Research On Design Method Of Fluxgate Sensor Based On ANSYS

The fluxgate sensor is a weak magnetic field measuring instrument that uses the nonlinear characteristics of periodic alternating magnetization saturation of soft magnetic materials,and it obeys Faraday's law of electromagnetic induction.Due to its characteristics of simple structure,small size,high sensitivity and good temperature stability,the application field is extremely extensive.Domestic research on fluxgate sensors is relatively lagging,and there is a big gap with foreign countries,and the core technologies of high-performance fluxgate sensors are in the hands of developed countries such as Europe and the United States.This thesis relies on the funding of the long-period distributed magnetotelluric observation system(No.2014AA06A612)of the 863 major project to carry out research on fluxgate sensors.In this paper,we study the related literatures on fluxgate sensor research at home and abroad,and finally choose the powerful and reliable finite element simulation software ANSYS to design the fluxgate sensor.Firstly,the working principle of the fluxgate sensor is analyzed,and the fluxgate sensor with double core structure is selected and designed.Based on the average magnetization curve of the core,the mathematical model of the fluxgate probe with half bridge square wave excitation is established,and the expressions of induction electromotive force and second harmonic sensitivity are derived.The rationality of the closed-loop structure of the fluxgate sensor based on the second harmonic method is analyzed.Then according to the target requirements of the subject,select the core material with suitable performance;analyze the design basis of the fluxgate probe,use ANSYS Maxwell software to establish the core model,excitation coil model and induction coil model,and the optimum parameters of each model are analyzed and determined.At the same time,the influence of the non-uniformity of the magnetic core material and the asymmetry of the excitation coil on the noise of the probe is explored.The importance of feedback coil design is analyzed,and the design method of spherical feedback coil with equal spacing and unequal turns is proposed.The accuracy of the method is verified by experiments.In the ANSYS Simplorer,the fluxgate circuit and the probe model were designed for co-simulation,and the performance of the simulation design fluxgate sensor was determined.Then,according to the parameters of simulation design,the prototype of fluxgate sensor is designed and manufactured,and the skeleton of each part of the probe is made by using 3D printer to complete the manufacture of the probe.The excitation circuit of the fluxgate sensor is designed with the quartz crystal as the frequency source,and the driving signal is generated by frequency division,phase shifting and power amplification,and the reference signal of the phase sensitive detection circuit of the same phase is generated by frequency division;The signal processing circuit of the prototype is designed,including LC resonance,phase-sensitive detection,low-pass filter,integrator and feedback circuit.The effect of phase-sensitive rectification on the final output is emphatically analyzed.Finally,a three-axis fluxgate sensor prototype was fabricated according to the parameters of the simulation design for performance test.The magnetic field measurement range of the three-axis of the prototype satisfies ±78000nT,the sensitivity of the three axes is close to 0.1mV/nT,the minimum noise of the three axes is less than 20 pT/?Hz@1Hz,and the frequency response of the three axes satisfies DC-10 Hz.The simulation results and the prototype measurement results were compared and analyzed,and the feasibility and accuracy of the simulation design were verified.