This morphing drone signifies a new era of aerial robotics, one where nature and technology merge to produce a feat of engineering.
Drones come in many forms. The most common variations are fixed wing and rotary. Both types are optimized to function in precise conditions. Fixed wings allow for sustained flight as the airfoil lets the drone glide. This boosts efficiency during windy conditions. However, fixed wing drones aren't as nimble as their rotary counterparts. So how does one get the best of both worlds - agility and sustained flight?
An answer may come from Switzerland. Engineer Dario Floreano and his team at the Ecole Polytechnique Federale de Lausanne (EPFL) developed a new type of drone which takes inspiration from nature. Floreano’s design, published in the Interface Focus Journal (December 2016), mimics the agility of a bird by fitting the drone’s extremities with artificial retractable feathers.
[Image Source: EPFL]
The feathers, or primaries, consist of fiberglass, covered with nylon fabric. They also contain a carbon fiber shaft for added strength. The shape-shifting drone can adapt to variable wind conditions by applying a morphing strategy. The artificial feathers fold back asymmetrically (one at a time) to rapidly enhance the maneuverability and control of the aircraft.
The drone eliminates wing tip vortices (rotating air behind the wing) by retracting both of the wing’s fringes and hence reducing the surface area. This reduction in air friction, or drag, allows the drone to withstand heavy winds.
By reducing air resistance, a bird can increase its velocity without expending more energy than is required.
[Image Source: EPFL]
The prototype has a minimum turn radius of 3.9 m with the wings fully extended and 6.6 m when retracted. According to the simulations, the drone would have a minimum speed of 6.3 m/s with the wings fully extended and 7.6 m/s when folded.
These values are made possible by the feathered structure undergoing a 41 percent reduction in total wing surface area; reducing the drag coefficient by more than 40 percent when retracted. When deployed, the larger surface area has a 32 percent higher lift coefficient.
This isn't the first translation of bird qualities onto robotics. SmartBird is a lightweight drone built by Festo and modeled after a seagull. SmartBird flaps its wings to gain both lift and propulsion while twisting its torso for steering. An interesting idea would be to see these two ideas merged. It could fabricate a complete aerial concept that parallels the qualities of a bird.
Written by Terry Berman