Nonlinear Extended State Observer-Based Closed-Loop Control for Underactuated USV: High-Order Fully Actuated System Approach

This paper proposes a nonlinear extended state observer-based closed-loop control strategy for underactuated unmanned surface vessel (USV) using the high-order fully actuated (HOFA) system framework. To address the challenges of nonlinearity, strong coupling, and external disturbances inherent in underactuated USV, a diffeomorphism transformation is introduced to convert the original underactuated dynamics into a HOFA model, which simplifies controller design by eliminating the need for intricate Lyapunov function construction. A third-order nonlinear extended state observer is integrated to estimate and actively compensate for unmodeled dynamics and external disturbances, which enhances the disturbance-rejection capability of underactuated USV system. The effectiveness of this method is verified through numerical simulations.