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The concept of energy harvesting in unmanned aerial vehicles (UAVs) has received much attention in recent years.
Solar powered flight of small aircraft dates back to the 1970s when the first fully solar flight of an unmanned
aircraft took place. Currently, research has begun to investigate harvesting ambient vibration energy during
the flight of UAVs. The authors have recently developed multifunctional piezoelectric self-charging structures
in which piezoelectric devices are combined with thin-film lithium batteries and a substrate layer in order
to simultaneously harvest energy, store energy, and carry structural load. When integrated into mass and
volume critical applications, such as unmanned aircraft, multifunctional devices can provide great benefit over
conventional harvesting systems. A critical aspect of integrating any energy harvesting system into a UAV,
however, is the potential effect that the additional system has on the performance of the aircraft. Added mass
and increased drag can significantly degrade the flight performance of an aircraft, therefore, it is important to
ensure that the addition of an energy harvesting system does not adversely affect the efficiency of a host aircraft.
In this work, a system level approach is taken to examine the effects of adding both solar and piezoelectric
vibration harvesting to a UAV test platform. A formulation recently presented in the literature is applied to
describe the changes to the flight endurance of a UAV based on the power available from added harvesters and the
mass of the harvesters. Details of the derivation of the flight endurance model are reviewed and the formulation
is applied to an EasyGlider remote control foam hobbyist airplane, which is selected as the test platform for this
study. A theoretical study is performed in which the normalized change in flight endurance is calculated based
on the addition of flexible thin-film solar panels to the upper surface of the wings, as well as the addition of
flexible piezoelectric patches to the root of the wing spar. Experimental testing is also performed in which the
wing spar of the EasyGlider aircraft is modified to include both Macro Fiber Composite and Piezoelectric Fiber
Composite piezoelectric patches near the root of the wing and two thin-film solar panels are installed onto the
upper wing surface to harvest vibration and solar energy during flight. Testing is performed in which the power
output of the various harvesters is measured during flight. Results of the flight testing are used to update the
model with accurate measures of the power available from the energy harvesting systems. Finally, the model is
used to predict the potential benefits of adding multifunctional self-charging structures to the wing spar of the
aircraft in order to harvest vibration energy during flight and provide a local power source for low-power sensors.
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