Abstract:

In an electric vehicle driven by in-wheel motor,the motor,the wheels and the brake are all embeddedin the wheels.This configuration not only increases the unsprung mass but also results in critical vibration of the inwheelmotor system due to the nonuniform motor air-gap caused by road excitation.In order to solve these problems,based on the novel in-wheel motor topology scheme put forward in their early work,the authors set up a novelvehicle vibration model and derive the frequency response functions of the vehicle riding comfort indexes whichfit varied road unevenness,such as the multi-mass system body acceleration,the relative dynamic tyre load,thedynamic suspension deflection and the relative displacement between the rotor center and the stator center.Finally,the sensitivity analyses of some important structural parameters,such as the total mass of in-wheel motor,the massratio of the stator to the rotor,the bearing stiffness,the rubber bushing stiffness,are carried out to reveal the effectsof the parameters on the vehicle riding comfort indexes.The results show that the rubber bushing damping is thegreatest influence factor of the body acceleration and the suspension working space,with the corresponding sensitivitiesbeing up to 10.33 and 10.21,respectively; that the bearing stiffness is the most sensitive factor of the relativedisplacement between the rotor center and the stator center,with the corresponding sensitivity being up to 12.07;that the total mass of in-wheel motor is the most sensitive factor of the dynamic tyre load,with the sensitivity beingup to 10.49; and that,among all the above-mentioned parameters,the stator-to-rotor mass ratio has the slightesteffect on the vibration response indexes.

Key words: electric vehicle, rubber bushing, in-wheel motor, frequency response function, sensitivity