On the analysis of an actual model of a quasi-zero stiffness vibration isolator

Considering the practical situation where the mechanical springs are either compression springs or tension springs, an actual model of a quasi-zero stiffness vibration isolator (QZS-VI) is developed. The detachment between springs and isolated objects could occur when the external excitation is large, which leads to complex restoring force and stiffness characteristics. First, the restoring force and stiffness characteristics of an actual QZS-VI model are deduced. Then, the frequency response and isolation transmissibility are analyzed. At last, the actual QZS-VI model is compared with the corresponding ideal one. The results indicate that when large excitations are considered, the actual QZS-VI model exhibits lower resonance frequency and peak transmissibility than the ideal one and can avoid unbounded response. The frequency island phenomenon could occur under base excitation.