Practical operation of a bearingless permanent magnet-type synchronous motor (BPMSM) owes to stable suspension of the rotor. With the variation of operating conditions, conventional PID controller can't adjust its parameters, and the overshoot of the system response is big. Based on rotor flux orientation, a fuzzy self-adaptive PID controller was designed to control the suspending subsystem of a BPMSM. This controller can adjust the PID parameters on-line by fuzzy reasoning. The characteristics of dynamic tracking performance and steady-state precision of PID controller, together with strong robustness, good dynamic response and less overshoot of fuzzy controller are obtained. The simulation results show that this approach is effective in improving the static and dynamic performance of stable suspension of bearingless motors.

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