Research On Connected Hydro Pneumatic Suspension System

Connected hydro pneumatic suspension system(CHPSS) has the low inherent frequency and high antiroll ability, and is widely used in construction machinery and advanced cars. The research on CHPSS can provide some support for product design.In this paper, mathematic model of CHPSS is built, which contains hose damping. Based on the mathematic model, stiffness characteristics and damping characteristics are analyzed. The vertical linear stiffness will be reduced if the accumulator volume and gas precharged pressure are added, and will be added if the suspension mass is added. The rolling angular stiffness will be reduced if the accumulator volume and gas precharged pressure are added, and will be added if the distance of two cylinders, and area ratio of cylinder, and suspension mass are added, especially the area ratio, which has a very significant effect. The damping coefficient will be reduced if the diameters of orifice and hose are added. And the adding of check valve's diameter will also reduce the damping coefficient, but only for compression processing, not for rebound processing. For hose damping, when the diameter is added to some numerical value, the difference to damping coefficient is small, so the hose diameter should be reasonable chosen, not too thin or thick. If the hose diameter is reasonable, the hose length has a small effect on damping coefficient. The vibration processing of car body is analyzed and point that for the compression biggest velocity, there will be lots of fluid oils entering accumulator, so the accumulator has to meet this requirement, and there will be lots of fluid oils entering the cylinder's little chamber, so the check valve has to meet it. For the rebound biggest velocity, there will be lots of fluid oils discharging from cylinder's little chamber, so the orifice is hope big, but for suppressing the vibration the orifice is hope small. This paper advances to compute orifice's diameter by the equivalent damping ratio, and equivalent damping ratio is computed by the method of equivalent energy. At last, this paper points that if suspension mass is changed, the gas precharged pressure should be changed to keep the antiroll stiffness fixed, and if so, the inherent frequency and damping ratio can also be in reason. But if the relationship of ratio between gas precharged pressure and balance pressure is not suitable, we can change the accumulator volume by changing the oil circuit with the electric valve.In this paper, the characteristics of CHPSS are analyzed detailedly and a whole design method is prompted. The research results of this paper can provide help for the engineering application. So it has a significant meaning.