Work

Adaptive Nonlinear Terminal Sliding Mode Control for underactuated USV path following under ocean disturbances

Year: 2026

Type: article

Abstract: Unmanned Surface Vehicles (USVs) are increasingly deployed in ocean engineering applications such as hydrographic surveying, environmental monitoring, and maritime security. Achieving accurate path following in realistic ocean environments remains challenging due to nonlinear vessel dynamics, environmental disturbances, and underactuation arising from the absence of direct sway control. This paper proposes an Adaptive Nonlinear Terminal Sliding Mode Controller (ANTSMC) for a three-degree-of-freedom (3-DOF) underactuated USV subject to wind, wave, and current disturbances. The controller integrates a regularised nonlinear terminal sliding surface with a power-rate reaching law and a leakage-regulated adaptive switching gain that adjusts robustness online without a disturbance observer. A benchmark evaluation was conducted across six controllers (LQR, SMC, ASMC, ADRC, FNTSMC, and ANTSMC), four path geometries, and three WMO sea states while accounting for realistic sensor noise and parametric uncertainty. The results show that ANTSMC achieves cross-track accuracy comparable to SMC under calm sea conditions, while demonstrating stronger robustness as environmental disturbances increase. In particular, ANTSMC produces the lowest RMS cross-track error under SS 2 (smooth) and SS 3 (slight) conditions, where the imposed disturbance intensity is higher. Independent validation using the MBZIRC physics-based maritime simulator provides additional evidence of bounded, accurate path-following performance across different path geometries. Moreover, a Monte Carlo study evaluates robustness under expanded parametric and disturbance uncertainties. The results indicate that the proposed observer-free framework provides consistent path-following performance over the tested marine operating conditions.

Source: Applied Ocean Research

DOI: 10.1016/j.apor.2026.105231

Authors: Muhayy Ud Din, Waseem Akram, Irfan Hussain

Institutions: Khalifa University of Science and Technology, University of Zagreb, Faculty of Electrical Engineering and Computing in Zagreb

Language: English

Topic: Adaptive Control of Nonlinear Systems

Subfield: Control and Systems Engineering

Field: Engineering

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $2,950

Funder: Khalifa University of Science, Technology and Research