Quasi-zero stiffness suspension for reducing the resonance frequency of underwater electrodynamic transducers

To address the dual demands of high static load capacity and low resonance frequency in underwater electrodynamic transducers, this study introduces a nonlinear supporting mechanism based on a tension spring-roller-cam quasi-zero stiffness (QZS) structure. The mechanism effectively reduces the equivalent stiffness while maintaining high static load capacity, achieving lower resonance frequency and enhanced ultra-low-frequency vibration performance. A nonlinear dynamic model of the transducer is developed, and displacement and sound pressure level responses are analyzed using the harmonic balance method. Numerical simulations reveal the influence of mechanical damping and excitation amplitude on the system's vibration characteristics. Comparative analysis shows that the QZS-supported system exhibits a significantly lower resonance frequency and improved low-frequency vibration behavior than the conventional linear system. Experimental validation using impact hammer testing confirms a significant reduction in resonance frequency and enhanced acceleration response in the ultra-low-frequency range. These findings validate the capability of the proposed QZS suspension mechanism to achieve ultra-low resonance frequency, suggesting its potential for application in underwater ultra-low-frequency electrodynamic transducers.