1 April 2002
Gaining control over unmanned vehicles
Blacksburg, Va.—Think about the possibilities for unmanned flight above and beneath the sea. Imagine an unmanned airplane taking off on a reconnaissance mission, snapping photographs as ordered. It senses an antiaircraft missile coming and takes evasive action. Or suppose an unmanned submarine goes out to sea to track the boundaries of El Niño.
Virginia Tech’s Craig Woolsey will get a chance to help improve the maneuverability, robustness, and reliability of underwater, air, and space vehicles after garnering a $375,000 National Science Foundation (NSF) Faculty Early Career Development Program Award and a $300,000 Office of Naval Research (ONR) Young Investigator Award to study the design of advanced controls and control mechanisms.
A number of unmanned vehicles, such as the U.S. Air Force’s Predator aerial vehicle and underwater exploratory vessels, perform well in limited maneuvers with humans controlling them from the ground or from ships, Woolsey said.
Such vehicles as the Predator and an unmanned sub would have to use sophisticated control devices and advanced control algorithms—the muscles and brains of any unmanned vehicle—in order to perform complex maneuvers, Woolsey said. His NSF and ONR projects will extend methods of advanced control design to underwater vehicles by incorporating the effects of lift, drag, and other fluid forces.
"Lift—the force that keeps an airplane in the air, for example—is an important consideration for air and ocean vehicles and even some space vehicles," Woolsey said.
Woolsey is building a spherical underwater vehicle with internal rotors. These rotors are like the mechanisms used in many spacecraft to control where the spacecraft points, he said. Researchers will test the vehicle in a water tank.
"As a first step, we’ll program the vehicle and have it perform maneuvers similar to those of an unmanned spacecraft," Woolsey said. "The next step will be to add a streamlined hull and a propeller and control how the vehicle swims." Woolsey is also exploring moving masses for underwater vehicle control.
One of the goals of his project is to find ways to perform successful maneuvers with most of the controls inside the vehicle. "In the ocean, external controls such as propellers and rudders are subject to corrosion and biological fouling and unusual problems like seaweed," he said.
For unmanned ocean vehicles to operate on their own for long periods, researchers must protect their controls mechanisms, just as they protect the controls of spacecraft from intense forces and heat when reentering the atmosphere. The devices and control strategies Woolsey is developing can work in both of these applications.
Another goal is to design controls that will enable the underwater vehicle to move at a low velocity or even hover without disturbances from waves or currents throwing it off track. "For instance," Woolsey said, "imagine an unmanned submersible that could find an underwater minefield on its own, then hover at the mines and plant detonators to clear the area for ship passage."