Researchers at the University of Virginia School of Engineering have created a robotic fish tail for ultra-fast movement underwater.

The new model combines robotics, hydrodynamics and biomechanics, so the new fish-like robot swims much more efficiently compared to similar robots.

Submersibles are generally designed for one cruising speed and they often cannot sail faster or slower. But the new robot can even be used in multi-speed missions.

Dan Quinn, assistant professor at the University of Virginia’s School of Engineering and Applied Sciences, and his colleagues have figured out how to design variable speed submersibles. The point was to make a fishtail with adjustable stiffness: depending on its level, you can achieve different speeds.

The problem is that there is no known way to measure tail stiffness in swimming fish, so it is difficult to understand how this indicator changes in the natural environment. Quinn and Chung solved this problem by combining fluid dynamics and biomechanics to provide a model of how and why to tune tail stiffness. As a result, they came up with a formula: stiffness becomes higher with an increase in swimming speed squared.

To test the theory, they built a fish-like robot with a programmable artificial tendon to adjust the rigidity of the tail while swimming.

As a result, the robot was able to swim at a wider range of speeds and wasted less energy than robots with fixed stiffness.