Study On Radial Displacement Self-sensing System Of Power Magnetic Bearing

Power Magnetic Bearing, also known as Bearingless Motors, has been proposed as a new type of motor in recent years. In principle, it is based on the general Motors. Two different sets of windings are installed on the stator, which enable the magnetic field provided by electromagnets not only to produce the radial force to support the rotor, but also to drive the rotor. Because of its simple structure, easy manufacturing, high reliability, suitability for ultra-high-speed operation, etc., the current research in the motor field has become a new hot spot.At present, the traditional magnetic bearings are widely used in industries. To detect the rotor displacement, 5 to 10 non-contact displacement sensors are needed. The existence of displacement sensor will increase the axial size of magnetic bearing system, and badly affect the dynamic performance and reliability. Also as a result of structural limitations, the sensor can not be installed in the middle of magnetic bearings, which makes the equations of the system coupling, and the design of system controller becomes more complicated. In addition, the high price of the positioning sensor results in the high price of the entire system of magnetic bearing, which will greatly limit its industrial applications.In this thesis, the expression of the levitation force considering rotor eccentricity is analyzed, and the mathematical modle between the self-inductance of levitation windings and radial offsets is derived, basing on the operating principles of the power magnetic bearing; the displacement detection circuit using high-frequency signals injectiong method is designed, basing on the radial displacement self-sensing principle of the magnetic bearing; the magnetic linkage relationship between the levitaton windings and torque windings, and the independent control algorithm of the levitaton windings based on U-I modle is given; the radial displacement self-sensing control system of the power magnetic bearing is designed, using DSP(TMS320LF2407A) as the main control chip.