analysis and optimal design of brushless dc micromotor

I

AIN SHAMS UNIVERSITY

FACULTY OF ENGINEERING

Electrical Power and Machines Engineering

Analysis and Optimal Design

of Brushless DC Micromotor

A Thesis submitted in partial fulfilment of the requirements of the degree of

Doctor of Philosophy In Electrical Engineering

(Electrical Power and Machines Engineering)

By

Ahmed Sayed Abd-Rabou Mohammed

Master of Science In Electrical Engineering


Faculty of Engineering, Ain shams University, 2011

Supervised By

Prof. Ahmed Abdel Sattar Abdel Fattah

Prof. Mostafa Ibrahim Marei

Assoc. Prof. Mohamed Ali Basha

Cairo - (2019)

II



Electrical Power and Machines



by




Faculty of Engineering, Ain Shams University, 2011

Examiners’ Committee

Name and Affiliation Signature

Prof. Hassan Elsayed Ahmed Ibrahim

Electrical and Control Engineering, Arab Academy for

Science Technology & Maritime Transport

……………….

Prof. Hamdy Saleh Khalil Elgoharey

Electrical Power and Machines , Ain shams University

……………….


Electrical Power and Machines , Ain shams University ……………….


Electrical Power and Machines, Ain shams University ……………….

Date:04 December 2019

III



Electrical Power and Machines



by




Faculty of Engineering, Ain Shams University, 2011

Supervisors’ Committee

Name and Affiliation Signature



……………….



……………….

Assoc. Prof. Mohamed Ali Basha

Electrical and Computer, Waterloo University

……………….


IV

Statement

This thesis is submitted as a partial fulfilment of Doctor of Philosophy in

Electrical Engineering, Faculty of Engineering, Ain shams University.

The author carried out the work included in this thesis, and none of its parts has

been submitted for a degree or a qualification at any other scientific entity.


Signature

…………...……….


V

Researcher Data

Name : Ahmed Sayed Abd-Rabou Mohammed

Date of birth : 27/4/1983

Place of birth : Cairo, Egypt

Last academic degree : Master of Science

Field of specialization : Electrical Power and Machines Engineering

University issued the degree : Ain Shams University

Date of issued degree : 2011

Current job : Nanotechnology Senior Engineer

Zewail City of Science and Technology

VI

Thesis Abstract

This thesis presents a novel analysis and design of axial flux brushless DC

micromotor for implantable drug delivery applications for chemotherapy of

liver cancer. In order to design the micromotor, an analytical model has been

formulated. The 3D finite elements simulation has been used to validate the

analytical model accuracy as well as the experimental results of a previous

work, before using it to find the optimal design. The variations of the

geometrical dimensions, electrical parameters, and their effects on the output

torque and back EMF have been also examined. Finite element computations

have been used for numerical experiments on geometrical design variables in

order to evaluate the coefficients of a second-order empirical model for the

response surface representation. Mono-objective and multi-objective

optimization problems are introduced. The Bat Algorithm (BA) is used to solve

the mono-objective optimization process to minimize the motor volume and

improve joules efficiency in separate optimization problems with the constraints

of maximum required torque and maximum back EMF. The optimization results

were compared with other metaheuristic algorithms, including Genetic

Algorithms (GA), and Particle Swarm Optimization (PSO). The bat algorithm

results show an improvement over GA and PSO results. Moreover, multi-

objective design optimization technique using Multi-Objective Multi-Verse

optimization algorithm (MOMVO) is introduced. The two objectives of the

optimization process are to minimize the micromotor volume and improve

Joules efficiency with the constraints of maximum required torque and

maximum required back EMF. The optimization results were compared with

efficient multi-objective algorithm, the Non-Dominated Sorting Genetic

Algorithm Version II (NSGA-II). The MOMVO algorithm results show an

improvement over NSGA-II results. Prototypes of large scale PCB motor is

designed and manufactured to verify the analytical model and simulation of

micromotor.

Key words: Axial flux brushless DC micromotor, bat algorithm (BA), Multi-

Objective Multi-Verse optimization algorithm, implantable drug delivery

applications.

VII

Acknowledgment

The author would like to express his sincerest gratitude to Prof. Dr. Ahmed A.

El-Sattar, Prof. Dr. Mostafa I. Marei and Assoc. Prof. Dr. Mohamed Ali Basha

for their great support, excellent supervision and encouragement during the

period of this study. Deep thanks to the soul of Prof. Dr. Mohamed Abdel-Latif

Badr, as he gave me a great support during his supervision of this study. Sadly,

he had passed away before I accomplished this work .

Special thanks to Dr. Mohamed Ali Basha, as I am considering him my big

brother, he not only supported me in my study, but he also encouraged and

helped me in several hard situations that I had faced.

I would like to thank my friend Tamer Abd-Elsalam, as he always encourages

and supports me. I would like to thank my friend and my colleague in Zewail

City of Science and Technology Karim Mohamed for his great support and

encouragement .

