Electrical and Electronic Engineering - Doctoral Theses

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    Electromagnetic tracking methods and magnetic modelling for distortion compensation
    (University College Cork, 2023) Cavaliere, Marco; Cantillon-Murphy, Padraig; Hayes, John G.; Science Foundation Ireland; European Research Council
    The thesis presents a comprehensive study of electromagnetic tracking (EMT), focusing on developing methods and techniques to reduce and compensate for distortions in the magnetic field through improved modelling and real-time correction methods. To this end, the research-oriented Anser EMT system is employed. Anser is the Latin name of the greylag goose, which uses the geomagnetic field for navigation. In this work, a general method for modelling magnetic fields is developed to significantly improve the Anser EMT magnetic model by correcting systematic errors and including magnetic shielding. Moreover, real-time compensation techniques for dynamic distortion are proposed using external reference sensors. Further improvements are demonstrated for dynamic tracking by optimising the EMT model and algorithm. Finally, the effectiveness of the Anser EMT system for developing novel EMT applications is demonstrated by introducing alternative tracking techniques based on the magnetic scalar potential formulation, particularly suited for tracking the elongated sensor coils used in medical applications, and on the magnetic vector potential formulation, for tracking large-area PCB coils. Overall, this work provides the theoretical and experimental basis for a new approach to distortion rejection in EMT systems with significant potential for future clinical benefit in the years to come.
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    Electrochemical sensor interface
    (University College Cork, 2023) Murphy, Aidan; O'Connell, Ivan; O'Riordan, Alan
    Recent advances in nanotechnology have led to the development of electrochemical sensors that utilize electrodes with a width of one micron or less. This increased sensitivity has opened up a range of new electrochemical sensing applications, allowing the technology to move beyond the confines of the laboratory and into real-world settings. However, the interfacial electronics used for these sensors are often too bulky for portable use and can be prohibitively expensive due to the low current measurement capability required from the instrument. To address this challenge, this thesis presents cost-effective measures for creating portable interfaces specifically designed for ultra-micro and nano-scale electrochemical sensors. A portable data acquisition system has been developed to interface to nano and ultra-micro scale electrochemical sensors at the point of use through voltammetry. It can perform a range of voltammetric tests, including cyclic voltammetry, square wave voltammetry and generator collector voltammetry. The data acquisition system interfaces to a smartphone, operates from a rechargeable battery and is of suitable form factor to ensure that it’s fully portable. By utilising commercially available components, this system has been developed to lower the barrier for entry for the development of emerging portable electrochemical sensing technologies at micro and nano scale. A second data acquisition system has been developed to interface to nano and ultra micro electrochemical immunosensors through Electrochemical Impedance Spectroscopy. Results from the device were benchmarked against laboratory equipment to ensure it is of suitable sensitivity to be fit for purpose. The printed circuit board has been designed such that it can be integrated into a handheld device suitable for operatives such as veterinarians. This system will aid in the detection of biological agents such as viruses and antibodies at the point of sample, particularly in electrochemical sensors designed for agricultural applications.
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    Planning studies for distribution grids with high penetration of distributed energy resources: the challenge of fairness in future electricity networks
    (University College Cork, 2023-05-02) Cuenca, Juan Jose; Hayes, Barry; Leahy, Paul; Massey, Beth; Department of Jobs, Enterprise and Innovation; Government of Huila
    The inclusion of distributed energy resources and electrification of heat and transport is creating additional supply and demand stresses that distribution grids were not originally designed for. The flows of energy and revenue are changing in magnitude and direction, making these grids more dynamic over time. In this changing landscape, the traditional approach for planning in distribution networks of "oversize, fit and forget" is not enough. A review of the literature in grid planning shows that the current focus is on transmission-network-inspired methods that are not realistically scalable for the distribution network case. Accordingly, this thesis presents a collection of novel technical and economic methodologies to transform the planning paradigm into an active one, including sharing economy concepts. First, this work presents a technology-agnostic impartial method to assign customers with export capacity for distributed generation. Subsequently, a new method to determine location, size, and prioritisation of flexibility resources at the distribution level is formulated using information on forecasted constraints and grid topology, this includes obtaining a distribution network expansion plan. Next, this thesis performs a technical/economic analysis of future distribution grids. Through co-simulation of electricity distribution networks and decentralised electricity trading platforms, an advanced methodology is developed for the assignment of electricity use of network charges. Ultimately, to paint a broader picture, this manuscript explores the socio-economic implications of the energy transition through the long-term simulation of access to distributed generation for small-scale participants at a national level. These new propositions are validated using two standard IEEE test networks, two real distribution feeders in the west coast of Ireland, and ultimately the entire interconnected distribution and transmission networks from Ireland. Technologies studied include small-scale rooftop solar PV, wind turbines, battery energy storage systems, voltage regulators and infrastructure upgrades. This work presents novel tools for planners to address the new challenges of modern and future distribution networks.
