【作者】 李刚；

【导师】 陈南；

【作者基本信息】 东南大学 ， 车辆工程， 2018， 硕士

【摘要】 随着四轮轮毂电机独立驱动(4WID)电动汽车的快速发展,汽车结构发生了重要改变。轮毂电机的引入,简化了传动结构,提高了传动效率,便于整车控制。但同时也使簧下质量增加,导致车辆整体平顺性和轮胎接地条件恶化。除此之外,悬架垂横向耦合以及悬架系统与转向系之间的耦合更加密切,使车辆摆振这一世界性难题更加复杂和不确定。本文主要针对四轮轮毂电机驱动电动汽车这一车型,建立了包含悬架系统的5自由度摆振模型,系统研究了悬架非线性特性以及主销间隙和干摩擦不光滑非线性因素对车辆摆振现象的影响机理,并在摆振学科领域内率先开展了整车摆振道路实验。本文完成的主要工作如下:1.针对四轮轮毂电机独立驱动电动汽车这一新型汽车,利用拉格朗日方程建立了包含独立悬架系统的五自由度前轮摆振模型,并进行定性和定量分析。首先根据4WID这一新型汽车的特点以及影响摆振的主要因素,确立包含左右前轮绕主销摆角、左右悬架绕车纵轴、方向盘转角的五自由度摆振模型,利用拉格朗日方程建立其动力学平衡方程。然后结合轮胎动态侧偏特性和轮胎滚动约束方程,完成五自由度前轮摆振模型。最后根据对模型的定量分析得出了轮毂电机的引入导致摆振现象速度区间增大,相同速度下摆角幅值增大的结论。2.考虑典型非线性悬架系统对四轮独立驱动电动汽车这一新型汽车摆振的影响。在前文5自由度摆振模型的基础上,分别考虑非线性悬架系统中非线性阻尼器、非线性弹簧,并建立相应的非线性动力学模型。对其定量分析结果表明非线性悬架对车辆摆振现象有很大的影响,产生了多极限环现象,即产生多个摆振速度区间,并且在相同速度下,非线性悬架摆角幅值较小。随着悬架阻尼的增大,车轮摆角速度和悬架摆角幅值增加,而悬架摆角速度减小,悬架刚度对摆振现象几乎没有影响。3.讨论了线性悬架垂横向耦合非线性对摆振现象的影响。特别考虑线性悬架系统内部的垂横向间的耦合作用,并建立相应耦合非线性悬架模型。对比分析了线性悬架与耦合悬架对摆振现象的影响,结果表明悬架内的耦合对摆振区间中的后临界速度有稍微前移作用,并且对摆振形成前期幅值有较大影响,随着悬架阻尼增大,车辆摆角幅值和速度大幅增加。其次影响耦合作用的悬架横臂对悬架绕车纵轴的摆动有抑制效果,对乘坐舒适性的提高有重要作用。4.针对主销间隙和干摩擦不光滑非线性因素也给予了考虑。分别建立了非连续二状态间隙幅模型和静态Couloumb干摩擦模型,并对两者进行了定量分析。结果表明两者对摆振均有较大影响,随着主销间隙的增加,摆振速度区间增加,幅值增大;随着干摩擦的增加,摆振速度区间和幅值迅速减小。以此得出主销间隙和干摩擦是抑制车辆摆振的重要因素。5.搭建了四轮独立驱动电动汽车摆振试验车平台,并在摆振领域内率先进行了整车道路实验。首先根据用车目的和实验要求确定整车总体性能指标和关键结构形式设计,然后对关键子系统和零部件的安全性和实验性能进行仿真分析与验证。最后在整车上加装实验所需的转角传感器和轮速传感器,并进行整车台架测试和基本工况路试。在以上基础上,进行了多组不同速度下整车道路摆振实验,并根据实验结果对理论模型进行了验证,表明所建立的理论模型是可靠和正确的。更多还原

【Abstract】 The development of four-wheel independent drive(4WID)electric vehicles(EVs)has led to significant changes in modern vehicles.The introduction of the hub motor simplifies the transmission structure,improves the transmission efficiency and facilitates vehicle control.At the same time,it also increases the unsprung mass,resulting in deterioration of the overall ride comfort of the vehicle and the contact condition between tires and road.Besides,it also increases the coupling effect of the vertical vibration of the suspension and the shimmy of the steering system,make the global problem of vehicle shimmy more complicated and uncertain.In this paper,mainly focuses on the four-wheel hub motor drive model,establishes a 5-DOF model with a suspension system,and systematically studies the nonlinear characteristics of the suspension and the main pin gap and dry friction non-smooth nonlinear factors on the phenomenon of shimmy,and took the lead in launching the whole vehicle shuffling road experiment in the field of shimmy.The main tasks of this paper are as follows:First,for a new type of 4WID electric vehicle driving the electric vehicle,a 5DOF front-wheel-shimmy model including an independent suspension system was established based on the Lagrange equation,qualitative and quantification analysis was performed.Firstly,based on the characteristics of the new 4WID car and the main factors affecting the shimmy,a 5DOF shimmy model consisting of the left and right front wheel around the kingpin swing angle,the left and right suspension around the longitudinal axis,and the steering wheel angle was established using Lagrange.Then,the 5DOF front-wheel-shimmy model is completed by combining the tire’s dynamic cornering characteristics and the tire rolling constraint equation.Finally,according to the quantitative analysis of the model,the conclusion is drawn that the introduction of the hub motor leads to the increase of the speed range of the shimmy phenomenon and the increase of the amplitude value of the same speed slewing.Scond,consider the impact of a typical nonlinear suspension system on the 4WID electric vehicle,a new type of automotive shimmy.Based on the above 5DOF model,the nonlinear damper and nonlinear spring in the nonlinear suspension system are considered and the corresponding dynamic model is established.The simulation results show that the nonlinear suspension has a great influence on the phenomenon of vehicle shimmy,resulting in a multiple limit cycle phenomenon.Third,the effect of vertical suspension coupling due to linear suspension on the phenomenon of shimmy is discussed.Special consideration is given to the vertical lateral coupling effect of the linear suspension system and a corresponding coupling model is established.The influence of the linear suspension and the coupled suspension on the oscillation phenomenon is compared and analyzed.The results show that the coupling in the suspension has a slight forward movement in the post-critical velocity in the oscillation range,and it has a very early amplitude for the formation of the oscillation.Great influence.Secondly,the suspension cross arm that influences the coupling action has an inhibitory effect on the suspension of the suspension around the longitudinal axis of the vehicle.Fourth,consideration was also given to non-smooth non-linear factors such as kingpin motion gap and dry friction.The Discontinuous two-state gap amplitude model and Couloumb dry friction model of static friction model was established respectively,and both of them were quantitatively analyzed.The results show that both of them have a greater impact on the shimmy.With the increase of the main pin gap,the interval of the shimmy speed increases and the amplitude increases.As the dry friction increases,the interval and amplitude of the shimmy speed decrease rapidly.Finally,a 4WID electric vehicle shimmy experimental vehicle platform was built,and the entire vehicle road experiment was first conducted in the field of shimmy.First of all,according to the purpose of the vehicle and the experimental requirements to determine the overall performance of the vehicle and the key structure of the form design,and then the key subsystems and components of the safety and experimental performance of the simulation analysis and verification.Finally,the corner sensor and wheel speed sensor required for the experiment are installed on the vehicle,and the entire vehicle bench test and on-road operation are performed.On the basis of the above,a series of road-shuffling experiments for the entire vehicle at different speeds were performed,and the theoretical model was verified based on the experimental results,indicating that the established theoretical model was reliable and correct.更多还原