Scientists regularly try to adopt certain technical solutions from nature, because they are ideal for performing their functions, although reproducing and scaling them can be difficult. For example, drones could borrow from birds’ leg use and structure to be more energy efficient during takeoff and landing. Scientists from Switzerland reproduced this practice in a drone model with “chicken legs”, and it paid off.
Image source: EPFL
This may seem strange to some, but most birds walk more than they fly. Their legs allow them to search for food, move on the ground, stay on branches and jump during take-off, which makes starting conditions easier. The legs also soften contact with the support when landing. Scientists at the École Polytechnique Fédérale de Lausanne (EPFL) have, after extensive bird observation, created the RAVEN drone, which has a fixed wing and propeller, but legs capable of a range of actions.
The drone’s wingspan reaches 1 m, and its body length is 0.5 m. The drone covers a distance of 1 m in about 4 seconds. Its legs help it jump over gaps 12 cm wide and jump onto obstacles 26 cm high. To take off in a jump, the drone can jump about 0.5 m and reach a speed of 2.2 m/s. With a mass of 620 g, the “foot drive” weighs 230 g – more than a third of the drone’s weight. The scientists were faced with the task of finding out the effectiveness of using legs in comparison with flights and take-offs without jumping. Maybe these legs are not needed at all to sacrifice a whole third of the drone’s mass?
Experiments have shown that flight after a jump is more stable and therefore preferable to taking off from a standstill. Also, the presence of “legs” ensures take-off and landing from a very short runway without the need for propellers and horizontal engines. In general, for the take-off task, a jump turned out to be 10 times more energy efficient than getting up from a standstill. The drone also consumed significantly less energy if it needed to move over the ground to another place than it would have done as a result of short flights. Finally, scientists are convinced that even simple jointed fingers are preferable to their absence. Thanks to its toes, the drone maintained its balance when walking and jumping.
Subsequent work on the RAVEN drone will be equipping it with cameras to estimate distances, which is necessary when landing on its feet, as well as work on the wings – the ability to fold them for passage in narrow places and transition to flight with wing flapping.