Electric vehicles with in-wheel switched reluctance motors: Coupling effects between road excitation and the unbalanced radial force

The switched reluctance motor (SRM) has great application potential in in-wheel motor electric vehicle (IWM-EV) due to its advantages, such as a high starting torque for initial acceleration, a wide operating speed range and high efficiency to extend the battery service life. However, these advantages are overshadowed by its inherent vibration and noise due to the unbalanced radial force. For the vehicle vibration system, the vertical component of SRM unbalanced radial force, namely SRM vertical force, is one of the major concerns. This paper analytically investigates the coupling effect of SRM vertical force and road excitation on IWM-EV vibration. First, the system dynamics model of IWM-EV and IWM driving EV controller are proposed to include SRM vertical force; then the analytical models are solved to predict the vehicle dynamic responses at different speeds on periodic and stochastic road inputs with various amplitudes and coherence functions between left- and right-sides of the vehicle. It is concluded that SRM vertical force is highly coupled with road excitation and SRM airgap eccentricity, and such coupling effects yield a great impact on vehicle vertical vibration dynamics.