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This paper proposes a fault-tolerant control allocation (FTCA) scheme for a flexible satellite. A novel control strategy is implemented, which fulfills the satellite mission and also decreases vibrations, saturation time of the actuators, and required energy. Avoiding spillover instability, an infinite-dimensional model of the flexible satellite is considered, which is one of the important benefits of the proposed control scheme over the previously presented FTCA methods. External disturbances, the uncertainty of moment of inertia, actuator fault and failure, imprecision in fault estimation, and control constraints are considered. The designed control system is comprised of two modules: the virtual control module that designs the virtual control law to stabilize the satellite and control vibrations without any in-domain actuators on panels, and a distribution control module that distributes the virtual control law among actuators based on their fault information and distance of bound of the control limit. The proposed virtual control law consists of an observer-based PD-like nominal control and adaptive control parts, and the internal reaction torque is estimated using a nonlinear observer. The closed-loop uniformly ultimately bounded (UUB) stability is achieved using Lyapunov criteria. A numerical example illustrates the effectiveness of the proposed approach regarding attitude stabilization and vibration control objectives. [ABSTRACT FROM AUTHOR]

Fault-tolerant control allocation (FTCA) strategy is proposed for attitude stabilization of a flexible satellite with actuator redundancy. The control scheme is based on the infinite-dimensional model of a flexible satellite with no discretization, so the spillover instability is eliminated. This is one of the important benefits of the proposed control scheme over the previous FTCA schemes that have been used for the flexible satellite. The proposed scheme contains two modules. The first module provides a virtual control law to meet stabilization and vibration control objectives in the presence of uncertainties and external disturbances. There is no need to implement in-domain actuators on panels to stabilize their vibration. In this module, the virtual control is designed using adaptive integral sliding mode approach where the sliding surface includes angular velocities, internal reaction torques, and nominal control for healthy system. The second module, based on fault/failure information and using a control allocation scheme, provides redistribution of the virtual control law among the available actuators. Due to simultaneous actuator faults and control constraints, there is an error between the actual virtual control and the designed control that affects the overall system stability. To eliminate this error, gain of the virtual control signal is adjusted by an adaptive updating law. The closed-loop system stability is guaranteed for small changes in a neighborhood of the sliding surface with simultaneous vibration damping. A numerical example illustrates the effectiveness of the proposed control strategy. [ABSTRACT FROM AUTHOR]

Fault-tolerant control (FTC) strategy based on adaptive integral sliding mode (AISM) is proposed to stabilize a flexible satellite, subject to inertia uncertainties, external disturbances, and actuator faults. Using Hamilton's principle, the satellite dynamics is presented as a coupled Ordinary Differential Equation (ODE) and Partial Differential Equation (PDE). The control scheme is based on the infinite-dimensional model of the flexible satellite with no discretization, so the spillover instability phenomenon is eliminated. This is the most important advantage of the proposed control scheme over the previous FTC schemes that have been used for the flexible satellite. Stabilization and vibration suppression are performed using control torque that is applied to the rigid center, and there is no need to implement in-domain actuators on panels to stabilize their vibration. First, a novel nominal controller based on the infinite-dimensional model of the satellite is designed for a healthy system. Then, an integral sliding surface, including angular velocities, internal reaction torques, and nominal control, is proposed. Finally, an AISM controller with an adaptive estimator is designed to accommodate actuator faults and other uncertainties. System stability is guaranteed for small changes in a neighborhood around the sliding surface with simultaneous vibration damping. Numerical simulations illustrate the effectiveness of the proposed control strategy. [ABSTRACT FROM AUTHOR]