Optimal design of an interior permanent magnet in-wheel motor for electric off-road vehicles

Interior permanent magnet in-wheel motor exhibits advantages of four-wheel independent drive and wheel-slip based steering, high efficiency and power density, wide field weakening capability, and more space within the vehicle, which is desirable for electric off-road vehicles. Since the motor flux linkage model is established by polynomial fitting, an optimization-based motor analysis model is proposed to handle the torque requirement and voltage constraint using Lagrange multiplier. To simplify the motor efficiency optimization problem, voltage constraint is neglected without efficiency alteration theoretically. Then an initial optimization of a motor with 16 poles and 18 slots is performed, before the number of turns per coil is chosen to meet the voltage constraint. Finally, the efficiency map of the optimal designed in-wheel motor is presented to validate the proposed method.