Study On Micro-satellite Attitude Control System

Since the concept of micro-satellite was proposed in the 80's 20 centuries, its techniques have made great progress in recent years, the development of which is a significant trend in the aerospace area. As a key section of micro-satellite, the micro-satellite attitude control system should have the feature of simple configuration, light weight, high reliability and low cost. In this paper, taking a specific micro-satellite'attitude control system as an example, the method of micro-satellite attitude determination,magnetic attitude control and their hardware realization are studied. The main work done is as follows:At first, the attitude representation of Euler Angle and Quaternion are analyzed and generalized. Then the attitude kinematics and dynamic models are developed. The models of environmental torques are also discussed.About attitude determination: the attitude sensor's measure theories are studied and their measure equations are established. Then, the deterministic method, including TRIAD and QUEST algorithm which determine the attitude from double vector observations and a simple attitude determination method using infrared earth sensor and magnetic vector, are presented. Based on state estimation, an extended kalman filter algorithm by fusing the data from sun sensor, magnetic sensor and infrared earth sensor is built. In order to reduce the calculation, a decoupled kalman filter algorithm using magnetic measurement only is designed. All of these attitude determination algorithms are demonstrated by simulation.About active magnetic attitude control: the work theory of magnetorquers and the characteristic of magnetic torque are analyzed at first. Then, the velocity damping magnetic control of satellite during the initial entering orbit is discussed. Based on the kinematics characteristic of biased momentum satellites, the magnetic control law for both of the pitch channel and roll/yaw channel are designed. Because the flywheel may stop running, the magnetic control algorithm for gravity gradient micro-satellite is studied too, The PD feedback control law based on Euler Angle and Quaternion are provided separately. All of these control algorithms are demonstrated by simulation, too.At last, the hardware realization of the attitude determination and control algorithm is simply discussed. Take the EP2S60F1024C4 chip, a mainstream product of Altera Co., as the goal FPGA device, the decoupled kalman filter algorithm and control algorithm for biased momentum micro-satellite is realized in VHDL. Based on the toolbox"Link for modelsim", a micro-satellite Attitude Control Simulation System is built using Matlab and Modelsim. The simulation result shows that the hardware realization of the attitude control system in this paper is valid.