A HEXAPOD ROBOTIC PLATFORM FOR MINIATURE
DRILLING OPERATIONS
BY
MURSHIDUZZAMAN
A thesis submitted in fulfilment of the requirement for the
degree of Master of Science (Mechatronics Engineering)
Kulliyyah of Engineering
International Islamic University Malaysia
MAY 2019
ii
ABSTRACT
Product miniaturization is a key aspect of manufacturing nowadays. Computer
numerically controlled (CNC) machine tools are the major tools used in manufacturing
industries for producing miniaturized products. However, CNC machines are still big,
bulky and stationary. This research is an effort to develop a robot which would be able
to carry out machining operation as a mobile plaform. There have been several
researches going on about the development and application of miniature multi legged
robots. Hexapod robots are small and stable mobile robots which are developed having
a lot of variety. But the main focus of researchers till now have been the structure and
motion of hexapod robots. However, not much research has been conducted about the
use of legged robot for machining application. In this project a Hexapod robot was
designed and fabricated for machining operation. The research scope for this project is
limited to 1-D machining i.e. drilling operation. This research demonstrates
methodically for the first time the feasibility of meso-scale machining using linked
mobile robotic platform. A suitable existing robot (hexapod) design was followed in
this project. A drilling spindle was attached with the robot to carry out the machining
operation. The robot was controlled using serial communication. A Graphical User
Interface (GUI) was developed to control the Hexapod which had all the required
algorithm inside. Machining operations were carried out with the prototype robot to
test its performance. A new compensation algorithm has been proposed to improve the
positional accuracy of the robot movement. The proposed algorithm takes into account
spindle speed and linear velocity to compensate the positional error. The positional
accuracy was improved by 85% after implementing the error compensation scheme. It
was seen that for lowest spindle speed which is 2500RPM and point to point velocity
200mm/min the repeatability was the best which was less than 30µm. The positional
accuracy of the robot movement was compared with that of an existing commercial
micromachining system. The performance of the robot was found to be almost similar
to that of the commercial machine. Finally, the machined hole quality was measured in
terms of circularity and taperness. It was observed that at the best machining parameter
setting, circularity deviation was as low as 0.016 mm and taperness was 0.547 degree.
iii
خلاصة البحث
العددي ت التحكم أدواان تصغير المنتج هو أحد الجوانب الرئيسية للتصنيع في الوقت الحاضر. ان .نتاج المنتجات المصغرة( هي الأدوات الرئيسية المستخدمة في الصناعات التحويلية لإCNCبالكمبيوتر )
ثابتة. هذا البحث هو و الحجم ومع ذلك ، لا تزال آلات التصنيع باستخدام الحاسب الآلي كبيرة وكبيرةاث الجارية حول تطوير هناك العديد من الأبح ،اتفالروبوت من تشغيل الآلي إلى منصة اله جهد لتطوير
، متزنصغير و نقال ت. ان الروبوت سداسي الارجل هو روبو وتطبيق الروبوتات الصغيرة متعددة الأرجلروبوتات اللى بنية وحركة عينصب لحد الان التركيز الرئيسي للباحثين ان. ه لانواع عديدةر يتطو تم الذي و
وت ذو ارجل للتشغيل ، لم يتم إجراء الكثير من الأبحاث حول استخدام روبومع ذلك .سداسية الارجلنطاق البحث لهذا انت. لتشغيل الآلا سداسي الارجلروبوت الهذا المشروع تم تصميم وتصنيع في .الآلي
ان المثال عملية الحفر. ، على سبيلD-1 الاحادي الاتجاه التشغيل عالتي تتبعلى الآلات يقتصر المشروع استخدام ب يستعرض بشكل منهجي ولاول مره جدوى التشغيل متوسط النطاق للالاتالبحث هذا
ابود( في هذا مناسب )هيكسسداسي الارجل تم اتباع تصميم روبوت الوسائل بمنصة هاتف الربوت.ستخدام لتحكم في الروبوت باتم ا .المشروع. تم إرفاق مغزل الحفر مع الروبوت لتنفيذ عملية التشغيل الآلي
داسي الأرجل للتحكم في س (GUI)الاتصال التسلسلي.وقد تم تطوير واجهة المستخدم الرسومية مليات التشغيل مع عوأجريت )هيكسابود( التي كانت تحتوي على جميع الخوارزميات المطلوبة داخلها.
