Quirks & Quarks·Analysis

We could be a wing-beat closer to machines that fly like birds — with flapping wings

Bob McDonald's blog: Practical ornithopters that fly like hummingbirds or dragonflies have been a long-time dream. A new electrically powered flapping wing system could make insect-like flying machines a reality.

Bob McDonald's blog: A team in the UK has developed a tiny robot with a new design for flapping wings

The flapping wings of this robot designed by engineers at the University of Bristol in the U.K., are driven by electrical charges in the metal plates at the wing roots rather than by spinning motors. (Tim Helps, University of Bristol)

A British team has developed a new miniature flying robot that flaps its wings like an insect, with no conventional motors and gears. It's a step toward flapping flight that's more like the way animals do it.

Nature, of course, uses flapping wings on everything from mosquitoes to condors. Humans have had more success building flying machines that use propellers, rockets and jets.

But designing machines that imitate nature by flapping wings has been an ambition that goes back centuries. Leonardo da Vinci dreamed of human powered flight in the late 15th century with his designs for ornithopters, devices meant to to be constructed out of wood and cloth with wings attached to oar-like levers.

The pilot would use their arms to pump the levers up and down to power the wings.

As far as we know, da Vinci never built his designs. And human muscle power would have been insufficient to lift the weight of the machine and its pilot into the air.

In 2006, a team at the University of Toronto built the first piloted flapping wing aircraft to achieve sustained flight. It was driven by a gasoline engine and made a brief demonstration flight. 

WATCH | Flight of the University of Toronto Institute for Aerospace Studies ornithopter:

Then in 2010 the same team achieved the first human-powered ornithopter flight in an ultralight vehicle called Snowbird. Its wings spanned 32 metres, which is about the length of the wings on a 737 airliner, yet it weighed only 43 kg.

The gossamer aircraft was towed up to flight speed by a vehicle and then released. Then the pilot pumped a bicycle-style system that connected to the wings through a system of pumps and pulleys. It was able to maintain level flight with flapping wings alone for about 20 seconds, a few metres above the ground before gently landing. 

The vehicle now hangs on display at the Canadian Aviation and Space Museum in Ottawa.

The Snowbird ornithopter in flight. Its design was inspired by sketches made by Leonardo da Vinci in 1485. (Canadian Press)

When it comes to ornithopters, smaller machines a few tens of centimetres long have had the greatest success because weight can be reduced to a minimum. There are kits you can build at home, powered by rubber bands or small electric motors. But controlling ornithopters is difficult because of the machinery required to manipulate the wing as it flaps to maintain stable flight.

Getting an ornithopter to hover, fly backwards and be extremely manoeuvrable like a hummingbird or dragonfly has proved beyond our abilities.

That's one reason propeller-driven drones have dominated the market: they are easier to design and fly.

A team at the University of Bristol Faculty of Engineering in the U.K., has taken a new approach to flapping-wing flight with a robot currently in development. It eliminates traditional motors altogether, and is instead powered by electrostatic forces that involve no rotating parts or gears. The wings are driven by a unique system they call a liquid-amplified zipping actuator, or LAZA.

They published their latest findings this month in the journal Science Robotics.

WATCH | The University of Bristol LAZA device:

At the base of each wing is a pair of curved metal plates, one above and one below. An electric charge is applied to those plates, alternating from one to the other. A liquid surrounding the wing root amplifies the charge, so the wing is drawn up and down by electrostatic forces. The team says the flapping force exceeds those of both mammalian and insect muscle, and matches that of other mechanical flapping mechanisms driven by spinning motors.

The scientists hope that with LAZA, they've found a mechanism to drive future miniature flying machines that are even smaller — perhaps the size of insects.

Micro-robots that fly like insects would be extremely useful working their way through small spaces among the rubble of a collapsed building to find survivors, or entering hazardous environments.

A hummingbird sipping nectar. The speed and maneuverability provided by flapping wings is something ornithopter designers dream of emulating. (Submitted by Bindhu Mohan)

So the next time an annoying insect manages to escape a swat from your hand, think about how remarkable its flying abilities are, and how difficult it is for us humans to duplicate them.

ABOUT THE AUTHOR

Bob McDonald is the host of CBC Radio's award-winning weekly science program, Quirks & Quarks. He is also a science commentator for CBC News Network and CBC-TV's The National. He has received 12 honorary degrees and is an Officer of the Order of Canada.

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