| Control Moment Gyroscope(CMG) is the main actuator of attitude control system for large spacecrafts and agile satellites. This dissertation focuses on a large magnetically suspended single gimbal CMG(SGCMG) which is designed for a space station. The structure optimization of key components, mechanical characteristics of magnetic bearing, dynamics characteristics of SGCMG, and imbalance vibration response and suppression are studied in detail. The main contents and innovative work include:(1) An overview of fundamental theory for CMG is carried. The configurations of magnetically suspended flywheel for space application in common use are summarized and compared with each other, and their advantages and disadvantages are analyzed. The four-axis-active configuration is selected for the the magnetically suspended flywheel of SGCMG and the structure configuration of the whole SGCMG is designed.(2) Structure optimization and mechanical analysis of key components for the magnetically suspended SGCMG are carried out. Rotor component of magnetically suspended flywheel is optimized with the sequential quadratic programming method. The values of interference for each mating face of the multilayer rotor are designed, considering the large centrifugal force. The distribution of stress and displacement for the rotor is calculated at the rated rotational speed. The elastic modes and its corresponding natural frequencies of the rotor are calculated for different rotational speeds. The stator component of the magnetically suspended flywheel is optimized with analytical method and the stiffness of the optimized stator is calculated with finite element method. The dynamics, statics and stability analysis is carried out for flywheel case of the SGCMG.(3) The mechanical characteristics of radial hybrid magnetic bearing for the SGCMG flywheel are studied with the equivalent magnetic circuit and finite element methods, respectively. The configuration and working principle of the RHMB are introduced. Based on the the equivalent magnetic circuits of the RHMB, structural parameters of bias and control flux circuits are designed with interation method. The air gap reluctance, magnetic flux distribution and magnetic force are calculated with an integral method and the conventional linear approximation method. The magnetic field and radial magnetic force are calculated with finite element method, and the coupling of magnetic flux and force between adjacent channels is also analyzed. The mechanism for passive stabilization of axial and tilting freedoms is analyzed, and the passive restoring force and moment and the corresponding passive restoring stiffness are calculated using the equivalent magnetic circuit and finite element methods, respectively. The influence of structural parameters on the passive stabilization is studied.(4) The dynamics characteristic of the magnetically suspended SGCMG is studied. The differential equations of motion for the gimbal-flywheel system of the SGCMG are deducted using the Lagrange method. The fundamental precession modes of the rotor are studied. The variation of precession frequencies with rotational speed is calculated for the flywheel rotor with a fixed and free gimbal, respectively. The influence of gimbal motion on precession frequency and critical speed is analyzed. Moving-gimbal effects of the SGCMG are studied. Based on feedforward compensation for gimbal angular rate, a method for suppression the moving-gimbal effects is proposed and simulated. The influence of accuracy of model parameters and time delay of the gimbal angular rate signal on compensation effects is studied.(5) The imbalance vibration response and suppression method for the flywheel rotor of the SGCMG are investigated. The imbalance state for a rigid rotor is analyzed, and the differential equations of forced vibration for the SGCMG flywheel under imbalance excitation are established. The imbalance responses of rotor translation and tilt are calculated, respectively, and the influence of imbalance vibration on control moment of the SGCMG is analyzed. The principle of active control for imbalance vibration is introduced. Based on generalized filter and compensation for displacement-stiffness force, an active control method for imbalance suppression is proposed and simulated. The influence of model parameter error on the active control is investigated. |
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