An EKF based method for path following in turbulent air

Abstract

An innovative use of the Extended Kalman Filter (EKF) is proposed to perform both accurate path following and adequate disturbance rejection in turbulent air. The tuned up procedure employs simultaneously two different EKF: the first one estimates gust disturbances, the second one estimates modified aircraft parameters. The first filter, by using measurements gathered in turbulent air, estimates aircraft states and wind components. The second, by using the estimated disturbances, obtains command laws able to reject disturbances. Therefore, the estimated wind components are inserted into the predictor of the second EKF, which contains the motion equations in turbulent air. Since aerodynamic coefficients are modified by adding entirely new derivatives or synthetic increments to basic ones. So a set of unknown stability and control parameters (containing displacements of the controls) is introduced into the predictor. Therefore the aircraft’s state is augmented by the above aforementioned unknown values of aircraft parameters. The filter estimates the latters by using a set of measurements formed by the desired flight path variables. Due to the postulated unknown stability and control derivatives containing control displacements, the command laws are obtained. The obtained control laws are adaptive since they are related to either the characteristics of the disturbance or the desired flight path.