A team of University of South Australia PhD students has modelled the dragonfly’s unique body shape and aerodynamic properties in the hope that it will provide inspiration for the next generation of flapping-wing drones.
Working remotely due to the pandemic, the students turned their homes into makeshift labs, solving mathematical formulas on whiteboards, digitising stereo photographs of insect wings and then turning them into 3D models, and using spare rooms as rapid-prototyping workshops in order to test parts fabricated for their flapping-wing drone. Their findings have been published in the journal Drones.
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‘Dragonflies are supremely efficient in all areas of flying. They need to be,’ said Javaan Chahl, professor of sensor systems, who led the study. ‘After emerging from underwater until their death (up to six months later), male dragonflies are involved in perpetual, dangerous combat against male rivals. Mating requires an aerial pursuit of females and they are constantly avoiding predators. Their flying abilities have evolved over millions of years to ensure they survive.
‘They can turn quickly at high speeds and take off while carrying more than three times their own body weight,’ he continued. ‘They are also one of nature’s most effective predators, targeting, chasing and capturing their prey with a 95 per cent success rate.’
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Dragonflies’ amazing eyesight, speed and agility make them notoriously difficult to capture, so the researchers developed a special optical technique to photograph the wing geometry of 75 different dragonfly species from glass display cases in museum collections. In a world first, they then used the photos to construct 3D images of the wings that enabled them to pick up subtle and not so subtle differences in their shapes.
‘Dragonfly wings are long, light and rigid, with a high lift-to-drag ratio, which gives them superior aerodynamic performance,’ said Chahl. ‘Their long abdomen, which makes up about 35 per cent of their body weight, has also evolved to serve many purposes. It houses the digestive tract, is involved in reproduction, and it helps with balance, stability and manoeuvrability. The abdomen plays a crucial role in their flying ability.’
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The researchers believe that dragonfly-inspired drones would benefit from reduced drag and improved load capacity, and would be particularly versatile, capable of collecting and delivering awkward, unbalanced loads, safely operating near people, exploring delicate natural environments and executing long surveillance missions.