Real-time correction of movement errors of a machine axis by multiple null-balancing using Twyman-Green interferometry

Abstract

This paper presents a real-time correction method for the geometric movement errors of a translatory precision machine axis. The method utilizes the optical principle of Twyman-Green interferometry with two plane mirrors to detect one translatory and two rotational errors of the machine axis simultaneously. The errors measured are instantly suppressed by activating piezoelectric actuators using a null-balancing feedback control algorithm of multi-input and multi-output while the machine axis is moving. Experimental results demonstrate that movement errors can be controlled less than 10 nm for vertical straightness, 0.1 arcs for pitch, and 0.06 arcs for roll for a total distance of 50 mm by adopting the method proposed.