In an study to see if animals will react to robotic attempts to interact with them, Swiss researchers have built a robotic fish that can successfully imitate and mingle with zebrafish."We created a kind of 'secret agent' that can infiltrate these schools of small fish," says Frank Bonnet of the Swiss Federal Institute of Technology in Lausanne (EPFL).
EPFL researchers chose the small fish because of their sudden bursts of movement. It's difficult to build a robot that can integrate into a species like zebrafish, which have a deeply developed "," a sensory network evolved to detect the pattern of water movement. This sense is what allows fish like zebrafish to suddenly change directions as a group.
The scientists considered the physical characteristics of zebrafish, such shape, color and stripe when selecting a species to study. Their behavior in schools was also a focus: acceleration speed, linear velocity, distance between individual fish inside the schools, the size of the schools themselves, individual vibrations and motion, and the rhythm at which they move their tails.
Bonnet and his fellow scientists put the robot in an aquarium and let it start interacting with five different schools of zebrafish. At seven centimeters, the robot fish is slightly bigger than a normal zebrafish, but it mimics the fish in other ways. With a swimming mechanism that improved over time, "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."
Scientists have long taken inspiration from animals when building robots. But using a robot to interact with animals can help researchers learn about biology as well as robotics. And for Bonnet and his group at the EPFL, their robots are getting more complex. This is a step up from their last project, which involved building robots to imitate cockroaches.
"Fish are much more complicated animals," says Bonnet. "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."