Spacecraft Angular Velocity and Line-of-Sight Control Using A Single-Gimbal Variable-Speed Control Moment Gyro

It is well known that complete attitude control of a spacecraft is not possible with only one single-gimbal Variable-Speed Control Moment Gyro (VSCMG) due to the conservation of the angular momentum. However, partial attitude control without violating the angular momentum conservation principle is still possible. In this paper, feedback controllers that stabilize the angular velocity vector of a rigid spacecraft with additional partial attitude stabilization using a single VSCMG are presented. A pair of angles is chosen to parameterize all feasible final spacecraft orientations at rest. Based on this parametrization, an LQR control law is designed to locally stabilize the spacecraft angular velocity, while also controlling a given spacecraft body-axis in inertial space. A multi-stage control law is also suggested to achieve the same control objective in the large.