UNIVERSITI PUTRA MALAYSIA

DEVELOPMENT OF A SINGLE DEGREE OF FREEDOM HAPTIC SYSTEM HANDLE

KWA CHIN KOK.

FK 2004 39

DEVELOPMENT OF A SINGLE DEGREE OF FREEDOM HAPTIC SYSTEM

HANDLE

BY

KWA CHIN KOK

Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in Fulfillment of the Requirements for the Degree of Master of

Science

JANUARY 2004

DEDICATION

Specially dedicated to my family and friends.

Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfillment of the requirement for the degree of Master of Science

DEVELOPMENT OF A SINGLE DEGREE OF HAPTIC SYSTEM HANDLE

KWA CHIN KOK

January 2004

Chairman: lshak Ark, Ph.D.

Faculty: Engineering

Sense of touch is one of the most important senses for human. Human feels

and interacts with the environment through their sense of touch. This thesis

describes the design and development of a single degree of freedom handle

with force feedback. The interaction between the handle and the user is

achieved through the usage of a DC servomotor. The servomotor provides

the resistive force to the manipulator. To control the servomotor, electronics

circuit is constructed. The electronics circuit controls the force provided by

the motor by using the Pulse Width Modulation technique. A computer is

used to provide graphical interface to the user. The computer is also used to

control the force provided by the motor by sending data through its parallel

port to the controlling electronics circuit. At the end of the project, a single

degree of freedom handle has been constructed and its characteristics have

been tested. From the tests conducted, the system built managed to provide

resistive torque up to 1.6Nm

Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi keperluan untuk ljazah Master Sains

PEMBINAAN PENGAWAL DENGAN KUASA SUAP-BALIK BERKEBEBASANSATUDARJAH

Oleh

KWA CHIN KOK

Januari 2004

Pengerusi: lshak Aris, Ph.D.

Fakulti: Kejuruteraan

Deria sentuh merupakan salah satu deria yang penting kepada manusia.

Manusia berinteraksi dengan persekitaran melalui deria sentuh mereka.

Tesis ini menerangkan rekabentuk and pembinaan satu pengawal dengan

kuasa suap-balik berkebebasan satu darjah. lnteraksi antara penguna

dengan pengawal dicapai melalui penggunaan motor arus terus 24V. Kuasa

penentang oleh pengawal adalah diperoleh daripada motor ini. Untuk

mengawal motor ini, litar elektronik direka. Litar elektronik ini mengawal

kuasa yang dibekalkan oleh motor dengan menggunakan teknik modulasi

lebar denyut. Komputer digunakan untuk memberikan interaksi grafik kepada

penguna. Komputer juga digunakan untuk mengawal kuasa yang dibekalkan

oleh motor dengan menghantar data melalui pengkalan selarinya kepada litar

elektronik. Pada akhir projek, satu pengawal dengan kuasa suap-balik

berkebebasan satu darjah telah dibina dan ciri-cirinya diuji. Daripada ujian-

ujian yang telah dilakukan, sistem yang telah dibina berkeupayaan menjana

kuasa tentangan 1.6Nm telah dibina.

ACKNOWLEDGEMENTS

First and foremost, I would like to take this opportunity to express my deepest

gratitude to the people who have cherished and enriched my life in Universiti

Putra Malaysia with invaluable knowledge and experiences. These people

have made my life easier and happier throughout the completion of this

thesis.

My sincere appreciation to my supervisory committee chairman, Associate

Professor Dr. lshak Aris, Dr. Samsul Bahari and Dr. Mahmud Hasan for

helping me through the hard time. Their guidance and advice throughout the

project have been very inspiring and indispensable for the success of my

project.

A simple thank you to all my friends. Sincere thank you to Ng Kwan Ti for his

insightful and constructive criticism. My very best wishes for their success in

their future undertakings.

It is a pleasure to acknowledge my family. Their love and support have

always been my source of inspiration and aspiration.

Finally, I would like to also say thank you to all the Universiti Putra Malaysia's

staffs that have help me throughout these years. Without them, my project

will never be realized.

