Parameter Identification and Calibration of D-H Model for 6-DOF Serial Robots

This paper intends to improve the absolute accuracy of the end-effector of serial robot. Firstly, the axis measurement method is used to identify the D-H (Denavit-Hartenberg) model parameters, and the D-H model parameters are transformed into the complete, minimal and model-continuous kinematic (CMMK) model parameters. Then, the parameters are optimized by the nonlinear method to solve the non-convergence problem of nonlinear optimization, which is caused by the singularity and redundancy of the D-H parameter model. Finally, the optimized CMMKmodel parameters are transformed into the industrial D-H model parameters, according to which the theoretical D-H parameter model is modified to accomplish high-accuracy calibration and position control. In experiments on MOTOMAN-MH80 robot, the robotic link parameters are effectively identified with the proposed method, and the positioning error decreases from 2 mm to 0.7 mm after calibration, ithe positioning accuracy is improved by about 70%. The proposed method can be used in more cases comparing with the kinematic loop method, because it obtains initial values of robot model parameters by axis measurement method and avoids the theoretical modeling process. Plus, problems of singularity, discontinuity and non-convergence of D-H model are solved effectively through the CMMK model based calibration.