Abstract: For studying vehicle air suspension more accurately, the variant stiffness of air springs should be considered in the process of building dynamic models of vehicle suspension and simulation of the models. Based on the test data of dynamic characteristics of air spring, the numerical stiffness equations of air springs used in the air suspension of vehicle are obtained by means of nonlinear curve fitting according to the loads and equilibrium heights of air springs. In the beginning of every simulation step of discrete state space model of half vehicle, the value of air spring stiffness is changed and determined according to the dynamic deflection value of the suspension. In comparison with the experimental air spring pressures during the suspension step tests, the pressure difference between calculation and test is reduced greatly, which shows the effectiveness of the proposed method of dynamic characteristics fitting of air spring and nonlinear simulation of suspension models.

Key words: Air spring, Air suspension, Curve fitting, Simulation, Stiffness, Vehicle