Multiple location constraints based industrial robot kinematic parameter calibration and accuracy assessment

Kinematic calibration of industrial robots is an effective method of improving robot accuracy, and thus robot performance, especially when working with offline programming. The state-of-art industrial applications are lacking an easy-to-operate, reliable, and economic solution, hence forbidding frequent on-site calibration. This study presents a robot kinematic calibration method to improve the accuracy of six-axis industrial robots, using multiple location constraints. The robot parameters are calibrated by controlling a robot to reach the same location in different poses. Two standard devices and a non-contact equipment, non-bar device, are used for measurement. The proposed calibration process applies three identification methods and two compensation methods that can be mixed and matched, allowing flexible combinations of solutions to fit various industrial conditions. The proposed measurement/calibration system is economic, easy-to-operate, reliable, and suitable for express user-site industrial robot kinematic calibration, avoiding extensive production interruption. Actual experiments are carried out to verify the effects of joint zero calibration. These experiments demonstrate the proposed method's ability to improve the accuracy of robots, and thus improve the robot work quality using offline programming.