Improved Design of Wireless Electrical Energy Transfer System for Various Power Applications

This thesis introduces a state-of-the-art review of existing wireless power transfer (WPT) technologies with a detailed comparison and presents the limitations of the inductive power transfer system through simulation and practical analyses. This thesis also presents the expanded use of the high-frequency analysis tool, known as FEKO, and the novel application of frequency response analyser (FRA) with various simulations and practical demonstrations for enhancing the design and maintenance of WPT systems

Fundamentals of Inductively Coupled Wireless Power Transfer Systems

The objective of this chapter is to study the fundamentals and operating principles of inductively coupled wireless power transfer (ICWPT) systems. This new technology can be used in various wireless power transfer applications with different specifications, necessities, and restrictions such as in electric vehicles and consumer electronics. A typical ICWPT system involves a loosely coupled magnetic coupling structure and power electronics circuitries as an integrated system. In this chapter, the emphasis is placed on the magnetic coupling structure, which is the most important part of the system. Although this technology has motivated considerable research and development in the past two decades, still there are several theoretical studies such as the level of the operating frequency, operating at high secondary circuit quality factor, coupling efficiency, etc., that need further investigation to fully develop the governing mathematical relationships of this technology

Near-Field Analysis and Design of Inductively-Coupled Wireless Power Transfer System in FEKO

Inductively-coupled wireless power transfer (WPT) system is broadly adopted for charging batteries of mobile devices and electric vehicles. The performance of the WPT system is sensitively dependent on the strength of electromagnetic coupling between the coils, compensating topologies, loads and airgap variation. This paper aims to present a comprehensive characteristic analysis for the design of the WPT system with a numerical simulation tool. The electromagnetic field solver FEKO is mainly used for studying high-frequency devices. However, the computational tool is also applicable for not only the analysis of the electromagnetic characteristic but also the identification of the electrical parameters in the WPT system operating in the nearfield. In this paper, the self and mutual inductance of the wireless transfer windings over the various airgaps were inferred from the simulated S-parameter. Then, the formation of the magnetic coupling and the distribution of the magnetic fields between the coils in the seriesparallel model were examined through the near-field analysis for recognizing the efficient performance of the WPT system. Lastly, it was clarified that the FEKO simulation results showed good agreement with the practical measurements. When the input voltage of 10 V was supplied into the transmitting unit of the prototype, the power of 5.31 W is delivered with the transferring efficiency of 97.79% in FEKO. The actual measurements indicated 95.68% transferring efficiency. The electrical parameters; in , out, in , , in , and out, had a fair agreement with the FEKO results, and they are under 8.4% of error

Coupled resonator based wireless power transfer for bioelectronics

Implantable and wearable bioelectronics provide the ability to monitor and modulate physiological processes. They represent a promising set of technologies that can provide new treatment for patients or new tools for scientific discovery, such as in long-term studies involving small animals. As these technologies advance, two trends are clear, miniaturization and increased sophistication i.e. multiple channels, wireless bi-directional communication, and responsiveness (closed-loop devices). One primary challenge in realizing miniaturized and sophisticated bioelectronics is powering. Integration and development of wireless power transfer (WPT) technology, however, can overcome this challenge. In this dissertation, I propose the use of coupled resonator WPT for bioelectronics and present a new generalized analysis and optimization methodology, derived from complex microwave bandpass filter synthesis, for maximizing and controlling coupled resonator based WPT performance. This newly developed set of analysis and optimization methods enables system miniaturization while simultaneously achieving the necessary performance to safely power sophisticated bioelectronics. As an application example, a novel coil to coil based coupled resonator arrangement to wirelessly operate eight surface electromyography sensing devices wrapped circumferentially around an able-bodied arm is developed and demonstrated. In addition to standard coil to coil based systems, this dissertation also presents a new form of coupled resonator WPT system built of a large hollow metallic cavity resonator. By leveraging the analysis and optimization methods developed here, I present a new cavity resonator WPT system for long-term experiments involving small rodents for the first time. The cavity resonator based WPT arena exhibits a volume of 60.96 x 60.96 x 30.0 cm3. In comparison to prior state of the art, this cavity resonator system enables nearly continuous wireless operation of a miniature sophisticated device implanted in a freely behaving rodent within the largest space. Finally, I present preliminary work, providing the foundation for future studies, to demonstrate the feasibility of treating segments of the human body as a dielectric waveguide resonator. This creates another form of a coupled resonator system. Preliminary experiments demonstrated optimized coupled resonator wireless energy transfer into human tissue. The WPT performance achieved to an ultra-miniature sized receive coil (2 mm diameter) is presented. Indeed, optimized coupled resonator systems, broadened to include cavity resonator structures and human formed dielectric resonators, can enable the effective use of coupled resonator based WPT technology to power miniaturized and sophisticated bioelectronics

