SoFi can swim to depths of 50 feet for 40 minutes. Source: MIT CSAILDespite technological advances in maritime research, challenges remain to study animals in the ocean up close.
MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) has developed a potential solution in a soft robotic fish that can swim on its own untethered alongside real fish in the ocean.
The robot, named SoFi, was tested in the Rainbow Reef in Fiji where it swam to depths of more than 50 feet for about 40 minutes, handling currents and taking high resolutions photos and videos using a fisheye lens.
The soft robot has an undulating tail to control its own buoyancy, allowing it to swim in a straight line, turn or dive up or down. The team also waterproofed a Super Nintendo controller and developed a custom communications system to change the robot’s speed and make specific turns. SoFi is the first robotic fish that can swim untethered in three dimensions for extended periods of time, MIT CSAIL says.
Robert Katzschmann, MIT CSAIL PhD student and lead in the research, tells Electronics360 being untethered is key because it doesn’t hinder the robot to freely explore sceneries without getting entangled or damaging the environment. This is very important when exploring coral reefs or other marine environments as untethered locomotion helps to not harm corals. If the SoFi was tethered, the undulation of the soft fish tail would be less biomimetic in its appearance, he says.
“Also, a tether introduces additional drag that would have to be overcome by the tail actuation of the fish—we do not use thrusters or other rather artificial means of propulsion—so we have to make it work with less propulsive power,” Katzschmann says. “Similarly to flying a drone, the operator keeps the robot within sight and therefore no live video stream from the fish is needed.”
What’s Inside
The soft robot is untethered allowing it to freely roam the ocean. Source: MIT CSAILSoFi has a few on-board sensors for perception, a servo motor and the same lithium-polymer battery found in smartphones. In order to swim, the motor pumps water into two balloon-like chambers in the fish’s tail that operate like a set of pistons in an engine. As one chamber expands, it bends and flexes to one side; when the actuators push water to the other channel, the other one bends and flexes in the other direction.
The entire back half of the fish is made of silicone rubber and flexible plastic. Several of the components are 3D printed, including the head, which houses the electronics. To reduce the chance of leakage, the team filled the head with baby oil, since it will not compress from pressure changes during dives.
The SoFi project is part of MIT CSAIL’s focus on soft robots that are safer, sturdier and more nimble than their hard-bodied counterparts.
SoFi is currently just a research prototype and MIT CSAIL is open to collaborating with biologists or other researchers in studying, observing and interacting with life in the ocean. Katzschmann says there is potential in studying the behavior of marine life over long periods of time without human interference and also if SoFi can influence marine life.
Other potential uses for SoFi could be as an inspection device that can enter small openings and film videos or the creation of robotic swarms that monitor human littering in the ocean or to monitor and detect invaders within guarded waters.
“I could imagine these robots one day leading swarms of real fish toward other areas, either for saving them from oil spills or for guiding them into a fishing net,” Katzschmann says. “These robots could also be used as a network of underwater sensors in order to record oceanic data, including taking small water samples. The fish could also be used for underwater inspection of oil rigs, pipelines and other critical infrastructure.”
