Tunable Predefined-Time Attitude Tracking Control for Rigid Spacecraft

The problem of the predefined-time attitude tracking control for rigid spacecraft subject to internal parameter uncertainty and external disturbance is addressed in this paper. A new criterion is first derived for the tunable predefined-time stability. Then, a new tunable predefined-time controller based on a predefined-time extended state observer is designed for the attitude tracking of rigid spacecraft. Different from the existing predefined-time control methods, the proposed tunable predefined-time controller can guarantee that the settling time of the system is strictly bounded by a given constant, while the actual settling time can be sped up or slowed down by tuning an extra parameter. The stability of the resulting closed-loop system under the designed controller is proven by the Lyapunov stability theory. Some simulation results are provided to verify the advantages of the proposed controller.