Study On Dynamics And Control Of Spacecraft Formation Flying Near Lagrange Point

Based on the three-body dynamic model in deep space exploration, the formation flying technologies near Lagrange Point are systematically and deeply studied in this dissertation. In order to solve the dynamics and control problems in scheme design, the key technologies of formation flying are studied, together with talking about the there-body mechanical model and characters of the Lagrange points. The results may be helpful for the layout of the future formation flying missions, and provide theoretical and technological support and references for the coming deep space exploration tasks. The main contents of the dissertation are as follows:Firstly, the three-body formation dynamics and configuration problems are studied. The dynamics of the Lagrange points, including the frame establishment and stability, are analyzed. The analytic and correctional numerical periodic and quasi-periodic orbits near the Lagrange points are presented. Then, the three-body nonlinear formation dynamics with the fourth disturbance are built up for the coming control scheme. Meanwhile, based on the Halo orbit near the collinear Lagrange point, analytic studies are done to find the effects of changing the main system parameters. The relationship between the initialization time and formation form are studied for the nonlinear formation dynamics with the fourth acceleration disturbance, in comparison with the linear system. Besides, natural formation schemes are designed on Hamilton homenergic curves and differential correctional Halo orbits, to provide references for the parameter selection of formation flying systems.Secondly, the control system structure and station keeping problems near collinear Lagrange points are studied. From the view of control topology, the centralized and decentralized structures are analyzed respectively. The decentralized state feedback controller is derived according to the nonlinear formation dynamics. Then, after analyzing the periodic characters of the uncontrolled movements near the Sun-Earth collinear Lagrange points, the station keeping schemes are designed. The target-point method and Monodromy matrix based Floquet method are presented with simulations. Results show that in presence of initial orbit errors, the spacecraft can be controlled within some precision, so as to lay the foundation for the control of relative orbit or decentralized formation.Thirdly, the formation baseline maneuver and keeping problem near the collinear Lagrange point is studied. Linear and nonlinear schemes are studied respectively. Linear description of the formation is derived based on the equations of Chief and nonlinear formation dynamics, so as to design the linear threshold controller to realize the formation maneuver and keeping. Then, according to the high precision demand of the system, an improved nonlinear controller is proposed. Two RTBP models and the nonlinear state space description of the formation system are utilized to study the uncertainty problem of dynamical modeling. With considering the Moon acceleration and SRP disturbances, the adaptive neural network controller is designed to compensate the effects of modeling error and nonlinear disturbances.Finally, the formation flying problems near Earth-Moon triangular Lagrange points and corresponding interferometry technologies are studied. According to the particularity of the Earth-Moon triangle Lagrange points, the formation dynamic equations near Earth-Moon L4 are built up to study the tasks design and the formation configurations. Analytic relative motions are analyzed for in-plane formation, leader-follower formation, circular formation, and the effects of different initial values. Furthermore, ASPRO based simulations are carried out for different interferometric systems to draw some qualitative conclusions for parameter selection. Simulations are performed to find the effects of the spacecraft number and observation times on image reconstruction, so as to provide some references for formation tasks design near the triangular Lagrange points.