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Vibration based piezoelectric energy harvesting using cantilevered bimorph beams under base excitation has been the subject of numerous investigations during the last two decades. One major topic of the recent research is the purposeful introduction of nonlinearities which lead to a bistable behavior of the system to improve performance. The mechanical domain of those systems is usually modeled as a Duffng oscillator with a negative linear stiffness and a positive cubic stiffness. Although such a model is generally able to display the desired behavior it becomes clear from the physical modeling process that higher nonlinear terms might be necessary to give a proper representation of the physical system.
This paper recapitulates the modeling process of a magneto elastic piezoelectric energy harvester and presents experimental measurements showing a qualitative behavior that is not predicted by the commonly used cubic model. Further it is shown that a refined model is not only able to predict the meassured behavior but also leads to different results regarding the optimal operating range for the energy harvester.