Wind disturbance compensated path-following control for fixed-wing UAVs in arbitrarily strong winds

Wind is the primary challenge for low-speed fixed-wing unmanned aerial vehicles to follow a predefined flight path. To cope with various wind conditions, this paper proposes a wind disturbance compensated path following control strategy where the wind disturbance estimate is incorporated with the nominal guiding vector field to provide the desired airspeed direction for the inner-loop. Since the control input vector for the outer-loop kinematic subsystem needs to satisfy a magnitude constraint, a scaling mechanism is introduced to tune the proportions of the compensation and nominal components. Moreover, an optimization problem is formulated to pursue a maximum wind compensation in strong winds, which can be solved analytically to yield two scaling factors. A cascaded inner-loop tracking controller is also designed to fulfill the outer-loop wind disturbance compensated guiding vector field. High-fidelity simulation results under sensor noises and realistic winds demonstrate that the proposed path following algorithm is less sensitive to sensor noises, achieves promising accuracy in normal winds, and mitigates the deviation from a desired path in wild winds.