Design and characteristics of low-frequency nonlinear floating raft vibration isolation device

Low frequency vibration and noise affects acoustic stealth performance of underwater equipment. Here, based on the original airbag vibration isolation device, improving structural design, lateral airbag could provide negative stiffness to the system, through parallel connection with vertical airbag, a new type nonlinear floating raft vibration isolation device was designed to enhance its low-frequency vibration isolation ability. The new type vibration isolation device was composed of a nonlinear isolator set of "lateral airbag-universal joint-vertical airbag" and a floating raft. The principle of lateral airbag to provide negative stiffness to the system was analyzed to establish a 6DOF dynamic model of the new device. Its prototype was designed to conduct relevant performance tests. Theoretical analysis and test results showed that the vertical first-order natural frequency of the new nonlinear floating raft vibration isolation system is about 50% of that of the original system, its vertical vibration isolation performance is improved by about 6 dB; its lateral vibration isolation performance is comparable to that of the original system; the rolling stability of the new system can be better under heavy load. © 2024 Chinese Vibration Engineering Society. All rights reserved.