Suspension Flux Control with Model-Compensated Repetition Controller for Single-Winding Bearingless Flux-Switching Permanent Magnet Motor

The harsh marine environment often leads to bearing erosion and damage to propulsion motors. The single-winding bearingless flux-switching permanent magnet motor (BFSPMM), which operates without mechanical bearings, provides notable advantages, including frictionless operation, long service life, high back-EMF sinusoidal quality, and superior efficiency. But the BFSPMM faces significant challenges due to the strong coupling between its torque and suspension controls, as well as the speed-frequency ripple in rotor radial displacement, which severely impacts mechanical transmission performance. This paper proposes a suspension flux control strategy based on a model-compensated repetitive controller. A mathematical flux linkage model incorporating rotor dynamic eccentricity is developed, establishing a linear relationship between rotor displacement and flux linkage. The control strategy accounts for controllable suspension forces, unbalanced magnetic pull, and speed-frequency ripple in the rotor dynamics model. It employs a repetitive controller that integrates a repetitive signal generator, a model compensator, and a least mean square notch filter to compute the desired suspension flux. To enhance accuracy, a flux observer leveraging orthogonal characteristics is designed to measure the actual suspension flux. The effectiveness of the proposed method is validated through simulations and experiments, demonstrating its superior performance in steady-state and dynamic conditions.