Measurement of Machine Tool Two-Dimensional Error Motions Using Direction-Regulated Laser Interferometers

The volumetric accuracy of a machine tool generally changes with time. Its periodic check, performed at a user’s site in a semi-automated manner, can be a key to ensure a sufficient volumetric accuracy in the long term. A laser interferometer can only measure the linear positioning error motion of a linear axis. This paper proposes a scheme to identify all the two-dimensional (2D) error motions of two linear axes in a plane based on a set of distance measurements using only a laser interferometer. Unlike conventional tracking interferometers, the proposed scheme requires only a numerically controlled rotary table on which a laser interferometer is mounted. It regulates the laser beam direction based on the command target position in an open-loop control manner. This paper presents an algorithm to identify 2D error motions of two linear axes by performing only a single tracking test, in addition to the direct measurement of linear positioning error motions of two linear axes. The experimental comparison of the estimated error motions with their direct measurements is presented. The uncertainty analysis is also presented.