Analyses Of Joint Flexibility And Layout Optimization Of Weld Seam Of A Heavy Duty FSW Robot

Taking Jiangsu Province Transformation Project of Scientific and Technological Achievements "Development and Industrialization of Core Technology of High Speed and Heavy Duty 500kg Industrial Robots" as the background,technical problems such as the flexibility,deviation compensation and workpiece layout optimization in the robot friction stir welding system are systematically studied in this thesis.Considering the design and development of the 500kg robot in this project is still in the stage of model design,the 150kg robot is used as an example to do the research.In view of the fact that kinematics is the precondition and foundation of robot motion control,the 150kg heavy duty robot's kinematics model is established based on the D-H model and the analytic solutions of inverse kinematics are derived.Meanwhile Analyses are conducted on judgment of the robot's singular configuration and principles of inverse kinematics' choice.In order to confirm the correctness of kinematics,the virtual prototyping model of the robot is constructed based on Adams.Then the spline curves of six joints'displacements are set as driving curves of virtual prototyping model's six joints and the motion simulation is completed.Simulation results show that simulated trajectories of robot's terminal coincide with planning paths,thus proving the validity of the analytic solutions of inverse kinematics.The existence of joint flexibility makes heavy duty robots difficult to achieve high absolute position accuracy and the path deviation of the robot caused by joint flexibility has a serious impact on welding quality.Thus,in this thesis,the joint flexibility is quantified by the joint stiffness and the joint stiffness of the robot is analyzed and estimated.A stiffness model is established and an experiment is carried out to identify the joint stiffness of the robot.Then,an off-line compensation method of path deviations of the robot end-effector is introduced and implemented to solve the problem about joint flexibility.The deviation compensation experiments are carried out on multiple trajectories of the robot in two kinds of different working conditions,and the experiment results show that the average efficiency of deviation compensation is 71.49%in which the robot carries the load and 88.84%in which the robot subjects to forging force.Based on the analysis of the load experimental data,the second deviation compensation method is proposed,which increases the average efficiency of deviation compensation to 97.00%.So the experiment results show the validity and feasibility of the deviation compensation method and path deviation is greatly reduced to improve welding quality.Reasonable layout of welding workpiece in the working space of the robot can improve the operating performance of robotic friction stir welding.Through a deep analysis of influence factors of robotic friction stir welding,the mathematical optimization model for the layout problem of welding workpiece is established with the method of incorporating multiple criteria,which takes into account multiple criteria and constraints,such as the optimization indexes of deviation of the robot end-effector,joint torque,flexibility of robot motion,the optimization constraints of non-singular posture,motion stability and scopes of joints,joint torque,working space.Then the mathematical optimization model is solved by genetic algorithm.At last,the efficiency of this method is proved by the layout optimization simulation experiments.Finally,on the basis of the robot off-line programming and simulation platform"ROBOLP" developed by our laboratory,the development and integration of robotic friction stir welding system software are realized by using Solidworks as the development platform and VC++/MFC as the development language.The design principle and structure of the software,interface implementation and integration method are discussed in detail in this thesis.Meanwhile the function design and test evaluation analysis of the software's function modules are given in this thesis,including welding seam information extraction module,process parameters setting module,workpiece's layout optimization module,deviation compensation and robot's motion simulation module and data real-time monitoring module.