Adaptive autocentering control for an active magnetic bearing supporting a rotor with unknown mass imbalance

This paper presents a new approach, called adaptive autocentering, that compensates for transmitted force due to imbalance in an active magnetic bearing system. Under the proposed control law, a rigid rotor achieves rotation about the mass center and principal axis of inertia. The basic principle of this approach is to perform on-line identification of the physical characteristics of rotor imbalance and to use the identification results to tune a stabilizing controller. This approach differs from the usual strategy of adaptive feedforward compensation, which models the effect of imbalance as an external disturbance or measurement noise, and then cancels this effect by generating a synchronous reference signal. Unlike adaptive feedforward compensation, adaptive autocentering control is frequency independent and works under varying rotor speed. Performance of the control algorithm is demonstrated in simulation examples for the case of rigid rotors with static or dynamic imbalance.