Adaptive disturbance observer-based finite-time continuous fault-tolerant control for reentry RLV

The control effectors of reusable launch vehicle (RLV) can produce significant perturbations and faults in reentry phase. Such a challenge imposes tight requirements to enhance the robustness of vehicle autopilot. Focusing on this problem, a novel finite-time fault-tolerant control strategy is proposed for reentry RLV in this paper. The key of this strategy is to design an adaptive-gain multivariable finite-time disturbance observer (FDO) to estimate the synthetical perturbation with unknown bounds, which is composed of model uncertainty, external disturbance, and actuator fault considered as the partial loss of actuator effectiveness in this work. Then, combined with the finite-time high-order observer and differentiator, a continuous homogeneous second-order sliding mode controller based on the terminal sliding mode and super-twisting algorithm is designed to achieve a fast and accurate RLV attitude tracking with chattering attenuation. The main features of the integrated control strategy are that the adaptation algorithm of FDO can achieve non-overestimating values of the observer gains and the second-order super-twisting sliding mode approach can obtain a more elegant solution in finite time. Finally, simulation results of classical RLV (X-33) are provided to verify the effectiveness and robustness of the proposed fault-tolerant controller in tracking the guidance commands. Copyright (c) 2017 John Wiley & Sons, Ltd.