Multi-Level Design Optimization Considering Magnet Characteristic Constraint for Bearingless Permanent Magnet Vernier Motor

For bearingless permanent magnet (PM) vernier motor (BPMVM) with dual-purpose no-voltage (DPNV) winding, the accuracy of suspension force control is influenced by excessive magnetic saturation. While reducing current density can weaken magnetic saturation, it also lowers motor output performance. To address the tradeoff between suspension force control accuracy and motor output performance, this paper proposes a multi-level motor design optimization method that incorporates magnet characteristic constraints. Different from traditional design optimizations that focus solely on geometric parameters, slot fill factor, which is closely related to magnet characteristics, is also considered as a design variable. First, the motor topology is introduced and the adverse effect of excessive magnetic saturation on suspension force control is analyzed. Next, a multi-level design optimization is carried out for the BPMVM, considering magnet characteristic and output performance as constraint and optimization objective respectively. Compared with traditional single-level design optimization without considering slot fill factor, the proposed optimization method is proved to enhance output performance while ensuring the suspension force control accuracy. Finally, the prototype of BPMVM is tested based on established experimental platform to validate the superiority of the optimized motor.