Abstract: An air spring dynamic stiffness model for passenger cars considering equivalent damping and hysteresis characteristics is proposed. The physical meaning and mathematical expression of each component in the model are given for precise control of air suspension system. Based on the analytical expressions of the model, a set of general methods for the identification of key nonlinear parameters such as the effective area equivalent stiffness, air chamber stiffness and equivalent damping are given. The indicator experiment is designed to identify each parameter item, and verify the correctness and feasibility of the dynamic stiffness model and the parameter identification method under large stroke (the maximum relative error of the model under long-stroke sinusoidal excitation is less than 0.5%, and the parameter identification error is less than 3%). Finally, based on the derived dynamic stiffness model, the influence of key parameters and their dynamic characteristics are analyzed. The results show that the hysteresis characteristic (phase angle) of a single-chamber air spring for passenger cars increases first and then decreases with increasing frequency. The greater the equivalent stiffness, the greater the phase angle peak value and the higher the corresponding frequency; the greater the equivalent damping, the phase angle peak value remains unchanged, and the corresponding frequency decreases. According to the theory and experiment, the frequency dependence and change law of the key nonlinear parameters of the air spring are pointed out, which provides guidance for the theoretical modeling and forward development of the air spring.

Key words: thermodynamics, hysteretic characteristics, parameter identification, dynamic characteristics