Faculty of Engineering · otot buatan pneumatik (PAM) sebagai sistem penggerak telah dilakukan...

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Master of Engineering

2019

Faculty of Engineering

Development of Ankle Foot Orthosis (AFO) Using Pneumatic Artificial

Muscle (PAM)

Nurhanna Zulaikha binti Ishak

Development of Ankle Foot Orthosis (AFO) Using Pneumatic Artificial

Muscle

Nurhanna Zulaikha Binti Ishak

A thesis submitted

In fulfilment of the requirements for the degree of Master of Engineering

(Mechanical and Manufacturing Engineering)

Faculty of Engineering

UNIVERSITI MALAYSIA SARAWAK

2019

i

DECLARATION

The thesis has not been accepted for any degree and is not concurrently submitted in

candidature of any other degree.

Signature:

Name:

Matric No.:

Date:

ii

ACKNOWLEDGEMENT

Various parties have been involved directly and indirectly in many ways during the

accomplishment of this research. Firstly, all praises and thanks to Allah as only Him, I will

able done my thesis successfully. Without Allah grace, this research would not the same as

presented here.

Secondly, I wish to express my special appreciation to my supervisor, Dr Shahrol

bin Mohamaddan for his generous guidance, advice and encouragement towards

completing this research. Also special thanks to Prof Shin-Ichiroh Yamamoto and his

fellow research team from Shibaura Institute of Technology Japan, who helping me

develop ideas in this research and their generous attitude along with my presence there.

Special thanks to my lovely ummi, Aminah Mok and dad, Ishak Eli for their

untiring moral and giving fully financial support, which had been contributed toward

accomplishing thought out this research was highly appreciated.

Last but not least, I would like to express my gratefulness to my lovely course

mates and friends for their constant assistance, knowledge and help on various matters.

Their support and constructive ideas was indeed a great help to me out the years.

I humbly extend my thanks to anyone who co-operated with me in this regard.

Thank you.

iii

ABSTRACT

Ankle foot orthosis (AFO) is commonly used for a patient who had difficulty on their joint

weakness of lower limb, which to correct the instabilities and improve gait pattern. Many

studies have explored of dorsiflexion and plantarflexion on AFO. However, a few

researchers combine the eversion motion on AFO. The eversion motion has been not

introduced widely as dorsiflexion and plantarflexion motion and only have minimal data

analysis from previous research. The implementation of pneumatic artificial muscle (PAM)

as an actuation system was initiated for controlling the AFO which mimics the biological

human muscle tendon. Thus, this research introduces the development of AFO using PAM

that assists dorsiflexion, plantarflexion and eversion motion. This research started with

anthropometry measurement (n=5, age=12 years old) with 18 body dimensions on the

lower limb, and applied to AFO design by using Computer Aided Design (CAD) software.

The final design of AFO was fabricated by using a 3D printer. The PAM was fabricated

and been tested by using a test bed machine to test the PAM performance before being

used for AFO. To determine AFO performances, this research performed with normal

children (age = 12 years old) with two walking conditions which is using passive and

active AFO. As a result, AFO performances allowed free ankle movement during stance

phase and also allowed to perform proper dorsiflexion by ~5° which avoids toe drag during

swing phase hence avoid the foot drop to occur as well. The AFO shows the eversion

motion can move up to ~9° from the neutral position (0°). The results from AFO

performance by walking trials demonstrated that the newly developed AFO is provided the

assisted for foot drop condition which can contribute to the future opportunities with real

foot drop syndrome patient.

iv

Keywords: Ankle Foot Orthosis (AFO), Pneumatic Artificial Muscle (PAM), 3D Printer,

human gait

v

Pembangunan Orthosis Pergelangan Kaki (AFO) menggunakan Otot Tiruan

Pneumatik (PAM)

ABSTRAK

Ortosis pergelangan kaki (AFO) sering digunakan untuk pesakit yang mengalami

kelemahan dan kesukaran anggota badan yang lebih rendah, dimana ia memperbaiki

ketidakstabilan dan pola gait. Pelbagai kajian telah menerokai dorsiflexion dan

plantarflexion pada AFO. Walau bagaimanapun, hanya beberapa penyelidik telah

menggabungkan gerakan eversion pada AFO. Gerakan eversion tidak diperkenalkan

secara meluas seperti pergerakan dorsiflexion dan plantarflexion dan ianya juga

mempunyai minimal analisis data dari penyelidikan eversion sebelumnya. Pelaksanaan

otot buatan pneumatik (PAM) sebagai sistem penggerak telah dilakukan untuk mengawal

AFO yang menyerupai biologi tendon otot manusia. Oleh itu, kajian ini memperkenalkan

pembangunan AFO menggunakan PAM yang membantu gerakan dorsiflexion,

plantarflexion dan eversion. Kajian ini bermula dengan pengukuran antropometri (n = 5,

umur = 12 tahun) dengan 18 dimensi badan pada bahagian bawah dan digunakan pada

reka bentuk AFO dengan menggunakan perisian Bantuan Berbentukan Komputer (CAD).

