A distance calibration method for kinematic parameters of serial industrial robots considering the accuracy of relative position

This paper proposes a kinematic calibration method based on the optimized distance error function to improve the accuracy of the relative positions of industrial robots. For implementation, a three-dimensional measurement system with R-test is designed to measure the robot end-effector's distance, which is the first successful use of this system for robot calibration. Then, an optimization function of the distance errors is proposed without an approximation condition to identify the controller's modifiable parameter errors. In addition, the influence of the redundant parameter on the error of relative position is analyzed, which indicates it can further improve the relative position's accuracy. Simulations prove the performance of the proposed solution by comparing it with the current distance and positioning error methods. The validation experiment shows the proposed method reduced the mean of distance error/distance and relative positioning error/relative positioning from 14.30 mu m/ mm to 4.4 mu m/mm and from 20.15 mu m/mm to 10.85 mu m/mm.