Robust trajectory linearization control of a flexible hypersonic vehicle in the presence of uncertainties

This paper addresses the design of a robust trajectory linearization control (TLC) scheme for a flexible air-breathing hypersonic vehicle model with multiple uncertainties. Because of the model complexity, the flexibility effects and open-loop behaviors are analyzed, offering insights on the vehicle features and guidelines for control design. Based on the analysis, a basic TLC frame, including an adaptive time-varying bandwidth algorithm, is firstly constructed. As for the inevitable uncertainties in hypersonic flight, a uniform nonlinear uncertainty model is explored which lumps all external disturbances and typical internal uncertainties such as propulsive perturbations and variations in control effectiveness together. Then extended state observer (ESO) technique is integrated into the basic TLC frame to estimate and compensate these uncertainties, forming a robust TLC scheme. Two flight cases are conducted, through which the robust scheme exhibits great tracking performance and uncertainty rejection ability.