Robotic fish mimic behaviors of real fish swarms

19 Jan 2021

The Bluebots can autonomously synchronize their movements and can signal when to disperse, aggregate, and form a circle. The Bluebots are equipped with three LED lights and two cameras to have them navigate. (Image credit: Self-organizing Systems Research Group)

Schools of fish use synchronized behaviors to help them find food and avoid danger, like predators. Rather than follow a leader, fish use implicit coordination where individual fish make decisions based on what they see their neighbors doing. To learn more about this behavior, a team of researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Wyss Institute for Biologically Inspired Engineering developed robotic fish that can autonomously synchronize their movements like a real school of fish.

The robotic fish swarm, dubbed Blueswarm, can navigate 3D spaces, like water, unlike previous robotic swarms that operate in two-dimensional due to challenges with sensing and locomotion. To overcome these issues, the individual robotic fish, known as Bluebots, are equipped with blue LED lights that help them communicate with other bots using a vision-based coordination system developed by researchers. Each both is equipped with two cameras and three LED lights. The fish-lens camera finds the LED lights of other Bluebots and uses a custom algorithm to determine their distance, direction, and heading. With this system, the robotic fish can signal when to disperse, aggregate, and form a circle.

“Each Bluebot implicitly reacts to its neighbors’ positions,” said Florian Berlinger, a Ph.D. Candidate at SEAS and Wyss and first author of the paper. “So, if we want the robots to be aggregate, then each Bluebot will calculate the position of each of its neighbors and move towards the center. If we want the robots to disperse, the Bluebots do the opposite. If we want them to swim as a school in a circle, they are programmed to follow lights directly in front of them in a clockwise direction.”

For testing, researchers simulated a search mission using a red light in the tank. The Bluebots used the dispersion algorithm to spread out across the tank until one came close enough to the light source to find it. Once it was detected, the bot’s LED flashed, triggering the aggregation algorithm in the rest of the Blueswarm. This causes all the robots to aggregate around the signaling robot.

Researchers believe Blueswarm will not only help them better understand the behaviors of fish schools, but it can also help them monitor and search in visually rich but fragile environments like coral reefs. These areas are hard for humans to get to, and they’re often out of reach for GPS and WiFi-based systems.