Control of a high precision positioning stage

Control of a two dimensional high precision positioning stage is presented in this work 1. This stage is composed by two kinds of stages, a two degrees-of-freedom (DOF) (X and Y) linear cross roller guideway supported stage and a 4-DOF (Z, θ_x, θ_y and θ_z) piezo-stage. Two linear shaft voice coil motor are used to actuate the roller guided X-Y stage and five piezoelectric actuators are used in the piezo-stage. The positioning range of the X-Y stage is 25 mm × 25 mm and the piezo-stage is designed to compensate the vertical position, row, pitch and yow errors throughout the whole working range. A 6-DOF optical measurement system that consists of three laser interferometers and two quadrant photo-diodes is used to measure the attitude of the stage. The resolution of this measurement system is about 9.8 nm and 0.1 arc second. Integral sliding-mode controllers are used to control the linear motor driven stage while PID controllers are used to control the piezo-stage. Experimental results show that the positioning uncertainty is about ±20 nm.