I certify that an Examination Committee met on 09 January 2004 to conduct the final examination of Kwa Chin Kok on his Master of Science thesis entitled "Development of a Single Degree of Freedom Haptic System Handle" in accordance with Universiti Pertanian Malaysia (Higher Degree) Act 1980 and Universiti Pertanian Malaysia (Higher Degree) Regulations 1981. The Committee recommends that the candidate be awarded the relevant degree. Members of the Examination Committee are as follows:

Napsiah Omar, Ph.D. Faculty of Engineering Universiti Putra Malaysia (Chairman)

lshak Ark, Ph.D. Faculty of Engineering Universiti Putra Malaysia (Member)

Samsul Bahari, Ph.D. Faculty of Engineering Universiti Putra Malaysia (Member)

Md. Mahmud Hasan, Ph.D. Faculty of Science Universiti Brunei Darusalam (Member)

ProfessorIDeputy Dean School of Graduate Studies Universiti Putra Malaysia

Date: 2 2 JUN 2004

This thesis submitted to the Senate of Universiti Putra Malaysia and has been accepted as fulfilment of the requirement for the degree of Master of Science. The members of the Supervisory Committee are as follows:

lshak Ark, Ph.D. Associate Professor Faculty of Engineering Universiti Putra Malaysia (Chairman)

Samsul Bahari, Ph.D. Faculty of Engineering Universiti Putra Malaysia (Member)

Md. Mahmud Hasan, Ph.D. Faculty of Science Universiti Brunei Darusalam (Member)

AlNl IDERIS, Ph.D. ProfessortDean School of Graduate Studies Universiti Putra Malaysia

Date: 2 0 JUL 2004

vii

DECLARATION

I hereby declare that the thesis is based on my original work except for quotations and citations which have been duly acknowledged. I also declare that it has not been previously of concurrently submitted for any degree at UPM or other institutions.

viii

LIST OF TABLES

Table

3.1

3.2

3.3

3.4

3.5

3.6

3.7

3.8

3.9

4.1

Signals of Optical Switches when Motor is Rotating

Direction Command from Microcontroller 2 to Microcontroller 1

User Defined Registers and Description

Routines in Textunit unit

Routines in MiceUnit unit

Newwindow object's window

Objects in CtrlUnit unit

MenuTool object's methods

Routines in Main Program

Relationship between torque and Level Displayed in the GUI

Page

33

35

37

46

49

52

54

55

59

78

LIST OF FIGURES

Figure

1 . I

3.1

3.2

3.3

3 -4

3.5

3.6

3.7

3.8

3.9

3.1

3.1 1 (a)

3.1 1(b)

3.12

3.1 3

3.14

3.15

3.16

3.17

3.18

3.19

3.20

3.21

3.22

3.23

3.24

4.1

4.2

4.3

System for Haptic Interaction with Computer Simulation

General Structure of the Proposed Project

Block Diagram of the Haptic System

Half of H-bridge Motor Driver Circuit

H-bridge Motor Driver Circuit

Collector Feedback lnverter Circuit

lnverter Circuit

Pulse Train Generation Circuit

Flowchart of Communication between the Microcontroller 1 and

the Computer

Flowchart of Pulse Train Generation

Optical Encoders Circuit and Disc Mounted on Motor's Spindle

Encoder Disc

Output Waveforms of Both Optical Switches

Position Reference and Direction Processing Circuit

Flowchart of Microcontroller 2 Interrupt Service Routine

Flowchart of Sending Position Reference Data to Computer

Electronics Circuit of Force-Feedback System

Mechanical Setup of the Haptic System

Mechanical Construction of the Haptic System

Overall Hardware System

Boxselected Method

Coordinates Convention Used in the Program

Flowchart of DrawRight Routine

Flowchart of DrawLeft Routine

Flowchart of Main Program

Experimental Setup Construction

Graph of Generated Voltage versus Speed

Graph of Ktlao versus Speed

Graph of No Load Current versus KJ,,

Page

Relationship between the Duty Cycle and No Load Current Consumption

Current Consumption of the System when Manipulator Stalled

Relationship of Duty Cycle with the Maximum Weight of the System

Relationship of Duty Cycle with the Torque Produced by the System

Password Window

User Name Window

Graphical User Interface Window

Abbreviation

AC

CAD

DC

EMF

GUI

JSF

LVDT

MIT

PCB

RVDT

LIST OF ABBREVIATIONS

Alternating Current

Computer Aided Design

Direct Current

Electromotive Force

Graphical User Interface

Joint Strike Fighter

Linear Variable Differential Transformer

Massachusetts Institute of Technology

Printed Circuit Board

Rotary Variable Differential Transformer

xii

TABLE OF CONTENTS

Page

DEDICATION ABSTRACT ABSTRAK ACKNOWLEDGEMENTS APPROVAL SHEETS DECLARATION FORM LlST OF TABLES LlST OF FIGURES LlST OF ABBREVIATIONS

