A thesis submitted in fulfilment of the requirement for the degree of Master of Science

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ACTIVE VIBRATION ISOLATION BY USING VOICE COIL ACTUATOR FOR FREE SPACE OPTIC

COMMUNICATION

BY

SYAZWANI AB. RAHIM

A thesis submitted in fulfilment of the requirement for the degree of Master of Science

(Mechatronics Engineering)

Kulliyyah of Engineering

International Islamic University Malaysia

MARCH 2014

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ABSTRACT

In Free Space Optic (FSO) communication, the alignment between transmitter and receiver telescope is very important. The line of sight (LOS) of their optics must be aligned during the entire communication session. This is crucial in long distance data transmission. One of the factors that cause misalignment is vibration, either at the transmitter or the receiver. In this thesis, active vibration isolation (AVI) system which is able to actively isolate FSO devices from low frequency vibration from the ground is designed and developed. The main goal is to suppress vibration from the top plate of the system where the telescope of FSO system is mounted. A mathematical model of the isolator is derived and the prototype model of the AVI system is designed in SolidWorks. This prototype model is integrated with LabVIEW software to perform virtual prototyping in order to analyze the behavior of the system before the real prototype is developed. Controllers are designed and some simulation studies are performed in MATLAB for this AVI system. Then the real prototype is developed according to the design. An imbalance mass system is used as exciter of the system.

Furthermore for cost saving factor, voice coil actuator which is modified from conventional loudspeaker is used as actuator of the system. Gain Feedback controller and LQR controller are implemented by using LabVIEW. The time domain and frequency domain analysis are done to analyze the performance of the active vibration isolation system with excitation frequency in a range of 0 Hz to 20 Hz. For system with excitation frequency 6 Hz, the reduction of displacement for gain feedback controller and LQR controller are 30.78 % and 93.56 % respectively while for the system with excitation frequency 12 Hz, the reduction of displacement is 30.86 % and 86.02 % for gain feedback controller and LQR controller respectively. The reduction of displacement of the system with excitation frequency 18 Hz for gain feedback controller and LQR controller are 61.23 % and 90.04 % respectively. According to experimental and simulation results, we can conclude that both controllers manage to suppress vibration at low frequency. LQR controller shows a better performance compared to gain feedback controller.

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iii Free

Space Optic Communication (FSO) Line of Sight (LOS)

(AVI) Active Vibration Isolation

(FSO)

(AVI) SolidWorks

LabVIEW

MATLAB an imbalance mass

system Gain

Feedback Controller Linear-Quadratic Regulator(LQR)

Controller LabVIEW

Gain Feedback Controller

LQR

Gain Feedback Controller LQR

LQR

Gain Feedback Controller

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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).

………...…………

Asan Gani Abdul Muthalif 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).

………...…….…

Nahrul Khair Alang Md. Rashid Internal Examiner

………...………

Jawaid Iqbal Inayat Hussain 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 (Mechatronicss Engineering).

..………...…

Md. Raisuddin Khan

Head, Department of Mechatronics 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).

………...………

Md Noor Bin Salleh

Dean, Kulliyyah of Engineering

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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.

Syazwani Binti Ab. Rahim

Signature………..…… Date………..

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vi To:

My beloved parent and family

INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA

DECLARATION OF COPYRIGHT AND AFFIRMATION OF FAIR USE OF UNPUBLISHED RESEARCH

ACTIVE VIBRATION ISOLATION BY USING VOICE COIL ACTUATOR FOR FREE SPACE OPTIC COMMUNICATION

I hereby affirm that The International Islamic University Malaysia (IIUM) holds all rights in the copyright of this Work and henceforth any reproduction or use in any form or by means whatsoever is prohibited without the written consent of IIUM. No part of this unpublished research may be reproduced, stored in a retrieval system, or transmitted, in any form or by means, electronic, mechanical, photocopying, recording or otherwise without prior written permission of copyright holder.

Affirmed by Syazwani Binti Ab. Rahim.

