| The Magnetic Bearing(MB) has great advantages over conventional mechanical bearing in many fields, especially in high speed and vacuum circumstances. This dissertation focuses on the integration technology in the Magnetic Bearing System including permanent magnet biased axial-radial magnetic bearing, bearingless induction motor, novel switching amplifier used in MB and robust control of MB. The integration technology in the Magnetic Bearing System can simplify the system, reduce over system size, possibly improve rotor dynamics and simplify control, and inherently reduce cost.A permanent magnet biased electromagnetism bearing (PMEB) with three degrees of freedom that combines the radial and axial actuator into one combination permanent magnet biased axial-radial magnetic bearing is presented. The mechanism of operation of the actuator is defined. Compared with a standard bearing of similar capacity the new design shows some advantages in size, losses, and costs. One downside of the integrated bearings is increased coupling between the radial and axial degrees of freedom. The analysis of coupling is done by method of an electric circuit analog of the integrated magnetic bearing. The basic equation of magnetic circuit and the equation of suspension force are derived when permanent magnet flux and electromagnetism flux simultaneity is effected. The basic performance limit expressions about this novel MB is derived in order to design it. The novel magnetic bearing is analyzed employing the Finite Element Method and has been integrated into a test facility with very simple control method, and the results of selected experiment have been provided. The lack of cross-coupling between radial and thrust axes has been seen in tested units, confirming the model results. And a new radial MB is presented based on permanent magnet biased axial- radial actuator, the model of this MB is defined.Bearingless motors are high speed electric machines combined with radial magnetic bearing functions. The compactness of bearingless motors suggests the possibility of high power and high speed motors. In this dissertation, the modeling and analysis of levitation force are presented in a bearingless induction motor. Firstly, a modeling for levitation force control is developed based on the theoretical analysis. And flux distributions and radial force of an induction type bearingless motor is analyzed employing the Finite Element Method. Relationships between the radial force and radial force winding currents are influenced by magnetic saturation. It was shown that the generated radial force reaches its maximum value due to magnetic saturation. The mechanism of radial force is defined and the analyzed results will be applied to derive more precise radial force model.A new bearingless induction motor system with five degrees of freedom is developed including a bearingless induction motor and a permanent magnet biased axial-radial magnetic bearing. The control strategy of bearingless induction motor based on air-gap flux orientation is introduced, and the decentralization PID control is used to maintain equal airin the five degrees of freedom. The digital controller guarantees rotor suspension steadily, and the speed of rotor reaches 3000 rpm.A novel magnetic bearing system with five degrees of freedom is designed including a permanent magnet biased axial-radial magnetic bearing, a permanent magnet biased radial-magnetic bearing and high speed permanent magnet synchronous motor. The nonlinear modeling and linear state equation of this system is built, and H∞ control theory is employed in designing the controller for robust stabilization and disturbance attenuation of the magnetic bearing. By using the hybrid-sensitivity scheme, a H∞ controller is devised and H∞ control in the new MB system is compared with that of PID control.The standard bi-state magnetic bearing amplifier have some disadvantages such as high current harmonics, low reliability and the current mode switching for tri-state amplifier is expounded. The ba...
|
PDF Full Text Request