Dynamic frequency response characteristics of a compound regulative quasi-zero stiffness air spring system

Quasi-zero stiffness (QZS) device is widely studied for their better performance in low-frequency and micro-vibration isolation due to the high-static and low-dynamic (HSLD) stiffness characteristics. The previous QZS isolator with determined parameters is not suitable for variable isolated mass. In this study, a novel compound regulative quasi-zero stiffness air spring (CRQSAS) has been proposed and designed by introducing a bidirectional regulator for the horizontal air springs. The CRQSAS could change the quasi-zero region depending on the payload. To identify the parameters of the convoluted air spring (CAS) and novel rubber air spring (NRAS), the air spring testing system is established. The stiffness functions of air springs are obtained by the multi-parameter fitting method. According to the structure of the CRQSAS, the dynamic model of the system is analyzed and simplified by Taylor Expansion. The harmonic balance method (HBM) is applied to calculate the frequency response and absolute displacement transmissibility. An experimental prototype has been set up to verify the theoretical model and simulation. Compared with the single NRAS, CRQSAS performs better in low-frequency and micro-amplitude vibration. The research proves that CRQSAS is a passive device widely applied for improving isolation precision under low-frequency vibration.