The Amazon black ghost knifefish is a tropical fish known for its impressive maneuvering capabilities in the water. Researchers from the Northwestern University have designed a new type of underwater robot inspired by the movements of the black ghost knifefish.
Unlike most fishes, the black ghost knifefish can transition from forward to backward movement and upward to downward movement in the blink of an eye. This impressive maneuverability has prompted scientists to develop a new type of robot that can emulate the movements of the knifefish. The black ghost knifefish owes its maneuverability to a ribbon-like fin located on the underside of the fish. Moreover, this type of fish is also considered as a "weakly electric fish," which means that it can use a weak electrical field to locate its prey even in complete darkness.
The robot was designed using data gathered from computer simulations showcasing the extreme maneuverability of the black ghost knifefish.
The research team was spearheaded by Northwestern University associate professor of mechanical and biomedical engineering Malcolm MacIver. The team published its findings at the Journal of the Royal Society Interface.
MacIver is considered as an expert on the locomotive capabilities of the black ghost knifefish. He has also lent his technical expertise as a consultant for the TV show Caprica and the movie Tron: Legacy.
MacIver and his team have christened their underwater robot as the GhostBot. The endeavor started when Oscar Curet, a graduate student from Northwestern University and one of the study's co-authors was impressed after observing the sudden vertical movements of a black ghost knifefish in a tank.
"We had only tracked it horizontally before," said MacIver. "We thought, 'How could it be doing this?'"
The team then discovered that the fish uses one motion wave that travels across the central ribbon-like fin to move forward or backward. To move upward and downward, the fish used two wave motions that originate from both ends of the fish. The two motion waves then meet at the center propelling the fish up or down.
"It's interesting because you're getting force coming off the animal in a completely unexpected direction that allows it to do acrobatics that, given its lifestyle of hunting and maneuvering among tree roots, makes a huge amount of sense," said MacIver.
After completing the computer simulations, the team then hired the firm Kinea Design to help them design and build the GhostBot. To build the current version of the robot, Kinea Design and the Northwestern University team used 32 motors to control a central fin. The central fin contains 32 individual rays that provide the robot with 32 degrees of freedom.
"It worked perfectly the first time," MacIver said. "We high-fived. We had the robot in the real world being pushed by real forces."
