【作者】 何荣；

【导师】 管欣；

【作者基本信息】 吉林大学 ， 车辆工程， 2014， 博士

【摘要】 传统的整车开发设计理念，在整车厂商在与零部件供应商同步开发的过程中，概念开发阶段仅仅保障整车和部件性能，而对于耐久性和可靠性则是在设计验证阶段考虑的。节能环保提出了新的轻量化的要求，汽车轻量化是当前汽车设计开发最重要的目标之一。为实现这个目标，整车厂商在与供应商同步开发过程中，不仅会要求其保证整车性能，还会提出可靠性和耐久性的要求；同样，总成厂家也会要求零部件开发商在保证总成特性的同时，还需要考虑部件的可靠性、耐久性。根据调研，供应商在概念开发阶段保障性能的同时无法考虑可靠性、耐久性主要问题是由于在这个阶段无法准确预测分析出系统边界和部件周边的动态载荷和位形。究其原因，主要是因为应用于概念开发阶段的整车厂商和零部件供应商同步开发汽车的重要工具基于总成特性的汽车动力学模型中缺少了影响动态载荷关键环节的建模。本文从目前最急需的车轮动态载荷出发，在调研了影响其精度的关键环节模型的基础上，重点研究了概念开发阶段车轮动态载荷关键环节的建模方法，研究如何在概念开发阶段使得车轮动态载荷更为接近实际。围绕上述目标，本文的研究工作主要从以下几个方面开展：首先，面向动态载荷的整车动力学模型研究改进。簧载质量的运动是整车动力学模型运动的基础，其它部件的运动大多是相对于簧载质量描述的，建立了簧载质量特性模型，为其他部件的运动奠定了基础。转向系统中绕主销的转动会使得轮轴位置和姿态发生变化，从而影响车轮动态载荷，面向齿轮齿条转向系统，建立了齿轮齿条转向系统特性模型，其中考虑了齿轮齿条动力学、转向助力特性、转向立柱的弹性特性以及主销处的干摩擦特性。非簧载质量相对车身只有垂直方向自由度，悬架是两者之间的纽带，本文建立了悬架导向机构二力杆传力模型，准确计算了导向机构向簧载质量传递的力和力矩。其次，考虑胎体非线性特性的气胎车轮模型。轮胎由天然橡胶、合成橡胶、纤维、炭黑等材料组成，再加上内部所充气体的共同作用，充气轮胎胎体特性十分复杂，是目前车轮模型中一直欠缺的。本文建立了适用于概念开发阶段车轮动态载荷仿真的车轮模型，将其简化为刚性环和轮辋，在刚性环与轮辋之间建立了考虑气胎胎体本身硫化橡胶和所充气体共同作用表现出的不对称性、非线性、迟滞特性的六个方向完备自由度的动力学模型，使模型可以仿真车轮受地面激励时胎体往复变形的不同特性、基于输入变化带来的滞后响应、车轮加载卸载迁变时的动态特性。针对所建立的气胎车轮胎体六向非线性模型，研究利用MTS悬架K&C试验台获取胎体动态特性数据的方法，通过假定整车由车轮与悬架串联，根据试验台测量的接地点和轮轴中心点的变形分离出了气胎车轮胎体六个方向的非线性特性。以气胎车轮胎体实验数据为依据，采用参数分离的方法对模型中的静态参数和动态参数分别进行辨识，通过仿真与实验对比验证了辨识方法的有效性。再次，悬架承载特性瞬态模型的建立。悬架承载特性是将悬架作为一个整体受到垂直方向激励时垂直载荷表现出来的特性。垂直运动是轮轴的主运动，轮轴相对于簧载质量只在垂直方向有自由度，其运动由悬架垂直动力学确定。传统的应用于操纵稳定性和平顺性分析的悬架承载特性模型没有考虑悬架承载系统的摩擦特性或者只考虑仅仅与位移有关的稳态摩擦力包络线模型，不能真实模拟悬架受到垂直激励时的特性。本文建立了考虑悬架螺旋弹簧、减震器、弹性限位装置、导向杆系、横向稳定杆、橡胶衬套mount、strut内部以及它们之间的间隙、耦合、摩擦表现出的非线性、不对称性、滞后特性、迟滞特性的悬架承载特性瞬态模型，通过微分方程实时求解悬架承载力。针对所建立的模型，设计了利用单轴式悬架综合试验台测量悬架垂直特性的静态和动态参数辨识实验并研究了模型的参数识别方法。然后，考虑不对称性的悬架KC修正模型的建立。不同长度和角度布置的悬架连杆决定了悬架运动学的变化规律，现有悬架大都通过橡胶衬套与底盘铰接点相连，悬架杆系受到轮轴作用力会产生弹性变形，所以车轮除了垂直自由度之外，在其他方向上需要考虑悬架K&C特性产生的附加变形，以更精确地描述轮轴的位置和姿态。传统的KC修正模型以线性或非线性穿越中心线对悬架运动学和弹性运动学引起的轮轴位形进行补偿，没有考虑由于悬架本身不对称性、杆件的柔性和弹性元件特性造成的迟滞区间。本文建立了考虑不对称性的悬架KC修正模型，采用反映迟滞环包络线的Fancher公式对运动学、弹性运动学引起的轮轴位置和姿态变化进行修正。针对采用分布获取和经验预估的方法获取Fancher模型参数时，在工程实施中会出现较大的随机性，提出了整体拟合的方法，一次性获取所有参数，减少了计算的误差，提高了模型的仿真精度。通过仿真与实验对比，证实了辨识方法的有效性。最后，概念开发阶段车轮动态载荷仿真研究。首先，在实验室性能动力学模型的基础上编制了用于概念开发阶段车轮动态载荷预测的考虑总成非线性的动力学模型程序；其次，利用总成台架实验结果对各总成系统的正确性进行了验证，验证了悬架承载特性、KC修正特性、转向系统干摩擦特性以及轮胎的力学特性。再次，选取典型工况对操纵稳定进行了验证，通过应用于车轮动态载荷的整车动力学模型的仿真结果与实车场地操纵稳定性试验结果进行对比，验证了所建模型在稳态性能上与实车的一致性，为进一步对动态载荷的仿真研究奠定了基础。最后，选取了激发关键环节的典型工况，在保证其它模型均相同的情况下改变关键环节模型特性并比较车轮动态载荷的变化，仿真结果表明所建立的模型已经有效描述了车轮动态载荷的关键环节和关键因素，揭示了关键环节模型对车轮动态载荷的影响，验证了模型的有效性。更多还原

