Yasushi Koyanagawa

A surface motor-driven precise positioning system

Abstract A novel precise positioning system incorporating a surface motor (SFM) drive, called the SFM positioning system, has been developed and its performance experimentally evaluated. The positioning stage is guided along a base plate by three air-bearing pads and driven in 3 of freedom ( x , y , θ z ) by coupled forces produced by three brushless-type linear DC motors. The positioning and guidance of the stages planar motion is accomplished via the simultaneous operation of three identical force-controlled servo systems with a laser-interferometer position feedback loop. The systems advantageous design features and its fundamental configuration and operating principles are described. In addition, we discuss the design of the servo control system, being based on proportional-integral-derivative and decoupling compensations and providing dynamic accuracy as well as rapid response capabilities, including the control system configuration, which incorporates a high-performance parallel processor. Evaluations of experimental positioning tests indicate that a resultant positioning resolution of 10–20 nm, maximum speed of 150 mm/s, and frequency response bandwidth of 105 Hz are successfully achieved.

Study on a Surface-Motor Driven Precise Positioning System

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 stages 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.

Precise Positioning Mechanism using Surface Motor.

In this paper, a new precise positioning mechanism using a surface motor is proposed, and the construction and analytical and experimental results for the characteristics of a newly developed stage mechanism are also described. The surface motor consists of 3 driving elements using a brushless-type linear DC motor, and a stage, supported on a base plate by hydrostatic gas bearings, is directly driven in 3 degrees of freedom (X Y θz). The motion of the stage is measured by a laser interferometer system with 5 nm resolution, and each axis is controlled by a PID controller. Thrust force characteristics are analyzed by means of the permeance concept, and the method is validated by some experimental results. Also, calculated closed-loop positioning characteristics of the system have good coincidence with experimental ones. Consequently, a translational positioning resolution of 0.01μm and rotational accuracy less than ±0.07 μrad are achieved in the travel area of 10 mm square.