轮毂驱动电动汽车垂向机-电耦合振动机理及抑制方法研究

For electric vehicle driven by in-wheel motors, the method of designing or using active suspension is employed by the present scholars to enhance vehicle-body vibration performance, because of the problem of riding comfort deterioration caused by increasing unsprung weight. However, by this method, the wheel vibration can not be reduced greatly, which has a bad impact on lifetime of in-wheel motors and road handling of wheels. A self-made sample vehicle is researched from two aspects: wheel-hub driving-system and whole-vehicle modal analysis and motor magneticmoment analysis. The influence of main parameters of wheel-hub driving system on whole-vehicle vibration is summarized so that the truth of vertical dynamics and electromechanical-coupling vibration of electric vehicle driven by in-wheel motors can be discovered. Riding comfort design theory and suppression method of wheel-hub driving system are explored to provide design theory and method of development and production of electric vehicle driven by in-wheel motors. Firstly, vehicle vertical-performance and motor vertical-vibration evaluating indexes are established or defined. Then, kinematic stability analysis of wheel-hub driving system is conducted through poincare newton floquet(PNT) so that the principle of system catastrophe and destabilization caused by system-parameter change and outer excitation can be discovered and design method of system stability can be achieved. Finally, experimental system is built up and orthogonal experiment method is employed to test the nonlinear dynamics performance of sample vehicle. On this basis, effectiveness of stability measure and suppression method of vetical electromechanical-coupling vibration of whole vehicle is verified. Mechanism and principle of influence of changing paramters on sample-vehicle vibration performance are analyzed.

前人对轮毂驱动电动汽车因非簧载质量增加导致车辆行驶平顺性恶化等问题的研究，侧重于设计或采用主动悬架来改善车身振动，但对车轮振动的改善效果不明显，这会影响到轮中轮毂电机的寿命和轮胎接地性。本课题以自制的样车为研究对象，从轮毂驱动系统、整车模态分析和电机磁矩分析两方面入手，总结轮毂驱动系统参数对整车振动水平的影响，找到轮毂驱动电动车的垂向动力学及机-电耦合振动问题的本源，探索轮毂驱动系统平顺性设计理论、振动抑制方法。首先制定车辆和电机垂向振动性能评价指标，并通过动力学仿真、实验，分析设计参数对各项性能指标的影响；其次，采用PNT法完成轮毂驱动系统运动稳定性分析，揭示系统参数变化和外界激振下系统发生激变及失稳规律，找出系统稳定性的设计方法；最后，采用正交实验法对样车进行非线性动力学行为测试，验证理论研究的正确性、整车垂向机-电耦合振动抑制方法的有效性，分析参数改变对样车振动特性的影响机制及规律。

新能源汽车作为汽车行业绿色发展的代表性产物，逐渐成为车企未来研发的重要指向标。轮毂电机驱动式电动汽车因其机械构造简单、环保、传动效率高等优点，被业界称为电动车辆终极驱动形式，引起了新能源汽车企业和高校的广泛关注。但轮毂驱动在实际应用中还存在诸多挑战：第一，轮毂电机与轮毂结合增加了车辆非簧载质量，会恶化车辆行驶平顺性；第二，因轮毂电机直接与车轮固连，易受路面激励而产生较大振动，既可能加剧定子与转子间的磁隙波动，也将缩短电机结构的工作寿命；第三，电机力矩波动直接作用于车轮，会引起悬架前后方向共振以及整个驱动系统的振动问题。.本项目从轮毂驱动系统、悬架和电机磁矩波动两方面入手，探索轮毂驱动系统平顺性设计理论、振动抑制方法，并针对轮毂驱动电动汽车垂向机-电耦合振动特性开展了研究，结果表明轮毂电机带载后转速和转矩都存在波动情况，且随着负载的增加，电机转速、转矩的波动量都会增大；电机转矩波动对车辆悬架系统垂向振动的影响十分明显，尤其对作为非簧载质量的车轮影响较大，恶化了轮胎的抓地性，造成汽车垂向振动加剧和驱动力不稳定，不利于汽车驱动和行驶安全性。说明此类电动汽车产业化之前，需采取措施，优化电机或改型或设计电机减振系统或进一步研究电机的转矩和转速控制问题或重新优化匹配汽车悬架系统设计，以保证轮毂驱动电动汽车的行驶平顺性、动力性。.研究成果可为轮毂驱动电动汽车的产业化开发提供理论与方法，并为提高轮毂驱动电动汽车整车NVH 性能提供了可选方案。轮毂电机的优势在于对整车结构性的优化作用，传统的新能源汽车动力要通过多重传动系统的传递，而轮毂电机则是直接驱动轮辋，这个传动过程中效率损失几乎忽略不计。以轮毂电机直驱系统为地盘的汽车更容易实现智能化、网联化，应用前景广阔。同时该技术应用于混合动力汽车上，特别是野外作业的军车上，可轻松实现多轮驱动，降低研制成本。