CHAPTER

1 INTRODUCTION 1.1 Haptic System 1.2 Problem Statement 1.3 Objectives of the Project 1.4 Thesis Layout

2 LITERATURE REVIEW 2.1 Haptic Technology

2.1.1 Application in Virtual Reality 2.1.2 Application in Medical Field 2.1.3 Application in Manufacturing 2.1.4 Application in Aerospace

2.2 Reference on Other Single DOF Haptic System 2.3 Conclusion

3 METHODOLOGY 3.1 Introduction 3.2 Conceptual and Skeleton Structure of the Design 3.3 General Overview of the Haptic System 3.4 Hardware Design

3.4.1 Electronics Module 3.4.1.1 Motor Driver Circuit 3.4.1.2 Microcontroller 1 3.4.1.3 Microcontroller 2

3.4.2 Mechanical Hardware Design 3.5 Software Design

I I . . . Ill

iv v vi . . .

Vl l l

ix X

xii

3.5.1 Providing Text in Graphics Mode 3.5.2 Providing Mouse Support 3.5.3 Providing Multiple Windows Operation 3.5.4 Providing Object Controls 3.5.5 Providing User Interface

3.6 Experimental Setup

4 RESULTS AND DISCUSSIONS 4.1 Identification of DC Motor Parameters

4.1.1 Terminal Resistance, R 4.1.2 Back Electromotive Force Constant, Kb and Torque

Constant, Kt 4.1.3 Friction Terms Tf and D

4.2 Force Feedback lnterface Experimental Results 4.3 Computer lnterface

5 CONCLUSION AND SUGGESTION FOR FUTURE WORKS 5.1 Conclusion 5.2 Suggestions for Future Works

REFERENCES APPENDICES BIODATA OF THE AUTHOR

CHAPTER I

INTRODUCTION

1.1 Haptic System

The term haptics was derived from the Greek word haptikos, which brings the

meaning of "able to touch" [I]. This was first coined by the psychologists who

were studying active touch in the early part of the 2oth century.

Sense of touch has enabled human to feel the environment around them.

Simple everyday tasks such as brushing one's teeth, typing, writing, or

pressing a button would all become great difficulties to human without the

sense of touch.

Sense of touch is different from the sense of hearing as well as visual. This is

because in audio and graphics, the user is just receiving energy from the

environment. But in touch, the user is interacting, which means that the user

is exchanging energy with the environment.

Development in human-machine systems such as teleoperation and

interactive human-computer systems such as virtual reality has increased the

interest in haptics study. In virtual reality for example, besides audio and

graphical display, the user must also be able to feel, touch and manipulate

the virtual environments as it should be in the real environment, which can be

achieved through haptic display.

Figure 1.1 shows a block diagram for a haptic interface to a computer-

simulated environment. In this system, human will interact with the haptic

interface through motion. The motion signal from haptic interface will be

inputted to a computer simulation of a virtual environment. The computer will

computes the desired reaction forces back to the user through the haptic

interface.

I Human Operator Haptic Interface t

Force System Force Computer

Figure 1 .I: System for Haptic Interaction with Computer Simulation

1.2 Problem Statement

This thesis is intended to design a basic single degree of freedom haptic

interface system. The primary challenges to this effort are development of

haptic interface mechanisms, development of software simulations and the

communication between the software, the user and the haptic system. The

purpose of this thesis is to build the basic knowledge to the design of the

haptic interface system as foundation to future device design.

In the mechanical design, a force transmission system has to be designed

that will provide the force interaction between the user and the haptic system.

The design of the power transmission system will the primary objective in the

mechanical design in order to achieve the desirable torque.

In the electronics design, there are few things that have to be considered.

The type of motor driving circuit that has to be used and the method of

driving the motor, either using Pulse Width Modulation technique, or any

other methods that is more suitable for the circuit. Besides that, the selection

of communication protocol with the computer has to be put into

consideration.

