by nor hidayati diyana binti nordin a thesis submitted in

INVESTIGATION OF ENERGY EFFICIENT

MAGNETORHEOLOGICAL FLUID (MRF) DAMPER

FOR APPLICATION IN PROSTHETIC LIMB

BY

NOR HIDAYATI DIYANA BINTI NORDIN

A thesis submitted in fulfillment of the requirement for

the degree of Doctor of Philosophy (Engineering)

Kulliyyah of Engineering

International Islamic University Malaysia

MAY 2018

ii

ABSTRACT

The use of dampers as shock absorbers in both transfemoral and transtibial prosthesis is

important in order to provide comfort to the amputees without jeopardizing their health

and safety. Three types of dampers are available namely active, semi-active and passive

dampers. However, passive dampers are not suitable since the impedance data cannot be

tuned and for active devices, they are not in favour due to its size and cost. In order to

provide damping to the prosthesis that can be automatically tuned for normal walking

conditions, magnetorheological fluid (MRF) damper can be used. MRF damper is a

damper filled with magnetorheological fluid that reacts to the presence of magnetic field.

It contains microsized particles, usually carbonyl iron particles which will align

themselves forming chain-like structures parallel to the applied magnetic field. Thus, the

rheology of the fluid is rapidly altered. The strength and distributions of the magnetic

field influence the rigidity of the material, which directly affects the magnitude of force

delivered by the damper. MRF damper needs an electromagnetic system to achieve

“ON” state. Wearing a prosthetic limb that requires large power source accounts for

inconveniency. Hence, to address this issue, there is a need for an energy efficient MRF

damper that requires low power consumption so as to prolong its battery life. In this

research, two areas were covered which are optimizing the energy efficient MRF damper

as well as designing a suitable controller for an ankle prosthesis. In optimizing the

dynamic range, this study will tackle the issue through MRF particles size and volume

percentage ratio. COMSOL Multiphysics software was used in the optimization study

and experiments were also conducted to verify the findings. It is shown that smallest

particle size and highest particle ratio, which is 2μm at 0.6 particle ratio exhibits the

highest wall shear stress, at a lesser amount of applied current. In addition, simulation

works using fuzzy-PID (F-PID) controller was also developed to ensure the performance

of the prosthetic limb equipped with MRF damper, which completed the research work

from the perspective of mechatronics engineering. Using PID controller, the error goes

up to 90% while a maximum of 20% percentage error is seen for a prosthetic limb with

F-PID.

.

iii

خلاصة البحث

ظنبوبية -فخذية و العبر-استخدام مثبطات الصدمات لامتصاص الصدمات في الأطراف الاصطناعية العبر ;المساس بصحتهم وسلامتهم. هناك ثلاثة أنواع من المثبطاتمهم لتوفير الراحة لمبتوري الأطراف دون

مثبطات نشطة، وشبه نشطة، وغير نشطة. المثبطات الغير نشطة غير ملائمة لأن بيانات الممانعة لا يمكن ضبطها، أما المثبطات النشطة فهي ليست مرغوبة بسبب حجمها وتكلفتها. من أجل توفير تثبيط إلى

ط التلقائي لظروف المشي العادية فإنه بالامكان استخدام مثبطات السائل طرف اصطناعي قابل للضبهو مثبط معبأ بسائل مغنطيسي يتفاعل مع وجود مجال MRF. مثبط (MRF)المغنطيسي الريولوجي

مغناطيسي. يحتوي هذا المثبط على جسيمات متناهية الصغر، وعادة ما تكون مصنوعة من حديد الكربونيل ا بتكوين هياكل شبه سلسلية متوازية مع المجال المغناطيسي المطبق، وبالتالي فإن انسيابية التي تشكل نفسه

السائل في تغير سريع. تؤثر قوة وتوزع المجال المغناطيسي على صلابة المادة، والتي تؤثر بشكل مباشر على يق حالة التشغيل إلى نظام كهرومغناطيسي لتحق MRFكمية القوة الموضوعة على المثبط. يحتاج مثبط

