Underwater Glider Path Planning and Control
Underwater gliders are winged underwater vehicles that modulate their buoyancy to rise and sink. Pitch and roll attitude are controlled by shifting the center of mass relative to the center of buoyancy. By appropriately cycling these actuators, underwater gliders can control their directional motion and propel themselves with great efficiency. Because they use internal actuators, underwater gliders are also extremely robust. The combination of efficiency and robustness enables long-duration, long-distance missions such as persistent ocean sampling and surveillance.
While underwater gliders are intrinsically efficient and robust, performance can be improved by using path planning and control strategies that account appropriately for the vehicle dynamics and the environmental dynamics. Perturbation analysis of glider steady motions indicates that the flight path angle and speed remain constant during a steady turn, to first order in turn rate. Thus, a glider that is trimmed to some optimal flight condition such as minimum drag or best speed over ground maintains that condition even while turning. As a result, for a vehicle operating in still water, some well-known optimal path planning strategies are immediately applicable.
While underwater gliders were conceived as deep ocean profilers, an application where currents are often negligible, there is interest in operating gliders in littoral regions where flows are more significant. In this scenario, path planning and control is a bit more challenging. The seminar will begin with a brief review of the dynamics of underwater gliders and some relevant optimal path planning methods. The speaker will then describe some recent extensions of these methods that are appropriate for gliders operating in dynamic environments.
Craig Woolsey an Associate Professor and the Assistant Department Head for Graduate Studies in Virginia Tech's Aerospace and Ocean Engineering Department. Dr. Woolsey is the founding Director of the Virginia Center for Autonomous Systems (www.unmanned.vt.edu), an interdisciplinary research center which includes more than thirty faculty members from four Virginia Tech colleges. The center promotes autonomous systems research activities that span every domain: water, land, air, and space. Member research activities range from fundamental control and estimation theory to platform development to applications for science, security, and commerce. The principal aim of Dr. Woolsey's research is to improve performance and robustness of autonomous vehicles, particularly ocean and atmospheric vehicles. The theoretical focus is nonlinear control, particularly energy-based methods for mechanical control systems. Dr. Woolsey is a past recipient of the NSF Career Award and the ONR Young Investigator Program Award, as well as the SAE Ralph R. Teetor Educational Award.