Error Analysis And Calibration Methods Research Of Kinematic Parameters For 6-dof Industrial Robot

With the development of technology,the demand for industrial robot applications is also growing.Although it guarantees sufficient production requirements in design and production,it is difficult to meet the application requirements in terms of absolute positioning accuracy.Therefore,analyzing the factors affecting the pose error of the robot and studying the kinematic calibration method of the robot are the key issues to improve the absolute positioning accuracy robot and extend the application of robot.Firstly,analyzing the factors affecting the end pose error of the robot:(1)Starting from the robot joint level,focusing on the influence of the inaccuracy of joint transmission ratio on the end accuracy,a method based on the nominal transmission ratio to measure the actual transmission ratio is proposed,and the decoupling method is proposed for the problem that the joint has motion coupling.(2)From the perspective of robot kinematics,the joint rotation angle variable is set as a function of time t,under the condition of equal error,the influence of each D-H parameter on the end position error of the robot is analyzed by controlling the single variable method.Secondly,based on the principle of differential kinematics of the robot,a positioning error model of the robot is established.In order to solve the problem that most of the robot control systems are not open to the outside or most robots need to meet the Pieper criteria and cannot compensate for all error parameters,two solutions are proposed in this paper.(1)Starting from the error parameter identification method,a parameter dimension reduction identification method is proposed.In the process of using the error model to solve the parameter error,the error caused by uncompensated parameters is refracted to the compensated parameter,and the compensated parameter error is solved by the least squares approximation method.(2)Starting from the error compensation method,a two-step error compensation method is proposed.The first step is to directly compensate some of the parameter errors that don,t affect the robot control system algorithm.In the second step,the remaining parameter errors are converted into joint forms for indirect compensation.Finally,an experimental platform is build.The robot joint transmission ratio and coupling ratio are calibrated,contrasting the error effect after calibration of transmission ratio and coupling ratio.The laser tracker is used to measure the actual position value of the robot end,and the measurement data is substituted into the error model to solve the kinematic parameter error by the parameter identification method.The parameter error is compensated by a two-step error compensation method.In addition,The direct compensation verification experiment of 10 parameter errors obtained by parameter dimension reduction identification method is executed.The experimental results show that both methods can effectively improve the absolute positioning accuracy.