"ON لبس طرف اصطناعي يتطلب مصدر طاقة كبيرة والذي بكونه غير ملائم. لمعالجة هذه المشكلة ."موفر للطاقة والذي يحتاج فقط إلى طاقة منخفضة لإطالة عمر البطارية. MRFهناك حاجة إلى مثبط

، بالإضافة MRFاقة مثبط الـفي هذا البحث ، تم تغطية مجالاين وهما العمل على تحسين كفاءة مولد طإلى تصميم وحدة تحكم مناسبة لعزل الكاحل. من أجل تحسين النطاق الديناميكي ستعالج هذه الدراسة

وفرق النسبة المئوية للحجم. تم استخدام برنامج MRFالمشكلة من خلال حجم جزيئات الــCOMSOL Multiphysics من النتائج. تبين أن في دراسة التحسين وتم إجراء تجارب للتحقق

نسبة جسيمية، أظهرت 0.6مكرومتر عند 2أصغر حجم جسيمي وأعلى نسبة للجسيمات والتي بلغت أعلى إجهاد على الجدار، وذلك على أقل كمية للتيار المطبق. بالإضافة إلى ذلك تم تطوير أعمال المحاكاة

صطناعي المجهز بمثبط لضمان أداء الطرف الا fuzzy-PID (F-PID)باستخدام وحدة تحكم MRF والذي أكمل العمل البحثي من منظور الهندسة الميكاترونيكية. باستخدام وحدة تحكم ،PID

.F-PID٪ بحد أقصى للخطأ في الأطراف الصناعية المجهزة بــ20٪ مقارنة بنسبة 90ارتفع الخطأ إلى

iv

APPROVAL PAGE

This thesis of Nor Hidayati Diyana binti Nordin has been approved by the following:

______________________

Asan Gani Abdul Muthalif

Supervisor

______________________

Tanveer Saleh

Co-Supervisor

______________________

Norsinnira Zainul Azlan

Co-Supervisor

______________________

Muhammad Mahbubur Rashid

Internal Examiner

______________________

Rahizar Ramli

External Examiner

______________________

Jawaid Iqbal Inayat Hussain

External Examiner

______________________

Akram M Z M Khedher

Chairman

v

DECLARATION

I hereby declare that this thesis is the result of my own investigations, except where

otherwise stated. I also declare that it has not been previously or concurrently submitted

as a whole for any other degrees at IIUM or other institutions.

Nor Hidayati Diyana binti Nordin

Signature …………………………………… Date ……………………..

vi

INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA

DECLARATION OF COPYRIGHT AND AFFIRMATION OF

FAIR USE OF UNPUBLISHED RESEARCH

INVESTIGATION OF ENERGY EFFICIENT

MAGNETORHEOLOGICAL FLUID (MRF) DAMPER

FOR APPLICATION IN PROSTHETIC LIMB

I declare that the copyright holder of this thesis are jointly owned by the student

and IIUM.

Copyright © 2018 Nor Hidayati Diyana binti Nordin and International Islamic University Malaysia.

All rights reserved.

No part of this unpublished research may be reproduced, stored in a retrieval system,

or transmitted, in any form or by any means, electronic, mechanical, photocopying,

recording or otherwise without prior written permission of the copyright holder

except as provided below.

1. Any material contained in or derived from this unpublished research may only

be used by others in their writing with due acknowledgement.

2. IIUM or its library will have the right to make and transmit copies (print or

electronic) for institutional and academic purposes.

3. The IIUM library will have the right to make, store in a retrieval system and

supply copies of this unpublished research if requested by other universities

and research libraries.

By signing this form, I acknowledge that I have read and understand the IIUM

Intellectual Property Right and Commercialization policy.

Affirmed by Nor Hidayati Diyana binti Nordin

……………………………………. ……………………..

Signature Date

vii

This thesis is dedicated to my husband, Mohd Shafiq, children, Hanaa Nuralisha &

Ilman Hafiy and parents, Nordin and Rohani…

viii

ACKNOWLEDGEMENT

Alhamdulillah, prayers to Allah s.w.t for giving me the courage, strength and health to

complete this thesis as part of my PhD journey. My thanks go to all those people who

have assisted and guided me.

