Birds fly more efficiently by folding their wings during the stroke, according to a recent study from Lund University in Sweden. The findings may mean that folding the wings is the next step in increasing the propulsion and aerodynamic efficiency of flapping drones.
Even the ancestors of birds – the extinct bird-like dinosaurs – benefited from folding their wings during the stroke, as they developed energetic flight. Of the flying animals alive today, birds are the largest and most efficient. This makes it particularly interesting as an inspiration for drone development. However, determining the best flapping strategy requires aerodynamic studies of the different ways wings flap. So, a Swedish-Swiss research team has built a robotic wing that can achieve exactly that — flap like a bird, and beyond.
“We built a robotic wing that could flap more like a bird than previous robots, but also flap in a way that birds could not. By measuring wing performance in our wind tunnel, we studied the different ways achieving wing stroke affects strength and energy in flight.” , says Christopher Johansson, a research biologist at Lund University.
Previous studies have shown that birds flap their wings more horizontally when they fly slowly. The new study shows that birds probably do this, even though they require more energy, because it’s easier to build up forces large enough to stay aloft and propel themselves. This is something drones can simulate to increase the range of speeds they can fly at.
“The new robotic wing can be used to answer questions about bird flight that would otherwise be impossible simply by observing flying birds,” explains Christopher Johansson. “Research into the ability of live birds to fly is limited to the flapping motion that the bird actually uses.”
Research explains why birds beat the way they do, by discovering which movement patterns create the most force and are most efficient. The findings could also be used in other areas of research, such as better understanding how bird migration and access to food are affected by climate change. There are also many potential uses for drones where these ideas can be put to good use. One area may be the use of drones to deliver goods.
“Drones can be used for deliveries, but they have to be efficient enough and able to lift the extra weight that this entails. How the wings move is of huge importance to performance, so this is where our research can be useful,” concludes Christopher. Johansson.