Electrostatic linear servo motor with built-in position sensor for vacuum environment

A high-power electrostatic linear servo motor stage for vacuum environment has been developed. The stage is equipped with integrated built-in position sensor that uses the motor's electrode for position sensing. This stage is characterized by compact structure and low magnetic field emission. It can work within sufficiently small space in a vacuum chamber without disturbing surrounding electro-magnetic field. Therefore this motor stage could be highly compatible with many vacuum applications that utilize electron beam. In this paper, basic structure of the motor is described. The motor is sized 145 mm in length, 125 mm in width, and 40 mm in height. The stage is equipped with two thin plastic films, which contain three-phase electrodes aligned with an interval of 200 /spl mu/m. Those two films are attached to slider and stator, respectively, to generate electrostatic thrust force. Linear cross-roller guide supports the slider. The stroke is 40 mm. The estimated thrust force in 10/sup -3/ Pa is 1.2 N with an applied voltage of 1.6 kV/sub 0-p/. We have developed built-in position sensor for positioning servo control. Detail of built-in position sensor and results of positioning control are reported.