Robust flight control for hypersonic flight vehicle using nonlinear disturbance observer

Dynamic surface control scheme combined with a nonlinear disturbance observer technique is investigated for application to a class of generic hypersonic fight vehicles (HFVs) with parametric uncertainties and external disturbance. The proposed scheme possesses the following significant advantages: 1) A nonlinear disturbance observer-based approach enhances the system´s disturbance attenuation ability and robustness of performance against uncertain aerodynamic coefficients. 2) The dynamic surface control is designed to avoid issues regarding “explosion of complexity” that exist in the backstepping scheme by introducing a first order filter. Disturbance estimations are introduced into the virtual control laws at each step to compensate for unknown external disturbances or parametric uncertainties. Stability analysis for the closed-loop system is then established by the Lyapunov function method. Analysis results demonstrate that all signals of the closed-loop system were uniformly, ultimately bounded.