【Abstract】 In traditional vehicle development and design philosophy, during the synchronousdevelopment process of vehicle manufacturers and parts suppliers, the performance ofvehicle and component is considered during concept development stage, while the durabilityand reliability are protected during design validation stage. Energy-saving proposes newrequirements of lightweight, which is one of the most important goals of currentautomobile design and development. To achieve this goal, the performance、durability andreliability must be considered at the same time.According to our survey, the main problem that supplier cannot consider durability andperformance simultaneously is that dynamic load of the system boundaries and componentssurrounding cannot be accurately predicted during the concept development stage. The mainreason of the problem is that vehicle dynamic model based on characteristic lack the keyaspects of dynamic load model.In this paper, the wheel dynamic load which is the most urgent need is discussed. Onthe basis of investigation of the status of the relevant models affecting the accuracy of wheeldynamic load, we focus on exploring the modeling approach of wheel dynamic load invehicle dynamic model based on characteristic and studying how to improve the accuracy ofwheel dynamic load during concept development stage. The main contents of this paperconsist of the following five areas.First，the study and improvement of vehicle dynamic model based on dynamic loads.The movement of sprung mass is the basis of the movement of vehicle, and the movement ofother parts is almost described relative to sprung mass. The sprung mass characteristics model is established to lay the foundation for the movement of other parts. Rotating aroundkingpin will make the position and attitude of the spindle change in steering system. For therack and pinion steering system, the characteristics model of rack and pinion steering systemis established. According to theory of roll center, suspension guiding-mechanism model isestablished to accurately calculate the forces and moments transferred to sprung masssystem.Second, pneumatic tire model considered nonlinear characteristic of carcass. Tire ismade from natural rubber、synthetic rubber、fiber、carbon black and so on, plus the combinedeffect of the gas inside, the characteristic of tire carcass is very complicated, which is thewheel model lack of currently. The nonlinear characteristic pneumatic tire model of completefreedom in six directions which can characterize the properties of asymmetry、nonlinearityand hysteresis is established. For the nonlinear carcass model established, the experiment ofsteady-state and dynamic characteristic of pneumatic tire is designed by KC suspension testrig. Assuming vehicle is connected with wheel and suspension in series, the nonlinearcharacteristics of carcass in six directions are isolated according to the deformation of theground and the center of spindle. According to the experimental data, the acquisition methodof the model parameter is researched, and the validity of identification method is confirmedthrough simulation and experimental comparison.Third, suspension bearing characteristic transient model is established. Suspensionbearing characteristic is the characteristic of the suspension as a whole subject shown whensuffered vertical excitation. Traditional suspension bearing characteristic model applied tohandling stability and ride comfort does not consider the friction characteristic of thesuspension or just consider the steady-state friction envelope model only associated with thevertical displacement. Adopting the idea of separation of static and dynamic friction, thesuspension bearing transient characteristic model is established and suspension loads arecalculated by differential equations in real time. For the model established, the static anddynamic parameter identification experiment of the suspension is designed through uniaxialsuspension comprehensive test bench, and the acquisition method of the model parameter is researched.Fourth, hysteresis characteristic suspension KC correction model is established.Suspension rod of different length determines the variation of the suspension kinematics; dueto extensive use of rubber bushing, when subjected to external force, suspension rod willproduce elastic deformation which called compliance. The traditional KC correction modeluse linear or non-linear centerline to describe the deformation caused by kinematics andcompliance. In this paper, Borrowing Fancher formula, hysteresis characteristic suspensionKC correction model is established. To obtain the parameters of the Fancher model with thestep method and experiments often leads to large randomness in the engineering praxis. Aone-time non-linear fitting method to obtain all parameters without estimation is proposed toreduce the calculation error, and the validity of identification method is confirmed throughsimulation and experimental comparison.Last, the research on simulation of wheel dynamic load during concept developmentstage. The correctness of each assembly system is verified by using assembly bench testresults. By the comparison with the results of the actual vehicle handling and stability test,the consistency of the model is verified on the steady-state performance. In other models areguaranteed the same circumstances, the characteristic of key model is changed to comparethe wheel dynamic load, the simulation results show that the key characteristics of the modelaffect the wheel dynamic load significantly, verifying the validity of the model.更多还原