Suppression of Imbalance Vibration in AMB-Rotor Systems Using Adaptive Frequency Estimator

Synchronous vibration due to rotor unbalance is a main disturbance source that drastically reduces the performance of a rotating shaft supported by active magnetic bearings. To suppress the imbalance vibration force without a rotational sensor, a novel adaptive notch filter (ANF) for frequency estimation based on the information of radial displacement signals in X- and Y-directions together is proposed. The structure and principle of the proposed technique used for the online extraction of synchronous signals and frequency estimation are presented, and the convergence properties of the algorithm are analyzed. Meanwhile, synchronous current nulling and synchronous force nulling achieved based on the ANF are investigated, respectively. Simulation and experimental results on a motor driveline system demonstrate a significant effect on the elimination of synchronous current and suppression of residual imbalance vibration force due to the displacement stiffness of the magnetically suspended rotor.