Mechanical vibrations in large structures such as buildings, bridges, dams and critical frequencies in large machinery generally have low frequencies (100Hz-1000Hz). To monitor large areas of such structures we need huge network of low cost, easily manufacturable, self-powered and stand-alone vibration spectrum sensors. The sensors should also consume very little power during their overall operation cycle and have moderately high frequency resoultion. The thesis provides mathematical analysis, design and development of stand-alone, low frequency vibration spectrum analyzer .A mechanically stretched polymer piezoelectric membrane, which has a fixed length and tension, can act as a single frequency detector due to its unique resonant frequency. Stretching multiple ribbons of diffferent lengths and tensions, a vibration spectrum analyzer, which gives the Fourier frequency components present in an arbitrary mechanical input vibration, can be designed. The thesis presents a detailed description of experiments to evaluate a low frequency vibration spectrum analyzer system that accepts an incoming input vibration and directly provides the spectrum as output. Polymer piezoelectric materials being easily manufacturable these sensors can be deployed in wide area sensor networks that monitor large structures. The thesis also shows design of a vibration energy harvesting system based on the concept of harvesting energy at low frequencies. The need for developing such an energy harvesting system arises from the necessity of making the vibration sensor, self-powered. Multiple experimental tests were performed before developing a prototype vibration energy harvesting circuit.

Supplying wireless sensors from ambient energy is nowadays highly demanded for a higher flexibility of use and low system maintenance costs. Vibration sources are thereby especially attractive due to their availability and the relatively high energy density they can provide. The aim of this work is to realize a hybrid energy converter for vibration sources having low amplitude and low frequency. The idea is to combine two diverse harvesters to realize a higher energy density and at the same time to improve the converter reliability. We focus on the design, modeling, and test of the hybrid vibration converter. For an appropriate converter design, the vibration profiles of several ambient vibration sources are characterized. The results show that the typical frequency and acceleration ranges are between 5 Hz to 60 Hz and 0.1 g to 1.5 g respectively. The proposed converter is based on the magnetoelectric (ME) and electromagnetic (EM) principles. These two principles can be easily combined within almost the same volume, because they generate energy form the same varying magnetic field coupled to the mechanical vibration of the source. Thereby, the energy density is improved as the ME converter is incorporated within the relatively large coil housing of the electromagnetic converter. The proposed converter is based on the use of a magnetic spring instead of the typically used mechanical springs, which applies the repulsive force to the seismic mass of the converter. The applied vibration is transmitted to the converter based on the magnetic spring principle instead of the conventional mechanical springs. Due to the nonlinearity of the magnetic spring, the converter is able to operate for a frequency bandwidth instead of resonant frequency which is the case while using a mechanical spring. Hence, this leads to realize a high converter efficiency even under random vibrations characterized by frequency bandwidth. As well, using magnetic spring principle enables to adjust the resonant frequency of the converter relative to the applied vibration source easily by just adjusting the moving magnet size. For the converter design, a parametric study is conducted using finite element analysis. Two main criteria are thereby taken into account, which are the compactness and the efficiency of the converter. Parameters affecting these two criteria are classified in mechanical, electromagnetic and magnetoelectric parameters. Results show that the combination of the EM and ME principles leads to an improvement of the energy output compared to a single EM or ME converter. The novel hybrid converter is realized and tested under harmonic and real vibration profiles. It comprises two main parts: A fixed part, where the coils and the ME transducer are fixed in order to ensure a good reliability of the converter by avoiding wire movements. A moving part, where the moving magnet of the magnetic spring and the magnetic circuit are placed. The presented converter is reliable and compact, which is able to harvest energy with a maximum output power density of 0.11 mW/cm³ within a frequency bandwidth of 12 