7 research outputs found
Energy buffer dimensioning through energy-erlangs in spatio-temporal-correlated energy-harvesting-enabled wireless sensor networks
Energy-harvesting-enabled wireless sensor networks (EHE-WSN), despite their disruptive potential impact, still present several challenges precluding practical deployability. In particular, the low power density and random character of the ambient energy sources produce slow deep fadings in the energy that nodes harvest. Unfortunately, the capacity of the energy buffers is very limited, causing that, at some times, the node might interrupt its operation due to lack of stored energy. In this context, a general purpose framework for dimensioning the energy buffer is provided in this work. To achieve this, a dynamics-decoupled, multi-source capable energy model is presented, which can handle fast random patterns of the communications and the energy harvesting, while it can capture slow variations of the ambient energy in both time and space. By merging both dynamics, the model can more accurately evaluate the performance of the sensor node in terms of the energy storage capacity and to estimate the expected energy of the neighboring nodes. In order to evaluate the performance of the sensor node, a statistical unit for energy harvesting resources, referred as the Energy-Erlang (E2), has been defined. This unit provides a link between the energy model, the environmental harvested power and the energy buffer. The results motivate the study of the specific properties of the ambient energy sources before the design and deployment. By combining them in this general-purpose framework, electronics and network designers will have a powerful tool for optimizing resources in EHE-WSNs.Peer Reviewe
Energy buffer dimensioning through energy-erlangs in spatio-temporal-correlated energy-harvesting-enabled wireless sensor networks
Energy-harvesting-enabled wireless sensor networks (EHE-WSN), despite their disruptive potential impact, still present several challenges precluding practical deployability. In particular, the low power density and random character of the ambient energy sources produce slow deep fadings in the energy that nodes harvest. Unfortunately, the capacity of the energy buffers is very limited, causing that, at some times, the node might interrupt its operation due to lack of stored energy. In this context, a general purpose framework for dimensioning the energy buffer is provided in this work. To achieve this, a dynamics-decoupled, multi-source capable energy model is presented, which can handle fast random patterns of the communications and the energy harvesting, while it can capture slow variations of the ambient energy in both time and space. By merging both dynamics, the model can more accurately evaluate the performance of the sensor node in terms of the energy storage capacity and to estimate the expected energy of the neighboring nodes. In order to evaluate the performance of the sensor node, a statistical unit for energy harvesting resources, referred as the Energy-Erlang (E2), has been defined. This unit provides a link between the energy model, the environmental harvested power and the energy buffer. The results motivate the study of the specific properties of the ambient energy sources before the design and deployment. By combining them in this general-purpose framework, electronics and network designers will have a powerful tool for optimizing resources in EHE-WSNs.Peer Reviewe
A system-level methodology for the design and deployment of reliable low-power wireless sensor networks
Innovative Internet of Things (IoT) applications with strict performance and energy consumption requirements and where the agile collection of data is paramount are rousing. Wireless sensor networks (WSN) represent a promising solution as they can be easily deployed to sense, process, and forward data. The large number of Sensor Nodes (SNs) composing a WSN are expected to be autonomous, with a node's lifetime dictated by the battery's size. As the form factor of the SN is critical in various use cases such as industrial and building automation, minimizing energy consumption while ensuring availability becomes a priority. Moreover, energy harvesting techniques are increasingly considered as a viable solution for building an entirely green SN and prolonging its lifetime. In the process of building a SN and in the absence of a clear and well-rounded methodology, the designer can easily make unfounded decisions about the right hardware components, their configuration and data reliable data communication techniques such as automatic repeat request (ARQ) and forward error correction (FEC). In this thesis, a methodology to better optimize the design, configuration and deployment of reliable ultra-low power WSNs is proposed. Comprehensive and realistic energy and path-loss (PL) models of the sensor node are also established. Through estimations and measurements, it is shown that following the proposed methodology, the designer can thoroughly explore the design space and make most favorable decisions when choosing commercial off-the-shelf (COTS) components, configuring the node, and deploying a reliable and energy-efficient WSN