In the software, the important part in the design is to consider the interaction

of the computer with the haptic system. The design of the Graphical User

Interface to display the position of the handle and the communication with the

haptic system will be given primary priorities.

The single degree of freedom haptic system handle can be used as a

foundation for future research in understanding haptic system. Amongst the

many applications that can be achieved by the proposed system is in arm

physiotherapy sessions. Conventional physiotherapy method is to do

exercise with various objects that will have different weights. By using this

system, together with the implementation of the computer system, the

doctors will have the flexibility to monitor and control the patients

physiotherapy sessions development.

Besides that, the system can be further developed into a teleoperation

system. The advent of the internet and more sophisticated digital gadgets, a

system that will allow a user in Europe to control or touch an object located in

Malaysia seems to be achievable and not intangible.

1.3 Objectives of the Project

The proposed system will have the following basic features:

The system should have a feedback to the user as though he or she is

interacting with the real world.

Under no load simulation, the user should have force-free control, which

means the user should be able to move the handle freely without feeling

any resistive force.

The handle should remain at one place when the operator stops

pushing it.

The objectives of the project are listed as follows.

1. Design of mechanical setup. This includes the design of the handle and

the power transmission from the motor to the handle.

2. Design of electronics circuitry. Electronics is used to control the torque

and direction of the force applied by the motor.

3. Design of graphical interface. Graphical interface is important for the

interaction between user and the system. Computer is used to control the

force and direction provided by the motor. Besides that, computer

provides the graphical presentation of the movement of handle.

gRPUSlAKAAH SULTAN A W L UNIVW3tTl mRA W Y O A

1.4 Thesis Layout

Chapters 1 and 2 are introductory. Chapter 1 presents objectives and the

basic construction of this project. Chapter 2 reviews the on-going and

available research on haptics technology. Besides that Chapter 2 also

presents various types of mechanisms and parts that are available that could

be used in the design. Chapter 3 gives detail design methodology of the

proposed project. In Chapter 4, results and discussion of experiment and

tests will be highlighted. The last chapter, Chapter 5, summarises the project

and gives further recommendation to continue the project.

CHAPTER 2

LITERATURE REVIEW

2.1 Haptic Technology

A haptic system can be defined as a force feedback interface that lets the

user touches, feels and manipulates the virtual environments. In the future

there will be more and more surprising and eye-opening inventions emerging,

as the potential of haptic application is still vast.

2.1 .I Application in Virtual Reality

The most obvious application of haptics is in the computer applications.

Perhaps the earliest haptics devices for computers were those meant for the

Braille readers. These devices enable the blind user to read the text on the

computer screen by moving their finger along a line of metal pins that form a

Braille representation of the text displayed on the screen.

Playing computer games will be more engaging by touch interactions. This

objective is achieved with the emergence of the force-feedback joysticks and

force-feedback mouse [2]. Immersion began licensing its Touchsense

software in 1995 for usage in joysticks and steering wheels. This technology

is quickly absorbed by the game producers such as Microsoft, Electronic

Arts, Acclaim and LucasArts in their game applications. Black & White has

won major awards including the Best Show at E3, the world largest video

games trade gathering. The game that was created by Black & White, "god

simulator" allows the game player to feel the fish nibbling, heartbeat of the

worshippers, the tug of uprooting a tree and the pulsing power of casting a

spell 131. The Immersion's tactile feedback technology also works well with

the Windows 98 compatible software. Hence it will automatically adds touch

feedback to many of the basic Windows controls, such as the icons, menus

and buttons. Besides that, it will also add sense of touch to internet

application such as the hyperlinks, check boxes and the menus.

In December year 2000, Logitech, a renowned mouse maker, began offering

its latest mouse technology that made use of haptic technology, the

WingMan. Working alongside with Immersion's software, WingMan has

microprocessor and motors that will vibrate, recoil, stiffen and loosen the

mouse accordingly. Besides that, the latest version of Logitech's mouse,

iFeel would enable user to feel the tactile sensations linked to the features on

the site [4]. This mouse made use of the Inertial Harmonic Drive. The

mismatch number of tooth of its meshed gears will generate the vibration and

motion needed to provide the haptics sensation.

