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 in this paper. The positioning system is levitated on a base plate by three air-bearing pads being driven by simultaneous operation of three linear motors in x-, y-, and θ{sub}z-directions and by piezo elements in z-. θx', and θ{sub}y-directions. A new design concept that incorporates the six-axis position control method using a force disturbance observer for achieving high positioning resolution as well as quick response capabilities is discussed. The evaluation of experimental results indicates that the system is capable of achieving six-axis precision and that the proposed control strategy enables better positioning characteristics than the conventional PID-based servo control method. These mechanical and control system design concepts have been applied to a newly developed linear-motor driven precision XY stage system "Nanoplane". The Nanoplane system has several operating features such as high positioning resolution of 8.6 to 20 nm, following motion stability better than 40 nm, and yaw-axis motion accuracy better than ±1.6 arcsec over 800mm travel stroke.
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