Unique Fleet Of Underwater Vehicles To Gather Elusive Environmental Data

BLACKSBURG, Va., Feb. 14, 2003 – A fleet of miniature underwater vehicles being developed by Virginia Tech researcher Dan Stilwell will enable scientists to gather environmental data off the coast of Virginia and in the Chesapeake Bay.

Stilwell, an assistant professor of electrical and computer engineering, has received a $400,000 Faculty Early Career Development Program (CAREER) Award from the National Science Foundation (NSF) and a $300,000 Young Investigator Program award from the Office of Naval Research (ONR) to support his research.

Stilwell's goal is three-fold: to develop a low-cost miniature autonomous underwater vehicle (AUV), to develop a mathematical theory that describes how AUVs can cooperate, and to deploy a fleet of vehicles that can gather environmental data that otherwise would be impossible to collect.

"One of our field sites is Hog Island Bay off the coast of Virginia. This bay serves as a natural barrier to man-made pollutants," Stilwell said.

Separated from the Atlantic Ocean by barrier islands, Hog Island Bay is the site of a long-term NSF ecological study. However, researchers haven't been able to collect certain critical data about the health of the bay. That data--including dissolved oxygen, which is used to estimate the metabolism of plants and organisms that live in the bay--has proven elusive with traditional collection methods.

"The difficulty is that changes in dissolved oxygen must be measured over periods of one to two hours and across the entire bay," Stilwell explained. This will require several autonomous vehicles working cooperatively--one vehicle acting alone cannot cover the bay quickly enough to collect a scientifically valid sample.

Stilwell's research for both the NSF and ONR is aimed at creating the first miniature AUVs capable of operating effectively as a group. "Cooperation between autonomous vehicles is the one of the major advancements my graduate students and I are pursuing," he said.

Stilwell's ONR project will complement his work for the NSF. At additional field sites on the York River and the Chesapeake Bay, Stilwell plans to develop the capability to take three-dimensional measurements of parameters that vary with time.

"Applications for this technology include rapidly locating and tracking chemical pollutants in the water. Using a fleet of AUVs, we would be able to quickly map a chemical plume, track its progress in real-time, and quickly locate its source," Stilwell said.

One of the important research issues will be to develop the algorithms that enable a fleet of AUVs to cooperatively find and track a plume in real-time.

The two-feet-long cylindrical AUVs under construction in the Autonomous Systems and Controls Laboratory at Virginia Tech will be fitted with sensors for monitoring dissolved oxygen and other environmental parameters, including conductivity, salinity, temperature, and depth.

When on the surface, the AUVs will use geographical positioning system (GPS) for precise navigation. The AUVs also will carry miniature sonar systems to help with navigation and wireless transmitters to send data to one another and to researchers on land.

Other larger AUVs are commercially available, but their size, cost and infrastructure requirements are prohibitive for many applications.

"By producing AUVs that are very small and cost about $2,000 in parts, our AUVs will be suitable for a number of applications that cannot now be addressed with current AUV technology," Stilwell noted. "The idea of a miniature AUV was originally proposed by Carl Wick, a researcher at the U. S. Naval Academy. Dr. Wick designed the prototype miniature AUV on which our original designs where based."

"If we're successful with these experiments in water, we can develop autonomous vehicles that will work cooperatively on land or in the air," Stilwell said. In the air, for example, teams of vehicles could be designed to more efficiently perform surveillance or track plumes of pollutants. Because these AUVs are so inexpensive, they also could be used by the military to seek out and detonate underwater mines.

Stilwell also is developing a robotics curriculum for seniors and first-year graduate students that will emphasize the unique engineering problems associated with underwater robotics. "The design of an underwater robot requires a set of skills that cross traditional department boundaries," Stilwell noted. "A curriculum that combines elements from electrical engineering, ocean engineering, computer science, and other departments does not currently exist."

Last year Stilwell and fellow CAREER award recipient Craig Woolsey of Virginia Tech's aerospace and ocean engineering department helped found the university's Autonomous Underwater Vehicle Team, which will design and build AUVs for a national competition.

For more information about this research, contact Dan Stilwell at (540)231-3204 or email stilwell@vt.edu.