Optimal design of a 3-leg 6-DOF parallel manipulator for a specific workspace

Researchers seldom study optimum design of a six-degree-of-freedom(DOF) parallel manipulator with three legs based upon the given workspace. An optimal design method of a novel three-leg six-DOF parallel manipulator(TLPM) is presented. The mechanical structure of this robot is introduced, with this structure the kinematic constrain equations is decoupled. Analytical solutions of the forward kinematics are worked out, one configuration of this robot, including position and orientation of the end-effector are graphically displayed. Then, on the basis of several extreme positions of the kinematic performances, the task workspace is given. An algorithm of optimal designing is introduced to find the smallest dimensional parameters of the proposed robot. Examples illustrate the design results, and a design stability index is introduced, which ensures that the robot remains a safe distance from the boundary of sits actual workspace. Finally, one prototype of the robot is developed based on this method. This method can easily find appropriate kinematic parameters that can size a robot having the smallest workspace enclosing a predefined task workspace. It improves the design efficiency, ensures that the robot has a small mechanical size possesses a large given workspace volume, and meets the lightweight design requirements.     

3SPS-3PRS并联机构构型分岔特性

作为轴对称矢量喷管转向控制驱动机构的Gough-Stewart类并联机构,主要工作在奇异位置状态.在该位置,驱动平台能够获得一个绕其法线的自由转动,导致转向控制驱动机构的运动具有不确定性.为此,采用少自由度3SPS-3PRS并联机构限制该自由转动,通过对少自由度3SPS-3PRS并联机构的分岔特性研究发现,该并联机构存在尺度极限奇异位置,且输入参数的取值对由尺度极限奇异位置决定的并联机构的工作空间影响较大.对于给定的矢量状态要求,3SPS-3PRS并联机构的输入参数变化范围有可能超出由尺度极限奇异位置确定的工作空间,导致3PRS运动链产生较大的约束内应力,同时并联机构的工作空间跨越奇异位置使得动平台在通过奇异位置后的构型具有不确定性,因此该并联机构的运动奇异性问题依然存在.     

一种离散驱动蛇形柔性臂的工作空间及优化设计研究

以一种离散驱动蛇形柔性臂为研究对象 ,分析并提出了弯曲型离散驱动机器人工作空间的表达方法。考虑到离散驱动机器人工作空间的离散性 ,为了便于对其运动学参数进行调整 ,以使末端操作器达到新指定的工作位置 ,提出了参数调整“标定”的概念 ,并依据使运动学参数调整值尽量小的优化原则对运动学参数进行了优化设计 ,从而解决了运动学参数设计的冗余度问题。     

基于弦方法的平面并联操作手工作空间分析

采用一种工作空间边界求解的新方法——弦方法对平面并联操作手工作空间的综合问题进行了研究。首先给出了弦方法的基本原理和求解步骤。在平面并联操作手运动学分析的基础上,利用弦方法易于加入约束条件的特点,以机构的灵巧性指标为约束,采用约束跳步优化搜索算法得到具有良好运动学特性的工作空间边界。最后给出了几个具体的设计算例。     

双支链六自由度并联机构尺度设计与性能分析

提出了一种新型六自由度并联机构,该机构由两条运动支链组成,每条支链各包含一个主动球副。与常规六自由度并联机构相比,支链数目的减少可有效增大机构工作空间。基于封闭矢量法求得所提机构的运动学位置逆解,在此基础上分析了机构输入与输出的速度映射关系,建立了机构雅可比矩阵。以工作空间和全域灵巧度为性能评价指标,借助性能图谱法完成了机构尺度设计,基于该尺度参数,对特定工作姿态下的工作空间、灵巧度、承载性能及刚度性能进行了全面研究。最后,搭建了3D打印样机,并对其典型应用场景进行了分析。     

Kinematics and dynamics analysis of the 3PUS-PRU parallel mechanism module designed for a novel 6-DOF gantry hybrid machine tool

