160 results found
Kwan CH, Yates DC, Mitcheson PD, 2019, Reducing human body heating and temperature rises due to inductively-powered implantable medical devices, ISSN: 1742-6588
© Published under licence by IOP Publishing Ltd. The use of inductive power transfer (IPT) for medical implants can cause heating and temperature rises in human tissue. Increasing the load resistance away from the optimal value for maximising link efficiency has been shown to reduce the specific absorption rate (SAR) and temperature rises in a human body model in electromagnetic and thermal simulations. However, these quantities are generally difficult to measure as they are internal to the body, so experiments with a phantom should be used to verify the theory and simulations. This paper presents results of an experiment, in which 10 W is delivered to a receiver immersed in salt water with two different load resistances. The temperature rise of the salt water was lower with the use of the increased load. Simulations of the experimental setup demonstrate good agreement with experimental results.
Arteaga Saenz J, Aldhaher S, Kkelis G, et al., 2019, Dynamic capabilities of multi-MHz inductive power transfer systems demonstrated with batteryless drones, IEEE Transactions on Power Electronics, Vol: 34, Pages: 5093-5104, ISSN: 0885-8993
This paper presents the design of a multi-MHz inductive power transfer (IPT) system showcasing lightweight and energy-efficient solutions for non-radiative wireless power transfer. A proof of concept is developed by powering a drone without a battery that can hover freely in proximity to an IPT transmitter. The most challenging aspect, addressed here for the first time, is the complete system level design to provide uninterrupted power-flow efficiently while allowing for variable power demand and highly variable coupling factor. The proposed solution includes the design of lightweight air-core coils that can achieve sufficient coupling without degrading the aerodynamics of the drone, and designing newly-developed resonant power converters at both ends of the system. At the transmittingend, a load-independent Class EF inverter, which can drive a transmitting-coil with constant current amplitude and achieves zero-voltage switching (ZVS) for the entire range of operation, was developed; and at the receiving-end, a hybrid Class E rectifier, which allows tuning for large changes in coupling and power demand, was used. For the demo, the range of motion of the drone was limited by a 7.5 cm nylon string tether, connected between the centre of the transmitting-coil and the bottom of the drone. The design of the IPT system, including all the power conversion stages and the IPT link, is explained in detail. The results on performance and specific practical considerations required for the physical implementation are provided. An average end-to-end efficiency of 60% was achieved for a coupling range of 23% to 5.8%. Relevant simulations concerning human exposure to electromagnetic fields are also included to assure that the demo is safe according to the relevant guidelines. This paper is accompanied by a video featuring the proposed IPT system.
Lawson J, Yates DC, Mitcheson PD, 2019, High Q Coil Measurement for Inductive Power Transfer, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, Vol: 67, Pages: 1962-1973, ISSN: 0018-9480
Arteaga JM, Aldhaher S, Yates DC, et al., 2019, A Multi-MHz Wireless Power Transfer System With Mains Power Factor Correction Circuitry on the Receiver, 34th Annual IEEE Applied Power Electronics Conference and Exposition (APEC), Publisher: IEEE, Pages: 683-688, ISSN: 1048-2334
Aldhaher S, Yates D, Mitcheson P, 2018, Load-independent class E/EF inverters and rectifiers for MHz-switching applications, IEEE Transactions on Power Electronics, Vol: 33, Pages: 8270-8287, ISSN: 0885-8993
This paper presents a unified framework for themodelling, analysis and design of load-independent Class E andClass EF inverters and rectifiers. These circuits are able tomaintain zero-voltage switching (ZVS) and hence high efficiencyfor a wide load range without requiring tuning or use of afeedback loop, and simultaneously achieve a constant amplitudeAC voltage or current in inversion, and a constant DC outputvoltage or current in rectification. As switching frequencies aregradually stepping into the megahertz (MHz) region with the useof wide-bandgap (WBG) devices such as GaN and SiC, switchingloss, implementing fast control loops and current sensing becomea challenge which load-independent operation is able to address,thus allowing exploitation of the high frequency capability ofWBG devices. The traditional Class E and EF topologies arefirst presented and the conditions for load-independent oper-ation are derived mathematically, then a thorough analyticalcharacterisation of the circuit performance is carried out interms of voltage and current stresses and power-output capability.From this, design contours and tables are presented to enablethe rapid implementation of these converters given particularpower and load requirements. Three different design examplesare used to showcase the capability of these converters in typicalMHz power conversion applications using the design equationsand methods presented in this paper. The design examples arechosen towards enabling efficient and high power density MHzconverters for wireless power transfer (WPT) applications andDC/DC conversion. Specifically a150W 13.56MHzClass EFinverter for WPT, a150W 10MHzminiature Class E boostconverter, and a lightweight wirelessly powered drone using a20W 13.56MHzClass E synchronous rectifier have beendesigned and are presented here.
