Constant Quasi-zero Stiffness Ultra-low Frequency Vibration Isolator Design Based on Negative Stiffness Mechanism Composed of Oblique Bars and Tension Spring

Compared with linear vibration isolator, quasi-zero stiffness vibration isolator has excellent vibration isolation performance with wide frequency and low transmissibility, and it is a kind of passive vibration isolator with better application prospect. However,the quasi-zero stiffness isolator with a single static equilibrium point has problems in the variable bearing mass isolation and large excitation isolation. For solving the problems, a constant-value quasi-zero stiffness isolator is constructed by using the constant-value negative stiffness mechanism of oblique bars and tension springs. The parameter conditions of constant-value quasi-zero stiffness,non-constant-value quasi-zero stiffness and zero stiffness are derived, as well as the characteristics of quasi-zero stiffness and the law under the influence of the parameters are analyzed. The experimental model is then designed, manufactured and assembled according to the constant-value quasi-zero stiffness parameter conditions. The universal testing machine is used to obtain the force-displacement curves which corresponded well with theoretical predictions, providing verification for the static analysis theory. Subsequently, the Polytec laser vibrometer and the shaking table are used to collect dynamic experiments results on the experimental model with constant-value quasi-zero stiffness. The experimental transmissibility is consistent with theoretical predictions well. The isolator has the wide bandwidth with the starting isolation frequency of close to 1 Hz and low transmissibility amplitude.