Research On Vertical Dynamics And Solution Of In-Wheel Motor

As the key technology of the new generation electric vehicle drive system,the in-wheel motor has obvious technical advantages in reducing the weight of the vehicle,realizing the integration of mechatronics,flexible layout and improving the controllability of vehicles.However,due to the elimination of the traditional motor and transmission system,the in-wheel motor driven electric vehicle integrates the electric motor,the hub,the speed reduction mechanism and the braking system into one tire,thereby which significantly increases the unsprung mass and severely affects the ride comfort and handling stability.Under the uneven road roughness,the tire beats and the unbalanced load will lead to uneven stator airgap of the driving motor,resulting in vertical imbalance force,which further deteriorates the ride comfort of the vehicle.How to reduce or even eliminate the negative effects brought by the introduction of the in-wheel motor has become the most crucial issue to be solved in the research and development of the in-wheel motor driven electric vehicle.In order to solve the problems existing in the hub-motor-driven electric vehicle,Two new types of suspension configurations of the in-wheel dynamic vibration absorbing is presented which connects the motor stator shell with the vehicle body or the wheel through the spring damping system.and established the dynamic model and road roughness input model of the traditional suspension configuration,the traditional hub motor suspension configuration and two new types of in-wheel dynamic vibration absorption suspension configuration.The frequency response functions of the system such as the acceleration of the sprung mass,the moving stroke of the suspension,the dynamic deflection of the tire and the gap of the stator and the input of the unevenness of the road surface were analyzed.The parameter sensitivity analysis of vehicle ride index to the important structural parameters of suspension stiffness,bearing stiffness,vibration absorber stiffness,vibration damping and suspension damping were carried out.In order to improve the ride comfort and steering stability,the parameters of the suspension are optimized with the dynamic travel of the suspension and the clearance of the stator.The optimal stiffness damping parameters are obtained for each configuration,which improves the ride comfort and steering stability.Aim at the problem of vertical unbalance caused by uneven air gap between the stator and rotor of a motor,the switched reluctance motor is chosen as the driving motor in this paper.An analytical model of switched reluctance motor is established,the relationship between the angle and current of the switched reluctance motor and the inductance,flux,torque and radial force of the motor is analyzed.And the influence of motor eccentricity on the radial force,the optimal opening and closing angles are selected,the torque ripple of the motor is reduced,and the vertical imbalance force caused by the stator clearance is reduced.