If you're trying to develop new-and-improved forms of underwater propulsion, you could do worse than copying one of the fastest fish in the sea – the tuna. That's what American scientists have done, and they claim that the resulting "Tunabot" can match the swimming speed of the genuine article.
Modelled specifically after the yellowfin tuna and the related Atlantic mackerel, the device was created via a collaboration between mechanical engineers at the University of Virginia and Harvard University. Significantly scaled down from the actual tuna, which can get up to 7 feet (2 m) long, it's approximately 10 inches (25.5 cm) in length.
When the Tunabot was tethered in flow tanks at both universities, laser-based fluid-motion analysis showed that it was capable of swimming at a maximum speed equivalent to that of a real yellowfin of the same size – about four body lengths per second.
Additionally, it did so by rapidly bending its flexible body in a manner much like that of a living tuna. The water-tank tests suggested that if equipped with a 10 watt-hour battery pack, the robot could thus swim at a speed of 0.4 m/second (1.3 ft) for a distance of about 9 km (5.6 miles). If the speed were increased to 1 m/sec (3.3 ft), the range would drop to around 4 km (2.5 miles).
And while there might indeed be uses for a robotic tuna – such as the US Department of Homeland Security's BIOSwimmer underwater surveillance robot – it is hoped that the Tunabot research may more generally lead to faster, more efficient propulsion systems for both manned and unmanned underwater vehicles. In fact, the scientists plan on ultimately producing a system that outperforms an actual tuna.
"We don’t assume that biology has evolved to the best solution," says U Virginia's Prof. Hilary Bart-Smith, leader of the study. "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. Our ultimate goal is to surpass biology."
A paper on the project, which is being funded by the US Office of Naval Research, was recently published in the journal Science Robotics. And Bart-Smith, incidentally, previously led the development of a robotic cow-nosed ray.
The Tunabot can be seen in action, in the following video.
Source: University of Virginia