Modeling and Control of the MARES Autonomous Underwater Vehicle

In this work, we address the modeling and control problems in the domain of underwater vehicles. We focus on a prototype of an autonomous underwater vehicle. Although the work presented here is applied to a particular vehicle with four controllable degrees of freedom, the method may be easily extended to several submerged bodies. In the engineering area, modeling of systems is done frequently, as it yields a mathematical translation of their behavior. Since models can become, an important tool to solve problems related to its motion or even to the design of controllers, we obtain a model with six degrees of freedom for such a vehicle. Robust control of underwater vehicles is an area in which many efforts were applied over the last two decades. However, due to nonlinear dynamics, it may be hard to design robust controllers that yield the expected behavior, and there is no general procedure to develop them. Here, we propose an approach that combines nonlinear controllers based on the deduced model and on the Lyapunov theory to control the velocities of the vehicle with linear controllers that control the vehicle's position. We derive control laws to perform several maneuvers, both in the vertical and the horizontal planes, in a decoupled way, which is made possible through the configuration of thrusters. Finally, we present realistic simulations and experimental results that validate the proposed approach in the definition of the control laws.