Multivariable Disturbance Observer-Based Fuzzy Fast Terminal Sliding Mode Attitude Control for a Hypersonic Vehicle

This paper develops a comprehensive methodology to address the attitude control problem of hypersonic vehicles in the presence of matched model uncertainties and external disturbances. Initially, a nonlinear dynamic model was established dedicated to attitude control. Afterward, a multivariable disturbance observer was constructed to estimate the lumped disturbance for compensation. Moreover, the dynamic inversion technique was adopted to cancel the nonlinear dynamics for decreasing complexity of controller design. To proceed, a novel fuzzy fast terminal sliding mode control strategy was designed to achieve a significant performance of attitude command tracking with the integrated consideration of robustness, chattering alleviation, and actuator saturation rejection. The finite-time stability of the closed-loop system was proven by means of the finite-time bounded function method and the Lyapunov theory. Simulation results demonstrated that the proposed synthetic scheme showed preferable performance and strong robustness in view of attitude command tracking.