Researchers from Lund University in Sweden have built a bird-like feathered robotic wing and tested it in a wind tunnel in an effort to work out how to improve the efficiency of flight.
The research has revealed that birds fly more efficiently by folding their wings during the upstroke, a technique that the researchers believe could be applied to drones to increase their propulsive and aerodynamic efficiency.
Christoffer Johansson, biology researcher at Lund University said, “We have built a robot wing that can flap more like a bird than previous robots, and flap in a way that birds cannot do.
“By measuring the performance of the wing in our wind tunnel, we have studied how different ways of achieving the wing upstroke affect force and energy in flight.
The Swedish-Swiss research team constructed the robotic wing to mimic the way a bird’s wing flaps, as well as movement beyond that original motion.
Even precursors to birds – extinct bird-like dinosaurs – benefited from folding their wings during the upstroke, as they developed active flight. Among flying animals alive today, birds are the largest and most efficient. This makes them particularly interesting as inspiration for the development of drones. However, determining which flapping strategy is best requires aerodynamic studies of various ways of flapping the wings.
“Research into the flight ability of living birds is limited to the flapping movement that the bird actually uses. The new robotic wing can be used to answer questions about bird flight that would be impossible simply by observing flying birds.,” Johansson said.
The research explains why birds flap the way they do, by finding out which movement patterns create the most force and are the most efficient.
Previous studies have shown that birds flap their wings more horizontally when flying slowly. Data from the recent wind tunnel testing shows that even though this requires more energy, it is an easier way for birds to create sufficiently large forces to stay aloft and propel themselves. The researchers hope this is something drones can emulate to increase the range of speeds they can fly at.
The results can also be used in other research areas, such as to better understand how the migration of birds is affected by climate change and access to food. There are also other potential uses for drones where these insights can be put to good use, such as using drones to deliver goods.
“Flapping drones could be used for deliveries, but they would need to be efficient enough and able to lift the extra weight this entails. How the wings move is of great importance for performance, so this is where our research could come in handy”, added Johansson.