Dimensional Optimization And Trajectory Planning Of High Stiffness And Heavy Load Friction Stir Welding Robot

The welding quality of high strength aluminum alloy panel with complex space curved surface is the key to ensure the service performance of large aerospace and aviation structures.Friction stir welding(FSW)is an ideal technology to realize the welding of high strength aluminum alloy panel with complex curved surface.In recent years,with the development of artificial intelligence technology,intelligent manufacturing has become the trend of the times.Robot technology is an effective tool to improve the welding efficiency and intelligence of aluminum alloy panel.However,the serial robot has the disadvantage of poor end stiffness,which will limit its performance in FSW task.Therefore,in order to improve the end stiffness of the serial robot,this paper conducted the research on kinematics modeling,index construction,dimensional optimization,trajectory planning and force position hybrid control.Firstly,the kinematics model of zk-500 robot and positioner system is established,and the coordinate system,forward and inverse kinematics model,velocity kinematics model and coordinated kinematics model of robot positioner system are established.Secondly,this thesis analyzes the stress form of FSW and deduces the direction stiffness index.Based on sigmoid function,a new construction method of robot hybrid index is proposed,which is called soft constraint index.Compared with the existing weighted average hybrid index,the soft constraint index has a clear physical meaning,and the hyper parameters can be determined systematically.Using this index,the optimal design of the arm length of the robot and the joint trajectory planning of the robot-positioner redundant degree of freedom system are completed.The simulation results of joint trajectory planning show that the joint trajectory planned by soft constraint stiffness index can not only ensure the end stiffness close to the optimum,but also greatly improve the trajectory smoothness.Finally,the dynamic model of the robot is established,and its correctness is verified by ADAMS simulation.In the framework of force position hybrid control algorithm,the position control loop of robot is realized by combining dynamic model with PID control;the contact force control loop is designed by using force Jacobian matrix and PID control;the position control and contact force control in two orthogonal directions are realized by selecting matrix.The simulation experiment is carried out by using ADAMS and MATLAB / Simulink co simulation platform.The experimental results show the effectiveness of the robot force position hybrid control system.