Beneficial performance of a quasi-zero-stiffness vibration isolator with displacement-velocity feedback control

A displacement-velocity feedback control method is proposed to enhance the isolation performance of a quasi-zero-stiffness vibration isolator (QZS-VI). Time delay is considered in the controlled QZS-VI system. First, the steady-state solutions are obtained using the averaging method and validated by a numerical method. The jump phenomenon and frequency island phenomenon can occur, and a stability analysis is implemented. Then, the effects of the time delay and feedback gain on the frequency response and stability of solutions are analyzed in detail. Then, the force transmissibility is defined to evaluate the isolation performance of the controlled QZS-VI system. The results show that the time delay mainly affects the stability of the controlled system and weakly influences the isolation performance. The proposed displacement-velocity feedback control method can effectively suppress the vibration in the resonant region without affecting the performance in the isolation region. Finally, the vibration control effect is illustrated by the concept of an equivalent damping ratio.