Hz for a resonance frequency of 24 Hz under an applied harmonic vibration with an amplitude of 1 mm. / Die Versorgung von drahtlosen Sensoren aus der Umgebungsenergie ermöglicht heutzutage eine hohe Einsatzflexibilität und die Senkung des Systemwartungsaufwands. Schwingungsquellen sind aufgrund ihrer Verfügbarkeit und der damit erreichbaren Energiedichte besonders attraktiv. Ziel dieser Arbeit ist es, einen hybriden Energiewandler für Vibrationsquellen mit geringer Amplitude und niedriger Frequenz zu realisieren. Der Ansatz dabei ist, zwei verschiedene Wandler zu kombinieren, um eine höhere Energiedichte zu erreichen und die Zuverlässigkeit zu verbessern. Der Entwurf konzentriert sich auf die Modellierung und den Test des hybriden Vibrationswandlers. Für einen geeigneten Wandlerentwurf werden die Schwingungsprofileigenschaften mehrerer Umgebungsschwingungsquellen untersucht. Die Ergebnisse zeigen, dass die typische Frequenz zwischen 5 Hz und 60 Hz und der Beschleunigungsbereich zwischen 0,1 g und 1,5 g liegen. Der vorgeschlagene Wandler kombiniert das magnetoelektrischen (ME) Prinzip mit dem elektromagnetischen (EM) Prinzip. Diese beiden Prinzipien können innerhalb des fast gleichen Volumens leicht integriert werden, da sie Energie aus der Variation des gleichen Magnetfeldes, das mit der mechanischen Schwingung gekoppelt ist, erzeugen können. Dadurch wird die Energiedichte verbessert, da der ME-Wandler in das relativ große Spulengehäuse des elektromagnetischen Wandlers eingesetzt werden kann. Darüber hinaus basiert der vorgeschlagene Wandler auf der Verwendung von Magnetfedern, um die Repulsivkraft auf die seismische Masse zu realisieren. Aufgrund der Nichtlinearität der Magnetfeder, kann der Wandler in einem breiteren Frequenzbereich betrieben werden, anstatt nur bei der Resonanzfrequenz, wie es bei der Verwendung einer mechanischen Feder der Fall ist. Dies führt dazu, dass der Wandler auch bei zufälligen breitbandigen Schwingungsquellen effizient betrieben werden kann. Darüber hinaus ermöglicht die Verwendung des Magnetfederprinzips eine einfache Einstellung der Resonanzfrequenz des Wandlers in Bezug auf die Schwingungsquelle, durch Einstellen der Größe des beweglichen Magneten. Für den Wandlerentwurf wird eine Parameterstudie mit Hilfe der Finite-Elemente-Analyse durchgeführt. Zwei Hauptkriterien werden dabei berücksichtigt: Die Kompaktheit und die Energieeffizienz des Wandlers. Parameter die diese beiden Kriterien beeinflussen, können in mechanische, elektromagnetische und magnetoelektrische unterteilt werden. Die Ergebnisse haben gezeigt, dass die Kombination der EM- und ME-Prinzipien zu einer Verbesserung der Energieausbeute im Vergleich zu einem einzelnen EM- oder ME-Wandler geführt hat. Der neuartige Hybrid-Wandler wurde realisiert und unter harmonischen und realen Schwingungsprofilen getestet. Der Wandler besteht aus zwei Hauptteilen: Ein festes Teil, an dem die Spulen und der ME-Wandler befestigt sind, um eine hohe Zuverlässigkeit zu gewährleisten indem auf einen beweglichen Draht verzichtet wird, und ein bewegliches Teil, das sich aus einem beweglichen Magneten zusammensetzt. Der vorgestellte Wandler ist zuverlässig, kompakt und in der Lage, Energie mit einer maximalen Ausgangsleistungsdichte von 0,11 mW/cm 3 und einer Bandbreite von 12 Hz bei einer Resonanzfrequenz von 24 Hz unter einer angelegten harmonischen Schwingung mit einer Amplitude von 1 mm zu gewinnen.

Die Weiterentwicklung klassischer, elektronischer Identifikationstechnologien leistet einen wichtigen Beitrag zum technischen Fortschritt in Industrie, Logistik und Gesundheitswesen. Die vorliegende Dissertationsschrift beschreibt die Entwicklung eines Dual-Feed-Antennendesigns für passive UHF-RFID-Transponder auf kritischen Oberflächen. Die zu Grunde liegende Antennenstruktur besteht aus einem Microstrip-Patch unter Verwendung eines verlustarmen Substratmaterials. Dieser erfährt eine Optimierung hinsichtlich seiner Lesereichweite, insbesondere auf kritischen Oberflächen. Ein Zwei-Port-Konzept mit gekoppeltem Feed-Line-Anpassnetzwerk reduziert die Anzahl benötigter, diskreter Komponenten und ermöglicht eine kostengünstige Herstellung mittels klassischer Ätzverfahren. Verschiedene Ansätze zur Modellierung und zur analytischen Berechnung der Antennenparameter werden dargestellt. Des Weiteren erfolgt eine Verifikation der Antennenstruktur anhand eines Konzepts für einen passiven Energy-Harvesting-RFID-Transponder, der zur Temperaturüberwachung in den genannten Branchen eingesetzt werden kann. Dieses Konzept schließt ein effizientes Energiemanagement mittels eines Ultra-Low-Power-Mikrocontrollers sowie Ansätze zur Energiegewinnung und -speicherung mit ein und stellt die Wahl wichtiger Systemparameter und Bauelemente anhand anwendungsspezifischer Abschätzungen dar.

