Research On The Structure Design And Compliance Control Technology Of Grinding And Polishing Robot End Effector

The harsh working environment of grinding and polishing industry causes great harm to the operator's body and mind.With the progress of Chinese society and the upgrading of Chinese manufacturing industry,the application of industrial robots to replace workers in grinding and polishing operations is the development trend of the industry.In the operation of polishing robot,precise control of polishing contact force is needed.Due to the coupling between the contact force and the position depth in the process of machining,the precise control of the contact force of the polishing robot is a difficulty in the development of the polishing robot.In this paper,the precise control method of the contact force of the polishing robot was studied.An end-effector was designed for the polishing robot,which decoupled the contact force and position better.Meanwhile,a fuzzy PID control method based on the improved PSO algorithm was developed to achieve the precise control of the contact force of the polishing robot.The main work of this paper includes:First,in order to achieve the design objectives of flexible floating,constant force grinding and rapid response of polishing end-effector,the paper uses functional demand-mechanical structure mapping method and takes the minimum weight of polishing end-effector as the constraint condition to analyze the mechanical structure of polishing end-effector.A flexible polishing end-effector with pneumatic motor and low friction cylinder was designed.Second,mathematical modeling and analysis of the designed polishing end-effector system are carried out.By modeling the flow characteristics of electric proportional valve,low friction cylinder,gas pipe and dynamics of polishing end-effector in the system,the transfer function of polishing end-effector system was obtained.By using the Bode diagram analysis in MATLAB,it was concluded that the system has strong stability.Thirdly,the PSO algorithm is improved and the random inertia weight is used to improve its optimization ability.On the fuzzy PID control method,the improved PSO algorithm is used to optimize the initial PID control parameters,and the improved PSO algorithm fuzzy PID control method is obtained.Through MATLAB simulation analysis,the fuzzy PID control system with improved PSO algorithm has faster response speed and better robustness.Fourthly,the designed end-effector was used to build the polishing robot experimental platform,and the developed compliant control method was used to control the polishing end-effector,and the step signal response contrast experiment and constant force polishing experiment were carried out.Experiments show that the fuzzy PID control method based on the improved PSO algorithm can accurately control the output contact force of the polishing end-effector and achieve a higher step response speed.The contact force error of the end effector output can be controlled within ±1N.