I would like to thank my wife Maha for her great support, understanding and

love during my studying journey. Thanks to my son Omar for the great love,

that he gives me. I dedicated this thesis to the soul of my mother, I wish her

heaven. I would like to acknowledge with gratitude, my father, my sister Hoda

and my brother Mohammed for the great love and encouragement.

Finally, special thanks to my friend Wael Shehata for his great support and

encouragement.

December 2019

VIII

Table of Contents

Thesis Abstract VI Acknowledgment VII Table of Contents VIII List of figures XI List of tables XVII List of Abbreviations XIX List of symbols XX

Chapter 1: INTRODUCTION

1.1 General 1

1.2 Brushless DC Motor an Overview 2

1.3 Brushless DC Motor Principle of Operation 6

1.4 Brushless DC Motor Control Circuit 9

1.5 Sensorless BLDC Motor Control 9

1.6 Torque/Speed Characteristics 11

1.7 Types of BLDC Motor 12

1.8 Axial Flux BLDC Motor Configurations 15

1.8.1 Axial Flux BLDC Machines Stator

Windings

15

1.8.2 Axial Flux BLDC Machines Rotor 16

1.8.3 Axial Flux BLDC Machines without

Stator Cores

17

1.9 Power MEMS 19

1.9.1 Micromotors 21

1.10 Literature Review 21

1.10.1 Electrostatic Micromotors 22

1.10.2 The Electrical Induction Micromotors 23

1.10.3 Variable Reluctance Magnetic

Micromotors

25

1.10.4 Axial Flux BLDC micromotor 27

1.11 Application of Axial Flux BLDC micromotor 32

1.11.1 Medical Applications 32

1.11.2 Hand watches Application 36

1.12 Thesis Objectives and layout 37

IX

Chapter 2: DESIGN AND MODELING

ANALYSIS OF AFPM BLDC

MICROMOTOR

2.1 Introduction 40

2.2 Analytical model 42

2.2.1 Sizing equation 42

2.2.2 Air Gap Flux Density 45 2.2.3 Electromagnetic Torque and Back EMF 46

2.2.4 The Phase Resistance, Joule and Eddy

Current Losses

48

2.3 Verification of analytical model and 3D FE

Analysis using previous work micromotor

53

2.4 Design steps of micromotor initial model 56

2.5 Initial model of Micromotor basic structure and

specification

61

2.6 3D Finite Elements Analysis 63

2.7 Micromotor parametric study 68

2.7.1 Air Gap length δ 69

2.7.2 Stator Outer Diameter Dout 72

2.7.3 Permanent Magnet Outer and Inner Radii

RPMout, RPMin

75

2.7.4 Permanent Magnet Thickness hm 77

2.7.5 Number of Layers 80

2.7.6 Coil Shape 81

2.8 Selection of design parameters for optimization

study

85

Chapter 3: DESIGN OPTIMIZATION OF

AFPM BLDC MICROMOTOR

3.1 Introduction 88

3.2 Micromotor Model And FEA Simulation 89

3.3 Response Surface Methodology (RSM) 90

3.3.1 Constructing of Empirical Model 91

3.4 Bat Algorithm (BA) 94

3.4.1 Bat Algorithm Optimization Results 97

3.4.2 Comparison with Other Algorithms 101

3.5 Multi-Objective Multi-Verse Optimization

Algorithm (MOMVO)

104

X

3.5.1 Multi-Verse Optimizer 104

3.5.2 Mechanism of Multi-Objective Multi-

Verse Optimizer

108

3.5.3 MOMVO Optimization Results 109

Chapter 4: EXPERIMENTAL OF

PROTOTYPE PCB MOTOR

4.1 Introduction 114

4.2 Design of PCB Motor 115

4.3 Basic Structure Of PCB Motor 117

4.4 PCB Motor Parts And Assembly 120

4.4.1 PCB Stator 120

4.4.2 Rotor Assembly 121

4.4.3 Complete PCB Motor Assembly 122

4.5 Driving Circuit 123

4.5.1 General Functional Description of

Sensorless BLDC Motor Driver

124

4.6 Experimental measurements 126

4.6.1 Measuring OF Back EMF 127

4.6.2 Measuring OF PCB Motor Input Voltage 132

4.6.3 Measuring OF PCB Motor Output Torque 134

4.7 Mathematical Model Verification 135

4.8 Verification Of 3-D Finite Element Analyses

Simulation

136

4.8.1 3D-FEA Magneto-Static Simulation 137

4.8.2 3D-FEA Transient (Dynamics)