Reka bentuk akhir AFO dibuat dengan menggunakan pencetak 3D. PAM direka dan diuji

dengan menggunakan mesin test bed untuk menguji prestasi PAM sebelum ia digunakan

untuk AFO. Bagi menentukan prestasi AFO, kajian ini dijalankan dengan melalui kanak-

kanak normal (umur = 12 tahun) diikuti dengan dua syarat berjalan yang menggunakan

AFO pasif dan aktif. Hasilnya, AFO membenarkan pergerakan buku lali secara bebas

semasa fasa pendirian dan juga dibenarkan untuk melakukan dorsiflexion yang betul

dengan ~ 5° yang menghindari penyeretan kaki semasa fasa ayunan dan seterusnya

vi

mengelakkan penurunan kaki berlaku juga. AFO menunjukkan gerakan eversion boleh

bergerak sehingga ~ 9° dari kedudukan neutral (0°). Hasil daripada prestasi AFO dengan

ujian berjalan menunjukkan bahawa perkembangan AFO yang baru dapat membantu

keadaan penurunan kaki seterusnya, dapat menyumbang kepada peluang masa depan

dengan pesakit sindrom penurunan sebenar.

Kata kunci: Orthosis pergelangan kaki (AFO), otot pembuatan pneumatik (PAM),

Pencetak 3D, gaya berjalan manusia

.

vii

TABLE OF CONTENTS

Page

DECLARATION .................................................................................................................. i

ACKNOWLEDGEMENT .................................................................................................. ii

ABSTRACT ........................................................................................................................ iii

ABSTRAK ............................................................................................................................. v

TABLE OF CONTENTS .................................................................................................. vii

LIST OF TABLES ............................................................................................................... x

LIST OF FIGURES ........................................................................................................... xii

LIST OF ABBREVIATIONS ........................................................................................... xv

LIST OF APPENDICES .................................................................................................. xvi

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

1.1 Research Bakground .................................................................................................... 1

1.2 Problem Statement ....................................................................................................... 3

1.3 Research Objectives ..................................................................................................... 4

1.4 Significance of the Study ............................................................................................. 4

1.5 Scopes and Limitation .................................................................................................. 4

1.6 Organization of Study .................................................................................................. 5

Line ........................................................................... Error! Bookmark not defined.

CHAPTER 2: LITERATURE REVIEW .......................................................................... 7

2.1 Introduction .................................................................................................................. 7

2.2 Biomechanics of Ankle-Foot ....................................................................................... 7

viii

2.3 Foot Drop Gait Cycle ................................................................................................... 9

2.4 Impaired Gait of Foot Drop, Inversion and Eversion ................................................ 11

2.5 Ankle Foot Orthosis ................................................................................................... 15

2.5.1 Passive AFO .................................................................................................. 17

2.5.2 Semi-Active AFO .......................................................................................... 20

2.5.3 Fully Active AFO .......................................................................................... 22

2.5.4 AFO Summary ............................................................................................... 26

2.6 Pneumatic Artificial Muscle (PAM) .......................................................................... 31

2.6.1 Braided Muscles ............................................................................................ 33

2.7 Summary .................................................................................................................... 35

CHAPTER 3: METHODOLOGY ................................................................................... 37

3.1 Introduction ................................................................................................................ 37

3.2 Anthropometric Measurement ................................................................................... 38

3.3 Designing AFO .......................................................................................................... 40

3.4 Simulation Analysis ................................................................................................... 42

3.5 AFO Fabrication ........................................................................................................ 44

3.6 Fabrication of Pneumatic Artificial Muscle (PAM)................................................... 45

3.7 PAM Experimental..................................................................................................... 48

3.8 Orthosis Control Systems ........................................................................................... 50

3.9 Selection and Placement of Sensor ............................................................................ 55

3.10 Biomechanical Assessment of AFO........................................................................... 58


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CHAPTER 4: RESULTS AND DISCUSSION ............................................................... 60

