The best human runners specialize — with some devoted to covering ultra-long distances while others focus on lightning speed over a matter of yards.
In the open ocean, though, tuna can do both — as highly efficient swimmers, they’re able to migrate thousands of miles across the Pacific from California to Japan, but when threatened or on the hunt, they’re also among the fastest fish in the water, capable of reaching speeds of nearly 50 miles per hour.
But for scientists, like George Lauder, who hope to better understand how fish move by developing robots to model their underwater “gait,” that flexibility has been maddeningly difficult to capture until now.
The Henry Bryant Bigelow Professor of Ichthyology, Lauder and a team of researchers from the University of Virginia developed “Tunabot,” the first robotic tuna that can accurately mimic both the highly efficient swimming style of tuna and their high speed. The robot is described in a paper published in Science Robotics.
“People have come up with some complicated ways of building fish robots. Some can move pretty quickly, but they take large amounts of power,” Lauder explained. “We wanted to create something that could approximate the energy demands on the fish and move efficiently over a range of speeds.
“It’s like a Porsche going through Cambridge traffic,” Lauder said. “It’s not going 100 miles per hour, but it can go to the track and perform at a high level. Tuna are basically like the Porsche, they’re high-performance fish that have the capability of moving relatively slowly and efficiently, but they’re happy to ramp it up.”
The challenge, Lauder said, was in designing a mechanism that could efficiently convert the rotation of a motor into the side-to-side flapping of a fish tail — and the solution proved to be surprisingly simple.