Isolation Performance of the Quasi-Zero Stiffness Isolation System Enhanced by Mixed Tuned Inerter Damper

The low-frequency isolation performance of the transverse spring-rocker quasi-zero stiffness (QZS) isolation system has been demonstrated. However, the QZS isolation system could encounter a deterioration of the low-frequency isolation performance under strong external excitation, due to the hardening phenomenon of its amplitude-frequency response (AFR). To end this problem, a mixed tuned inerter damper (MTID) which combines the advantages of the tuned inerter damper (TID) and the tuned viscous mass damper (TVMD) is proposed in this research. The analytical solution of the AFR of the MTID-QZS isolation system under harmonic excitation is solved by the harmonic balance method (HBM) and verified by numerical method. Whereafter, the corresponding stability analysis of AFR is conducted, and the force transmissibility (FT) of the MTID-QZS is defined to qualify the isolation performance. The effects of the tuning frequency of MTID, the inertance-to-mass ratio, and damping ratios on AFR and FT are conducted, and optimized parameter combinations are suggested to obtain distinguished ultra-low-frequency isolation performance. The comparison among the MTID-QZS system, TID-QZS system, TVMD-QZS system, and QZS system shows that the MTID-QZS system has obvious advantages in suppressing the low-frequency and high-frequency vibration either under strong or weak external excitation.