Kinematics of a five-degrees-of-freedom parallel manipulator using screw theory

In this work, the kinematic analysis of a five-degrees-of-freedom decoupled parallel manipulator is approached by means of the theory of screws. The architecture of the parallel manipulator under study is such that the translational motion of the moving platform, with respect to the fixed platform, is controlled by means of a central limb provided with two active prismatic joints while its rotational motion is controlled by means of a three-degrees-of-freedom spherical parallel manipulator. The forward position analysis is presented in semiclosed form solution applying recursively the Sylvester dialytic elimination method. On the other hand, the velocity and acceleration analyses are carried out using the theory of screws. Simple and compact expressions to compute the velocity state and the reduced acceleration state of the moving platform, with respect to the fixed platform, are easily derived in this contribution by taking advantage of the Klein form of the Lie algebra se(3). Finally, only few and slight modifications to the proposed method of kinematic analyses are required in order to approach the position, velocity, and acceleration analyses of parallel manipulators with similar topologies.     

平面并联机器人的速度控制精度分析

对各种衡量机器人灵活性的指标进行了比较,分析了平面并联机器人的基于雅可比矩阵的速度控制精度,并模拟计算了速度控制精度的分布情况。     

6-PUS/UPU并联机器人运动学及工作空间分析

提出和研究了一种新型6-PUS/UPU并联机器人,该机器人结构对称,刚度大,可用于视觉测量、力控制研究、冗余控制研究.首先利用螺旋理论对6-PUS/UPU并联机器人进行了自由度分析,然后根据该机构的几何特点和D-H法对该并联机器人进行了运动学分析,得出了6-PUS/UPU并联机器人的运动学反解,并在此基础上对该并联机器人的工作空间进行了分析.该研究结果对此种机器人的深入研究及该并联机器人的实际应用具有重要理论意义.     

Kinetostatic modelling of a 3-PRR planar compliant parallel manipulator with flexure pivots

Flexure pivots are widely used in long stroke complaint parallel manipulators (CPMs) for their large deformation capacity. However the parasitic motion caused by the flexure pivots cannot be neglected as the rotation angle gets large, which will finally affect the absolute positioning accuracy of the manipulators. In this paper, a modelling approach to calculate the nonlinear kinetostatics of a long stroke planar CPM with flexure pivots is proposed, in which the parasitic motion of the flexure joints are taken into account. The displacement constraint equations and the static equilibrium equations of the CPM are established under the deformed configuration. Finite element analysis (FEA) shows the accuracy and efficiency of the nonlinear kinematic model (NLKM) for both the inverse and forward kinematic analysis. Moreover, the prediction accuracy of the CPM’s kinematic behavior has been improved more than 20 times by employing the NLKM compared with the conventional kinematic model (CKM).     

染色体切割设备的并联宏动平台运动学性能分析

提出了一种新型6-(P-2P-S)并联宏动平台,应用于染色体切割设备可实现微米级高精度定位,该宏动平台在初始正交位姿部分运动解耦,具有装配工艺性好和控制模型简单等特点。基于其结构布局特点,分析了该并联宏动平台的位置问题和运动传递性能,定义了速度传递性能评价指标,同时考虑其结构约束条件,分析了速度传递性能评价指标在姿态空间内的分布情况,为这种并联宏动平台的应用奠定了理论基础。     

Kinematic analysis and optimal design of 3-PPR planar parallel manipulator

This paper proposes a 3-PPR planar parallel manipulator, which consists of three active prismatic joints, three passive prismatic joints, and three passive rotational joints. The analysis of the kinematics and the optimal design of the manipulator are also discussed. The proposed manipulator has the advantages of the closed type of direct kinematics and a void-free workspace with a convex type of borderline. For the kinematic analysis of the proposed manipulator, the direct kinematics, the inverse kinematics, and the inverse Jacobian of the manipulator are derived. After the rotational limits and the workspaces of the manipulator are investigated, the workspace of the manipulator is simulated. In addition, for the optimal design of the manipulator, the performance indices of the manipulator are investigated, and then an optimal design procedure is carried out using Min-Max theory. Finally, one example using the optimal design is presented.     

