Research On Distributed Coordination Control For Spacecraft Formation Flying

In recent years, more and more aerospace research institutions develop thespace missions which are fulfilled by multiple spacecrafts formation flying.Meanwhile as the applications of the consensus algorithm to the distributed controllaws of the first and second order integral dynamical systems are becoming moreand more mature, how to apply the consensus algorithm to the cooperation controlof spacecrafts formation system gets more and more attention of the scholars andexperts at home and abroad. By surveying existing research results on thespacecrafts formation flying control and consensus algorithm, the dissertationmainly research on the coordinative attitude and relative position control laws of thespacecrafts formation system based on consensus theory. The main contents of thedissertation are as follows:In order to solve the coordinative attitude control problem of spacecraftsformation flying, the attitudes and angular velocities of the spacecrafts wereintroduced, by which the spacecrafts could communicate with each other, and then acooperative attitude control law is designed based on the consensus algorithm andundirected communication topology. Then extending this control law to thesituations that the controller contains time-varying weighted cooperation controlparameters, the desired states can be accepted by the sliding-mode estimator, and thedirected communication topology, several control algorithms are proposed toimprove the accuary and the dynamic performance of relative attitude errors, toreduce the communication pressure of the ground station or the leader spacecraft, tocooperatively converge to desired attitude in finite-time, and to overcome thespacecraft physical parameters uncertainty and external disturb torque. It isvalidated by the simulation results that the above distributed control strategies cansolve the spacecrafts formation attitude cooperative problem better and are morerobust, compared to the traditional centralized control of the leader-followerstructure.The time-delays of information transmission is usually inevitable among thespacecrafts which communicate with each other in the formation. Taking this intoaccount, proper Lyapunov function is chosen to propose a distributed variablestructure attitude cooperative control law, meanwhile the condition of thedelay-independent stability is found. Furthermore, the range of the controlparameters is given when the tracking performance is evaluated by L2-gain from thedisturbance input to the penalty output of the control system. In addition,considering the input time-delays of the relative control part, this control law is extend to the situation of the directed communication topology, a new distributedcontrol strategy is designed and the delay-dependent stability condition is found,thus the conservative of the delay-independent stability condition is reduced. Finally,a finite-time sliding-mode estimator is introduced in order to release the heavycommunication pressures of the earth station or the leader spacecraft. Simulationresults are presented to demonstrate the effectiveness of the two control schemeswith time-delays.An output feedback attitude cooperation tracking control law is proposed byonly using the absolute and relative attitude measurements when there are noangular velocity sensors, and the constant disturbance torque can be overcomed bydesigning the filters with integral term. In addition, the condition of the underictedcommunication topology is proved when the desired attitude only can access to apart of spacecrafts. Based on the above attitude coordination control law withtime-delay, an attitude cooperation tracking control law is proposed without usingexplicit angular velocity, the results of which are also extended to the situation thatcontains the input time-delays of the relative control part, then thedelay-independent and delay-dependent stability conditions are given respectively.The simulation results show that the distributed output feedback control laws canmake multiple formation spacecrafts to track the dynamic desired target and havegood accuracy even without the angular velocity measurements.Based on the relative position dynamics in the orbit reference of the leaderspacecraft, a distributed position cooperation tracking control law is designed,taking into account the effect of the attitude control due to the relative positionamong the spacecrafts in the formation. The stability analysis of the formationsystem is performed under the dericted communication topology. Further more,using the relative positions among the spacecrafts, the desired attitude quaternionand angular velocity can be determined for the requirement of thespecific communication measurement task. Like the above case of attitude controlwith time-delay, a distributed adaptive cooperation control law with communicationtime-varying delays is proposed without any velocity measurements. Numericalsimulation results are presented to show the effectiveness of the proposedcontrollers for the relative position of the spacecrafts in the formation.