Machining, Measurement, and Control Laboratory

Estimation of Three-Dimensional Volumetric Errors of Numerically Controlled Machine Tools by a Tracking Interferometer
Soichi Ibaraki, Kunitaka Takeuchi, Tomoaki Yano, Toshiyuki Takatsuji, Sonko Osawa and Osamu Sato

This paper presents the estimation of three-dimensional volumetric errors of a machining center by using a tracking interferometer. A tracking interferometer is a laser interferometer with the mechanism to steer the laser direction to follow a target retroreflector. Based on the triangulation principle, the three-dimensional position of the target can be estimated from measured laser displacements. Its capability to measure three-dimensional positioning errors for arbitrary trajectories is important for the indirect measurement of the machine’s kinematic model. This paper presents experimental investigation of the estimation accuracy of the multilateration-based measurement by a tracking interferometer. A tracking interferometer developed by a part of the authors is used in experiments. In the present experiment, the measured volume of target positions was 100 mm X 100 mm X 100 mm. The estimation accuracy of targets within this volume was not sufficiently high compared to the positioning error of the measured machine tool. The results of the experiment and simulation show that the estimation uncertainty is dependent on tracking interferometer locations relative to target locations. Error sensitivity analysis shows that wider distribution of tracker positions in XY improves the estimation accuracy.
Keywords: Tracking interferometer, laser tracker, volumetric errors, multilateration, machine tools, estimation accuracy.