| The suspension system is an assembly, which connects the automobile body and axle of the vehicle. It is composed of road, tyre, non-sprung mass, suspension, and sprung mass. The ride comfortability is decided by the quality of the suspension system. The hydro-pneumatic suspension gets popular using is just for its distinguished characteristic of shock absorbing. The hydro-pneumatic cylinder integrating the spring unit and shock absorber, which is a core component of the hydro-pneumatic suspension, which uses the hydraulic oil as the damping medium and uses the inert gases N2 as spring medium. It has been developed into the key technology of special vehicle and engineering vehicle for its excellent nonlinear stiffness and damping characteristics, which can meet the demands of vehicle at maximum level. This paper takes the hydro-pneumatic cylinder of one kind of dump truck as the studying object, which is a part of the project "Study on CAE technology for the parts and components of dump truck". The paper mainly studies on the back hydro-pneumatic cylinder based on test and establish thermo-mechanically numeric model about the output force characteristic of the hydro-pneumatic cylinder, which depending on the R-K equation and the hydrodynamics. After comparing the simulation results and the test ones, it shows that the numeric model is correct. Based on the numeric model built in this paper and combing the numeric model of output force of the front hydro-pneumatic cylinder, the paper build up a whole vehicle model and analyzed the results of the ride comfortability with different parameters of the front, back hydro-pneumatic cylinder, different velocities, wheel track and ambient temperature, which provide more reliable theory foundation to the designing of the hydro-pneumatic cylinder. This paper also attempts to establish the neural network model of the output force of the back hydro-pneumatic which makes a rewarding research about how to using neural network to establish the non-parameter model of the hydro-pneumatic cylinder. This paper mainly includes such contents: Chapter One: Introduction. In this chapter, the paper systematically introduced the vehicle suspensions. At the same time, the paper introduced the development of the hydro-pneumatic cylinder and its application in the world. The paper points out the excellent character of the hydro-pneumatic cylinder, and coming out the research contents of this paper. Chapter Two: Dynamic Character Simulation of Hydro-Pneumatic Cylinder. In this chapter, we established the nonlinear numeric model of the back hydro-pneumatic cylinder by the R-K equation and the hydrodynamics after introducing its working principle in detail. The simulating results are useful for designing the hydro-pneumatic cylinder Chapter Three: Dynamic Character Test of Hydro-Pneumatic Cylinder. Taking the back hydro-pneumatic cylinder as studying object, the paper carries out a test with the 200kN hydraulic servo test-bed of Jilin University. The testing contents include different agitating amplitudes, different agitating frequencies and different loads. And the paper also carries out a test about the reaction of the output force of the cylinder under different temperature. After comparing the simulation results with the test results, it can be shown that the numeric model built in this pater is correct, so it can correctly predict the output force characteristic of the hydro-pneumatic cylinder, so the model built in the paper is correct. Chapter Four: The Neural Network Model of the Hydro-Pneumatic Cylinder. In this chapter, we established the neural network model of the output force characteristic of the hydro-pneumatic cylinder using neural network method based on the results of the test, and trained the neural model with the test results. In order to test the generalization ability of the neural network model, the paper compared...
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