Precision positioning of a surface motor-driven multi-axis stage using a surface encoder

This paper describes a surface motor-driven XYθz stage equipped with a newly developed surface encoder as the position-detection sensor. The stage consists of a moving element, a stage base, a surface motor and a surface encoder. The surface motor is composed of four linear motors (two pairs in XY-axes). Translational motions in XY and the rotational motion θ_z around Z-axis of the moving element can be generated by the surface motor. The surface encoder consists of a two-dimensional angle sensor and a two-dimensional angle grid. The angle sensor is fixed on the stage base and the angle grid is mounted on the back of the moving element. The multi-axis position of the moving element can be obtained from the angle sensor output. The surface encoder is placed inside the stage and the stage system is very compact in size. The range of travel of the stage is designed to be 40mm x 40mm x 24deg. Experimental results in XY axes are reported.