Modeling of hydro-pneumatic suspension system with fractional order terms and simulation analysis of road friendliness

To establish the hydro-pneumatic suspension model more accurately and better analyze the influence of heavy vehicle hydro-pneumatic suspension system on road friendliness, the fractional order theory is applied to modeling, and the mathematical model and dynamics model of dual-chamber hydro-pneumatic suspension with fractional order are established by using Matlab/Simulink, and the fractional order differential term of the suspension system is calculated according to the improved Oustaloup filter. The effect of fractional order on suspension stiffness, damping and output forces is also investigated. The optimal fractional order is determined to be 0.9 for the design of a combined suspension performance index function. The vibration law of increasing amplitude and error of fractional-order is obtained through simulation, and the model with fractional-order is described more accurately. A sliding film variable structure controller was established for control. The simulation results were analyzed by means of theoretical road damage factors and dynamic load factors. The results show that the suspension system model with fractional order terms can effectively reduce the dynamic tire load and improve the suspension smoothness and road friendliness.