Research On Control And Application Of LEO Spacecraft Formation Flying

For its advantages in technology and its vast field of application, Spacecraft formation flying(SFF), a new mode of spacecrafts motion., has been a hot point since it appeared and is called as a kind of technology that representing the developing trend of space technology. At the same time, there are a lot of challenges in dynamics, control and application.Based on the excellent feature and the wide application of low earth orbit (LEO), the Problems about SFF in LEO, including formation design and dynamics analysis with perturbations, formation establishing, formation maintenance and reconfiguration problem, whole formation orbit maneuvers, design and optimization and coordinated control of SFF system for InSAR measurement, are systematically studied in the dissertation. What's more, there is a discussion on the method and the ability of local space control with SFF. The main contents are as follows:1. In the analysis of formation dynamics, the orbital constraints of stable formation are provided considering the gravitational perturbations. A method based on three orthogonal directions synchronized to design formation is presented. Based on spacecraft orbit theory, expressions to describe formation secular movement considering the J₂ perturbation are educed. It is proved to be in a high precision with numerical simulations.2. The method to establish formation with impulses is studied. Two approaches to establishing SFF are provided: one is to utilize the impulses in radial direction and in cross-track direction, the other is to utilize the impulses in along-track direction and in cross-track direction. The methods are proved simple and practical with simulations.3. The basic frame of formation maintenance is structured and the formation control effect with different thrust models is analyzed. It is theoretically proved that three models of thrust—impulse thrust, continuous thrust and Bang-Bang thrust are equivalent in formation control. The method of transformation among the thrust models is also presented.4. Reconfiguration of SFF with micro-thruster and simple four-impulses is discussed respectively. A novel idea and two corresponding low level control methods with continuous micro-thrust to reconfigure are raised, and two low level control methods are provided, and the expressions estimating fuel consumed (ΔV budged) are educed. Then, the reconfiguration problem of simple SFF comes down to solving algebra equations, while the reconfiguration problem of complex SFF are expressed to general assignment problem (GAP), and the best solution can be obtained with ant system (AS) algorithms. At last, a low level control method with simple four-impulses is presented, and the magnitude and the time of control impulses are expressed as formation parameters. All the upper methods are applied to the reconfiguration example of SFF with 10 spacecrafts. Simulation results demonstrate the efficacy of the proposed approachs.5. The multi-impulse method of orbit maneuvers based on the primer vector theory is applied to maneuvering problem of SFF for the first time. To avoid impulses' being too large, the idea of path-planning for multi-impulse orbit maneuvers of satellite formation is presented, and numerical simulations show that the method provided here is simple and practical.6. Considering spaceborne Interferometric Synthetic Aperture Radar (InSAR) systems as the application of SFF for achieving highly accurate digital elevation models (DEMs) on a global scale, the requirement of Global Single Instantaneous Access Effective Coverage (GSIAEC) and some restrictions on orbit are put forward. Thus two ideas about coverage are provided. Based on a new technique of adjusting and controlling formation, the whole model of design and optimization of formation and orbit of SFF is summed up. A logic structure discovers the essence, and simulation results show that the method can solve the problem and be of general meaning.7. The coordination control of formation and attitude of concomitant satellite formation in spaceborne InSAR system is studied. The coordination architecture with an orbit coordinator and an attitude coordinator is presented, which illustrates the approach to the coordination problem. Then, formation planning methods, attitude planning methods and laws of coordination control are respectively studied. At last, numerical simulations indicate the architecture of coordination control is feasible.8. The methods to control local space with SFF are discussed. Two kind of application concept of SFF in space orbit blocking, which are destroying SFF and disturbing SFF. The abilities to control local space with SFF based on impulse control and micro-thruster control are explored respectively. Results show that SFF with 20% mass of fuel can control space in a range of 200km at least.In conclusion, by analyzing and simulating, it mainly studies the problems in dynamics, control and application of SFF in the dissertation and proposes some methods on the control and the application of SFF, which can provide ideas for the study of SFF in other orbits, and be of some help to the development of distributed spacecraft system (DSS) of china.