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.

Workspace optimization of parallel robot by using multi-objective genetic algorithm

For the narrow workspace problem of the universal-prismatic-universal(UPU)parallel robotwith fixed orientation,a kind of multi-objective genetic algorithm is studied to optimize the robot’sworkspace.The concept of the effective workspace and its solution method are given.The effectiveworkspace height(EWH)and global condition number index(GCI)of Jacobi matrix are selected asthe optimized objective functions.Setting the robot in two different orientations,the geometric pa-rameters are optimized by the multi-objective genetic algorithm named non-dominated sorting geneticalgorithm II(NSGA-II),and a set of structural parameters is obtained.The optimization results areverified by four indicators with the robot’s moving platform at different orientations.The resultsshow that,after optimization,the fixed-orientation workspace volume,the effective workspace heightand the effective workspace volume increase by 32.4%,17.8%and 72.9%on average,respec-tively.GCI decreases by 6.8%on average.