Finite Time Fault Tolerant Attitude Control-Based Observer for a Rigid Satellite Subject to Thruster Faults

A rigid satellite fault diagnosis strategy, subject to faults of external disturbances and thruster faults, is developed. In this design, an equivalent idea is introduced to design a sliding mode observer that can detect and identify the failures indicated previously. Considering the measurability of parameters of the satellite, such as angular velocity and attitude, a sliding mode observer is implemented. Next, the amplitudes of the faults and disturbances can be detected, identified, and estimated via the sliding mode observer; these tasks are accomplished with zero estimation error within a finite period. A sliding mode-based attitude controller is developed using an exponential reaching law that relies on the system states and the corresponding formation of the estimated parameters. The controller not only guarantees the attitude system to be stable but also governs the attitude and angular velocity to converge to zero within a finite period. The good reliability of the proposed controller can be proved via multiple simulation tests.