I would first like to acknowledge my main supervisor, Assoc. Prof. Ir. Dr. Asan

Gani Abdul Muthalif for his patience, guidance and encouragement throughout my

academic years in IIUM, without which this thesis would not be possible. I would also

like to thank my co-supervisors, Assoc. Prof. Dr Tanveer Saleh and Dr Norsinnira

Zainul Azlan for their assistance.

I am thankful to my husband, Mohd Shafiq Suhaimi for his understanding and

endless support to me throughout the journey and my beautiful children, Hanaa

Nuralisha and Ilman Hafiy for being my strength and motivation. Not to forget, I would

like to express my gratitude to my family, especially my parents, Nordin Hj Ahmad,

and Rohani Embong, for always be there every time I need their help as well as my

brothers for their support.

I would also like to thank my friends in Smart Structures, Systems and Control

Research (S3CR) Laboratory, especially Sr. Azni Nabela Wahid, Sr. Farahiyah Jasni

and Br Khairul Affendy for being part of the journey. My appreciation is also extended

to Br. Shahlan Dalil from Mechatronics Workshop, Br. Shaiful from Engineering

Workshop and Br. Farid from General Structure Lab for their cooperation and ideas

during the machining works and experiments. Finally, to MySMARTLeg team from

University Malaya, thank you for the exposure and knowledge sharing.

Thank you!

ix

TABLE OF CONTENTS

Abstract ………………………………………………………………………... ii

Abstract in Arabic ……………………………………………………...…........ iii

Approval Page ………………………………………………………...……...... iv

Declaration …………………………………………………………………...... v

Copyright ………………………………………………………..……………... vi

Dedication ………….………………………………………………..………… vii

Acknowledgement ……………………………………………………...…........ viii

List of Tables ………………………………………………………………..…. xii

List of Figures ……………………………………………………………….… xiv

List of Symbols ………………………………………………………………... xx

CHAPTER 1: INTRODUCTION ……………….…………………………... 1

1.1 Overview ……………………………………………………...……….…... 1

1.2 Semi active prosthetic limb ………………………………………………… 4

1.2.1 Magnetorheological fluid (MRF) damper…...…………………...... 5

1.3 Motivation of the study……………………………………………….…..… 10

1.4 Problem statement ……………………………………………………….…. 11

1.5 Research objective ……………………………………………………..…… 12

1.6 Research methodology…………………………………………………....… 12

1.6.1 Phase 1: Optimization of MRF for energy efficient MRF damper.. 13

1.6.1 Phase 2: Controller design 13

1.7 Contribution of the work……………………………………………...…...… 15

1.8 Scope of research……………………………………………….………...…. 15

1.9 Organization of thesis……………………………………………………...... 16

CHAPTER 2: LITERATURE REVIEW……………………………..……... 17

2.1 Mechanism of shock attenuation during walking via human lower limb …. 18

2.2 Shock absorption in prosthetic limb ……………………………………….. 20

2.2.1 Passive prosthetic limb ………………………………………….. 20

2.2.2 Active prosthetic limb ……………………………………………. 21

2.2.3 Semi active prosthetic limb ……………………………..……….. 23

2.3 Optimization of magnetorheological fluid damper …….………………….. 24

2.3.1 Damper design …………………………………………………… 25

2.3.2 Magnetorheological fluid particle …………………………..…... 27

2.3.2.1 Sedimentation rate…………………………………………. 27

2.3.2.2 Damping force……………………………………………... 28

2.4 Control strategies for magnetorheological fluid (MRF) damper..…………. 29

2.5 Control strategies for prosthetic limb …………………………………….. 30

2.5.1 PID controller …………………………….….………….….…... 32

2.5.2 Fuzzy-PID controller ……………………………………….…… 34

2.5.2.1 Fuzzy logic controller ……………………………………… 34

2.5.2.2 Fuzzy-PID controller ………………………………………. 35

2.6 Summary ………………………………………………………………….. 36

x

CHAPTER 3: PARAMETRIC INVESTIGATION ……………..………..... 37

3.1 Simulation studies ……………………………………………..…………... 37

3.1.1 Boundary Conditions ………………………………..…………... 39

3.1.2 B-H Curve …………………………………………..………….... 40

3.1.3 Dipole-Dipole Interactions ………………………...…………..... 42

3.1.4 Shear Stress Analysis …………..………………………………... 43

3.2 The effect of particle ratio, ϕ and particle size, d on shear stress, τ ( during

ON state) ………………………………………...…………………………….

