Effects of system parameters and damping on an optimal vibraiton-based energy harvester

Daqaq, Mohammed F., Renno, Jamil M., Farmer, Justin R. and Inman, Daniel J. (2007) Effects of system parameters and damping on an optimal vibraiton-based energy harvester. In Proceedings of 48th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference. American Institute of Aeronautics and Astronautics. 11 pp . (doi:10.2514/6.2007-2361).

Abstract

The authors present a comprehensive study of the effects of damping and electromechanical
coupling on the power optimality of a vibration-based energy harvester. The harvester
under consideration utilizes a piezoceramic element operating in the {33} mode to scavenge
mechanical energy emanating from a sinusoidal-base excitation. Under typical operating
conditions, the piezoceramic element is subjected to small strains and low electric fields,
which allows for the adaptation of the linear small-signal constitutive law to model its
behavior. To optimize the harvested power, previous researches neglected the role of mechanical
damping. This lead to results suggesting that the optimal-harvesting frequencies
are not effected by mechanical damping. However, in this paper, exact expressions for
the optimal frequency ratios that account for damping are derived. The results show that
mechanical damping affects the optimal frequency ratios and optimal harvested power qualitatively
and quantitatively. The effects of the electromechanical coupling coefficient is also
explored. It is observed that there is an optimal value of the coupling coefficient beyond
which the harvested power decreases. This result breaks the taboo suggesting that larger
electromechanical coupling culminates in more efficient energy harvesting devices. Additionally,
it is shown that at the optimal frequencies, and optimal load resistance, increasing
the electromechanical coupling saturates the harvested power

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