Wireless sensor system for infrastructure health monitoring

In this thesis, radio frequency identification (RFID)-based wireless sensor system for infrastructure health monitoring (IHM) is designed and developed. It includes mountable semi-passive tag antenna integrated sensors capable of measuring critical responses of infrastructure such as dynamic acceleration and strain. Furthermore, the system is capable of measuring structural displacement. One of the most important parts of this system is the relatively small, tunable, construction material mountable RFID tag antenna. The tag antenna is electronically integrated with the sensors. Leading to the process of developing tag antenna integrated sensors having satisfactory wireless performance (sensitivity and read range) when mounted on concrete and metal structural members, the electromagnetic performance of the tag antenna is analyzed and optimized using both numerical and experimental procedures. Subsequently, it is shown that both the simulation and the experimental measurement results are in good agreement. The semi-passive RFID-based system is implemented in a wireless IHM system with multiple sensor points to measure dynamic acceleration and strain. The developed system can determine the natural frequencies of infrastructure and identify any state changes of infrastructure by measuring natural frequency shifts. Enhancement of the spectral bandwidth of the system has been performed under the constraints of the RFID hardware. The influence of the orientation and shape of the structural members on wireless power flow in the vicinity of those members is also investigated with the RFID reader-tag antenna system in both simulation and experiments. The antenna system simulations with a full-scale structural member have shown that both the orientation and the shape of the structural member influence the wireless power flow towards and in the vicinity of the member, respectively. The measurement results of the conducted laboratory experiments using the RFID antenna system in passive mode have shown good agreement with simulation results. Furthermore, the system’s ability to measure structural displacement is also investigated by conducting phase angle of arrival measurements. It is shown that the system in its passive mode is capable of measuring small structural displacements within a short wireless distance. The benchmarking of the developed system with independent, commercial, wired and wireless measurement systems has confirmed the ability of the RFID-based system to measure dynamic acceleration and strain. Furthermore, it has confirmed the system’s ability to determine the natural frequency of an infrastructure accurately. Therefore, the developed system with wireless sensors that do not consume battery power in data transmission and with the capability of dynamic response measurement is highly applicable in IHM

Battery-less near field communications (nfc) sensors for internet of things (iot) applications

