【作者】 李未；

【导师】 王登峰；

【作者基本信息】 吉林大学 ， 车辆工程， 2012， 博士

【摘要】 随着国民经济的快速发展和人们生活水平的不断提高，人们在不断追求汽车安全、节能和环保性能的同时，对汽车行驶平顺性的要求也越来越高，汽车的行驶平顺性已经成为自主品牌轿车在市场竞争中取得优势的重要指标之一。在汽车新产品开发和量产车型平顺性改进中，都需要对影响整车行驶平顺性的主要传递路径进行识别、分析与评价，并据此提出行之有效的减振措施，来提高整车行驶平顺性，使其满足设计目标要求，这是提高汽车产品市场竞争力中不可缺少的重要环节。但是物理样车传递路径分析试验周期长、成本高，需要在物理样机研制出来之后才能进行。如何在产品设计阶段就能对影响轿车行驶平顺性的主要传递路径进行准确地分析和识别，从而对整车行驶平顺性进行预测和评价，缩短产品研发周期、降低研发成本，已成为我国自主品牌轿车在市场竞争中取胜的关键。本文的研究结合产学研合作项目《轿车中低频舒适性研究开发》，对轿车行驶平顺性的传递路径分析方法进行了系统、深入研究，并通过主要传递路径减振性能优化来改善轿车的行驶平顺性。本文根据所研究车型的特点，建立了以动力总成、前悬架、后悬架到驾驶员座椅地板的整车振动传递路径分析模型。在B级路面上进行了实车道路试验，分析了该车的行驶平顺性。结果表明，该车驾驶员座椅地板处的三向与总加权加速度均方根值随车速提高而逐渐增加。以50km/h、80km/h和120km/h三种典型车速为例，进行了该车平顺性的试验传递路径分析（Test TPA）方法研究。对驾驶员座椅地板垂直振动加速度频谱的峰值频率进行了TPA计算，得到整车各传递路径对目标点的振动贡献量。为了避免只考虑幅值大小而错误降低了对目标点振动有抵消作用的传递路径幅值，本文提出了一种综合考虑幅值与相位的评价传递路径贡献量的方法。结果表明，在三种典型车速下，该车各传递路径对驾驶员座椅地板Z向的振动中，动力总成右悬置Z向与X向的振动贡献量最大，其次是前悬架下控制臂前点Z向振动，再次就是后悬架下控制臂支臂Z向以及后悬架纵臂Y向。为了克服试验TPA中试验工作量大、个别路径频响函数因结构限制而难以敲击或激振、以及无法在产品研发初级阶段物理样机研制出来以前进行传递路径分析的不足，本文提出了一种平顺性的虚拟传递路径分析（Virtual TPA）方法。利用有限元和虚拟样机技术建立了整车刚弹耦合模型，在B级路面上进行了行驶平顺性仿真分析，并与实车试验结果进行了对比，验证了整车虚拟样机模型的正确性。采用与试验TPA同样的方法，完成了虚拟传递路径分析，综合考虑幅值与相位后识别出主要的振动传递路径。将试验TPA与虚拟TPA的结果在传递路径总贡献量以及传递路径识别结果两方面进行对比。结果表明，得到的主要传递路径识别结果一致，动力总成、前后悬架各传递路径总贡献量峰值频率和幅值的最大相对误差在13%以内，验证了所提出虚拟TPA方法的有效性。为了解决由于试验条件有限或者轿车本身结构限制而导致的传递路径丢失问题，避免拆卸发动机等复杂的试验工作，本文又提出了混合传递路径分析（Hybrid TPA）方法。该方法将所缺失的传递路径数据利用虚拟样机分析数据进行补充，建立完整的整车混合传递路径分析模型，进而将混合TPA与试验TPA的传递路径识别结果进行对比。结果表明，除了由于试验限制而缺失的前悬架上控制臂后点Z向，利用混合TPA得到的结果是对目标点的振动起加强作用外，其余各主要传递路径的识别结果是一致的。为了消除路面随机振动对前后悬架的相干影响，对悬架总成进行主分量分析后再进行了混合传递路径分析。将悬架总成利用混合TPA与试验TPA中前悬架、后悬架单独分析两种方法获得的结果相比较，说明对驾驶员座椅地板振动的主要路径识别结果是一致的，进一步说明了前悬架上控制臂后点Z向对目标点的振动贡献量是不可忽视的。针对识别出来的问题路径，进行动力总成悬置隔振率和悬架衬套传递特性分析，确定动力总成右悬置的隔振率较差，应针对右悬置的隔振特性进行优化；前悬架弹簧上点Z向、后悬架纵臂Y向对目标点的振动受其与目标点之间的频响函数影响较大，应该针对车身结构进行优化；前悬架上控制臂后点Z向、前悬架下控制臂前点Z向、后悬架下控制臂支臂Z向对目标点的振动主要是由路径点的工作载荷引起，应针对衬套传递特性进行优化，以达到提高整车平顺性的目的。最后，针对前文中传递路径分析识别出问题路径上减振元件的动力学参数，进行基于TPA方法的平顺性优化分析。以驾驶员座椅地板的垂直振动加速度最小为优化目标，以悬置和衬套的刚度为设计变量，进行整车环境下的传递路径优化，最后利用优化后的悬置和衬套的刚度，进行整车行驶平顺性仿真分析。结果表明，优化后整车平顺性有所改善，验证了优化结果的有效性。更多还原

