Disturbance observer-based adaptive integral sliding mode control for rigid spacecraft attitude maneuvers

This article considers the attitude tracking problem of a rigid spacecraft involving inertia matrix uncertainty and external disturbance. The adaptive sliding mode control is utilized for the attitude controller design. The major concern is reducing the switching gain generated by current adaptive sliding mode control, thereby alleviating the chattering problem. By eliminating the influence of initial tracking error from the switching gain adaptation, an adaptive integral sliding mode control scheme is first presented. As compared with current adaptive sliding mode control, a much smaller switching gain is produced. Then, a disturbance observer-based adaptive integral sliding mode control design is proposed to further enhance the result. To this end, the joint effect caused by external disturbance and inertia matrix uncertainty, referred as lumped uncertainty, is divided into a slow varying part and a rapid varying part. By compensating the slow varying component via a disturbance observer, the switching gain is only required to be larger than the upper bound on the rapid varying component. The effectiveness of the proposed strategies, especially the switching gain reduction ability, is verified by both theoretical analysis and simulation results.