| The parallel mechanism is the core component of the parallel robot system.Serial and parallel mechanisms get complementary advantages in terms of stiffness,precision and motion capability.Due to the rapid development of the series mechanism,it is necessary to develop a parallel mechanism with better comprehensive performance for the development of industrial robots.The continuous development of the automotive industry requires installation accuracy and reliability between automotive parts.Parallel mechanisms with high mobility,high bearing capacity and high precision are well qualified for this task.In this paper,an 8-SPU redundant parallel mechanism is taken as the research object,and its kinematics performance,bearing performance and precision performance are analyzed.From these three aspects,the comprehensive size optimization is carried out,and the driving force is optimized.The parallel mechanism for welding between automotive components is designed.The main contents of the thesis are as follows:Firstly,kinematic analysis of the mechanism.Introducing the composition of the mechanism and calculating the degree of freedom,then explaining its redundancy.The fixed and movable coordinate systems of the mechanism are established,and the inverse length solution,the inverse velocity solution and the inverse acceleration model of the mechanism are gotten.The motion model was numerically simulated with MATLAB,and the kinematics of the mechanism was obtained from the motion variation curve.The point search method is used to obtain the workspace of the mechanism,and the influence of relevant mechanism parameters on the workspace volume is obtained.The particle swarm optimization algorithm is used to optimize the proportionate volume of the workspace.Then,static stiffness analysis of the mechanism.The principle of virtual work is used to establish the full static stiffness matrix of the mechanism.The projections of the static stiffness of the mechanism in three directions of movement and rotation are obtained respectively,and the stiffness map of the two cases with or without driving force is obtained,and the stiffness distribution laws of the mechanism is obtained.The bearing capacity of the mechanism is optimized by the condition number of the stiffness matrix and average stiffness.The results comparison before and after the stiffness optimization is analyzed and evaluated.In addition,accuracy analysis of the mechanism.The differential form of the rotation matrix is derived from the limit theory,and then the error model and error compensation model of the mechanism are established.The influence of the structural parameters and pose parameters on the error is obtained.The error compensation effect is verified by the error compensation model,and the pose error of the mechanism is optimized by the mutated particle swarm optimization algorithm.Finally,dynamic analysis of the mechanism and optimization of the prototype size.The Kane method was used to establish the dynamics model of the mechanism and the driving force optimization was performed from the energy point of view.In order to obtain better kinematics,bearing and precision comprehensive performance,the multi-objective optimization method is used to optimize the size of the mechanism,and the parallel mechanism with the best comprehensive performance is obtained.The kinetic numerical simulation and virtual prototype simulation of the mechanism were carried out by MATLAB and ADAMS respectively.The results show consistency,which explains the correctness of the dynamic model to some extent.In the end,the parallel mechanism prototype according to the structural optimization results and control platform were built.This thesis analyzes the 8-SPU parallel mechanism from the aspects of kinematics,static stiffness,precision and dynamics.It provides a theoretical reference for the analysis and design of parallel robots used in the welding of automotive components.In the field of industrial machine automation,it has kind of engineering significance. |
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