Laser-Based Sensing, Measurement, and Misalignment Control of Coupled Linear and Angular Motion for Ultrahigh Precision Movement

This paper presents a novel methodology for position and orientation (pose) measurement of stages used for micro/nano positioning which produce coupled motions with three planar degrees of freedom (DOF). In the proposed methodology, counter-rotation of the entire mechanism prevents the misalignment of the measurement beams within a laser-interferometry-based sensing and measurement technique. To detect such a misalignment, a sensing strategy constructed around a position sensitive diode has been developed. A feedforward-feedback compound controller has been established to provide the necessary counter-rotation input to reduce the misalignment error. Experimental validation has been conducted through the measurement of the workspace of a three-DOF planar micro/nano positioning stage. Experimental results demonstrate the capability of the technique to provide combined linear/angular measurement.