الدقة الموضعية لحركة سين روبوت النموذج الأولي لاختبار أدائها. تم اقتراح خوارزمية تعويض جديدة لتحية لتعويض الخطأ الموضعي. تم تأخذ الخوارزمية المقترحة في الاعتبار سرعة الدوران والسرعة الخط .الروبوت
رعة للمغزل وهي سأدنى لقد وجد بان .٪ بعد تطبيق نظام تعويض الخطأ85تحسين دقة الموضع بنسبة 2500RPM 200و سرعة نقطة إلى نقطةmm / min ل من كرار الأفضل، حيث كان أقكان الت
30µm. يكانيكي التجاري القائم. وتمت مقارنة الدقة الموضعية لحركة الروبوت مع نظام التصنيع الميكرومصنوع قياس جودة الثقب المتمأخيرا اظهرت النتائج ان أداء الروبوت مشابه تقريبا لاداء الجهاز التجاري.و
راف الدئري منخضا كان الانحدوال معالم اعداد أفضل حالة في. لوحظ أنه دائرية والسمك من حيث ال درجة. 0.547 سمك، وكان ال ملم 0.016 الى
iv
APPROVAL PAGE
I certify that I have supervised and read this study and that in my opinion, it conforms
to acceptable standards of scholarly presentation and is fully adequate, in scope and
quality, as a thesis for the degree of Master of Science (Mechatronics Engineering).
…………………………………..
Tanveer Saleh
Supervisor
…………………………………..
Md. Raisuddin Khan
Co-Supervisor
I certify that I have read this study and that in my opinion it conforms to acceptable
standards of scholarly presentation and is fully adequate, in scope and quality, as a thesis
for the degree of Master of Science (Mechatronics Engineering).
…………………………………..
Amir Akramin Shafie
Internal Examiner
…………………………………..
Khairul Salleh Mohamed Sahari
External Examiner
This thesis was submitted to the Department of Mechatronics Engineering and is
accepted as a fulfilment of the requirement for the degree of Master of Science
(Mechatronics Engineering).
…………………………………..
Syamsul Bahrin Abdul Hamid
Head, Department of
Mechatronics Engineering
This thesis was submitted to the Kulliyyah of Engineering and is accepted as a
fulfilment of the requirement for the degree of Master of Science (Mechatronics
Engineering).
…………………………………..
Ahmad Faris Ismail
Dean, Kulliyyah of Engineering
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.
Murshiduzzaman
Signature........................................................... Date.........................................
vi
INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA
DECLARATION OF COPYRIGHT AND AFFIRMATION OF
FAIR USE OF UNPUBLISHED RESEARCH
A HEXAPOD ROBOT FOR MINIATURE MACHINING
OPERATIONS
I declare that the copyright holders of this thesis are jointly owned by the student
and IIUM.
Copyright © 2019 Murshiduzzaman 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 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 retrieved system
and supply copies of this unpublished research if requested by other
universities and research libraries.
By signing this form, I acknowledged that I have read and understand the IIUM
Intellectual Property Right and Commercialization policy.
Affirmed by Murshiduzzaman
……..…………………….. ………………………..
Signature Date
vii
ACKNOWLEDGEMENTS
Alhumdulillah, all praises to ALLAH (S.W.T), the Most Beneficial and Most Merciful,
to give me the ability and knowledge to accomplish my research work successfully. I
would like to thank my supervisor Dr. Tanveer Saleh for his dedicated guidance,
suggestions, motivation and valuable support which have directed me to develop my
research skills and knowledge. He has not only guided me as a supervisor but also
played the role of a guardian. I would also like to thank my co-supervisor Dr. Md.
Raisuddin Khan for his endless encouragement and support to my research work. I
would like to extend my gratitude to others who also have helped me in using research
instrument for my experiments as the technicians of the Engineering Laboratories in
IIUM.
I am also grateful to Mechatronics Engineering Department and Kulliyyah of
engineering for giving me the research facilities.
