Abstract: According to vibration characteristics of a certain type of tractor,a kind of adjustable damping hydro-pneumatic suspension was put forward.Based on the analysis of working principle,the nonlinear mathematical model of suspension was set up,and the nonlinear damping characteristics were investigated using MATLAB/Simulink.The results showed that suspension damping has obvious non-linear characteristics.The indicator diagram and speed characteristics of suspension damping are greatly influenced by the fluctuation of the number and size of the damping hole.The flow area of variable throttle only changes the damping characteristics of return stroke,the effect on compression stroke is not obvious.The frequency and amplitude of external excitation have a marked impact on indicator diagram of suspension damping,but have no effect on the velocity characteristics.

Key words: vehicle engineering, hydro-pneumatic suspension, non-linear characteristics, indicator diagram, damping characteristics, simulation