L’ implementació de la tecnologia de comunicació de camp proper (NFC) en els telèfons intel·ligents no para de créixer degut a l’ús d’aquesta per fer pagaments, això, junt amb el fet de poder aprofitar l’energia generada pel mòbil no només per la comunicació, sinó també per transmetre energia, el baix cost dels xips NFC, i el fet de que els telèfons tinguin connectivitat amb internet, possibilita i fa molt interesant el disseny d’etiquetes sense bateria incorporant-hi sensors i poder enviar la informació al núvol, dins del creixent escenari de l’internet de les coses (IoT). La present Tesi estudia la viabilitat d’aquests sensors, analitzant la màxima distància entre lector i sensor per proveir la potència necessària, presenta tècniques per augmentar el rang d’operació, i analitza els efectes de certs materials quan aquests estan propers a les antenes. Diversos sensors han estat dissenyats i analitzats i son presentats en aquest treball. Aquests son: Una etiqueta que mesura la humitat de la terra, la temperatura i la humitat relativa de l’aire per controlar les condicions de plantes. Un sensor per detectar la humitat en bolquers, imprès en material flexible que s’adapta a la forma del bolquer. Dues aplicacions, una per estimació de pH i una altre per avaluar el grau de maduració de fruites, basats en un sensor de color. I, per últim, s’estudia la viabilitat de sensors en implants per aplicacions mèdiques, analitzant l’efecte del cos i proposant un sistema per augmentar la profunditat a la que aquests es poden llegir utilitzant un telèfon mòbil. Tots aquests sensors poden ser alimentats i llegits per qualsevol dispositiu que disposin de connexió NFC.La implementación de la tecnología de comunicaciones de campo cercano (NFC) en los teléfonos inteligentes no para de crecer debido al uso de esta para llevar a cabo pagos, esto, junto con el hecho de poder aprovechar la energía generada por el móvil no sólo para la comunicación, sino también para transmitir energía, el bajo coste de los chips NFC, i el hecho que los teléfonos tengan conectividad a internet, posibilita y hace muy interesante el diseño de etiquetas sin batería que incorporen sensores i poder enviar la información a la nube, enmarcado en el creciente escenario del internet de las cosas (IoT). La presente Tesis estudia la viabilidad de estos sensores, analizando la máxima distancia entre lector i sensor para proveer la potencia necesaria, presenta técnicas para aumentar el rango de operación, y analiza los efectos de ciertos materiales cuando estos están cerca de las antenas. Varios sensores han sido diseñados y analizados y son presentados en este trabajo. Estos son: Una etiqueta que mide la humedad de la tierra, la temperatura y la humedad relativa del aire para controlar las condiciones de plantas. Un sensor para detectar la humedad en pañales, impreso en material flexible que se adapta a la forma del pañal. Dos aplicaciones, una para estimación de pH y otra para evaluar el grado de maduración de frutas, basados en un sensor de color. Y, por último, se estudia la viabilidad de sensores en implantes para aplicaciones médicas, analizando el efecto del cuerpo y proponiendo un sistema para aumentar la profundidad a la que estos se pueden leer usando un teléfono móvil. Todos estos sensores pueden ser alimentados y leídos por cualquier dispositivo que disponga de conexión NFC.The implementation of near field communication (NFC) technology into smartphones grows rapidly due the use of this technology as a payment system. This, altogether with the fact that the energy generated by the phone can be used not only to communicate but for power transfer as well, the low-cost of the NFC chips, and the fact that the smartphones have connectivity to internet, makes possible and very interesting the design of battery-less sensing tags which information can be sent to the cloud, within the growing internet of things (IoT) scenario. This Thesis studies the feasibility of these sensors, analysing the maximum distance between reader and sensor to provide the necessary power, presents techniques to increase the range of operation, and analyses the effects of certain materials when they are near to the antennas. Several sensors have been designed and analysed and are presented in this work. These are: a tag that measures the soil moisture, the temperature and the relative humidity of the air to control the conditions of plants. A moisture sensor for diapers, printed on flexible material that adapts to the diaper shape. Two applications, one for pH estimation and another for assessing the degree of fruit ripening, based on a colour sensor. And finally, the feasibility of sensors in implants for medical applications is studied, analysing the effect of the body and proposing a system to increase the depth at which they can be read using a mobile phone. All of these sensors can be powered and read by any NFC enabled device

Autonomous Sensing Nodes for IoT Applications

The present doctoral thesis fits into the energy harvesting framework, presenting the development of low-power nodes compliant with the energy autonomy requirement, and sharing common technologies and architectures, but based on different energy sources and sensing mechanisms. The adopted approach is aimed at evaluating multiple aspects of the system in its entirety (i.e., the energy harvesting mechanism, the choice of the harvester, the study of the sensing process, the selection of the electronic devices for processing, acquisition and measurement, the electronic design, the microcontroller unit (MCU) programming techniques), accounting for very challenging constraints as the low amounts of harvested power (i.e., [μW, mW] range), the careful management of the available energy, the coexistence of sensing and radio transmitting features with ultra-low power requirements. Commercial sensors are mainly used to meet the cost-effectiveness and the large-scale reproducibility requirements, however also customized sensors for a specific application (soil moisture measurement), together with appropriate characterization and reading circuits, are also presented. Two different strategies have been pursued which led to the development of two types of sensor nodes, which are referred to as 'sensor tags' and 'self-sufficient sensor nodes'. The first term refers to completely passive sensor nodes without an on-board battery as storage element and which operate only in the presence of the energy source, provisioning energy from it. In this thesis, an RFID (Radio Frequency Identification) sensor tag for soil moisture monitoring powered by the impinging electromagnetic field is presented. The second term identifies sensor nodes equipped with a battery rechargeable through energy scavenging and working as a secondary reserve in case of absence of the primary energy source. In this thesis, quasi-real-time multi-purpose monitoring LoRaWAN nodes harvesting energy from thermoelectricity, diffused solar light, indoor white light, and artificial colored light are presented

