A semi-active electromagnetic quasi-zero-stiffness vibration isolator

Abstract

A semi-active electromagnetic quasi-zero-stiffness (QZS) vibration isolator (VI) (SEQZS VI) is proposed to broaden the frequency bandwidth for low or ultra-low frequency vibration isolation. The electromagnetic negative stiffness mechanism (NSM) applies a newly designed "8"-shaped electromagnetic equivalent magnetic circuit and has a more extensive tunable range of negative stiffness (NS) than previous studies. Moreover, theoretical formulations for the SEQZS VI in static and dynamic analyses under harmonic excitations were derived in detail and the parameter analysis is carried out to provide a reference for the design. Furthermore, a prototype is fabricated and tested to validate the design concept of SEQZS VI. The experimental results validate the present formulation and show that the vibration isolation performance of the proposed SEQZS VI is much better than that of the corresponding linear isolator. Moreover, the present SEQZS VI can have lower stiffness in a wider region and lower transmissibility at the resonance frequency.