Three-dimensional path-following control of nonlinear autonomous underwater vehicles with actuator saturation

This paper addresses the challenging problem of three-dimensional (3D) path-following control for a class of nonlinear autonomous underwater vehicles (AUVs) equipped with four independently movable control surfaces, with a specific focus on actuator saturation. The core objective is to achieve exponential stabilization of the regulation-error dynamics, encompassing critical variables such as the desired surge speed, horizontal and vertical path-tangential angles, and cross-track errors and their derivatives. Our approach leverages advanced nonlinear feedback control techniques, including feedback linearization and linear parameter varying (LPV) or fuzzy model-based control, to systematically decompose the control problem. This decomposition leads to the attainment of regional exponential stability for distinct control components, namely speed control, horizontal path-following, vertical path-following, and roll control according to the Lyapunov stability criterion within the linear matrix inequality (LMI) framework. Rigorous stability analysis of the overall control system demonstrates its ability to ensure the boundedness of state trajectories and, notably, practical stability. Two illustrative examples are provided to validate our proposed methodology.