……… ………

Signature Date

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vii To:

My beloved parent and family

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ACKNOWLEDGEMENTS

Alhamdulillah. Praise be to Allah the Almighty, only with His will I am able to complete my thesis. First and foremost, I would like to convey my warmest gratitude to my supervisor, Dr. Asan Gani Abdul Muthalif for his guidance, generous contribution of knowledge and experience, valuable comments and encouragement from the start until the end of my study. A special thank also to my co supervisor Dr.

Md. Raisuddin Khan for his useful comments. My deepest appreciation goes to Sr.

Khairiah Kamilah Turahim for her assistance and support. She helped me a lot in developing the hardware and shared idea and knowledge throughout completing this project.

Many thanks to my friends and fellow researchers from MIMOS-IIUM Lab and Intelligent Mechatronics Research Unit especially to Zalifah Ramli, Aina Mardhiyyah Mohd Ghazali, Norhanis Aida Mohd Noor, Nur Haedzerin Mohd Nor, Noor Asyikin Hazam, Nurul Izzati Samsudin, Mdm. Suriza Ahmad Zabidi, Ismail Ladipo and Mohd.

Nor Fakhzan. I am also thankful to lab technician, Br. Shahlan Bin Dalil, Br.

Muhamad Shaiful Bin Khamis @ Wahab and Br. Sanadi Bin Subhi for their help, support and permission to use different laboratory instruments.

I would like to express my gratitude to my parents and family members who always had been there beside me to give encouragement, enthusiasm, understanding and prayer. A special thanks also to the person who always give me moral support to finish this project.

Finally, a great thank you to everyone who was important to the successful realization of this thesis, and I apologize that I could not mention the names personally one by one.

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LIST OF TABLES

Table No. Page No.

1.1 Common sources of vibration (www.fabreeka.com) 5 2.1 Advantages and disadvantages of piezoelectric, pneumatic and 20

voice coil actuators.

2.2 Meta analysis of related works 26

3.1 Parameters for simulation study 37

4.1 Summary of performance 48

4.2 Trends of result 49

4.3 Summary of performance characteristics of the system 51

4.4 Summary of results for frequency of 6 Hz 56

6.1 Materials and dimensions 70

6.2 Characteristics of the spring. 73

6.3 Specifications of Rinover RM-LY-230 linear actuator 78 6.4 Specifications of Caliber CW-666 Speaker 83

6.5 Specifications of Ezone Power Planet Amplifier 85

6.6 Components for experimental setup 86

7.1 Components and equipments used for calibration of voice coil actuator 91 7.2 Summary of results for excitation frequency of 6 Hz 109 7.3 Summary of results for excitation frequency of 12 Hz 109 7.4 Summary of results for excitation frequency of 18 Hz 110

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7.5 Comparison between simulation and experimental result of LQR 112 controller

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LIST OF FIGURES

Figure No

.

^{Page No.}

1.1 Schematic structure of FSO system 2

1.2 The factors that contribute to misalignment of the laser beam. 3

1.3 Proposed active vibration isolation system 6

1.4 Overall methodology flowchart 9

2.1 Simple models showing the basic elements in different types of vibration isolation systems: (a) passive, (b) active, and (c) semi-active system

15

3.1 (a) Three dimensional model of prototype model, (b) Schematic diagram of the active vibration isolation system

33

3.2 Free body diagram 33

3.3 Schematic diagram of active vibration isolation system with displacement and velocity feedback control.

38

3.4 Bode Diagram of displacement of the top plate for various values of hd 40 3.5 Bode diagram of displacement of the top plate for =0 and various

values of

42

3.6 Bode diagram of displacement of the top plate for =500 and various values of

42

3.7 Bode diagram of displacement of the top plate for =5000 and various values of

43

4.1 Step response with various value of R 47

4.2 Graph of step response (a) without controller and (b) with LQR controller.

50

4.3 Response of active vibration isolation with LQR controller under an excitation of 6 Hz, (a) time domain; (b) frequency domain

