Research On Attitude Control Of Combined Spacecraft With Partial Inertia Unknown

With the highly development of space technology, the on-orbit servicing technique, has won broad concern and has been studied intensively among spacefaring unions. As the service station and maintenance station in space, the on-orbit servicing spacecraft is the core carrier of on-orbit servicing technology. The role of on-orbit servicing spacecraft has gradually become more essential. In the context of on-orbit servicing technique, this dissertation mainly studies the attitude control problem of servicing spacecraft after it combines with the target spacecraft which goes out of control. The main contents are as follow:When the target spacecraft with payload loses control in space, a servicing spacecraft can be used to combine with it through rendezvous and docking process to further control its attitude. The quality character of combined spacecraft changes dramatically from the initial character of servicing spacecraft. Considering the large change of spacecraft is one main concern of the controller design in this dissertation. The uncertainty caused by reconfiguration of combined spacecraft, the value gained by estimated system is different from the real one, and unknown inertia of non-cooperate target spacecraft have also been considered in the attitude control design. In this paper, the combined spacecraft with given accurate inertia, with partial uncertainty and unknown target spacecraft have been considered and controllers have been designed respectively.When the inertia of target spacecraft is accurate given, considering the inertia of combined spacecraft changes greatly, an attitude controller based on pole assignment has been designed. The convergence rate of system remains when the inertia changes greatly.Considering the inertia value given by identification system which has an uncertainty with the real value and external disturbance, a sliding mode controller has been provided based on pole assignment. The parameters of controller have been designed and stability of system has been proved with Lyapunov theorem of stability. With comparison of simulation results, the controller is proved to remain good performance with small and large inertia and is robust to parametric uncertainties and external disturbances.An adaptive sliding mode controller based on pole assignment has been designed considering the large uncertainty of unknown target spacecraft. A time-varying gain of sliding mode controller has been designed using adaptive control theory to weaken the chatting of sliding mode. Numerical simulation results showed that the performance of the adaptive sliding mode attitude control is effective.The parameters of controller designed are related to inertia and designed pole. According to the indicators of system the poles can be selected and thus the controller can converge to equilibrium as expected.