A humanoid robot may have just been granted citizenship status for the first time, but we're still a long way from crossing the uncanny valley to where they blend seamlessly into our society. But apparently fish are easier to fool, since a team from EPFL has successfully integrated a robotic impostor into schools of zebrafish, to the point where the robot could guide the group's behavior.

Fish have inspired robots for years, allowing scientists to measure the acidity or quality of water without disturbing the locals, and teaching us more about how fish move and sense their surroundings in murky waters.

This new robot is more of a social experiment. It was designed to be a "secret agent," integrating with schools of fish to see if it could learn to communicate and move like the real thing, as well as influence the group's behavior. Researchers at the EPFL robotics laboratory have managed to get robots to infiltrate cockroach communities in the past, but trying to do so with fish is a different … well, kettle of fish.

"Fish are much more complicated animals," says Frank Bonnet, an author of the study. "To integrate into an insect community, a robot simply has to emit certain kinds of pheromones. But integrating into a community of vertebrates seems to involve many more criteria, in terms of such things as appearance, movement and vibration."

To help the robot pass the school's entrance exam, the team built it with the same color, shape, proportions and striped pattern as the zebrafish, although at 7 cm (2.8 in) long it's a little bigger than the real thing. To make sure the robot's movements were realistic, the team studied the behavior of the fish, including their linear velocity, acceleration speed, vibration, tail movement rhythm, how big schools get and how far apart individual fish tend to swim.

The robot zebrafish is mounted on a small pole connected to a base sliding along the bottom of the aquarium, which is magnetically hooked up to a little engine that drives around underneath the tank, dragging the robot through the water. Its tail still kicks side to side to give the impression that the robot is swimming, and over time the robot learned from the fish to improve its swimming mechanism.

The team tested the robofish with 10 different schools of four zebrafish in aquariums with mazes of rooms and corridors. They recorded the movements of the school as a whole and individual fish within it, and how well the robot integrated with the animals, and compared the results to schools of five live zebrafish with no robot intruder. Schools with robot fish were found to function essentially the same as entirely-natural ones.

"The fish accepted the robot into their schools without any problem," says Bonnet. "And the robot was also able to mimic the fish's behavior, prompting them to change direction or swim from one room to another."

The results can not only helps scientists study the social interactions of fish, but also how to make bio-inspired robots more lifelike.

The research was published in the journal Bioinspiration & Biomimetics.

Source: EPFL