Adaptive fixed-time control of autonomous VTOL UAVs for ship landing operations

This paper addresses the fixed-time control problem of autonomous ship landing operations of vertical take-off and landing (VTOL) unmanned aerial vehicles (UAVs) subject to external disturbances. A continuous reference altitude is planned for the UAV by introducing a high order polynomial function and a continuous differentiable switching function. To ensure a safe and precise board landing operation under bad sea condition, a landing constraint condition is designed in terms of rotational motion of the ship. By combining the planar motion of the ship with the reference altitude, the landing mission is converted into the control development for the UAV tracking. By introducing the hierarchical design, an adaptive fixed-time control algorithm is proposed for the UAV such that the trajectory and command attitude tracking are achieved, respectively. It is proved via Lyapunov stability theory that the proposed control algorithm guarantees the fixed-time trajectory tracking of the UAV subject to unknown external disturbances and inertia parameters. Simulation examples verify the proposed strategy.