"Efficient Motion Control for Underwater Gliders"

Craig Woolsey, Department of Aerospace and Ocean Engineering, Virginia Tech

An underwater glider is a winged autonomous underwater vehicle which modulates its buoyancy to rise or sink. It uses servo-actuators to shift the center of mass relative to the center of buoyancy in order to control its pitch and roll attitude. By appropriately cycling these actuators, an underwater glider can control its directional motion and propel itself with great efficiency. Applications include long-term, ocean basin-scale oceanographic sampling and persistent littoral surveillance. The presentation will describe an underwater glider motion control system that is intended to enhance the vehicle’s locomotive efficiency by reducing the energy expended by vehicle guidance and control. The presentation will begin with a brief review of a multi-body dynamic model for a generic underwater glider. The speaker will then present an approximate analytical expression for steady turning motion obtained through regular perturbation theory. Using these steady turn solutions, including the special case of wings-level gliding, one may construct feasible paths for a glider to follow. Because the turning motion results are only approximate, however, and to compensate for model and environmental uncertainty, one must incorporate feedback to ensure convergent path following. Since the resulting feedforward/feedback motion control system relies heavily on stable, steady motions, it is intrinsically efficient. Moreover, the nature of the steady turn approximations suggests a method for nearly energy-optimal path planning. The presentation will describe the development and numerical implementation of this motion control system for the generic underwater glider model, as well as plans for an experimental implementation on a Seaglider AUV.

The principal aim of Dr. Woolsey’s research is to improve performance and robustness of autonomous vehicles, particularly ocean and atmospheric vehicles. In 2002, Dr. Woolsey received the NSF Career Award and the ONR Young Investigator Program Award to support research and education activities related to nonlinear control of ocean and atmospheric vehicles. He was named a Virginia Tech College of Engineering Faculty Fellow in 2003 and received the SAE Ralph R. Teetor Educational Award in 2008. Dr. Woolsey is the founding Director of the Virginia Center for Autonomous Systems, an interdisciplinary research center which includes more than thirty faculty members from four Virginia Tech colleges. The center facilitates interdisciplinary research in autonomous systems technology, hosting research activities that span every application domain: water, land, air, and space. VaCAS member research activities range from fundamental control theory to vehicle design and development to applications for science, security, and commerce.

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