Dynamic performance analysis of a mixed-connected inerter-based quasi-zero stiffness vibration isolator

An inerter-based quasi-zero stiffness (IQZS) vibration isolator is proposed to further enhance the dynamic performance of the QZS one. It combines the superior nonlinear stiffness characteristic of the QZS vibration isolator and the beneficial mass magnification effect of the inerter. The diamond-shaped structure is used as the negative stiffness structure; an additional spring is added together with the inerter and damper to construct a novel IQZS vibration isolator, which the inerter and damper are first parallel connected and then series connected with the additional spring; it is a mixed-connected (MC) type and termed as MC-IQZS vibration isolator. The dynamic response of MC-IQZS vibration isolator is acquired via harmonic balance method (HBM), and the isolation performance is evaluated using four performance criteria. The effects of the inerter and additional spring on its dynamic response and isolation performance are examined. The results show that the MC-IQZS vibration isolator could have smaller displacement amplitude and force transmissibility peaks, wider isolation frequency band, and faster high-frequency force transmissibility attenuation rate than the QZS one, and it can improve the four performance criteria simultaneously. Its isolation performance is further compared with another two typical types of IQZS vibration isolators where the inerter and damper are in parallel-connected (PC) and series-connected (SC), respectively, and they are denoted as PC-IQZS and SC-IQZS vibration isolators, respectively. The results demonstrate that the proposed MC-IQZS vibration isolator could achieve the best isolation performance among the three IQZS ones, which offers an effective option for excellent vibration suppression in practical engineering.