Research On Compliance Control Method For Robotic Surface Grinding

Compliant control refers to the process that the robot makes corresponding adjustments based on the feedback signal of the force sensor to precisely control the change of contact force.Generally speaking,industrial robots meet the requirements of traditional position control,while industrial robots based on position control were difficult to meet the requirements of contact force control for grinding of complex surfaces.Therefore,the research on the control method of robot polishing compliance has important application significance.In this thesis,the robot surface grinding compliance control method was taken as the object.In view of the current situation and deficiencies of the surface grinding operation,research on the compliance control technical scheme,surface grinding fitting method,mathematical modeling of the compliant device,and grinding contact force control were studied,to provide a theoretical basis for satisfying the robot grinding operation.The work and main research contents of this article are as follows.(1)Research on the technical scheme of robot polishing operation control.In this thesis,the traditional position control is difficult to meet the shortcomings of the grinding contact force control.The characteristics of the two typical schemes of force/position hybrid control and impedance control are analyzed in detail,and the force-position separation grinding compliance control scheme is proposed.On the basis of the six-degree-of-freedom robot,the expansion axis was used to form a seven-axis grinding operation control system,while maintaining the position control mode of the six-degree-of-freedom robot unchanged.The control parameter is the operating current of the proportional valve.At the same time,based on the technical scheme of compliance control,the principle and characteristics of pneumatic drive grinding contact force control were analyzed to lay the foundation for the design of the compliance device later.(2)Research on the fitting method of robot surface grinding.Aiming at the path problem of robot surface grinding,this thesis introduces the fitting methods and characteristics of several typical surfaces in detail,and proposes a fifth degree polynomial function interpolation algorithm.This method can better realize the fitting of the curved surface grinding path of the robot.The grinding path of the robot is smooth and smooth,which meets the stability and continuity of the grinding process.(3)Design of curved surface smoothing device and establishment of system mathematical model.In order to meet the requirements of normal contact force control during grinding and the accuracy of compliance control,this thesis designs a reasonable compliance grinding device.Based on the modeling and analysis of the main components of the pneumatic compliance device,the transfer function is obtained,which is approximated as the mathematical model of the entire control system.Use phase margin and amplitude margin to determine the stability of the system,and lay the foundation for the following to ensure constant control of contact force.(4)Research on constant control algorithm of contact force for surface grinding.In this paper,three control algorithms,such as traditional PID control,fuzzy PID control,and sliding mode control,are proposed to address the shortcomings of precise control of nonlinear systems.Detailed analysis of the three control principles and characteristics,as well as the constant control scheme of the grinding contact force.The MATLAB software was used to carry out simulation analysis research on the three control algorithms,and comparatively analyze the control effect of the grinding contact force under different control algorithms.This article makes an in-depth study on the technical solutions of the compliant control of sanding for the key problems in the sanding operation.The innovation of this article is to propose a flexible control scheme of force-position separation based on the insufficient contact force of industrial robot to control the grinding,keep the robot position control mode unchanged,and use the seventh axis of the robot to control the grinding contact force to meet the surface grinding Contact force control accuracy requirements.