The animal kingdom is full of inspiration for robotics – just ask the creators of SALTO, Robirds, MuddyBot, WildCat, Octobot, or EPFL's robo-croc. Now, engineers at Caltech and the University of Illinois at Urbana-Champaign (UIUC) have developed the Bat Bot, a robotic bat with soft, flappable wings that could not only make for a safer alternative to keeping drones aloft with spinning blades, but also teach scientists more about the mechanics at work in natural bat flight.
It's hard to tell from fleeting overhead silhouette in the dark, but bats make use of a complex musculoskeletal system to perform the aerial acrobatics they're capable of. By twisting the joints at its shoulders, elbows, wrists and legs, a bat can change the shape of its flexible wings to move in over 40 rotational directions, enabling it to make swift turns and dives.
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Weighing just 93 g (3.3 oz) and sporting a wingspan of about 0.3 m (1 ft), the Bat Bot mimics the flight mechanisms of its natural counterpart, driven by a small onboard computer and a series of sensors that allow it to fly autonomously.
"Our work demonstrates one of the most advanced designs to date of a self-contained flapping-winged aerial robot with bat morphology that is able to perform autonomous flight," says Alireza Ramezani, one of the researchers on the project.
But recreating the wings themselves proved a challenge for the team. The thin, flexible wings of a bat change shape constantly during flight – not just to help the animal steer, but to improve the efficiency of each flap of its wings. When it pushes downwards, the wing membranes catch a pocket of air, and at the bottom of the arc, the membranes snap back to their original position, releasing the trapped air as a gust that boosts the bat's thrust.
The researchers weren't able to find an existing material that was stretchy enough to recreate bat wings, so they developed their own silicone-based membrane measuring just 56 microns thick to do the job. With the help of that air pocket, flapping a wing made of this membrane should require much less energy than the methods existing drones use to stay in the air, and these soft-winged Bat Bots could also be useful in tight areas, where sharp, spinning rotors could injure people or damage objects.
The research was published in the journal Science Robotics and the Bat Bot can be seen in action in the video below.