Experimental Verification of Models for Microfabricated Piezoelectric Vibration Energy Harvesters

Abstract

Experiments have been performed to verify power-optimized modal models of piezoelectric vibration harvesters for microelectromechanical systems. Such harvesters can power a variety of sensors, and there have been recent national workshops dedicated to harvesting. Detailed experimental results, including displacement histories and electrical output, are provided over a range of frequencies and electrical loadings to compare with (optimized) modal models. The harvester geometry considered is that of a symmetric bimorph macroscale cantilever. Although some experimental work for cantilevered bimorph harvesters has been published, key testing and/or device parameters needed for model verification are missing and/or data at and near power optima (the most interesting operating points) are not provided. Therefore, a detailed set of experiments was performed using power-optimized modeling results to guide the test matrix. Over the broad range of parameters tested, the models accurately predicted all trends and device performance away from device resonances (resonance and antiresonance frequencies). Near the resonance frequencies, the model consistently underpredicts electrical performance, which is satisfactorily attributed (and experimentally supported) to the well-known piezoelectric coupling nonlinearity in the large-strain region. The data presented herein can serve as benchmark data to verify other modeling efforts. The verified models have been used to optimally design microelectromechanical system harvesters for commercial aircraft and microfabrication is ongoing.