An Accurate Point-Based Rigid Registration Method for Laser Tracker Relocation

The laser tracker is widely used in a large component measurement. In practical application, due to the large size and complex shape, the laser tracker relocation is usually performed based on the fiducial points to reduce measurement distance or avoid occlusion. For a conventional relocation method, a lot of fiducial points are expected to be uniformly distributed in the entire measurement volume. However, the number and distribution of fiducial points cannot satisfy this requirement due to the light beam occlusion caused by the measured component and jig, resulting in low relocation accuracy. To solve this problem, we propose a survey adjustment-based relocation method. For this method, first, taking into account the inhomogeneity and anisotropy properties of laser tracker, the weighting matrix related to distance and direction is deduced; second, survey adjustment is performed to reduce the location error of a fiducial point, thereby reducing the relocation error. Simulations and experiments are carried out to verify relocation error, and the results show that compared with a traditional relocation method, our proposed method can achieve higher relocation accuracy only with fewer fiducial points distributed in a narrow space; thus, it can be applied in a complicated environment to solve the light beam occlusion problem.