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    Development of electromagnetic vibration energy harvesters as powering solution for IoT based applications
    (University College Cork, 2022-09-20) Paul, Kankana; Roy, Saibal; Amann, Andreas; Kennedy, Peter; Science Foundation Ireland; Horizon 2020
    The drive towards building pervasive intelligence encompassing urban as well as rural environments has paved the way for the Internet of Things (IoT), which has reshaped our regular lifestyle alleviating the dependence on wired communication systems since its inception. The inexorable advancement in low to ultra-low power electronics have steered the rapid growth of the IoT platform expanding into several application fields. With the ongoing implementation of 5G (Fifth generation) and the emergence of 6G (Sixth generation) wireless technology on the horizon, the explosive growth of IoT connected devices reinforces the requirement of a robust and reliable power solution for the deployed wireless communication platforms. Utilizing distributed clean energy sources, especially the ubiquitous mechanical energy available in environment through dedicated transducers in the form of vibration energy harvesters (VEHs) to power the IoT-based wireless sensor platforms is a sought after alternatives to batteries in the forthcoming IoT applications. The potential of the resonant/linear VEHs have been limited owing to the narrow operable frequency bandwidth as well as due to the lack of intelligent device designs that aids to yield large electrical power from the provided mechanical energy. In this thesis, a concertina shaped linear VEH spring architecture has been exploited to instigate large amplitudes of oscillation, which aids to yield a high power density (455.6μW/cm3g2) at resonance from a relatively small device footprint. From the application perspective, this concertina-VEH has been utilized to power the electronics interface and enhance the performance of a NFC (Near Field Communication) based wireless sensor platform which offers the benefits of low power consumption and on call data acquisition through this short range NFC based communication protocol. Such a robust autonomous wireless sensing platform offers the potential to be used in a large number of IoT based applications. Despite of the large deliverable power obtained from the resonant VEH, the energy extraction drops dramatically as the excitation frequency deviates from the resonance condition, which is inevitable owing to the random nature of vibrations. A novel broadband VEH with tapered spring geometry has been developed as a part of this thesis to address this issue. Nonlinear restoring forces arising from the stretched springs enables the VEH to generate large power over a considerably wide bandwidth (45Hz of hysteresis width that is the difference of the jump down and jump up frequency with 1g excitation amplitude) of operable frequencies. Suitable power management strategies have been proposed to enhance the energy extraction capabilities. The nonlinear VEH has been successfully used to harness mechanical energy from the broadband vibrations of a car; the extracted energy is fed to a wireless sensor platform that reports on ambient temperature and humidity. This self-powered sensing system opens up the scope for exploiting this technology for monitoring food and medicinal quality during transportation while the VEH extracts mechanical energy from the transporting vehicle and perpetually powers the wireless sensor node. Multiple nonlinearities arising from the stretching of the VEH spring as well as from the interaction of repulsive magnets have been introduced into the energy harvester, which gives rise to coexisting multiple energy branches. Not all of these energy states are achieved through the typical excitation frequency routine, some of these energy states are rather hidden. Experimentally a route to achieve these hidden energy branches have been explored in this work. Suitable frequency routines have been designed to achieve and sustain these higher energy states. A useful graphical representation has been introduced in the form of ‘eye diagrams’ that essentially estimates the transaction of energy from mechanical to electrical domain, and provides deep insight of the dynamical features of each energy branches, based on time resolved measurements of acceleration and voltage. A mathematical model has been developed to investigate the intricate complexities of the nonlinear system, which supports the experimental findings. One of the major impediments