Design and Hierarchical Coordinated Optimization of an Outer-Rotor Hybrid-Excitation Flux-Switching Machine for In-Wheel Driving Applications
Zhiyuan Xu, Ming Cheng, Minghao Tong, Chunyu Lu
Abstract
This paper presents an outer-rotor hybrid-excitation flux-switching (OR-HEFS) machine with E-type stator cores, specifically designed for electric vehicles applications. To address the challenging working conditions encountered in in-wheel driving electric vehicles, an improved hierarchical coordinated optimization (HCO) method is proposed to optimize the proposed machine. This paper commences with an introduction to the structural evolution, and followed by the initial design stage of the proposed machine. Subsequently, in order to streamline the optimization process, the HCO method is launched by balancing the dimension-reduction and the comprehensive confidence of the optimization results. After optimization, an overall evaluation of the optimized OR-HEFS machine is conducted both by the finite element analysis and prototype experiments. The results indicate that the HCO method improves the performance of the optimized OR-HEFS machine by 18.7% lower iron loss, and 5.44% better flux-regulation capability than the initial design. Particularly for the torque characteristic, the optimized 6-19 OR-HEFS machine possesses 22.6% higher average torque and 63.2% lower ripple under the hybrid-excitation condition. Moreover, compared to the conventional outer-rotor flux-switching permanent magnet machine with traditional stator cores, the proposed OR-HEFS machine achieves nearly equivalent output torque with a 50% reduction in PM usage.