A Study on Active Magnetic Bearings for Machine Tool's High Speed Spindle

This paper describes a high-speed spindle with fivedegree- of-freedom active magnetic bearings. High efficient magnetic bearings of this spindle provide noncontact, no rubbing and permanent life suspension. The spindle is f 49.1 mm in diameter and 268-mm long. The position and attitude of the center of mass of the spindle is controlled by a centralized PID compensator making use of DSP. Thus, the control bandwidth of this magnetic bearing is about 250 Hz. An exclusive controller and an amplifier for the spindle rotation enable to control its rotation speed. Moreover, it takes only 10 seconds. to power the maximum rotation up to 70,000 r/min. and to stop, and the motor of the spindle is powerful enough to 11 kW at maximum.