Research On Trajectory Error Compensation Of 6-DOF Industrial Robots

As an important equipment to realize industrial automation and intelligence,industrial robots has been widely used in various fields.Trajectory accuracy is an important dynamic performance of industrial robots.At present,the trajectory accuracy of industrial robots is far lower than the positioning accuracy.In this paper,a method based on robots kinematics calibration and joint space interpolation error compensation is proposed to improve the trajectory accuracy of the robot,which is verified by simulation and experiment.In this thesis,a general six degree of freedom industrial robot is selected as the research object.Based on the MD-H method,the kinematics model of the robot is built.Based on this,the terminal position error model and trajectory error model are established by using the theory of robots differential kinematics.In order to overcome the problem of slow convergence and even divergence of traditional optimization algorithms such as least square method when the data noise is large and does not conform to Gaussian distribution,a robot kinematics parameter identification method based on extended Kalman filter algorithm is proposed to realize the fast convergence of kinematics parameter identification and improve the accuracy of identification results.Through the simulation,it can be found that the Extended Kalman filter algorithm can identify the robot kinematics parameter error more accurately than the traditional least square method.In this thises,through the calibration method,the extended Kalman filter algorithm is used to identify the kinematic parameters of the robot to improve the position accuracy of the robot.After improving the position accuracy,it is found that the trajectory accuracy of the robot is also improved,because the inaccurate kinematic parameters are also an important reason for the low trajectory accuracy of the robot.The effectiveness of the method is verified by experiments.After compensation,the trajectory accuracy of the robot is improved from 2.532 mm to 1.873 mm.Because the trajectory accuracy of robot is affected by kinematic parameters,dynamic parameters,transmission error and control algorithm,and the opening degree of robot controller is limited,it is unable to compensate all kinematic parameters,so only through the identification and compensation of kinematic parameters,the improvement of trajectory accuracy of robot is limited.Firstly,Based on the principle of robot workspace error similarity,the existing workspace inverse distance weighted interpolation method is used to compensate the robot end position error.The simulation and experiment results show that the position accuracy of the end of the robot is greatly improved after compensation,which verifies the effectiveness of the workspace interpolation compensation method.However,because the inverse solution of the robot has multiple solutions,the workspace compensation method of the robot will have limitations.When the robot's pose transformation is large,the method will fail.In order to solve this problem,it is found that the robot error has better continuity in the joint space through analysis.Therefore,a joint space interpolation error compensation method is proposed.A grid error compensation database is established,and the joint angle error of each control point is predicted by using the joint space distance weight function and the known grid vertex error,and it is compensated to every joint angle in robot motion planning.The experimental results show that the trajectory accuracy is improved from 1.873 mm to 1.464 mm.