【作者】 管仁梅；

【导师】 管欣；

【作者基本信息】 吉林大学 ， 车辆工程， 2004， 硕士

【摘要】 制动器是汽车制动系统中最重要的安全部件，对汽车的使用性能有很大的影响。本文所研究的内容是围绕着汽车制动器总成多柔体模型在MSC.ADAMS中的建立、及相关参数对制动过程中制动器卡死和振动的影响而展开的。结合汽车动态模拟国家重点实验室和一汽客车公司底盘厂的合作项目——客车底盘制动系统异常磨损、自锁（发啃）及尖叫现象的研究， 针对大客车制动器总成在制动过程中出现异常现象：制动自锁现象、制动鼓和摩擦片的椭圆接触导致的楔效应、制动卡死及振动等现象，建立包括制动鼓、摩擦片、振动底板等元件及其弹性特性的动态仿真模型，分析制动器结构特性参数对以上现象的影响。本文建立的制动器总成多柔体模型是应用MSC.NASTRAN有限元软件对部件进行模态分析，将模态分析结果（模态坐标、模态转换矩阵、模态质量矩阵、模态刚度矩阵以及模态频率等）导入到ADAMS中，应用制动器力学模型， 建立制动器总成的多柔体模型。本文建立的制动器总成多柔体模型与其它方法不同的是：不光考虑各部件的弹性变形，还考虑了车轮和后桥等部件的转动惯量、后桥与车架之间的刚度、阻尼等特性对制动器制动过程的影响。针对客车制动器总成探索了在MSC.NASTRAN/MSC.ADAMS下进行多柔体建模的关键技术包括：应用PRO/Engineer进行三维实体建模，应用MSC.NASTRAN进行有限元分析和MSC.ADAMS进行动力学分析，共同建立了制动器总成多柔体模型，其中重点研究了鼓和摩擦片之间的柔性接触摩擦问题。对制动器制动的真实过程进行了仿真分析，得出了各零部件的受力、变形、速度和加速度等参数随时间的变化曲线。通过对制动器总成多柔体模型的动力学仿真和分析，得到了以下一些结论：1、本文建立的制动器总成多柔体模型，经过动力学仿真计算和分析，大致符合汽车的真实制动过程。2、摩擦力随着动摩擦系数的增加而增加，但是动摩擦系数高时，瞬时振动有较大的振幅，产生制动器振动，降低了制动器工作的稳定性；相反<WP=74>动摩擦系数低时，制动器振动得到抑制，但制动器制动容量变小。选择鼓式制动器摩擦片时，动摩擦系数的选择既要满足制动性能，同时也要满足稳定性。3、增大摩擦片的自锁角、或减小包角，都会使制动器制动效能变小，所以我们应兼顾稳定性和制动效能两方面。同时应提高其制造和装配精度。4. 由于时间的关系，本文没能实现制动器在制动过程中动摩擦系数和静摩擦系数之间的转换关系问题，所以没有仿真出制动器的颤振现象；也没有仿真出制动器的卡死现象，分析表明分析制动器卡死现象时，只考虑制动器的弹性是不够的，必须综合考虑摩擦副中静摩擦工况和半轴给制动器底板的力矩等影响。本文初步探索了制动器多柔体模型的建立，为制动过程中各种复杂现象的分析，提供一个方法和数据依据，有待不断地完善。本文建立制动器总成多柔体模型处理方法具有通用性，可随时更换其中任意的部件或将其应用于其它的接触模型问题中，为分析各种结构制动器和其它接触模型工作状况提供了便利。本文只对制动器的动力学特性进行了初步分析，在此基础上，还可以利用此模型作进一步分析。比如运用在MSC.ADAMS运算中得到的结果——运动关系和相互作用力，将其再输入到MSC.NASTRAN(有限元模型)中，进行热力学分析等。另外，对制动性能的评价，仅有制动器模型是不够的，还应建立包括制动器在内的整车模型，以分析悬架、转向等参数对制动过程的影响，以及更多工况下制动器的性能。以三维实体建模、动力学仿真和有限元为主线的制动器总成多柔体模型，能有效分析和解决制动器的复杂空间动力学问题，对制动器工作状态做出评价。在此基础上进行进一步的开发和研究，将对汽车制动器的研究、设计和开发提供方便的研究手段和有效的指导作用。更多还原

【Abstract】 Brake system is one of the most important security components in the vehicle and it greatly contributes to the performance of the vehicle. This paper mainly concerns modeling of flexible multibody of vehicle braking system with MSC.ADAMS, and how some parameters contribute to brake lock and vibration while braking.Combined with the research on a cooperative project between ASCL (State Key Laboratory of Automotive Dynamic Simulation) and Chassis Factory of FAW Bus Company——Research of abnormal wearing, self-locking and whistle on brake system of bus chassis, concerning with abnormal braking behavior of bus brake system like: self-lock, wedge effect arose by elliptical contact between drum and shoe, stuck and vibration, this paper have built dynamic simulation models of braking system including components of drake drum, brake shoe and lining and their elastic characteristic, and have analyzed the effect that structure parameters contribute to these problems.This paper use MSC.Nastran to analyze modes of components, and use ADAMS to load analysis result (mode coordinate, modes conversion matrix, modes stiffness matrix and modes frequency) combined with mechanical model to build flexible multibody model of brake system.The method of modeling flexible multiby in this paper is different with others that it concern not only the elastic deformation among components of brake system, but also revolution inertia of wheel and rear axle, as well as stiffness and damp between rear axle and chassis frame.Concerning with the bus brake system, this paper quest some key technologies of modeling flexible multibody with MSC.Nastran and ADAMS including: modeling three-dimensional geometry entry, FEA analysis of with MSC.Nastran, dynamical analysis with ADAMS, modeling flexible multibody of brake system with both software. Among these, the paper pays much attention on flexible contact friction between drum and shoe. By simulation of braking process, components’ characteristic of force, deformation, speed and acceleration relative to time can be achieved.As a result of dynamical simulation and analysis of the flexible multibody models, we <WP=76>have some conclusions below:1. The flexible multibody models built in this paper are proven to be accordant with the actual process by and large.2. The friction increase along with the dynamic friction coefficient. But there will be great instantaneous amplitude that would cause vibration of brake system and worsen the stability. On the contrary, with a lower dynamic friction coefficient, the vibration will be restrained but the capacity of brake system will be too low. When selecting brake shoe, the dynamic friction coefficient must fulfill the request of both brake capability and stability.3. To increase self-lock angle of the brake shoe or decrease the cover angle will lower the brake capability and the selection also should fulfill the request of both brake capability and stability. At the same time, it should pay attention on precision of production and assemble.4. Because of insufficient time, this paper does not implement switch between dynamical friction coefficient and a static one, then no harsh can be simulated. At the same time, no stuck was simulated either. It shows that it’s not sufficient only concerning elastic characteristic of components while analyzing stuck problem, but other factors like: temperature of brake system, components of suspension and steering, have to be included. This paper applies an elementary research on modeling flexible multibody of brake system, and provides a feasible solution and reference about analysis of complex braking process. This certainly needs more work to make it more and more capable and precise.The solution of modeling flexible multibody in this paper is universal to apply to other friction studies that only need to change some of the parts. It’s very convenient to analyze brake system with other structure or some other contact models with it.This paper only applies an elementary analysis on dynamic characteristic o更多还原