45

3.2.1 The Effect of Particle Size, d and Particle Ratio, ϕ on Shear

Stress, τ at a Fixed Number of Magnetic Particles …………………….

45

3.2.2 The Effect of Particle Size, d and Particle Ratio, ϕ on Shear

Stress, τ at Different Number of Magnetic Particles …………………..

48

3.3 The effect of polydispersed particles in magnetorheological fluid ………... 56

3.4 Optimal value of particle ratio and particle size for energy efficient

magnetorheological fluid damper for prosthetic limb ………………………….

59

3.5 Summary ..…………………………………………………………………. 63

CHAPTER 4: EXPERIMENTAL WORK ………..……………………....... 65

4.1 Magnetorheological fluid (MRF) damper …………………………………. 65

4.1.1 Design of MRF damper ………………………………………...… 65

4.1.2 Measurement of magnetic field ………………………………...… 68

4.1.3 Magnetorheological fluid ………………...……………………... 72

4.2 Experimental setup ……………………………………………………...… 74

4.3 Optimal magnetorheological fluid for MRF damper in prosthetic limb …….. 83

4.4 Summary …………………………………………………………………… 85

CHAPTER 5: THE BIOMECHANICS OF HUMAN WALKING …….…. 86

5.1 Human gait cycle ………………………………………………………..…. 86

5.2 Kinematics of human lower limb …………………………..… 88

5.3 Simulation studies using kinematic data …………………………………… 93

5.3.1 Ground reaction force ……………………………………………. 95

5.4 Shock absorber in gait ……………………………………………………… 96

5.5 Preliminary studies using commercial prosthetic foot ……………………… 96

5.6 Summary ………………………………………………………………...… 100

CHAPTER 6: TRANSTIBIAL PROSTHETIC LIMB WITH MRF

DAMPER ……………………………………………………………………...

101

6.1 MRF damper in transtibial prosthetic limb …………………………………. 101

6.2 controller design for mrf damper in prosthetic limb ………………………. 105

6.2.1 Simulation results before foot flat ………………………………. 107

6.2.1.1 Case 1: without impact at heel strike ………………..…… 107

6.2.1.2 Case 2: With impact at heel strike ………………………... 117

6.2.2 Simulation results after foot flat ……………………………......... 119

6.3 Summary ….……………………………………………………………….. 120

CHAPTER 7: CONCLUSION AND RECOMMENDATION …………… 121

7.1 Conclusion………………………………………………..……………….. 121

7.2 Limitations ……………………………………………..…………………... 122

7.3 Recommendations …………………………………….……………….…… 123

xi

REFERENCES ……………………………………………………………….. 125

LIST OF PUBLICATIONS & AWARD…………………………………….. 141

xii

LIST OF TABLES

Table 1.1 Three parts of prosthetic limbs

3

Table 1.2 Operational modes of MRF damper

7

Table 2.1 Advantages of disadvantages of SACH foot (Grimmer & Seyfarth,

2014; O’Toole & Finnieston, 2013; Staros, 1957; Stein & Flowers,

1987)

21

Table 2.2 K-Levels definition (American Academy of Orthothists &

Prosthetists, n.d.)

