AbstractThis thesis is focused on the vibration analysis and the active vibration control of the magnetically suspended flywheel (MSFW) rotor system, which has five degrees-of-freedom (DOF) with the control of the axial and radial active magnetic bearing (AMB). The main works of this thesis contain five parts as following,
Firstly, the vibration characteristics of the MSFW rotor are analyzed, and the stiffness characteristics and the damping characteristics are studied. The natural frequency of the MSFW rotor is determined by the stiffness coefficient, and the vibration transmissibility of the MSFW rotor is affected by the damping coefficient. So, the vibration response of the MSFW rotor is controllable by regulating the damping coefficient and the stiffness coefficient, this part of research provides the theoretical foundation to the active vibration control of the MSFW rotor in the following parts.
Moreover, the relationships amongst the vibration characteristics of the MSFW rotor, the suspension span ratio and the moment of inertia ratio are studied. Based on the phase margin and the response magnitude of the translational motion, the vibration response of the translation is regulated by tuning the control parameters. The frequency response of the rotation is analyzed based on the open-loop poles of the rotational control loop, the critical whirling frequency of the MSFW rotor is decided by the moment of inertia ratio, and the BW motion and the FW of the MSFW rotor are affected by the suspension span ratio. This result provides a new method of analyzing the vibration response of the MSFW rotor and the design guideline for the MSFW rotor.
In additional, the vibration absorbing ability of the axial AMB in the MSFW rotor is testified, and the axial AMB mounted at the suspension end of the MSFW rotor is regard as a dynamic vibration absorber (DVA). The dynamic responses of the MSFW rotor with the axial AMB are researched, the vibration magnitude of the MSFW rotor is suppressed by the damping coefficient and the stiffness coefficient of the axial AMB. Experiments are conducted to testify the effectiveness of the axial AMB on tuning the vibration response of the MSFW rotor, and the stiffness coefficient and the damping coefficient of the axial AMB could suppress the radial displacement deflection of the MSFW rotor, and then enhance the stability of the MSFW rotor. This part of research expands the application range of the MSFW rotor on the active vibration control.
Furthermore, for the MSFW rotor with heavy self-weight and great moment of inertia, the uncertainties about the current stiffness and the displacement stiffness cause disturbances on the stable control of the MSFW rotor. Therefore, the robust control is applied to attenuate the influence caused by the uncertainties of the current stiffness and the displacement stiffness on the MSFW rotor. Simulation about the stable suspension of the MSFW rotor is developed when the transient impulse disturbance, sinusoidal disturbance and random disturbance are imposed on the MSFW rotor, and maximum displacement deflection of the MSFW rotor is mitigated by the robust control. In the experiment, the maximum displacement deflection of the MSFW rotor using the robust control is smaller than that with the proportional integral derivative control. These results indicate that the stability of the MSFW rotor with heavy self-weight and great moment of inertia could be improved by using the robust control method.
Finally, the stability and control precision of the MSFW rotor with heavy self-weight and great moment of inertia are easily affected by the parameter uncertainty and external disturbances. The coupling effect in radial tilting becomes significant with the variation of rotational speed. Therefore, an internal model control (IMC) model is proposed to adjust the robustness of the MSFW rotor. Then, a decoupling model based on the IMC model is designed for the MSFW rotor with four DOFs. Simulations and experiments are conducted to verify that the IMC model could improve the anti-disturbance ability of the MSFW rotor with heavy self-weight and great moment of inertia, and the decoupling IMC model could effectively realize the decoupling control of the MSFW rotor.
|Date of Award||2021|
|Supervisor||Wai On Wong (Chief supervisor)|