In experiments carried out in a water tank and at Lake Geneva, a team led by Raphael Zufferey, an assistant professor of mechanical engineering at MIT, identified combinations of wing size, flapping frequency, and tail angle that enable the robot to smoothly transition from swimming to flying.
The best results came with medium-size wings that were flexible enough to minimize flapping amplitude in water and also firm enough to keep the robot aloft in the air. The speeds and flapping frequencies were similar to those used by actual birds, and a pitch of 70 degrees—a relatively steep angle—allowed the robot to make the leap from water to air. Interestingly, although many diving birds paddle their feet to help them take off from the water’s surface, the team found that the bot didn’t need feet at all.
The engineers’ results could help pave the way for a new class of drones and vehicles that could fly to and sample from aquatic regions too dangerous for traditional vessels to access.
“Our dream vision is for oceanographers, marine biologists, and members of coastal communities to launch this robot from a boat, or from shore, and it would fly close to the area of interest, such as an iceberg or a port facility, or over a pod of whales,” says Zufferey. “It would dive into the water to take a measurement or collect a sample, and fly back to deliver the data at a fraction of the cost of traditional methods. Then it could go back out to dive for more.”