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Harvesting Mechanical Vibrations Using a Frequency Up-Converter

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Harvesting Mechanical Vibrations Using a Frequency Up-Converter Harvesting Mechanical Vibrations using a Frequency Up-converter Thesis by Esraa Fakeih In Partial Fulfillment of the Requirements For the Degree of Master of Science King Abdullah University of Science and Technology Thuwal, Kingdom of Saudi Arabia April, 2020 2 EXAMINATION COMMITTEE PAGE The thesis of Esraa Fakeih is approved by the examination committee. Committee Chairperson: Prof. Khaled Salama Committee Members: Prof. Mohammad Younis, Prof. Shehab Ahmed 3 © April, 2020 Esraa Fakeih All Rights Reserved 4 ABSTRACT Voltage Enhancer Mechanical Energy Harvester Esraa Fakeih With the rise of wireless sensor networks and the internet of things, many sensors are being developed to help us monitor our environment. Sensor applications from marine animal tracking to implantable healthcare monitoring require small and non-invasive methods of powering, for which purpose traditional batteries are considered too bulky and unreasonable. If appropriately designed, energy harvesting devices can be a viable solution. Solar and wind energy are good candidates of power but require constant exposure to their sources, which may not be feasible for in-vivo and underwater applications. Mechanical energy, however, is available underwater (the motion of the waves) and inside our bodies (the beating of the heart). These vibrations are normally low in frequency and amplitude, thus resulting in a low voltage once converted into electrical signals using conventional mechanical harvesters. These mechanical harvesters also suffer from narrow bandwidth, which limits their efficient operation to a small range of frequencies. Thus, there is a need for a mechanical energy harvester to convert mechanical energy into electrical energy with enhanced output voltage and for a wide range of frequencies. In this thesis, a new mechanical harvester is introduced, and two different methods of rectifying it are investigated. 5 The designed harvester enhances the output voltage and extends the bandwidth of operation using a mechanical frequency up-convertor. This is implemented using magnetic forces to convert low-frequency vibrations to high-frequency pulses with the help of a piezoelectric material to generate high output voltage. The results show a 48.9% increase in the output voltage at 12.2Hz at an acceleration of 1.0g, and a bandwidth increase from 0.23Hz to 11.4Hz. For the rectification, mechanical rectifiers are discussed, which would obviate the need for electrical rectification, thus preventing the losses normally caused by the threshold voltage of electronics. Two designs of mechanical rectifiers are investigated and implemented on the frequency up-converter: a static rectifier and a rotating rectifier. The results show a voltage rectification, which required a sacrifice in the bandwidth and boosted voltage. 6 ACKNOWLEDGEMENTS First, I would like to thank my committee chair and supervisor Prof. Khaled Salama for his constant guidance and support during this research. It took longer than expected, and I am very appreciative for his patience through it all. I would also like to thank my committee members, Prof. Shehab Ahmed and Prof. Mohammad Younis, for their support. This research would have been much more difficult without the constant help and advice of my advisor, Abdullah Almansouri, and for that I am very grateful. My appreciation also goes to my friends, both inside and outside King Abdullah University of Science and Technology, for continuously encouraging me to keep going during challenging times. Finally, my heartfelt gratitude is extended to my parents and siblings for always being there for me whenever I needed them and for supporting me throughout this journey. 7 TABLE OF CONTENTS EXAMINATION COMMITTEE PAGE ................................................................................ 2 COPYRIGHT PAGE ......................................................................................................... 3 ABSTRACT .................................................................................................................... 4 ACKNOWLEDGEMENTS ................................................................................................ 6 TABLE OF CONTENTS .................................................................................................... 7 LIST OF ABBREVIATIONS ............................................................................................... 9 LIST OF SYMBOLS ....................................................................................................... 10 LIST OF ILLUSTRATIONS .............................................................................................. 11 LIST OF TABLES ........................................................................................................... 12 INTRODUCTION .......................................................................................................... 13 1.1 ENERGY HARVESTING ................................................................................................... 13 1.2 PROBLEM STATEMENT .................................................................................................. 15 1.3 OBJECTIVES ................................................................................................................ 16 BACKGROUND: VIBRATIONAL ENERGY HARVESTING .................................................. 17 2.1 SYSTEM ARCHITECTURE ................................................................................................. 17 2.2 METHODS OF HARVESTING: A LITERATURE REVIEW ............................................................ 20 2.2.1 Voltage Amplifiers ........................................................................................... 20 2.2.2 Bandwidth Amplifiers ...................................................................................... 21 2.2.3 Mechanical Rectifiers ...................................................................................... 22 PROPOSED SYSTEM I: VOLTAGE AND BANDWIDTH ENHANCER .................................. 25 3.1 SYSTEM DESIGN .......................................................................................................... 25 3.2 WORKING PRINCIPLE .................................................................................................... 30 3.3 FABRICATION .............................................................................................................. 32 3.4 RESULTS .................................................................................................................... 33 PROPOSED SYSTEM II: MECHANICAL RECTIFIER .......................................................... 40 4.1 MODEL I: STATIC RECTIFIER ........................................................................................... 43 4.1.1 System Design ................................................................................................. 43 4.1.2 FaBrication ...................................................................................................... 45 4.1.3 Results ............................................................................................................. 46 4.2 MODEL II: ROTATING RECTIFIER ..................................................................................... 48 4.2.1 System Design ................................................................................................. 48 4.2.2 FaBrication ...................................................................................................... 49 4.2.3 Results ............................................................................................................. 50 4.3 SUMMARY .................................................................................................................. 52 8 CONCLUSION .............................................................................................................. 54 FUTURE WORK ........................................................................................................... 57 BIBLIOGRAPHY ........................................................................................................... 60 9 LIST OF ABBREVIATIONS AC alternating current AI Artificial intelligence DC direct current HF high-frequency LF low-frequency MEMS micro-electromechanical systems PLA polylactic acid PVDF polyvinylidene fluoride PZT lead zirconate titanate RMS root mean square 10 LIST OF SYMBOLS ω The angular frequency ρ The density of a material π The ratio of any circle’s circumference to its diameter 11 LIST OF ILLUSTRATIONS Figure 2.1 Oscillating cantilever.................................................................................. 17 Figure 2.2 Piezoelectric voltage generation................................................................ 19 Figure 3.1 Single beam energy harvester ................................................................... 25 Figure 3.2 Voltage and bandwidth of single beam energy harvester at 12.2Hz ........ 26 Figure 3.3 Proposed system........................................................................................ 27 Figure 3.4 Voltage generation.................................................................................... 30 Figure 3.5 Working principle of the system................................................................ 31 Figure 3.6 Fabricated system...................................................................................... 32 Figure 3.7 Setup of the experimental testing............................................................
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