IMPROVED MANIPULATOR PERFORMANCE THROUGH LOCAL D-H CALIBRATION

This article deals with the subject of increasing the positioning accuracy of a manipulator beyond what is typically obtained via Denavit-Hartenberg (D-H) calibration. It is commonly accepted that one method for accomplishing this requires including ''extra'' terms (such as static deflection) in the D-H model. Another technique, which is experimentally verified and quantified in this article, is that of local calibration. Rather than continually introducing more and more modeling terms, we restrict the worlvolume of the manipulator. One contribution of this article is an experimental investigation of local calibration. Most data indicates that local calibration offers advantages and it quantifies that the approximate improvement on one particular PUMA 560 robot is as much as four times better than global calibration. Some data indicates that it is not always true that ''localizing'' the calibration is an improvement. The article also discusses the problem of recognizing bad calibration data. We demonstrate a technique for identifying and removing ''bad'' data. Finally, the article shows that the locality of workvolume must include a consideration of the joint motions as well. For example, it presents results when data is taken with the arm in a single configuration, and in multiple configurations. (C) 1995 John Wiley & Sons, Inc.