Observer-Based Practically Prescribed-Time Attitude Control for Flexible Spacecraft

In this paper, the practically prescribed-time attitude stabilization problem for flexible spacecraft with unknown disturbances is investigated. By designing an extended modal observer, the flexible vibrations and disturbances are compensated. Compared with some existing results on the flexible modal observers, an appealing feature in the current design is that the estimation errors of flexible vibrations converge faster. To establish the practically prescribed-time control scheme, a state-scaling transformation is introduced by time-varying functions. Additionally, with the aid of the presented observer and an adaptive law, the attitude achieves practically prescribed-time stability. At last, numerical simulations are presented to show the effectiveness of the proposed control method.