ESA GNC Conference Papers Repository
Sizing and steering CMG arrays for agile spacecraft
Single-gimbal control moment gyroscopes (CMG) offer significantly greater vehicle acceleration (>100x) than a reaction wheel system of the same power. But the sizing and control of an array of CMGs is much more difficult than an array of reaction wheels. Gyroscopic physics, a time-varying Jacobian and the presence of singularities make this a subject of academic interest, but the spacecraft designer who values robustness over optimality finds little help in the open literature. An organization wishing to take advantage of the benefits of CMG technology often sees the need to develop a reliable control solution as an obstacle to entry. Honeywell has developed practical steering laws for 'roof' arrays of CMGs that can be embedded in momentum system products or licensed separately to CMG customers. They offer robust, deterministic, singularity-free management of the CMG array with guaranteed torque availability. Honeywell's approach has been extended to arrays of up to 8 CMGs, and more are possible. This paper will provide some theoretical background on the approach taken by Honeywell. The practical benefits of the approach will be discussed. It also provides practical guidance into the sizing of an array for specific applications.