4.1 Introduction ................................................................................................................ 60

4.2 Anthropometric Measurement ................................................................................... 60

4.3 Final Design Drawing ................................................................................................ 62

4.4 AFO Simulation Analysis .......................................................................................... 64

4.5 PAM Analysis ............................................................................................................ 66

4.5.1 0 kg Load PAM ............................................................................................. 67

4.5.2 1 kg Load PAM ............................................................................................. 70

4.6 AFO Fabrication ........................................................................................................ 73

4.7 Joint Kinematics ......................................................................................................... 77

4.7.1 Pilot Experiment on Adult ............................................................................. 78

4.7.2 Real Experiment on Children (Dorsiflexion and Plantarflexion) .................. 81

4.7.3 Real Experiment on Children (Eversion) ...................................................... 83

4.8 Summary .................................................................................................................... 84


CHAPTER 5: CONCLUSION AND RECOMMENDATIONS .................................... 85

5.1 Conclusion ................................................................................................................. 85

5.2 Recommendations ...................................................................................................... 87


REFERENCES .................................................................................................................. 89

APPENDICES .................................................................................................................... 99

x

LIST OF TABLES

Page

Table 2.1 Description of Gait Stance Phases (Uusal and Baerga, 2004) ..................... 10

Table 2.2 Description of Gait Swing Phases (Uusal and Baerga, 2004). .................... 11

Table 2.3 Passive AFO types (Buckon et al., 2001). ................................................... 28

Table 2.4 Semi-Active AFO types ............................................................................... 29

Table 2.5 Fully Active AFO types ............................................................................... 30

Table 3.1 18 Dimension on lower limb........................................................................ 38

Table 3.2 Comparison between conceptual design 1 and 2. ........................................ 42

Table 3.3 Speed and temperature for 3D printer filament. .......................................... 45

Table 3.4 Air compressor specification. ...................................................................... 52

Table 3.5 The block diagram of sensor control which dictates the PAM

condition and direction of dorsiflexion and plantarflexion of AFO .......... 56

Table 4.1 Descriptive statistics of dimension measurement (cm). .............................. 61

Table 4.2 Ankle angle data during wearing passive AFO and active AFO. ................ 80

Table 4.3 Ankle angle data during wearing passive AFO and active AFO. ................ 82

xi

LIST OF FIGURES

Page

Figure 2.1 Anatomical Plane Shown with Spatial Coordinate System (Winter,

2009). ............................................................................................................. 8

Figure 2.2 The multi -joint mechanism of human ankle -foot complex

(Boonpratatong and Ren, 2010) ..................................................................... 9

Figure 2.3 Gait Cycle Phase can be divided into two phases during gait walking

which is stance phase and swing phase (Sofla, 2012). ................................ 10

Figure 2.4 Stiffness characteristic of ankle of a normal gait. HS: Hill strike, FF:

Flat foot, MD: Maximum dorsiflexion, and TO: Toe off (Romkes,

2008 ). .......................................................................................................... 12

Figure 2.5 Muscle pathology of lower limb that can lead to foot drop syndrome

(Femke, 2015). ............................................................................................. 13

Figure 2.6 Muscle that involves during inversion and eversion (Shorter, 2013) .......... 14

Figure 2.7 X-ray of a normal ankle joint (TeachMeAnatomy, 2016) ........................... 15

Figure 2.8 Lateral view of passive AFO (a) hinged AFO (b) posterior leaf spring

AFO and (c) solid AFO (Buckon, 2001). .................................................... 17

Figure 2.9 Hybrid AFO with linear spring and thermoplastics AFO (Teyssedre,

2005). ........................................................................................................... 19

Figure 2.10 Magneto rheology (MR) damper AFO and torque amplifying

mechanical linkage (Furusho et al., 2007). .................................................. 21

Figure 2.11 The Arizona State AFO powered by a modified series elastic actuator

(Boehler et al., 2008) .................................................................................. 22

Figure 2.12 Active Ankle Foot Orthosis (AAFO) using pneumatic artificial

actuator (Ferris, Czerniecki, and Hannaford, 2005). ................................... 23

Figure 2.13 Anklebot assist dorsiflexion and plantarflexion motion (Roy et al.,

2007) ............................................................................................................ 24

Figure 2.14 Robotic gait trainer (Bharadwaj et al., 2005). .............................................. 25

