Design and experiment of a high-static–low-dynamic stiffness isolator using a negative stiffness magnetic spring

Abstract To improve the vibration isolation performance under low frequency excitation, a negative stiffness magnetic spring (NSMS) is employed to reduce the resonance frequency of the linear isolator. The NSMS comprising a pair of coaxial ring permanent magnets is installed in parallel with the mechanical spring to counteract its positive stiffness. The major feature of the isolator is that it has high static low dynamic stiffness (HSLDS). In this paper, the model of the HSLDS isolator and the NSMS is analyzed firstly; and the magnetic force and stiffness exerted between the inner magnet and the outer magnet is then calculated based on the Amperian current model. After analyzing the effect of the geometric parameters of the magnets on the stiffness characteristic of the NSMS, a designing procedure for the NSMS is proposed. Then the nonlinear dynamic equation of the isolator is established and numerical simulation is performed to obtain the transmissibility. Finally, the detailed design of the HSLDS isolator is given and an experimental setup is proposed. The experimental results demonstrate that the NSMS can reduce the resonance frequency of the isolator indeed; and the isolation performance of the proposed isolator is improved accordingly.