Abstract:

In order to improve the autonomous operation ability of a bias momentum microsatellite, a sliding mode fault-tolerant control method based on an observer of uncertain terms is proposed. Using the disturbance observation method of the Euler-Lagrange system, an observer of uncertain terms is designed to estimate the actuator faults, such as the reduction of the momentum wheel output torque and the resistance drift of the magnetic torquer’s coil as well as the environmental disturbance torques of the satellite, and the theoretical deduction shows that the observation error of the observer is uniformly ultimately bounded (UUB). The estimated values of the observer are used for the feedback compensation of the sliding mode fault-tolerant controller. The stability analysis shows that the proposed method can quickly converge the satellite attitude to the sliding surface. It is noted that the control method proposed in this paper does not need to make the small-angle assumption and the fault-tolerant control process is not dependent on the working state information of the actuators. The attitude control performance is evaluated by the numerical simulations.

Key words:  Bias momentum, Fault-tolerant control, Terminal sliding mode, Observation of uncertain terms