Finally, I would like to mention my parents who always keep me in their prayers
to almighty “ALLAH” for every single bit of my success.
viii
TABLE OF CONTENTS
Abstract .......................................................................................................................... ii Abstract in Arabic ......................................................................................................... iii Approval Page ............................................................................................................... iv Declaration ..................................................................................................................... v Copyright ...................................................................................................................... vi Acknowledgements ...................................................................................................... vii Table of Contents ........................................................................................................ viii List of Tables ................................................................................................................. x List of Figures ............................................................................................................... xi
List of Symbols ............................................................................................................ xv
List of Abbreviations .................................................................................................. xvi
CHAPTER ONE: INTRODUCTION ........................................................................ 1 1.1 Background ................................................................................................... 1 1.2 Problem Statement And Its Significance ...................................................... 2 1.3 Research Objectives ...................................................................................... 2 1.4 Research Methodology ................................................................................. 3
1.4.1 Methodology For Objective 1 ............................................................. 3 1.4.2 Methodology For Objective 2 ............................................................. 3 1.4.3 Methodology For Objective 3 ............................................................. 4 1.4.4 Methodology For Objective 4 ............................................................. 4
1.5 Research Scope ............................................................................................. 6 1.6 Thesis Organization ...................................................................................... 6
CHAPTER TWO: LITERATURE REVIEW ........................................................... 8 2.1 Introduction................................................................................................... 8 2.2 Hexapod Robots............................................................................................ 9
2.2.1 Comparing Locomotion Of Wheeled, Tracked And Legged
Robots ........................................................................................................ 10 2.2.1.1 Locomotion Using Wheel ...................................................... 11 2.2.1.2 Locomotion Using Tracks ..................................................... 11 2.2.1.3 Locomotion Using Legs ........................................................ 12
2.2.2 Configurations Of Legged Robot ...................................................... 13 2.2.2.1 Stability In Static And Dynamic State ................................... 13 2.2.2.2 Legged Robot’s Walking Speed ............................................ 15 2.2.2.3 Gait Diagrams Of Six Legged Robot .................................... 15
2.2.3 Hexapod Robots Existing Models .................................................... 20 2.3 Machining And Mobile Robots .................................................................. 28 2.4 Hexapod Robot Machines........................................................................... 34 2.5 Chapter Summary ....................................................................................... 36
CHAPTER THREE: DEVELOPMENT OF THE HEXAPOD ROBOT ............. 38 3.1 Introduction................................................................................................. 38 3.2 Hardware System Development ................................................................. 38
3.2.1 Mechanical Structure Of The Hexapod Robot System ..................... 38
ix
