Design Optimization of Asymmetric Permanent Magnet Assisted Bearingless Synchronous Reluctance Motor

In order to improve the output torque performance of the PM assisted bearingless synchronous reluctance motor (PMa-BSynRM), a novel asymmetric rotor structure for PMa-BSynRM is proposed. Firstly, the proposed asymmetric rotor structure combines the symmetric flux barrier and asymmetric magnetic pole, and realizes the maximum value of PM torque and reluctance torque at the similar current angle based on the magnetic-field-shifting (MFS) effect, which enhances the output torque of the motor. Secondly, in order to obtain the optimal parameter values and improve the performance (high output torque, high suspension force, low torque ripple and low suspension force ripple) of the motor, the multi-objective optimization method based on fast non-dominated sorting genetic algorithm (NSGA-Ⅲ) is used to optimize the selected design variables, which are verified by finite element analysis (FEA). Thirdly, the simulation results confirm that the output torque of the optimal asymmetric motor is increased by 31.23%, compared with the symmetrical structure. Finally, the optimal prototype is manufactured and relevant experiments are conducted, which verified that the prototype has excellent torque and suspension force performance.