Adaptive sliding mode control for spacecraft attitude maneuvers with reduced or eliminated reaching phase

This paper aims to present an improved adaptive sliding mode control (ASMC) design for rigid spacecraft attitude maneuvers. An adaptive scheme is proposed for the switching gain calculation when the upper bound of the system uncertainty is unknown in advance. Unlike existing ASMC design, which may result in an over-adaptation of the upper bound when the initial system trajectory is located far from the sliding surface, this paper presents a novel ASMC strategy by introducing a decay term in the sliding function to reduce or eliminate the unrelated factor in the adaptation scheme. Consequently, a lower-chattering control signal is achieved. Simulation results are presented to illustrate the effectiveness of the proposed strategy.