3.2.1.1 Body Configuration And Body Design ................................. 40 3.2.1.2 Legs Development Of The Hexapod ..................................... 42 3.2.1.3 Critical Load Calculation For Tibia Leg Link ....................... 45 3.2.1.4 Critical Load Calculation For Femur Leg Link ..................... 46 3.2.1.5 Motor Torque ......................................................................... 47 3.2.1.6 Static Stability........................................................................ 48 3.2.1.7 Machining Spindle ................................................................. 60
3.2.2 Control System Of The Hexapod Robot System .............................. 61 3.2.2.1 Electric Components.............................................................. 62 3.2.2.2 Power Supply ......................................................................... 64
3.3 Development Of The Gui Based Control System ....................................... 65 3.3.1 Gui Of The Hexapod ......................................................................... 70
3.3.1.1 Giving Xy Co-Ordinate For Multiple Point .......................... 73 3.3.1.2 Button Press Command For Hexapod Movement ................. 74 3.3.1.3 Sending Manual Command For Servo Position .................... 74
3.4 Chapter Summary ....................................................................................... 76
CHAPTER FOUR: EXPERIMENTAL SETUP, RESULTS AND
DISCUSSION ............................................................................................................. 77 4.1 Introduction................................................................................................. 77
4.1.1 Materials Preparation For The Experimental Setup .......................... 79 4.1.2 Characterization By Dino-Lite .......................................................... 81 4.1.3 Summary Of Characterization .......................................................... 83
4.2 Results And Discussion .............................................................................. 83 4.3 Positional Accuracy .................................................................................... 83
4.3.1 Benchmarking ................................................................................... 92 4.4 Hole Quality................................................................................................ 93
CHAPTER FIVE: CONCLUSIONS AND RECOMMENDATION .................... 95 5.1 Conclusions................................................................................................. 95 5.2 Recommendations....................................................................................... 96
REFERENCES ........................................................................................................... 97
PUBLICATIONS .................................................................................................... 109
APPENDIX .............................................................................................................. 109
108
x
LIST OF TABLES
Table 4.1 Variable parameters 82
Table 4.2 Average error found by using different parameters along x and y axis
(mm) 84
Table 4.3 Repeatability found by using different parameters (mm) 86
Table 4.4 Error in mm found after moving whole body 91
xi
LIST OF FIGURES
Figure 1.1 Complete Research Flow Chart 5
Figure 2.1 Support pattern used by a multi-legged robot , and the Center of
Mass (CoM) stays inside the support polygon created by the
supporting legs. If the CoM of the Robot stays inside the support
pattern then it is said that Static balancing is occurring. (Siciliano
& Khatib, 2008) 14
Figure 2.2 Two types of configurations which are popular in hexapod robots
16
Figure 2.3 Leg structure of an insect (Shahriari, 2013) 17
Figure 2.4 Leg movement of insects inspired these 4 gaits. Black bars mean
swing phase. Empty area between black bars denote the support
phase. Tripod gait is shown as number 1, Other dynamic gaits
which are seen naturally in the movement of insects like
cockroach (Beer, Quinn, Chiel, & Ritzmann, 1997). 18
Figure 2.5 A faster form of wave gait. Here 4 legs stay is support phase and
2 legs swing to make new footholds (Siciliano & Khatib, 2008).
19
Figure 2.6 Tripod gait. Because of three legs moving at the same time, the
static stability is good (Siciliano & Khatib, 2008). 19
Figure 2.7 Solid model of Robot III (Nelson et al., 1997). 20
Figure 2.8 RHex (Koditschek, Daniel ESaranli & Buehler, 2000) 21
Figure 2.9 Structural design of HITCR-II (Zhang et al., 2014) 22
Figure 2.10 Configuration of HITCR II’s leg (on left) and joint(on right)
(Zhang et al., 2014) 22
Figure 2.11 Wall climbing hexapod robot(on left) and concrete wall surface
& claw(on right) (Funatsu et al., 2014) 23
Figure 2.12 Thrust Mechanism (Funatsu et al., 2014) 23
Figure 2.13 Physical Tigerbug(Left) and Tigerbug in simulation
software(Right) (Sahin & Stevenson, 2015) 24
Figure 2.14 WEBX hexapod design (Webx Hexapod Project, n.d.) 25
xii
Figure 2.15 Round Hexapod(Left) and Rectangular Hexapod(Right) 26
