Satellite Formation Flight Dynamics And Control Technology Research

With the development of space technology, modern small satellites are becoming more and more mature, and will have increasing effect on modern society. The concept of satellite formation flying has provided new application directions and developable space for small satellites, and has received much attention. This paper is to study the relevant issues of satellite formation flying from the point of view of dynamics and control.Based on the two-body assumption, two methods are used to investigate the mechanism of satellite formation flying on circular or near-circular orbits. In the dynamic method, starting from the analytical solutions of the CW equations, the flying-around orbit is proved to be an ellipse centered at the reference satellite, and its description parameters are presented, hi the kinetic method, flying-around conditions and equations in kinetic form are obtained by first order approximating, and the description parameters of the relative orbit are given. Then, emphasis is placed on circular and projected circular flying-around orbits. Based on the flying-around equations, mechanism of flying-around formation is showed, followed which the orbit design is investigated with two methods. In addition, relative motion between flying-around satellites is analyzed and formations of non-flying-around case and complex case are discussed.Much attention is paid to the effect of perturbations on satellite formation flying and how to decrease the effect, which are studied with the Earth oblateness and atmospheric drag considered. First, bulk and relative perturbation of J2 term are solved and analyzed based on the CW equations. Based on the first order perturbing solutions, the thesis obtained the long term relative perturbation of equal semi-major axis formation, which is removed by adjusting semi-major axis of the flying-around satellite. The effect caused by the atmospheric drag is investigated also.Satellite formation flying on elliptic orbits is studied in this thesis. In the two-body case, the approximate equations of relative motion on elliptic orbits are derived. On this basis, several formations are discussed with emphasis on the flying-around one. Based on the first order perturbing solutions due to the Earth oblateness, the long term relative perturbation of equal semi-major axis formation is analyzed, which is removed by adjusting semi-major axis of the flying-around satellite.Satellite formation keeping and control, which is one key technique of formation flying, is investigated deeply. After summarization of formation control tasks, a hierarchical control structure is presented. Based on two-impulse optimal control for relative motion, the formation planning problem is solved. With different dynamic models for relative motion, two nonlinear controllers without velocity measurements are obtained. One is obtained with the exact nonlinear model by designing a filter to avoid measurements of relative velocity. Using the linear model with disturbances, the other law is designed to be robust based on the linear quadratic optimal control and the state observer of linear system.The problem of attitude tracking maneuvers of satellite is studied with MRPs. With limited disturbances considered, sliding mode control is used to design the controller, which ensures the sliding mode to be exponentially converged and the sliding manifold to be reached in limited time from any initial states. And an adaptive law is designed for the unknown inertia matrix.