Artificial Time Delay based Adaptive Robust Fault Tolerant Control for RLV During Re-entry Phase

This paper considers attitude tracking problem of a reusable launch vehicle (RLV) in its re-entry phase. The complex environmental conditions and highly nonlinear coupled dynamics impose a challenging task to regulate the spacecraft to follow a desired trajectory. In this paper, an artificial time-delay based control (TDC) scheme is implemented to incorporate robustness against system uncertainties, external disturbances and actuator faults. The time-delay approach uses input and output measurements from the past instant to estimate uncertainties effecting the system. Lyapunov stability is conducted to show that with the proposed control scheme uniformly ultimately bounded (UUB) convergence of system states under bounded estimation error is ensured. To further improve the performance, a switching law is augmented with the TDC. Additionally, a dual-rate adaption law for switching gain has also been exploited to prevent over and under estimation. The effectiveness of the proposed control scheme is verified through simulation results which shows robust tracking of the desired trajectory.