Optimal depth controller for an Autonomous Underwater Vehicle under constrains and uncertainties

In this paper an Optimal Controller for the depth plane motion of an Autonomous Underwater Vehicle (AUV) is presented. The controller is designed based on a linearized model that describes the rigid body dynamics of the AUV while including all the external forces and moments that are produced from the hydrostatics, the hydrodynamic lift and drag, the added mass, the control inputs of the vehicle propeller and the fins. These factors are all defined in terms of vehicles coefficients in the AUV´s model. The proposed control scheme is based on the theory of Constrained Finite Time Optimal Control scheme and it is able to take under consideration factors that degrade the performance of the controlled vehicle such as: a) the physical and mechanical constrains of the system, b) the disturbances that are introduced from the sensing elements, and c) the additive uncertainty due to modeling errors. The proposed controller is applied in simulations and multiple results are presented that prove the efficacy of the proposed scheme.