Is it a bird, a plane? A flapping wing drone

A drone prototype that mimics the aerobatic manoeuvres of one of the world’s fastest birds, the swift, is the latest example of engineers taking inspiration from nature.

The team from South Australia, Singapore, China and Taiwan has designed a 26 gram ornithopter (flapping wing aircraft) which can hover, dart, glide, brake and dive just like a swift. It can also rapidly switch between manoeuvres instantly in mid-air.

Weighing the equivalent of two tablespoons of flour and around 25cm long, the flapping wing drone has been optimised to fly in cluttered environments near humans. It can glide, hover at very low power, and stop quickly from fast speeds while avoiding collisions – all things that existing quadcopters can’t do.

The design has been described in the journal Scientific Reports.

Flapping wing drone ornithopter
The newly designed ornithopter. Credit: Chin et al, Science Robotics

Flapping wing drone waves goodbye to rotors

The team, which includes UniSA aerospace engineer Professor Javaan Chahl, has designed the flapping wing drone to be similar in size to a swift, or large moth.

The researchers were able to construct such a skilled winged robot, also called an ornithopter, by creating an elastic mechanism that minimizes wobble and increases energy efficiency. The elastic drive replaces a rigid and unstable crank-rocker that normally drives flapping motion in ornithopters.

Chahl says copying the design of birds, like swifts, is just one strategy to improve the flight performance of flapping wing drones.

“There are existing ornithopters but, until now, they were too inefficient and slow to be agile. We have overcome these issues with our flapping wing prototype, achieving the same thrust generated by a propeller.”

“Flapping wings can lift like an aeroplane wing, while making thrust like a propeller and braking like a parachute. We have put this together to replicate the aggressive flight patterns of birds by simple tail control.”

Yes it could be used for surveillance, but there are other uses too

National University of Singapore scientist Dr Yao-Wei Chin, who led the project, says the biologically-inspired drones could be useful in a range of environments.

The surveillance applications are clear. But the engineers are also looking at the potential to pollinate indoor vertical farms without damaging dense vegetation. Rotary-propelled quadcopters risk shredding crops with their blades in the same situation.

Ornithopters are also stable in strong winds, meaning they could be used to chase birds away from airports.

“The optimised ornithopter acts as a kind of scarecrow, greatly saving on labour costs for pest control companies and airport operators,” says Chin.

The researchers also think the latest design could be improved to produce enough thrust to hover while carrying a camera and accompanying electronics. And that would make the flapping wing drone useful for crowd and traffic monitoring, information gathering, and surveying forests and wildlife.

The light weight and the slow beating wings of the ornithopter poses less danger to the public than quadcopter drones in the event of a crash. Given sufficient thrust and power banks it could also be modified to carry different payloads depending on what is required.

Flapping wing drones become bird prey

One question that remains, though, is how birds will react to a mechanical flying object resembling them in size and shape. Small, birds are easily scared by drones. On the other hand, large flocks and bigger birds sometimes attack ornithopters.

And while the bio-inspired breakthrough is impressive, Chin says we are still a long way from replicating biological flight.

“Although ornithopters are the closest to biological flight with their flapping wing propulsion, birds and insects have multiple sets of muscles which enable them to fly incredibly fast, fold their wings, twist, open feather slots and save energy.

“Their wing agility allows them to turn their body in mid-air while still flapping at different speeds and angles,” says Chin.

“Common swifts can cruise at a maximum speed of 31 metres a second, equivalent to 112 kilometres per hour or 90 miles per hour.

“At most, I would say we are replicating 10 per cent of biological flight.”

This article was first published on Australia’s Science Channel, the original news platform of The Royal Institution of Australia.

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