Low power wireless technologies for AC current sensing

This thesis is concerned with the development of a novel RFID ac current sensing technique for smart power monitoring systems. The research aims to explore designing self-tuning RFID tags and antenna designs and transforming simple tags into passive ac current sensors.The sensing mechanism by which a self-tuning RFID tag is linked with a varactor tuning circuit and integrated into a current transformer is described. The proposed sensing tag structure is less complex and provides a cost-effective solution for power monitoring when many tags on individual appliances communicate wirelessly with a centrally mounted single RFID reader in the views of the tags to be read.New optimised RFID tag antenna designs for a current transformer are introduced. Antenna miniaturisation techniques are adopted in designing tag antennas to achieve compact physical integration with the transformer housing while maintaining the tag link. These optimisedtag antennas are designed in order to reduce the size of the tag system.The proposed current sensing concept is further explored to utilise two tag antennas in a single design. The two tag antennas are coupled with different tuning circuits and integrated into a single transformer for increasing the current sensing range of the sensor. The antenna design techniques of designing two tag antennas in close proximity with each other and how the mutual coupling between the tag antennas can be reduced are also studied

DIEstro: Motion sensor platform for cattle oestrus detection

The reproductive efficiency of dairy industry has decreased over the last ten years due mainly to an intensification of the management techniques of the herd, and an increase of total number of animals. A main objective of worldwide dairy farms is to ensure that dairy cows, produce as much milk as possible. A cow produces milk while it has a calf to breastfeed, therefore, the less time passes between births, the more ”productive” the cows are. This is the principal reason why the precise heat (oestrus) detection has became so important, a task traditionally assigned to veterinary and expert people examining and watching the cattle behavior, and in recent years to electronic devices monitoring the cow’s physical activity. Tracking the animal’s physical activity by means of a portable device strapped to each animal, is known to be a very effective way to determine heat, but sometimes requires expensive hardware and large batteries. In this work, a low-cost micropower wireless system able to automatically detect oestrus period of cattle is presented. It was designed in cooperation with BQN, a company developing technology for the agribusiness industry in Uruguay. The tracker seizes the recent availability of 1 uA micropower accelerometers, LoRa long range transceivers, and FRAM microcontrollers, to achieve a coin cell battery powered paradigm for oestrus detection. The device records 3 axis acceleration information, process it, and periodically sends it to a server; it has a measured ultra low power consumption of 4 uA while collecting/processing data, reaching a very large (> 10km) communication distance using a star topology and LoRa technology at countryside areas. The scope of the project and this documentation is the entire hardware and firmware development, from the start idea, design and final implementation.Agencia Nacional de Investigación e Innovació

DIEstro: Motion sensor platform for cattle oestrus detection

The reproductive efficiency of dairy industry has decreased over the last ten years due mainly to an intensification of the management techniques of the herd, and an increase of total number of animals. A main objective of worldwide dairy farms is to ensure that dairy cows, produce as much milk as possible. A cow produces milk while it has a calf to breastfeed, therefore, the less time passes between births, the more ”productive” the cows are. This is the principal reason why the precise heat (oestrus) detection has became so important, a task traditionally assigned to veterinary and expert people examining and watching the cattle behavior, and in recent years to electronic devices monitoring the cow’s physical activity. Tracking the animal’s physical activity by means of a portable device strapped to each animal, is known to be a very effective way to determine heat, but sometimes requires expensive hardware and large batteries. In this work, a low-cost micropower wireless system able to automatically detect oestrus period of cattle is presented. It was designed in cooperation with BQN, a company developing technology for the agribusiness industry in Uruguay. The tracker seizes the recent availability of 1 uA micropower accelerometers, LoRa long range transceivers, and FRAM microcontrollers, to achieve a coin cell battery powered paradigm for oestrus detection. The device records 3 axis acceleration information, process it, and periodically sends it to a server; it has a measured ultra low power consumption of 4 uA while collecting/processing data, reaching a very large (> 10km) communication distance using a star topology and LoRa technology at countryside areas. The scope of the project and this documentation is the entire hardware and firmware development, from the start idea, design and final implementation.Agencia Nacional de Investigación e Innovació

