Design and performance analysis of a low-frequency vibration isolator with dual negative stiffness: Roller–cam, steel wire rope, and symmetric tetrahedron

Low-frequency vibration isolation is essential for precision systems; however, conventional linear isolators are limited by the inherent coupling between static stiffness and natural frequency. To overcome this limitation, a dual negative-stiffness quasi-zero-stiffness (DNS-QZS) isolator is developed by integrating a roller–cam mechanism, steel wire-rope elements with hysteretic damping, and a symmetric tetrahedral support structure. An improved Bouc–Wen hysteresis model is formulated to characterize the nonlinear restoring force behavior. Experimental and numerical results show that the proposed isolator begins to attenuate transmitted vibration energy in the low-frequency range and achieves effective vibration isolation when the excitation frequency exceeds approximately 7.7 Hz, where the transmissibility falls below 0 dB and remains suppressed over a broad frequency band. The DNS-QZS isolator exhibits low equivalent stiffness near equilibrium and enhanced damping, enabling stable and broadband low-frequency isolation while retaining sufficient load-bearing capability. These findings demonstrate the practical applicability of the proposed design in advanced vibration control scenarios.