Fish-inspired robots synchronise movement without any outside control
20 January 2021
The decentralised, autonomous self-organisation and coordination of schools of fish has long fascinated scientists, especially in the field of robotics.
Now, 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 have developed fish-inspired robots that can synchronise their movements like a real school of fish, without any external control. It is the first time researchers have demonstrated complex 3D collective behaviours with implicit coordination in underwater robots.
“Robots are often deployed in areas that are inaccessible or dangerous to humans, areas where human intervention might not even be possible,” said Florian Berlinger, a PhD Candidate at SEAS and Wyss and first author of the paper. “In these situations, it really benefits you to have a highly autonomous robot swarm that is self-sufficient. By using implicit rules and 3D visual perception, we were able to create a system that has a high degree of autonomy and flexibility underwater where things like GPS and Wi-Fi are not accessible.”
The research is published in Science Robotics.
The fish-inspired robotic swarm, dubbed Blueswarm, was created in the lab of Radhika Nagpal, the Fred Kavli Professor of Computer Science at SEAS and Associate Faculty Member at the Wyss Institute. Nagpal’s lab is a pioneer in self-organising systems, from their 1,000 robot Kilobot swarm to their termite-inspired robotic construction crew.
However, most previous robotic swarms operated in two-dimensional space. Three-dimensional spaces, like air and water, pose significant challenges to sensing and locomotion.
To overcome these challenges, the researchers developed a vision-based coordination system in their fish robots based on blue LED lights. Each underwater robot, called a Bluebot, is equipped with two cameras and three LED lights. The on-board fish-lens cameras detect the LEDs of neighbouring Bluebots and use a custom algorithm to determine their distance, direction and heading. Based on the simple production and detection of LED light, the researchers demonstrated that the Blueswarm could exhibit complex self-organised behaviours, including aggregation, dispersion and circle formation.
Each Bluebot implicitly reacts to its neighbours’ positions,” said Berlinger. “So, if we want the robots to aggregate, then each Bluebot will calculate the position of each of its neighbours and move towards the centre. 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.”
The researchers also simulated a simple search mission with a red light in the tank. Using the dispersion algorithm, the Bluebots spread out across the tank until one comes close enough to the light source to detect it. Once the robot detects the light, its LEDs begin to flash, which triggers the aggregation algorithm in the rest of the school. From there, all the Bluebots aggregate around the signalling robot.
“Our results with Blueswarm represent a significant milestone in the investigation of underwater self-organised collective behaviours,” said Nagpal. “Insights from this research will help us develop future miniature underwater swarms that can perform environmental monitoring and search in visually-rich but fragile environments like coral reefs. This research also paves a way to better understand fish schools, by synthetically recreating their behaviour.”
The research was co-authored by Dr. Melvin Gauci, a former Wyss Technology Development Fellow. It was supported in part by the Office of Naval Research, the Wyss Institute for Biologically Inspired Engineering, and an Amazon AWS Research Award.