基于动力总成悬置系统优化与仿真的车内噪声分析

发布时间：2018-09-09 18:51

【摘要】：随着社会的发展,消费者对于汽车品质的要求愈加苛刻,良好的NVH性能也就显得愈加重要。过多的振动和噪声不仅影响乘坐舒适性,还会分散驾驶员注意力,减少零部件的寿命,影响行驶安全性。发动机振动是整车振动噪声的重要来源。这一激励经由动力总成悬置系统传递到车架和车身,引起驾驶室内的振动和噪声。为了减小传递到车架和车身的振动,动力总成悬置系统的隔振性能显得尤为重要。新兴的主动、半主动液压悬置具有十分优越的隔振性能,但是成本较高。对于传统的橡胶悬置和被动式液压悬置来说,元件合理的布置与参数匹配都能影响悬置系统的隔振性能,主要体现在固有频率的分布是否合理以及解耦性能的优劣。本文结合某国产轻型卡车的NVH性能正向开发项目,通过改变悬置元件的刚度和安装角度,优化了动力总成悬置系统的解耦性能,并对优化结果进行了验证。主要研究内容如下所示:1.在理论准备上,推导了发动机振动产生的机理和悬置隔振的原理,阐述了动力总成悬置系统的作用、布置要求以及布置方式。提出了解耦的概念,介绍了几种主流的解耦方式。2.对动力总成后悬置的V形支架进行了锤击试验,得到了固有频率和相应的动刚度,验证了其性能的可靠,简化了建模程序。对动力总成悬置系统进行了模态试验,得到了六阶模态的固有频率和振型,作为后续工作中判断模型准确与否的依据。3.将动力总成简化为空间六自由度刚体,忽略悬置元件的扭簧作用,建立动力总成悬置系统的力学模型,推导出固有频率和解耦率的具体计算公式,并用MATLAB进行了计算。将计算得到的固有频率和试验结果对比,验证了力学模型的准确性,计算得到的解耦率是可信的。4.以前、后悬置的三向刚度和安装角度共8个参数为变量,应用MATLAB中的优化函数对悬置系统进行了优化。在保证Bounce运动解耦率接近80%的前提下,使Roll运动解耦率超过了90%。5.在ADAMS中建立动力总成悬置系统的模型,以仿真、试验和MATLAB计算得到的固有频率相对比,验证了模型的准确性。通过怠速工况仿真分析,优化后悬置的垂向响应力有所减小,说明优化方案有效。6.依据优化方案,对试验车进行改造,测量改造前后试验车在怠速、匀速以及加速工况下的车内噪声水平。根据试验结果,车辆改造后二阶、四阶频率处噪声峰值明显下降,说明本文提出的解耦理论和优化方案有效。
[Abstract]:With the development of society, consumers are demanding for automobile quality, and good NVH performance is becoming more and more important. Excessive vibration and noise not only affect ride comfort, but also distract driver's attention, reduce the life of parts and affect driving safety. Engine vibration is an important source of vehicle vibration and noise. This excitation is transmitted to the frame and body through the powertrain mount system, which causes vibration and noise in the cab. In order to reduce the vibration transmitted to the frame and body, the vibration isolation performance of the powertrain mount system is particularly important. Emerging active, semi-active hydraulic mounting has excellent vibration isolation performance, but the cost is high. For the traditional rubber mounting and passive hydraulic mounting, the reasonable arrangement of the components and the matching of the parameters can affect the isolation performance of the mounting system, mainly reflected in whether the distribution of the natural frequency is reasonable and whether the decoupling performance is good or bad. In this paper, the decoupling performance of the powertrain mounting system is optimized by changing the stiffness and mounting angle of the mounting elements, and the optimization results are verified by combining the NVH performance forward development project of a domestic light truck. The main contents of the study are as follows: 1: 1. In theory preparation, the mechanism of engine vibration and the principle of mounting vibration isolation are deduced, and the function, arrangement requirement and layout mode of powertrain mount system are expounded. This paper puts forward the concept of decoupling, and introduces several main decoupling methods. The hammering test was carried out on the V-shaped bracket mounted after the powertrain, the natural frequency and the corresponding dynamic stiffness were obtained, the reliability of its performance was verified, and the modeling program was simplified. The natural frequency and mode shape of the sixth order mode are obtained by the modal test of the powertrain mount system, which is used as the basis for judging the model in the following work. The dynamic assembly is simplified as a rigid body with six degrees of freedom in space, and the torsion spring of the mounting element is ignored. The mechanical model of the mounting system of the assembly is established, and the concrete calculation formulas of natural frequency and decoupling rate are deduced and calculated by MATLAB. The accuracy of the mechanical model is verified by comparing the calculated natural frequency with the experimental results. The calculated decoupling rate is credible. 4. In the past, the three-way stiffness and installation angle of the rear mount were used as variables, and the optimization function in MATLAB was used to optimize the mounting system. On the premise that the decoupling rate of Bounce motion is close to 80%, the decoupling rate of Roll motion is more than 90. 5. The model of powertrain mount system is established in ADAMS, and the accuracy of the model is verified by comparing the natural frequency obtained by simulation, experiment and MATLAB calculation. Through the simulation analysis of idle condition, the vertical response force of the suspension is reduced after optimization, which shows that the optimized scheme is effective. 6. According to the optimization scheme, the test car was reformed to measure the noise level of the test car in idle speed, uniform speed and acceleration condition before and after the revamping. According to the experimental results, the noise peak at the second order and the fourth order frequency of the vehicle is obviously decreased after the vehicle is reformed, which shows that the decoupling theory and the optimization scheme proposed in this paper are effective.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U464.13

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