In the world of underwater robots, new Robofish are a team of pioneers. While most ocean robots require periodic communication with scientist or satellite intermediaries to share information, these can work cooperatively communicating only with each other.




“Underwater robots don’t need oxygen. The only reason they come up to the surface right now is for communication,” Morgansen said. Her robots do not need to come to the surface until their task is complete.



But while other research groups are building fishlike robots, what’s novel with this system is that the robotic fish can communicate wirelessly underwater. Again, Morgansen looked to natural systems for inspiration. The engineers worked with collaborator Julia Parrish, an associate professor in the UW’s School of Aquatic and Fishery Sciences, to record patterns of fish schools’ behavior.

“In schooling and herding animals, you can get much more efficient maneuvers and smoother behaviors than what we can do in engineering right now,” Morgansen explained. “The idea of these experiments (with schools of live fish) is to ask, ‘How are they doing it?’ and see if we can come up with some ideas.”


“The fish that have a strong idea tend to dominate over those that don’t,” Morgansen said. “That has implications for what will happen in a group of vehicles. Can one vehicle make the rest of the group do something just based on its behavior?”


“When you’re underwater you run into problems with not being able to send a lot of data,” Morgansen said. State of the art is 80 bytes or about 32 numbers per second, she said.

The energy required to send the information over long distances is prohibitive because the robots have limited battery power. What’s more, signals can become garbled when they reflect off the surface or off of any obstacles.

Messages were sent between the robots using low-frequency sonar pulses, or pressure waves. The new results showed that only about half the information was received successfully, yet because of the way the Robofish were programmed they were still able to accomplish their tasks. Robots that can independently carry out two simple sets of instructions–swimming in the same direction or swimming in different directions–will allow them to carry out more complicated missions.

Now researchers are using the fish’s coordination ability to do a task more similar to what they would face in the ocean. The Robofish pack’s first assignment, beginning this summer, will be to trail a remote-controlled toy shark.

Further reading: Autonomous Underwater Multivehicle Control with Limited Communication: Theory and Experiment

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