Charybdis Battles Again

September 1, 2005

This summer, the Duke Robotics Club won 4th place and a $2,000 prize at the International 2005 Autonomous Underwater Vehicle Competition in San Diego, Calif. They won an additional $1,000 for being the “Most Dockable” vehicle at the event, as they were the only team that successfully made contact with a submerged docking station.

“This year’s competition had a very practical slant. The ‘mission’ was more like what a real world application would be,” said club adviser Jason Janet, adjunct associate professor for the Electrical and Computer Engineering Department.

Each team had to complete four tasks: pass through an underwater gate, dock with a light beacon, follow a pipe located on the pool bottom and drop a marker to identify the location of a pipe leak, and then detect acoustic signals in order to surface in a designated recovery zone.

“Ours was the only team to attempt all four parts of the mission and the judges really appreciated that,” said ME Senior Julien Finlay.

Duke’s entry was a souped up Charybdis — the vehicle that won the Most Innovative Design award in last year’s competition but then experienced unexpected performance problems in the final round.

“We were so close to winning last year that we decided to try to fix our performance problems rather than start all over with a new design,” said Peter (Andy) Smith, ’05, who majored in ECE and computer science. Charybdis, a spherical thruster-propelled robotic vehicle, is named after the Greek mythological monster-daughter of Poseidon and Gaia.

The team ironed out several electromechanical problems, solved a heat overload problem, simplified some of the electronics connections, and improved the watertight seal for the thruster system. Still, they left for the competition experiencing difficulties with the Doppler velocity logger — the system that enables the machine to remember where it is in space.

With that problem on their mind, the student team traveled to San Diego a day ahead of time. Unfortunately, only half of their boxes had arrived — and Charybdis was missing.

“So instead of getting rested up and accustomed to the three-hour time change, we spent the day trying to find our missing equipment at the delivery distribution center,” said Finlay. “It was a good thing we were persistent, because the center initially told us our boxes had been sent back to Durham.”

Luck smiled on the team the next day, however. “By talking with students from other universities, we discovered the Doppler logger problem was being caused by the magnet we were using to drop a locator marker,” said Finlay.

Moving the magnet solved that problem and got the team back on track to compete, but didn’t leave them enough time to get an acoustic system detection system working or to fine tune the visual system. Ultimately, Charybdis didn’t perform as well as the team had hoped.

The team was able to find the break in the pipe, but accidentally dropped their locator marker on a dislodged piece of algae instead of the correct location. And because they didn’t have an acoustic detection system, they had to guess about where the recovery zone was and surfaced in the wrong place. But they have new ideas for what to try next year.

“We plan to create a new design for the 2006 competition and we know we need to be able to move through the water much faster, to include an acoustic detection system, and to improve our visual system,” said Finlay.

“Part of what makes the underwater autonomous vehicle project both appealing and challenging for the Duke Robotics club is that students come and go -- seniors graduate and move on and underclassmen join the team and contribute their own ideas,” said Janet. “The Charybdis that competed this year is really the result of several years of effort from many students.”

The following students have worked on Charybdis over the past two years: Tyler Helble ’04 (ECE and economics), Ethan Eade ’04 (computer science and Math), Raul Rodriguez ’04 (ME and philosophy), Shawn Haigh '04 (BME, ECE and economics), Josh Johnston ’05 (ECE and ME), Peter (Andy) Smith '05 (ECE and computer science), Jamaal Brown '05 (ECE and computer science), John Felkins '05 (ECE and computer science), ME seniors Julien Finlay and Brian Hilgeford, ECE senior Vinh Nguyen, BME/EE junior Matt Johnson and ECE/CS sophomore Gareth Guvanasen.

Duke’s sponsors include SAIC, RD Instruments, Tritech International Limited, Deep Ocean Engineering, Subconn, American Standard, Duke Engineering Alumni Association, Global Water Instrumentation and Vortex Holding, LLC.