Calibration of a 6-DOF industrial robot considering the actual mechanical structures and CNC system

Calibration is an efficient approach to improve the position accuracy of robots. But in some industrial practice, only part of the DH parameters can be compensated and the reduction ratios of reduction boxes and coupling coefficient of fifth joint and sixth joint are not originally accurate in the robot CNC system. If all DH parameters are identified and only part of them is compensated, and the reduction ratio errors and coupling coefficient error are ignored, the position error may be large. In this paper, based on the robot CNC system, a calibration method for identifying the reduction ratios, coupling coefficient and part of the DH parameters is proposed. This method can improve the position accuracy as much as possible by compensating above identified parameters in CNC system. RB08 robot and Leica laser tracker are used to conduct the experiment. Results show that the maximum/mean position errors are developed from 58.292mm/36.780mm to 0.496mm/0.331mm. Therefore, this calibration method is effective and can be applied in practical industrial productions.