A preferred trajectory tracking steering law for spacecraft with redundant CMGs

Spacecraft which use control moment gyroscopes (CMGs) as momentum exchange devices in an attitude control system suffer from CMG configurations which preclude arbitrary torque generation. The exploitation of CMG null-space motion which exists in redundant systems allows the development of CMG steering laws which attempt to avoid these singular configurations. This paper presents a new singularity avoidance CMG steering law which operates by converging to a set of “preferred” trajectories in which no singular points exist. The underlying principle of CMG preferred trajectories as well as proof of the stability of the convergence process to these trajectories is presented. Simulation results demonstrating the convergence process as well as the resulting singularity avoidance properties are presented as well