Characterization and optimization of a 2DOF velocity amplified EM EH
A two degree of freedom velocity amplified electromagnetic energy harvester has been taken in consideration. The structure is constituted by a little mass which is responsible of the electromagnetic conversion, and an outer bigger mass, for the velocity amplification. The aim of the work has been to characterize both the whole system, and the electromagnetic part alone. It will be demonstrated that both show a significant nonlinearity through the study of the transfer function and of its hysteretic behaviour. Sine sweeps have been used, in order to analyse differences between the increasing and the decreasing frequency performance. The origin and the benefit of the resulting resonance frequency shifting will be discussed, in conjunction with the possibilities of investigating other kind of nonlinearities. Finally, an optimization process has been performed only on the electromagnetic part, considering coils with different wire diameters at fixed volume and magnetic field. The data and the results are showed in details in the plots.