A resonant frequency tunable, extensional mode piezoelectric vibration harvestingmechanism

Abstract

Electrical power for distributed, wireless sensors may be harvested from vibrations in theambient through the use of electromechanical transducers. To be most useful, theelectromechanical transducer should maximize the harvested power by matching itsresonant frequency to the strongest vibration amplitude in the source’s vibrationspectrum. This paper introduces a new frequency tunable mechanism wherein thedeformation of the piezoelectric elements is primarily in-plane extension, andbending effects may be neglected. The extensional mode resonator (XMR) is formedby suspending a seismic mass with two piezoelectric sheets. The mechanism ismade frequency tunable by an adjustable link that symmetrically pre-tensionsboth piezoelectric sheets. A prototype XMR has been built and tested that hasdemonstrated adjustable and repeatable resonant frequency variation from 80to 235 Hz. The electrical power generated by the XMR is also insensitive to thedriving frequency, when the resonant frequency is matched to the driving frequency.