【作者】 王雪婧；

【导师】 史文库；

【作者基本信息】 吉林大学 ， 车辆工程， 2011， 硕士

【摘要】 近年来由于道路条件的改善和大功率发动机、轻量化车身的应用,以及消费者对乘坐舒适性要求的提高,发动机振动引起的整车NVH问题愈发突出。因此,人们对发动机悬置元件隔振性能的要求不断提高。由于传统悬置元件很难在宽频段内满足复杂的理想隔振特性,半主动/主动发动机悬置应运而生,另一方面,智能材料的蓬勃发展也为发动机隔振技术提供了广阔的发展前景。本文研究的磁流变发动机悬置是磁流变液体与隔振技术的有机结合,属于典型半主动控制式液压悬置。磁流变悬置通过控制电流,改变悬置中外加磁场强度,进而改变磁流变液体的流动性来实现悬置动态特性的实时可控。本文分别对磁流变液体的磁流变效应、剪切屈服应力与流变性能进行介绍分析;设计一种磁流变发动机悬置结构,并建立其键合图模型、数学模型,对悬置动特性进行参数化研究;分别采用两种控制方法对二自由度发动机‐车架振动系统进行控制仿真,并对仿真数据进行对比研究。论文所做工作是针对磁流变悬置开发所进行的探索性研究,论文主要内容如下:首先论述发动机悬置理想隔振特性;回顾磁流变技术的发展历程与商业化应用,以及半主动控制策略的研究进展。分析磁流变液体的磁流变效应、剪切屈服应力与流变性能。随后,提出将磁流变液体应用到传统液压悬置隔振性能改进中的思想,分析磁流变悬置的工作原理与主要工作模式,推导流动工作模式下液体阻尼与电流变化的表达式,并且以某现有液压悬置为基础,在保持其橡胶主簧和金属支撑骨架不变的情况下,设计一种以磁流变液作为封入液体的液压悬置的结构。然后,在磁流变悬置液力模型的基础上运用键合图理论建立其键合图模型,推导其状态方程,并推导磁流变悬置动刚度和阻尼滞后角的频率变化特性表达式,应用Matlab编制程序对悬置低频动态特性进行仿真并进行参数化研究,着重分析电流强度对动态特性的影响。最后,考虑悬架等效刚度和等效阻尼,建立发动机‐车架的二自由度悬置系统模型,利用MATLAB/Simulink仿真模块建立仿真模型,分别运用模糊控制和模糊PID控制方法对悬置系统进行半主动控制仿真,得到各种工况下车架加速度和传递率的时域变化曲线,并与被动悬置系统进行对比分析,结果表明,采用适合的控制方法后磁流变悬置系统隔振性能得到较大的改进,且模糊PID控制方法控制效果较模糊控制方法更好。更多还原

【Abstract】 In recent years as a result of the improvement of road conditions and the application of high-power engine, lightweight body and consumer’s high demand for comfortableness, the NVH problems caused by engine vibration are becoming more and more serious. Therefore, the demand for isolation performance of engine mount is on an increase. Because the traditional engine mount cannot satisfy the complex characteristics of ideal vibration isolation within the broadband section, the semi-active/active engine mount emerges. On the other hand, the vigorous development of intelligent materials provid broad prospects for the vibration isolation technology.The semi-active MRF (Magneto-rheological Fluid) engine mount studied in this thesis is a combination of the magneto-rheological fluid and vibration isolation technology and belongs to a typical semi-active control mount. Intelligent control MRF engine mount can change the strength of applied magnetic field through controlling the current and then change the fluidity of MRF and finally realize theinstant controls of dynamic chatacteristics. This thesis analyzes the MR effect principle, yield shearing stress and mechanical characteristics of MRF; designs structure of a MRF and builds bond graph model and mathematic model to study characteristics of MRF mount; I also compare the isolation characteristics of two degree MRF mount using two different intelligent methods. This thesis is aiming to do the exploratory research of MRF engine mount’s development.The main contents are as follows:The first part is discussing the ideal vibration isolation characteristics of engine mount, reviewing the development and commercial applications of magneto-rheological fluid technology, and the semi-active control strategy and then analyzing the MR effect principle, yield shearing stress and mechanical characteristics of MRF. Then I propose the idea toapply magneto-rheological fluid to the performance improvement of traditional hydraulic mount and analyze the structure and working principle of typical MRF mount. An expression of liquid damping with the current change under the valve mode model is derived. After that, I design a MRF engine mount on the basis of existing hydraulic mount.In part three, bond graph modeling of MRF mount is built up based on its physical model. Frequency changing expression of MRF mount’s dynamic stiffness and damping lagging angle is deduced. Then I simulate the dynamic characteristics within low frequency using MATLAB and do the parametric research. Especially, the influence of current intensity upon dynamic characteristics is analyzed.At last, considering stiffness and damping of MRF mount and suspension, the two degree system mechanical model of engine and body is built, whose simulated model is constructed using Simulink module of MATLAB software. Then applying Fuzzy control and Fuzzy-PID control separately to control the MRF mount system and develops the force and acceleration time domain curves of body in different working conditions. After comparing with the passive engine mount, we find that the isolation effects are improved a lot under applicable methods, in which the Fuzzy-PID control method is better.更多还原