Anti-disturbance for Vectored-Thrust VTOL via Sliding Mode Control with Enhanced Observer

Vectored-thrust vertical takeoff and landing (VTOL) unmanned aerial vehicles (UAVs) have advanced rapidly due to their broad application prospects. However, during takeoff and landing, their attitude and position control are easily affected by wind disturbances, especially in miniaturized designs. While the extended state observer (ESO) is commonly used in model-free approaches for disturbance estimation, it faces limitations in model-based control due to its non-derivative structure and restricted information use. This paper proposes a disturbance-rejection controller that replaces the ESO with an enhanced state compensation function observer (SCFO), and combines it with an equivalent sliding mode controller. Comparative simulations with classical observers demonstrate the SCFO’s improved estimation accuracy and convergence. In addition, flight experiments on a vectored-thrust VTOL show that, compared with a conventional PID controller, the proposed method significantly reduces tracking error and enhances robustness in windy conditions, enabling stable hovering under external disturbances.