A comparative study of MDH and zero reference model for geometric parameters calibration to enhance robot accuracy

Abstract

It is an effective method to improve the absolute positioning accuracy (APA) of robot’s end-effector by geometric parameters calibration. In this paper, zero reference model (ZRM) and modified Denavit-Hartenberg (MDH) methods are adopted to establish the geometric parameters model of series robot, respectively. Least squares method (LSM) is used to minimize error magnitude in a function modeled over analytical Jacobian of the robot. By carrying out the practical calibration for Staubli Tx60 industrial robot with a Leica 960 laser tracker, the experimental results verify that in robot workspaces the mean absolute positioning errors is reduced from 0.5864 mm before calibration to 0.0737 mm based on ZRM and to 0.1319 mm based on MDH after calibration, respectively. The comparative study shows that ZRM and MDH methods can enhance robot APA and the improvement by ZRM is superior to that by MDH.