MECHATRONIC DESIGN AND DEVELOPMENT OF A ROBOTIC ARM

ZULKIFLI BIN MOHAMED

UNIVERSITI TEKNOLOGI MALAYSIA

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To my beloved mak, abah and family, for your love and continuous support.

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ACKNOWLEDGEMENT

First and foremost, I would like to thank my supervisor Prof. Madya Dr.

Musa bin Mailah for his guidance, critics and advice in completing this project.

Without his supervision it would be impossible to accomplish this project.

I would also like to thank Mr. Yeong Che Fai from FKE, Mr. Phang Che Yi

from Cytron and En. Mohamed Akmal Baharin from System and Control Laboratory,

which have guided me on the design and mechatronic part of the project. Also to the

members of Faculty of Mechanical Engineering, Universiti Teknologi Malaysia and

others who have provided assistance towards completing this work.

Then, I would like to thank my parents for their never ending support and

love. Without their continuous support and ‘doa’, I will not be here today. I am also

indebted to my family members and friends, especially Zaki, Yusri, Nizam and

Azmi, for their advice and support.

Finally, this appreciation is for Universiti Teknologi MARA for sponsoring

my study from the beginning to the end.

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ABSTRACT

In this study a small scale robot arm was developed based on the actual rig.

The parameter from the model is used in the simulation process. Simulation

algorithm was developed and implemented within the Simulink environment. The

analysis is done by the implementation of different type of control scheme and

disturbances to the robot arm. The results from the simulation are used and compared

with experimental results. It is proven that a robot arm having a PD-AFC scheme is

very robust and stable compare to PD control.

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ABSTRAK

Dalam kajian ini, sebuah lengan robot berskala kecil telah dibina berdasarkan

lengan robot yang asal. Data – data dan ukuran dari model robot ini digunakan di

dalam proses simulasi. Algoritma simulasi dibangunkan dan simulasi dijalankan di

dalam Simulink. Analisis dijalankan dengan mengaplikasikan skema kawalan dan

gangguan yang berbeza kepada lengan robot. Hasil analisis dan kajian dari simulasi

dibandingkan dengan keputusan secara praktikal. Terbukti bahawa lengan robot yang

menggunakan skema PD-AFC adalah lebih stabil berbanding dengan kawalan PD

sahaja.

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TABLE OF CONTENTS

CHAPTER TITLE PAGE

1

TITLE

DECLARATION

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

ABSTRAK

TABLE OF CONTENTS

LIST OF TABLES

LIST OF FIGURES

LIST OF SYMBOLS

LIST OF ABBREVIATIONS

LIST OF APPENDICES

INTRODUCTION

1.1 Introduction

1.2 Research Objectives

1.3 Research Scopes

1.4 Research Methodology and Strategy

1.5 Expected Results

1.6 Organization of Thesis

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2 THEORETICAL AND LITERATURE REVIEW