Figure 2.16 Jumping Hexapod (Younse et al., n.d.) 27
Figure 2.17 Pulstech Hexapod (Pulstech, 2009) 28
Figure 2.18 Kiva (D’Andrea, Robot, & 2008, n.d.) 30
Figure 2.19 Timeline from Bogh, et al (Bøgh et al., n.d.) 31
Figure 2.20 Snapshot of simulation video showing drones being used for
palletizing (Amazon.com, 2014) 32
Figure 2.21 Hexapod robotic machining unit, (a) Hexapod platform (b)
Milling spindle attached (Tunc & Shaw, 2016) 34
Figure 2.22 SHeRo hexapod retracted (Left) and expanded (Right) (Agheli
et al., 2014) 345
Figure 2.23 Mobile robotic system for machining (Mobile CNC Base) 346
Figure 3.1 Complete Hexapod 3D design (Left) and Actual (Right)
Hexapod 39
Figure 3.2 Top (Right) and Bottom (Left) body plate [3D Design] 40
Figure 3.3 Top (Left) body plate and flipped view (Right) [Actual] 42
Figure 3.4 3D design of one leg with 3 servo and leg links 43
Figure 3.5 Leg and body links with attached servo horn 44
Figure 3.6 Simplified Structure of the Hexapod 45
Figure 3.7 Simplified Structure of the Hexapod 46
Figure 3.8 Support by 3 legs (robotshop, n.d.) 48
Figure 3.9 Non-perpendicular leg placement (robotshop, n.d.) 48
Figure 3.10 Free body diagram (robotshop, n.d.) 49
Figure 3.11 Stance 1 54
Figure 3.12 Stance 2 55
Figure 3.13 Stance 3 56
Figure 3.14 Stance 4 58
Figure 3.15 Spindle design with scotch yoke mechanism 61
36
35
xiii
Figure 3.16 Lynxmotion SSC-32u servo driver 62
Figure 3.17 12 Ampere Voltage Regulator 63
Figure 3.18 MD10C DC motor driver 63
Figure 3.19 Circuit diagram of the Hexapod robot 64
Figure 3.20 Excel file to calculate required motor rotation using Inverse
Kinematics (Oscarliang.com, n.d.) 66
Figure 3.21 Motor angular movement vs movement of hexapod 67
Figure 3.22 Compensation algorithm 69
Figure 3.23 Graphical User Interface (GUI) of the Hexapod Robot 70
Figure 3.24 Work flow of the GUI 71
Figure 3.25 GUI of the Hexapod robot 72
Figure 3.26 XY co-ordinate for Multiple points 73
Figure 3.27 GUI for CNC machining operation 74
Figure 3.28 Manual Command for Servo Position 75
Figure 3.29 String writing and Sending 75
Figure 4.1 Total experimental procedure 78
Figure 4.2 Levelling of the wooden block using leveler 79
Figure 4.3 Material Placement 80
Figure 4.4 Experimental Setup 81
Figure 4.5 View from Dino-lite 82
Figure 4.6 Graphical representation of average error found by using
different parameters 85
Figure 4.7 Repeatability found by using different parameters in mm 87
Figure 4.8 Graphical representation of repeatability found by using
different parameters 89
Figure 4.9 Graphical representation of average error after using
compensation 90
Figure 4.10 Graphical representation of error between the Hexapod robot
and a CNC machine 91
xiv
Figure 4.11 Error in mm found after moving whole body 92
Figure 4.12 Graphical representation of hole taperness found by using
different parameters 93
Figure 4.13 Graphical representation of standard deviation using different
parameters. 94
xv
LIST OF SYMBOLS
C# C Sharp
E Modulus of Elasticity
I Moment of Inertia
kg Kilo-gram
Kpa Kilo pascal
L1,2,3 Length of link
mm Millimeter
n Number of leg
N1,2 Normal (reaction) force
Pcr Critical Load
T1,2,3,4 Torque acting on joint
V Voltage
W4 Weight of link
3-D Three dimensional
β Duty Factor
σ Bending Stress
µm Micro-meter
ϴ1,2
Angle between leg links
xvi
LIST OF ABBREVIATIONS
CNC Computer Numerically Controlled
CoM Centre of Mass
Coxa Co-Axial
DC Direct Current
DOF Degree Of Freedom
EKF Extended-Kalman-Filter
GUI Graphical User Interface
IC Integrated Circuit
IK Inverse Kinematics
Li-Po Lithium Polymer
MDI Manual Data Input
PCB Printed Circuit Board
R/C Radio Control
RFID Radio Frequency Identification
USB Universal Serial Bus
3D Three Dimensional
1
CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND
A research in 2007 states that ,CNC machine tools have been in use in the manufacturing
sectors for more than 50 years (Thomas, 2007). It is one of the key processes used for
micro fabrication. Recently, demand of micro-fabrication has increased tremendously
due to product miniaturization. CNC machines play a vital role to fabricate mini/micro
parts. CNC machines can work very fast and effectively while the command is given
by some G codes using a computer interface. The computer command controls all the
features of the machining operation like machining speed, feedrate, velocity and so on.
The modern researches about CNC machines usually focus on enhancing the
performance of the CNC machining system. Some researches focus on the delivery of
coolant at the place of machining (Robert Yellin, 2017). There are also a lot of
researches which focus on making the CNC platform capable of doing multiple
operation in the same platform. Some focus on using multiple axis (Gosselin, 2018)
while some other researches focus on incorporating and improving different types of
operations with CNC machining (Tomal et al., 2017).
