Semi-active control of a quasi-zero stiffness vibration isolation system using adjustable lateral springs with resonance detuning

Over the past decades, quasi-zero stiffness (QZS) vibration isolation systems have demonstrated a significant potential for low-frequency vibration isolation due to their nonlinear stiffness characteristics. Various passive QZS isolation systems have been proposed, incorporating different sources of negative stiffness in conjunction with high static-stiffness springs. However, most of the QZS isolation systems generally focus on addressing vibration of a single degree-of-freedom (DOF) QZS isolation system and exhibit rather limited performances in responding to a variation in external disturbances particularly at low frequencies. To enhance the vibration isolation performance of a multi-DOF QZS isolation system, this work introduces a semi-active two-DOF QZS isolation system, featuring lateral springs that generate controllable stiffness through an implementation of stepper motors. The system stiffness can be controlled based on feedback from an accelerometer. The effectiveness of this control approach is investigated by analysing the displacement frequency response across low to high frequencies. The simulation results demonstrate that the vibration amplitudes within the frequency range of interest can be significantly improved using this semi-active vibration isolation mechanism. The frequency associated with the peak displacement transmissibility has been reduced from 1.91 Hz to 1.02 Hz, while the peak amplitude has significantly decreased from 29.59 dB to 4.395 dB.