I Introduction
Recently, precision position control become more and more important in LCD equipment, chip mount machines, semiconductor production machines, precision milling machines, high resolution CNC machines, precision assembly robots, high speed hard disk drivers and so on. Also one of a merging technology is a nanotechnology. This part almost works in nano-fabrication but now spreads to bio-engineering, optical equipment, and so on. It is also very important for direct drive systems. A PMSM has replaced many DC motors since the industry applications require more powerful actuators in small sizes. The PMSM has low inertia, large power-to-volume ratio, and low noise as compared to a permanent magnet DC servomotor having the same output rating [1] [2]. However, the disadvantages of this machine are the high cost and the need for a more complex controller because of the nonlinear characteristic.