Multisensor wireless
El presente Trabajo Fin de Master versa sobre el estudio de la técnica, diseño e implementación de un nodo sensor inalámbrico capaz de capturar imagen, sonido, temperatura, humedad y presencia, de forma autónoma en cualquier estancia del hogar. La captura de todo el conjunto de datos que el sensor es capaz de capturar, permitirá, mediante un procesamiento individualizado o combinando los datos de varios senosres, definir la actividad que se está llevando a cabo en la estancia del hogar en la que ha sido instalado. Este nodo sensor también es capaz de enviar los datos capturados a través de un canal de comunicación inalámbrico a un concentrador, el cual se ocupe del tratado de datos o simplemente de almacenarlos. Con este envío de datos se consigue poder tener almacenados estos datos para su posterior consulta, así como poder procesar un conjunto de datos capturados por varios nodos sensores. Este dispositivo cuenta también con cierta capacidad de procesamiento, así como una buena eficiencia energética con el fin de alargar al máximo posible la vida útil del nodo sensor determinada por la capacidad de la batería. Podrán emplearse técnicas de “energy harvesting” con el fin de poder recoger energía del entorno, como por ejemplo de luz solar, para recargar las baterías. La finalidad última de este nodo sensor inalámbrico es la monitorización de la actividad en el hogar de personas enfermas con problemas o trastornos de memoria. Con los datos de esta monitorización se pretende ser capaces de detectar que estos enfermos dejan de realizar ciertos hábitos. También servirá para que los enfermos puedan acceder a los datos almacenados de su actividad diaria. Este Trabajo Fin de Master se enmarca dentro del proyecto de investigación titulado MEMORY LANE en el que participa el grupo de investigación HOWLab de la Universidad de Zaragoza. Este proyecto pretende crear un “life-blog” para personas ancianas susceptibles de padecer problemas de memoria, permitiéndoles acceder al contenido del mismo en función de su contexto
On-chip adaptive power management for WPT-Enabled IoT
Internet of Things (IoT), as broadband network connecting every physical objects, is becoming more widely available in various industrial, medical, home and automotive applications. In such network, the physical devices, vehicles, medical assistance, and home appliances among others are supposed to be embedded by sensors, actuators, radio frequency (RF) antennas, memory, and microprocessors, such that these devices are able to exchange data and connect with other devices in the network. Among other IoT’s pillars, wireless sensor network (WSN) is one of the main parts comprising massive clusters of spatially distributed sensor nodes dedicated for sensing and monitoring environmental conditions. The lifetime of a WSN is greatly dependent on the lifetime of the small sensor nodes, which, in turn, is primarily dependent on energy availability within every sensor node. Predominantly, the main energy source for a sensor node is supplied by a small battery attached to it. In a large WSN with massive number of deployed sensor nodes, it becomes a challenge to replace the batteries of every single sensor node especially for sensor nodes deployed in harsh environments. Consequently, powering the sensor nodes becomes a key limiting issue, which poses important challenges for their practicality and cost.
Therefore, in this thesis we propose enabling WSN, as the main pillar of IoT, by means of resonant inductive coupling (RIC) wireless power transfer (WPT). In order to enable efficient energy delivery at higher range, high quality factor RIC-WPT system is required in order to boost the magnetic flux generated at the transmitting coil. However, an adaptive front-end is essential for self-tuning the resonant tank against any mismatch in the components values, distance variation, and interference from close metallic objects. Consequently, the purpose of the thesis is to develop and design an adaptive efficient switch-mode front-end for self-tuning in WPT receivers in multiple receiver system.
