An improved adaptive sliding mode control (ASMC) strategy is presented to address the robust attitude control
problem of uncertain rigid spacecraft. The proposed ASMC algorithm provides an effective solution for the over-adaptation problem in current ASMC design and removes the requirement of a prior knowledge of the upper bound of the model uncertainty as well. The advantages of the proposed method are twofold. Firstly, the resulting switching gain is much smaller and a lower-chattering control signal is generated. Second, the corresponding control torque is smoother, which is more suitable for engineering applications. Simulation results show the effectiveness of the proposed strategy.