Theoretical modeling and experimental analysis of nonlinear electromagnetic shunt damping

Linear electromagnetic shunt damping (L-EMSD) has been investigated deeply for vibration control in previous studies. This paper proposes nonlinear electromagnetic shunt damping (N-EMSD) for vibration isolation enhancement of linear vibration isolators (LVIs), which has not been discussed in existing literature. N-EMSD composes of a pair of the permanent magnets (PMs) and a pair of the coils, where the two coils are wound in opposite direction and connected in series. The nonlinear electromagnetic coupling coefficient is derived. The coupling governing equations of a LVI with N-EMSD are established and the amplitude-frequency relationship is theoretically derived using the harmonic balance method (HBM). Both the simulations and experiments are carried out to verify the nonlinear damping characteristic of N-EMSD. The results demonstrate that the LVI with N-EMSD can effectively reduce the vibration in the resonance region without affecting the vibration isolation performance in the isolation region compared with the traditional L-EMSD. It is also found in both simulation and experiment for the two coils configuration that the frequency of the induced voltage is twice the frequency of the displacement. Furthermore, the transmissibility of the LVI with N-EMSD reduces with the increase of the input amplitude in the resonance region, which demonstrates the nonlinearity of N-EMSD. The natural frequency slightly decreases with the decrease of the peak transmissibility. This paper extends the electromagnetic shunt damping (EMSD) technique from linear to nonlinear fields and provides a guideline to design nonlinear damping. (C) 2020 Elsevier Ltd. All rights reserved.