Spacecraft attitude-orbit combined control analysis for flying-around and hovering task in super-close relative distance

Aimming at the requirement of relative motion control on chasing spacecraft in super-close distance towards targeter in on-orbit servicing tasks, methods of relative orbital control for flying-around and hovering as well as relative attitude control for viewing-tracking are presented respectively. Firstly, super-near relative orbital dynamical model is presented, flying-around trajectory is then planned and a expecting spot is set to facilitate the following hovering control design; attitude dynamical model using flywheel, as well as the MRP, a proper method for describing relative attitude motion are concisely introduced; the definition and motion law of sight coordinate system in flying-around mode is derived differently from that in hovering period, according to the instantaneous relative position and velocity. Secondly, LQG optimal relative orbital control law and robust sliding mode relative attitude control law are designed, based on the dynamical modeling result. The final simulation example illustrates the design effectiveness of this attitude-orbit combined control algorithm: the actual relative trajectory tracks the expecting one well while the chaser body attitude can keep pace with the sight coordinate system in high precision.