23

Table 2.3 General effects of PID parameters (Liu & Van der Spiegel, 2017)

33

Table 3.1 List of material properties used for the simulation

38

Table 3.2 List of parameters used for the simulation

39

Table 3.3 The effect of particle size, d on particle ratio, ϕ

46

Table 3.4 Magnetic field, H generated at different level of applied current,

Icoil

47

Table 3.5 The effect of particle size, d and particle ratio, ϕ on the total

number of particles

49

Table 3.6 Maximum shear stress, τ generated at different particle size, d

(from 2 μm to 12 μm) throughout the simulation studies; which

occurs at ϕ = 0.6

55

Table 3.7 Maximum shear stress, τ generated at different particle ratio, ϕ

(from 0.05 to 0.6) throughout the simulation studies; which

occurs at d = 2μm

56

Table 3.8 The corresponding particle ratio of each primary particle size for

both monodispersed and polydispersed particles

57

Table 3.9 Damping values at four perturbation timing instances during

stance phase

61

Table 4.1 Dimension of the MRF damper used

68

Table 4.2 Amount of magnetic flux density generated at different values of

applied current, run in COMSOL Multiphysics software

69

xiii

Table 4.3 Magnetic flux density generated by the piston of the MRF

damper used

71

Table 4.4 Properties of the MRFs used [1]

73

Table 4.5 Percentage increment of the values of damping force and

magnetic flux density taken at side and bottom surfaces of the

piston

82

Table 4.6 Various amount of current to produce 106.2 N

85

Table 5.1 Sequence of events in gait cycle (Seymour, 2002)

87

Table 5.2 Temporal and distance variables in gait cycle (Kadabam

Ramakrishnan, & Wootten, 1990; Levangie & Norkin, 2011;

Perry & Burnfield, 1992; Seymour, 2002)

88

Table 5.3 Lower limb segment measurement

93

Table 6.1 Fuzzy PID controller decisions rules 110

Table 6.2 Intervals assigned to the input and output of the F-PID controller

111

xiv

LIST OF FIGURES

Figure 1.1 Levels of lower extremity amputations (Capital Health,

n.d.)

2

Figure 1.2 MR prosthetic knee as developed by Herr and Wilkenfeld

(2003)

5

Figure 1.3 The arrangement of magnetic particles

(a) without magnetic field (b) with magnetic field

6

Figure 1.4 Magnetorheological fluid on a 0.437T magnet

6

Figure 1.5

Flow of a viscous fluid through a parallel duct 8

Figure 1.6

MRF flows through a parallel duct 9

Figure 1.7 Research process flow

14

Figure 2.1 SACH foot

20

Figure 2.2 Schematic of a prosthetic knee (Gao, Liu, & Liao, 2017) 24

Figure 2.3 The coil aspect ratio,

2

1

c

c

L

Lis shown (Zeinali, Mazlan, Choi,

Imaduddin, & Hamdan, 2016)

26

Figure 2.4 Yield stress curve function for applied field at (a) different

particle size and (b) different distribution, as presented by

(Chiriac & Stoian, 2009)

29

Figure 2.5 An example of finite state machine diagram for level

ground walking (Simon et al., 2014)

31

Figure 2.6 PID controller block diagram

33

Figure 2.7 Fuzzy logic system block diagram

34

Figure 2.8 The output of the triangular membership function, μ(x)

defined between 0 and 1

35

Figure 3.1 2D MRF damper model in COMSOL Multiphysics

software

38

Figure 3.2 Boundary conditions assigned to the model 40

xv

Figure 3.3 Velocity profile of the fluid

40

Figure 3.4 BH curve for Iron particle

41

Figure 3.5 Alignment of the magnetic particles parallel to the flux

lines

43

Figure 3.6 The effect of adding solid particles to the viscosity of the

fluid

44

Figure 3.7 Stress generated as the particle size increases while

maintaining the number of particles suspended in the fluid

46

Figure 3.8 Stress profile using 30 magnetic particles

48

Figure 3.9 Shear stress generated by the fluid at different particle

ratio

(particle size, d = 2 μm)