In this research, a modular hexapod robot was used to carry out machining
operation. Hexapod robots are used in different engineering applications. Many
researchers have investigated kinematic and dynamic behaviour of the hexapods
(Woering, 2011). There are various ways to design the motion patterns of the links of
the hexapod (P. de Santos et al., 2007). Most literatures give wave gait examples of a
2
rectangle shaped robots(Kimura et al., 2006). In the current research, a suitable method
for the walking mechanism of the hexapod was considered based on the literature
review and more focus was given on the development of hexapod assisted micro/mini
machining technology.
1.2 PROBLEM STATEMENT AND ITS SIGNIFICANCE
In different manufacturing processes CNC machining plays an important role. It
provides a very useful way of automatically controlling different machining operations.
However, for miniature product machining (feature size in mm range) conventional
CNC machines are still used with significantly large work envelope. This is inefficient
in terms of space utilization. Generally, CNC machines are bulky and very difficult to
move from one place to another as they are not modular. As such, on site machining is
not possible with current CNC machines.
1.3 RESEARCH OBJECTIVES
This project represents in detail about design and development of a Hexapod machine
capable of machining for new engineering applications. The objectives of the project
are presented below:
1. To develop a Hexapod robot based machining platform for micromachining
operation on large work-piece.
2. To develop a control system for the Hexapod robot for precise machining
operation
3. To design and develop a Graphical User Interface (GUI) for controlling the
motion and machining parameters of the robotic machining platform
4. To evaluate the performance of the robot in terms of machining accuracy
3
1.4 RESEARCH METHODOLOGY
This research was carried out based on experimental design, development and control
implementation of the developed system. The following section describes methodology
for each objective of this proposed project.
1.4.1 Methodology for Objective 1
The mechanical design of the Hexapod was inspired from a previous design which
consists of 6 legs with three degree of freedom in each leg. So, the total degree of
freedom was 3(motor) X 6(legs) =18 DOF (Degrees of Freedom). The design of this
hexapod was inspired from “Phoenix” hexapod of Lynxmotion.com(“Lynxmotion").
This type of structure provided the platform ability to move over the work piece and do
machining operation. There was another servo attached in the front middle area of the
Hexapod which enabled, engage and disengage of the spindle motor. Skotch yoke
mechanism was used to transform the rotary motion of the servo into z axis motion. The
skotch yoke mechanism idea was followed from a CNC hexapod router. But detail
research data were not found (Denton Matt).
1.4.2 Methodology for Objective 2
The whole control system for the Hexapod was developed through using a controller,
circuitry and algorithm. SSC32u servo controller was used to control the position of
servos. To communicate with the servo driver a GUI was developed. Point to point
motion command could be given using the GUI within the workspace of 20mm x 20mm.
The hexapod could do machining while standing at one place locally and also while it
moves with moving its whole body and thus changing its global position.
4
1.4.3 Methodology for Objective 3
For controlling the Hexapod a GUI was developed using C# language. The Hexapod
robot’s various motions was given using the developed GUI. The GUI program helped
to find out the required amount of rotation of each motor to move the Hexapod to an
exact point where the machining is required. The GUI was capable of taking the input
in three ways. Manual data input, button controlled movement and multiple data input
by using text file. A compensation algorithm was adapted to reduce the positional error
of the robotic platform. More about this controlling is discussed in chapter 3.
1.4.4 Methodology for Objective 4
The working ability of the Hexapod was studied. The machining that the Hexapod could
do was checked by standard processes. Different operations was performed with the
Hexapod by varying different parameters of the operation. Its movements was also
checked to ensure that they are good enough and can correctly follow the given
commands. The positional accuracy was measured in terms of distance in mm. The
circularity and taperness was also measured. To find out the taperness, the following
formula was used, 𝜃 = 𝑡𝑎𝑛−1(𝐸𝑛𝑡𝑟𝑦 ℎ𝑜𝑙𝑒 − 𝐸𝑥𝑖𝑡 ℎ𝑜𝑙𝑒 𝑇ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠⁄ ). And the hole
circularity is measured by taking diameter from three places of the same hole and then
calculating their standard deviation. If the standard deviation is high, then it means the
hole circularity is less.
