Development of Reliable Gearless Motors for Electric Vehicles

In this paper, a new class of reliable gearless motors, dubbed as the magnetic steering (MS) motor, is proposed to realize the concept of the magnetic differential (MagD) system for direct-drive electric vehicles. While the electronic differential (ED) system can control two individual motors to provide the differential action in the absence of mechanical differential, it suffers from reliability concerns upon errors from the individual motors. The proposed MagD system instead utilizes the MS-field excitation to interlock the magnetic fields in two rotors of the MS motor. With the control of MS-field excitation, the two rotors can be differentiated to generate appropriate torque levels for two driving wheels. As a result, the MagD system can offer higher reliability than the ED system. The machine performances of the proposed MS motor are evaluated by finite-element analysis, and the operating performances of the proposed MagD system are testified by system-level simulation.