Simulation

138

4.9 Comparison Between Mathematical Model, 3D

(FEA) Simulation And Measurement Results

141

4.10 Data sheet of PCB motor Prototype 142

Chapter 5: CONCLUSION 144

REFERENCES 148

APPENDIX A 158

PUBLICATIONS 178

XI

List of Figures

1.1 Structure of brushless DC motor 4

1.2.a Brushless DC motor different configurations,

Inner rotor

5

1.2.b Brushless DC motor different configurations,

Outer rotor type

5

1.3 Commutation Sequence of three-Phase BLDC

Motor

6

1.4 Timing diagrams of the three-phase BLDC motor

Hall sensors

8

1.5 Brushless DC Motor Control Circuit 9

1.6 Sensorless BLDC motor control block diagram 10

1.7 Hall sensor versus back EMF 11

1.8 BLDC motor torque/speed characteristics 12

1.9.a Types of BLDC motor, Radial flux BLDC motor 13

1.9.b Types of BLDC motor, Axial flux BLDC motor 13

1.10 Coreless winding of a three-phase, eight-pole

axial flux BLDC machine with twin external

rotor

16

1.11 AFPM BLDC machine PM rotors shapes 17

1.12 Axial flux PM brushless motor with film coil

ironless stator winding

18

1.13 Exploded view of PCB ironless axial flux PM

brushless motor

19

XII

1.14 Microengine silicon components in Professor

Alan Epstein hand

20

1.15 An electrostatic micromotor 22

1.16 Electrostatic micromotor with assembled

micromirror for optical MEMS switch application

23

1.17 Electrical induction micromotors 24

1.18.a A variable-reluctance magnetic micromotor,

Motor structure

25

1.18.b A variable-reluctance magnetic micromotor,

Meander-type inductor

25

1.19 Penny-motor 27

1.20 Penny-motor components 28

1.21 PM micromotor four layer winding. Courtesy of

TU Berlin, Germany

29

1.22.a Micromotor with etched winding, construction 30

1.22.b Micromotor with etched winding, etched

windings layout

30

1.23 Structure of the axial flux BLDC micromotor 31

1.24.a Structure of the axial flux BLDC micromotor,

Stator

31

1.24.b Structure of the axial flux BLDC micromotor,

Rotor permanent magnet

31

1.25 DuraHeart pump exploded view 33

1.26.a Implantable insulin pump. Pump inside body 34

1.26.b Implantable insulin pump, Pump system 34

1.27 Implantable chemotherapy pump for liver cancer 35

XIII

treatment

1.28 Axial flux BLDC micromotor for driving hand

watch

36

2.1 Trapezoidal coil layout 50

2.2 Exploded view and dimensions of previous work

micromotor

53

2.3 Mesh density of previous work micromotor

model

54

2.4 Flux density distribution previous work

micromotor model (isometric view)

55

2.5 Flux density distribution previous work

micromotor model (side view).

55

2.6 Design Steps of micromotor initial model 58

2.7 Exploded view of the proposed micromotor 62

2.8.a Flux density distribution from 3D FEA, Isometric

view

65

2.8.b Flux density distribution from 3D FEA, Axial

view

65

2.9 Comparison between the calculations of the air

gap flux density using mathematical model and

the 3D (FEA) simulation

66

2.10 Back EMF calculation using 3D (FEA)

simulation

67

2.11 Flux linkage calculation using 3D (FEA)

simulation

67

2.12 The air gap maximum flux density for deferent

air gap length

70

XIV

2.13 The average electromagnetic torque for deferent

air gap length

70

2.14 The back EMF for deferent air gap length 71

2.15 Dependence of average electromagnetic torque

on stator outer

72

2.16 Dependence of back EMF on stator outer

diameter

73

2.17 Micromotor geometery for different permanent

magnet outer and inner radii.

76

2.18 The air gap flux density calculation using 3D

(FEA) simulation for different Permanent Magnet

Outer and Inner Radii.

77

2.19 The air gap flux density in the axial direction (z-

axis) for different permanent magnet thickness

78


on the permanent magnet thickness

79


on the ratio (total axial motor high/motor outer

diameter).

79

2.22 Dependence of back EMF on the permanent

magnet thickness

80

2.23 Exploded view of micromotor with rhomboidal

coil

81

2.24 Force analysis of micromotor with rhomboidal

coil

82

2.25 Rhomboidal coil layout 84

2.26 Selected design range for PM thickness 85

XV

2.27 Selected design range for air gap length 86

2.28 Selected design range for stator outer diameter 86

3.1 Exploded view of the proposed motor and

dimension design variables

90

3.2 Flow chart of total design process using BA

optimization

98

3.3 Volume at each iteration 99

3.4 Efficiency at each iteration 101

3.5 Flow chart of MVO algorithm 107

3.6 Flow chart of optimization process using

MOMVO

109

3.7 MOMVO Pareto front 111

3.8 Comparison between Pareto front of MOMVO

and NSGA-II algorithms

112

4.1 Exploded view of PCB motor basic structure 117

4.2 Cross section view of PCB motor with main

dimensions

118

4.3 PCB motor layout 119

4.4 PCB motor manufacturing and assembly steps 120

4.5 PCB stator 121

4.6 Rotor assembly. 121

4.7 M340 B-H curve 122

4.8 Complete assembly of PCB motor 123

4.9 PCB motor driving circuit. 124

analysis and optimal design of brushless dc micromotor

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