A distributed predefined-time attitude coordination control scheme for multiple rigid spacecraft

In this paper, the distributed predefined-time attitude coordination control problem is investigated for multiple rigid spacecraft systems when only a subset of spacecraft has access to the reference attitude and angular velocity. Two sliding mode estimators are proposed to estimate the reference attitude and angular velocity, respectively. It is proved that the states of the two proposed estimators can converge to zero in a predefined time. Then, a predefined-time control scheme is designed for the multiple rigid spacecraft systems subject to inertial uncertainty and external disturbance. The practical predefined-time stability is proved for the multiple rigid spacecraft system under the presented controller. It should be pointed out that the most important feature of the proposed estimators and controller is the tunable settling time characteristic. To be specific, based on ensuring that the settling time is less than the predefined value, the actual settling time of the system states can be further adjusted for different task requirements by a tunable parameter. Finally, some simulations are conducted to illustrate the effectiveness and advantages of the proposed tunable predefined-time control scheme.