汽车–拖车组合系统中车轮摆振与车身摆振的耦合机理研究

The stability of car-trailer combinations is the research focus in this project. In practice, they might show not only the wheel shimmy phenomenon, which the passenger cars also have, but also the body shimmy phenomenon, which the passenger cars rarely have. Both phenomena belong to the shimmy problem in vehicle dynamics. This project is aiming to study the influences of the parameters of the towing car’s steering system and suspension system on both shimmy phenomena firstly. On this basis, any potential coupling mechanism between the two shimmy phenomena, as well as its physical interpretation and mathematical description, is expected in further investigation. This problem is proposed and investigated for the first time in both research areas of shimmy problem and stability of car-trailer combinations and it is still almost in blank. The methodology, performing a study from part to whole, from linear analysis to nonlinear analysis and from analysis to synthesis, is proposed to solve this problem. For this purpose, building the nonlinear dynamic theoretical model and virtural prototype model by which both shimmy phenomena can be described for car-trailer combinations, investigating the shimmy problem with the qualitative analysis and quantitative analysis methods in which the bifurcation analysis based on phase plane method, perturbation method and incremental harmonic balance method are specially considered for nonlinear systems, and proposing the reasonable hypothesis about the potential coupling mechanism will be performed step by step. The hypothesis is verified and might be modified when the experimental results from bench tests and road tests with the assistance of advanced optic sensor technology are compared. Finally a conclusion based on the hypothesis about the potential coupling mechanism has to be proposed and serves as a scientific and technological guideline for the optimal design of system components in car-trailer combinations.

本项目关注汽车–拖车组合系统的稳定性，此车辆系统不但具有类似于乘用车的车轮摆振现象，还具有乘用车鲜有的车身摆振现象，它们都属于车辆动力学中的摆振问题。将首先研究牵引车转向系统和悬架系统参数对两种摆振现象的影响，在此基础上进一步探究两种摆振现象潜在的耦合机理，并给出其物理解释和数学描述。此问题的提出和研究无论是在摆振问题的研究领域还是在汽车列车稳定性的研究领域都是首次，尚属空白。拟采用从局部子系统到整体系统，从线性分析到非线性分析，从分析到综合的研究方法来解决问题。为此需要建立融合两种摆振行为的系统的非线性动力学理论模型、虚拟样机模型，采用针对非线性系统的定性分析和定量分析方法来研究摆振问题，包括基于相平面法的分岔分析法、摄动法和增量谐波平衡法，提出耦合机理的假设。借助于先进的光学传感器技术，台架试验和道路试验将被用来验证和修正此假设。从而得出结论，为系统零部件的优化设计提供科学和技术参考。

本项目关注汽车–拖车组合系统的稳定性，此车辆系统不但具有类似于乘用车的车轮摆振现象，还具有乘用车鲜有的车身摆振现象，它们都属于车辆动力学中的摆振问题。本项目首先研究了牵引车转向系统和悬架系统参数对两种摆振现象的影响，在此基础上进一步探究两种摆振现象潜在的耦合机理，并给出其物理解释和数学描述。此问题的提出和研究无论是在摆振问题的研究领域还是在汽车列车稳定性的研究领域都是首次，尚属空白。本项目采用从局部子系统到整体系统，从线性分析到非线性分析，从分析到综合的研究方法来解决问题。为此，本项目分别建立了融合两种摆振行为的考虑悬架系统特性和考虑转向系统特性的非线性动力学理论模型，并利用Trucksim软件建立了相应的虚拟样机模型同理论模型相互验证。采用针对非线性系统的定性分析和定量分析方法来研究摆振问题，包括基于相平面法的分岔分析法、特征值法和增量谐波平衡法。在理论研究的基础上，本项目进一步设计搭建了摆振试验台架和摆振试验样车，并进行了国内业内首次的车轮摆振道路实验，开创了整车摆振实验的先河。试验结果表明所建立的理论模型是可靠且正确的，各结构参数对摆振行为均有不同程度、不同性质的影响。车轮不平衡质量、悬架失效对车轮摆振有较大影响。转向系刚度、阻尼以及悬架阻尼特性和失效行为对车身摆振临界车速影响最大可达10%左右。在耦合机理的研究中，本项目发现车轮高速摆振触发了车轮运动的共振现象，不但车轮的摆振行为将发散失稳，而且车轮垂向载荷的动态波动也会增大。这将进一步导致车轮及车轴的垂向有效载荷减小，侧偏刚度降低，从而影响系统的车身摆振行为。总体而言，本项目现有成果已经较为全面的研究了系统参数对两种摆振的影响，对于汽车拖车组合系统参数优化设计以提高其稳定性具有较强的实践指导意义。