| In recent years,micro-satellites have developed rapidly.It is no longer confined to the stage of experimental satellites.Micro-satellites are widely used in engineering because of its low cost and fast development.The system of micro-satellites is a complex system like large satellites,and the attitude control system is the guarantee of the stable operation of micro-satellites on orbit.As the complexity of micro-satellites gradually increases,the requirements for micro-satellites control systems are also getting higher and higher.The focus of the attitude control system is the research of attitude control law,which is the guarantee for the high precision and high stability.In this paper,based on the background of an observation micro-satellite on low earth orbit,the controller part of the attitude control system is studied in order to achieve the three-axis stability during the orbit operation.The micro-satellite control system studied in this paper only uses the magnetic torque converter as the actuator,mainly because of our research is put on the part of the attitude controller,and ignoring the research on the part of attitude determination.This paper mainly focuses on the small-angle perturbation and large-angle maneuver of the micro-satellites to conduct the controller research.Furthermore,we take the space unknown interference situation into account.The magnetic compensation design is carried out according to the characteristics of the limited torque control during the magnetic moment.The design of the quasi-PD control law for mission satellite is carried out and the advantages and disadvantages are analyzed.According to the satellite small-angle perturbation,the satellite model is linearized at the equilibrium point.Based on the linearized model,a linear quadratic regulator control law is calculated to reduce the load on the on-board computer.The mathematical simulation shows that the quasi-PD controller and linear quadratic regulator(LQR)controller can control the micro-satellites stability and have certain engineering and practical value.For the large-angle maneuvering of micro-satellites,a sliding mode variable structure controller with fast response and strong robustness is designed in this paper.Due to the fact that the moment of inertia cannot be accurately measured and the unknown disturbance exists in the space,the sliding mode variable structure control is improved.According to the principle that the state observers can estimate state variables,the sliding mode extended observer control law is designed based on the sliding mode variable structure control.The attitude control system is dynamically compensated by the good estimation performance of the dilatation observer.The simulations of sliding mode control and sliding mode control are carried out respectively.The results show that these two control algorithms have the high stability,short stabilization time and strong suppression of interference. |