The thesis start by giving background about the IoT system and the technical bottleneck followed by the problem statement and thesis scope. Then, Chapter 2 provides detailed backgrounds about the RIC-WPT system. Specifically, Chapter 2 analyzes the characteristics of different compensation topologies in RIC-WPT followed by the implications of mistuning on efficiency and power transfer capability. Chapter 3 discusses the concept of switch-mode gyrators as a potential candidate for generic variable reactive element synthesis while different potential applications and design cases are provided. Chapter 4 proposes two different self-tuning control for WPT receivers that utilize switch-mode gyrators as variable reactive element synthesis. The performance aspects of control approaches are discussed and evaluated as well in Chapter 4. The development and exploration of more compact front-end for self-tuned WPT receiver is investigated in Chapter 5 by proposing a phase-controlled switched inductor converter. The operation and design details of different switch-mode phase-controlled topologies are given and evaluated in the same chapter. Finally, Chapter 6 provides the conclusions and highlight the contribution of the thesis, in addition to suggesting the related future research topics.Internet de las cosas (IoT), como red de banda ancha que interconecta cualquier cosa, se está estableciendo como una tecnología valiosa en varias aplicaciones industriales, médicas, domóticas y en el sector del automóvil. En dicha red, los dispositivos físicos, los vehículos, los sistemas de asistencia médica y los electrodomésticos, entre otros, incluyen sensores, actuadores, subsistemas de comunicación, memoria y microprocesadores, de modo que son capaces de intercambiar datos e interconectarse con otros elementos de la red. Entre otros pilares que posibilitan IoT, la red de sensores inalámbricos (WSN), que es una de las partes cruciales del sistema, está formada por un conjunto masivo de nodos de sensado distribuidos espacialmente, y dedicados a sensar y monitorizar las condiciones del contexto de las cosas interconectadas. El tiempo de vida útil de una red WSN depende estrechamente del tiempo de vida de los pequeños nodos sensores, los cuales, a su vez, dependen primordialmente de la disponibilidad de energía en cada nodo sensor. La fuente principal de energía para un nodo sensor suele ser una pequeña batería integrada en él. En una red WSN con muchos nodos y con una alta densidad, es un desafío el reemplazar las baterías de cada nodo sensor, especialmente en entornos hostiles, como puedan ser en escenarios de Industria 4.0. En consecuencia, la alimentación de los nodos sensores constituye uno de los cuellos de botella que limitan un despliegue masivo práctico y de bajo coste. A tenor de estas circunstancias, en esta tesis doctoral se propone habilitar las redes WSN, como pilar principal de sistemas IoT, mediante sistemas de transferencia inalámbrica de energía (WPT) basados en acoplamiento inductivo resonante (RIC). Con objeto de posibilitar el suministro eficiente de energía a mayores distancias, deben aumentarse los factores de calidad de los elementos inductivos resonantes del sistema RIC-WPT, especialmente con el propósito de aumentar el flujo magnético generado por el inductor transmisor de energía y su acoplamiento resonante en recepción. Sin embargo, dotar al cabezal electrónico que gestiona y condicionada el flujo de energía de capacidad adaptativa es esencial para conseguir la autosintonía automática del sistema acoplado y resonante RIC-WPT, que es muy propenso a la desintonía ante desajustes en los parámetros nominales de los componentes, variaciones de distancia entre transmisor y receptores, así como debido a la interferencia de objetos metálicos. Es por tanto el objetivo central de esta tesis doctoral el concebir, proponer, diseñar y validar un sistema de WPT para múltiples receptores que incluya funciones adaptativas de autosintonía mediante circuitos conmutados de alto rendimiento energético, y susceptible de ser integrado en un chip para el condicionamiento de energía en cada receptor de forma miniaturizada y desplegable de forma masiva. La tesis empieza proporcionando una revisión del estado del arte en sistemas de IoT destacando el reto tecnológico de la alimentación energética de los nodos sensores distribuidos y planteando así el foco de la tesis doctoral. El capítulo 2 sigue con una revisión crítica del statu quo de los sistemas de transferencia inalámbrica de energía RIC-WPT. Específicamente, el capítulo 2 analiza las características de diferentes estructuras circuitales de compensación en RIC-WPT seguido de una descripción crítica de las implicaciones de la desintonía en la eficiencia y la capacidad de transferencia energética del sistema. El capítulo 3 propone y explora el concepto de utilizar circuitos conmutados con función de girador como potenciales candidatos para la síntesis de propósito general de elementos reactivos variables sintonizables electrónicamente, incluyendo varias aplicaciones y casos de uso. El capítulo 4 propone dos alternativas para métodos y circuitos de control para la autosintonía de receptores de energíaPostprint (published version
Silicon carbide based DC-DC converters for deployment in hostile environments
PhD ThesisThe development of power modules for deployment in hostile environments,
where the elevated ambient temperatures demand high temperature capability of the
entire converter system, requires innovative power electronic circuits to meet stringent
requirements in terms of efficiency, power-density and reliability. To simultaneously
meet these conflicting requirements in extreme environment applications is quite
challenging. To realise these power modules, the relevant control circuitry also needs to
operate at elevated temperatures. The recent advances in silicon carbide devices has
allowed the realisation of not just high frequency, high efficiency power converters, but
also the power electronic converters that can operate at elevated temperatures, beyond
those possible using conventional silicon-based technology.
