| Active magnetic bearing control system is a suspension system widely used in the world today.It can achieve high speed and high power density of the motor.It has the advantages of no contact,no friction and no lubrication,and has many applications in aerospace technology,production and processing,transportation and other fields.Magnetic bearing is an open loop instable system,which is composed of sensor detection,controller and electromagnet.In the control system,displacement detection is an important link,which is related to the control accuracy of the whole system.Therefore,the design of a stable and accurate displacement detection system has become the key to the operation of the magnetic suspension motor.The paper focuses on the detection system of eddy current sensor for magnetic bearing.It mainly contains the following components :（1）Based on the eddy current effect,the principle of the eddy current sensor is analyzed and derived.The transformer equivalent circuit model is established to derive the relationship between coil impedance,figure of merit and displacement.The formation range of eddy current is discussed,the relationship between eddy current strength and outer diameter,and the skin depth of different materials are studied.Analyzing on the coils of single turn,multi-turn and single layer,the relationship between the effective distance and the outer diameter and the influence of the inner and outer radius on the quality factor are concluded.（2）Based on finite element theory,Ansys Maxwell simulation software is used to compare and analyze the sensor detection materials,and to take a simulation analysis of various important size parameters,such as outer diameter,inner diameter,thickness,and excitation frequency,etc.to conclude the influence rules of sensor performance under various parameters.According to the combination of theoretical analysis and simulation rules,the probe size of the eddy-current sensor is determined,and the probe skeleton and fixed package are designed.A hand-cranked winding mechanism is used to make a pair of probe coils which are almost identical.（3）According to the detection characteristics of the eddy-current sensor,the detection circuit scheme is proposed,and the Multisim simulation software is used to verify the feasibility of the detection circuit.The software is used to calculate the values of the key parameters in the detection circuit,and the method of best matching the resistance and capacitance is obtained,and the anti-electromagnetic interference,high-speed and stable detection board is designed and produced.（4）According to the actual use of magnetic bearings,the differential static calibration scheme is proposed,the static displacement calibrator for differential calibration test is modified,and the experimental platform is built for static testing.The input and output characteristic data of the displacement sensing system is measured to analyze and obtain its linearity,sensitivity and other characteristics. |
PDF Full Text Request