High precision and low friction owing to the active control and the absence of mechanical contact are the major advantages of magnetic bearing system. Magnetic bearings are applied to various spindle systems requiring high precision and high speed operation.
In this study, the design, manufacturing, simulation and experiment of the high speed magnetic bearing system were performed.
Result of the simulation shows that nutation at high rotational speed cannot be avoided by using only decoupled digital PID controller, while it can be eliminated by adding low pass filter. In the experiment, digital PID controller is implemented by using high speed digital signal processor (DSP) board interfaced with a PC. The sampling frequency is fixed at 10 kHz. The best performance is obtained by using digital PID controller and low pass filter simultaneously. The maximum rotational speed is 69,000 rpm because of the first bending mode. The vibration amplitude of rotational center at 50,000 rpm is about 3㎛.
