Gimbal angle feedback steering logic for spacecraft with control momentum gyros considering required attitude accuracy

This study proposes a steering law of Control Moment Gyros (CMG), which is used for attitude control of spacecraft. Recently, missions of spacecraft such as Earth-observing satellites have required increasingly rapid maneuvering and the CMG has been expected to be applied to the attitude control of spacecraft because it generates high torques. The CMG can generate torque by tracking the gimbal angular velocity to a reference angular velocity derived from a reference torque. However, the CMG has a singularity problem. At singularities, the CMG cannot generate the required torque in the case of a specific set of gimbal angles. Steering logic calculates the gimbal angular velocity for escaping singularities from an indicator of the singularity, and the associated additional torque may adversely affect the attitude control performance of the spacecraft. Near the singularity, the gimbal angular velocity for attitude control torque increases and the singularity escape performance is thus likely to be low. This study proposes a gimbal angle feedback steering logic that improves the singularity escape performance by controlling the gimbal angular velocity for attitude control torque. A design method employing feedback gain related to the singularity escape performance in consideration of the required attitude accuracy is proposed.