Vibration isolation of a beam via negative resistance electromagnetic shunt dampers

In this study, two novel electromagnetic shunt damping vibration isolators (EMSD-VIs) were developed for the vibration isolation of a beam structure. The proposed isolator utilizes a pair of electromagnetic coils and permanent magnet and a box-shaped spring to generate both variable damping and spring effect. The governing equation of the EMSD-VI-supported beam was established according to Galerkin method. The negative resistance was proposed to improve the performance of the isolator. The stability analysis was investigated to determine the design rules of the shunted negative resistance. The acceleration transmissibility of the beam system was simulated by using passive EMSD-VI control and negative resistance (NR)-EMSD-VI control. The experiment was conducted to verify the theoretical model and the numerical simulation. The experimental results demonstrated that the proposed NR-EMSD-VI is capable of isolating the first-order and the third-order vibrations. Also, a discussion of the resonance frequency shift toward higher value was given.