And Fortune suspects that the study will inspire young engineers to approach mechanical design in novel ways. "Despite the fact that the knifefish break a traditional rule of engineering," says Fortune, "they nevertheless achieve better locomotor performance than current robotic systems."
To conduct its study, the team used a combination of careful observations of the fish, mathematical modeling and an analysis of a swimming robot. Working in his NJIT lab with students and in collaboration with his colleagues at Johns Hopkins, Fortune used slow-motion video to film the fish to study its fin movements: What the videos revealed was startlingly counterintuitive.
"It is immediately obvious in the slow-motion videos is that the fish constantly move their fins to produce opposing forces," says Fortune. "One region of their fin pushes water forward, while the other region pushes the water backward. This arrangement is rather counter-intuitive, like two propellers fighting against each other."
A mathematical model designed by Shahin Sefati, a graduate student at Johns Hopkins and a lead author of the research project, showed that this odd arrangement generates stabilizing forces. But the model also suggested that the opposing forces simultaneously improved the ability of the animal to change its velocity, thereby making the animal more maneuverable. The team then tested this model using a robot in the laboratory of Malcolm MacIver at Northwestern University; the robot mimicked the fish's fin movements.
One exciting implication of study is its possible application to robotics systems, including the design of sophisticated robots and aircraft. Designers and engineers might make simple changes to propulsion systems, such as tilting engines or motors so that some of the thrusts oppose each other. Such an arrangement might waste some energy, but this cost may be more than offset by making a robot or aircraft simpl
|Contact: Tanya Klein|
New Jersey Institute of Technology