Kinematic Analysis And Structural Parameters Optimization Of 6-DOF Parallel Platform

In fact,6-DOF parallel platform is also called Stewart parallel manipulator.It is used in various applications due to its high load-carrying capacity,accuracy and stiffness,such as aircraft,manufacturing industry and health care industry.However,the use of such parallel robots is not widespread due to these factors: the limited workspace,high cost,dexterity index and the singularity configurations existing inside the workspace.The parallel platform in this paper is mainly used for positioning of wings and ribs and assembly process of aircraft.The change of the workspace of the platform and dynamic performance has been affected the motion range and accuracy of workpieces to a great extent.Therefore,it is very important to optimize the structure of the parallel and improve the performance of the 6-DOF parallel platform.This paper mainly focuses on the optimization of the structural parameters of the6-DOF parallel platform.Firstly,the paper presented a mathematical model based on the platform.Then kinematics analysis is introduced and the inverse kinematics is also computed.In fact,the forward kinematics also played an important role in the structure optimization.So,the positive kinematics,Jacobian matrix is obtained in this paper.The relationship between singular configurations the Jacobian matrix and workspace of the parallel platform is also gained.Secondly,it presented a mathematical model of the dynamics based on the Stewart platform.And it established single body dynamics equation by New-Euler method.Furthermore,it established multi-body dynamics equations by Kane's method by comparing four methods.Then it verified the correctness of the dynamics model using ADAMS software.Finally,the structure optimization of 6-DOF parallel manipulator is introduced.And it analyzed the impact of the geometrical parameters on the performance of the manipulator and determined the range of the parameters.Then the multi-objective and multi-constraint method is proposed and choose the appropriate variable boundaries.The linear combination of the workspace and leg force is used as the optimization function and the genetic algorithm automatically optimized the determined objective function,obtained specific optimizationresults.And it compared the optimized results with the previous results.