method. The simulations are performed to follow the given planar trajectories by using the dynamic equations of the variable geometry truss manipulator and computed force control method. In computed force control method, the feedback gain matrices for PD control are tuned with fixed matrices by trail end error and variable ones by means of optimization with genetic algorithm.

关键词： parallel manipulator Variable geometry truss manipulator Planar Stewart platform. Dynamic analysis Computed force control Genetic algorithm