Robots that can swim underwater are nothing new. For instance, Carnegie Mellon fitted its earlier this year to give it aquatic capabilities. But few can do so with the grace, speed and effortlessness of a real-life fish. And it’s not that scientists have avoided trying to create a robot that can do just that, but the exact way fish swim faster or slower is something that has proved elusive.
Marine biologists have known for a while that the secret lies somewhere in the way they can alter the rigidity of their tails. The problem is that it’s difficult to measure that while a fish swims. However, using a combination of fluid dynamics and biomechanics, say they’ve derived a formula that not only provides an answer to that question but also allows a robot with a specially designed tail to be nearly as good as its natural counterpart at speeding up and slowing down in water.
When they applied the formula to a tuna-like robot they built, they found it could swim at a greater variety of speeds using almost half as much energy as one with a fixed-stiffness tail. If you’re a cyclist, you’ll love this analogy. “Having one tail stiffness is like having one gear ratio on a bike,” Dan Quinn, one of the co-authors of the study, told . “You’d only be efficient at one speed. It would be like biking through San Francisco with a fixed-gear bike; you’d be exhausted after just a few blocks.”
With a tuna-sized machine under their belt, the University of Virginia team plans to scale their tail technology for use on both bigger and smaller robots. They’re also developing one that undulates like a stingray. Their work could one day lead to a class of drones that can quickly travel to a remote location and then slow down to investigate the area. Like an aquatic snakebot, that’s something the Navy could use to inspect their ships for damage.
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