Development of Six-Axis Precise Positioning System Driven by Surface Motor.

Abstract

A newly developed six-axis precise positioning system incorporating a surface motor (SFM) is presented and its operational principle, mechanical and control system design, and some experimental results are described. The positioning system is levitated on a base plate by three air-bearing pads ; being driven by simultaneous operation of three linear motors in the x-, y-, and θz-directions and piezo elements in the z-, θx-, and θy-directions. A new design concept is discussed that incorporates (i) a mechanical design relative to the drive and sensing point locations which enables stabilization of the x-, y-, and θz-directional planar motions and (ii) a six-axis position control method using a force disturbance observer for achieving high positioning resolution as well as quick response capabilities. Evaluation of experimental results indicates that the system is capable of achieving six-axis precise motion with 10-20 nm resolution in the x- and y-directions and that the proposed control strategy enables better positioning characteristics than the conventional PID-based servo control method.