Adaptive fault-tolerant attitude control for microsatellite based on disturbance observer

In this paper, an adaptive fault tolerant control (FTC) method based on disturbance observer is proposed for microsatellite attitude control system (ACS) with actuator faults and multiple disturbances simultaneously. Disturbance observer and fault diagnosis observer are designed to estimate the modeled disturbances and faults of flywheels, respectively. An adaptive term is applied to compensate norm-bounded disturbance. Furthermore, a composite fault tolerant controller is constructed to reject modeled disturbance, to accommodate actuator faults, and to compensate norm bounded disturbance. Compared with the robust FTC, this method removes the assumption that the norm bounded disturbance is bounded by a known constant. Finally, simulations for a microsatellite ACS are given to demonstrate the effectiveness of the proposed method.