Abstract:

Low-frequency vibration suppression under multidirectional excitations remains a major challenge in engineering systems. To address this issue, a novel bidirectional quasi-zero-stiffness (QZS) X-shaped linkage isolator incorporating torsional positive springs and a torsional magnetic negative stiffness (TMNS) mechanism connected in parallel is proposed. The parallel torsional positive-negative-stiffness strategy enables simultaneous QZS characteristics in both horizontal and vertical directions. An analytical model describing the coupled in-plane dynamics is established and validated through ADAMS simulations. The stability analysis shows that the stable potential well disappears under horizontal-torsional coupling when the vertical static equilibrium displacement exceeds a critical threshold. With the torsional motion constrained, the coupled dynamic behavior and transmissibility under bidirectional excitations are further investigated. Compared with previous structures, the proposed isolator achieves superior bidirectional low-frequency vibration-isolation performance. The experimental results agree well with the theoretical predictions, confirming the effectiveness of the proposed bidirectional vibration-isolation mechanism.

Key words: quasi-zero-stiffness (QZS), low-frequency vibration isolation, torsional magnetic negative stiffness (TMNS), bidirectional vibration isolator, X-shaped mechanism