Fuzzy Disturbance Observer Based Fixed-time Sliding Mode Control for Hypersonic Morphing Vehicles with Uncertainties

This work focuses on the attitude control problem for hypersonic morphing vehicles(HMVs) with uncertainties. A span-morphing HMV model is firstly established with lumped disturbances. Based on fixed-time technique, a disturbance observer with fuzzy logic system(FLS) is proposed to enhance the robustness by estimating the unmodelled dynamics and external disturbances in fixed settling time. The multivariable fixed-time sliding mode manifold is applied to the transformed control system, which guarantees a direct control input design from attitude command and decent tracking performance. Then, the control system degenerates into an autonomous system, and the closed-loop fixed-time stability is ensured via Lyapunov synthesis and homogeneity theory. Finally, simulation results are presented to demonstrate the effectiveness of the proposed control scheme.