Figure 2.15 LOKOMAT (picture coutesy of HOKOMA). ............................................. 26

xii

Figure 2.16 Comparison of dorsiflexion and plantarflexion of normal gait (without

AFO), SAFO and AAFO (Hwang et al., 2006) ........................................... 27

Figure 2.17 PAM operation at constant load (Choi, Jin, and Lee, 2006) ........................ 32

Figure 2.18 PAM operation at constant pressure (Choi, Jin, and Lee, 2006). ................ 33

Figure 2.19 McKibben Muscle (Okayama University, 2001). ........................................ 34

Figure 3.1 Workflow for methodology. ........................................................................ 37

Figure 3.2 Standard professional anthropometer tools (ROSSCRAFT,Canada). ......... 39

Figure 3.3 Anthropometry measurement on foot breath horizontal. ............................. 40

Figure 3.4 Anthropometry measurement on calf girth. ................................................. 40

Figure 3.5 Workflow for analyzing the component. ..................................................... 43

Figure 3.6 FLASHFORGE 3D printer. ......................................................................... 44

Figure 3.7 FlashPrint software. ..................................................................................... 45

Figure 3.8 FLEXO PET mesh stripe (PTN 1.00BL). .................................................... 46

Figure 3.9 Shaft component .......................................................................................... 46

Figure 3.10 Shaft component, nitrile rubber, washer and nut is arranged in order ......... 47

Figure 3.11 Shaft component at the both end of rubber tube .......................................... 47

Figure 3.12 Copper ring placed at the both end .............................................................. 47

Figure 3.13 Tighten the copper ring by using Three Jaws Chuck ................................... 48

Figure 3.14 Final PAM .................................................................................................... 48

Figure 3.15 Test Bed machine. ........................................................................................ 49

Figure 3.16 Test bed system. ........................................................................................... 50

Figure 3.17 Control System Scheme ............................................................................... 51

Figure 3.18 Air compressor JD-2540B(F). ..................................................................... 52

Figure 3.19 Solenoid valve, female coupling, female reducer coupling and

pneumatic tube fitting arranged in order. ..................................................... 53

xiii

Figure 3.20 Pneumatic tube fitting connected with silicone rubber tube. ....................... 54

Figure 3.21 Single channel BB relay 5V breakout .......................................................... 54

Figure 3.22 Force resistive sensor 0.5 inches. ................................................................. 55

Figure 3.23 Distribution of pressure of the AFO during walking (Tekscan, 2012). ....... 56

Figure 3.24 Sensor flowchart process ............................................................................. 57

Figure 3.25 ADXL335 3-Axis Accelerometer. ............................................................... 57

Figure 3.26 Circuit diagram by Fritzing Software .......................................................... 58

Figure 4.1 Technical Drawing of Assembled AFO with measurement (mm). ............. 63

Figure 4.2 Final Design of 3D Drawing in Isometric View. ......................................... 64

Figure 4.3 Displacement AFO Analysis........................................................................ 65

Figure 4.4 Safety Factor AFO Analysis. ....................................................................... 66

Figure 4.5 Load 0 kg, 0.1 Hz, ~30 mm displacement. .................................................. 68

Figure 4.6 Load 0 kg with linear system PAM. ............................................................ 68


Figure 4.8 Load 0 kg with nonlinear system PAM. ...................................................... 70





Figure 4.13 AFO prototype in CAD software with specific details. ............................... 74

Figure 4.14 Final prototype of AFO fabrication by using 3D printer. ............................ 75

Figure 4.15 Prototype AFO assembled on subject’s right leg. ........................................ 76

Figure 4.16 PAM assisted ankle motion of (a) dorsiflexion and (b) plantarflexion. ...... 77

Figure 4.17 Ankle joint range of motion. ........................................................................ 80

xiv

Figure 4.18 Ankle joint range of motion. ........................................................................ 81

Figure 4.19 Eversion angle during AFO assistance ........................................................ 83

xv

LIST OF ABBREVIATIONS

AAFO Active Ankle Foot Orthosis

AFO Ankle Foot Orthosis

CAD Computer Aided Design

COG Center of Gravity

EMG Electromyography

GRF Ground Reaction Force

HAFO Hinged Ankle Foot Orthosis

M Mass of Foot

MR Magneto Rheological

PAM Pneumatic Artificial Muscle

PLS Posterior Leaf Spring

SAFO Solid Ankle Foot Orthosis

SEA Series Elastic Actuator

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CHAPTER 1

INTRODUCTION

1.1 Background

Foot plays an important role in human motion such as standing, walking, running,

jumping, balancing and also withstand the force from weight bearing. The complexity of

the foot causes difficulty in analyzing and understanding the mechanism of motion

especially by means of quantification (Bahler, 2008). In general, the human foot composed

of three sections which are forefoot, midfoot and hindfoot. As for skeleton structure are

built from phalanges, metatarsals, talus, calcaneus and other parts and supported by

muscles, ligaments and tendons (Alcamo, 2003). The biomechanics of each part plays

important role in building up the kinetic and balancing system.

