Design and experimental study of a two-stage nonlinear vibration isolators with quasi-zero stiffness

Abstract

Quasi-zero-stiffness (QZS) vibration isolators are practical solutions for isolation in the low-frequency range. However, single-layer QZS isolators have a low roll-off rate of transmissibility in the frequency band of isolation, especially at high frequencies. The purpose of this study is to design a novel two-stage QZS isolator, called TSQZS isolator. In each stage, the quasi-zero stiffness is achieved by combining magnetic rings and linear springs in parallel. The TSQZS isolator can support a wide range of payloads by adjusting the initial compression of the positive-stiffness element (coil spring). Firstly, an analytical model of magnetic spring is given by employing the theory of equivalent magnetic charge, and the parameters are designed using the finite element simulation. Then, the dynamic behaviors of the TSQZS isolation system are revealed by using the harmonic balance method, and the isolation performance is assessed by displacement transmissibility. Finally, an experimental prototype is fabricated and the experimental testing setup is established to verify the isolation performance of the TSQZS system under base excitation. The results demonstrate that the devised TSQZS isolator not only enables vibration isolation at low frequencies, but also gains a high roll-off rate of transmissibility in the frequency band of vibration isolation.