Performance evaluation of laser tracker kinematic models and parameter identification

A new kinematic model for a laser tracker is presented in this paper. This model obtains the kinematic parameters by the coordinate transformation matrices between successive reference systems based on the Denavit-Hartenberg method. The ASME B89.4.19 Standard provides some ranging tests, length measurement system tests and two-face system tests that can be performed to analyze the performance of the laser tracker. However, these tests take a lot of time and require specialized equipment. Another problem is that the end user cannot apply the manufacturer's model because he cannot measure physical errors. The kinematic model developed has been compared with a geometric model based on modelling physical errors. To do this, the laser tracker kinematic model has been presented and validated using a mesh with synthetic reflector coordinates and known error parameters. The laser tracker has then been calibrated, in an easy and fast way, with experimental data using the measurements obtained by a coordinate measuring machine as nominal values. The calibration has been performed with both the kinematic model presented in this work and the geometric model based on physical errors. A comparison of both calibrations has been made, analyzing the performance of both models. Finally, a sensitivity analysis of the length measurement system tests is presented to recommend the more suitable positions to perform the calibration procedure.