Chemicapacitors as a versatile platform for miniature gas and vapor sensors

Recent years have seen the rapid growth in the need for sensors throughout all areas of society including environmental sensing, health-care, public safety and manufacturing quality control. To meet this diverse need, sensors have to evolve from specialized and bespoke systems to miniaturized, low-power, low-cost (almost disposable) ubiquitous platforms. A technology that has been developed which gives a route to meet these challenges is the chemicapacitor sensor. To date the commercialization of these sensors has largely been restricted to humidity sensing, but in this review we examine the progress over recent years to expand this sensing technology to a wide range of gases and vapors. From sensors interrogated with laboratory instrumentation, chemicapacitor sensors have evolved into miniaturized units integrated with low power readout electronics that can selectively detect target molecules to ppm and sub-ppm levels within vapor mixtures

Application of Ultra-Wideband Technology to RFID and Wireless Sensors

Aquesta Tesi Doctoral estudia l'ús de tecnologia de ràdio banda ultraampla (UWB) per sistemes de identificació per radiofreqüència (RFID) i sensors sense fils. Les xarxes de sensors sense fils (WSNs), ciutats i llars intel•ligents, i, en general, l'Internet de les coses (IoT) requereixen interfícies de ràdio simples i de baix consum i cost per un número molt ampli de sensors disseminats. UWB en el domini temporal es proposa aquí com una tecnologia de radio habilitant per aquestes aplicacions. Un model circuital s'estudia per RFID d'UWB codificat en el temps. Es proposen lectors basats en ràdars polsats comercials amb tècniques de processat de senyal. Tags RFID sense xip (chipless) codificats en el temps son dissenyats i caracterizats en termes de número d'identificacions possible, distància màxima de lectura, polarització, influència de materials adherits, comportament angular i corbatura del tag. Es proposen sensors chipless de temperatura i composició de ciment (mitjançant detecció de permitivitat). Dos plataformes semipassives codificades en temps (amb un enllaç paral•lel de banda estreta per despertar el sensor i estalviar energia) es proposen com solucions més complexes i robustes, amb una distància de lectura major. Es dissenya un sensor de temperatura (alimentat per energia solar) i un sensor de diòxid de nitrogen (mitjançant nanotubs de carboni i alimentat per una petita bateria), ambdòs semipassius amb circuiteria analògica. Es dissenya un multi-sensor semipassiu capaç de mesurar temperatura, humitat, pressió i acceleració, fent servir un microcontrolador de baix consum digital. Combinant els tags RFID UWB codificats en temps amb tecnologia de ràdar de penetració del terra (GPR), es deriva una aplicació per localització en interiors amb terra intel•ligent. Finalment, dos sistemes actius RFID UWB codificats en el temps s'estudien per aplicacions de localització de molt llarg abast.Esta Tesis Doctoral estudia el uso de tecnología de radio de banda ultraancha (UWB) para sistemas de identificación por radiofrecuencia (RFID) y sensores inalámbricos. Las redes de sensores inalámbricas (WSNs), ciudades y casas inteligentes, y, en general, el Internet de las cosas (IoT) requieren de interfaces de radio simples y de bajo consumo y coste para un número muy amplio de sensores diseminados. UWB en el dominio temporal se propone aquí como una tecnología de radio habilitante para dichas aplicaciones. Un modelo circuital se estudia para RFID de UWB codificado en tiempo. Configuraciones de lector, basadas en rádar pulsados comerciales, son propuestas, además de técnicas de procesado de señal. Tags RFID sin chip (chipless) codificados en tiempo son diseñados y caracterizados en términos de número de identificaciones posible, distancia máxima de lectura, polarización, influencia de materiales adheridos, comportamiento angular y curvatura del tag. Se proponen sensores chipless de temperatura y composición de cemento (mediante detección de permitividad). Dos plataformas semipasivas codificadas en tiempo (con un enlace paralelo de banda estrecha para despertar el sensor y ahorrar energía) se proponen como soluciones más complejas y robustas, con una distancia de lectura mayor. Se diseña un sensor de temperatura (alimentado por energía solar) y un sensor de dióxido de nitrógeno (mediante nanotubos de carbono y alimentado por una batería pequeña), ambos semipasivos con circuitería analógica. Se diseña un multi-sensor semipasivo capaz de medir temperatura, humedad, presión y aceleración, usando un microcontrolador digital de bajo consumo. Combinando los tags RFID UWB codificados en tiempo y tecnología de radar de penetración de suelo (GPR), se deriva una aplicación para localización en interiores con suelo inteligente. Finalmente, dos sistemas activos RFID UWB codificados en tiempo se estudian para aplicaciones de localización de muy largo alcance.This Doctoral Thesis studies the use of ultra-wideband (UWB) radio technology for radio-frequency identification (RFID) and wireless sensors. Wireless sensor networks (WSNs) for smart cities, smart homes and, in general, Internet of Things (IoT) applications require low-power, low-cost and simple radio interfaces for an expected very large number of scattered sensors. UWB in time domain is proposed here as an enabling radio technology. A circuit model is studied for time-coded UWB RFID. Reader setups based on commercial impulse radars are proposed, in addition to signal processing techniques. Chipless time-coded RFID tags are designed and characterized in terms of number of possible IDs, maximum reading distance, polarization, influence of attached materials, angular behaviour and bending. Chipless wireless temperature sensors and chipless concrete composition sensors (enabled by permittivity sensing) are proposed. Two semi-passive time-coded RFID sensing platforms are proposed as more complex, more robust, and longer read-range solutions. A wake-up link is used to save energy when the sensor is not being read. A semi-passive wireless temperature sensor (powered by solar energy) and a wireless nitrogen dioxide sensor (enabled with carbon nanotubes and powered by a small battery) are developed, using analog circuitry. A semi-passive multi-sensor tag capable of measuring temperature, humidity, pressure and acceleration is proposed, using a digital low-power microcontroller. Combining time-coded UWB RFID tags and ground penetrating radar, a smart floor application for indoor localization is derived. Finally, as another approach, two active time-coded RFID systems are developed for very long-range applications

