The
pizzicato knee-joint energy harvester: characterization with biomechanical data
and the effect of backpack load
Abstract
The reduced
power requirements of miniaturized electronics offer the opportunity to create
devices which rely on energy harvesters for their power supply. In the case of
wearable devices, human-based piezoelectric energy harvesting is particularly
difficult due to the mismatch between the low frequency of human activities and
the high-frequency requirements of piezoelectric transducers. We propose a
piezoelectric energy harvester, to be worn on the knee-joint, that relies on
the plucking technique to achieve frequency up-conversion. During a plucking
action, a piezoelectric bimorph is deflected by a plectrum; when released due
to loss of contact, the bimorph is free to vibrate at its resonant frequency,
generating electrical energy with the highest efficiency. A prototype,
featuring four PZT-5H bimorphs, was built and is here studied in a knee
simulator which reproduces the gait of a human subject.
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