As pointed out by by the author in [5], learning 3-D modeling packages has

always been time consuming and torturous. With the emergence of the a

device called FreeForm Phantom's .3-D modeling system by SensAble

Technologies, the learning curve of the 3-D modeling has been greatly

reduced. One of the best examples of using the haptics devices in 3-D

modeling is in the movie, Chicken Run.

A group of researchers in MIT is developing the World Wide Web with the

touch of haptic [6]. Using Phantom haptic interface, the user will be asked to

differentiate the stiffness of two different coils across the web and send their

responses via e-mail. They are trying to embed the haptics into Virtual

Reality Modelling Language (VRML) through its extension mechanism.

Another group of researchers, led by Professor Hardwick, foresees the

application of VRML and haptics in helping the blind to 'feel' over the net [7].

Using the Immersion's Impulse 3000 force-feedback probe and the VRML

language, they are able to provide some sense of touch over the internet.

2.1.2 Application in Medical Field

The usage of haptic technology has greatly help the doctors to have the

better tools in order to reduce the risk when performing surgery procedures

[8, 9, 10, 111. In endosurgery procedures, there are great amount of loss in

the sense of touch compared to the open surgery. This is due to the

mechanical design and construction of the endoscopic devices that will

create a lot of friction, backlash and stiffness in these long devices. In the

papers presented by a group of researchers (8, 91, they have presented on a

system named 'Computerized Force Feedback Endoscopic Surgical Grasper'

was developed by using the computer control and haptic interface. The

system developed has been able to differentiate the difference between the

live tissue and the artificial tissue. The application of haptic in the endoscopic

system, as presented in these papers, has proved that it will greatly help the

doctors in performing their surgical procedures compared to the normal

conventional endoscopic graspers by restoring the lost of the sense of touch.

Application of haptic in the endosurgery will restore the sensation of touch

that is much needed by the doctors during the surgery procedures, especially

in handling delicate and soft tissue. Hence, the use of haptics endoscopic

grasper has greatly reduces the trauma to the tissues, reduces the pain of

patient, and increases the rate of recovery of the patient. In a very well

written journal written by Stoianovici [lo], the author has pointed out a few

robots and applications that utilize haptic technology. For example, the

daVinci system developed by Intuitive Surgical Inc. that perform totally

endoscopic coronary artery bypass procedures on a beating heart, and the

Zeus system developed by Computer Motion, Inc. that also enable the

surgeon to operate the system from the remotely located haptic interface.

Doctors or medical students rarely have a chance to practice their technique

before performing any surgery on a live patient. With the emergence of

simulation programmes that have incorporated the haptics technology,

doctors and medical students will be able to do training before performing

any surgical operation [8, 11, 12, 13, 14, 15, 171. Paper written by lssenber

[I41 has quoted the Medical School Objectives Project, sponsored by the

Association of American Medical Colleges, stated in their Medical Informatics

Objectives that the medical students should be proficient in various

computer-based instructional tools, including the electronic tutorials and

patient simulations. There are many medical training simulators available in

the market nowadays. One of the most popular simulators is CathSim, the

product of Immersion Medical [13]. This simulator allows the medical

students to get a feel for the basics of snipping a tissue sample from inside a

lung or inspecting a colon without touching a patient. There are also Harvey,

the Cardiology Patient Simulator [14], laparoscopic surgical skill simulator

[15], lowa Dental Surgical Simulator developed by colleges of Dentistry and

Engineering of University of lowa [16], and endoscopic sinus surgery

simulation [I 71.

For the visually impaired people, they 'see' the world mostly by touching.

VisuAide [I81 has shown how the MouseCAT, a two-button mouse that

provide haptic sensation, helped the blind people to feel their way through

the computer. The paper written by Gunnar Jansson [I91 has emphasised

how the haptic could help the blind by improving their recognition ability

through their sense of touch.

In the future, haptic may also help restoring the feel of touch of the

prosthetics from their artificial limbs and arms [I]. One day in the future, the

doctors and patients will not have to meet. The patient will consult the doctor

through Internet and the doctor could perform surgery on the patient even

they are parted by the Pacific Ocean. This is what Grobkopf and friends

foresee (201.

2.1.3 Application in Manufacturing

Haptic is widely applied in product designing. The application of haptic device

in the product design, prototyping and testing will greatly reduce the time and

cost of manufacturing and designing [21, 221.