Kinematics and optimization of 2-DOF parallel manipulator with revolute actuators and a passive leg

In this paper, a 2-DOF planar parallel manipulator with two revolute actuators and one passive constraining leg. The kinematic analysis of the mechanism is analytically performed: the inverse and forward kinematics problems are solved in closed forms, the workspace is derived systematically, and the three kinds of singular configurations are found. The optimal design to determine the geometric parameters and the operating limits of the actuated legs is performed considering the kinematic manipulability and workspace size. These results of the paper show the effectiveness of the presented manipulator.     

排爆机器人机械手运动规划

机械手是排爆机器人关键的部分,机器人作业主要依赖于机械手的运动.介绍了自行研制的机械手运动学构型,重点描述了机械手运动轨迹规划方法并利用Madab软件编程对机械手末端执行器进行了运动学分析,为机械手轨迹控制实现和进一步的动力学研究奠定基础.     

Kinematics and optimization of a 2-DOF parallel manipulator with a passive constraining leg and linear actuators

This paper presents a two degree-of-freedom (DOF) planar parallel manipulator with two linear actuators, whose degree of freedom is dependent on a passive constraining leg connecting the base and the platform. The kinematics of the presented manipulator is first studied: the inverse and forward kinematics problems are solved in the closed form, the practical workspace is described symbolically, the Jacobian matrix is derived, and several singular conditions are discussed. Then, in order to determine the geometric parameters and the operating range of the actuators, the optimization of the mechanism is performed considering its dexterity and stiffness.     

Robust nonlinear PID-like fuzzy logic control of a planar parallel (2PRP-PPR) manipulator

In this paper, a robust nonlinear proportional–integral–derivative (PID)-like fuzzy control scheme is presented and applied to complex trajectory tracking control of a 2PRP-PPR (P-prismatic, R-revolute) planar parallel manipulator (motion platform) with three degrees-of-freedom (DOF) in the presence of parameter uncertainties and external disturbances. The proposed control law consists of mainly two parts: first part uses a feed forward term to enhance the control activity and estimated perturbed term to compensate for the unknown effects namely external disturbances and unmodeled dynamics, and the second part uses a PID-like fuzzy logic control as a feedback portion to enhance the overall closed-loop stability of the system. Experimental results are presented to show the effectiveness of the proposed control scheme.     

解耦三轴平面并联操作手的新机构及分析

为适应大幅面光电产品检测和大型工件操作(加工、焊接、喷涂)时变位姿的需要,提出一种结构简易的3滑块在3个平行导轨上驱动且易实现大工作空间的平面型解耦并联操作手的新型机构,推导了该机构运动学正反解解析公式,计算了末端执行器在定位置和定姿态情况下的工作空间,仿真分析了定姿态时3滑块的运动规律及特性,建立了三维虚拟样机模型,为其物理样机研制、实时控制及工业应用奠定了基础.     

Cusp points and assembly changing motions in the PRR-PR-PRR planar parallel manipulator

Most parallel manipulators have multiple solutions to the direct kinematic problem. The ability to perform assembly changing motions has received the attention of a few researchers. Cusp points play an important role in the kinematic behavior. This study investigates the cusp points and assembly changing motions in a two degrees of freedom planar parallel manipulator. The direct kinematic problem of the manipulator yields a quartic polynomial equation. Each root in the equation determines the assembly configuration, and four solutions are obtained for a given set of actuated joint coordinates. By regarding the discriminant of the repeated roots of the quartic equation as an implicit function of two actuated joint coordinates, the direct kinematic singularity loci in the joint space are determined by the implicit function. Cusp points are then obtained by the intersection of a quadratic curve and a cubic curve. Two assembly changing motions by encircling different cusp points are highlighted, for each pair of solutions with the same sign of the determinants of the direct Jacobian matrices.     

