Something’s really fishy...

Researchers at the University of Washington have created three autonomous, fish-like robots that use their fins for propulsion, and communicate wirelessly with one another underwater

MUMBAI MIRROR BUREAU

Boffins in the US have built a breed of autonomous Robofish that can work by cooperatively communicating only with each other – without human intervention.
Over the past five years, Kristi Morgansen – a University of Washington (UW) professor of aeronautics and astronautics – has built three Robofish after studying the way real fish communicate.
The robots were programmed to either all swim in one direction or all swim in different directions – basic tasks that can provide the building blocks for coordinated group movement.
“Underwater robots don’t need oxygen. The only reason they come up to the surface right now is for communication,” Morgansen said, adding that her robots do not need to come to the surface until their task is complete.
In the future, ocean-going robots, she said, could cooperatively track moving targets such as groups of whales, or explore caves underneath ice-covered waters, or even work in dangerous underwater environments.
Morganson was assisted in the study by aeronautics and astronautics students, Daniel Klein and Benjamin Triplet – and Patrick Bettale, an electrical engineering student.

LEARNING FROM REAL FISH
The Robofish, which are roughly the size of a 5-kg salmon, look a bit like fish because they use fins rather than propellers. The fins make them potentially more manoeuvrable and create lower drag than propeller-driven vehicles.
For the wireless communication aspect, Morgansen collaborated with Julia Parrish – an associate professor in the UW’s School of Aquatic and Fishery Sciences – to record patterns of fish schools’ behaviour.
“In schooling and herding animals, you can get much more efficient manoeuvres and smoother behaviours 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 team trained some live fish to respond to a stimulus by swimming to the feeding area. The scientists discovered that even when less than a third of the fish were trained, the whole school swam to the feeding area on cue.
“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 behaviour?”

COMMUNICATING THROUGH SONAR
Beyond finding the optimal way to coordinate movement of the robots, the researchers faced major challenges in having robots transmit information through dense water.
“When you’re underwater you run into problems with not being able to send a lot of data,” Morgansen 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, she said.
Messages were sent between the robots using low-frequency sonar pulses, or pressure waves. The 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.
Now the researchers are using their 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 later this year, will be to trail a remote-controlled toy shark.

Kristi Morgansen uses a remote controller to direct a Robofish. In experiments she programs basic instructions so up to three robots can navigate without human intervention INSET: The fin-propelled, autonomous Robofish designed at the University of Washington