A fixed-time fuzzy control framework for spacecraft based on disturbance estimator and guaranteed performance

This paper studies spacecraft attitude tracking issue under actuator faults and external disturbances. A dynamic estimator reconstructs the lumped disturbance without differentiating the measured attitude-rate signal. The estimation error decays exponentially for constant disturbances and has an explicit ultimate bound when the disturbance derivative is bounded. A scalar fuzzy adaptive term compensates for the remaining uncertainty within a command-filtered backstepping controller. A prescribed-performance transformation constrains the attitude error to a time-varying envelope. Under the stated operating-domain and auxiliary-dynamics conditions, the Lyapunov analysis gives a residual-set bound and a reaching-time estimate independent of the initial tracking error. The envelope is preserved along admissible trajectories with bounded transformed errors. Simulation results confirm the superiority of the proposed scheme in disturbance estimation and tracking accuracy under the considered fault conditions.