An Anti-Disturbance Attitude Control Method for Fixed-Wing Unmanned Aerial Vehicles Based on an Integral Sliding Mode Under Complex Disturbances During Sea Flight

The increasing complexity of aerial acrobatics missions necessitates ever-higher levels of attitude control precision in fixed-wing unmanned aerial vehicles (UAVs). Traditional control methods, such as feedback linearization and small disturbance derivation linear models, falter in maintaining attitude tracking accuracy, due to the presence of unanticipated disturbances—most notably, wave disturbances during low-altitude maritime flights—and model uncertainties introduced by factors like large-angle maneuvers, intricate aerodynamic characteristics, and fuel consumption. Consequently, these limitations impede the successful execution of intricate maneuvers, such as looping, the split-S, the Immelmann turn, and the Pougatcheff cobra maneuver. In response to these challenges, we propose an integral sliding mode control based on disturbance observer (ISMC-DO) system to achieve robust attitude angle tracking amidst model uncertainties and mitigate the effects of wave disturbances. Additionally, quaternion representations are adopted as a supplement to Euler angles, thereby resolving the singularity issues inherent in the latter. By using the Lyapunov function, the ISMC-DO-based control system is shown to be asymptotically stable. Simulation results further validate that ISMC-DO can achieve high-precision attitude tracking control of the UAV under wave disturbance.