Modeling of Air Spring Dynamical Characteristics using Fractional Derivative Model and Thermal Hysteresis

Air springs are one of the most common used groups of vibration isolators and their dynamical characteristics are extensively studied. One of the main challenges of modeling of air spring dynamical characteristics is to model for hysteresis characteristics of air spring. Hysteresis characteristics of air spring are contributed by friction and viscosity of rubber bellow and by thermal hysteresis of compressed air inside air spring. In this paper, dynamic behaviors of air spring are modeled and analyzed. Firstly, force versus displacement data are obtained by the tests under static, harmonic and random excitations. Secondly, a nonlinear model is presented to capture the measured air spring’s behaviors. The model is consisted of Berg’s friction and fractional derivative model to describe rubber bellow behaviors and heat exchange model to describe thermal hysteresis of air. Furthermore, the proposed model parameters are identified using finite element model and test data. Finally, the air spring hysteresis behaviors are analyzed based on the proposed model.