A locally resonant non-contact absorber based on electromagnetic induction for vibration suppression

Electromagnetic interactions hold promise in the realms of dynamics and control, especially when eddy currents induced through coils combine with permanent magnets to produce a Lorentz force. A coil's interaction with eddy currents, stemming from two-way coupling via mutual inductance, enables non-contact sensing and actuation of nearby metallic structures. When combined with vibrating structures, this electromagnetic interaction paves the way for innovative applications for structural health monitoring and vibration control. In this investigation, a locally resonant electromagnetic unit cell is proposed to impose damped vibration absorption on the dynamics of an oscillating beam. This approach of noncontact vibration absorption preserves the resonant characteristics of the host structure, while facilitating precise calibration and tuning via an electrical shunt. This induced local resonance is pivotal for adaptive vibration control and suppression, serving as a novel mechanism to mitigate potential damage or fatigue in vital structural components. In addition, locally resonant structures have been demonstrated in the implementation of elastic waveguiding and related applications. In this investigation, the non-contact vibration absorber is examined and modeled via a lumped parameter approach combining the fundamental laws of elastic mechanics and electromagnetics. The resulting displacement-force transmissibility is examined and compared to the more traditional approach of a LC-shunted piezoelectric absorber. These investigations illustrate the expected challenges stemming from high electrical resistivity in the electromagnetic coil and sensitivity to the lift-off distance. A mitigation technique for these challenges is proposed, involving the integration of negative impedance converters in the electrical shunt which allows the absorber to be optimally tuned.