AUTOMATIC TAKE-OFF OR LANDING PATH FOLLOWING IN TURBULENT AIR FOR UAS - AN EKF BASED PROCEDURE

Abstract

By using the Extended Kalman Filter (EKF) an accurate take-off or landing flight path following in turbulent air is performed. The tuned up procedure employs simultaneously two different EKF: the first one estimates gust disturbances, the second one affords to determine the necessary controls displacements for rejecting those ones. In particular, the first filter, by using instrumental measurements gathered in turbulent air, estimates wind components. The second one obtains command laws able to follow the desired flight path. To perform this task aerodynamic coefficients have been modified by adding entirely new derivatives or synthetic increments to basic ones whose might the kind of change required to reject disturbances. Such a procedure leads to a set of unknown stability and control parameters containing the required displacements of the controls. The modified aircraft parameters are determined by augmenting the aircraft’s state. The filter estimates the new set of aircraft stability derivatives by using measurements made by the desired take-off or landing flight path parameters. Once the unknown stability and control derivatives have been determined, the obtained control displacements are used to perform an accurate path following in turbulent air. Obviously, the obtained control laws are adaptive since they depend by either the characteristics of the disturbance or the desired flight path. The proposed procedure requires low computational power, therefore it is particularly suited for UAS, besides being simple to implement on board it may be successfully employed on low cost platforms.