2.1 Introduction

2.2 Kinematics and Dynamics of Robot Arm

2.2.1 Basic Dynamic Equation

2.2.2 Newton-Euler Formulation

2.3 Robot Control

2.3.1 Position Control

2.3.2 Speed Control

2.3.3 Acceleration Control

2.4 Control Scheme

2.4.1 Classical Control

2.4.2 Active Force Control (AFC)

2.5 Disturbance Model

2.6 Related Software

2.7 Conclusion

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SIMULATION

3.1 Introduction

3.2 Parameters of Robot Arm

3.3 Simulation

3.3.1 Prescribe Trajectory

3.3.2 Simulation Condition

3.4 Conclusion

DEVELOPMENT OF ROBOTIC ARM

4.1 Introduction

4.2 Main Components

4.2.1 Arm Design

4.2.2 Hobby Servo Motor

4.2.3 PIC Start-up Kit – SK40A

4.2.4 Microcontroller

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4.2.5 Potentiometer

4.2.6 Bootloader

4.3 Programming

4.3.1 Open Loop System

4.3.2 Closed Loop System (PD Control)

4.3.3 Signal Conversion

4.4 Summary of the Development Process

4.5 Conclusion

RESULTS AND DISCUSSION

5.1 Introduction

5.2 Simulation Results

5.2.1 No Disturbance

5.2.2 Constant Disturbance Torque at Joints

5.2.3 Spring Force at Link 2

5.2.4 Different Payload

5.3 Experimental Results

5.4 Conclusion

CONCLUSIONS

6.1 Conclusion

6.2 Recommendations

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REFERENCES

Appendices A – D

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LIST OF TABLES

TABLE NO. TITLE PAGE

3.1 Properties of the arm 25

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LIST OF FIGURES

FIGURE NO. TITLE PAGE

1.1

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

2.10

3.1

3.2

3.3

3.4

3.5

3.6

4.1

4.2

4.3

4.4

4.5

4.6

Project’s flowchart

Two-link robot arm

Isometric view of two-link robot arm

Free body diagram of link i

Simulink block diagram of robot dynamics

Position control of robot arm

Speed control of robot arm

Acceleration control of robot arm

An AFC block diagram

Simulink block diagram of PD-AFC scheme

Simulink block diagram of disturbance model

Robot Arm

Simulink block diagram of PD-AFC scheme

Simulink block diagram of robot dynamics

Simulink block diagram of disturbance model

Simulink block diagram of AFC loop

Prescribed trajectory

Robot arm design

Complete experimental setup

Hobby servo motor

Inside a servo motor

Duration of pulse

a) PIC start-up kit (SK40A) b) SK40A layout

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4.7

4.8

4.9

4.10

4.11

4.12

4.13

4.14

4.15

4.16

4.17

4.18

4.19

5.1

5.2

5.3

5.4

5.5

5.6

5.7

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5.9

5.10

5.11

5.12

PIC 16F877A microcontroller

PIC 16F877A pin layout

10K Potentiometer

HyperTerminal for bootloader

a) Laptop programmer (Z000L) b) Desktop programmer

(L4128D)

Main routine flowchart

Interrupt service routine

Open loop system

Arm position

Closed loop system (PD control)

A/D block diagram of PIC 16F877A microcontroller

a) Original arm design b) Small scale arm

Potentiometer attachment

Position of joints, spring and payload

No Disturbance a) PD control b) PD-AFC control

Constant torque at both joints a) PD control b) PD-AFC

Constant torque at joints 1 a) PD control b) PD-AFC

Constant torque at joints 2 a) PD control b) PD-AFC

Spring force at link 2 (200 N/m) a) PD control b) PD-

AFC

Spring force at link 2 (400 N/m) a) PD control b) PD-

AFC

Payload position

Payload of 0.5 kg a) PD control b) PD-AFC

Payload of 2.5 kg a) PD control b) PD-AFC

Prescribed trajectory of arm (experimental)

Desired position of servo motor

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LIST OF SYMBOLS

l - length of link

θ - joint angle of link

Τ - joint torque

ciivm &− - inertial force of link

ρacrylic - mass density per unit area for acrylic

m - mass of link

civ& - linear acceleration

g - gravitational acceleration

iiN ,1− - rotational motion of the arm

iiI ω - gyroscopic torque

f - force

Kp - proportional constant

Ki - integral constant

KD - derivatives constant

a - acceleration

mmot - mass of motor

h - thickness of link

v - volume of link

ktn - motor torque

I - moment of inertia

a - width of plate

b - length of plate

k - spring stiffness

Vcut - end point linear velocity,

D(t) - desired position

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Y(t) - measured position

E(t) - error

C(t) - controller response

E(n) - current error

E(n-1) - previous error

T(s) - sampling period

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LIST OF ABBREVIATIONS

P Proportional

I Integral

D Derivative

PID Proportional-Integral-Derivative

PD Proportional-Derivative

AFC Active Force Control

PD-AFC Proportional-Derivative-Active Force Control

RR Rotation-Rotation

AFCAFL Active Force Control and Fuzzy Logic

AFCANN Active Force Control and Neural Network

ALCAIL Active Force Control and Iterative Learning

AFCAGA Active Force Control and Genetic Algorithm

IDE Integrated Development Environment

PC Personal Computer

PCM Pulse Coded Modulation

PWM Pulse Width Modulation

I/O Input/Output

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LIST OF APPENDICES

APPENDIX TITLE PAGE

A1

A2

A3

B

C1

C2

C3

C4

C5

C6

D1

D2

Simulation data

Part of AFC simulation function

AFC Animation function

Program source code for robot arm

Technical drawing of link 1

Technical drawing of link 2

Technical drawing of base plate

Technical drawing of servo motor attachment

Technical drawing of potentiometer holder

Technical drawing of robot arm

PIC 16F877A data sheets

Schematic diagram of SK40A

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CHAPTER 1

INTRODUCTION

1.1 Introduction

This project is basically the continuation of previous research with some

modification and the use of different approaches. Previously, the focuses are on the

interfacing and control of a single link arm (Soong, 2001), experimental aspect of

interfacing and experimental aspects of single link arm (Goh, 2003) and the

implementation of Active Force Control (AFC) to a two-link robot arm (Pitowarno,

2002).

