Precise Positioning Mechanism using Surface Motor

In this paper, a new precise positioning mechanism using a surface motor is proposed, and the construction and analytical and experimental results for the characteristics of a newly developed stage mechanism are also described. The surface motor consists of 3 driving elements using a brushless-type linear DC motor, and a stage, supported on a base plate by hydrostatic gas bearings, is directly driven in 3 degrees of freedom (X Y θz). The motion of the stage is measured by a laser interferometer system with 5 nm resolution, and each axis is controlled by a PID controller. Thrust force characteristics are analyzed by means of the permeance concept, and the method is validated by some experimental results. Also, calculated closed-loop positioning characteristics of the system have good coincidence with experimental ones. Consequently, a translational positioning resolution of 0.01μm and rotational accuracy less than ±0.07 μrad are achieved in the travel area of 10 mm square.