Suspension Internal Model Control With Active Ripple Rejection of Single-Winding Bearingless Flux Switching Permanent Magnet Motor

Single-winding bearingless flux switching permanent magnet motor (BFSPMM), characterized by its frictionless operation, maintenance-free nature, and high efficiency, holds the potential to fundamentally address the issues of bearing erosion and failure in marine propulsion motors caused by harsh oceanic environments. However, the torque and suspension forces are strongly coupled, and the radial forces are complex and variable, resulting in significant rotor displacement ripples that severely impact the performance of electric drive systems. Herein, a suspension internal model control strategy with active ripple suppression is proposed. Firstly, based on the magnetic field modulation theory, the mechanism of unbalanced magnetic pull is analyzed in detail, and the corresponding expressions are established. Then, a rotor dynamic model is derived from the differential equations of a whirl for the suspended rotor, which facilitates the construction of the BFSPMM internal model. A linear extended state observer is employed to obtain smoother displacement error signals, differential signals, and account for unmodeled dynamics. Subsequently, an inverse system model for the controllable suspension force is derived, and the internal model controller is formulated and analyzed in an innovative PD-based structure. This approach not only enhances the controller's performance but also simplifies the tuning process, requiring only two parameters to be adjusted. Finally, the performance of the proposed method is analyzed theoretically, and its effectiveness is validated through experimental verification.