Relative Orbit And Attitude Control Methods For Spacecraft Formation Flying

With the rapid development of space technology,formation spacecraft flying has become a research hotspot in the field of aerospace,and has attracted more and more attention from space research institutions.Compared with traditional single spacecraft,formation flying spacecraft has the advantages of low cost,high flexibility and reliabil-ity.Thus,formation flying spacecraft is more suitable for complex space missions.For spacecraft formation missions,effective orbit and attitude control of spacecraft is the key to success or failure.This thesis will make a detailed analysis and investigation of the relative orbit control for two spacecraft formation and coordinated control for multiple spacecraft formation.The main contents are as follows:For the problem of multi-constraint impulse control for formation spacecraft,a state observer-based impulse covariance controller is proposed.Considering the uncertainties of model parameters and external disturbances,the uncertain linear system models are established for the case of circular and elliptical orbits of the leader spacecraft respec-tively.Considering the incomplete measurability of relative position and velocity,a full state observer is designed.Based on observer,multiple constraints impulse variance con-trol strategy is developed to solve the stabilization problem in the presences of parameter uncertainty,poles constraint,variance constraint and limited-thrust.Numerical examples are established to demonstrate the effectiveness of the proposed control approach.For the problem of high precision tracking control for formation spacecraft,an adap-tive sliding mode variable structure fault tolerant controller is presented.Considering the thruster fault,a fault model is established.In the developed approach,by using adaptive algorithm is employed to estimate the external disturbance and thruster fault.Based on the estimation information,an adaptive sliding mode tracking controller is designed.This controller does not need precise information of external disturbances and thruster fault.The Lyapunov method is used to prove that the closed-loop system is asymptotically sta-ble despite external disturbances and thruster faults.A numerical example is established to illustrate the effectiveness of the proposed control approach.For the problem of relative orbit coordinated control for spacecraft formation,a finite-time coordinated controller under an undirected topology is developed.A fast ter-minal sliding mode control strategy is designed under an undirected topology.In order to improve the control accuracy,a RBF neural networks is employed to approximate the un-certainty of the system and bounded external disturbances.Besides,a switching function is introduced to ensure the output boundedness of RBF neural network.Based on the fast terminal sliding mode and RBF neural network approximation,a distributed finite-time synchronization control law is designed.Moreover,a distributed finite-time coordinated control scheme with communication delay is given.A numerical example is illustrated to demonstrate the effectiveness of the proposed two control strategies.For the problem of coupled attitude and orbit coordinated control for spacecraft for-mation,a fixed time coordinated controller under a directed topology is developed.A multi-spacecraft fixed time sliding manifold is derived.Considering the upper bound of bounded external and system's uncertain parts is known,based on the designed fixed time sliding mode,a coupled attitude and orbit fixed time coordinated control law is given.Moreover,considering the upper bound of bounded external and system's uncertain parts is unknown,a coupled attitude and orbit adaptive fixed time coordinated control law is developed.The numerical simulation results show that the proposed two control strate-gies can ensure that the relative position and attitude errors between formation spacecraft achieve good convergence accuracy in a fixed time.