However, due to neurological disorder such as trauma, stroke, spinal cord injury

and cerebral palsy, it may disrupt the ability of human to walk properly (Veale & Xie,

2016). One of abnormal gait is foot drop syndrome. Foot drop syndrome is occurred due to

the weakness of distal muscles and extensor hypertonia in lower limb (Standford Medicine

25, 2016). This syndrome leads to excessive plantarflexion and weak dorsiflexion during

swing phase of the leg (Smalley, 2014). As a result, the patient may have the tendency to

walk on the toes where the affected foot striking the ground first instead of the usual heel

strikes (Romkes, 2006). The walking behavior will give harmful effect to the leg.

Aside from foot drop, inversion and eversion motion can occurred in lower limb.

Inversion and eversion is occurred when the ligaments are stretch out far from its normal

ligament. An inversion is the movements where the sole of the foot is facing inwards and

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eversion is the movements where the sole of the foot is facing outwards. In

general, ,inversion occurs more often compared to eversion (Walters, 2006).

Normally, an ankle foot orthosis (AFO) is introduced to patient who diagnosed with

foot drop syndrome. An AFO is a device or brace that covered the foot, ankle and also part

of leg (Chin et al., 2009). The device is used to correct the instabilities and joint

weaknesses of lower limb muscle (Chen, Tang, & Ju, 2001). Using AFO will improve the

mobility and can be used as rehabilitation devices to correct the motor patterns (Kao &

Ferris, 2009). Besides, by using AFO, the user may improve the walking pattern

performance by proper control motion of the device (Park et al., 2011).

Before the active AFO is been introduced, the rehabilitation for AFO was

conducted manually or traditionally by physiotherapist by making the repeated movement

(Hamid, Patar, & Ayub, 2012). Nowadays, the procedure has been replaced after the

advancement of technology with the mechanical actuator such as hydraulic, pneumatic or

motor actuator (active AFO) to actuate the AFO (Manzoor, Elkhbai, & Kkwaneen, 2007).

One of the actuator to control the AFO mechanism system is pneumatic artificial

muscle (PAM). Pneumatic artificial muscles (PAM) are type of actuator that contractile

and perform linear motion which usually operated by air pressure which filling a

pneumatic bladder (Daerden & Lefeber, 2002). The PAM is operated when it is pressurized;

the PAM will inflate and shorten when the gas is sucked out and the membrane is squeezed.

McKibben muscle type is widely used in AFO design since it is lightweight, capable at

high forces and can mimics or has similarity to the human skeletal muscles behaviour.

3

1.2 Problem Statements

AFO is a support at ankle foot which intended to compensate the weakness on that

area and also to correct deformities. By that, the foot and ankle can be stabilized during the

swing phase of gait. A lot of researcher had investigated the development of AFO.

However, most of them focused on avoid excessive plantarflexion or assist dorsiflexion

during swing phase. Another important aspect or criteria that is inversion syndrome to

correct the foot is yet to go through deep exploration and the development of AFO can be

further improved. Previous researcher (Park et al., 2011) introduced the eversion and

inversion motion on the AFO, however the data analysis results only focused on

dorsiflexion and plantarflexion. Thus, this study focuses on the development of AFO not

only to prevent plantarflexion but also to correct the foot from the inversion syndrome.

Besides that, in development of AFO, the fabrication is taken into account. The

fabrication usually takes time, labour work and sometimes expensive demand by custom

made AFO (Walbran, Turner, & Mcdaid, 2016). Fabrication normally required from

manually casting plastic method, thermoplastic molding method and cutting the form as a

finishing AFO. This whole process sometimes need to be repeated as the AFO is damaged

or the condition of patient is changed (Walbran, Turner, & Mcdaid, 2016). However, by

using 3D printer, the effort and skill that needed in fabrication is easier compared to

manual casting AFO method (Walbran, Turner, & Mcdaid, 2016). Furthermore, the

material used in AFO design by using 3D printer is more lightweight compare to casting

material.

