Disturbance Observer–Based Backstepping Control for Hypersonic Vehicles with Input Constraints

A super-twisting disturbance observer–based adaptive fixed-time antisaturation backstepping control algorithm is designed for hypersonic vehicles with input constraints. First, super-twisting disturbance observers are developed to estimate the lumped disturbances comprising model uncertainties, aerodynamic uncertainties, and external disturbances, which will enhance the robustness of the backstepping controller. To address the problem of explosion of complexity in the backstepping approach, hyperbolic sine tracking differentiators are used and which can achieve a higher tracking accuracy than that of the command filtered backstepping control algorithm. Furthermore, an adaptive fixed-time antisaturation compensator (AFAC) is used to suppress the influence of actuator saturation. AFAC can shorten the saturation duration, and the auxiliary variable of AFAC rapidly converges to zero after the saturation disappears. In this case, the controller degenerates to the former backstepping controller. Finally, the effectiveness of the proposed controller is verified by numerical simulation results.