Researches On The Attitude Determination And Control System Of A Small Astronomical Satellite

This thesis took a small astronomical satellite as an example, deeply studied the attitude determination and control method for small astronomical satellites from both the theoretical and the engineering aspects. The main work done in this thesis is as follows:The performance of the Attitude Determination and Control System (ADCS) greatly relies on the precision of attitude determination, so this thesis focused on the high precision attitude determination mothod. The attitude sensors were modeled. Based on Extended Kalman Filter (EKF) algorithm, an traditional attitude determination scheme using Star Sensors and Gyros was studied, and proved not able to achieve the required precision. So a new idea called Instrument-in-Loop was presented what using the attitude information contained in the payload's data for the control loop. The simulation proved that the Instrument-in-Loop method can greatly improve the precision of attitude determination with low cost.The small astronomical satellite has demands on both pointing accuracy and attitude maneuverability, so this thesis modeled the attitude control subsystem based on reaction wheels. Under the fine precision pointing mode, A PD control law and a Variable Structure (VS) control law were studied respectively, and the simulation validated that VS control is more effective under fine precision pointing mode. Furthermore, the VS controller for rapid large-angle maneuver was also designed.In order to test the performance of the attitude determination and control methods presented in this thesis, the whole simulation loop of the small astronomical satellite's ADCS was constructed. The simulation results showed the methods represented in this thesis were effective and feasible.