A novel high-static-low-dynamic-stiffness isolator with sliding mass: modeling and analysis

The dynamic response of high-static-low-dynamic-stiffness (HSLDS) isolators often exhibits a pronounced rightward bend under large excitation and low damping, significantly reducing the effective isolation region. Aiming at such a problem, a novel isolator is proposed in this study by combining the HSLDS characteristic with the sliding mass inertia (SMI). The isolator comprises a negative stiffness structure and two specially introduced masses that can move freely in the horizontal direction. The working principle of the newly proposed isolator is introduced, and the nonlinear dynamic equation of motion of the corresponding system is derived using the Lagrange principle. A Taylor series expansion is then conducted to derive an approximated equation of motion, and the effect of the SMI and HSLDS are clarified through a parametric study in terms of the equivalent mass, equivalent stiffness force and resonance frequency. The harmonic balance method is employed to the approximated equation for the steady-state displacement transmissibility in the frequency domain under base excitation. The isolation performance and the effects of design parameters are evaluated, and validated through simulations in ADAMS along with comparisons to two counterparts. The results reveal that the coupling between the sliding mass and the HSLDS mechanism significantly shifts the transmissibility peak towards the lower left region. This coupling can completely eliminate the hardening in the dynamic response under low damping and high amplitude of excitations, and thus increase the stability of the overall system. Moreover, the anti-resonance induced by the sliding mass enhances the vibration isolation effect in the low-frequency region. These advantages imply potential application to vibration isolation in various engineering.