Design And Analysis Of Parallel Mechanism For Machining Slender Structural Parts

In recent years,the development of China’s aerospace industry has put forward higher requirements for the performance of aerospace equipment.In order to meet the overall performance of aerospace equipment,more and more slender structural parts are used in aerospace equipment.This research in view of the problems of the traditional way in the process of slender structural parts processing,carries out design and analysis of parallel mechanism for the slender structural parts processing,this research proposes a 2-UPS&(2-RPR)R new large rotation parallel mechanism,and carries out its kinematic analysis,kinematic performance analysis,dynamic analysis,size optimization,simulation analysis and trajectory planning.This research has laid a foundation for the parallel mechanism to be used in the manufacture of slender structural parts,which has important theoretical significance and application value.The research and analysis of this paper are as follows:(1)Design of the overall scheme of machining equipment for slender structural parts.In view of the structural characteristics of slender structural parts and the requirements for processing equipment,the long guide rail,4-DOF parallel mechanism and rotating posture adjustment platen are determined as the final processing scheme through the comparative analysis and further optimization of a variety of overall schemes.(2)Configuration design of the parallel mechanism.Combined with the design requirements of degree of freedom,large rotation,high dexterity and high stiffness,a 2-UPS&(2-RPR)R new large rotation parallel mechanism is designed.The four degrees of freedom of the mechanism are calculated and verified by using the spiral theory and the modified G-K formula.By analyzing the singular configuration of the mechanism,the relevant structural parameters of the mechanism are optimized,and four prismatic pairs are selected as the drive pairs of the mechanism.(3)Kinematic analysis,kinematic performance analysis and dynamics analysis of 2-UPS&(2-RPR)R parallel mechanism.Based on the closed-loop vector equation,the inverse kinematics model and the forward kinematics model of the mechanism is obtained,and the jacobian matrix of the mechanism is obtained.Based on the monte carlo search method,the conditional number of jacobian matrix,the working space,singularity,dexterity and static stiffness of the mechanism are analyzed and the corresponding graphs are drawn.The dynamic model of the mechanism is established based on the principle of virtual work.(4)Dimension synthesis of 2-UPS&(2-RPR)R parallel mechanism.The multiobjective optimization of the mechanism is carried out by using the optimization method of Non-Dominated Sorting Genetic Algorithm-II.Taking the working space and dexterity as the objective function,the optimized mechanism size is obtained.The comparison of the working space and dexterity performance before and after the size optimization of the mechanism is carried out,and the expansion of the working space and the improvement of dexterity performance by the multi-objective optimization are verified.(5)Simulation analysis and trajectory planning of 2-UPS&(2-RPR)R parallel mechanism.Virtual prototype of the mechanism is established based on ADAMS software,and the verification of mechanism’s degree of freedom,kinematics simulation analysis and dynamic simulation analysis are carried out.The theoretical calculation of the drive’s parameters of the mechanism has carried on by MATLAB software.Through the comparison,the results verifies that the mechanism has four freedom degree,the correctness of the kinematics analysis,the dynamic analysis and the virtual prototype model.According to the actual machining requirements,the trajectory planning of Tshaped motion,the motion along the rotation direction and circular motion in the plane is carried out,and a complete trajectory planning for machining an arc surface on slender structural part is realized by combined with three kinds of motion trajectory.According to the trajectory,ADAMS software and MATLAB software are respectively used for simulation analysis and theoretical calculation of the drive’s parameters of the mechanism,which verifies that the performance of the mechanism meets the requirements and the feasibility of trajectory planning.