A newly developed precise positioning system incorporating a surface-motor (SFM) drive unit is presented and its advantageous features, operation principles, electromagnetic drive force design, and some experimental results are described. The stage of our “SFM positioning system” is levitated on a base plate by three air bearing pads; being driven by three brushless-type linear DC motors in three degrees of freedom. The guidance and positioning of the stage’s planar motion are achieved via the simultaneous operation of three identical proportional-integral-derivative (PID) servo-control systems, each having a laser-interferometer position feedback loop. The electromagnetically produced drive forces are analyzed by employing magnetic permeability theory, with good correspondence being obtained between calculated and experimental results. Additionally discussed is the closed-loop dynamic behavior, including the motion caused by three axis-interference. Evaluations of experimental tests indicate that a positioning resolution of 10–20 nm and yaw angle accuracy less than ±0.08 µrad are successfully achieved for an x-y travel range of 10 mm.

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