Immersion and Invariance-Based Nonlinear Control Synthesis for Depth Position of an AUV: Tracking and Regulation

This paper addresses the tracking control problem associated with the diving motion system of a torpedo-like shape autonomous underwater vehicle (AUV). A decoupled and reduced-order three degrees-of-freedom (3-DOF) nonlinear model is employed to represent the dynamics of the diving motion system for depth position control. The control objective is to track the demanded depth position in the presence of uncertainties and disturbances. A control law based on the immersion and invariance (I &I) technique is synthesized to achieve the control objectives. The proposed control law effectively tracks a stable, lower-order target dynamic system immersed within a three-dimensional manifold. Additionally, the regulation problem is treated as a specialized case of tracking, with a known depth serving as the reference input to be regulated. The performance of the proposed control law is assessed through simulation studies that consider various scenarios. The simulation study evaluates the robustness of the proposed control law resilience against modelling uncertainties and underwater disturbances. The simulations utilize the MAYA AUV, incorporating experimentally validated diving motion parameters. The proposed control law’s quantitative analysis and computational performance show better performance against the benchmark controller.