49


ratio


50


ratio


50


ratio


50


ratio


51


ratio


51


ratio


51


ratio


52


ratio

52

xvi



ratio


52


ratio


53

Figure 3.20 Stress Profile at different values of particle ratio, d for

0.1A Icoil 0.2A

54

Figure 3.21 Particle interaction force at different values of particle

ratio, under different levels of magnetic field

55

Figure 3.22 The arrangement of particles in COMSOL Multiphysics

software

57

Figure 3.23 Shear stress generated at different particle size, for both

monodispersed and composite particles

58

Figure 3.24 Shear stress generated at different particle ratio, for both

monodispersed and polydispersed particles

59

Figure 3.25 Damping values normalized by body weight throughout

the stance phase (Rouse, Hargrove, Perreault, & Kuiken,

2012)

60

Figure 3.26 Different amount of applied current, particle ratio and size

to provide different damping values at four perturbation

timing instances (a) τ = 9.64 kPa, (b) τ = 8.84 kPa (c) τ =

17.7 kPa (d) τ = 30.5 kPa

62

Figure 3.27 Stress profile at Icoil = 200 mA

64

Figure 4.1 Initial design of the monotube damper (a) damper

components and (b) assembled damper

66

Figure 4.2 Damping force exhibited by damper shown in Figure 4.1

67

Figure 4.3 The bypass MRF damper used, to replace the monotube

damper

67

Figure 4.4 Magnetic flux density generated at Icoil = 1A

69

Figure 4.5 Measuring the amount of magnetic flux density generated

using a gaussmeter

70

xvii

Figure 4.6 Piston head, with and without housing

70

Figure 4.7 Graphical representation of current varying magnetic

field, with and without piston housing

72

Figure 4.8 MRF-122 EG under the microscope

74

Figure 4.9 MRF-132DG under the microscope

74

Figure 4.10 Schematic diagram of the experimental setup

75

Figure 4.11 Experimental setup 75

Figure 4.12 Force response of the damper filled with MRF-122 EG, at

300mm/min

76


400mm/min

76


500mm/min

77

Figure 4.15 Force response of the damper filled with MRF-132 DG, at

300mm/min

77


400mm/min

78


500mm/min

78

Figure 4.18 Force-displacement curve of MRF at 300mm/min, at 1.2A

of applied current

79

Figure 4.19 Damping force generated by MRF-132DG at 1.2A of

applied current, at three different velocities

80

Figure 4.20 Initial position of the piston

81

Figure 4.21 The location of piston, when the force is at its highest

81

Figure 4.22 Percentage increment of the magnetic flux density around

piston and its effect on the increment of damping force

produced by the damper

83

Figure 4.23 Damping force generated by the MRF damper at 30mm of

stroke length

84

Figure 4.24 Various amount of current producing 106.2N

84

xviii

Figure 5.1 Human gait cycle (Neumann, 2013)

87

Figure 5.2 Human leg segment (Model taken from OpenSim 3.2) 89

Figure 5.3 Link-segment-model (thigh, shank and foot) for single

human leg (Model taken from OpenSim 3.2)

90

Figure 5.4 External forces acting on (a) thigh (b) shank and (c) foot 91

Figure 5.5 Human lower limb in one gait cycle

93

Figure 5.6 Human lower limb joint angles in one gait cycle 94

Figure 5.7 Five stages of stance phase

94

Figure 5.8 Ground reaction force of an able-bodied person (Winter,

2009)

96

Figure 5.9 GRF of the subject wearing single axis foot

97

Figure 5.10 GRF of the subject wearing SACH foot

98

Figure 5.11 Ankle joint angle of the subject wearing SACH foot

98

Figure 5.12 Ankle joint angle of the subject wearing single axis foot

99

Figure 5.13 Ankle joint angle for amputated and intact limbs

100

Figure 6.1 The location of Gastrocnomius and soleus muscles (that

form calf muscles) and Achilles tendon ("Achilles

Tendon," 2015)

102

Figure 6.2 Simplified model of transtibial prosthetic limb with linear

MRF damper.

