A novel large linear stroke high-static-low-dynamic stiffness vibration isolator with high magnetic negative stiffness and compactness

Traditional high-static-low-dynamic stiffness (HSLDs) vibration isolator can effectively mitigate low frequency micro-amplitude vibration, but its isolation performance always deteriorates under large amplitude vibration due to the nonlinearity of negative stiffness spring. To address the issue, based on the convex-concave counteraction principle, a novel large linear stroke magnetic negative stiffness spring (LLS-MNSS) is proposed to construct a large linear stroke high-static-low-dynamic stiffness (LLS-HSLDs) vibration isolator. The LLS-MNSS is composed of four magnetic rings, which can be divided into a group exhibiting concave negative stiffness and another group exhibiting convex negative stiffness. The analytical magnetic stiffness model of the LLS-MNSS is firstly established. Based on parameters analyses and Taylor expansion expression of the theoretical magnetic stiffness model, an optimization model is built to minimize the variation degree of resultant magnetic negative stiffness. By solving the presented optimization problem, the parameters of LLS-MNSS are elaborately determined, effectively counteracting the variation of concave negative stiffness by that of the convex negative stiffness over a wide displacement range, and results in an approximately constant resultant magnetic negative stiffness within a stroke of (-6.7 mm, 6.7 mm). Besides, the designed LLS-MNSS possesses higher negative stiffness and more superior compactness when considering an identical linear stroke, as evidenced by the results of the comparative analysis between the LLS-MNSS and four existing magnetic negative stiffness springs with wide linear stroke. Finally, the theoretical and experimental results demonstrate that the low frequency vibration isolation performance of the LLS-HSLDs isolator exhibits remarkable stability even under large amplitude vibration.