Statistical Linearization Analysis of a Hydropneumatic Suspension System With Nonlinearity

Hydropneumatic suspension has the characteristics of nonlinear stiffness, nonlinear friction damping, and nonlinear hydraulic damping, and therefore, it has been widely applied to heavy vehicles. A hydropneumatic suspension with a special structure was proposed and studied in this paper. The nonlinear quarter-vehicle model was built by using Newton's laws according to its configuration. Then, this nonlinear mathematic model was linearized through the statistical linearization method on the basis of random vibration theory. Next, the transfer functions of the suspension system subjected to random road excitation were built according to the statistical linearization model and the power density spectrum approach. In addition, the responses of vehicle body acceleration, tire relative dynamic load, and suspension deflection with respect to the wideband random excitation due to road roughness were obtained according to the James formula. Next, the influences of the equivalent damping ratio and the equivalent frequency ratio on vehicle riding comfort, riding safety, handing stability, and suspension reliability were analyzed through simulations. These results provided the basic principles for selecting the reasonable hydropneumatic suspension parameters.