Nonlinear dynamics of a magnetic vibration isolator with higher-order stable quasi-zero-stiffness

The concept of quasi-zero-stiffness (QZS) isolator was proposed in recent decades for low-frequency vibration isolation. However, the QZS feature is preserved only in the vicinity of the equilibrium point, which causes a dissatisfactory isolation effect especially when experiencing large excursion. Therefore, extending the QZS displacement range is very crucial for improving the isolation performance. This paper proposes a magnetic higher-order stable QZS mechanism to obtain a very wide QZS displacement range. The design criteria for the higher-order QZS property with stable static equilibrium point are expounded. The frequency response characteristics of the higher-order QZS isolator are analyzed without involving polynomial approximation. The complicated nonlinear dynamic behaviors are investigated in detail. The vibration isolation performance is compared with conventional QZS isolator and non-QZS isolator, revealing the advantages of the higher-order QZS isolator. An experimental prototype of the 5th-order QZS isolator is fabricated and tested, exhibiting greatly superior vibration isolation performance in comparison to the 1st-order QZS isolator and non-QZS isolator.