LQG/LTR spacecraft attitude control

The control of pitch attitude and pitch momentum of an Earth-orbiting spacecraft using loop-shaping techniques based on the linear-quadratic-Gaussian/loop-transfer-recovery (LQG/LTR) methodology is considered. Attitude is measured by an Earth horizon sensor, and control torque is produced by magnetic torquer bars and a pitch momentum or reaction wheel. The controller must achieve good tracking, environmental disturbance rejection, and robustness to modeling errors. Loop-shaping filters are used so that the roll and yaw magnetic torquer bars control pitch attitude at low frequency, while the pitch wheel controls pitch attitude at high frequency. The controller design and the simulation results are presented and discussed.