School of fishy little robots

Why have a school of fish when you can have a school of robots?

This is a question recently answered by a team of researchers from Harvard University, who have developed fish-inspired robots – Bluebots – that swim in an independently organised swarm that simulates schooling behaviours. 

According to their paper, published in Science Robotics, Bluebots use a combination of cameras and blue LED lights to recognise where their friends are and synchronise their movements to explore 3D collective behaviour. 

Beyond the adorableness of the 13cm Bluebots (which are based on surgeonfish), this is also the first demonstration of an independent underwater system of robot organisation. Previously, most underwater bots relied on coordination from above-water communication, which limited coordination complexity.

The whole collective, called the Blueswarm, allows for extra research about swarming algorithms, which could improve robot swarms. 

“Our results with Blueswarm represent a significant milestone in the investigation of underwater self-organised collective behaviours,” says Radhika Nagpal, whose lab previously developed termite-inspired robot swarms.

“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.”

This is especially useful for exploring deep parts of the ocean. 

“Robots are often deployed in areas that are inaccessible or dangerous to humans, areas where human intervention might not even be possible,” says author Florian Berlinger. “In these situations, it really benefits you to have a highly autonomous robot swarm that is self-sufficient.”

Having multiple small fish allows the possibility of searching large and inaccessible areas more efficiently. Researchers tested this notion by giving them the task of finding something: they put a red-light stimulus in the laboratory pool for the Bluebots to discover. When the light was detected by a Bluebot it gave off a signal to the other Bluebots, who swarmed around the finder. 

The idea of self-organisation came from large schools of fish that move as a single unit. Swarming and swimming in schools is an ancient trait in fish. 

Fish don’t rely on explicit communication, rather organising themselves based on an implicit coordination taken from visual cues of neighbours. The same idea was used with the Bluebots.

When Bluebots swim within 5m, they detect their neighbours’ lights with two camera “eyes” and organise themselves to move closer or further apart depending on the distance and their programming.

“Each Bluebot implicitly reacts to its neighbours’ positions,” says Berlinger. “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.”

Previous fishbot studies have looked at fishy personalities, using schools to swim efficiently, and at speedster robots – but in each of these the robots were acting alone or in pairs.

The new research demonstrates a complex, seven-member group that work together to move in basically every direction within their 3D space.