Abstract: The single-frame control moment gyro is the core component for attitude adjustment of two-wheeled vehicles.Carrying out research on the inherent properties and dynamics of the single-frame control moment gyro structure is an important prerequisite for its high-speed and miniaturization.In view of this,a joint Hypermesh-Ansys simulation and analysis model of the single-frame control moment gyro frame-bearing-rotor system coupling is established based on the finite element method,taking into account the multi-material rotor gyro effect,the support frame flexibility,the radial stiffness of the rotor bearing and other factors.On the basis of this model,the modal variation of the coupled system with inertia speed and the influence of the radial stiffness of the rotor bearing on the critical speed of the system are investigated; the accuracy of the critical speed analysis is verified by studying the unbalanced response of the single-frame control moment gyro rotor under a specific eccentric mass; the vibration characteristics of the frame and rotor of the coupled system are investigated under the steady-state rotor condition.The results show that the first-order inherent frequency of the coupled system decreases with increasing inertia speed,and the first-and second-order critical speeds of the system rotor stand approximately at 6 000 r/min and 11 500 r/min respectively; the sensitivity of the critical speed to the change of the radial stiffness of the rotor bearing is obtained,and a reasonable threshold range of 180～320 kN/mm is given for the radial stiffness of the rotor bearing of the coupled system.The vibration of the single-frame control moment gyro frame and rotor under steady-state conditions is revealed.The research results may provide insight into the engineering application and optimization of the control moment gyro.