Modeling a Nonlinear Harvester for Low Energy Vibrations

The availability of reliable analytical models is essential to the optimal design of energy harvesters and for the prediction of the system behavior. In this paper, we consider a low-input nonlinear system based on a flexible buckled beam forced in a bistable configuration. The harvester has been demonstrated to generate power in the excess of 400 μW with the optimal resistive load of 15 kΩ and a monotonic input with rootmean-square accelerations of 13.35 m/s2. The power generated is suitable for powering low-power measurement systems or sensor nodes. This paper focuses on a methodology for the modeling of the mechanical dynamical behavior of the device subject to a periodic impulsive signal. A measurement protocol for the evaluation of system's hidden quantities, the beam's restoring force, and the beam's displacement between its stable states is introduced. A second-order behavioral model with a nonlinear term representing the beam's restoring force has been used. In order to model the nonlinearity, two different potential energy functions have been compared by fitting the models to the experimental data with different constrains, through a performance index evaluating the fitting error.