53

54

4.5 Response of active vibration isolation with LQR controller under an 55

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excitation of 18 Hz, (a) time domain; (b) frequency domain

5.1 3D CAD model of active vibration isolator test rig in SolidWorks 62

5.2 NI LabVIEW project explorer window 63

5.3 NI LabVIEW vi (front panel and block diagram) to perform a contour move

64

5.4 Contour move points used to excite the system. 64

5.5 Integration between LabVIEW and SolidWorks. 65

5.6 Output of contour movement on excitation plate 66

5.7 Output of contour movement on top plate, 66

6.1 Main frame of active vibration isolation system. 69

6.2 Aluminum plate (0.3 m x 0.3 m x 0.015 m) 70

6.3 Dimension of holes and aluminum plate 71

6.4 Stainless steel rod 71

6.5 (a) Custom made compression spring, (b) Detailed drawing of a compression spring.

72

6.6 LMF20UU flange linear ball bearing. 74

6.7 Motor with lead screw 75

6.8 Electric circuit 75

6.9 Schematic diagram of pulley and belt 76

6.10 Rinover RM-LY-230 linear actuator was tested on the system. 78

6.11 Dongling vibration shaker. 79

6.12 (a) Schematic diagram, (b) Real prototype of imbalance mass 80 6.13 Accelerometer (PCB Piezotronics (352C33 125310)) 82 6.14 Modified loudspeaker (a) Caliber CW-666 speaker, (b) cross section of

modified loudspeaker.

83

6.15 (a) National Instrument USB 4431. (b) National Instrument USB 6216 84

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6.16 Ezone Power Planet Amplifier 85

6.17 (a) Test rig. (b) Experimental setup 87

6.18 Schematic diagram of experimental setup 87

7.1 Schematic diagram of test rig for calibration of voice coil actuator 91 7.2 LabVIEW block diagram for calibration of voice coil actuator

(loudspeaker)

93

7.3 Graph of relationship between voltage and force for the voice coil actuator

94

7.4 Programming flowchart of gain feedback controller 95 7.5 LabVIEW block diagram for gain feedback controller 97 7.6 LabVIEW block diagram to obtain optimal gain matrix, k. 98

7.7 Programming flowchart of LQR controller 99

7.8 LabVIEW block diagram for LQR controller 101

7.9 Response of active vibration isolation with gain feedback controller under an excitation of 6 Hz, (a) time domain; (b) frequency domain

