XIX IMEKO World Congress Fundamental and Applied Metrology September 611, 2009, Lisbon, Portugal PERFORMANCE EVALUATION OF PROBING SYSTEMS IN DATA CAPTURE FOR KINEMATIC PARAMETER IDENTIFICATION AND VERIFICATION OF ARTICULATED ARM COORDINATE MEASURING MACHINES Jorge Santolaria 1 , Juan José Aguilar 1 , Agustín Brau 1 , Francisco Javier Brosed 1 1 Design and Manufacturing Engineering Department, C.P.S. University of Zaragoza, Zaragoza, Spain, jsmazo@unizar.es Abstract  This paper presents a comparison of different techniques to capture nominal data for its use in later verification and kinematic parameter identification procedures for articulated arm coordinate measuring machines (AACMM). By using four different probing systems (passive spherical probe, active spherical probe, self-centering passive probe and self- centering active probe) the accuracy and repeatability of captured points has been evaluated. The nominal points are materialized by a ball-bar gauge distributed in several positions of the measurement volume. By comparing these systems it is possible to characterize the influence of the force over the final results for each of the gauge and probing system configurations. The results with each of the systems studied show the advantages and original accuracy obtained by active probes, and thus their suitability in verification (active probes) and kinematic parameter identification (self- centering active probes) procedures. Keywords: Articulated arm coordinate measuring machines; Performance evaluation; Probing system comparison. 1. INTRODUCTION One of the key aspects in the procedure of identifying the parameters of a kinematic model of an AACMM or robot arm [1-7] is the process of capturing data. This data will be compared to nominal distance and position data obtained from a gauge or some other measurement instrument which functions as a gauge, thus allowing us to define an error objective function to be minimized by means of a mathematical optimization procedure [8]. Once the parameters have been identified, the best attainable accuracy in this type of equipment will greatly depend on the type and number of positions captured by the AACMM or robot arm [9, 10] and, ultimately, on the extent to which the number of influences on the capture of points can be minimized. Because the AACMM is a manually- operated instrument, the results obtained in its verification tests are subject to influences from the operator, mainly materialized through different probing forces during the data capture process. These external probing forces cause deformations to the gauge or to the probe [11, 12] which can result in the loss of accuracy in the verification procedure or during the process of capturing data for parameter identification. In this work we present a comparison of different data capture techniques and an analysis of the influence of the probing force in each of them, showing the most adequate procedure to capture data for the verification and parameter identification procedures. 2. METHODOLOGY In order to capture the data a ball bar gauge was used to materialize nominal points and distances in the workspace of an AACMM. Fig. 1. Evaluated AACMM probing systems. The ASME B89.4.22-2004 standard, the only existing standard in the field of AACMM verification, establishes verification procedures based solely in the capture of points through passive and active spherical tip probes. In this case, the influence of the probing force over the behavior of the articulated arm has been analyzed, obtaining the 1846 ISBN 978-963-88410-0-1 © 2009 IMEKO