运动副间隙干摩擦诱发汽车摆振系统多极限环机理

The multiple limit cycles induced by the dry friction in kinematic pair clearance of mechanical system is a sort of dynamic phenomenon which exists but has been always neglected.It is investigated that the unsolved multi-amplitude and multi-frequency self-excited shimmy of vehicle relates to the phenomenon closely. The research on the mechanism of the above-mentioned engineering phenomenon was performed to explore the mechanism of the dry friction in kinematic pair clearance inducing the multiple limit cycles in mechanical dynamic system.Firstly, the dynamic model and its mathematic representation of dry friction in pair clearance of suspension and steering system are built on the basis of Coulomb and Stribeck model.Secondly,the clearance dry friction-oriented dynamic model of vehicle shimmy is established by combined the dry friction model and the classical dynamic model of vehicle shimmy.Then, the center manifold theory,multi-limit cycles judgement theorem and calculating Lyapunov quantities are applied to analyze the multiple limit cycles of system quantitatively.Finally,the distribution rule and the dynamical characteristic of multiple limit cycles are obtained by mathematical analysis.The project is helpful to provide a method of building the system model and solving technique for controling this vehicle shimmy.It is also able to provide a research approach for multiple limit cycles induced by the clearance dry fiction of the other dynamic mechanical system.

运动副间隙干摩擦诱导机械系统出现多极限环现象是工程中存在但长期被忽略掉的一种动力学现象，悬而未解的汽车多幅多频自激振动与其密切相关。本项目对以上发现的工程现象机理展开研究，探讨机械动力系统运动副间隙干摩擦诱导多极限环的本质。以Coulomb和Stribeck模型为基础，建立悬架与转向系统运动副间隙干摩擦力学模型及其数学表征，与经典的汽车摆振系统动力学模型相结合，建立考虑间隙干摩擦主导型的汽车摆振动力学模型；基于中心流形理论、多极限环判定定理和计算Lyapunov量对系统出现多极限环定性分析；用数值分析方法寻找多极限环分布规律及其动态特性。目的是为抑制该类型汽车摆振提供建模方法与求解技术，为其他动力机械系统间隙干摩擦诱发的多极限环提供一种研究方法。

运动副间隙干摩擦诱导机械系统出现多极限环振动是工程中存在但长期被忽略掉的一种动力学现象，汽车行驶中转向轮多幅多频自激振动与其密切相关；汽车制动副中干摩擦诱导制动器系统极限环振动和混沌振动有相似的机理，也是悬而未解的难题。为了认识运动副干摩擦诱发的非线性振动机理，本项目展开了三方面研究工作：.第一方面，以合作厂家某型轿车为样车，考虑轮胎悬架和转向系统运动副干摩擦，分别建立7自由度和9自由度自激摆振系统数学模型，运用定性和定量方法再现该车极限环摆振现象；寻找到产生该现象的系统主要参数和影响规律。并且建立了Adams虚拟样车模型，再现该车多极限环摆振现象，与数学模型求解结果一致。在上述研究中，发现对开路面附着系数（胎路摩擦系数）对汽车自激摆振有影响，建立了该系统模型，用定性方法获得极限环摆振机理，用数值方法找到附着系数对左右轮极限环摆振耦合影响规律。.第二方面，以合作厂家重卡为样车建立9自由度和11自由度双前桥转向系统及整车自激摆振数学模型，运用定性和定量方法寻找到该车极限环摆振现象。以及系统参数对多极限环振动的影响机理。并且在上述机理研究基础上，建立了该样车多极限环摆振控制策略，能较好抑制该类摆振。.第三方面，以干摩擦诱发制动副系统多极限环和混沌振动为研究内容，建立该系统2自由度和4自由度颤振数学模型，运用定性和定量方法找到了该系统极限环振动和混沌振动现象。提出了双块双缸盘式制动器模型，运用数值方法发现该系统存在多极限环现象，该模型有利于增加制动强度，但多频多幅自激振动影响制动稳定性。在上述基础上，探索设计了变刚度变阻尼双层制动块结构，用定性和定量方法寻找到制动摩擦副系统极限环振动，且极限环幅值低于单层摩擦块。