, , Octavio Icasio Hernandez, ,
Due to their accuracy, portability, and large working volume, laser trackers (LTs) are widely used for dimensional metrology in a variety of large-scale manufacturing and assembly operations. Their performance evaluation is a key concern for users, especially because factors such as environmental conditions, vibration during use, installation, transport, etc., can degrade performance over its life span. Periodic field checks are therefore important to ensure the reliability of data obtained using LTs. In this context, we discuss practical issues involved in evaluating LT performance based on the network method, i.e., the measurement of a set of fixed targets from different locations of the LT. The idea is to calibrate the distances between pairs of targets using the instrument under test and subsequently use those values as references to evaluate the performance of the instrument. We reduce the uncertainties in the calibrated distances by incorporating the laser tracker geometrical error model where the model parameters are evaluated as a part of an optimization process within the same network method. We validate the uncertainties by comparing the calibrated distances against a line-of-sight interferometer for a few selected lengths. We then demonstrate the performance evaluation through a case study using three different LTs. The clear advantage of LT performance evaluation using the network method is that it is universally applicable and does not require the use of a scale bar or a reference instrument.
Measurement Science and Technology
Laser tracker, Performance evaluation, Network method, Geometrical error model parameters