Apart from that, Kao and Ferris (2009) stated that the PAM in their design had

some limitation where the size was considered is large and longer which offer no mobility

4

to user. A more compact and lightweight PAM are the preferable option for the actuator

mechanism. To compensate with human muscle, McKibben PAM type is better alternative

which offer more similar to biological muscles than other types of artificial muscle. In

Malaysia the AFO using PAM as an actuator has not widely introduced as PAM brings

many benefit to user. Thus, this research aims to develop the AFO using PAM for foot

drop patient. In this research, the material used in AFO design in by using 3D printer.

Meanwhile, a more compact and lightweight PAM is designed. This research introduces

the development of ankle foot orthosis (AFO) using pneumatic artificial muscle (PAM) for

foot drop patients.

1.3 Objectives of the Study

The objectives of this research are:

i. To design and fabricate the AFO for disabled children.

ii. To develop pneumatic artificial muscles for the AFO.

iii. To analyze human gait cycle with assisted of AFO.

1.4 Significance of the Study

The outcomes of this study will be useful information and guidelines to designer and

researcher in lower limb orthosis field with regards to:

i. Design the AFO to prevent excessive plantarflexion to occur and allow the eversion

motion.

ii. Using AFO will improve patient with foot drop syndrome walking pattern.

iii. AFO can be used as rehabilitation devices in training process.

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1.5 Research Limitation

The subject of this study is focus on children who suffered from foot drop

syndrome and who have difficulty in eversion motion. The study is focusing on the

rehabilitation or treatment on lower limb area by researching or studying, designing and

fabricating an AFO. However, some limitation should be noted:

i. Healthy subjects are chosen instead of real children patient who had foot drop

syndrome and difficulty in eversion motion to avoid any safety issue related to

patient.

1.6 Organization of the thesis

This thesis is divided into five chapters as follows:

i. Chapter 1, Introduction provides general background, idea and also the concept of

the studies.

ii. Chapter 2, Literature Review highlights and describes the previous studies related

to AFO where it provides basic understanding on the required information of

current AFO devices technology and identify the challenges or problems faced by

current AFO. At the end of the chapter a key of technology advances for new AFO

design along with the actuator and power supply to assist the new AFO are

highlighted.

iii. Chapter 3, Methodology, provides and describes all materials, relevant technique

and experimental that used in the whole process of project development. This

chapter introduces the AFO design which is capable to subject matter and describes

how both dorsiflexion and plantarflexion works by using pneumatic artificial

muscle (PAM). Besides, the integration of electronic parts to control the PAM

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(actuation) of the AFO is elaborated. The experimental data of healthy subject

demonstrated the ability of AFO.

iv. Chapter 4, Results and Discussion, shows the analysis and presentation of data of

final design, fabricated prototype and also include the output data for foot drop

motion. Overall, this chapter explains further about the characterization of AFO

performance on the gait for the healthy subjects.

v. Chapter 5, Summary and Conclusion, concludes the summary of the study

including the methods and results, and also the suggestion or recommendation for

future work of the study improvement.

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CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

This chapter highlights and review the previous studies related to the AFO device which

assist the plantarflexion and dorsiflexion while walking. By understanding the

plantarflexion and dorsiflexion will fulfil a characteristic that needed in designing AFO.

Besides, the understanding of human behavior will make it easier to perform AFO on

subjects. Hence, the human biomechanics of ankle-foot is studied.

2.2 Biomechanics of Ankle-Foot

Biomechanics is the study of body motion analysis using the application of

mechanic science (Hatze, 1974). Mechanics is one of the physics that is related to body

motion and how the motion is created by using forces (Knudson, 2007). The human ankle-

foot plays an important role in studying the human motion especially for normal and

abnormal locomotion. The Ground Reaction Forces (GRF) exerted from the human ankle-

foot complex transmits to thigh and shank of the leg and pushed the body forward and also

support the body weight during stance phase of walking (Boonpratatong & Ren, 2010).

However, the human foot complex can cause difficulties in understanding the motion

mechanism especially in the form of quantification.

The spatial coordinate system of the body is highlight to understand the

biomechanics of human ankle-foot. The spatial coordinate systems can be divided into

three planes which is sagittal plane, transverse plane and frontal plane referred in rotation

of foot-ankle joints as shown in Figure 2.1 (Winter, 2009).

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