FREQUENCY TUNING CONCEPTS FOR PIEZOELECTRIC CANTILEVER BEAMS AND PLATES FOR ENERGY HARVESTING

The _link_ (pdf)

A great deal of research has repeatedly demonstrated that piezoelectric energy harvesters
hold the promise of providing an alternative power source that can enhance or replace
conventional batteries and power wireless devices. Also, ambient vibrations have been the focus
as a source due to the amount of energy available in them. By using energy harvesting devices to
extract energy from their environments, the sensors that they power can be self-reliant and
maintenance time and cost can be reduced. In order to harvest the most energy with the device,
the beam’s fundamental mode must be excited. However, this is not always possible due to
manufacturing of the device or fluctuations in the vibration source. By being able to change the
frequencies of the beam, the device can be more effective in harvesting energy. This work
utilizes a shunt capacitor-tuning concept on a piezoelectric bimorph energy harvester. Design
parameters are investigated and discussed to achieve the most tuning from the device. Static and
dynamic beam and plate models are derived to predict natural frequencies and power and are
later used to compare to experimental results. Results are presented for the tunability of a square
cantilever bimorph. In addition, the amount of power able to be harvested from each _layer_ of the
bimorph is tested. Finally, several other tuning methods are discussed.
FREQUENCY TUNING CONCEPTS FOR PIEZOELECTRIC CANTILEVER
BEAMS AND PLATES FOR ENERGY HARVESTING
David Charnegie, M.S.
University of Pittsburgh, 2007