Anti-Unwinding Active Fault-Tolerant Attitude Tracking Control for Uncertain Spacecraft via Fully Actuated System Approach

This article proposes an active fault-tolerant control (AFTC) scheme for attitude tracking of uncertain spacecraft with actuator faults and unavailable angular velocity. First, a second-order fully actuated system (FAS) model is derived from the dynamics of the spacecraft. The unwinding phenomenon is solved by controlling the scalar quaternion. Then, the state observer and the FAS-based controller are designed, and the assumption that all the system states and their derivatives are requested to be known is relaxed, which is a typical assumption in the existing FAS approach. The proposed method facilitates the detection and analysis of the fault information for a spacecraft, based on which an AFTC scheme is designed to address uncertain spacecraft attitude tracking under uncertain time-varying inertia parameters, faults, and disturbances. Moreover, angular velocity measurements are not needed. The uniformly bounded stability of the proposed control scheme is theoretically proved. Finally, the numerical simulation results are provided to illustrate the performance of the proposed control scheme.