Abstract: Abstract： A variety of errors and disturbances exist in control moment gyro (CMG) system, affecting the accuracy of spacecraft attitude control. This paper analyzes the characteristics of the main components of the largescale single gimbal control moment gyro (SGCMG) as well as errors and disturbances, including the static and dynamic imbalances of rotor, installation error of rotor axis, friction of bearing, characteristics of rotor motor and gimbal motor, harmonic gear drive. Numerical simulation results of the dynamics fine model of largescale SGCMG indicate that adding harmonic gear into gimbal servo system of largescale SGCMG significantly improves output torque accuracy, simultaneously brings highfrequency resonance to gimbal. The disturbing torque caused by dynamic imbalance of rotor is the main factor that results in output torque deviation in the direction of gimbal rotation axis and the output torque direction of SGCMG.

Key words: control moment gyro, dynamics, disturbance, modeling, simulation