Robotic tuna moves like the real thing

Robotics researchers at the University of Virginia have created a robotic tuna able to move just like the real thing. The robotic fish is about 14 inches long and can swim at speeds up to 1.5 mph, which is two body lengths per second. One of the critical design features is that the robot tuna can flap its tail nearly as fast as a real tuna, up to seven times per second.

One of the key design features of the robot is its ability to tense and relax the tail joint allowing it to move at different speeds. The design of the tail joint allows the robot to swim at high speeds while simultaneously allowing it to conserve energy. Researchers believe their breakthrough could help improve swimming robots and underwater vehicles.

There are lots of researchers around the world investigating building robotic fish. Researchers on this project say theirs is different because they are studying the physics of real fish rather than simply mimicking the shape. In a real fish, muscles do generate the motion but their ability to adjust how flexible their tail is allows them to swim efficiently.

Fish can control their tail, allowing it to be as flexible as a sheet of paper or as rigid as the limb on a tree. Tuna can control their tail in part thanks to tendons running the entire length of their body. As they apply force to tendons, the tail stiffens, allowing them to swim faster. Researchers on the project emulated the muscle-tendon system using series of springs and motors.

The creation is a simplified robotic fish utilizing high-frequency actuators to approximate motion. A spring system integrated into the robot converts the force of the spring to tail joint stiffness. Robotics investigators are increasingly looking to nature for improvements in the design and function of robots of all shapes and sizes.