The problem in Accuracy Compensation of Industrial Robot

From the published article, it seems that there is a 0.3mm accuracy limit which cannot be break no matter what model we used to compensate (for high-load 6R series industrial robots without external testing equipment). Veitschegger & Wu [1] built the kinematic model of PUMA 560 and used the differential error transform to calibrate kinematic parameters; the worst case compensated error is 0.3mm (only in one direction). Nubiola [2] also calibrated the parameters of robot and the result of positioning error is 0.696mm. Wei Z [3] proposed the concept of error similarity and adopted the method of spatial interpolation to find the size of error. Result has shown that the maximum value of positioning error is 0.386mm. This is due to the existence of backlash errors in the joints, which are caused by the reverse movement of the joints and it can be expressed by the error of moving from different directions to the same position. In this paper, the grating scales are installed at the joints of the robot, by which the size of the backlashes are measured. Through the analysis of defects in parameter calibration and accuracy compensation, the method improving robot accuracy based on joint feedback is proposed. The preliminary experimental results show that the maximum absolute position error is 0.14mm.