A Surfeit of Eels

For centuries, schoolchildren have recited the tale of the demise of England's King Henry I, a cruel medieval monarch (blinded one kinsman, imprisoned another for 28 years) who died in a wretched state (so we're told) after dining on "…a surfeit of eels of which he was inordinately fond" thus getting his in the end. For many of us, King Henry and his plate of boiled lampreys is the extent of our knowledge about eels.

Researcher Joseph Ayers at Northeastern University is about to change all that. Henry didn't eat eels; he ate lampreys, a secretive (but apparently tasty) eel-like creature long confused with eels, but actually a cyclostome with some interesting and useful properties. Lampreys swim by rhythmic undulations of their bodies resulting from waves of contractions down their bodies occurring out of phase. This phase delay is independent of frequency, so the lamprey's body contains a single wavelength of oscillation at any given time, and thus always maintains an S-shape during swimming. Speed is proportional to the frequency of this wave, and can vary by an order of magnitude. Lampreys can even swim backward. Ayers is building an autonomous robotic lamprey that can do the same thing.

Ayers is not new to this. He's been building robotic lobsters for years, and he's basing his lamprey's technology on those. "From my perspective, the fact that we can build a family of robots based on a common underlying controller technology is the essence of biomimetics," he says. Employing biomimetic neurotechnology - i.e. mimicking nature in technology -Ayers is using an artificial muscle material to control the movement of his lamprey's spinal cord. It comes complete with an onboard compass, a pitch-and-roll inclinometer, and will soon incorporate a sonar altimeter as well as a forward-looking sonar. A library of behavioral sequences is based on reverse-engineering command sequences from films of behaving lamprey.

"Now we're almost to the point where theoretically we could begin building whole platoons of robotic lampreys and putting them on operational maneuvers in the water," says Dr. Joel Davis, manager of the project in ONR's Cognitive, Neural, and Biomolecular S & T Division. "A robotic lamprey is ideal for stealthy underwater search and identification missions."

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