Rigid Spacecraft Attitude Regulation with Delayed Feedback and Actuator Faults

The work presented in this paper discusses time delay compensation of a rigid spacecraft with faulty actuators. The proposed method consists of a nominal controller and an extended state observer. Based on the backstepping method, the nominal control is designed to stabilize the spacecraft in the presence of delayed inputs. Then, the discrepancy between the nominal plant and real system which is influenced by faulty actuators, model uncertainties, and external disturbances is estimated by the extended state observer and actively compensated. The proposed controller does not require exact knowledge of delay, actuator faults and disturbances. By adjusting controller parameters, using the Lyapunov-Krasovski method and properties of modified Rodrigues parameters, it is proved that the investigated control scheme can stabilize the system with respect to a small neighborhood of the origin. Numerical simulation results demonstrate that the acceptable performance of the controlled system is guaranteed in the presence of retreated inputs, the considered faults are tolerated and disturbances are rejected.