A hybrid kinematic machine (HKM) tool with the respective advantages of serial and parallel mechanism is a significant direction for the innovation and development of current advanced sophisticated manufacturing equipment. This paper considers the configuration design, kinematics analysis and dynamics analysis of a 1-translational-3-rotational (1T3R) parallel manipulator, which acts as the main movement module of a novel 6-DOF reconfigurable HKM. The key parallel manipulator with 4 DOFs is composed of one middle PRU kinematic chain and three identical PUS kinematic chains. First, complete kinematics characteristics, including position, velocity, acceleration and jerk, are deeply analyzed by a vector analysis approach. Reachable position workspace and orientation workspace were derived through the workspace boundary search method. Furthermore, complete inverse dynamics model of the 3PUS-PRU parallel manipulator was formulated by virtue of the virtual work principle with considering the inertial and gravitational properties of struts. Finally, a driving power and energy consumption model of each actuated motor under the prescribed trajectory were obtained, resulting in the decouple contribution of each motion part correspondingly. This systematic and rigorous methodology aims at laying a solid theoretical and technical foundation for configuration design and performance analysis of this homologous type HKM.

     

3-PRS微操作器的运动学性质分析

分析了3-PRS微操作器的运动特性，给出了微操作运动的位置公式，并以微位移矩阵条件数及工作空间体积值为度量指标分析了微操作器操作性能与结构参数间的关系。分析表明，条件数取决于操作针长度Le及动平台半径ra之比，且当二者的比值小于5时微操作器具有较好的操作灵巧性；工作空间体积值主要受操作针长度Le动静平台半径ra、rb的影响，且在Le及rb取定值时随ra的减小而增大；支链杆长L对工作空间体积值影响不大。相关的分析结果可应用于3-PRS微操作器的运动学设计。     

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。     

Obtaining configuration space and singularity maps for parallel manipulators

The aim of this paper is to describe a general methodology to obtain the entire set of positions that a parallel manipulator can reach and the workspace regions where the robot is controllable. The workspace is computed using a hybrid analytical-discrete procedure. Next the singularity maps are traced by carrying out a kinematic analysis of the positions obtained. To perform the latter a systematic method has been introduced to obtain the corresponding Jacobian matrices. The result of the whole process is the computation of singularity-free workspace regions, associated with certain working and assembly modes. After that, strategies to enlarge the accessible space are easier to plan and implement. This methodology is based on disassembling the manipulator into a mobile platform and a set of kinematic chains.     

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.     

Optimum design of 6-DOF parallel manipulator with translational/rotational workspaces for haptic device application

This paper proposes an optimum design method that satisfies the desired orientation workspace at the boundary of the translation workspace while maximizing the mechanism isotropy for parallel manipulators. A simple genetic algorithm is used to obtain the optimal linkage parameters of a six-degree-of-freedom parallel manipulator that can be used as a haptic device. The objective function is composed of a desired spherical shape translation workspace and a desired orientation workspace located on the boundaries of the desired translation workspace, along with a global conditioning index based on a homogeneous Jacobian matrix. The objective function was optimized to satisfy the desired orientation workspace at the boundary positions as translated from a neutral position of the increased-entropy mechanism. An optimization result with desired translation and orientation workspaces for a haptic device was obtained to show the effectiveness of the suggested scheme, and the kinematic performances of the proposed model were compared with those of a preexisting base model.     

三自由度冗余驱动并联机构的奇异性和工作空间分析

基于4-SPS/S三自由度冗余驱动并联机构的位置逆解模型,运用微分法推导出了该并联机构的雅可比矩阵,结合Gosselin奇异性分析法和数值分析法,分析了该并联机构的奇异性。随后分析了影响4-SPS/S三自由度冗余驱动并联机构工作空间的主要因素,并对其各支链的行程限制、各球铰副的转角限制和各支链间的尺寸干涉限制等影响因素进行了解析化分析。最后,基于4-SPS/S三自由度冗余驱动并联机构的位置正解模型,设计了该并联机构回转工作空间的求解算法。该算法避免了数值方法及几何方法的复杂性和不确定性,实现了回转工作空间的直观性表达。     

三维平动球平台机器人的位置与工作空间分析

提出一种新颖的三维平动球平台机器人并分析其位置与工作空间问题。该新型机器人是DELTA机器人的一种变异形式，结合其结构布局特点，建立了其位置正反解方程式，分析其工作空间及其影响因素，为其设计和实用化提供理论依据。该新型机器人运动平台无过约束，在三雏平动微动机器人、并联机床和振动环境模拟台等领域有广阔的应用前景。     

