轮毂电机驱动电动汽车机电耦合垂向动力学特性

电动车用轮毂电机受路面激励和车重的双重作用，定转子相对偏心进而产生不平衡磁拉力，其垂向分量与车辆悬架系统的垂向振动相耦合，影响电动汽车的平顺性、舒适性等性能。针对这一机电耦合问题，以一台永磁式轮毂电机为研究对象，利用磁场叠加法获得负载气隙磁密分布，引入复数相对磁导和偏心磁导修正系数，建立考虑定子开槽效应的电机偏心磁场和不平衡磁拉力解析模型，并通过有限元仿真和样机试验验证了解析模型的有效性。根据悬架系统的垂向振动与电机偏心不平衡磁拉力的实时耦合关系，利用拉格朗日法求解车辆动力学方程，建立1/4车身垂向耦合振动模型。以轮毂电机定子垂向振动加速度、车身垂向振动加速度、悬架动挠度和轮胎动载荷为主要指标，研究机电耦合效应对车辆垂向动力学特性的影响，揭示不平衡磁拉力输出特性与车辆动力学响应之间的机电耦合机理。研究结果表明,机电耦合效应使电动汽车的平顺性、操稳性和安全性等性能总体下降。

Vertical dynamic characteristics of electromechanical coupling of in-wheel motor drive system for electric vehicle

Due to the double action of road excitation and vehicle weight, the stator and rotor of the in-wheel motor (IWM) for electric vehicles (EVs) are relatively eccentric, thus generating an unbalanced magnetic force (UMF). When the vertical component of UMF is coupled with the vertical vibration of the suspension system of the vehicle, the ride comfort and other properties of EV are affected. To study this electromechanical coupling problem, by taking a permanent magnet IWM as the research object, the vertical dynamic characteristics of electromechanical coupling of an IWM drive system for electric vehicle were investigated. Firstly, the air gap flux density distribution of IWM under load was obtained by superposition method of magnetic field. By introducing complex relative permeance and correction coefficient of permeance when the motor was eccentric, analytical models of the eccentric magnetic fields of IWM and UMF were obtained with the stator slotting effect taken into account, and the validity of the analytical models was verified by finite element simulation and prototype test. Then, according to the real-time coupling relationship between the vertical vibration of the suspension system and the eccentric UMF of IWM, the dynamic equation of the vehicle was solved by using the Lagrangian method, and the vertical coupling vibration model of a quarter car body was established. Finally, taking the vertical vibration acceleration of the stator of IWM, the vertical vibration acceleration of the car body, the dynamic deflection of the suspension and the dynamic load of the tire as the main indexes, the effect of electromechanical coupling on the vertical dynamic characteristics of EV was studied, and the mechanism of electromechanical coupling between the output characteristics of UMF and dynamic response of EV was revealed. The results show that the electromechanical coupling effect impairs the ride stability, operation stability and safety of EV.