Performance evaluation of laser trackers using the network method. (1st December 2020)

• Record Type: Journal Article
• Authors: Wang, Ling; Muralikrishnan, Bala; Icasio Hernandez, Octavio; Shakarji, Craig; Sawyer, Daniel
• Is Part Of: Measurement. Volume 165(2020)
• Publication Date: 2020-12-01
• Subjects: Laser tracker -- Performance evaluation -- Network method -- Geometrical error model parameters; Weights and measures -- Periodicals; Measurement -- Periodicals; Measurement; Weights and measures; Periodicals; 530.8
• DOI: 10.1016/j.measurement.2020.108165
• Languages: English
• ISSNs: 0263-2241

Abstract

Highlights: Method to evaluate performance of a laser tracker (LT) without need for scale bar. Method utilizes stationary targets measured from multiple LT positions. Length uncertainty between stationary targets is reduced by fitting LT error model. These lengths are then used as reference for laser tracker performance evaluation. Method validated using line-of-sight interferometry. Abstract: Laser trackers (LTs) are widely used for large-scale dimensional metrology. Periodic LT performance evaluation is a key aspect in ensuring measurement reliability. The existing documentary standards for LT performance evaluation require scale bars and special artifacts that are often unavailable for many LT users. A network-based method is considered in this paper as a simple and effective approach to evaluate LT performance without the need for expensive artifacts or reference instruments. In this method, a set of fixed targets are measured from different locations of the LT. The reference values for the lengths between pairs of targets are determined by incorporating the geometrical error model of the LT (i.e., the LT data from each location are corrected for systematic geometric misalignments, quantities that are also obtained from the same data), thus the LT under test is itself used to calibrate the lengths in the network. Subsequently, these length values are used as references to evaluate the LT performance. We validate this method of establishing reference lengths by comparing the values for select lengths in the network against more traditional line-of-sight interferometry. We show that the uncertainties in the reference lengths obtained in this manner are sufficiently small in comparison to the maximum permissible error (MPE) specifications so that they can be used for performance evaluation. A case study using three LTs is presented in this paper. The results obtained from that case study is also verified by a simulation based on the ASME B89.4.19 standard, showing the feasibility of the proposed network-based LT performance evaluation method.