Engineers Build First Robotic Fish to Keep Pace with a Tuna

Researchers hope to develop faster, more efficient propulsion systems for manned and unmanned underwater vehicles.
Loukia Papadopoulos

Mechanical engineers at the University of Virginia, in collaboration with biologists from Harvard University, have built the first robotic fish that can imitate the speed and movements of a yellowfin tuna. The research is an attempt to understand the physics of fish propulsion.


Next-generation of underwater vehicles

The robot is called the 'Tunabot,' and the work could eventually lead to the next generation of underwater vehicles. "Our goal wasn't just to build a robot. We really wanted to understand the science of biological swimming," said Hilary Bart-Smith, a professor in UVA Engineering's Department of Mechanical and Aerospace Engineering.

"Our aim was to build something that we could test hypotheses on in terms of what makes biological swimmers so fast and efficient."

In order to achieve this, the team first looked at the swimming dynamics of yellowfin tuna and mackerel. Then, Bart-Smith and her team, research scientist Jianzhong "Joe" Zhu and Ph.D. student Carl White, engineered a robot fish that moved like a fish underwater at nearly equivalent speeds and compared it to real fish.

"There are [a] lot of papers on fish robots, but most of them don't have much biological data in them. So I think this paper is unique in the quality of both the robotic work and the biological data married together into one paper," Lauder said.

"What is so fantastic with the results we are presenting in the paper are the similarities between biology and the robotic platform, not just in terms of the swimming kinematics, but also in terms of the relationship between speed and tail-beat frequency and energy performance," Bart-Smith said.

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"These comparisons give us confidence in our platform and its ability to help us understand more about the physics of biological swimming." 

The Tunabot is an eyeless, finless replica fish that is roughly 10-inches long. The robot features a fishing line tether to keep the robot steady, and a green laser light to cut across its midline.

Mimicking real tuna fish

Tunabot is built in a way that, as the current of water speeds up, its tail and body move in a rapid bending pattern. This mimics the way a real yellowfin tuna swims.

"We see in the fish robotics literature so far that there are really great systems others have made, but the data is often inconsistent in terms of measurement selection and presentation. It's just the current state of the robotics field at the moment. Our paper about the Tunabot is significant because our comprehensive performance data sets the bar very high," White said.

Lauder praises the relationship between biology and robotics. "One reason I think we have a successful research program in this area is because of the great interaction between biologists and roboticists," said the researcher,

Each discovery in one branch informs the other in an educational feedback loop.

"We don't assume that biology has evolved to the best solution," Bart-Smith said.

"These fishes have had a long time to evolve to a solution that enables them to survive, specifically, to eat, reproduce, and not be eaten. Unconstrained by these requirements, we can focus solely on mechanisms and features that promote higher performance, higher speed, higher efficiency."

The researchers want to eventually surpass biology. Lauder states, "Our ultimate goal is to surpass biology. How can we build something that looks like biology but swims faster than anything you see out there in the ocean?"

Their peer-reviewed paper was published in the journal Science Robotics.

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