Lan L, Ting NM, Aldhaher S, et al., 2018, Foreign Object Detection for Wireless Power Transfer, 2nd URSI Atlantic Radio Science Meeting (AT-RASC), Publisher: IEEE
This paper proposes solutions for an IPT system to operate efficiently when large changes in coupling take place. To achieve high power-efficiency independent of coupling, we utilise inherent regulation properties of resonant converters to avoid losing soft switching for any coupling value, and present the optimal load to the IPT-link at the maximum energy-throughput coupling. A probability-based model is introduced to assess and optimise the IPT system by analysing coupling as a distribution in time, which depends on the dynamic behaviour of the wireless charging system. The proposed circuits are a Class D rectifier with a resistance compression network (RCN) in the receiving-end and a load-independent Class EF inverter in the transmitting-end. Experiments were performed at 6.78 and 13.56 MHz verifying high efficiency for dynamic coupling and variable load resistance. End-to-end efficiencies of up to 88% are achieved at a coil separation larger than one coil-radius for a system capable of supplying 150 W to the load, and the energy-efficiency was measured at 80% when performing a uniformly-distributed linear-misalignment of 0-12.5 cm, corresponding to a receiver moving at constant velocity over a transmitter without power throughput control.
Arteaga JM, Kkelis G, Aldhaher S, et al., 2018, Probability-based Optimisation for a Multi-MHz IPT System with Variable Coupling, IEEE PELS Workshop on Emerging Technologies - Wireless Power Transfer (Wow), Publisher: IEEE
Mitcheson PD, Kkelis G, Aldhaher S, et al., 2018, Power Electronics for Wireless Power Delivery in Synthetic Sensor Networks, 17th International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS), Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
Gadoue S, Chen K-W, Mitcheson P, et al., 2018, Electrochemical Impedance Spectroscopy State of Charge Measurement for Batteries using Power Converter Modulation, 9th International Renewable Energy Congress (IREC), Publisher: IEEE, ISSN: 2378-3435
Aldhaher S, Mitcheson PD, 2018, Sate-Space Modelling and Design of a 10MHz 180W Class E DC/DC Converter using WBG Devices, 33nd Annual IEEE Applied Power Electronics Conference and Exposition (APEC), Publisher: IEEE, Pages: 2918-2921, ISSN: 1048-2334
Arteaga Saenz J, Lan L, Aldhaher S, et al., A Multi-MHz IPT-link Developed for Load Characterisation at Highly Variable Coupling Factor, Wireless Power Transfer Conference
Ouda MHI, Mitcheson P, Clerckx B, Optimal Operation of Multi-Tone Waveforms inLow RF-Power Receivers, IEEE MTT-S Wireless Power Transfer Conference
Aldhaher S, Yates DC, Mitcheson PD, 2018, 13.56MHz 50W Load-Independent Synchronous Class E Rectifier using GaN devices for Space-Constrained Applications, IEEE Wireless Power Transfer Conference (WPTC), Publisher: IEEE, ISSN: 2474-0225
Mitcheson PD, Boyle D, Kkelis G, et al., 2017, Energy-Autonomous Sensing Systems Using Drones, 16th IEEE SENSORS CONFERENCE, Publisher: IEEE, Pages: 648-650, ISSN: 1930-0395
© 2017 IEEE. This paper describes the system concept and initial results for end-to-end energy-autonomous sensor systems using unmanned aerial vehicles (drones) as agents for power delivery to and data gathering from sensing devices. Such systems may be particularly useful for delay tolerant monitoring scenarios, where sensing devices may be deployed in remote, harsh conditions, often with sparse connectivity, long life and high reliability requirements. This paper discusses the latest advances in wireless power delivery that makes this it possible to fly wireless power delivery systems on drones that have little payload capability.
