POSITION CONTROL AND ATTITUDE STABILIZATION OF A DUCTED FAN VTOL UAV IN CROSSWIND

This paper describes a control strategy to stabilize the position of a Vertical Takeoff and Landing (VTOL) Unmanned Aerial Vehicle (UAV) in crosswind. The proposed approach takes advantage of the cascade structure of the system to design a hierarchical controller involving a High Level Controller devoted to position control and a Low Level Controller devoted to attitude stabilization. Both controllers are designed by means of backstepping techniques that allow the stabilization of the vehicle's position while on-line estimation of the unknown aerodynamic forces. Simulations as well as experimental results are presented to illustrate the concept.