Robust fuzzy tracking control for flexible air-breathing hypersonic vehicles with measurement noises

Measurement noise is an obstacle to the performance improvement of a flexible air-breathing hypersonic vehicle. This paper explores a robust fuzzy tracking control scheme for the longitudinal dynamics of the hypersonic vehicle, which is constructed by utilizing type-2 fuzzy adaptive technique and dynamic surface control (DSC) approach. The control scheme is comprised of two parts: the state estimators and tracking controllers of velocity and altitude. The state estimators are designed by using the type-2 fuzzy logic system-based approximators, which guarantees the estimation of real states from measurement signals with noises. Furthermore, on the basis of the designed state estimators, the velocity and altitude tracking controllers are constructed by using the adaptive fuzzy DSC approach. On one hand, DSC approach can filter the virtual control law and avoid the amplification of the measurement noise. On the other hand, since the antecedent of the type-2 fuzzy logic system is based on the type-2 fuzzy sets and the consequent parameters are adjusted by an integral calculation in the adaptive law, the type-2 fuzzy adaptive technique in the adaptive fuzzy DSC tracking controller has the ability to further reduce the impact of the measurement noises. A Lyapunov-based stability analysis shows the tracking ability of the proposed control scheme. Nominal and comparison simulation considering the measurement noises are carried out for demonstrating the effectiveness of the proposed method.