Workspace quality analysis and application for a completely restrained 3-Dof planar cable-driven parallel manipulator

With the advantage of large workspace, low energy consumption and small inertia, the cable-driven parallel manipulator (CDPM) is suitable for heavy workpieces in rapid velocity and acceleration. We present a workspace analysis approach to solve force and torque equilibriums of completely restrained CDPMs. By this approach, not only the distribution but also the value of tensions driven by cables is investigated together. Two new indices, all cable tension distribution index (ACTDI) and area of the global quality workspace (AG) are proposed to evaluate the quality of the workspace. By concentrating on the workspace and its quality combined with the tension characteristics, these criteria are used to determine the optimal workspace in CDPMs. To verify the capacity of the proposed method, simulation examples are presented and the results demonstrate the approach’s effectiveness. In the end, the dimensional design for a planar CDPM is discussed with the indices of workspace quality.     

六自由度机械手的运动学分析

对六自由度机械手建模,利用D-H法建立运动学正模型,并在Paul等人提出的代数法求机械手反解的基础上进行了改进,根据机器人的结构特点提出了一种基于空间几何反解的方法,大大简化了计算过程,实验和仿真结果表明该方法正确可行。     

码垛机械手运动学分析

以自行研制的码垛机械手为分析对象,运用D-H法建立机械手的运动学数学模型,进行正、逆向运动学分析,分别得出了操作臂末端在基坐标系下的位置关系式和各关节的参数变量;最后根据机械手末端速度与关节变量速度之间关系分析,得出机械手的雅可比矩阵和逆雅可比矩阵.     

Dynamic analysis of the 2-DOF planar parallel manipulator of a heavy duty hybrid machine tool

This paper focuses on the dynamic characteristics of the two degree-of-freedom (DOF) planar parallel manipulator of a heavy duty hybrid machine tool. The Newton-Euler approach is employed to derive the inverse dynamic equation of the parallel manipulator. According to the motion planning of the cutting tool, dynamic simulation without cutting force is performed, and the ratio of the masses of counterweights to that of moving parts (not including the counterweight) is optimized. It demonstrates that the manipulator which is designed with over constraint can improve the dynamic behaviour. Furthermore, the cutting force model for face milling is introduced and the dynamic simulation with the dynamic cutting force is carried out. Simulation shows that the oscillation of cutting force is one cause of the vibration of the machine tool in the milling process. In the detailed design, some modification in the structure of the machine tool is made to suppress the vibration.     

3-DOF并联微纳操作器运动学分析

作为一执行机构,微纳操作器是纳米操作系统的关键部件之一。重点分析了3-DOF并联微纳操作器的运动学正解和逆解,推导出了运动学正解的雅可比矩阵。依据微纳操作器的可操作空问最大化,对微纳操作器的雅可比矩阵进行了分析。分析结果对并联微纳机构的参数选择与设计具有一定的指导意义。     

一种新型3T2R并联机器人

理想的少自由度并联机构的所有分支最好具有完全相同的结构,保持结构的对称,以满足各向同性的要求.以单开链支路为单元,提出了一种新型的对称的少自由度的并联机器人机构.研究结果表明,该机构的运动平台具有三维移动和两维转动的5个自由度.     

Position analysis of a 3-DOF parallel manipulator

The forward and inverse kinematics of a 3-DOF parallel mechanism for beam aiming applications is derived in closed form. The mechanism has three actuated arms attached to a base via revolute joints. Another three arms are also attached to an upper platform via passive revolute joints. Each of the three base arms is connected to its respective opposing passive arm via a spherical joint. The platform has three degrees of freedom with respect to the base, two rotational and one radial motion.     

新型装夹机械手的运动学分析与轨迹规划

三自由度机械手广泛地应用于工业领域中,随着工业生产线自动化要求的不断提高,对机械手的需求也越来越广泛.本文所涉及的可调式机械手是一种用于数控机床上的装夹机械手,通过一次装夹完成上料、加工、下料整个过程.采用动力学仿真软件Adams对机械手进行了虚拟样机建模与仿真分析,利用点驱动的方式使机器人按优化后的轨迹运动,得到机械手各关节的运动参数,为机械手的控制提供了重要依据.