Design and Optimization Analysis of Coreless Stator Axial-Flux Permanent Magnet In-Wheel Motor for Unmanned Ground Vehicle

In this article, a coreless stator axial-flux permanent magnet (CSAFPM) indirect drive (ID) in-wheel motor is proposed and researched taking into consideration the multiphysics constraints, including electromagnetic performance and mechanical strength for unmanned ground vehicles (UGVs). At first, two 12-slot-14-pole CSAFPM motors with different rotor structures are designed to meet the vehicle rim space and driving system demand. In addition, the rotor parameters are optimized to obtain higher torque density based on the response surface method (RSM) and finite element model (FEM). Meanwhile, the electromagnetic performance of optimized motors with different rotors is compared, including back electromotive force (EMF), output torque capability, and efficiency characteristics. The results indicate that the Halbach-array PM rotor has higher torque and efficiency than the spoke-type PM rotor. On that basis, the thermal stress and deformation of the stator support are analyzed and optimized, considering material property and temperature distribution. In addition, the stress of PM rotor, annular gear, and gear reducer are analyzed and optimized to achieve higher torque density. Finally, a 35-kW prototype is manufactured and tested to verify the performance of the design.