Satellite Attitude Control Methods Using Only Magnetorquers
|School||Harbin Institute of Technology|
|Course||Control Science and Engineering|
|Keywords||Satellite Attitude Control Magnetorquers LQR Model Predictive Control Sliding Mode Control|
In recent years, research on small satellites has been paid great attention, and has become an important research area of space technology due to some“Faster Better Cheaper”characteristics for small satellites. Magnetic control system is attractive for small satellites, since the magnetorquers are relatively simple and lightweight, require low power and are inexpensive. The primary purpose of the work is to develop control laws for three axis stabilization of small satellites.The magnetic control torques are different from the traditional controller, which can only be generated perpendicular to the local geomagnetic field vector, and hence the satellite is instantaneously under-actuated. So far, this has prevented the application in practice using magenetorquers only. However, this paper presents the satellite model of a small magnetic actuated satellite with the constrainted control torques and environment model. Four magnetic controller designs are implemented for different missions, and their pros and cons are discussed via simulation.After provided the introduction to periodic linear system and the periodic linear model of satellite, a periodic time varying controller is presented based on LQR method and then examined its performance via simulation; At the same time a constant gain LQR controller is designed in order to reduce the computer burden on satellite, the stability of which can be checked by means of Floquet theory. The controller is also effective and with certain utility according to simulation results.Online receding horizon optimal strategy in Model Predictive Control is applied to magnetic attitude control problems in this paper to enhance the robustness of the system, a predictive control algorithm is designed with constraints on the control torque based on the discrete model of satellite, afterwards its stability is also analyzed. The simulation results showed that the control law designed has high steady precision and strong ability to mitigate interference.The last approach to the attitude control for a magnetic actuated satellite is based on sliding mode control considering the strong nonlinear in attitude maneuver missions. A stable controller is applied which can be easily used in practical based on the nonlinear model of satellite, and then a modification has been done on it combined with the constraints of magnetic control torque. The analysis of simulation results showed that the control law designed has fast dynamic response and strong robustness.