Refined Disturbance Observer-Based Maneuver Control for Flexible Spacecrafts With Guaranteed Strength-Saving Performance

Attitude constraints of spacecrafts such as maneuver speed and pointing accuracy are expected to be satisfied with low control strength for many long-term space missions (e.g., laser communication link establishment). However, disturbances come from the maneuver-induced flexible vibration and the environment disturbances will degrade the attitude control performances significantly. In this paper, the disturbance dynamic is deeply excavated and described by a less-conservative disturbance model, where the relations among the disturbance dynamic, control input, angular velocity, and some other uncertainties have been revealed. A refined deep-coupled dynamic model constituted by the spacecraft attitude dynamic and the disturbance dynamic is thereby established. Then, in order to address the disturbances with low control strength, a strength-saving composite maneuver control law is proposed by combining a refined disturbance observer (RDO) and a prescribed performance sliding mode control (PPSMC). The proposed RDO can not only fully utilize the deep-coupled model information, but also quantify and preassign the disturbance estimation error. With the aid of RDO, a time-varying gain related to disturbance estimation error is designed in the proposed PPSMC, where the control strength can be qualified and reduced significantly. The attitude constrains can be satisfied by tuning the finite-time performance functions conveniently. Finally, simulation and experiment results are presented to show the effectiveness of the proposed methods.