A team from the Laboratory of Computer Science and Artificial Intelligence (CSAIL) of the prestigious MIT has shown a fish-shaped soft robot prototype called “SoFi“, which can swim independently with real fish in the ocean.
The team of researchers made the first tests of dives in the Rainbow Reef coral in Fiji. SoFi swam at depths of more than 50 feet for up to 40 minutes at a time, nimbly maneuvering currents and taking high-resolution photos and videos using a fish-eye lens.
Using its wavy tail and a unique ability to control its own buoyancy, SoFi can swim in a straight line, rotate or dive up or down. The team also used a Super Nintendo waterproof controller and developed a customized acoustic communication system that allowed them to change the speed of SoFi and have it perform specific movements and turns.
“As far as we know, this is the first robotic fish that can swim unattached in three dimensions for long periods of time,” says Robert Katzschmann, lead author of the new journal article published in Science Robotics. “We are excited about the possibility of using a system like this to get closer to marine life than humans can do for themselves.”
Side by side like a real fish
The existing autonomous underwater vehicles (AUVs) traditionally operate by being attached to ships or propelled by bulky and expensive propellers. On the contrary, SoFi has a much simpler and lighter configuration, with a single camera, an engine and the same lithium polymer battery found in smartphones.
To make the robot swim, the engine pumps water in two cameras similar to balloons located in the tail of the fish that function as a set of pistons in an engine. As one camera expands, the other bends and flexes; When the actuators push the water into the other channel, it bends and flexes in the other direction.
These alternate actions create a side-to-side movement that mimics the movement of a real fish. By changing its flow patterns, the hydraulic system allows different tail maneuvers that result in a range of swim speeds, with an average speed of approximately half the body length per second.
“The authors show a series of technical achievements in manufacturing, power and water resistance that allow the robot to move underwater without ties,” says Cecilia Laschi, professor of bio-robotics at the Sant’Anna School of Advanced Studies in Pisa. , Italy. “A robot like this can help explore the reef more closely than current robots, both because it can get closer to the reef more safely and because it can be better accepted by marine species.”
The back half of SoFi is made of silicone rubber and flexible plastic, and several components are printed in 3-D, including the head, which contains all the electronic components. To reduce the possibility of water seeping into the machinery, the team filled the head with a small amount of baby oil, because it is a fluid that will not be compressed by pressure changes during dives.
In fact, one of the team’s biggest challenges was getting SoFi to swim at different depths. The robot has two fins on its side that adjust the pitch of the fish up and down. To adjust its position vertically, the robot has an adjustable weight compartment and a buoyancy control unit that can change its density by compressing and decompressing the air.
Do not disturb the other fish
Katzschmann says the team developed SoFi with the goal of being as disruptive as possible in its environment, from the minimum noise from the engine to the ultrasonic emissions of the team’s communications system, which sends commands using wavelengths of 30 to 36 kilohertz.
“The robot is capable of making close observations and interactions with marine life and seems not to disturb the real fish,” says Daniela Rus, CSAIL director, who also collaborated with the research.
As next steps, the team will be working on several improvements in SoFi. Katzschmann plans to increase speed by improving the pumping system and modifying the design of his body and tail. He also plans to use the built-in camera soon to allow SoFi to automatically follow real fish, and build additional SoFis for biologists to study how fish respond to different changes in their environment.
“We see SoFi as a first step to develop almost a type of underwater observatory,” says Rus. “It has the potential to be a new kind of tool for ocean exploration and open new ways to discover the mysteries of marine life,” he concluded.
Robots are growing rapidly in recent years. And this is one among them.