乘用车后扭力梁悬架系统动态特性仿真与试验研究

发布时间：2018-09-01 05:34

【摘要】：当汽车以中速行驶时,轮胎与不平路面之间的相互作用是车内振动的主要激励源。该激励力通过轮胎系统传递到悬架,经过悬架系统的缓冲与减振作用后传至车身,从而引起车身振动和车内噪声。工程实践中,应用后扭力梁悬架系统的前置前驱(FF)乘用车在中低速行驶过程中出现较明显的噪音已成为普遍性问题,如何通过优化悬架系统设计以改善整车NVH性能引起业内广泛关注。论文以中低档乘用车广泛应用的后扭力梁悬架系统作为研究对象,以仿真与试验相结合的方式深入研究其动态特性,以及基于悬架系统动态特性的整车振动分析。将悬架系统与车身连接处的橡胶衬套刚度作为关键影响因素,进行以改善悬架系统模态分布以及降低底盘振动响应为目标的影响规律研究。为了客观全面地反映悬架系统的固有特性以及振动传递特性,对扭力梁悬架系统的动态特性进行了试验测试分析,得到系统的试验模态参数、振动传递函数(VTF)以及各弹性阻尼元件的特性参数。上述参数的获取也为仿真建模工作提供试验数据支持以及检验模型的依据。根据有限元原理,以Hyper Works软件作为仿真计算平台,对扭力梁悬架系统的动态特性进行仿真分析,重点讨论有限元建模中各部件特性的等效表达方式,各约束边界的简化模拟原理。提出了橡胶衬套动刚度当量化的赋值方法以及铁制工装代替复杂轮胎系统边界的处理方式,并根据试验测试数据验证其有效性。依托上述建立的扭力梁悬架系统有限元模型,以悬架与车身连接处安装衬套的各向刚度作为单一变量,对悬架系统的低阶模态频率进行灵敏度分析；并讨论了衬套某一刚度方向与悬架系统某阶模态振型之间的对应关系,揭示了悬架系统模态分布随衬套刚度的变化规律。研究表明,悬架系统前三阶模态振型主要表现为Z向与X向的弯曲,因此模态频率也受这两个方向的刚度变化影响较大。为了进一步揭示悬架系统动态特性与整车振动之间的关系,以后扭力梁悬架子系统为基础,补充前悬架子系统、转向子系统、轮胎子系统以及车身子系统的建模工作,完成整车参数化模型的搭建。在此基础上定性讨论车内底盘处垂向振动加速度响应随安装衬套刚度的变化规律,并结合实车道路测试结果进行有效性验证。研究表明,减小衬套整车安装方向Z向的刚度对降低车内中低频振动有利。综上所述,论文从多个角度全面分析了扭力梁悬架系统的动态特性,以及各关键因素对动态特性的影响规律。同时,重点讨论了悬架系统动态特性中衬套刚度特性对整车振动的影响,为路面激励经由悬架系统传至车身的减振研究工作提供指导,进而提升整车NVH性能。
[Abstract]:The interaction between the tire and the uneven road is the main source of vibration when the vehicle is moving at medium speed. The excitation force is transferred to the suspension through the tire system, and then transmitted to the body after the suspension system's cushioning and damping action, thus causing the body vibration and the vehicle interior noise. In engineering practice, it has become a universal problem that the front (FF) passenger car with rear torsion beam suspension system appears obvious noise in the course of middle and low speed driving. How to optimize the design of suspension system to improve the performance of vehicle NVH has attracted wide attention in the industry. In this paper, the rear torsion beam suspension system which is widely used in medium and low class passenger cars is taken as the research object. The dynamic characteristics of the suspension system and the vibration analysis of the whole vehicle based on the dynamic characteristics of the suspension system are deeply studied by means of the combination of simulation and test. Taking the stiffness of rubber bushing at the joint of suspension system and body as the key factor, the influence law of improving the modal distribution of suspension system and reducing the vibration response of chassis is studied. In order to reflect the inherent characteristics and vibration transfer characteristics of suspension system objectively and comprehensively, the dynamic characteristics of torsional beam suspension system are tested and analyzed, and the test modal parameters of the system are obtained. Vibration transfer function (VTF) and characteristic parameters of each elastic damping element. The acquisition of the above parameters also provides experimental data support for simulation modeling and the basis for checking the model. According to the principle of finite element, the dynamic characteristics of torsion beam suspension system are simulated and analyzed with Hyper Works software as the simulation platform, and the equivalent expression of the characteristics of each component in finite element modeling is discussed emphatically. The simplified simulation principle of each constraint boundary. The evaluation method of dynamic stiffness of rubber bushing and the method of replacing the boundary of complex tire system with iron tooling are put forward. The validity of the method is verified by the test data. Based on the above finite element model of torsional beam suspension system, the stiffness of the bushing installed at the joint of suspension and body is taken as a single variable to analyze the sensitivity of the low-order modal frequency of suspension system. The relationship between the stiffness direction of the bushing and the mode shape of the suspension system is discussed, and the variation of the modal distribution of the suspension system with the stiffness of the bushing is revealed. The results show that the first three modes of suspension system are mainly bending in Z direction and X direction, so the modal frequency is greatly affected by the stiffness variation in these two directions. In order to further reveal the relationship between the dynamic characteristics of suspension system and vehicle vibration, the modeling work of front suspension subsystem, steering subsystem, tire subsystem and vehicle body subsystem is added based on the torsion beam suspension subsystem. Build the parameterized model of the whole vehicle. On this basis, the variation of vertical vibration acceleration response of the chassis with the stiffness of the mounting bushing is discussed qualitatively, and the validity is verified by the test results of the real vehicle road. It is shown that reducing the Z-direction stiffness of the bushing direction is beneficial to the reduction of the mid-low frequency vibration in the vehicle. To sum up, the dynamic characteristics of torsional beam suspension system and the influence of key factors on the dynamic characteristics are analyzed comprehensively in this paper. At the same time, the influence of the stiffness characteristics of the bushing on the vibration of the whole vehicle is discussed, which provides guidance for the study of the vibration reduction of the road excitation transmitted to the body through the suspension system, and then improves the NVH performance of the whole vehicle.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U463.33

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