Development of Ultra-Precision Positioning Technique with Linear Motor

This paper introduces ultra-precision positioning technique with linear motor. In order to realize a compact positioning movement without dual structure consisting coarse and fine positionings, higher accuracy air slider studies are conducted a completely frictionless support mechanism using a linear motor and an externally pressurized air bearing. Results are as follows : (1) Temperature rise of 0.3°C, table displacement of 0.16 μm and guide warp of 0.03, μm are achieved by slider guide with adiabatic structure. (2) To reduce cogging force and normal force, coreless and slotless motor is developed. Thrust ripple has reduced to less than 2% of the rated thrust. (3) Maximum pulse velocity of 10 Mpps, acceleration of 3 m/s2, 0.2 sec for 15 mm stroke are achieved. (4) Software servo system using DSP is adopted, positioning accuracy of 10 nm are achieved without fine positioning.