102

Figure 6.3 (a) and (b) Trantibial prosthetic limb

105

Figure 6.4 Control system block diagram of mrf damper in prosthetic

limb

105

Figure 6.5 Block diagram of transtibial prosthetic limb in MATLAB

Simulink

106

Figure 6.6 Block diagram of the system with PID controller

108

Figure 6.7 Simulated ankle angle with PID controller

108

Figure 6.8 Block diagram of the system with F-PID controller 109

xix

Figure 6.9 Controller design using MATLAB Fuzzy Logic Designer

110

Figure 6.10 Surface plots of the governing fuzzy rules for (a) Kp, (b)

Ki and (c) Kd

112

Figure 6.11 Simulated ankle angle with F-PID controller

113

Figure 6.12 Percentage error of the response of the system, with PID

and F-PID controller

114

Figure 6.13 The adjusted PID gains 114

Figure 6.14 Simulated stroke length before foot flat

115

Figure 6.15 Amount of damping force needed in response to the

vertical GRF applied to the foot

116

Figure 6.16 Current applied to the MRF damper before foot flat

116

Figure 6.17 Amount of ankle torque produced by the linear MRF

damping force

117

Figure 6.18 GRF with impact at heel strike

118


vertical GRF applied to the foot with impact at heel strike

118


vertical GRF applied to the foot after foot flat

119

Figure 6.21 Current applied to the MRF damper after foot flat

120

Achilles Tendon. (2015).

Capital Health. (n.d.). Lower Limb Amputations. Retrieved 18 Jun, 2014, from

http://www.cdha.nshealth.ca/amputee-rehabilitation-musculoskeletal-program/patient-family-

information/lower-limb-amputations

Chiriac, H., & Stoian, G. (2009). Influence of the particles size and size distribution on the magnetorheological

fluids properties. IEEE Transactions on magnetics, 45(10).

Gao, F., Liu, Y.-N., & Liao, W.-H. (2017). Optimal design of a magnetorheological damper used in smart

prosthetic knees. Smart Materials and Structures, 26(3), 035034.

Herr, H., & Wilkenfeld, A. (2003). User-adaptive control of a magnetorheological prosthetic knee. Industrial

Robot: An International Journal, 30(1), 42-55.

Rouse, E. J., Hargrove, L. J., Perreault, E. J., & Kuiken, T. A. (2012). Estimation of human ankle impedance

during walking using the Perturberator robot. Paper presented at the Biomedical Robotics and

Biomechatronics (BioRob), 2012 4th IEEE RAS & EMBS International Conference on.

Zeinali, M., Mazlan, S. A., Choi, S.-B., Imaduddin, F., & Hamdan, L. H. (2016). Influence of piston and magnetic

coils on the field-dependent damping performance of a mixed-mode magnetorheological damper. Smart

Materials and Structures, 25(5), 055010.

http://www.cdha.nshealth.ca/amputee-rehabilitation-musculoskeletal-program/patient-family-information/lower-limb-amputations

http://www.cdha.nshealth.ca/amputee-rehabilitation-musculoskeletal-program/patient-family-information/lower-limb-amputations

xx

LIST OF SYMBOLS

∆p pressure difference

η field-independent post-yield plastic viscosity

ɳmix viscosity of the mixture

ɳf viscosity of the carrier fluid

θh, hip angle

θk knee angle

θa ankle angle

i joint Angular velocity

i joint angular acceleration

τ wall shear stress.

τ0 yield stress caused by the applied field

τankle_output torque around ankle joint,

ϕ MRF particle ratio

ϕmax maximum packing density

Ap cross-sectional area of the piston head

𝐷 damper dynamic range

Icoil applied current

F damper force

Fη damping force due to viscosity

Fτ damping force due to magnetic field

Ff friction force

𝐹𝑢𝑐 uncontrollable force

Fx horizontal component of ground reaction force (GRF).

Fy vertical component of ground reaction force (GRF).

