Estimation of wind gusts using an unknown input observer

This paper describes the design of an estimator for wind gusts acting on an airplane during flight. The linearised longitudinal model of the airplane for steady state rectilinear flight is presented. It is shown, how wind gusts, which are considered to be unknown inputs to the airplane, can be estimated in general, if the unknown inputs appear in the output equation. The unknown inputs are removed from the system by use of a transformation. It is discussed, which measurements are necessary for the transformed system to be observable. The proposed estimator is a combination of an output transformation and an unknown input observer. The performance of the estimator is demonstrated with simulations. The robustness of the proposed estimator with respect to model uncertainties has also been tested with the help of simulations.