5
Figure 1.1 Complete Research Flow Chart
The complete research flow chart is shown in the Fig 1.1 above. From this flow chart,
the steps followed to do this research can be understood.
Development of the mechanical
structure
Development of hardware control
system
Design and development of the
Control System using GUI
Evaluation of the performance of
the system
Does performance
meet the
requirements?
No
Yes
Finish
Start
Use compensation algorithm
Literature review
Benchmarking with standard CNC
machine
Writing Thesis
6
1.5 RESEARCH SCOPE
In most researches, CNC machining and Hexapod robot had been usually two separate
themes. In the research of hexapod robots, machining operations like CNC machining
has not been thought of. Mostly the Hexapod robot research work focus on different
designs, models and movements. In some recent researches, CNC machining is done by
big size Hexapods (Tunc & Shaw, 2016). This mobile hexapod gives certain mobility
and ease of movement of the CNC machining tool. Still the machine is somewhat heavy
and bulky. This research can be thought of as the fusion of mini hexapod robots and
CNC machining. The size of the machine tool was small because of using mini size
Hexapods. Adjusting movement of the robot for rough terrain or obstacle was not
covered in this research.
1.6 THESIS ORGANIZATION
The thesis has been organized in 6 chapters which have highlighted the total research
work in details. The 6 chapters are described briefly as below.
Chapter 1: As described in the previous sections, this chapter provides a brief
product. The last section highlights the research scope of this study technology.
Chapter 2: The literature review starts with introducing different types of
Hexapods and different method of locomotion. Then, different configurations and
walking styles of hexapod robots are discussed. Existing mobile machines and existing
hexapod models are discussed as well.
Chapter 3: The design and development of the whole Hexapod based
machining system is discussed in this chapter. The mechanical development, required
7
stress and torque analysis, electrical components and their application, control
algorithm, GUI instruction all these topics are discussed in this chapter.
Chapter 4: The arrangements required for the experimental procedures are
discussed in this chapter. A wooden block was used as sacrificial material which gave
support and elevated the workpiece. And 3mm Perspex was used to test drilling. Dino-
lite was used for measuring accuracy.
Chapter 5: The data collected from the experiments were shown in this chapter.
Comparison were also shown among use of various parameters.
Chapter 6: The whole work discussed in this thesis is summarized in this
chapter. The shortcomings of this research work is highlighted and recommendations
are also included to give proper direction for future works that will further improve this
hybrid manufacturing system.
8
CHAPTER TWO
LITERATURE REVIEW
2.1 INTRODUCTION
Research about hexapod robots started approximately around late 80’s. Since it is not a
very old research topic, researchers started to create some movement sequences and
structure which can be used effectively as per requirement. Still, there are many research
work going on to optimize the functionality of hexapod robots. At the university of
Duisberg, the department of Mechanics started to develop a hexapod named Tarry I in
1992, which followed the structure of stick insect (Carausius morosus) (Buschmann.,
2000). Later on there were some research work which considered different movement
and structure of hexapod robots. Cockroach like structure was followed in a research in
1997 (Nelson et al., 1997). In the year 2000 some research works were done on a robot
called RHex by Uluq Saranli’, Martin Buehler and Daniel E. Koditschek’ (Koditschek
et al., 2000). In 2012 some work on a hexapod robot called “HITCR II” by Jie Zhao,
He Zhang, Yubin Liu, Jihong Yan, Xizhe Zang and Ziwei Zhou(Zhang et al., 2014) .
This robot was designed in a way so that it was capable of walking on an unstructured
surface. A hexapod robot which was smaller than 9 cm in terms of length, width and
height, was developed by Mayo Funatsu, Yushi Kawasaki, Soichiro Kawasaki and Koki
Kikuchi in 2014. This robot had claws which assisted it to climb concrete wall
(Funatsuat et al, 2014).
The first industrial robot which was commercially available, was made by the
father of industrial grade robotic arm, Joseph Engelberger. He along with his colleagues
designed the first autonomous mobile robots to be used in hospital. Later on there had