Some fish are almost impossible for scientists to observe: the Greenland shark, which can live for more than 400 years, was caught on camera for the first time this month. Tracking marine animal can be complex but robotics may make getting close to them easier.
The latest fish-monitoring creation is a fish-shaped rubber and plastic robot from the Massachusetts Institute of Technology. Called SoFi, the fish is controlled by a Super Nintendo controller and has been used to swim alongside fish in Fiji’s Rainbow Reef.
“Current robotic prototypes do not provide adequate platforms for studying marine life in their natural habitats,” write adacemics from MIT’s Computer Science and Artificial Intelligence Laboratory in a new research paper. Existing underwater robotics contain propulsion systems that “systems generate substantial turbulence” and may scare the animals they are observing, they say.
So, to get around the problems they created SoFi. “A diver can direct the fish by sending commands such as speed, turning angle, and dynamic vertical diving,” they write. The computer scientists explain that their robo fish can swim without being tethered to a motor for a maximum of 40 minutes. During this time it’s possible for SoFi to dive to 18 metres. The researcher behind the work say the rubber fish is essentially a “mobile underwater observatory”.
Within the silicone rubber shell there’s a buoyancy sensor, DC motor, a receiver that can talk to the controller, and a displacement pump that allows its tail to move. The motor pumps water into chambers in the robotic fish’s tail, which then force it out to move forward. There’s also a fish-eye camera that is used for capturing images and video of the robot’s surroundings.
A diver close to the artificial fish is able to control its movements using the Nintendo controller. The gamepad is housed in a oil-filled rigid outer shell, which allows it to handle the pressure of deeper water. It issues ultrasonic sounds that are read by a Raspberry Pi and then amplified so they can reach the robot.
During tests in Fiji’s coral reefs the man-made fish swam an average of 296.8m in a straight line on each dive and didn’t scare away other animals around it. Overall, six tests of the robot were completed in the Somosomo Strait in Taveuni and the diver could be around 10 metres away from where it was swimming. If the signal between the controller and the fish is lost then the creature goes into a dormant state and floats in the water.
“Multiple fish swim parallel to the robot a few centimetres below it and also pass a few centimetres in front of its lens,” the researchers write. “The fish did not appear to change their swimming trajectory as SoFi approached them in these cases, suggesting that SoFi has the potential to integrate into the natural underwater environment.”