SUBOPTIMAL COMMAND GENERATION FOR CONTROL MOMENT GYROSCOPES AND FEEDBACK-CONTROL OF SPACECRAFT

This paper presents a suboptimal gimbal-angle command generation techn ique and a Lyapunov-based tracking control law for control moment gyro scopes. The formulation of the open-loop maneuver problem exploits the principle of conservation of angular momentum. This allows for a redu ction in the dimensionality of the problem-only the kinematics need be considered. The gimbal rates are parametrized as polynomial functions of time, and the parameters are optimized. The objective function of the optimization is the singularity measure. The optimal null motion u sed is determined after computing the open-loop gimbal-rate profiles. A feedback strategy is used to track the open-loop reference attitude and angular velocity profiles. Null motion is also used to allow the c losed-loop gimbal angles to follow the open-loop gimbal-angle historie s. This procedure avoids neighboring singularities and also provides r epeatability. Simulation results are presented for rest-to-rest maneuv ers using a model of a ground-based test article. The results show tha t a wide domain of singularity-free operation around the reference sol ution can be provided with this approach.