Bioinspired frog adaptive-mass quasi-zero stiffness vibration isolator

Abstract

This study proposes and systematically investigates a bioinspired frog vibration isolator (BFVI) featuring quasi-zero stiffness (QZS) characteristics and adaptive load capacity, aiming to address the degradation in vibration isolation performance commonly observed in traditional isolators under varying load conditions. A composite electromagnetic structure integrating horizontal and vertical configurations is constructed. The electromagnetic force model is derived using the filament method, and the influence of key geometric parameters—including structural rod length, initial angle, magnet dimensions, and current intensity—on the quasi-zero stiffness behavior is thoroughly analyzed. A nonlinear dynamic differential equation is established based on the Lagrange approach, and the harmonic balance method (HBM) is employed to reveal the transmission rate shift induced by mass variation. The effectiveness of adaptive current control in mitigating this shift is theoretically demonstrated. Furthermore, an active controller based on the nonlinear backstepping method is designed. Simulation results confirm adaptive current regulation effectively compensates for equilibrium deviation and performance loss caused by load fluctuations. Static experiments validate the QZS characteristics of the BFVI while time-varying load experiments confirm the controller's regulation capabilities and system response. Transmission rates under both fixed and adaptive current conditions are compared. Results show the system provides strong active regulation and effective low-frequency isolation under varying loads. This work offers new insights and strategies for integrating intelligent active control with bioinspired vibration isolation in complex engineering scenarios.