Robust Fault-Tolerant Control of Launch Vehicle Via GPI Observer and Integral Sliding Mode Control

A robust fault-tolerant attitude control scheme is proposed for a launch vehicle (LV) in the presence of unknown external disturbances, mismodeling dynamics, actuator faults, and actuator's constraints. The input-output representation is employed to describe the rotational dynamics of LV rendering three independently decoupled second order single-input-single-output (SISO) systems. In the differential algebraic framework, general proportional integral (GPI) observers are used for the estimations of the states and of the generalized disturbances, which include internal perturbations, external disturbances, and unknown actuator failures. In order to avoid the defects of the conventional sliding surface, a new nonlinear integral sliding manifold is introduced for the robust fault-tolerant sliding mode controller design. The stability of the GPI observer and that of the closed-loop system are guaranteed by Lyapunov's indirect and direct methods, respectively. The convincing numerical simulation results demonstrate the proposed control scheme is with high attitude tracking performance in the presence of various disturbances, actuator faults, and actuator constraints.