Flies just like a bird: New drone to shake the industry?
Via The Conversation, engineers at the University of South Australia have revealed that they have made the ornithopter, a bird-like drone which they are confident will shake the current drone market, dominated by drones powered by static wings or propellers.
The ornithopter was made by reverse engineering the aerodynamics and biomechanics of hummingbirds and insects. In the air, the ornithopter will flap its wings to generate forward thrust, taking after the complex relationship between aerodynamics and wing movements of birds that allows them to fly in ways that are impossible for conventional drones.
“An ornithopter is a highly complex system,” writes Javaan Chahl, DST Group Joint Chair of Sensor Systems at the University of South Australia. “Until now, flapping wing drones have been slow flying and not capable of achieving the speed and power required for vertical aerobatics or sustained hovering. The few commercially available ornithopters are designed for forward flight. They climb slowly like an underpowered aeroplane, and can’t hover or climb vertically.
“Our design is different in several ways.
“One difference is that our ornithopters make use of the “clap and fling” effect. The two pairs of wings flap such that they meet, like hands clapping. This makes enough extra thrust to lift their body weight when hovering.
“We improved efficiency by tuning the wing/body hinge to store and recover the energy of the moving wing when the wings change direction, like a spring. We also discovered that most of the energy loss happened because the gears flexed under the load of driving the wing. We resolved this with minute bearings and by rearranging shafts in the transmission to keep the gears spaced correctly.
“The large tail, comprising a rudder and elevator, creates a lot of turning force. This allows aggressive aerobatic manoeuvres and switching fast from horizontal to vertical flight.
“The system was designed to be able to pitch nose up, rapidly increasing its angle of attack to the point where the wing does not generate lift, a phenomenon called “dynamic stall”. Dynamic stall creates a lot of drag, turning the wing into a parachute to slow the aircraft. This would be undesirable in many drones, but the ability to enter this state and quickly recover adds to manoeuvrability. This is useful when operating in cluttered environments or landing on a perch.
Chahl added that ornithopters fly differently to conventional drones in that they can glide, hover, can perform aerobatics and, in different situations, can either save energy by flying like a regular aeroplane or choose to hover. They can take off and land slowly in tight spaces, yet quickly soar upwards to perch like a bird.
“In principle, ornithopters are capable of more complex missions than conventional aircraft, such as flying long distances, hovering at times, and manoeuvring in tight spaces. Ornithopters are less noisy and safer to use around humans, because of their large wing area and slow wing beats.”
Catching up with evolution
“One of the major findings of our work was that a practical ornithopter might achieve similar efficiency to a propeller driven aircraft. Several behaviours became possible for the ornithopter once some additional power was liberated.
“This proved that optimising the flight apparatus is key to making these new aircraft designs viable. We are now working to use wing designs copied from nature. We hope for equally large improvements.
“In some ways, such large efficiency gains from design changes in these new systems should not be surprising. Winged organisms have been optimised by evolution over hundreds of millions of years. We humans have been at it for less than 200 years.”