MODELING GIMBAL AXIS MISALIGNMENTS AND MIRROR CENTER OFFSET IN A SINGLE-BEAM LASER TRACKING MEASUREMENT SYSTEM

The calibration of robots and machine tools normally requires external pose measuring devices to provide precision calibration measurement d ata. Among the various coordinate measuring techniques, laser tracking systems based on interferometry offer the potential for continuously producing noninvasive and highly accurate measurements over a large wo rk volume. This article addresses the error modeling issue for laser t racking coordinate measuring systems, which is crucial in the accuracy enhancement of such systems. Relative distance measurements provided by laser interferometers have an extremely high resolution. However; a ccuracy errors of a coordinate measuring machine based on laser tracki ng are dominated by geometric en-ors in the tracking mirror system. Ma jor geometric en or sources include gimbal axis misalignments and mirr or center offset. In this article a kinematic model for the single-bea m tracker is developed in which a necessary and sufficient number of k inematic parameters are used to represent these two types of error sou rces for arbitrary target positions. This model, together with its err or model, which is also presented in this article, can be used for des ign, calibration, and control of single-beam laser tracking measuremen t systems.