Research On Fluxgate Sensor With Multi-Magnetic Circuit And Parameters Optimization Of The Core Model

The precise measurement of the weak magnetic field,especially the geomagnetic field,plays an important role in the satellite attitude measurement and control,the autonomous navigation of submarine,earthquake prediction,medical equipment,mining location and so on.Among numerous kinds of vector magnetic field sensors,the fluxgate sensor has some advantages such as small size,light weight,high sensitivity and so on,so it has been widely used in practice.Fluxgate sensor is such an instrument that uses excitation magnetic field and external magnetic field to make the magnetic core saturate periodically to measure the magnetic field.The fluxgate sensor is mainly composed of a probe,an excitation circuit and a detection circuit.The main part of the fluxgate sensor is the probe,while the essential part of the probe is the magnetic core.So the accuracy of the magnetic core model is essential to precisely analyze and design fluxgate probe.The fluxgate probes with different core structures have different working mechanisms and applications.Different magnetic core structure and excitation mode should be designed to meet the special needs of magnetic measurement.In recent years,fluxgate sensor is development in the direction of high performance,miniaturization,and low power consumption and so on,which makes it has higher requirements in core structure,output signal detection and processing method in order to reduce the fluxgate sensor volume,complexity and power consumption,etc.In this paper,the key technologies such as the precise determination of the fluxgate magnetic core model parameters,the design of the magnetic core structure and the output signal processing of fluxgate probe are studied.The main contents are as follows.1.Precisely determine the parameters of the core model.Biogeography-based Optimization Algorithm and Fruit Fly Optimization Algorithm are applied to optimize the parameters of the Jiles-Atherton(J-A)model which is used to describe the hysteresis characteristics of the core.(1)To solve the disadvantages such as poor searching ability and prone to premature of Biogeography-based Optimization Algorithm,Arnold mapping is used to generate the initial population and differential mutation strategy is introduced to improve the performance of the transport equation.The simulation results are compared with those of Genetic Algorithm,Particle Swarm Algorithm,Differential Evolution Algorithm and Biogeography-based Optimization Algorithm.(2)Fruit Fly Optimization Algorithm is easy to fall into the local extremum and has low precision and stability,so the dynamic variable step size is used to generate the moving direction of the fruit fly to improve the algorithm performance.The simulation results are compared with those of Particle Swarm Algorithm and Fruit Fly Optimization Algorithm.2.Design fluxgate probe with new magnetic core structure and perform simulation research.(1)Aiming at the measurement of magnetic field in narrow slit and micro space,design fluxgate probe with ?-shaped core and study the working mechanism.Apply the Finite Element Analysis software AN SYS to carry out the simulation experiments to verify the correctness of the working mechanism.(2)Aiming at the measurement of point magnetic field in narrow slit and micro space,design fluxgate probe with ?-shaped core.Analyze the excitation mode and working mechanism of fluxgate probe with ?-shaped core in theoretical,and verify the rationality and correctness of fluxgate probe with ?-shaped core by simulations performed in ANSYS environment.3.Manufacture the fluxgate probes with novel structure and make experimental tests.(1)The fluxgate probe with ?-shaped core is made by using permalloy strip as the core material.Experiments are carried out to test the output of the probe under sine wave excitation and square wave excitation.(2)The fluxgate probe with ??shaped core is fabricated by using permalloy film as the core material.The outputs under sine wave excitation and square wave excitation are measured by center excitation mode.4.Study the performance of the same size probes with ?-shaped core and ??shaped core.(1)Manufacture fluxgate probe with ?-shaped core which has the same size as fluxgate probe with ?-shaped core.(2)Make tests on the output signals of the two fluxgate probes under two excitation modes(opposite-side excitation mode and four-side excitation mode),and analyze the output signals of the two fluxgate probes.5.Study on the processing method of output signal of fluxgate probe and point magnetic field measurement.(1)Use soft processing method to process output signal instead of conventional analog circuit processing;(2)Study the measurement method of plane point magnetic field.The research results show that:(1)Both Biogeography-Based Optimization Algorithm and Fruit Fly Optimization Algorithm can be used to optimize the parameters of J-A model accurately,which provides theoretical basis for the parameters determination of the core model;(2)Fluxgate probe with ?-shaped core can measure single direction magnetic field,fluxgate probe with ?-shaped core can measure magnetic field in both horizontal and vertical directions,and they can be used for a narrow slit magnetic field measurement occasion;(3)Outputs signal processing with soft processing method instead of conventional circuit processing,which solves the complexity problem of multi-magnetic circuit fluxgate,improves the effectiveness and flexibility of signal processing,and reduces power consumption.