Modeling and control of an autonomous underwater vehicle with combined foil/thruster actuators

Abstract

The Sentry AUV represents a radical departure from conventional AUVdesign, particularly with respect to actuation. The vehicle's combinedfoil/thruster actuators have the potential to produce a vehicle bothmaneuverable in the veritcal plane and effcient in forward flight,well suited to survey work over rough topography. Capitalizing onthis; however, requires an understanding of the vehicles dynamics.In this work, we present the development and analysis of an analyticmodel of the Sentry AUV. Our goals were to develop a model sufficientlyaccurate in terms of the mission profile to identify critical vehiclebehaviors influencing successful mission completion. The analyticalvehicle model was developed with structural accuracy in mind, andunder the requirement that it handle a large range of vertical planevelocities.Our primary methodology for analysis was through the design of a linearcontroller, whose behavior was investigated in simulation and asimplemented on a 1/4 scale physical model. Based on decoupled linearizedmodels for near-horizontal flight derived from the full non-linearmodel, classical linear controllers were designed and validated bysimulation and implementation on the physical model. Closed loopsimulations conducted at high angle of attack verified the vehicle'spredicted maneuverability in the vertical plane. Ultimately we determinedthe vehicle's input structure limited the achievable performanceof a classical linear controller.