High power-density power converters are key components for power supply
systems in applications where space and weight are critical parameters. The demand for
higher power density requires the use of high-frequency DC-DC converters to overcome
the increase in size and power losses due to the use of transformers. The increase in
converter switching frequency reduces the size of passive components whilst increasing
the electromagnetic interference (EMI) emissions.
A performance comparison of SiC MOSFETs and JFETs in a high-power
DC-DC converter to form part of a single phase PV inverter system is presented. The
drive design requirements for optimum performance in the energy conversion system
are also detailed. The converter was tested under continuous conduction mode at
frequencies up to 250 kHz. The converter power efficiency, switch power loss and
temperature measurements are then compared with the ultra-high speed CoolMOS
switches and SiC diodes. The high voltage, high frequency and high temperature
operation capability of the SiC DUTs are also demonstrated. The all SiC converters
showed more stable efficiencies of 95.5% and 96% for the switching frequency range
for the SiC MOSFET and JFET, respectively. A comparison of radiated noise showed
the highest noise signature for the SiC JFET and lowest for the SiC MOSFET. The
negative gate voltage requirement of the SiC MOSFET introduces up to 6 dBμV
increase in radiated noise, due to the induced current in the high frequency resonant
stray loop in the gate drive negative power plane.
ii
A gate driver is an essential part of any power electronic circuitry to control the
switching of the power semiconductor devices. The desire to place the gate driver
physically close to the power switches in the converter, leads to the necessity of a
temperature resilient PWM generator to control the power electronics module. At
elevated temperatures, the ability to control electrical systems will be a key enabler for
future technology enhancements.
Here an SiC/SOI-based PWM gate driver is proposed and designed using a
current source technique to accomplish variable duty-cycle PWM generation. The ring
oscillator and constant current source stages use low power normally-on, epitaxial
SiC-JFETs fabricated at Newcastle University. The amplification and control stages use
enhancement-mode signal SOI MOSFETs. Both SOI MOSFETs will be replaced by
future high current SiC-JFETs with only minor modification to the clamp-stage circuit
design. In the proposed design, the duty cycle can be varied from 10% to 90%. The
PWM generator is then evaluated in a 200 kHz step-up converter which results in a 91%
efficiency at 81% duty cycle.
High temperature environments are incompatible with standard battery
technologies, and so, energy harvesting is a suitable technology when remote
monitoring of these extreme environments is performed through the use of wireless
sensor nodes. Energy harvesting devices often produce voltages which are unusable
directly by electronic loads and so require power management circuits to convert the
electrical output to a level which is usable by monitoring electronics and sensors.
Therefore a DC-DC step-up converter that can handle low input voltages is required.
The first demonstration of a novel self-starting DC-DC converter is reported, to
supply power to a wireless sensor node for deployment in high temperature
environments. Utilising SiC devices a novel boost converter topology has been realised
which is suitable for boosting a low voltage to a level sufficient to power a sensor node
at temperatures up to 300 °C. The converter operates in the boundary between
continuous and discontinuous mode of operation and has a VCR of 3 at 300 °C. This
topology is able to self start and so requires no external control circuitry, making it ideal
for energy harvesting applications, where the energy supply may be intermittent.EPSRC and BAE
SYSTEMS through the Dorothy Hodgkin Postgraduate Awar