Intelligent Sensor Networks

In the last decade, wireless or wired sensor networks have attracted much attention. However, most designs target general sensor network issues including protocol stack (routing, MAC, etc.) and security issues. This book focuses on the close integration of sensing, networking, and smart signal processing via machine learning. Based on their world-class research, the authors present the fundamentals of intelligent sensor networks. They cover sensing and sampling, distributed signal processing, and intelligent signal learning. In addition, they present cutting-edge research results from leading experts

Wake-up radio systems : design, development, performance evaluation and comparison to conventional medium access control protocols for wireless sensor networks

During the recent years, the research related to Wake-up Radio (WuR) systems has gained noticeable interest. In WuR systems, a node initiating a communication first sends a Wake-up Call (WuC) by means of its Wake-up Transmitter (WuTx), to the Wake-up Receiver (WuRx) of a remote node to activate it in an on-demand manner. Until the reception of the WuC, the node's MCU and main data transceiver are in sleep mode. Hence, WuR drastically reduce the power required by wireless nodes. This thesis provides a complete analysis of several WuR designs vs. conventional MAC protocols for Wireless Sensor Networks (WSN). The research is performed in an incremental fashion and includes hardware, softwar and simulation topics. WuR systems enable energy savings in plenty of different applications, e.g., retrieving information from environmental pollution sensors placed in a city by a mobile collector node, or activating a sleeping wireless AP. They are easy to program in and provide implicit synchronization. However, achieving a good WuRx design may become a challenge because power amplifiers cannot be used for the sake of energy. The system proposed in chapter 2 is a successful WuR system prototype. The so-called SµA-WuRx is less complex than commercial WuR systems, it is cheaper from the monetary point of view, requires several times less energy and allows for up to 15 meters of communication, an adequate value for WuR systems. However, the system can be improved by including several desirable features, such as longer operational ranges and/or addressing mechanisms. The so-called Time-Knocking (TicK) addressing strategy, analyzed in chapter 3, enables energy efficient node addressing by varying the time between WuCs received by a MCU. TicK allows for variable length addresses and multicast. A WuR system may not fit any possible application. Thus, while the SµA-WuRx and TicK efficiently solved many of the requirements of single-hop and data-collector applications, they lack of flexibility. Instead, SCM-WuR systems in chapter 4 feature an outstanding trade-off between hardware complexity, current consumption and operational range, and even enable multi-hop wake-up for long remote sensor measure collection. To contextualize the WuR systems developed, chapter 5 provides an overview of the most important WuR systems as of 2014. Developing a MAC protocol which performs acceptably in a wide range of diverse applications is a very difficult task. Comparatively, SCM-WuR systems perform properly in all the use cases (single and multi-hop) presented in chapter 6. Bluetooth Low Energy, or BLE, appears as a duty-cycled MAC protocol mainly targeting single-hop applications. Because of its clearly defined use cases and its integration with its upper application layers, BLE appears as an extremely energy-efficient