基于车-路相互作用的车辆失稳机理及主动安全控制研究

The safe driving performance of the vehicle is closely related with the vehicle suspension, road surface characteristics, the adhesion state between tire and road surface. This project aims at the high-dimensional system of vehicle-pavement. The instability mechanism and control strategy of the vehicle at the statue of high speed, heavy-load, emergency steering, emergency braking and other complicated conditions are researched. The project puts forward the road surface morphology characterization methods that meets the requirement of vehicle-pavement system modeling. It can quantitatively describe three-dimensional micro and macro characteristics of road surface and research the influence of road surface morphology on tire/road friction performance. Based on the combination of theory and experiment, the shape of tire in contact pattern and non-uniform stress distribution characteristic are analyzed and the nonlinear switching friction force in sliding and adhesive area is designated. The adhesion mechanism of tires and road surface in contact area is revealed. Then a non-linear tire model with considering dynamic friction coefficient is established. The estimation methods of tire/road surface friction coefficient, longitudinal force，the lateral force and slip rate are proposed. The limitation of driving force, braking force related to the road adhesion conditions and the stability of steering and braking are discussed to clarify the mechanics mechanism from the steady sliding state to the instable sliding state. The combination control strategy of active steering, wheel sliding rate and semi-active suspension aiming at vehicle active safety is established. The research results will enrich the vehicle-pavement interaction research content, and provide the theory support for the vehicle safety driving under the complicated working conditions.

车辆安全行驶与悬架性能、道路表面特性、轮胎与路面附着状态有着密切的关系。本项目拟针对车-路高维系统，开展车辆在高速、重载、紧急转向、制动等复杂工况下失稳机理及控制研究。提出适用于车-路系统建模需求的路表形貌多尺度表征方法，定量描述路表三维微、宏观特征，研究路表形貌对轮胎/路面摩擦性能影响规律；结合理论与试验分析轮胎在接触印迹的形状、非均匀应力分布特征，明确在滑移、附着区摩擦力的非线性切换关系，揭示在复杂工况下轮胎与路面的附着机理；建立考虑动态摩擦因数的非线性轮胎模型，提出轮胎/路面摩擦因数、纵向力、横向力和滑移率估算方法，探讨与路面附着条件相关的驱动力、制动力极限及转向、制动稳定性问题，阐明从稳态转动到失稳滑移力学机理；基于轮胎与粗糙路面接触形成机理，构造针对车辆主动安全性的主动转向、车轮滑移率和半主动悬架的控制策略。研究成果将丰富车-路相互作用内容，为复杂工况下车辆安全行驶提供理论支持。

基于分形布朗运动随机中点位移和Diamond-Square算法，从分形几何学的角度定量描述路表的三维微、宏观的自相似特征。通过对重构的三维路面谱和理论路面谱的功率谱密度、残差平方和、相关系数对比分析，验证了由分形重构的路谱具有较高的重构精度。分析了轮胎与三维粗糙路面多点面接触下和传统点接触模型下的车体加速度、悬架变形和轮胎力的响应的区别，多点面接触下的模型反应出了轮胎真实的垂向包容特性，而且在轮胎的侧向力差异明显。同时也实现了在多体动力学软件中对三维路面和改进轮胎模型的嵌入和二次开发。. 为保证轮胎接地模型更加准确性，在传统的LuGre动态轮胎模型的基础上进行改进。将轮胎与路面接触均匀压力分布改进为任意压力分布函数分布，将轮胎垂向载荷对轮胎凹凸性因子和轮胎印迹长度的影响考虑在内。改进后的LuGre轮胎模型减少了模型的输入变量，保证了轮胎的有效滚动半径和轮胎与路面的接地印迹长度是随轮胎垂向载荷变化而变化的。通过与经典魔术轮胎模型对比，验证了模型的有效性，通过在频域下的仿真分析，进一步验证改进后的LuGre轮胎模型的稳定性。. 建立了基于半主动悬架和主动六轮转向的重载车辆垂向/侧向耦合动力学模型，应用协同控制策略同时改善了车辆的平顺性和操纵稳定性，同时提高了车辆的行驶安全性。将滑模变结构控制器和ABS制动系统相结合，融合差动制动原理对车辆各个轮胎上的制动力进行再分配，使得车辆产生额外的附加力矩，对车辆行驶状态进行修正。为扩展车辆对路面的适应性，提高控制精度，使得车辆在多数路面上都可以获得较好的防侧翻能力，在防侧翻控制算法中加入路面识别模型，达到了车辆制动系统在实施车辆防侧翻控制时的自适应、实用性、可靠性，最后在硬件在环实验平台上验证了控制策略的可行性。