An improved quasi-zero stiffness isolator with two pairs of oblique springs to increase isolation frequency band

Abstract

Quasi-zero stiffness (QZS) isolators can achieve superior performance in vibration isolation; however, this superiority is often effective only for an excitation with the small excitation amplitude due to the narrow QZS region around the static equilibrium positions. A QZS isolator with multi-pairs of oblique springs can increase the QZS region, but its isolation frequency band is still narrow owing to the large static deflection. This article presents an improved isolator with two pairs of oblique springs by setting an initial position to be located between the supporting points of the upper pair of oblique springs and the equilibrium position so that the static deflection is significantly decreased, and thus, the isolation frequency band can be considerably increased. New formulations of stiffness and displacement transmissibility are derived for the improved QZS isolator. A prototype is designed, fabricated and tested to verify benefits of the present QZS isolator for vibration mitigation. Numerical results of the present isolator predicted by experiment and theory are compared with those of the corresponding linear isolator and previous QZS isolator to show advantages of the innovated design for vibration isolation.