Nonlinear Low Frequency Response Research for a Vibration Isolator with Quasi-Zero Stiffness Characteristic

A vibration isolator system with nonlinear stiffness is designed and tested to solve problems on marine noise measuring equipment which are caused by underwater flow. The low frequency response characteristics of the vibration isolation system are evaluated from static function and dynamic simulation with Harmonic Balance Method. The theoretical analysis results show that the total stiffness value of the isolator system will be kept in 0 point around when parallel springs stay in equilibrium position. In order to assess the practical efficiency of Quasi-Zero-Stiffness (QZS) isolator, a vibration response test is carried out. By comparing the acceleration signals at 5 Hz and 100 Hz between linear and nonlinear system in time domain and frequency domain, the transmissibility curves are obtained. The experimental results demonstrate that the isolation system expands the frequency range of operation effectively by decreasing the natural frequency of the QZS vibration isolator. In addition, the QZS isolation system decreases the transmissibility of vibration by reducing the amplitude of output signals. The QZS isolator has more outstanding performance in contrast to linear spring in ultralow frequency isolation field.