Vibration Isolation Performance Enhancement Using Hybrid Nonlinear Inerter and Negative Stiffness Based on Linkage Mechanism

Purpose: To suppress the low-frequency vibration of dynamic systems such as underwater vehicles, this research proposes a novel geometrically nonlinear vibration isolator using hybrid nonlinear inertial and negative stiffness element. Methods: A spring and an inerter are integrated together into a 4-rod linkage structure to form geometric nonlinearity. The performance of isolator under force or base-motion excitation is analysed. The performance of the proposed isolator in a flexible base structure simulating vibration isolation in ships is also considered. The transmissibilities and vibrational energy transfer are used to evaluate the effectiveness of isolation. Results: The results demonstrate better performance in low-frequency vibration isolation comparing to conventional linear isolator. The combined use of spring and inerter in the linkage mechanism can create a frequency band of ultra-low transmissibility and energy flow at low frequencies. Conclusion: Structural parameters of the proposed hybrid nonlinear element can be designed to alter the dynamic characteristic of the nonlinear isolator to attenuate low-frequency vibration transmission. The proposed nonlinear isolator demonstrates a strong potential for application in naval architecture.