Harmonic Current Suppression of Magnetically Suspended Rotor System via Odd-Harmonic Fractional RC

As an efficient actuator for microvibration applications, a magnetically suspended rotor (MSR) system is always stymied by rotor mass imbalance and sensor runout, which will result in a harmonic disturbance in control current and further lead to severe periodic vibrations. In this paper, an odd-harmonic fractional repetitive control strategy is investigated for MSR systems to suppress odd-harmonic current with pertinence at low rotation speed. In contrast with conventional repetitive control (RC), only half of the delay units are required in the proposed control scheme. Therefore, it can achieve less computational burden and a faster convergence rate. Additionally, suppression accuracy of RC is vastly improved by adopting fractional delay filters, especially in fractional scenarios. The inset mode of RC is also modified for a simple system structure. Experimental results on a magnetically suspended flywheel are provided to validate the effectiveness of the proposed method.