FH, hip reaction force

FK knee reaction force

FA ankle reaction force

Kp PID constant (proportional gain)

Ki PID constant (Integral gain)

Kd PID constant (Derivative gain)

L effective axial pole length

Ld damper moment arm

Q volume flow rate

T joint torque

V particle volume

a linear acceleration

c damping coefficient

d MRF particle size

dp(x)/dx pressure gradient in longitudinal coordinate

h gap size

m body mass

v0 velocity of the piston head

w mean circumference of the damper’s annular flow path

H magnetic field

xxi

M magnetization

m magnetic moment acting on each particle

1

CHAPTER 1

INTRODUCTION

1.1 OVERVIEW

Prosthetic limb is an artificial replacement of a missing limb. The demands of prosthetic

limb are usually related to the rate of amputations. Common reasons for limb

amputations include diseases, trauma, birth defects, poor blood circulation to the limb

and severe injuries due to accidents. In Malaysia, the most common cause of limb

amputation is due to diabetes mellitus (DM) (Engkasan, Ehsan, & Chung, 2012; Yusof

et al., 2015). According to the National Health and Morbidity Survey (NHMS) in 2011,

there are 2.6 million of adults (aged 18 and above) are diagnosed with diabetes, which

constitutes to 15.2% of the population (Diabetes Malaysia, 2015). In 2015, the figure

further increases to 17.5% (Ahmad, 2015). With this trend, it is foreseen that the rate of

amputation increases over time which in turn, resulted in the increment of the demand

for prosthetic limb.

Amputation affects a person’s life. Lower limb amputation especially, is a life-

changing event as it greatly affects one’s mobility. Thus, amputees are highly

encouraged to go through rehabilitation programme, to ensure that they are mentally

and physically prepared to face a new challenging phase in their life. In this program,

prosthesis fitting and gait training are included. Different levels of lower limb

amputation are displayed in Figure 1.1.

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Figure 1.1 Levels of lower extremity amputations (Capital Health, n.d.)

The earliest design of prosthesis, dated around 3000 years ago, was made of

wood and iron (Brooker, 2012). With the expansion of knowledge and technological

advancement, the designs of prostheses have undergone tremendous evolution, from

being solely cosmetic and intended to hide injuries during battle, to the ones that are

fully functional, offer stability, more realistic and comfortable. People with prosthetic

limb are usually less active than able-bodied people. They tend to have inefficient gait

pattern (Esquenazi, 2014; Graham, Datta, Heller, & Howitt, 2008; Major, Twiste,

Kenney, & Howard, 2014), which might affect their health condition. It is

recommended for the prosthesis to at least achieve community ambulation, which refers

to the ability of a person to walk in their own community, outdoor or indoor, performing

daily activities of a healthy person (Barclay et al., 2015; Parker, Kirby, Adderson, &

Thompson, 2010).

People with transtibial amputation functioned better than transfemoral amputees

(Cox, Williams, & Weaver, 2011; Vogel, Petroski, & Kruse, 2014) due to the existence

of the intact knee. In designing the prosthetic limb, one of the key element to be

considered is the shock absorption. In a healthy leg, apart from the elasticity of bone,

cartilage and soft tissues; muscle and tendon work concurrently to attenuate shock in

3

order to protect the joints and other tissues (Grech, Formosa, & Gatt, 2016; Gruber,

Boyer, Derrick, & Hamill, 2014; Pratt, 1989) . Thus, when muscles are weak or poorly

coordinated, the lack of responses from them might impose injury to the person over

time.

According to the Merck Manuals (Baird, 2015), prosthetic limbs consist of three

parts which are the interface, the components and the cover.

Table 1.1 Three parts of prosthetic limbs

Part Description

Interface

• Attach prosthesis to body

• Consist of a socket and rigid frame

• May include suspension system

Components

• Working parts of the prosthesis

• Attach to the body via socket

• Include terminal devices (artificial fingers, hand, feet

and toe), joints (wrist, elbow, hip and knee) and metal

shafts (act as bones)

Cover • To conceal components

• Optional, depends on the amputees

Prostheses can be divided into three; namely passive, semi-active and active prostheses,

which are grouped based on the mechanism used for shock attenuation.

1. Passive prosthetic limb

This type of prosthetics is usually made of elastic material such as carbon fiber

reinforced composite material or titanium (Park, Yoon, Kang, & Choi, 2016). It

is driven by gross body movement and provide some basic functional

capabilities. Passive prostheses are usually preferred for cosmetic purpose as it

closely resembles human limb. However, the drawback of wearing passive

by nor hidayati diyana binti nordin a thesis submitted in

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