Flapping wing drone inspired by swifts

A drone prototype that mimics the aerobatic manoeuvres of one of the world’s fastest birds, the swift, is being developed by an international team of aerospace engineers in the latest example of biologically inspired flight.

A research team from South Australia, Singapore, China and Taiwan has designed a 26 g ornithopter (flapping wing aircraft) that can hover, dart, glide, brake and dive just like a swift, making them more versatile, safer and quieter than the existing quadcopter drones. Their work has been published in the journal Science Robotics.

Similar in size to a swift, and weighing the equivalent of two tablespoons of flour, the flapping wing drone has been optimised to fly in cluttered environments near humans, with the ability to glide, hover at low power and stop quickly from fast speeds, avoiding collisions — all things that quadcopters can’t do.

“There are existing ornithopters but, until now, they were too inefficient and slow to be agile,” said aerospace engineer Professor Javaan Chahl, from the University of South Australia. “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.”

Project leader Dr Yao-Wei Chin, from the National University of Singapore, said the drones could be used successfully in a range of environments. The surveillance applications are clear, but novel applications include pollination of indoor vertical farms without damaging dense vegetation — unlike the rotary-propelled quadcopters whose blades risk shredding crops. Their stability in strong winds means the ornithopter drone could also be used to chase birds away from airports, reducing the risk of them getting sucked into jet engines.

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

Dr Yao-Wei Chin with the flapping wing drone prototype.

By improving the design so ornithopters can now produce enough thrust to hover and to carry a camera and accompanying electronics, the flapping wing drone could be used for crowd and traffic monitoring, information gathering, and surveying forests and wildlife. The light weight and the slow beating wings of the ornithopter pose less danger to the public than quadcopter drones in the event of a crash and, given sufficient thrust and power banks, it could be modified to carry different payloads depending on what is required.

One area that requires more research is how birds will react to a mechanical flying object resembling them in size and shape. Small, domesticated birds are easily scared by drones, but large flocks and much bigger birds have been known to attack ornithopters. Dr Chin also emphasised that engineers are still a long way from truly 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.

“At most, I would say we are replicating 10% of biological flight,” he said.

Top image caption: Swifts are the inspiration for the flapping wing drone.

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