Attitude Control for an Agile Satellite using Four Variable Speed Control Moment Gyros

Variable speed control moment gyros (VSCMGs) are powerful attitude control actuators for their combined functionality providing both reaction wheel mode and control moment gyro mode. Four VSCMGs in a pyramid configuration are used to control the attitude of an agile satellite aiming at earth-scanning observation. A strategy for roll maneuver together with its steering law of the VSCMG cluster, is proposed. Performance of the strategy and the steering law is examined through numerical simulation. The results show that the scanning mission is well implemented within the constraints of physical limits, and the errors are acceptable.