Fault-Tolerant Attitude Control of Small Spacecraft Using Robust Artificial Time-Delay Approach

This article presents a robust artificial time-delay-based attitude regulation control of a small spacecraft under the influence of parametric uncertainties, surrounding disturbances, and time-varying actuator faults. In the artificial time-delay (ATD) approach, the input-output information of the previous time instant is utilized to estimate the uncertain dynamical parts. The proposed attitude controller is designed by integrating the time-delay approach with a feedback control technique. Under the proposed composite control scheme, the system states are proved to be uniformly ultimately bounded (UUB) stable using the Lyapunov analysis. Moreover, the problem of unwinding in the quaternion representation, due to which the spacecraft consumes more time and energy, is also resolved under the proposed scheme. The performance of the proposed control methodology has been validated using numerical simulations. Furthermore, two different control schemes are also compared to illustrate the efficacy of the proposed strategy.