Effect of the unbalanced vertical force of a switched reluctance motor on the stability and the comfort of an in-wheel motor electric vehicle

Switched reluctance motors are well suited to in-wheel-motor-driven electric vehicles because of their numerous advantages, such as a high torque density, a high operating efficiency and excellent power-speed characteristics. However, these advantages are overshadowed by their inherent high torque ripple and vibrations. The unbalanced radial force of the switched reluctance motor is one of the main reasons for vibrations of the switched reluctance motor but has attracted less attention for in-wheel motor applications according to previous research. In this paper, the vertical component of the residual unbalanced radial force of the switched reluctance motor, i.e. the vertical force of the switched reluctance motor, is taken into account in the stability and comfort analysis for in-wheel-motor-driven electric vehicles. The results in this paper indicate that the vertical force of the switched reluctance motor has a great effect on the lateral and anti-rollover stabilities of the vehicle. The direct cause of this phenomenon is that the vertical force of the switched reluctance motor is directly applied on the wheels, which will result in a significant variation in the tyre load, and the tyre can easily jump off the ground. Furthermore, the frequency of the vertical force of the switched reluctance motor covers a wide bandwidth which involves the resonance frequencies of the vehicle body's vibrations and the wheel bounce. As a result, the comfort of the vehicle is greatly harmed. Therefore, the effect of the vertical force of the switched reluctance motor on the the comfort of the vehicle is also considerable in some resonance situations. The conclusion is that the vertical force of the switched reluctance motor not only causes the stability of the vehicle to deteriorate but also has a considerable effect on the the comfort of the vehicle, and an appropriate control method for the switched reluctance motor is desired.