| Highway construction accelerated the progress of vehicle transportation dramatically. As a main means of delivery, commercial truck is developing aiming at heavy loading, high speed, more comfortable, and luxury. In order to adapt the improved requirement of domestic heavy-duty trucks, truck manufacturers have put more and more energy on the comfort performance of their truck cabs.Comfort is a main performance index for modern vehicle. There are two main factors that cause vehicle vibration, one is the random exciting caused by road irregularities while the truck is running; another is the vibration exciting caused by engine assembly while working. In regard to the causations of vibration and its transfer routes, researchers have made great efforts to reduce as much as possible the impact of vibration on smoothness and comfort performance of a vehicle. Cab mount system acts an important role in isolating the vibration that transferred from chassis to cab. Therefore, to enhance the isolation ability of cab mount is a sufficient mean for improving the comfort performance of cab when vibrating. For the air springs compared with the other elastic parts have many advantages. The most of mainstream heavy-duty truck cab mount systems in abroad have adopted air springs as the elastic parts. How to design the air springs which are used in the cab mount systems so that vibration spreading from frame to cab can be availably isolated has become an important task of the vehicle design. In addition, it is also a key point for the improvement of cab mount system ability, that elastic parts match damping part nicely. In this paper, based on a lot of references about the cab mount system, the air spring used in cab mount system is deeply researched by the way of that computer virtual technique combines with experiment, the Performance of Vibration Absorption of the elastic element and damping components of the vibration cab mounting system is also evaluated, and the damper on the cab is also optimized by the methods to optimizationCombined with projects that the research development of cab mount system used in changing generation truck of a company, this paper studies air spring cab mount deeply in both theory and test. The paper is divided into five chapters:Chapter one: Based on a lot of references, introduce the commercial driver's suspension briefly, including The definition of it , the development history and status quo of cab at home and abroad, how to dispose the cab (Including floating and semi-floating)and the characteristics of elastic parts used in cab mount(including rubber springs, coil spring, spring rubber compound, rubber damping pads, hydraulic suspension components, air spring ),and then make a brief introduction about Content and significance of researchChapter two: Test of air springs is introduced. The objects in those tests are rear and front air spring used in the cab suspension system; the tests include the test of Dynamic stiffness and Stiffness of both rear and front air springs and the test of damping of front air spring. In this chapter, we introduce the theory of air spring firstly, and then, we introduce those tests separately, including their methods, theory, contents. At last, we analyze the result of those tests and attain the curve of Dynamic stiffness and Stiffness of both rear and front air springs and the curve of damping of rear springs.Chapter three: We introduce the development of multi-body dynamics theory, the characteristics and modules of ADAMS briefly, and then, we introduce the process of modeling. Importing the CATIA model in ADAMS. Making some predilections of the model, Making the definition of joint points, Amending mass properties of the model of commercial vehicle cab, Adding constraints , Validating the model. At last, importing the curve of Dynamic stiffness and Stiffness of both rear and front air springs and the curve damping of rear springs to model commercial vehicle cab air suspension system.Chapter four: Establish the cab suspension model for vibration analysis based on the ADAMS dynamic stiffness and the static stiffness test results, First imposed a sinusoidal displacement excitation of 4mm amplitude on the frame cancroids ,then establish an output channel on the cab cancroids for it is displacement. With the indicators of transmissibility to analysis each damping performance . Compare the results of analysis it can be found that the two transmission power curve basically coincidence except only a little deviation on the maximum transmission point. The maximum occurred at the frequency of 2.2973 in the stiffness analysis with the transmissibility equal to 1.1599. Otherwise in the dynamic analysis it appears in the 2.7 ~ 2.9HZ with the maximum transmissibility of 1.222. However, the difference of the two maximum transmissibility no more than 10%, the result can be regarded as accurate. When it is for high-frequency analysis, the two power curve basically coincidence. Therefore, establish model based on the static stiffness curve and then use the model to analyze the dynamic is feasible. After verified the feasibility of the model, we can make analysis of the former air suspension in order to optimize it is damping based on this model. The left damping can defined as DV-1, whereas the right DV-2, take the maximum transmissibility of the cab suspension as it is objective function. After optimization, the left damping value from the 4 Ns / mm into 4.72 N-Sec/mm, where the right from 4 Ns / mm into 4.9266 N-Sec/mm, the transmissibility dropped to 1.1511 from 1.1559 after optimization ,at the same time , the resonance frequency from 2.2973 to 2.331, a slight increase. The difference of the two damping mainly because of the cab is not an entirely symmetrical structure. However, if define the left and right damping respectively and differently, it will take a great deal of inconvenience to the practical application, as well as to the products universal. Therefore, the same value of the damping is recommended.Chapter five: summarize the paper and give some advices.The meaning of this thesis is as follow, First of all, importing the test data in ADAMS to model and analysis commercial vehicle cab air suspension system .learning the process of using test data to model simulation model which is helpful to other people who devote on this object. And then , analysis the model based on the curve of Dynamic stiffness and Stiffness of both rear and front air springs ,and making a confrontation about the results, which prove that using the model based the curve of and Stiffness to do dynamic analysis is feasible. At last, we attain suitable damper by optimizing the model based the curve of and Stiffness, which guides the actual development of commercial vehicle cab air suspension system and is helpful to other people who commit themselves on this object. |
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