UBC Reports | Vol. 48 | No. 12 | Oct. 10, 2002

Is That a Fin in the Water?

Robo-ray points the way to better underwater propulsion

By Michelle Cook

Don’t be alarmed if you spot something fishy in the basement of the Hennings Building. It’s just Robo-Ray, a robotic fin built by a team of UBC Engineering Physics undergraduates looking for a better method of underwater propulsion.

Renee Boileau, Lilian Fan and Tim Moore created Robo-Ray last year. The little electromechanical fin won the Engineering Physics Dept. prize for top senior project but its potential to influence future submersible designs is what has really sparked interest.

“What we were trying to do was find a way to move under- water that is more efficient than a propeller,” says Boileau. “The ray fish is flat and skinny and doesn’t carry a lot of energy but it can move fast. It’s incredibly powerful and graceful, and we were looking for a way to mechanize a robot that would swim through the water with similar grace.”

By mimicking the flapping and rippling movements, called rajiform motion, that rays use to swim, it may be possible to design more flexible, energy-efficient unmanned submersibles for use in oil rig inspections, ocean floor surveys and even wildlife conservation activities, Boileau explains.

The team’s choice of fish stemmed, in part, from a project done by some Physics students and, in larger part, from Boileau’s long-time fascination with rays - something she acquired from watching ocean researcher Jacques Cousteau on television.

Using resources in the Engineering Physics Project lab, Boileau along with Moore, an aspiring naval architect, and Fan, the team’s electrical whiz, began experimenting with cables, motors, gears and pulleys to re-create a fin.

“It got very bulky very quickly because rays have many bones,” says Boileau, who took a zoological physics course to help understand a ray’s physiological structure.

The team’s breakthrough came when Fan found an unusual type of wire while surfing the Web. Called Shape Memory Alloy, the wire’s properties allow it to contract when heated - perfect for mimicking the muscles of a swimming ray.

The group fitted a fin-shaped piece of yellow sailcloth with a series of shape memory wires, and ran electricity through them in a timed sequence to produce the flapping motion of a ray on the move.

Robo-Ray was born.

A big challenge was getting the fin to “behave” by controlling the wires’ shape and their heat up/cool down rate, says Fan. But the bigger question was: could Robo-Ray swim?

The team took it to the B.C. Research Inc. 66-metre tow tank on campus and released it.

It took to water, well, like a fish.

Although the members of Team Robo-Ray all graduated in spring 2002, the trio plans to continue working with current undergraduates to build a more complex model with better propulsion. As for Robo-Ray, it’s still lurking somewhere in the depths of the Hennings Bldg.