Research On High-precision Trajectory Tracking And Motion Control Methods For Robots

With the rapid development of automation technology and computer science,industrial robots are increasingly used in modern manufacturing systems.The trajectory planning and trajectory tracking control are the key links to ensure the accurate operation of the robot.However,in practical engineering applications,the desired trajectory of robot is often complicated and the performance mutation at the inflection point of the trajectory has impact on the system,which may then affect the smoothness and reliability of robot movement.In addition,in the robot motion control system based on dynamics model,the sliding mode variable structure control method has strong robust performance,but also accompanied by chattering phenomenon of the system and the uncoordinated movements of robot joint,which has a certain degree of influence on the motion control performance and accuracy of the end-effector.In this paper,a three degrees of freedom robot is used as the main research object,and the trajectory planning and high-precision trajectory tracking control methods are studied.The contents of the paper are as follows:Firstly,the kinematics and dynamics model of the robot are established,and the accuracy of the mathematical model is validated.Second,a minimum snap trajectory is used to transition between adjacent curves of continuous trajectories in order to avoid impact problems caused by performance mutations at inflection points of desired trajectories.The position,velocity and acceleration are constrained by equality at the point of trajectory transition.This method can provide a smoothness and reliable trajectory for the robot motion control system.In addition,aiming at the influence of uncertain factors such as mutation of trajectory performance and external random interference on robot control performance,an improved non-singular terminal integral sliding mode surface is designed based on the dynamics model of the robot,and a second-order integral sliding mode trajectory tracking controller is designed by using the super-twisting algorithm.Simulation results show that the controller has better robustness to external uncertainties,and can effectively improve the steady-state error of each joint of the robot to within 10^-3rad,and effectively suppress the chattering phenomenon of the system.Then,the non-singular terminal integral sliding mode control law is designed by backstepping method for the influence such as the model error of the controller based on dynamics model on the contour tracking accuracy of robot.Then,the time delay estimation method is used to estimate the unknown dynamics and disturbances through the system delay information,and a model-free sliding mode trajectory tracking controller is obtained.At the same time,the contour error of the robot end-effector is compensated to each joint controller by cross coupling control,and the coordinated motion of each joint is studied while the tracking accuracy of each joint is studied.Simulation results show that the proposed control method can accurately track the planned trajectory of the robot end-effector under the influence of model errors,and the steady-state error of the trajectory of robot end-effector in X,Y and Z axes is within 10^-4m,which verifies the effectiveness of the proposed method.Finally,the robot experiment platform is built.Engineering experiments and tests of trajectory planning and trajectory tracking control algorithm are carried out on the experimental platform,which further verifies the feasibility of the proposed method.