Fixed-Time Attitude Tracking Control for Rigid Spacecraft With Actuator Misalignments and Faults

This paper investigates an attitude tracking maneuver problem for a rigid spacecraft with external disturbances, uncertain inertia parameters, actuator misalignments, and faults. First, all the uncertainty terms are split from the desired commanded control torque, and then, the nonsingular terminal sliding mode is implemented to design a fixed-time attitude tracking controller. Subsequently, an adaptive law is drawn into the attitude tracking controller to form a new control scheme, which eliminates the requirement of the upper bounds of all the uncertain terms. Besides, in the light of the concept of fixed-time stabilization, practical fixed-time convergence is achieved for attitude tracking errors. Finally, the numerical simulations are demonstrated to highlight the performance of the proposed controllers.