Magnetically modulated sliding structure for low frequency vibration isolation

Magnetically modulated sliding structure (MMSS) is proposed and systematically investigated in this paper. The MMSS consists of the sliding beam and a pair of repulsive magnets. The sliding beam can provide negative stiffness, which can be modulated by a pair of repulsive magnets (hardening positive stiffness). The static analysis is completed to fully clarify the modulation mechanism. With the modulation of magnets, the sliding beam can exhibit favorable high-static-low-dynamic stiffness (HSLDS). The dynamic model of the MMSS is developed to evaluate its response when subject to base excitation. The displacement transmissibility is derived by the harmonic balance method (HBM). Transmissibility curves show that the MMSS isolator possesses a low resonant frequency and can isolate vibration in a wide frequency range. The principle prototype is fabricated and tested. The effectiveness of the modulation mechanism in realizing quasi-zero stiffness (QZS) is verified by static experiment. Dynamic tests under periodic, sweep and random excitation demonstrate that the isolator exhibits excellent low frequency isolation performance and the vibration exceeding 4 Hz can be effectively isolated. The MMSS system provides a new approach to solve the problem of low frequency vibration isolation. The modulation mechanism, that is, utilizing hardening stiffness to modulate negative stiffness, is of reference significance for the design of HSLDS isolators.