Design, Analysis, and Sensorless Control of a Self-Decelerating Permanent-Magnet In-Wheel Motor

This paper is to propose a new self-decelerating permanent-magnet (PM) in-wheel motor for low-speed and high-torque drive of electric vehicles (EVs). This motor uses sensorless control and integrates advantages of magnetic gear and those of PM machine together while gear inner rotor is removed. The key is the magnetic gear, which can reduce the size of the motor and achieve the similar torque amplification provided by a mechanical gearbox and does not require maintenance or cause breakdown issues. The topology and the operating principle of the proposed in-wheel motor are analyzed; the effects of flux modulated by the magnetic gear and the static characteristics are investigated by using the finite-element analysis. To solve the problems of mechanical sensors, an improved sliding model observer for sensorless control is studied. Then, the evaluation of the system performances is conducted by the simulation based on the MATLAB/Simulink and the experiment based on a prototype. Both the simulation and the experimental results show that the system can provide low-speed high-torque driving for EVs without mechanical gears and sensors.