Indiana University-Purdue University Indianapolis (IUPUI) / The harvested energy of wind can be transferred to the generators either through a gearbox or through an intermediate medium such as hydraulic fluids. In this method, high-pressure hydraulic fluids are utilized to collect the energy of single or multiple wind turbines and transfer it to a central generation unit. In this unit, the mechanical energy of the hydraulic fluid is transformed into electric energy. The prime mover of hydraulic energy transfer unit, the wind turbine, experiences the intermittent characteristics of wind. This energy variation imposes fluctuations on generator outputs and drifts their angular velocity from desired frequencies. Nonlinearities exist in hydraulic wind power transfer and are originated from discrete elements such as check valves, proportional and directional valves, and leakage factors of hydraulic pumps and motors. A thorough understanding of hydraulic wind energy transfer system requires mathematical expression of the system. This can also be used to analyze, design, and predict the behavior of large-scale hydraulic-interconnected wind power plants. This thesis introduces the mathematical modeling and controls of the hydraulic wind energy transfer system. The obtained models of hydraulic energy transfer system are experimentally validated with the results from a prototype. This research is classified into three categories. 1) A complete mathematical model of the hydraulic energy transfer system is illustrated in both ordinary differential equations and state-space representation. 2) An experimental prototype of the energy transfer system is built and used to study the behavior of the system in different operating configurations, and 3) Controllers are designed to address the problems associated with the wind speed fluctuation and reference angular velocity tracking. The mathematical models of hydraulic energy transfer system are also validated with the simulation results from a SimHydraulics Toolbox of MATLAB/Simulink®. The models are also compared with the experimental data from the system prototype. The models provided in this thesis do consider the improved assessment of the hydraulic system operation and efficiency analysis for industrial level wind power application.

Wireless sensor networks (WSNs) have become pivotal in precision agriculture, environmental monitoring, and smart healthcare applications. However, the challenges of energy consumption and security, particularly concerning the reliance on large battery-operated nodes, pose significant hurdles for these networks. Energy-harvesting wireless sensor networks (EH-WSNs) emerged as a solution, enabling nodes to replenish energy from the environment remotely. Yet, the transition to EH-WSNs brought forth new obstacles in ensuring reliable and secure data transmission. In our initial study, we tackled the intermittent connectivity issue prevalent in EH-WSNs due to the dynamic behavior of energy harvesting nodes. Rapid shifts between ON and OFF states led to frequent changes in network topology, causing reduced link stability. To counter this, we introduced the hybrid routing method (HRM), amalgamating grid-based and opportunistic-based routing. HRM incorporated a packet fragmentation mechanism and cooperative localization for both static and mobile networks. Simulation results demonstrated HRM's superior performance, enhancing key metrics such as throughput, packet delivery ratio, and energy consumption in comparison to existing energy-aware adaptive opportunistic routing approaches. Our second research focused on countering emerging threats, particularly the malicious energy attack (MEA), which remotely powers specific nodes to manipulate routing paths. We developed intelligent energy attack methods utilizing Q-learning and Policy Gradient techniques. These methods enhanced attacking capabilities across diverse network settings without requiring internal network information. Simulation results showcased the efficacy of our intelligent methods in diverting traffic loads through compromised nodes, highlighting their superiority over traditional approaches. In our third study, we developed a deep learning-based two-stage framework to detect MEAs. Utilizing a stacked residual network (SR-Net) for global classification and a stacked LSTM network (SL-Net) to pinpoint specific compromised nodes, our approach demonstrated high detection accuracy. By deploying trained models as defenses, our method outperformed traditional threshold filtering techniques, emphasizing its accuracy in detecting MEAs and securing EH-WSNs. In summary, our research significantly advances the reliability and security of EH-WSN, particularly focusing on enhancing the network layer. These findings offer promising avenues for securing the future of wireless sensor technologies.

