Kinematic calibration of a laser tracker based on nonlinear optimization of a refined geometric error model

Laser trackers are instruments used for high-precision measurements of 3D points. Geometric errors may cause measurement errors and so they must be identified and used for error compensation. Current solutions use alignment deviation based kinematic error model or D-H kinematic error model for error correction. However, these models are not sufficient to describe the exact frame alignment errors. On the other hand, it is difficult to perform nonlinear optimization with high-dimension error parameters. In this paper, we first propose a new kinematic error model which takes translation and rotation displacements and joint offsets as error parameters. And then, we propose a grouped Taylor expansion based approximation approach to reduce the complexity of calculating the analytic form of the kinematic error model. After that, we are able to perform nonlinear optimization to identify the geometric error parameters. Experiments verify that the identified geometric parameters successfully improve measurement accuracy.