Parameter Optimization And Performance Experiment Of Self-inductive Sensor

Because of having no contact,high speed,low power consumption and easily being maintained,active magnetic bearing has a wide range of applications in the field of rotating machinery and applications are still very broad.According to rotor displacement detected by the displacement sensor,the active magnetic bearing needs to change electromagnetic force with real-time and achieve stable suspension of the rotor.Therefore,the performance of the displacement sensor is one of the main factors that affect the performance of the magnetic bearing.At present,inductive displacement sensors are widely used in active magnetic bearing systems.In order to further improve the performance of the sensor,it is necessary to study the variation of its performance with parameters.It is also the focus of research in this field that looking for parameter optimization methods.The mathematical model of differential self-inductance displacement sensor is derived and its output characteristics are analyzed.Based on the requirements of sensitivity,linearity etc,a method for determining the balance air gap of the sensor is given.Radial self-inductance displacement sensors with air gaps of 1.6mm,1.2mm,1.0mm,0.8mm and 0.6mm are designed for a magnetic suspension rotor with a diameter of 44.2mm in the laboratory.The electromagnetic field finite element software is used to simulate the relationship between output voltage and the rotor displacement,and the effects of balance air gap and coil turns on sensitivity and linearity.Theoretical analysis shows there is a good linear relationship between the output voltage of sensor and the rotor displacement.The sensitivity sensor is proportional to the supply voltage,and is inversely proportional to the balanced air gap.In the small displacement range,it can be considered that the coil inductance and current vary linearly with the rotor displacement,but in the large displacement range,there is a strong nonlinear relationship.The theoretical analysis shows that the relationship between the output voltage,the inductance and current of the coil and the displacement is consistent with the trend shown by the simulation.However,there is still a certain error in the numerical value,and the simulation value of sensitivity is significantly lower than the theoretical value.The reason for the error is mainly because it is assumed that the iron core coil is ideal,all fluxes are closed by the rotor core,no magnetic leakage and the effect of eddy currents in the core on the inductance of the coil is not considered.Therefore,it is quite different from the actual situation.The output signal of the sensor is a modulating signal,which must be demodulated and filtered to obtain a DC voltage signal that reflects the rotor displacement.This paper designs a sine wave generation circuit based on MAX038,a power amplifier circuit based on TDA7294,a detection circuit based on AD633,a butterworth low-pass filter circuit and a bias and amplitude modulation circuit.For the drive and measurement PCB of the self-inductive displacement sensor,the demodulation performance and thermal stability of the measurement circuit are tested by AFG-2225.The experimental results show that the measurement circuit meets the relevant performance requirements.In order to verify the theoretical analysis results,a self-inductance displacement sensor static calibration experiment platform is designed.Static experiments studied the effect ofbalance air gap and coil turns on sensor performance.The experimental results show that the designed self-inductance displacement sensor has good sensitivity and linearity,and the sensitivity can reach 25.22V/mm within±0.4mm,and the sensitivity sensor is inversely proportional to the balanced air gap,and the effect of coil turns on linearity,delaying and repeatability is negligible,and as the number of coil turns increases,the sensitivity of the sensor increases slightly.The experimental results verify the conclusions of theoretical analysis,but the experimental values of sensitivity are significantly smaller than the theoretical and simulated values.This paper provides theoretical guidance,design method and experimental value for the design of self-inductance displacement sensor of magnetic bearings.