【作者】 柳江；

【导师】 喻凡；

【作者基本信息】 上海交通大学 ， 车辆工程， 2007， 博士

【摘要】 车辆悬架系统设计中,弹簧减振器等主要元件的力学特性及其匹配对车辆性能的影响至关重要,由于悬架系统结构、载荷和工况的多变性,使得基于物理样机的设计方法难以适应日益严格的悬架系统设计要求。随着CAD/CAM/CAE技术的逐步成熟,虚拟样机、虚拟试验技术被广泛地应用于汽车产品开发之中。因此,本文结合上海汽车工业科技发展基金项目,针对轿车中广泛采用的麦弗逊式悬架典型实例,进行了“基于虚拟样机技术悬架系统性能分析和优化设计”的研究。以桑塔纳2000车型为例,充分考虑弹簧刚度特性、减振器阻尼特性、橡胶衬套和减振器缓冲块等橡胶元件的非线性特性,在多体系统动力学软件ADAMS建立麦弗逊式前悬架精细模型,并进行运动学仿真,分析了不同工况下前轮定位参数的变化。仿真结果与试验数据进行了对比,验证了所建悬架系统模型的有效性。在此基础上分析了麦弗逊式悬架的侧载问题,提出悬架弹簧的优化设计目标。在麦弗逊式前悬架系统精细建模的基础上建立整车系统多体动力学模型,进行正弦扫描和随机路谱输入的整车平顺性仿真,并对随机路谱输入下的车身加速度功率谱密度进行试验验证,进而研究悬架系统中弹性/非线性元件特性(包括弹簧垂向刚度、减振器阻尼、衬套刚度等)对整车行驶平顺性、悬架导向机构对前轮定位参数及操纵稳定性的影响,以确定悬架系统各主要元件的设计要求。针对麦弗逊式悬架系统中的螺旋弹簧元件,在不等曲率弯曲螺旋弹簧理论设计研究的基础上,结合车辆系统动力学仿真和有限元分析,提出一种基于虚拟样机技术的优化设计方法,并进行了实例优化和试验验证。该方法采用自顶向下的设计思路,从提高整车平顺性和操纵稳定性、延长减振器使用寿命、降低弹簧元件生产成本等性能要求出发,提出悬架系统的性能要求;根据悬架系统性能要求,对悬架系统主要元件如弹簧、减振器等提出元件设计的性能要求;针对其中的弹簧元件,以中心线不等曲率弯曲螺旋弹簧代替原有的普通螺旋弹簧,在元件特性研究的基础上将传统的多目标优化和有限元仿真结合起来进行弹簧结构的优化设计,获得了期望的弹簧中心线方程和主要结构参数;弹簧试制后进行台架试验,获得的弹簧刚度特性引入到整车系统动力学模型中,仿真结果表明:减振器的侧载显著降低;弹簧试件装车后进行整车平顺性试验并与原系统试验数据进行对比,检验了优化设计结果对整车行驶平顺性的改善效果。不等曲率弯曲的螺旋弹簧可以有效解决麦弗逊悬架的侧载问题,然而,由于这种螺旋弹簧压缩过程十分复杂,其变形机理和刚度特性需要进行全面的研究。因此,本文在有限元分析软件ANSYS基础上二次开发了螺旋弹簧性能分析和结构设计软件包,研究了簧丝直径、弹簧中径、有效圈数、自由高度和弹簧细长比等主要结构参数对不等曲率弯曲螺旋弹簧性能的影响,在此基础上探讨其设计原则。采用ZwickZ050弹簧测力机,进行了5组不同结构参数的复杂结构螺旋弹簧性能试验,弹簧的垂向刚度特性和侧向力特性与仿真结果吻合较好,侧向力特性试验数据间的比较也验证了中心线不等曲率弯曲螺旋弹簧的设计原则。更多还原

【Abstract】 In the design of vehicle suspension system, the characteristics and their matching of important components, such as spring and damper, have crucial effects on suspension and vehicle behaviors. Due to their complicated relationships and influences with each other and the complexity of suspension system structure, variable loads and work conditions, the conventional physical-prototype-based design approaches has become difficult to accommodate with stricter design requirements. With the rapid developments of CAD/CAM/CAE technology, the validity and efficiency of virtual-prototype-based design approaches have been utilized in the design for more and more new CAR products. Therefore, taking widely used Macpherson suspension system as example, this dissertation performs the study on“Performance Analysis and Optimization Design for Suspension System Based on Virtual Prototype Technology”, which is sponsored by SAIC Technology Fund.Taking Santana2000 car model as example and sufficiently considering the nonlinear characteristics of springs, dampers, rubber bushings and bumper blocks, a detailed dynamics model for MacPherson suspension system is built using Multi-body system dynamics software, i.e. ADAMS, at first to perform kinematics and dynamics simulations. The simulation results are compared with experimental data for validating of the established suspension model. Then the side load of MacPherson suspension system is analyzed and the optimization target is proposed accordingly.Base on the established suspension model, the whole vehicle model is built to perform ride comfort analysis in sine sweep and random road surface imputs respectively, which is validated by body acceleration PSD test data. The effects of elastic and nonlinear component characteristics (including spring stiffness, shock absorber damper coefficient, bushing stiffness, etc.) and suspension linkage on suspension performances are studied to determine the requirements for individual system component design. Based on theoretical study of the curve spring, a virtual-prototype-based approach, combining vehicle system dynamics simulation with the Finite Element Analysis, is proposed and validated for the optimal design of suspension system with these complicated structure springs. Adopting top-down design philosophy, the designers decide suspension performances according to the requirements of vehicle ride comfort, shock absorber service life and spring manufacture cost, etc. Then the characteristic requirements for each component are obtained according to suspension performance requirements. Taking spring component as example, a coil spring with curved centerline is substituted for original conventional spring and the structure parameters and desired centerline function for the complicated structure spring are optimized. Then the spring samples are produced and tested accordingly so that spring stiffness characteristics can be introduced into system dynamics model. The simulation results show significant reduction in shock absorber’s side load, while the experimental data of vehicle body acceleration also indicate the improvement in ride comfort.It has been proved that this curve coil spring can reduce MacPherson suspension side load efficiently. However, due to its complicated compression process, the distortion mechanism and stiffness characteristics of this complicated spring need comprehensively studies. Therefore, base on FEA software ANSYS, a software package for coil spring characteristic analysis and structure design is developed. Using this design package, the effects of main structure parameters of the complicated spring, including wire diameter, mean diameter, available coils number, free length and slender ratio, can be investigated. Accordingly, the design principals for the springs with curve centerline are discussed. Five groups of the spring samples with different structure parameters are experimented on ZwickZ050 test rig. The vertical and lateral stiffness experimental data match well with the FEA simulation results and the comparisons between force incline angles validate the conclusions on the design principals of this complicated structure spring as well.更多还原