Research On Modeling And Simulation Of Vernier Gimballing Momentum Wheel Supported By Magnetic Bearings

Vernier gimballing momentum wheel supported by magnetic bearings (VGMW) isa new kind of spacecraft attitude control actuator. The wheel is supported by activemagnetic bearings and its rotor can be tilted, thus it can control the attitude of thespacecraft on all three axes. Only one VGMW is needed to provide torques on all threeprincipal axes of inertia of the spacecraft. This dissertation mainly studies theoperational principles of the wheel, establishes the dynamic model and does research onthe simulation of the suspension control and tilt control of the wheel and the attitudecontrol of the spacecraft by the wheel. The main tasks of the dissertation aresummarized as follows.The operational principles of the wheel are analyzed by electromagnetics andmechanics. The dynamic model of the wheel is established. How the forces and torquesin the wheel are produced is analyzed and the expressions of the forces and torques inthe radial hybrid magnetic bearing and in the tilt magnetic bearing are derivated. Thenthe dynamic model of the VGMW is established.The dynamics of rotating systems and dynamics of gyros are applied to analyze thecoupling and imbalance of the wheel. The effect of the offset coupling of the sensorsgiven to the calculation of the radial displacements of the rotor is analyzed. Besides, theeffect of the static imbalance and dynamic imbalance to the movement of the rotor athigh speed is studied. The Campbell diagram is used to obtain the critical speed of therotor.The strategies of the suspending control and the tilt control of the wheel are putforward. In the radial direction, the rotor is suspended by a two-axis hybrid magneticbearing which is controlled by PD control method considered as a stable one. The PIDcontrol method is applied in the tilt magnetic bearings. The experiment result is given toprove that the control method is an effective one to suppress the conical whirling of therotor.The decoupling control of the spacecraft attitude based on the VGMW is designed.With the decoupling control method, the spacecraft attitude can be stabilized within therange of precision and the angle of the tilting of the rotor around the radial axis can becontrolled within the tolerance of the airgap in the magnetic bearing. The response of the angle around the radial direction under different kinds of disturbing forces isanalyzed. It is theoretically practicable to use the VGMW to accomplish the mission ofthe attitude stabilization of the spacecraft.