Study On Inductive Displacement Sensors For Magnetic Bearings

Magnetic bearing has the merits of contact-free,no lubricating,controllabe rigidity and damping,etc.Therefore,it is widely applied in many fields such as industry,national defense,aerospace etc.The performance of active magnetic bearing is confined by its control system.However,the sensors restrict the control performance.The inductance sensor has the advantages of small signal attenuation, good antijamming ability and so on,so it is good for improving the control performance of the magnetic bearing.In this paper,an inductive displacement sensor is studied,aming at improving the precision of the magnetic bearing's control system, therefore makes the foundation for designing the magnetic bearings with high speed (60000r/min) and high accuracy.The mathematical model of the differential transformer inductive sensor that applied in the magnetic bearing has been established.According to the existing magnetic bearing's characteristic and the magnetic bearing system's requirements of the sensors,the sensor's parameter has been designed,including the basic size of the probe,the coil's number of windings and wire diameter,the stimulus signal's frequency and its peak-to-peak value etc.The magnetic field analysis of the sensor's probe has been carried out using ANSYS,the magnetic field distribution in the probe has been obtained,thus confirms the structural design.The magnetic flux-displacement relationship has been analyzed,thus determined the sensor's general linear measurement scope.The phase sensitive circuit has been designed and manufactured as the sensor's measuring circuit,each main part of the measuring circuit has been simulated with Pspice,thus has confirmed the correctness of the principle,and carried out the optimize design of the circuit's parameter.The static calibration for the differential transformer sensor has been carried out.The results of the study on static state indicates that,the developed sensor takes on wide linearity range,good linearity,high sensitivity,it is suitable for the magnetic bearing's control system.On one hand,the work done in this paper provides a special position sensor for the magnetic beating control system,on the other hand,it founds some certain theoritecal foundation for the self inductance type(non-sensor type) magnetic bearing.