A ProofofConcept Study on an InternalResonanceBased Piezoelectric Energy Harvester With Coupled ThreeDimensional BendingTorsion Motions

Abstract

By exchanging the internal energy between coupled vibration modes, internalresonancebased energy harvesters may provide an effective solution to broadening and enhancing bandwidth and power performance in dealing with natural vibration sources. With the development of piezoelectricbased transducers, thickness and face shear coefficients in proper piezoelectric elements can also generate power output from shear deformation on the core vibrating elements. However, in most cantileverbased energy harvesters that focused on bending modes, the shear responses were neglected. In this paper, we present an internalresonancebased piezoelectric energy harvester with threedimensional coupled bending and torsional modes, for the first time. The finetuned system leverages a twotoone internal resonance between its first torsion and second bending modes to enhance the power output with piezoelectric effects. The dynamic behavior implies the coexistence of inplane and outofplane motions under a single excitation frequency, and the corresponding strain changes in the bending and shear directions are captured by bonded piezoelectric transducers. Dependence between excitation levels and the internalresonance phenomenon is justified as a critical system parameter study; the results also indicate that an intriguing nonperiodic region exists near the center frequency. The outcomes of this study feature a multidirectional and multimodal energy harvester that displays rich dynamic behaviors. The operational bandwidth is promising for broadband energy harvesting, and the output voltage is enhanced by capturing both inplane and outofplane motions at the same time.