A Novel Bioinspired Quasi-Zero Stiffness Ultra-Low-Frequency Vibration Isolation System for Ambulance Stretchers: Insights from Avian Lower Limbs

Inspired by the “M-shaped” structure of bird lower limbs, this study proposes a bioinspired quasi-zero-stiffness (BQZS) structure ultra-low-frequency vibration isolation system designed for ambulance stretchers to address the challenge of coordinating vibration reduction performance and static load stability. The research first simplifies the bird lower limb structure into a quasi-zero-stiffness model at bottom of the stretcher and investigates the effects of key parameters on BQZS vibration isolation performance through theoretical analysis. Furthermore, from the perspective of the overall stretcher system, low-frequency vibration isolation performance is evaluated via the harmonic balance method to study its response characteristics. The experimental results show that compared with the conventional linear system, the BQZS system achieves a maximum optimization amplitude of 75% in acceleration response, maintains low displacement transmissibility across the entire frequency range, and nearly realizes effective vibration isolation across the full-frequency band. This study provides a new technical solution for low-frequency vibration isolation of ambulance stretchers and broadens the application of vibration isolation technology in the medical rescue field.