Immersion and invariance based nonlinear adaptive longitudinal control for autonomous aircraft

This paper presents a novel nonlinear adaptive control scheme for the angle of attack of autonomous aircraft with some unknown aerodynamic parameters based on Immersion and Invariance approach. The design is based on a modular adaptive backstepping scheme with a recently developed nonlinear estimator that is relatively easy to tune. The nonlinear estimator is based on the notion of the invariant manifold which allows for the prescribed dynamics to be assigned to the estimation error. The estimator is combined with the adaptive backstepping control law that renders the closed-loop system stable with respect to the parameter estimation error. The main feature of the proposed flight control method is that it is valid in the entire flight envelope and does not require accurate knowledge of the aerodynamic coefficient. The numerical simulation shows that the proposed control system can accomplish the trajectory control of the angle of attack.