It is this folding and simple reduction of wing span that the team wished to exploit. By having a wing that can easily change size and shape, a drone can adapt to nippy manoeuvres (larger wing span required), or can reduce its drag at high speeds to fly in strong headwinds (short wing span required).
Birds can dramatically alter the shape and size of their wings because they are composed of an articulated skeleton controlled by muscles and covered with feathers that can overlap. Similarly, the presented drone has a wing equipped with artificial feathers that can be folded to actively change the surface. The wing contains two artificial tendons that can either rotate or straighten the front edge of the wing, thus splaying or storing the feathers. By enabling the drone to reduce its wingspan, the surface area is decreased by 41%, thus significantly reducing drag giving the possibility to fly against strong headwinds. On the other hand, when the wing is fully deployed, the drone can perform turns that are 40% sharper. Since the two foldable wings act independently of each other, the mechanism can also be used to control roll eliminating the need of additional ailerons with advantages in terms of reduced weight and mechanical complexity.
This new advent means that the drones of the future may not only manoeuvre like birds, but may also look like them too!
M. Di Luca, S. Mintchev, G. Heitz, F. Noca, and D. Floreano, Bio-inspired morphing wings for extended flight envelope and roll control of small drones, Journal of the Royal Society, Interface Focus, 16 December 2016. DOI – http://dx.doi.org/10.1098/rsfs.2016.0092