Formation Control Methods For Drag-free Dual-satellites System

The data and information about the earth’ gravity with high precision and time varying is extremely useful and meaningful to modern earth research. The drag-free satellite offer the facorable conditions for Earth’s delicate information with satellite platform which provide ultra-low microgravity. And the formation of drag-free satellites adopt the method of cooperative work and has a lot of use value in high-precision space science mission. On this background, the formation control algorithms and disturbance rejection problem for Drag-free dual-satellite formation flying is investigated in this thesis in detail from both theoretical and applicable aspects, and the proposed control schemes is applied to a certain satellites formation control system. The main contents of this thesis are as follows.Based on the requirements of the frequency isolation between drag-free dualsatellites formation control system and drag-free control system, a non-diagonal quantitative feedback control algorithm is designed. Firstly, a study to the design method of the non-diagonal controller in comparison with the diagnol controller is carried out. It is concluded that the former is prior to the latter in the performance of decoupling. Then considering the control expectation in frequency domain and time domain, a non-diagonal quantitative feedback controller is presented to achieve the desired state reference tracking and input disturbance rejection. The simulation results shows the effectiveness of the control algorithm.In order to eliminate the strong coupling influence of different channel in Drag-free dual-satellites dynamic model, a state feedback control algorithm is proposed based on dynamic decoupling control using eigenstructure assignment. Firstly, the formation model is transformed to the weak coupling by the dynamic decoupling method. Then based on the eigenstructure assignment theory, the algorithm is eventually designed to enhance the robustness of the system and the capacity of disturbance rejection. According to simulation results, the controller is very effective and shows strong robust ability to disturbance.In order to improve the robustness of closed-loop system and reduce the convergence time, a practical finite-time control algorithm is proposed in the present of parameter uncertainty and disturbance. Firstly, a practical finite time control algorithm based on adaptive parameter identification is adopted to handle the high-frequency disturbance, and its stability is analyzed and its control performance is verified via simulation. Then, an input disturbance observer-based control algorithm is proposed for the specific form of modeled noise. The analysis of simulation results shows that the control law designed has fast dynamic response and strong robustness.