We have developed four-winged robot birds, called ornithopters, that can take off and fly with the agility of swift, hummingbirds and insects. We did this by reverse engineering the aerodynamics and biomechanics of these creatures.
Our ornithopters have the potential to surpass and surpass existing unmanned configurations with static wings or propellers.
What are ornithopters?
Ornithopters are flying machines based on the design of birds. Existing unmanned configurations rely on propellers and static wings. Ornithopters flutter their wings to create thrust forward. The complex relationship between aerodynamics and wing motion allows birds and insects to fly in a way that is impossible for ordinary drones.
Why do we want ornithopters?
Ornithopters fly differently to conventional drones. They can slide, soar and perform aerobatics. In different situations, they can either save energy by flying like a normal plane, or decide to move the cursor. They can slowly take off and land in tight spaces, but can quickly soar up to a perch like a bird.
Current multi-engine drones hang very well, but use more energy in the flight forward than when recruiting, so they can not travel far. Stationary winged drones can move efficiently at high speeds, but freezing is usually not possible without compromising the entire structure. There are hybrid concepts, usually with wings and rotors. Hybrid aircraft perform poorly when hovering and cruising compared to other designs due to the extra weight and pull more parts.
The fluttering wings are an original decision of nature regarding the need to fly both fast and slow, as well as to land and take off from anywhere. For a bird or insect, each part of the system is used for soaring and cruising flights, without carrying extra pushers and extra wings.
Existing drones with fixed and swivel wings are so well understood that designs are now approaching the limits of how effective they can be. Adding something new is worth other aspects of performance.
In principle, ornithopters are able to perform more complex missions than conventional aircraft, such as long-distance flight, time lag and maneuvering in tight spaces. Ornithopters are less noisy and safer to use around people due to their large wing area and slow wing strikes.
How to make a working ornithopter?
Ornithopter is a very complex system. Until now, the fluttering wings of drones have flown slowly and are unable to reach the speed and power required for vertical aerobatics or steady soaring.
Several commercially available ornithopters are designed to fly forward. They rise slowly, like a plane that has no power, and cannot hang or rise vertically.
Our design differs in several ways.
One difference is that our ornithopters use a “clap and throw” effect. The two pairs of wings flutter so that they meet like hands clapping. This makes enough of an extra push to lift the weight when hanging.
We have increased efficiency by adjusting the wing / body loop to store and restore the energy of the movable wing when the wings change direction like a spring. We also found that most of the energy loss was due to the gear bending under the wing load. We solved this by using minute bearings and rearranging the shafts in the transmission to hold the gears correctly.
The large tail, consisting of a rudder and an elevator, creates a large turning force. This allows you to perform aggressive aerobatic maneuvers and quickly switch from horizontal to vertical flight.
The system was designed so that it could tilt its nose up, rapidly increasing its angle of attack to the point where the wing does not create a rise, a phenomenon called “dynamic stall”.
The dynamic stall creates a lot of traction, turning the wing into a parachute to slow down the plane. This would be undesirable for many drones, but the ability to enter this state and recover quickly adds maneuverability. This is useful when working in cluttered conditions or when planting perch.
Catch up with evolution
One of the main conclusions of our work was that a practical ornithopter can achieve efficiency similar to a helicopter aircraft. After the release of some additional force for the ornithopter, several behaviors became possible.
This has indeed shown that aircraft optimization is a key factor in ensuring the viability of these new aircraft designs. We are currently working on the use of wing designs copied from nature. We hope for the same big improvements.
For some reason, such great effective results from the design changes of these new systems should not be surprising. Winged organisms have been optimized by evolution for hundreds of millions of years. We humans have been at this for less than 200 years.
Jawaan Chal, Joint Department of Sensory Systems, DST Group, University of South Australia.
This article is republished from a conversation under a Creative Commons license. Read the original article.