Pacini A, Costanzo A, Aldhaher S, et al., 2017, Load- and Position-Independent Moving MHz WPT System Based on GaN-Distributed Current Sources, IEEE Transactions on Microwave Theory and Techniques, Vol: 65, Pages: 5367-5376, ISSN: 0018-9480
This paper describes the modeling, analysis, and design of a complete (dc-to-dc) inductive wireless power transfer (WPT) system for industrial moving applications. The system operates at 6.78 MHz and delivers up to 150 W to a load moving along a linear path, providing a quasi-constant dc output voltage and maintaining a zero voltage switching operation, regardless of position and load, without any retuning or feedback. The inductive link consists of an array of stationary transmitting coils and a moving receiving coil whose length is optimized to achieve a constant coupling coefficient along the path. Each Tx coil is individually driven by a constant amplitude and phase sinusoidal current that is generated from a GaN-based coupled load-independent Class EF inverter. Two adjacent transmitters are activated at a given time depending on the receiver’s position; this effectively creates a virtual series connection between the two transmitting coils. The Rx coil is connected to a passive Class E rectifier that is designed to maintain a constant dc output voltage independent of its load and position. Extensive experimental results are presented to show the performance over different loading conditions and positions. A peak dc-to-dc efficiency of 80% is achieved at 100 W of dc output power and a dc output voltage variation of less than 5% is measured over a load range from 30 to 500 Ω . The work in this paper is foreseen as a design solution for a high-efficient, maintenance-free, and reliable WPT system for powering sliders and mass movers in industrial automation plants.
Douthwaite M, Koutsos E, Yates DC, et al., 2017, A thermally powered ISFET array for on-body pH measurement, IEEE Transactions on Biomedical Circuits and Systems, Vol: 11, Pages: 1324-1334, ISSN: 1932-4545
Recent advances in electronics and electrochemical sensors have led to an emerging class of next generation wearables, detecting analytes in biofluids such as perspiration. Most of these devices utilize ion-selective electrodes (ISEs) as a detection method; however, ion-sensitive field-effect transistors (ISFETs) offer a solution with improved integration and a low power consumption. This work presents a wearable, thermoelectrically powered system composed of an application-specific integrated circuit (ASIC), two commercial power management integrated circuits and a network of commercial thermoelectric generators (TEGs). The ASIC is fabricated in 0.35 μm CMOS and contains an ISFET array designed to read pH as a current, a processing module which averages the signal to reduce noise and encodes it into a frequency, and a transmitter. The output frequency has a measured sensitivity of 6 to 8 kHz/pH for a pH range of 7-5. It is shown that the sensing array and processing module has a power consumption 6 μW and, therefore, can be entirely powered by body heat using a TEG. Array averaging is shown to reduce noise at these low power levels to 104 μV (input referred integrated noise), reducing the minimum detectable limit of the ASIC to 0.008 pH units. The work forms the foundation and proves the feasibility of battery-less, on-body electrochemical for perspiration analysis in sports science and healthcare applications.