【Abstract】 With the rapid development of the national economy and the people’s living standards,while automotive safety, energy saving and environment protection are pursued constantly,the requirements on the vehicle driving performance are also getting higher, vehicle drivingperformance has become an important indicator of the advantages of local brands cars inthe market competition. During the new model development and the driving performanceimprovement of the vehicles which is already in mass production, the identification, analysisand evaluation of the main transfer path which affect the car’s driving performance shouldbe accomplished, and accordingly the effective vibration reduction measures can beproposed to improve driving performance and meet the design requirements, that’s one of thekey factors to improve the vehicle capability for market competition. However, the testing oftransfer path analysis has long cycles and high costs, and only after the prototype car isavailable, the tests can be performed. Therefore, how to analyze and exactly identify themain transfer path which affects the driving performance during the vehicle design stage,and then the driving performance can be predicted, to shorten the optimization duration andreduce development cost, it has become an important key to succeed on the market for eachOEMs.This research is completed based on“The research and development of vehicle drivingcomfort in low frequency”, which is a project of industry-university joint research. Thepaper aims to analyze the method of transfer pass analysis on vehicle driving performancesystematically and deeply, and then the vibration reduction performances of the maintransfer path are optimized to ameliorate vehicle’s driving comfort.According to characteristics of the car analyzed in this paper, all TPA models of wholecar, from powertrain, front suspension and rear suspension to driver’s floor are built. Thevehicle test on B lever road is performed to study the car’s driving performance. The results show that, with the speed increase, the three dimensional and overall weighted accelerationRMS values of the driver’s floor increased gradually. Take speeds of50km/h、80km/h and120km/h for examples, the methods of test transfer paths analysis (test TPA) on drivingperformance is researched. Under three typical conditions, TPA calculation that based onpeaks frequency of the spectrum of driver’s floor is finished and each total contributionwhich originated from all transfer paths to target is obtained. A comprehensive method,considering both the amplitude and phase, is proposed for evaluating path contribution. Theresults show that, under the condition of these three typical speeds, the Z-direction andX-direction vibrations of the powertrain right mount has the greatest contribution to thez-direction vibration of the driver’s floor in all of the transfer paths, followed by theZ-direction vibration of the front point of the front suspension lower control arm, theZ-direction and Y-direction vibrations of the rear suspension lower control arm.Based on the following issues, the virtual transfer path analysis (Virtual TPA) method ofdriving comfort is presented to overcome these issues: firstly, heavy testing workload of thetest TPA; secondly, it is hard to get frequency response functions of some individual pathsdue to structural constraints which is difficult to knock and excitation; third, the transfer pathanalysis cannot be developed in the product development stage. To utilize finite elementmethod and virtual prototype technology, the rigid-flexible coupling model is set up. Thendriving comfort simulation on B-lever road is analyzed, and compared with the results of thetesting, to verify the correctness of the vehicle virtual prototype model. Using the sameanalysis method with test TPA, the virtual TPA is completed，and considering both theamplitude and phase, the main transfer paths which impact driving performance areidentified. According to the total path contribution and transfer path recognition results,results of test TPA and virtual TPA are compared. The results show that, consequences ofdriving performance transfer path analysis result obtained by these two analysis methods isthe same, and the maximum relative error of peak frequency and amplitude, which is aboutthe total contribution of the powertrain, front and rear suspension， is less than13%Then,the validity of the virtual TPA method is verified. So in order to solve the problems of transfer path lost caused by testing conditionlimitations and vehicle structure limitations, and to avoid some complex test work likedisassemble engine，a new hybrid transfer path analysis method is presented. Using the dataobtained from the virtual prototype analysis, the data of missed transfer path is supplied, andthe complete vehicle model of hybrid transfer path analysis is established, furthermore,results of test TPA and hybrid TPA are compared according the results of transfer pathidentification. Except for the transfer path, front suspension up control arm Z-direction,which didn’t get in test TPA due to the structure limitation, it has a lager contribution totarget; meanwhile, other main transfer paths are the same by means of these two methods.So as to eliminate the coherent effects between front and rear suspension because ofroad random vibration, the hybrid TPA result of suspension is calculated after principalcomponents analysis. The results of suspension assembly, which is from the method ofhybrid TPA and test TPA, are compared. It explains that the recognition result of maintransfer path is consistent, and the result shows again that the importance of the path, frontsuspension up control arm Z direction can not be ignored.According to problem paths obtained from hybrid TPA, characteristics of enginemountings and suspension bushings were analyzed. The results show that, to improve thedriving perferfomance, some measures should be implemented. First one is, the vibrationisolation ratio of powertrain right mount is bad and its characteristic should be making better.Second one, the frequency response functions, which are between the target and frontsuspension spring Z-direction, rear suspension trailing arm Z-direction, have influences totarget, so the structure of body should be optimized. Last is, the vibration of target is causedby the operation force of the rear point of front suspension upper control arm Z-direction, thefront point of front suspension lower control arm Z-direction, and the rear suspension lateralZ-direction, so the suspension bushing characteristic should be meliorate.For vehicle dynamic parameters of the vibration damping components, which areidentified in transfer path analysis, the optimization analysis of driving performance basedon TPA method is processed. Taking the driver’s floor vertical vibration acceleration minimum as optimization objective, and the stiffness of mount and bushing as designvariables, the optimization analysis of transfer path based on vehicle is processed. Finally,using the optimized stiffness of mount and bushing, the driving performance simulation testsare verified. The results show that, with the improved parameters, this vehicle’s drivingperformance is significantly improved, and the optimization results are also verified.更多还原