IMPROVED MANIPULATOR PERFORMANCE THROUGH LOCAL D-H CALIBRATION

This article deals with the subject of increasing the positioning accu racy of a manipulator beyond what is typically obtained via Denavit-Ha rtenberg (D-H) calibration. It is commonly accepted that one method fo r accomplishing this requires including ''extra'' terms (such as stati c deflection) in the D-H model. Another technique, which is experiment ally verified and quantified in this article, is that of local calibra tion. Rather than continually introducing more and more modeling terms , we restrict the worlvolume of the manipulator. One contribution of t his article is an experimental investigation of local calibration. Mos t data indicates that local calibration offers advantages and it quant ifies that the approximate improvement on one particular PUMA 560 robo t is as much as four times better than global calibration. Some data i ndicates that it is not always true that ''localizing'' the calibratio n is an improvement. The article also discusses the problem of recogni zing bad calibration data. We demonstrate a technique for identifying and removing ''bad'' data. Finally, the article shows that the localit y of workvolume must include a consideration of the joint motions as w ell. For example, it presents results when data is taken with the arm in a single configuration, and in multiple configurations. (C) 1995 Jo hn Wiley & Sons, Inc.