103

104

105

106

107

108

7.15 Summary of performance for frequency domain analysis 111

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LIST OF ABBREVIATIONS

DOF Degree-of-Freedom

3D Three Dimensions

ADC Analog to Digital Converter

ANSI American National Standards Institute

ARE Algebraic Ricatti Equation

AVI Active Vibration Isolation

BER Bit Error Rate

BNC Bayonet Neill–Concelman

CAD Computer Aided Design

DAC Digital to Analog Converter

DAQ Data Acquisition

DC Direct Current

EMF Electromagnetic Field

FSO Free Space Optic

HIFI High Fidelity

IEPE Integrated Electronics Piezo Electric

IIR Infinite Impulse Response

IIUM International Islamic University Malaysia

IR Infrared

LabVIEW Laboratory Virtual Instrument Engineering Workbench

LOS Line-of-Sight

LQR Linear Quadratic Regulator

LQG Linear Quadratic Gaussian

LMS Least Mean Squares

LTI Linear time invariant

MATLAB Matrix Laboratory

MIMO Multiple Input Multiple Output

NI National Instruments

PID Proportional-Integral-Derivative

PO Percent Overshoot

RF Radio Frequency

USB Universal Serial Bus

VCA Voice coil actuator

VI Virtual Instruments

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LIST OF SYMBOLS

A system matrix

B input matrix

C output matrix

c damping of spring

D feed forward matrix

inner diameter

outer diameter

d wire diameter

F force

force exerted by actuator

G shear modulus

g gravity

displacement feedback gain velocity feedback gain

I current flowing through the coil

J performance index for the optimal controller design

k stiffness of spring

L length of one coil winding

l free length of spring

m mass

N total numbers of coil windings

n number of active coil of spring

PO percent overshoot

Q weighting matrices for state variables

R Weighting matrices for input variables

r radius of the pulley

T torque of motor

rise time settling time

ω angular frequency

x displacement

velocity

acceleration

displacement of ground vibration

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CHAPTER ONE INTRODUCTION

1.0 BACKGROUND

For a long time, radio frequency (RF) network has become the main medium for wireless communication. However it is not sufficient for high speed data transmission anymore since the spectrum has become congested (Lin, 2001). So the optical frequency network is an alternative way to overcome this problem. There are two types of optical frequency network which are fiber optic and free space optic. This method uses light as the medium for data transmission either through the optical fiber or the air.

The technology of free space optic (FSO) communication is developing rapidly. It is a promising medium network in wireless technology. FSO is an optical communication technology that transmits data from one point to another point by using light through the air (Kadir, 2011). It only can work if the line of sight is clear. FSO system can reach over distances of several meters to kilometers. Usually the transmitter and receiver are mounted on the rooftop or behind the window in order to get a clear line of sight (Hua, 2007).

The FSO communication system has many advantages. It does not require licensing since infrared (IR) wavelength is used. This IR has similar transmission bandwidth capabilities with a fiber optic system with the frequencies of the order of hundreds of terahertz (Bloom, 2003). FSO is also very cost effective. The work of construction is not needed to dig the road in order to apply this method. Moreover it provides very high data rates and easy to be installed since the equipment is small, light

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and compact (Arnon, 2003). The FSO communication link is more secure than RF links. It is very difficult to intercept point-to-point data transmission (Davis, 2003).

FSO link consists of optical transmitter and receiver which are accurately aligned to each other with a clear line-of-sight. At both transmitter and receiver is a telescope. A process of electric-to-optic at the transmitter generates a laser beam.

Then the laser source from transmitter telescope is expanded and directed to the receiver telescope. After propagation through the atmosphere, the receiver telescope collects it, optically filters and concentrates onto the focal plane detector. Lastly a reverse process of optic-to-electric converts back the signal into an electric current (Manor, 2003). Figure 1.1 shows the schematic structure of FSO system.

Figure 1.1: Schematic structure of FSO system (Manor, 2003).

In FSO system, the alignment of transmitter and receiver of telescope is crucial in transferring data. The line of sight of their optics must be aligned during the entire period of communication. However due to the long distance between the transmitter and the receiver, it is difficult to maintain their alignment. This will disturb the process of data transmission. There are several factors that contribute to this problem such as

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fog, physical obstructions, absorption, scattering, scintillation and building sway (Lin, 2001). Figure 1.2 shows the factors that contribute to misalignment of the laser beam.

Figure 1.2: The factors that contribute to misalignment of the laser beam.

Fog contributes a major effect to the misalignment of FSO. It is composed of water droplets. Even though its diameter is only a few hundred microns but it manages to modify characteristics of light or completely block the passage of light through a combination of scattering, absorption and reflection (Kher, 2006). On the other hand, the physical obstruction can be caused by flying bird, bugs, construction crane, and tree limbs. However this interference is for a temporary period only. Once the line of sight is not blocked anymore, the transmission process will automatically resume. This problem can be solved by providing multiple beam system.

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Atmospheric scintillation is the phenomenon when the light intensities change in time and space at the receiver. The changes in the refractive index of air along the transmission path is due to the heat. This results in a fluctuation of receiving signals at the detector. The changes in this index make the atmosphere acts as if there is a series of small lenses that causes the deflection of the light beam into and out of the way of transmission path. The scintillation becomes worse when the temperature is at its highest. The main effects of scintillation are rapid fluctuations of receiving power and high-error-rate in FSO performance. The effect of scintillation can be reduced by implementation of multiple laser transmitters (Bloom, 2003).

