Energy-Conserving Nonlinear Active Control for a Bird-Inspired Quasi-Zero Stiffness Stretcher Vibration Isolation System with Asymmetric Stiffness

Active control and nonlinear vibration isolation are effective methods for achieving optimal vibration isolation performance. However, the excessive energy consumption and potential instability of these approaches substantially limit their development and widespread application. This study proposes an active bionic quasi-zero stiffness stretcher vibration isolation (ABQZSSVI) system, inspired by the efficient cushioning and vibration damping mechanisms of birds’ legs. The ABQZSSVI system reduces the demand for energy consumption of active control through a nonlinear quasi-zero stiffness (QZS) design. The polarization sway instability caused by the asymmetric stiffness is further mitigated using a nonlinear robust sliding mode controller (SMC) with a nonlinear disturbance observer. Asymmetric stiffness characteristics and vibration damping performance were experimentally tested. Results demonstrate that the proposed ABQZSSVI system significantly alleviates the polarization sway instability, and enhances stretcher stability, and improves both the low-frequency vibration isolation performance and energy efficiency.