Douthwaite M, Koutsos E, Yates DC, et al., 2017, A Thermally Powered ISFET Array for On-Body pH Measurement., IEEE Trans. Biomed. Circuits and Systems, Vol: 11, Pages: 1324-1334
Lawson J, 2017, High frequency electromagnetic links for wireless power transfer
This thesis investigates inductive links used in wireless power transfer systems. Inductive power transfer can be used as a power delivery method for a variety of portable devices, from medical implants to electric vehicles and is gaining increased interest. The focus is on high quality factor coils and MHz operation, where accurate measurements are difficult to achieve. Fast models of all pertinent aspects of inductive power transfer systems for constant cross section coils are developed. These models are used to optimise a new coil winding pattern that aims to increase efficiency in volume constrained scenarios. Measurement systems are developed to measure coil Q factors in excess of 1,000. The prototype measurement systems are verified against models of that system, as well as finite element simulations of the coil under test. Shielding of inductive power transfer systems is then investigated. A structure typically used at GHz frequencies, the artificial magnetic conductor, is miniaturised as an alternative to conventional ferrite backed ground plane shielding. Finite element simulation shows this structure significantly improves link efficiency. The artificial magnetic conductor prototype does not result in a gain in efficiency expected, however it does display the properties expected of an artificial magnetic conductor, including increased coupling factor. Finally, an unconventional inductive power transfer system is presented where transmitter and receiver are up to 6m away from each other and of radically different size. This system provides mW level power to remote devices in a room, for example thermostats or e-ink displays. Conventional approaches to design do not consider the distortion of the magnetic field caused by metallic objects in the room. It was found that treating the system as a decoupled receiver and transmitter provides a better prediction of received power in real world environments.
Pacini A, Costanzo A, Aldhaher S, et al., 2017, Design of a Position-Independent End-to-End Inductive WPT link for Industrial Dynamic Systems, IEEE-Microwave-Theory-and-Techniques-Society International Microwave Symposium (IMS) / Session on Women in Microwaves (WIM), Publisher: IEEE, Pages: 1049-1052, ISSN: 0149-645X
Kim J, Clerckx B, Mitcheson PD, 2017, Prototyping and Experimentation of a Closed-Loop Wireless Power Transmission with Channel Acquisition and Waveform Optimization, IEEE Wireless Power Transfer Conference (WPTC), Publisher: IEEE, ISSN: 2474-0225
Kkelis G, Aldhaher S, Arteaga JM, et al., 2017, Hybrid Class-E Synchronous Rectifier for Wireless Powering of Quadcopters, IEEE Wireless Power Transfer Conference (WPTC), Publisher: IEEE, ISSN: 2474-0225
Aldhaher S, Mitcheson PD, Arteaga JM, et al., 2017, Light-Weight Wireless Power Transfer for Mid-Air Charging of Drones, 11th European Conference on Antennas and Propagation (EUCAP), Publisher: IEEE, Pages: 336-340, ISSN: 2164-3342
Kkelis G, Yates DC, Mitcheson PD, 2017, Class-E half-wave zero dv/dt rectifiers for inductive power transfer, IEEE Transactions on Power Electronics, Vol: 32, Pages: 8322-8337, ISSN: 1941-0107
This paper analyses and compares candidate zero dv/dt half-wave Class-E rectifier topologies for integration into multi-MHz inductive power transfer (IPT) systems. Furthermore, a hybrid Class-E topology comprising advantageous properties from all existing Class-E half-wave zero dv/dt rectifiers is analysed for the first time. From the analysis, it is shown that the hybrid Class-E rectifier provides an extra degree of design freedom which enables optimal IPT operation over a wider range of operating conditions. Furthermore, it is shown that by designing both the hybrid and the current driven rectifiers to operate below resonance provides a low deviation input reactance and inherent output voltage regulation with duty cycle allowing efficient IPT operation over wider dc load range than would otherwise be achieved. A set of case studies demonstrated the following performances: 1) For a constant dc load resistance, a receiving end efficiency of 95% was achieved when utilising the hybrid rectifier, with a tolerance in required input resistance of 2.4% over the tested output power range (50W to 200W). 2) For a variable dc load in the range of 100% to 10%, the hybrid and current driven rectifiers presented an input reactance deviation less than 2% of the impedance of the magnetising inductance of the inductive link respectively and receiving end efficiencies greater than 90%. 3) For a constant current in the receiving coil, both the hybrid and the current driven rectifier achieve inherent output voltage regulation in the order of 3% and 8% of the nominal value respectively, for a variable dc load range from 100% to 10%.