空间2自由度冗余驱动并联机构运动学性能分析

面向建筑机器人领域的高性能机械臂需求,提出了一种空间2旋转自由度的3-UPS&U冗余驱动并联机构。基于螺旋理论和修正的G-K公式对机构的整体自由度进行分析,确定了其围绕恰约束支链万向副旋转的运动特性。建立驱动参数与末端参数之间的映射关系,得到其工作空间模型。通过主驱动并联、从动约束串联的独立建模,构造了该并联机构完整的广义雅可比矩阵,进一步得到动平台末端中心点线速度与驱动关节速度之间的无量纲化雅可比矩阵,并据此建立了特定工作空间下机构的灵巧度、承载能力和刚度性能评价指标。最后结果表明,3-UPS&U冗余驱动并联机构进行较高频次上下摆动作业时,在约束支链所布置的对应转轴方向上,具有更佳的综合运动学性能,且能大大降低性能衰减的幅度。     

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.     

6-SPS并联机器人工作空间的边界曲面分析方法

提出了一种并联机器人工作空间分析的解析方法。该方法以曲面分析为基础 ,结合并联机器人的运动特性 ,得到了并联机器人工作空间边界曲面的方程。以 6 - SPS并联机器人为例 ,分析计算了其工作空间。在此基础上 ,描绘出了 6 - SPS并联机器人工作空间边界曲面的投影视图及截面曲线图。分析结果表明 6 - SPS并联机器人的理论工作空间是由 30张曲面片包围而成的闭包     

3-PUU微动并联机构的尺寸型模型及性能图谱

为设计 3 PUU微动并联机构 ,使其获得良好的运动性能 ,提出用杆件无量纲参数建立机构尺寸型模型 ,该模型在有限区间内给出了 3 PUU微动机构所有可能的尺寸组合 ,模型空间中的任意一点代表具有相同或相似运动性能的同一族机构 ;定义反映微动机构运动性能的工作空间体积值、工作空间形状值及条件数 3种性能指标 ,在尺寸型模型中绘制一系列性能图谱 ,通过计算机仿真验证性能图谱的正确性 ,依据图谱提供优化设计机构的方法。     

Motion capability analysis of a quadruped robot as a parallel manipulator

This paper presents the forward and inverse displacement analysis of a quadruped robot MANA as a parallel manipulator in quadruple stance phase, which is used to obtain the workspace and control the motion of the body. The robot MANA designed on the basis of the structure of quadruped mammal is able to not only walk and turn in the uneven terrain, but also accomplish various manipulating tasks as a parallel manipulator in quadruple stance phase. The latter will be the focus of this paper, however. For this purpose, the leg kinematics is primarily analyzed, which lays the foundation on the gait planning in terms of locomotion and body kinematics analysis as a parallel manipulator. When all four feet of the robot contact on the ground, by assuming there is no slipping at the feet, each contacting point is treated as a passive spherical joint and the kinematic model of parallel manipulator is established. The method for choosing six non-redundant actuated joints for the parallel manipulator from all twelve optional joints is elaborated. The inverse and forward displacement analysis of the parallel manipulator is carried out using the method of coordinate transformation. Finally, based on the inverse and forward kinematic model, two issues on obtaining the reachable workspace of parallel manipulator and planning the motion of the body are implemented and verified by ADAMS simulation.     

Kinematic Calibration and Forecast Error Compensation of a 2-DOF Planar Parallel Manipulator

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 affected.The kinematic calibration cannot compensate the end-effector errors caused by the small deformation.This 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 tool.In the step k...     

2-RRC-UPU并联机构及工作空间分析

提出了一种新型三平移三自由度空间并联机器人机构,进行了机构运动输出特性分析及自由度计算,并建立2-RRC-UPU三平移并联机器人机构的位置正、反解方程。得到了该机构的工作空间。在此基础上描绘出了并联机器人工作空间边界曲面及截面视图,分析表明,2-RRC-UPU并联机器人的理论工作空间是部分实心球体,是一种较理想的能实现三维移动并联机构的选型。