protocol that cannot be easily replaced by WuR. Because of all these aspects, the performance of BLE is analyzed in chapter 7. Finally, chapter 8 tries to solve one of the issues affecting WuR systems, that is, the need for extra hardware. While this issue seems difficult to solve for WuRx, the chapter provides ideas to use IEEE 802.11-enabled devices as WuTx.Durant els últims anys, la investigació relativa als sistemes de Ràdios de Wake-up (de l'anglès Wake-up Radio, WuR) ha experimentat un interès notable. En aquests sistemes, un node inicia la comunicació inal.làmbrica transmetent una Wake-up Call (WuC), per mitjà del seu transmissor de Wake-up (WuTx), dirigida al receptor de Wake-up (WuRx) del node remot. Aquesta WuC activa el node remot, el microcontrolador (MCU) i la ràdio principals del qual han pogut romandre en mode "sleep" fins el moment. Així doncs, els sistemes WuR permeten un estalvi dràstic de l'energia requerida pels nodes sense fils. Aquesta tesi proposa diferents sistemes WuR i els compara amb protocols MAC existents per a xarxes de sensors sense fils (Wireless Sensor Networks, WSN). La investigació es realitza de forma progressiva i inclou hardware, software i simulació. Els sistemes WuR permeten un estalvi energètic notable en moltes aplicacions: recol¿lecció d'informació ambiental, activació remota de punts d'accés wi-fi, etc. Són fàcils de programar en software i comporten una sincronització implícita entre nodes. Malauradament, un consum energètic mínim impossibilita l'ús d'amplificadors de potència, i dissenyar-los esdevé un repte. El sistema presentat en el capítol 2 és un prototip exitós de sistema WuR. De nom SµA-WuR, és més senzill que alternatives comercials, és més econòmic, requereix menys energia i permet distàncies de comunicació WuR majors, de fins a 15 metres. L'estratègia d'adreçament Time-KnocKing, presentada en el capítol 3, permet dotar l'anterior SµA-WuR d'una forma d'especificar el node adreçat, permetent estalvi energètic a nivell de xarxa. TicK opera codificant el temps entre diferents WuC. Depenent del temps entre intervals, es desperten el/s node/s desitjats d'una forma extremadament eficient. Tot i els seus beneficis, hi ha aplicacions no implementables amb el sistema SµA-WuR. Per a aquest motiu, en el capítol 4 es presenta el sistema SCM-WuR, que ofereix un rang d'operació de 40 a 100 metres a canvi d'una mínima complexitat hardware afegida. SCM-WuR cobreix el ventall d'aplicacions del sistema SµA-WuRx, i també les que requereixen multi-hop a nivell WuR. El capítol 5 de la tesi compara els dos sistemes WuR anteriors vers les propostes més importants fins el 2014. El capítol 6 inclou un framework de simulació complet amb les bases per a substituir els sistemes basats en duty-cycling a WuR. Degut a que desenvolupar un protocol MAC que operi acceptablement bé en multitud d'aplicacions esdevé una tasca pràcticament impossible, els sistemes WuR presentats amb anterioritat i modelats en aquest capítol representen una solució versàtil, interessant i molt més eficient des del punt de vista energètic. Bluetooth Low Energy, o Smart, o BLE, representa un cas d'aplicació específica on, degut a la gran integració a nivell d'aplicació, la substitució per sistemes de WuR esdevé difícil Per a aquesta raó, i degut a que es tracta d'un protocol MAC extremadament eficient energèticament, aquesta tesi conté una caracterització completa de BLE en el capítol 7. Finalment, el capítol 8 soluciona un dels inconvenients del sistemes WuR, el disseny de WuTx específics, presentant una estratègia per a transformar qualsevol dispositiu IEEE 802.11 en WuTx