The central goal of the Duke Robotics Team is to build an Autonomous Underwater Vehicle (AUV) to compete in the annual Office of Naval Research and Association for Unmanned Vehicle Systems International (ONR/AUVSI) Underwater Robotics Competition. Since the purpose of this competition is to encourage innovation and experimentation, Duke Robotics decided to build an entirely new AUV this time around, rather than simply return with the same design year after year. Charybdis is loosely based on the strengths of our old vehicle, Gamera, while reaching new levels in craftsmanship and efficiency.

Charybdis is built around a unique propulsion system comprised of four reversible, propeller-based thrusters. Three of these are mounted around the perimeter of a circular chassis, each facing 120 degrees apart from the other two. By firing these thrusters at the correct ratio, Charybdis can move in any direction without having to turn. The fourth thruster is mounted vertically in a channel that passes through the middle of the vehicle to control up and down motion. This system provides unparalleled precision and agility in an underwater vehicle.

The central thruster channel also provides the inspiration for naming Charybdis. In Greek mythology, Charybdis was the daughter of Poseidon and Gaia until she was turned into a monster by Zeus. He placed Charybdis on one side of the Straight of Messina (opposite the six-headed monster Scylla) where she lived in a cave and sucked water in and out three times a day, forming a violent whirlpool. Charybdis and Scylla were two of the challenges faced by Odysseus in Homer's Odyssey.

Charybdis was designed and constructed with industry-standard components and craftsmanship, as well as an eye for detail and small innovations. A full suite of sensors (altimeter, DVL, pressure sensor, and cameras) and a brand-new streamlined electronics stack are connected to cutting-edge Lithium Polymer batteries with industry standard Subconn connectors. This system is finished out with creative details like a wireless ethernet buoy and the reed switch that serves as an emergency cut-off.

Finally, the software, without which the vehicle would never come to life, was completely overhauled. The operating system on the CPU is a scaled-down version of Slackware 9.1 running the Linux 2.6.6 kernel. High level control uses simple configuration files to initialize vehicle components (such as sensors and propulsion) which generate their own threads. A new waypoint scripting language provides event-based vehicle operation with feedback control. Finally, vision processing routines allow Charybdis to find and identify the target bins in the competition.

Charybdis has generated a large amount of excitement within the Duke community, among our generous sponsors and supporters, and with high school students in Duke's TIP summer program during our outreach initiative. We aim to improve on our 3rd place finish at the ONR/AUVSI compeition from last year (beating out defending champion MIT), and come home 1st out of the field of 20 competing schools. If you would like to get involved with the team or are interested in offering financial or in-kind support, please visit our Contact Page. I'd like to offer a final thanks to our Sponsors because without your generous support we wouldn't have been able to make any of this happen.

Josh Johnston
Class of 2005
President, Duke Robotics Club