Study on robot calibration using a laser tracking system (2nd report) - Discussion on how to select parameters, number of measurement and pose of measurement in multiple positioning method

Abstract

A 6-DOF articulated robot (PUMA 560) is calibrated by using a laser tracking system according to the multiple positioning method and the effectiveness of this system is certified. A method which calibrates only angle parameters is newly proposed, since there is a possibility that true values of length parameters are directly measured by some other methods. The relationship between sensibility index and the number of measurement are simulated and it is inferred that 10 random measurements with fixed orientation is enough in case of calibrating only angle parameters and 20 random measurements with random orientation is enough in case of calibrating both angle and length parameters. The combination method which obtains length parameters by the joint axis estimating method and calibrates angle parameters by the multiple positioning method is experimentally developed. The accuracy of the combination method and that of the normal multiple positioning method are experimentally investigated. From the results, the effectiveness of the strategy of how to select parameters, number and pose (position and orientation) of measurement, which is mentioned above, is experimentally confirmed. The accuracy of 0.12mm is achieved in wide area and this value is better than already reported ones about PUMA 560.