| The hydro-pneumatic suspension technology having developed since 1960 is a new type of suspension technology that combines hydraulic transmission and control technology with suspension technology, which makes the hydro-pneumatic suspension have not only performances of traditional passive suspension, but also comprehensive performances of slow active suspension. With inert gases N2 as spring and oil as force translation medium, Hydro-pneumatic Suspension integrating the spring unit and shock absorber is a new type passive suspension system. It has been developed into the key technology of special vehicle and engineering vehicle because it's excellent nonlinear stiffness and damping characteristics can meet the demands of vehicle at maximum level. As a main component, the hydro-pneumatic cylinder's dynamic working characteristics directly affect the compliance of the hydro-pneumatic suspension vehicle. So studying the performance of the hydro-pneumatic suspension from component to system, and mastering its key parameters design rules have great meaning for developing engineering vehicle of our country. This paper takes one kind of crane as an example and establishes the physical model of hydro-pneumatic cylinder through properly simplifying its practical structure according to its working elements on the basis of analysis of its structure form and working principles. On the basis of the model, the paper studies the force-displacement characteristics, force-velocity characteristics and nonlinear stiffness and damping characteristics, discovers the affection disciplines of parameters such as excitation parameters, and working parameters on characteristics of hydro-pneumatic cylinder. This paper mainly includes such contents as follows: Chapter one: Introduction. On the base of referring to a great deal of external and internal information on hydro-pneumatic suspension technology, This chapter summarizes its development history, research status and main application field etc. and illustrates it is one of the main study direction of vehicle suspension today. On the base of analyzing fore-researcher's investigation work, puts forward the question needed to be studied more, and show the main study contents of the paper. Chapter two and three: the working principle of hydro-pneumatic suspension cylinder and the theory modeling of hydro-pneumatic suspension cylinder. The two chapters belong to the theoretical study on the performance of hydro-pneumatic suspension cylinder. The paper selects a kind of crane with hydro-pneumatic suspension as study sample, introduces its fix structure and working elements, establishes the physical model through simplify the real structure, and researches the working parameters which include damping orifice check valve Gas-Charged Accumulator on the theory. Chapter four and five: The modeling and simulation analysis of dynamic characteristics of hydro-pneumatic suspension cylinder and the research of the stiffness and damping characteristics of the hydro-pneumatic suspension. By using the computer software ADAMS/view,the paper sets up the modeling of the hydro-pneumatic suspension cylinder. On the base of the parameter model of hydro-pneumatic suspension cylinder established in ADAMS/view, simulates the work characteristics and the change law of internal parameters such as under the external sine excitation. The two chapters put forward using displacement-force and velocity-force to describe the dynamic characteristics of the hydro-pneumatic suspension cylinder, and simulate the affection of the working parameters such as damping orifice diameter initial gas pressure and volume on the dynamic characteristics of the hydro-pneumatic suspension cylinder, and study the affection of the working parameters on the stiffness and damping characteristics. All of these can be treated as the theoretical base to select the parameters and design the hydro-pneumatic suspension cylinder. And then the paper researches the stiffness and damping characteristic of the hydro-pneumatic suspension cylinder.
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