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

Abstract

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 rough sea wave, a feasible landing condition in terms of rotational motion of the ship is provided. By transforming the ship landing problem into the trajectory tracking of the UAV, an adaptive fixed-time control strategy is proposed by introducing the hierarchical framework such that the position tracking to the planar trajectory of the ship and the reference altitude, and the attitude tracking to the command attitude are achieved. It is proved via hierarchical system stability theory that the proposed control strategy guarantees the achievement of trajectory tracking of the the UAV subject to unknown inertia parameters and external disturbances in a fixed time. Simulation example verifies the proposed strategy.