Adaptive fault tolerant attitude control based on a disturbance observer for satellites with multiple disturbances

The attitude control problem is much more complicated due to the existence of faults and multiple disturbances simultaneously in satellites. In this paper, an adaptive fault tolerant attitude control method is presented for satellites with both time-varying actuator faults and multiple disturbances. Differing from previous results, the first part of the multiple disturbance is the uncertain modelled disturbance and the second part represents an uncertain variable bounded by a given function. A composite observer is designed to estimate the uncertain modelled disturbance and the time-varying fault simultaneously. Then, a new fault tolerant control strategy consisting of disturbance observer based control, fault accommodation and an adaptive controller is constructed to reconfigure the concerned systems and so as to achieve the anti-disturbance performance. In the proposed method, the modelled disturbance can be rejected by its estimation and the uncertain bounded disturbance can be compensated by the adaptive compensation term. The simulation results are given to show the efficiency of the proposed approach.