Abstract
A new steering law of control moment gyroscopes (CMGs) is proposed to ensure extended life and to reduce the risk of failure. Because major failure modes of the CMG are aged deterioration and accumulated fatigue of the gimbal-axis bearing, the proposed method attempts to level gimbal angular displacements and to keep the manipulability greater applying a relation between the gimbal angular displacement of each CMG and the initial condition of gimbal angles. A suitable set of initial gimbal angles is selected using a defined evaluation function in an off-line preliminarily calculation. The evaluation function considers the average and variance of the gimbal angular displacement and the manipulability of the upcoming maneuver. The dynamics of a typical pyramid configuration of four single-gimbal CMGs was modeled and a numerical simulation was carried out to evaluate the performance of the proposed method. Numerical simulation confirmed that the proposed method levels the gimbal angular displacements of CMGs and keeps the manipulability greater, or suppresses radical motion of gimbals without degrading attitude control. The effective of the leveling of CMG loads was confirmed in the case that the CMGs do not pass a singularity.
