Your drone can fly, but can it walk? That’s where RAVEN stands out. This experimental winged drone has little mechanical legs that let it walk, jump over obstacles and leap quickly into the air.
Engineers from Switzerland and the U.S. drew inspiration from bird anatomy when building RAVEN (Robotic Avian-inspired Vehicle for multiple Environments). Birds can transition seamlessly between walking on land and flying through the air, and the researchers wanted to see if birdlike legs could help unmanned aerial vehicles do the same.
While fixed-wing aircraft are highly efficient at flying forward, they lack the ability to take off and land vertically, like drones do, without a runway or launcher. That limits their applications. RAVEN’s two birdlike legs potentially make it possible to deploy traditional fixed-wing aircraft in complex, tough-to-access terrain that isn’t accessible to winged drones.
Birds’ ability to combine aerial and terrestrial movement “allows them to access places that humans cannot easily reach,” Won Dong Shin, a doctoral candidate at Switzerland’s Ecole Polytechnique Federale de Lausanne who designed the drone legs, noted in an interview. “This inspired me to consider the potential of a bird-like robot in various fields, particularly for delivery and search-and-rescue missions.”
The team, which included scientists from the University of California Irvine’s Neuromechanics Lab, details its research in a paper out last week in the journal Nature.
Looks Like A Bird, Flies Like A Bird
RAVEN not only mimics a bird’s behavior, but resembles one in design. It has splindly legs ending in claw-like “feet” with power-amplifying ankle joints that allow for fast acceleration and taking off at the desired pitch angle. For extra realism, the robot’s “face” features an appendage that looks like a beak, lending it a level of cuteness not characteristic of your average drone. The avian-inspired gadget has a wingspan of 3.25 feet and weighs about 1.4 pounds. Shin finds birds fascinating and often films the crows that frequent campus. His footage has proved valuable in hatching RAVEN.
“I specifically focused on how crows took off in different situations, such as on flat ground, from branches, near cliffs and more,” he said. “What I consistently observed was that they always jumped to initiate flight, even in situations where they could have used only their wings.”
Jumping to take-off could prove especially valuable to RAVEN when locating people in peril or assessing hazardous situations. “Once the mission is complete, the robot could return to the base or another target area without the need for a runway or launcher by simply utilizing its jumping take-off capability,” Shin said.
It’s already possible to purchase fully autonomous, VTOL (vertical take-off and landing) fixed-wing drones, but adding legs marches the vehicles into a new frontier.
Designing lightweight robots with multifunctional legs did pose challenges in terms of integration and control, as the legs add extra payload during flight. However, the research also shed light on the energy efficiency of both birds and drones, Dario Floreano, a roboticist and director of the Laboratory of Intelligent Systems at Ecole Polytechnique Federale de Lausanne, said in a statement.
“These results,” Floreano said, “represent just a first step towards a better understanding of design and control principles of multimodal flying animals and their translation into agile and energetically efficient drones.”
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