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

Abstract

The Sentry AUV represents a radical departure from conventional AUV design, particularly with respect to actuation. The vehicle's combined foil/thruster actuators have the potential to produce a vehicle both maneuverable in the veritical plane and efficient in forward flight, well suited to survey work over rough topography. Capitalizing on this; however, requires an understanding of the vehicles dynamics. In this work, we present the development and analysis of an analytic model of the Sentry AUV. Our goals were to develop a model sufficiently accurate in terms of the mission profile to identify critical vehicle behaviors influencing successful mission completion. The analytical vehicle model was developed with structural accuracy in mind, and under the requirement that it handle a large range of vertical plane velocities, Our primary methodology for analysis was through the design of a linear controller, whose behavior was investigated in simulation and as implemented on a 1/4-scale physical model. Based on decoupled linearized models for near-horizontal flight derived from the full non-linear model, classical linear controllers were designed and validated by simulation and implementation on the physical model. Closed loop simulations conducted at high angle of attack verified the vehicle's predicted maneuverability in the vertical plane. Ultimately we determined the vehicle's input structure limited the achievable performance of a classical linear controller.