Allmen L, Bailleul G, Becker T, et al., 2017, Aircraft strain WSN powered by heat storage harvesting, IEEE Transactions on Industrial Electronics, Vol: 64, Pages: 7284-7292, ISSN: 0278-0046
The combination of ultra-low power wireless communications and energy harvesting enables the realization of autonomous Wireless Sensor Networks.Such networks can be usefully applied in commercialaircraft where wireless sensing solutions contribute to weight reduction and increased ease of installation and maintenance. This paper presents, for the first time, a complete energy autonomous wireless strain monitoring system for aircraft. The system is based on a multi-mode wireless TDMA MAC protocol that supports automatic configuration and a time-stamping accuracy better than 1 ms. The energy supply depends solely on an innovative thermoelectric energy harvester which takes advantage of the changes in environmental temperature during take-off and landing. The system was successfully integrated and passed the functional and flight-clearance tests that qualify it for use in a flight-test installation.
Rajaguru P, Bailey C, Lu H, et al., 2017, Co-Design/Simulation of Flip-Chip Assembly for High Voltage IGBT Packages, 23rd International Workshop on Thermal Investigations of ICs and Systems (THERMINIC), Publisher: IEEE
Boyle D, Kiziroglou ME, Mitcheson P, et al., 2016, Provision and storage of energy for pervasive computing, IEEE Pervasive Computing, Vol: 15, Pages: 28-35, ISSN: 1558-2590
Soon, pervasive computers will enormously outnumber humans. Devices requiring sufficient energy to operate maintenance-free for periods of years and beyond render today’s technologiesinsufficient. With the gap between energy requirements of embedded systems and achievable levels of harvested power reducing, viable hybrid energy and power management subsystems have emerged that combine harvesting with finite, rechargeable energy buffers. Coupled with advances in wireless power transfer and energy storage, we propose that an energy design space is emerging. There are, as yet, no tools or systematic methods for design space exploration or engineering in this context. It is important to develop such a methodology, and critical to link it with methodologies for system design and verification. We discuss the key factors such an energy design methodology should incorporate,including size, weight, energy and power densities; efficiencies of harvesters and buffers; time between charges, (dis)charge speeds, and charge cycles; and availability and predictability of harvestable energy.
Merlin MMC, mitcheson PD, 2016, Active power losses distribution methods for the modular multilevel converter, COMPEL 2016, Publisher: IEEE, ISSN: 1093-5142
Modular Converters such as the MMC have become the new standard in VSC-HVDC applications. Their modularity has brought many industrial advantages but also increased the complexity of their operation. This paper looks at how a range of techniques may alter the balance of power losses between the IGBT modules. These techniques are based on circulating currents at the (i) fundamental frequency and (ii) second harmonic and (iii) DC voltage offset on the converter voltage waveform. Finally, conclusions on the effectiveness and potential drawbacks of these techniques are discussed.
Mitcheson PD, Lucyszyn S, Pinuela M, et al., 2016, RF energy harvester, US9837865B2
Disclosed herein is an antenna apparatus for use in harvesting ambient radio frequency, RF, energy. The apparatus comprises one or more RF antenna components arranged to receive RF energy for producing electricity. The one or more RF antenna components comprise a plurality of frequency filtering components, each frequency filtering component being arranged to filter a respective frequency band of the received RF energy. Also disclosed herein is an apparatus comprising a rectifying circuit arranged to convert a variable electrical signal received at an input from an associated antenna into a direct current electrical signal for supplying to an electrical energy storage unit, the antenna for use in harvesting ambient radio frequency, RF, energy. The apparatus also comprises a power management module having an input arranged to receive the direct current and control supply of the direct current to the electrical energy storage unit. The rectifying circuit comprises a plurality of transmission lines, wherein the input of the rectifying circuit and the input of the power management module are connected via the plurality of transmission lines. The power management module is arranged at least partially within a boundary defined by the plurality of transmission lines.
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