ABSTRACT
This research was centered on optimizing the Fluxgate Magnetometer Sensor (FMS) at reduced noise level and enhanced sensitivity. The FMS was developed using Manganese Zinc(MnZn) ferrite alloy different from the usual permalloy and amorphous alloy materials.
The developed using MnZn ferrite achieved reduced dimensions with high sensitivity and reduced noise level, thus meeting the necessary requirements for the earth‟s magnetic field studies.
However, the sensor was realized using MnZn ferrite ring core material, excitation and pick-up coils, and the interface electronic circuits.
The performance of this designed and developed FMS was optimized using the modified Firefly OptimizationAlgorithm (FOA).
The characteristics of the developed sensors were modeled using the modified FOA and the matching between the excitation and detection was then considered.
Analysis was then carried out to determine the values of relevant parameters susing modified FOA written in the MATLAB program. The model yielded an accurate prediction of the sensitivity and noise level compared to the commonly used conventional Part-by-Part Optimization (PPO) and analytical optimization techniques.
Three-ring core FMS with different diameters (14 mm and 10 mm) were constructed based on the PPO technique while12 mm ring core was constructed based on the FOA technique. Experiments were employed to validate the PPO and the FOA techniques.
TABLE OF CONTENTS
TITLE PAGE…………………………………………………………………………………………………………… ii
DECLARATION…………………………………………………………………………….iii
CERTIFICATION …………………………………………………………………………………………………… iv
DEDICATION…………………………………………………………………………………………………………. v
ACKNOWLEDGEMENTS………………………………………………………………………………………. vi
ABSTRACT…………………………………………………………………………………………………………..viii
TABLE OF CONTENTS………………………………………………………………………………………….. ix
LIST OF FIGURES ………………………………………………………………………………………………..xiii
LIST OF PLATES ………………………………………………………………………………………………….. xv
LIST OF TABLES…………………………………………………………………………………………………. xvi
LIST OF ABBREVIATIONS…………………………………………………………………………………xviii
CHAPTER ONE: INTRODUCTION
1.1 Background…………………………………………………………………………………………………… 1
1.2 Motivation…………………………………………………………………………………………………….. 5
1.3 Problem Statement…………………………………………………………………………………………. 5
1.4 Significant Contributions of the Research …………………………………………………………. 6
1.5 Research Aim and Objectives………………………………………………………………………….. 7
1.6 Methodology…………………………………………………………………………………………………. 8
1.7 Organization of the Thesis………………………………………………………………………………. 9
CHAPTER TWO: LITERATURE REVIEW
2.1 Introduction………………………………………… ………………………………10
2.2 Review of Fundamental Concepts………………… …. …………………….……….10
2.2.1 Overview of Earth‟s Magnetic Field and Magnetic Storm……….. ………………..10
2.2.2 Overview of Fluxgate Magnetometers………………………… ……………………….12
2.2.3 Principle of Operation of Fluxgate Magnetometers…………… ………………………16
2.2.4 Classification of Magnetic Sensors and their Technologies………… ………………20
2.2.5 Fluxgate Sensor Electronics……………………………………………. ……………….24
2.2.5.1Square Wave Current Generator………………………………………. ……………….25
2.2.5.2 Frequency Divider………………………… ……………………………… ……………….27
2.2.5.3 Voltage to Current Converter………………………………………….. ……………….28
2.2.5.4 Detection Electronics…………………………………………………….. ……………….30
2.2.5.5 Synchronization Switch………………………… ………………………. ……………….32
2.2.5.6 Ferro-resonance Excitation Drive and Parametric Amplification…… ……………….. .34
2.2.6 Fluxgate Magnetometer Core Materials……………….…………… ………………….. 35
2.2.7 Magnetization Behavior of Ferromagnetic Materials…………………………………… 36
2.2.8 Soft and Hard Magnetic Materials………………………………………………………… 38
2.2.9 Demagnetization of Magnetic Material……… ………………………………………………… 40
2.2.10 Ferrite Core Material………………………………………………………………………………. 41
2.2.11 Helmholtz Coils…………… …………………………………………………………………………. 42
2.2.12 Overview of Optimization …………………………………………………………………………….. 44
2.2.12.1Multi-Objective Optimization…………………………………………………………………….. 47
2.2.13 Part-by-Part Optimization of Fluxgate Magnetometers…………………………………. 49
2.3 Review of Similar Works……………………………………………………………………. 49
2.4 Summary………………………………………………………………………………………. 58
CHAPTER THREE: MATERIALS AND METHODS
