Performance Analysis Of Inductive Sensors Based On The Integration Of Magnetic Bearings

With the development of modern industrialization,the requirements for miniaturization of rotating machinery,clean working environment,high speed and accurate control are higher and higher.Magnetic levitation motor is widely used in recent years because of its advantages of high speed,no friction and small volume.Active magnetic bearing(AMB),the key component of Maglev motor,needs to detect the rotor position in real time to change the electromagnetic force exerted by the stator core.The inductance sensor uses the change of self inductance or mutual inductance coefficient of the coil,which has good linearity and strong anti-interference ability.Firstly,the integrated structure of magnetic bearing and sensor is designed.In order to be suitable for magnetic levitation motor,the sensor structure size,coil turns and sensor excitation parameters are designed.The three-dimensional model is established in SolidWorks,and then imported into ANSYS Maxwell to simulate and analyze the magnetic circuit of the integrated magnetic bearing structure.It is determined that the control coil and the sensor coil form a magnetic circuit separately,and there is no mutual interference between the coils,which verifies the feasibility of the integrated structureSecondly,the circuit of the inductive sensor is designed.MAX038 chip is selected to generate the excitation signal,the signal detection and processing circuit is designed,and the sensor driving and conditioning circuit board is processed.Because MAX038 chip has limited capacity with load,its maximum working frequency can only be tuned to 0.94mhz,so two optimized circuit schemes are designed,mic1555 chip generates square wave signal and 4MHz crystal oscillator generates square wave signal.Finally,the static calibration experimental platform of the inductive displacement sensor is built to study the influence of the air gap,rotor material and coil turns of the magnetic bearing on the displacement measurement,and the influence of circuit parameters on the detection range of the sensor.The experimental analysis shows that the radial sensitivity curve(absolute value)is obtained in the effective measurement range of 1 mm and 0.6 mm;The axial and radial displacement detection accuracy of aluminum and stainless steel was compared.The magnetic bearing integrated inductive displacement sensor designed in this paper has simple structure and weak coupling between magnetic poles,which can meet the measurement accuracy requirements of Maglev motor,and provides a theoretical support for the research of magnetic bearing displacement sensor.