Design, Analysis, and Testing of a Metamaterial Vibration Isolator for Hydrophone Equipped on Autonomous Underwater Vehicles

The acoustic detection performance of hydrophones on the acoustic characteristics of targets is highly sensitive to external vibrations and noise interference. With the limitations of volume within autonomous underwater vehicles (AUVs) and highly corrosive ocean environments, the design of an embedded vibration isolator (VI) is needed so as to protect the hydrophones equipped on AUVs. To effectively isolate the low-frequency vibration produced by actuators on the AUV, such as the thruster, rudder, etc., this paper designs a VI for a hydrophone equipped on the AUV by using a metamaterial with quasi-zero stiffness (QZS) characteristics. This VI contains circumferential vibration-damping units, which improve the overall vibration damping effect through integration with the radial multi-stage damping layers. As a result, by utilising harmonic response analysis, the conformal design of eight circumferential units and two radial layers is optimised across all designs; its maximum vibration transmissibility is 56 dB at 500 Hz. Finally, the effectiveness of the QZS VI is verified through an experiment, which also shows a good match with the trend of the simulation results. This work also provides theoretical guidance for further study on the optimisation of phononic crystal mechanisms for vibration damping.