Package-Oriented Multiphysics Design of an Axial-Flux Integrated Drive Module for In-Wheel Applications

Abstract This paper presents a package-oriented multiphysics analysis of a compact axial-flux integrated drive module for in-wheel applications. In wheel-end drive systems, the traction motor and reduction mechanism must be accommodated within a severely constrained axial envelope; therefore, reducing the axial stack length and the number of mechanical interfaces is critical for improving package density and integration feasibility. To address this requirement, an axial-flux permanent-magnet (AFPM) motor and a two-stage axial-flux coaxial magnetic gear (AFCMG) are integrated in the axial direction using a shared-rotor configuration. The proposed module consists of a 9-slot/6-pole AFPM motor and a two-stage AFCMG, achieving a total reduction ratio of 13.33:1. A low-permeability nonmagnetic rotor core is employed to reduce magnetic flux leakage through the rotor core and to secure an axial flux-transfer path toward the AFCMG. Three-dimensional multiphysics numerical analyses are performed to evaluate the electromagnetic, demagnetization, thermal, and structural characteristics of the proposed module. The results show that the AFPM motor satisfies the rated output of 1 kW at 3000 rpm, while the AFCMG output stage produces 42.44 Nm at 225 rpm. Compared with a conventional separated configuration, the proposed integrated module reduces the axial stack length by 37.19% while maintaining an overall efficiency of 94.35%. In addition, local demagnetization, temperature rise, and mechanical stress are analyzed under rated and overload conditions to evaluate the multiphysics behavior of the proposed integrated structure.