Analysis And Experimental Study On Trajectory Error Of Serial Robot

The wide application of serial robots has promoted rapid development of modern industry.At present,absolute positioning accuracy and repetitive positioning accuracy of serial robots in market are excellent,but the accuracy of trajectory is much worse.As a complex electromechanical system with multiple input and output and time-varying coupling,research on trajectory accuracy of serial robot needs further study.In this paper,a 6-DOF serial robot named LR20 is taken as the experimental object.We try to systematically analyze the error sources that cause the trajectory error,and do experimental research on the trajectory error.Firstly,this paper introduces the research status of trajectory accuracy at home and abroad,and summarizes the factors that affect accuracy of end trajectory.On the basis of establishing kinematics model of LR20 robot,forward kinematics and inverse kinematics are derived,which satisfies Piper condition and the inverse solution has real root.Many error sources which cause the error of end trajectory are classified.The static error sources that mainly caused by structural parameters error can be eliminated by structural parameter identification.The laser tracker is used to identify parameters of LR20 robot.Matlab numerical simulation are carried out to verify.The flexible error generated by robot motion and joint angle error generated by actuator,servo system and control system have a complicated influence on end trajectory.Through joint torque monitoring experiment,the effect of joint driving torque and coupling torque on structural parameters was verified.The experiment of response time and boom offset verify important influence of these dynamic error sources on accuracy of end trajectory.In order to experimentally study trajectory error of LR20 robot,a laser tracker measuring system was set up.A dynamic model of trajectory error was established.Based on analysis of dynamic and static error sources,a linear model of error source was derived.According to the robot national standard,position of the largest experimental cube and solution of error between theoretical trajectory and experimental trajectory was determined.The typical trajectory error at different speeds and loads were measured.Results show that with the increase of speed,the influence of dynamic error sources is larger and trajectory accuracy is worse,but load has no significant effect on trajectory accuracy.The trajectory accuracy of LR20 robot was evaluated by measuring end trajectory error of 12 straight lines and arcs in the experimental cube.According to the analysis of error sources and assessment results,it is necessary to focus on reducing the influence of each dynamic error source to improve the trajectory accuracy of serial robots.