3.1 Introduction…..……………………………….. …………………………………………60
3.2 Materials…..…………… ……………………….. ……………………………………….60
3.2.1 types of equipment used…………………………………. ……………………………………….60
3.3 Method…..………………………………………. ………………………………………62
3.3.1 Fluxgate Magnetometer Drive Electronics Development and Simulations.. ……….63
3.3.1.1 Square Wave Generator Circuit…………………. …………………………………….64
3.3.1.2 Frequency Divider circuit…… ……………………. …………………………………….65
3.3.1.3 Voltage to Current Amplifier Circuit………….. …………………………………….65
3.3.2 Fluxgate Magnetometer Sense Electronics………………………………………….67
3.3.2.1 Synchronization Switch Circuit…………………. …………………………………….67
3.3.2.2 Pick-up Coil Output Voltage Amplification Circuit. ……………………………….69
3.3.2.3 Low Pass Filter…… ………………………………….. …………………………………….70
3.3.3 Analog to Digital Conversion of Fluxgate Sensor Output Signal….. ……………….71
3.3.4 Power Supply………………………………………….. …………………………………….73
3.3.5 Fluxgate Magnetometer Sensor…… ……………. …………………………………….73
3.3.6 Magnetic Field Model of Fluxgate Magnetometer………………………………….78
3.3.6.1 Finite Element Method…… ……………………….. …………………………………….78
3.3.6.2 ANSYS Program Structure………………………………………………………………….. .79
3.3.7 Fluxgate Sensor Design………………………… ……………………………………………. .86
3.3.7.1 Part-by-Part Optimization Design of Fluxgate Magnetometer……………………. ..…..86
3.3.7.2 FOA Design of Fluxgate Magnetometer and Helmholtz Coils…… ……………… .…..93
3.3.8 Fluxgate Sensor Fabrication…… …………………………………………………………….. .…..99
3.3.9 Helmholtz Coilsconstruction…… ……………… …………………………………….100
3.4 Summary……………………………………………………………………………………. ….103
CHAPTER FOUR: RESULTS AND DISCUSSIONS
4.1 Introduction….…………………………………………….. ……………………………104
4.2 FEA Simulation Results………………………………………………………………………. .…..104
4.3 Fluxgate Sensor Optimization Results…………………………………………………… .…..107
4.4 Helmholtz Coils Optimization Results…… …………………………………………….. .…..113
4.5 Performance of Fluxgate Sensors Based on Objective Three…………….. …..……116
4.5.1 Performance Responses of the Fluxgate Excitation Electronic Circuit…… ..……..116
4.5.1.1 Details of Electronic Testing Board and Experimental Set-up…… ……………….116
4.5.1.2 Time-Dependent Response……………………………… ………………………. ……..119
4.5.1.3 Response of Pick-up Coil without Detection Circuit………………………………. ……122
4.5.1.4 Responses of the Sensors Pick-up Coils with Detection Circuit……… ……… ……125
4.5.2 Sensing the Magnitude and Direction of Earth‟s Magnetic Field……………. ……..131
4.6 Performance of the Optimized FMS Based on Objective Four…………………….. ..140
4.7 Summary……..……………………………………………………………………………. 145
CHAPTER FIVE: CONCLUSION AND RECOMMENDATIONS
5.1 Conclusions………………………………………….. ……………………………………146
5.2 Limitations of the Research …………………………………………………………………………. 147
5.3 Recommendations for Further Works……………………………………………… ………148
REFERENCES…………………………… ……………………………………………………….. ……149
APPENDICES………………………………………….. ………………………………. ………………158
INTRODUCTION
Background
There have been increasing demands for the integration of a magnetic field sensor that can detect the magnitude and direction of the earth‟s magnetic field in complex electronic systems (Lv and Liu, 2014).
Such a magnetic field sensing system will find application in low-power mobile devices such as in terrestrial and space navigation systems including military detection, craft navigation, medical recognition, modern digital navigation, and nondestructive inspection (David et al., 2010; Hsieh et al., 2013).
The aim of this research is to design and develop an optimized Fluxgate Magnetometer Sensor (FMS), which has a small size, high sensitivity, low noise, low power consumption, and is capable of detecting the magnitude and direction of the earth‟s magnetic field.
In order to optimize the performance of magnetometers, different optimization techniques for their structures and core materials had been developed.
For example, the conventional approach was based on Part-by-Part Optimization (PPO) technique, which includes designing the sensor core first, then select the dimension of the pick-up coil, and finally develop a low-noise detection circuit.
However, the PPO technique is too slow, time-consuming, and expensive(Grosz and Paperno, 2012)
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