节点文献
面向虚拟试车场（VPG）技术的路面模型系统研究
Research on Road Surface Model System Oriented to VPG Technique
【作者】 胡志刚；
【导师】 陈立平；
【作者基本信息】 华中科技大学 ， 机械设计及理论， 2011， 博士
【摘要】 基于对随机道路数值模拟方法和车辆—道路系统动力学的深入研究,构建了面向虚拟试车场(VPG)技术的路面模型系统平台。利用该平台可以实现对一维、二维和用于虚拟试验环境的3D数值路面进行重构,借助MSC.ADAMS、ANSYS/LS-DYNA等动力学分析软件,对不平度路面激励下车辆的动力学响应进行分析,并进一步比较分析了道路的柔性对车辆动力学响应的影响。基于随机道路不平度功率谱密度(PSD)函数、互功率谱密度函数和相干函数的表述,导出二维路面的PSD、自功率谱密度函数和相干函数表达式。介绍了随机道路时域数值表达的基本理论和方法,分析了几种不同的随机道路数值模拟算法,建立了一维道路时域模型,并对所建构的数值道路模型进行了仿真和验证。在一维随机道路数值模拟方法的基础上,推导了基于PSD的IFFT二维路面数值模拟方法。利用分数布朗运动(FBM)理论,基于小波变换方法对道路路面进行了二维数值模拟。根据图像处理和模式识别的理论方法,建立标准等级随机道路的图像数据库,基于路面图像匹配方法,对二维随机路面进行数值重构。采用IFFT方法对确定性路面与平稳随机路面进行叠加,从而建立了典型试验强化路面的二维数值模型。运用小波分析方法,对仿真路面模型的细节信号进行了二维小波分析。分析平直路面、弯曲路面、坡道路面、确定性强化试验路面等路面模型在VPG环境中的重构算法,重构的路面为车辆—路面交互仿真研究提供3D路面模型。建立了典型试验车辆的动力学模型,分别以重构的标准等级随机路面和确定性强化试验路面为输入激励,对车辆—路面系统进行了动力学仿真,得到了汽车的振动响应和动载荷时间历程,以及它们的PSD曲线。通过对仿真试验结果作进一步的后处理,从而对汽车的行驶平顺性进行评价,也为汽车结构疲劳寿命分析与预测仿真奠定基础。基于弹性层状空间理论和有限元分析方法,利用ANSYS/LS-DYNA动力学分析软件,建立了柔性轮胎—柔性道路的耦合动力学模型。通过仿真计算,得到行驶在各种不平度等级柔性道路上的汽车动力学响应,并与行驶在各种不平度等级刚性道路上的汽车(轮胎)动力学响应进行比较,讨论了道路的柔性与路面不平度对汽车行驶性能的影响。通过分析得出：柔性路面与车辆轮胎的柔-柔耦合对由路面不平度激励所引起的车辆振动响应具有抑制作用；对于低速行驶在低等级道路上的车辆,它的振动响应主要来自路面不平度激励,随着路面等级和车速的提高,由于道路的柔性而引起的路面应力应变激励逐渐成为影响车辆振动响应的主要因素。
【Abstract】 A road surface model system platform of VPG technique was constructed based on the deep research on random road numerical simulation method and vehicle-road system dynamics. By using the platform, it was achieved to regenerate 1-D,2-D and 3-D numerical road available for virtue testing environment; then the dynamic response of vehicle to the excitation caused by road irregularities was analyzed by means of MSC.ADAMS, ANSYS/LS-DYNA, etc.; and furthermore, a comparative analysis was made to discuss the influence of road flexibility on vehicle dynamic response.According to the PSD function of random road irregularities, cross-spectral density function and coherence function, a 2-D PSD expression, auto-spectral density and coherence function were deduced. Afterwards, an introduction was given to the fundamental theories and methods of numerical expression of random road in time domain and some different numerical algorithms were analyzed, then a 1-D road model in time domain was established, and numerical simulation and verification of numerical road surface model were accomplished.On the basis of numerical simulation method of 1-D random road, an EFFT 2-D numerical simulation method based on PSD was deduced. Then by the use of FBM theory and wavelet transform method, a 2-D numerical simulation was carried out for random road surface. Moreover, by means of image processing and pattern recognition theory, an image database of random road surface of standard grade was set up, and then the 2-D numerical road surface regeneration method and system model were established based on road surface image matching.IFFT method was used to carry out superposition of deterministic event and stationary stochastic road surface, then a 2-D numerical model of typical testing intensified road surface was built, and a 2-D wavelet analysis was conducted to process the detail signals of simulated road surface model by means of wavelet analytical method.The regeneration algorithms of straight road, winding road, ramp road, intensified deterministic testing road, etc. in VPG environment were analyzed so as to regenerate a 3-D road surface model which was used in vehicle-road system simulation. After that, a typical dynamic model of testing vehicle was built with a regenerated random road surface of standard grade and an intensified deterministic testing road surface as its input excitation respectively, and the dynamic simulation was carried out for vehicle-road system, then the vibration response and PSD spectrum analytical curve were obtained. According to the postprocessing curve data, the vehicle’s riding comfort was evaluated and the fatigue life of vehicle structure was analyzed and predicted.Based on the elastic layered space theory and finite element (FE) analysis method, a coupled dynamic model of flexible tyre-flexible road was established by means of ANSYS/LS-DYNA software. Through simulation and calculation, the dynamic responses of a vehicle running on the flexible roads of different irregularity grade were obtained and compared with those on the rigid roads, and then the influence of road flexibility and roughness on vehicle riding comfort performance was discussed.It was concluded that the flexible coupling of road surface and tire implemented a repressing on the vibration response of vehicles from the road excitation, and for high grading road the vibration rsponse of vehicles was mainly from the road surface flxibility, furtherly, with the decrease of the road grade, the excitation from road irregularities gradually became dominant in the contribution to the vehicle’s vibration response.