Ambient RF energy harvesting and efficient DC-load inductive power transfer

This thesis analyses in detail the technology required for wireless power transfer via radio frequency (RF) ambient energy harvesting and an inductive power transfer system (IPT). Radio frequency harvesting circuits have been demonstrated for more than fifty years, but only a few have been able to harvest energy from freely available ambient (i.e. non-dedicated) RF sources. To explore the potential for ambient RF energy harvesting, a city-wide RF spectral survey was undertaken in London. Using the results from this survey, various harvesters were designed to cover four frequency bands from the largest RF contributors within the ultra-high frequency (0.3 to 3 GHz) part of the frequency spectrum. Prototypes were designed, fabricated and tested for each band and proved that approximately half of the London Underground stations were found to be suitable locations for harvesting ambient RF energy using the prototypes. Inductive Power Transfer systems for transmitting tens to hundreds of watts have been reported for almost a decade. Most of the work has concentrated on the optimization of the link efficiency and have not taken into account the efficiency of the driver and rectifier. Class-E amplifiers and rectifiers have been identified as ideal drivers for IPT applications, but their power handling capability at tens of MHz has been a crucial limiting factor, since the load and inductor characteristics are set by the requirements of the resonant inductive system. The frequency limitation of the driver restricts the unloaded Q-factor of the coils and thus the link efficiency. The system presented in this work alleviates the use of heavy and expensive field-shaping techniques by presenting an efficient IPT system capable of transmitting energy with high dc-to-load efficiencies at 6 MHz across a distance of 30 cm.Open Acces

IMPROVING EFFICIENCY OF WIRELESS POWER TRANSFER VIA MAGNETIC RESONANCE COUPLING

Described herein is wireless energy transmission via magnetic resonant coupling for author’s FYP project. The idea is based on two resonant coils, with one acting as transmitter, which consist of source and circuit, and the other as receiver connected to load, such as low power LED, having strong coupling electromagnetic resonant for wireless energy transmission from transmitter to receiver over a certain distance. The working principle operates as traditional inductance magnetic coupling devices, where Faradays’ Law states that, a time varying magnetic field of a coil of wire, voltage (emf) will be induced in the coil. However, these principles will limit the efficiency and distance transfer between transmitter and receiver. Thus, by applying resonant concept, which tunes both objects operating frequencies into resonant frequency, we can transfer energy wirelessly with greater efficiency and longer distance. This paper will emphasize on the fundamental principle in order to realize the concept until the design of the prototype itself. The basic theory such as magnetic induction, resonant frequency as well as magnetic resonant coupling will be further explained for better understanding and clarification. Apart from that, further analysis will also discussed and compared with the achievement and work done by others in comprehensive literature review chapter. In the design of prototype, a number of calculations have been done in order to get the resonance frequency which can be applied to both coils to function and the process of designing the circuit and building it through exclusive studies, will also be explained in detail. Last but not least, author will further analyze the circuit comprehensively by studying on three most important results, which are voltages, magnetic field intensities, and power with respect to different parameter setting. The author compared the finding by using theoretical calculation and measurement by using spectrum analyzer and multi-meter. All the measurement will be tabulated in tables and graphs

Improving the mechanistic study of neuromuscular diseases through the development of a fully wireless and implantable recording device

Neuromuscular diseases manifest by a handful of known phenotypes affecting the peripheral nerves, skeletal muscle fibers, and neuromuscular junction. Common signs of these diseases include demyelination, myasthenia, atrophy, and aberrant muscle activity—all of which may be tracked over time using one or more electrophysiological markers. Mice, which are the predominant mammalian model for most human diseases, have been used to study congenital neuromuscular diseases for decades. However, our understanding of the mechanisms underlying these pathologies is still incomplete. This is in part due to the lack of instrumentation available to easily collect longitudinal, in vivo electrophysiological activity from mice. There remains a need for a fully wireless, batteryless, and implantable recording system that can be adapted for a variety of electrophysiological measurements and also enable long-term, continuous data collection in very small animals. To meet this need a miniature, chronically implantable device has been developed that is capable of wirelessly coupling energy from electromagnetic fields while implanted within a body. This device can both record and trigger bioelectric events and may be chronically implanted in rodents as small as mice. This grants investigators the ability to continuously observe electrophysiological changes corresponding to disease progression in a single, freely behaving, untethered animal. The fully wireless closed-loop system is an adaptable solution for a range of long-term mechanistic and diagnostic studies in rodent disease models. Its high level of functionality, adjustable parameters, accessible building blocks, reprogrammable firmware, and modular electrode interface offer flexibility that is distinctive among fully implantable recording or stimulating devices. The key significance of this work is that it has generated novel instrumentation in the form of a fully implantable bioelectric recording device having a much higher level of functionality than any other fully wireless system available for mouse work. This has incidentally led to contributions in the areas of wireless power transfer and neural interfaces for upper-limb prosthesis control. Herein the solution space for wireless power transfer is examined including a close inspection of far-field power transfer to implanted bioelectric sensors. Methods of design and characterization for the iterative development of the device are detailed. Furthermore, its performance and utility in remote bioelectric sensing applications is demonstrated with humans, rats, healthy mice, and mouse models for degenerative neuromuscular and motoneuron diseases