Finite-time disturbance-rejection control of a dual-thruster USV via NDOB

To address the challenges of model uncertainty and external disturbances in unmanned surface vehicle (USV) trajectory tracking control, this paper proposes a finite-time dynamic surface control (FTDSC) method based on a nonlinear disturbance observer (NDOB). By integrating the NDOB with a finite-time control law, the proposed approach achieves real-time estimation and feedforward compensation of lumped disturbances, thereby ensuring practical finite-time stability while significantly enhancing system robustness. To improve the consistency between the nominal simulation model and the measured USV dynamic responses while preserving physical interpretability, a semi-empirical system identification strategy is adopted to obtain the Fossen model parameters. In addition, a constrained quadratic programming-based thrust allocation method is employed to generate feasible thrust commands for the twin-propeller system. SimuNPS simulation test results demonstrate that the proposed control method outperforms conventional PID, linear disturbance observer PID (DOB-PID), sliding mode control (SMC), and standard FTDSC in terms of tracking accuracy, disturbance rejection capability, and practical applicability, verifying its effectiveness and superiority.