A robust and stable performance of a robot arm is very important as it deals

with working environment and disturbances. For example, in manufacturing, process

such as welding, cutting and spraying demands a highly robust and stable system.

Study on kinematics (Lee, 1983), static, dynamics (Lee, 1983), robot control scheme

(Astrom, 1995) and trajectory planning (Taylor, 1979) are very important, and there

are a lot more consideration needs to be considered in robot analysis. These factors

are important in order to have high quality product.

Many robot control methods had been introduced such as Proportional-

Integral-Derivative (PID) control, (Astrom, 1995), Adaptive Control, (Petros

Ioannou, 1991), Hybrid Control, Intelligent Control and AFC (Musa, 1998).

PID control is the most widely used control scheme. It is very robust and

stable for a relatively low speed and very little disturbance robot operation. The

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combination of the controller depends on the needs of the system. It can be

Proportional alone or, the combination of Proportional with Integral (PI),

Proportional with Derivative (PD) or PID control.

Nowadays, most robot system will have these classical controls and it is

being upgraded with the implementation and combination with modern type of

control scheme such as, Active Force Control, Intelligent Control, Adaptive Control

and Hybrid Control. These control scheme will overcome the problem arise in PID

control and produce more stable and robust system. Therefore, the existence of

internal or external disturbance can be compensated.

1.2 Research Objectives

The objectives of the research are:

i. To model and simulate a robot arm with different control schemes and

operating conditions.

ii. To develop a physical robot arm and use a microcontroller as the

driver.

1.3 Research Scopes

The scopes of this project are:

• Simulation using two different control schemes and operating conditions.

• Development of small scale rig.

• Make use or PIC Microcontroller as the main component of the system.

• Development of an open loop system.

• Improving the system by upgrading it to a closed loop system.

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• Development of the program both, for open and closed loop system.

• Test the rig.

1.4 Research Methodology and Strategy

The research methodology of the project can be described as follows:

• Literature review on robot areas, control scheme, microcontroller,

software and hardware.

• Study on existing rig, measure and obtain all the parameters needed in

order to design a small scale rig (length of link 1 and link 2, density, ρ of

acrylic, mass of motor 1 and 2 and mass of link 1 and link 2).

• Study on PIC Microcontroller (set up, advantages and the specification).

• Study on the software in order to do simulation and testing (MATLAB

6.5, Simulink 5.0, MPLAB IDE 7.0, PiCC Lite 8.02 and IC Prog).

• Study on control scheme and identify the problem and other related issues

(PD Control and AFC).

• Test the robustness and stability of the system by introducing different

type of disturbances (simulation).

• Make use of microcontroller which acts as the driver, controller and

analogue to digital converter.

• Perform experiment, compare, analyze and discuss the results.

This project was carried out within two semesters. The flowchart of the

project is shown in Figure 1.1:

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Study on Existing Rig, Control Theory, Electronics, System Modeling, Microcontroller and Simulation

Literature Review (Books, Thesis, Journal & Papers)

Study on Software (MATLAB 6.5, Simulink 5.0, MPLAB IDE, PiCC

Lite and ICProg)

Design of Small Scale Robotic Arm (Design, Fabrication and Assembly)

Simulate New Parameters, Programming and Testing

Apply Control Strategy to Robot Arm

Perform Experiment, Test and Evaluation

Analysis and Discussion

Figure 1.1: Project’s flowchart

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1.5 Expected Results

This project produces results that show the stability and robustness of the

proposed control scheme on a small scale two degree of freedom rigid robot arm.

1.6 Organization of Thesis

This report is basically divided into six main chapters. In Chapter 1, the

general idea of the project is stated. Introduction, project scope, methodology and

expected results are described in this chapter. Chapter 2 describes the fundamentals

of robot, dynamic analysis of robot arm, control scheme and other related topics.

Chapter 3 describes the simulation process with different operating conditions.

Chapter 4 gives the development of the robot arm and it includes design, fabrication

and programming. Chapter 5 presents the simulations and experimental results. The

final chapter (Chapter 6) describes the conclusions and recommendations of the

project.