Abstract:

The problem of the attitude tracking control for space fly-around mission, when the slave spacecraft is desired to observe the main one, is investigated, and a method of robust controller design, associated with such factors as flexible vibration, external disturbances, and parametric uncertainties, subject to control input saturation, is presented. According to the relative motion information of the mass centers of both spacecraft, the desired attitude to be tracked by the slave is calculated. To guarantee the boundedness and strong  robustness of the controller when the slave tracks the desired attitude, the extension of a first-order-sliding mode controller for attitude regulation given in existing literatures to the case of attitude tracking is attempted. Further, to eliminate the high-frequency chattering brought by the first-order sliding mode controller, the attitude tracking problem is transformed to that of standard second-order sliding-mode control, then a continuous and second-order sliding-mode control based attitude tracking controller is proposed. Simulation results show that the algorithm in the paper can achieve the goal of attitude tracking during the fly-around stage effectively, and has strong robustness.