in miniaturizing high-efficiency macroscale VEHs into MEMS (Micro-Electro-Mechanical-System) scale is the lack of matured technology for the CMOS (Complementary-Metal-Oxide-Semiconductor) compatible integration of magnets and the adverse effect of scaling on the permanent hard magnets. A part of the presented work investigates the effect of patterning continuous thin films of magnets into micromagnet array. With detailed analytical framework and exhaustive finite element analysis, the shape, size and distribution of these micromagnets have been optimized to maximize the stray magnetic field emanating from each edge of these magnets. Novel MEMS device topologies comprising of linear/nonlinear MEMS springs, micromagnet arrays and copper microcoil have been proposed which systematically maximizes the electromagnetic interaction between the micromagnets and the integrated coil that in turn translates into large deliverable power. In addition to the developed device prototypes and demonstrations, this thesis further provides a firm roadmap that highlights the potential routes for enhancing the energy harvesting capabilities through highly integrated MEMS scale VEHs as well as for improving system level integration to establish these VEHs as a reliable and sustainable alternative of batteries in IoT applications.
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    Development and characterisation of macro-disc and micro-band electrodes for electrochemical sensing applications
    (University College Cork, 2022) Madden, Julia; Galvin, Paul; O'Riordan, Alan; Thompson, Michael; Science Foundation Ireland; Electronic Components and Systems for European Leadership
    The aim of this PhD thesis was to investigate potential next generation sensor platforms for electrochemical biosensor developments, specifically towards health monitoring applications. With increasing interest in the integration of miniaturised electrodes with minimally invasive and wearable devices, this thesis sought to explore electrodes fabricated using three different technologies for the construction of electrochemical biosensors: Silicon microfabrication, Laser scribing, and dispense printing. The first experimental section aimed to investigate the use of a single ultramicroband electrode fabricated on silicon for mediator-free glucose monitoring in bio-fluid environments. Six ultramicroband electrodes, a counter electrode and reference electrode were fabricated using standard microfabrication methods i.e. lithography and etching techniques. Glucose oxidase was selected as a model enzyme to attach onto a platinum modified gold microband electrode by electropolymerisation with an o-phenylenediamine/ß-cyclodextrin layer. The resulting microband biosensor demonstrated on-chip glucose detection in buffer based media. When applied to foetal bovine serum the sensor displayed a reduced sensitivity. The second experimental section explores the use of laser-scribed graphitic carbon for flexible sensing applications. A facile fabrication method was assessed involving electrodeposition of platinum followed by two casting steps to functionalise electrodes. This study examined the chronoamperometric response of the enzymatic lactate sensor whilst the flexible polyimide substrates were fixed at a curvature (K) of 0.14 mm-1. No noticeable change in signal response was observed in comparison to calibrations obtained with a flat substrate (K=0 mm-1), suggesting potential opportunities for sensor attachment or integration with oral-care products such as mouth swabs and mouth guards. Both laser scribed graphitic carbon and Ag/AgCl modified-laser scribed graphitic carbon were examined as reference electrodes for chronoamperometric lactate measurements. This device was applied for measuring lactate concentrations in artificial saliva and diluted sterile human serum. Finally, this study investigates the potential for a low cost additive printing tool to enable the fabrication of electrochemical sensor devices. To do this, electrodes were designed and printed onto polyimide substrates. Reproducibility between electrode dimensions was assessed using 3D microscopy. Standard electrochemical characterisation techniques were employed to study the reproducibility between electrode electrochemical response. Functionality was also assessed whilst electrodes were fixed were fixed at a curvature (K) of 0.14 mm-1. Finally, a simple casting approach was applied to the dispense printed working electrode to construct a lactate biosensor for a proof of concept electrochemical sensor demonstration.