|Title:||Vibration analysis and active vibration control of the magnetically suspended flywheel rotor|
|Advisors:||Wong, Waion (ME)|
Flywheels -- Design and construction
Hong Kong Polytechnic University -- Dissertations
|Department:||Department of Mechanical Engineering|
|Pages:||xxiv, 194 pages : color illustrations|
|Abstract:||This 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 contents of this thesis contain five parts as following, Firstly, the vibration characteristics of the MSFW rotor are modeled and analyzed, and the stiffness characteristics and the damping characteristics are studied. The vibration transmissibility of MSFW rotor is affected by the damping coefficient of control system. The natural frequency of MSFW rotor is determined by the stiffness coefficient of control system. So, the vibration characteristics of MSFW rotor are controllable through tuning damping parameters and stiffness parameters of magnetic suspension system. Research contents in this part provide the theoretical foundation to the active vibration control of the MSFW rotor in the following parts. Moreover, the relationships amongst the vibration characteristics of MSFW rotor, the suspension span ratio and the moment of inertia ratio are studied. Based on the phase margin and the response magnitude, the vibration response of translational motion is regulated by tuning the control parameters. The frequency response of radial rotation is analyzed based on the open-loop poles of the rotational control loop. The critical whirling frequency of MSFW rotor is decided by the moment of inertia ratio, and the BW motion and the FW motion of MSFW rotor are affected by the suspension span ratio. This result provides a new method of analyzing the vibration response of MSFW rotor and the design guideline for MSFW rotor. In addition, the vibration absorbing ability of axial AMB in MSFW rotor is testified, and the axial AMB mounted at the suspension end of MSFW rotor is regard as a dynamic vibration absorber (DVA) model. Furthermore, the frequency responses of MSFW rotor considering the DVA model are researched. The vibration magnitude of MSFW rotor is suppressed by tuning damping parameter and stiffness parameter of axial AMB. Experiments are conducted to testify the effectiveness of axial DVA on tuning the dynamic characteristics of MSFW rotor, and the stiffness coefficient is regulated to suppress the dynamic displacement deflections of load rotor and MSFW rotor. The damping coefficient of axial DVA could then be controlled to enhance the stability of MSFW rotor. This part of research expands the application range of MSFW rotor on the active vibration control. Furthermore, for the MSFW system with great equatorial moment of inertia and great self-weight, the uncertainties about displacement stiffness and current stiffness cause disturbances on the stable control of the MSFW rotor. Therefore, robust control is applied to attenuate the influence on the MSFW rotor introduced by the uncertainties of current stiffness and displacement stiffness. Simulations about axial suspension of MSFW rotor is developed when a transient impulse disturbance, a harmonic disturbance and a random disturbance are respectively added on the MSFW rotor, and maximum displacement deflection from the balanced position is mitigated by the robust control function. Based on experimental results, the maximum displacement deflection from the balanced position using the robust control function is smaller than that with the proportional integral derivative control. These results indicate that the stability of MSFW system with great equatorial moment of inertia and great self-weight could be improved by using the robust control function. Finally, for the MSFW rotor great equatorial moment of inertia and great self-weight, the coupling effect in radial tilting becomes serious with increasing the rotating speed. So, an internal model control (IMC) method is designed to enhance the robust performance of MSFW rotor. Then, a decoupling control model based on the IMC model is applied to control the translation of the MSFW rotor on four DOFs. Simulations and experiments are performed to validate the IMC model for enhancing the anti-disturbance ability of MSFW rotor. The decoupling IMC model could effectively realize decoupling control in four radial DOFs of MSFW rotor.|
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