Characteristic model-based H2/H∞ robust adaptive control during the re-entry of hypersonic cruise vehicles

This paper aims at introducing H-2 and H-infinity robustness into the well-known characteristic modelbased golden-section adaptive control law, and applying the robust adaptive control scheme to the attitude control of hypersonic cruise vehicles that are subject to external disturbances and aerodynamic coefficients uncertainties. When maneuvering at ultra high speeds, the attitude system of the hypersonic cruise vehicle is extremely sensitive to external disturbances and aerodynamic coefficients variations, and therefore the adaptiveness and the robustness of the attitude system are crucial during the controller design. To enhance the robustness of the existing golden-section adaptive control law, a golden-section robust adaptive control law is proposed. Compared to the existing control law where the design of the parameter lambda depends on experience and is carried out offline, linear matrix inequality-based synthesis of lambda is proposed such that the closed-loop system is stable with guaranteed H-2 and H-infinity performance. It is suitable for online computing and provides a time-varying lambda(k) that is adjusted towards the optimal H2 and H8 performance. When being applied to the attitude control of hypersonic vehicles during re-entry, the adaptive nature of the proposed control law provides the attitude system the capability to accommodate large flight conditions, and its H-2 and H-infinity robustness brought by lambda(k) guarantees satisfying tracking performance in the presence of disturbances including both external disturbance and absolute aerodynamic coefficients errors.