Misalignment insensitive wireless power transfer system for powering implanted biomedical devices

Abstract

Wireless power transfer (WPT), a concept dating back to Nikola Tesla’s innovations over a century ago, has recently gained increased attention, especially in biomedical realms like charging pacemakers, wireless endoscopic capsules, neural and cochlear implants, retinal prostheses, etc. Despite its flexibility, safety, and aesthetics advantages, practical WPT systems encounter challenges, notably misalignment between transmitter (Tx) and receiver (Rx) coils in biomedical implants. This thesis proposes a solution using field-forming techniques to mitigate misalignment issues in Tx design. Additionally, it explores optimizing Rx antennas to efficiently capture the magnetic field generated by conventional Tx setups, addressing misalignment problems in biomedical implants and other applications. The thesis is structured into eight chapters. In Chapter 1, the fundamentals of the near-field WPT system are explored, encompassing a discussion on various potential research challenges inherent to the WPT system. Moreover, this chapter identifies the most important issue, which forms the focal point of this thesis. It also undertakes an intensive investigation of existing solutions available in the literature. Concurrently, Chapter 2 provides the mathematical background essential for analyzing and modelling WPT systems employing field-forming techniques. This chapter outlines the closed-form equations for conventionally used coil structures and defines the various design parameters. Meanwhile, Chapter 3 focuses on establishing a mathematical framework for examining 3−D rotating H-fields, with particular emphasis on mitigating angular misalignment problems, notably in the context of charging biomedical implants. In contrast, Chapter 4 presents the inception of a novel methodology, amalgamating traditional field-forming techniques with switching control to obtain an orientation-insensitive WPT system. This method necessitates only a single sinusoidal source instead of the multiple modulated sources requisite in the traditional 3−D rotating H-field method. Subsequently, Chapter 5 introduces a magnetic localization method tailored for tracking both the position and orientation of a mobile receiver employed in biomedical implants. A thorough investigation draws a comparison between the existing technique centered on frequency-divisional approaches and a novel time-divisional approach aimed at mitigating circuit complexity and system cost. Chapter 6 marks an integration of previously proposed localization techniques with magnetic beamforming to address diverse misalignment challenges using a single Tx antenna, an innovative approach unexplored in near-field WPT applications. Here, a machine-learning model is adopted to localize the Rx, while particle swarm optimization is employed to effectively shape the desired magnetic beam. Employing a single excitation source and switching circuitry, the proposed Tx is energized, thus reducing circuit complexity and system cost. Finally, Chapter 7 introduces a novel Rx structure optimized to harness both longitudinal and lateral field components effectively for addressing misalignment issues. The proposed Rx is realized using multi-layer PCB technology, which encapsulates all circuit elements within the antenna structure, making it a compact, robust, and cost-effective solution poised as an ideal option for wirelessly powering biomedical implants and wearable devices. Furthermore, a use case is proposed for other applications, such as drone charging. Finally, Chapter 8 concludes the thesis and explores future development avenues to enhance proposed methodologies.