| Bearingless permanent magnet synchronous motor is a new type of motor combined with the magnetic levitation technology and permanent magnet motor, which has the advantages of high power of permanent magnet synchronous motor, long life, high efficiency and small size. What's more, the wear and temperature rise of mechanical bearing can be avoided and the application space of the permanent magnet synchronous motor in the field of high speed and supper high speed has been expanded. The technical and economic advantages and a good prospect of application are obvious for its unique suspension mechanism and structure characteristics, which can not be replaced by the traditional electric motor.This dissertation focuses on a surface-mounted bearingless permanent magnet synchronous motor and the motor levitation force model, and the impact on the stability of the hanging, the features of electro-magnet design, motor control strategy and control of eccentric rotor displacement is deeply studied.The research significance of the bearingless permanent magnet synchronous motor, the recent research and development trends both at home and abroad is systematically discussed in the dissertation. Levitation mechanism and the operating feature of the bearingless permanent magnet synchronous motor have been analyzed. Considered the factors of permanent magnet, the field of windings and eccentric rotor, the mathematical model of levitation force and the complete mathematical model of surface-mounted bearingless permanent magnet synchronous motor have been analyzed and established from different point of views of Maxwell's force principle and virtual displacement principle.With the help of Ansoft software, the established mathematical model of levitation force is verified by means of Finite Element Analysis. The impact of current stator windings, rotor eccentricity, saturation, cogging effect and Lorentz force on levitation force has been analyzed systematically and deeply for the first time. The related laws have been researched.The research on the special problems and design features existed in the electromagnetic design of the bearingless permanent magnet synchronous motor is conducted. By analyzing the relationships among the demagnetization of bearingless permanent magnet synchronous motor, levitation force and the thickness of the permanent magnet and air-gap length, the maximum torque current of the demagnetization effect and suspended current expression are derived. The optimization of rotor design by establishing the law of function which can reflect the thickness of permanent magnet, air-gap length and levitation force is creatively put forward, which is verified by Finite Element Analysis. For the first time, the design feature of surface bearingless permanent magnet synchronous motor from the perspective of the system is analyzed and the electromagnetic design of the research prototype has been completed.For the characteristics of bearingless permanent magnet synchronous motor and the control strategy of permanent magnet synchronous motor, the rotor field oriented control strategy based on a complete mathematical model is improved by analyzing the possible strategy of bearingless permanent magnet synchronous motor torque and levitation force decoupling control. The simulation result shows that the strategy has a better function to forecast the actual system performance in the simulation study of bearingless permanent magnet synchronous motor. To solve the problem of eccentric rotor displacement control of bearingless permanent magnet synchronous motor, the fuzzy PID control strategy is led into the suspension control strategy of bearingless permanent magnet synchronous motor. Meanwhile, the new method of direct control of eccentric rotor displacement based on accurate controllable force suspended model and rotor flux orientation is put forward. The simulation shows that a more effective levitation force control performance of bearingless permanent magnet synchronous motor has been achieved under the levitation force control system constituted by the two control strategies.So far, the research of the surface-mounted bearingless permanent magnet synchronous motor described in this dissertation is not mentioned or not researched further by others in this area. As a result, the study has its value both in theory and practical application. |