Absorption can be defined as the extinguishing of photons by suspended water molecules in the terrestrial atmosphere. It results in a decrease in the power density of the FSO beam which directly affects the availability of a system. However the availability of the network can be maintained by using multiple beam and appropriate power (Kher, 2006). Scattering occurs when the wavelength and scatterer collides.

The type of scattering is based on the physical size of the scatterer. There are three types of scattering which are non-selective scattering, Mie scattering and Rayleigh scattering. Non-selective scattering is when the scatterer is much larger than the wavelength while Mie scattering is when the scatterer is of comparable size to the wavelength. On the other hand Rayleigh scattering is when the scatterer is smaller than the wavelength [54].

As FSO system is often mounted on the building, it is exposed to the building sway effect. Building sway can be caused by small earthquake, thermal expansion, strong wind and vibration. The building sway causes the deflection of the laser beam from the transmission path. It will interrupt the process of data transmission. There are many sources of vibration such as large machine, air compression, elevators, railroad,

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highway traffic and human activity such as walking across the floor. The vibration range of walls and floors of the building is between 3 Hz and 100 Hz. The magnitude of vibration in this range can be detrimental to the building structure, floors and ceilings. Usually, the vibration from 8 Hz at 3900 microinches to 100 Hz at 400 microinches can lead to building damage. The natural frequency of the buildings greater than 30 stories which is affected by wind is from 0.1 Hz to 5 Hz (Dankowski, n.d).

A common source of vibration with its amplitude in the building is shown in Table 1.1. So to overcome this problem, active vibration isolation system is proposed.

It will be placed under the telescope either at transmitter or receiver to isolate the system from ground vibration. Figure 1.3 shows the propose system.

Table 1.1

Common sources of vibration (www.fabreeka.com)

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Figure 1.3: Proposed active vibration isolation system

1.2 PROBLEM STATEMENT AND ITS SIGNIFICANCE

In FSO communication, the alignment of the transmitter and receiver of the telescope is very important in transferring data. The line of sight of their optics must be aligned during the entire communication time. Once the telescopes of the transmitter and receiver are aligned, one could think of fixing the components in that position and leaving the system untouched. However because of the large distance between the transmitter and the receiver, the pointing from transmitter to receiver is complicated.

There are several factors that contribute to this problem such as fog, physical obstructions, absorption, scattering, scintillation and building sway (Lin, 2001). The building sway can be caused by vibration from the ground and surrounding which includes large machine, air compression, elevators, railroad, highway traffic and human activity such as walking across the floor. These will lead to the deflection of the laser beam from the transmission path. So in order to overcome this problem, the active vibration isolator is proposed.

The significance of this project is to reduce the vibration. This will align the receiver telescope with the transmitter telescope. Only then the communication can be

A thesis submitted in fulfilment of the requirement for the degree of Master of Science

ACTIVE VIBRATION ISOLATION BY USING VOICE COIL ACTUATOR FOR FREE SPACE OPTIC

COMMUNICATION

BY

SYAZWANI AB. RAHIM

A thesis submitted in fulfilment of the requirement for the degree of Master of Science

(Mechatronics Engineering)

Kulliyyah of Engineering

International Islamic University Malaysia

MARCH 2014

ABSTRACT

APPROVAL PAGE

DECLARATION

My beloved parent and family

INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA

DECLARATION OF COPYRIGHT AND AFFIRMATION OF FAIR USE OF UNPUBLISHED RESEARCH

ACTIVE VIBRATION ISOLATION BY USING VOICE COIL ACTUATOR FOR FREE SPACE OPTIC COMMUNICATION

My beloved parent and family

ACKNOWLEDGEMENTS

TABLE OF CONTENTS

LIST OF TABLES

LIST OF FIGURES

.

LIST OF ABBREVIATIONS

LIST OF SYMBOLS

CHAPTER ONE INTRODUCTION