Robust Aeroelastic Response Estimation for Flexible Aircraft

Elastic deformations of flexible aircraft significantly affect its stability, control, and performance. This paper proposes an observer-based approach to estimate the elastic motion of flexible aircraft under uncertainty. Based on an accurate aeroelastic model and primary sensors providing reliable rigid-body measurements, two full-order observers are synthesized to estimate both rigid-body and elastic modes. The first is a classical Luenberger observer with pole placement method for the observer gain selection. The second is a full-order discontinuous sliding mode observer that is robust to bounded exogenous disturbance, such as gust effects. The observer-based approach is demonstrated on a generic flexible hypersonic aircraft model to robustly estimate longitudinal elastic deformation in the presence of moderate gusts.