Research On Attitude Control Method Of Small Agile Satellite

Agile small satellites, due to its ability to acquire large angle maneuver in short time can acquire the date of non-subsatellite track quickly, so the satellite can get more date in single track. So it becomes to a popular reasearch field in recent years. In this paper, the agile satellite’s attitude control method of rapid large angle maneuver has been studied.Firstly, the dynamics and kinematics model of the agile satellite are established which is based on the hybrid actuators. The change of the moment of inertia caused by the frame rotating of SGCMGs is analysised. Then the configuration of the hybrid actuators which is made up of single-gimbal control moment gyros(SGCMG) and momentum wheel(MW) is designed and analysised.Secondly, by solving the optimal control problem the planning optimal trajectories are given out. The restrictions are analysised in the duration of attitude maneuver. Considering the time constraint and energy requirement in the rapid large angle maneuver, a weighted time and energy optimal expression has been proposed as the cost function of the attitude maneuver. Taking Gaussian pseudo-spectral method to solve this optimal problem which is accompanying with many constrains. Then the optimal control problem can be converted to nonlinear programming problems. It gives out the optimal planning trajectories of satellite attitude maneuver.Thirdly, the satellite’s attitude closed-loop new-type active disturbance rejection control(ADRC) method has been studied. The planned optimal trajectory has been set as the output of tracking differentiator(TD). Then based on the ADRC theory, an extended state observer(ESO) has been added to the inner control loop. The external disturbances and model uncertainty are observed and compensated by ESO, then the original nonlinear coupling system are converted to linear integral tandem system. Then the corresponding attitude control law has been designed for the linearized system. The nonlinear ADRC has excellent control performance, but the convergence problem of it is complicated. So the linear ADRC method has been proposed, the control parameters can be got through the linear method.Considering the singularity of the SGCMG system can not be avoided completely, in order to minimize the opportunity that the SGCMGs approaching singularity, a control method accomplished by hybird actuators has been proposed. Based on the hybrid actuator model which considering the change of moment of inertia caused by the frame rotating of SGCMGs, in order to raise the robustness of the system, a compound sliding mode control method has been used to provide the desried torque. Firstly, a simple switching control torque distribution law has been presented. When the conditions satisfy the chosen switching value, the MWs start to provide the desired control torque, which helps to mitigate the singularity of SGCMGs as much as possible. Since the output torque of MWs is limited, the advantage of hybrid actuator has not been fully used. Therefore, a new torque distribution law of the hybird actuator has been proposed. This torque distribution law is based on the real-time singular value decomposition, only the desired torque of the singular/quasi-singular direction has been distributed to MWs. Through this method, the hybrid actuator has better control performance for satellite attitude control.The research of the attitude control method about the agile satellite provides a reference program for the application of agile satellite.