Lågströmskommunikationsprotokoll såsom 6LoWPAN har använts i stor utsträckning för applikationer som kräver mindre energiförbrukning för trådlös kommunikation på korta avstånd, exempelvis IoT-enheter. Eftersom antalet sådana enheter ökar blir det allt viktigare att överväga ambient energy harvesting som en energikälla för att driva sådana enheter. Det framkallar ett behov av att ompröva designen av ett energieffektivt kommunikationsprotokoll som gör det möjligt för sensorer och aktuatorer att använda den utvunna energin för beräkning och kommunikation. Eftersom den utvunna energin från en energikälla är begränsad och det tar tid för en enhet att samla tillräckligt med energi för datahantering och kommunikation, finns det ett behov av att undersöka energibudgeten och bestämma de kritiska parametrarna som påverkar energiförbrukningen för trådlös kommunikation. En analys av energiförbrukningen utfördes genom att anpassa en Python-modell och simuleringar genomfördes för att hjälpa till att förstå påverkan av nyckelparametrar på energiförbrukningen med hänsyn till en lämplig radio frequency energy harvesting (RF-EH) för “zero” energienheter. I examensarbetet föreslås designöverväganden för ett nytt lågströmskommunikationsprotokoll för “zero” energienheter. Resultaten visade att adaptive data rate (ADR) har en stor betydelse för energibesparingar. Med lämpliga överföringsparametrar inställda kan energiförlusterna för omsändningar och kollisioner minskas. Det är också möjligt att införa en schemaläggningsalgoritm för kommunikationsprocessen för förbättrad kollisionsundvikande. De föreslagna designövervägandena kan tillämpas i framtida arbeten för att förbättra kortdistanskommunikationsprotokollet för “zero” energienheter. / Low power communication protocols such as 6LoWPAN have been widely used on applications that require less energy consumption for short-range wireless communication, for example, Internet of Thing (IoT) devices. As the amount of these devices escalates, it becomes increasingly important to consider ambient energy harvesting (EH) as an energy source to power such devices. This induces a need to reconsider the design of an energy-efficient data transfer protocol that enables the sensors and actuators to utilize the harvested energy for computing and communication. As the harvested energy from an energy source is limited and it takes time for a device to accumulate enough energy for data processing and communication, there is a need to investigate the energy budget and determine the critical parameters that affect the energy consumption for wireless communication. An energy consumption analysis was performed by adapting a Python model, and simulations were carried out to help understand the impact of key parameters on energy consumption while considering a suitable range for radio frequency (RF) energy harvesting “zero” energy devices. The thesis project aims to propose the design considerations of a new low-power communication protocol for “zero” energy devices. The results showed that adaptive data rate (ADR) has a major contribution to energy saving. With suitable transmitting parameters set, the energy waste of retransmissions and collisions could be reduced. It is also possible to introduce a scheduling algorithm to the communication process for improved collision avoidance. The proposed design considerations can be applied in future work to improve the shortrange communication protocol for zero-energy devices.

Doctor of Philosophy / Department of Electrical and Computer Engineering / Balasubramaniam Natarajan / In recent years, there has been a rapid expansion in the development and use of low-power, low-cost wireless modules with sensing, computing, and communication functionality. A wireless sensor network (WSN) is a group of these devices networked together wirelessly. Wireless sensor networks have found widespread application in infrastructure, environmental, and human health monitoring, surveillance, and disaster management. While there are many interesting problems within the WSN framework, we address the challenge of energy availability in a WSN tasked with a cooperative objective. We develop approximation algorithms and execute an analysis of concave utility maximization in resource constrained systems. Our analysis motivates a unique algorithm which we apply to resource management in WSNs. We also investigate energy harvesting as a way of improving system lifetime. We then analyze the effect of using these limited and stochastically available communication resources on the convergence of decentralized optimization techniques. The main contributions of this research are: (1) new optimization formulations which explicitly consider the energy states of a WSN executing a cooperative task; (2) several analytical insights regarding the distributed optimization of resource constrained systems; (3) a varied set of algorithmic solutions, some novel to this work and others based on extensions of existing techniques; and (4) an analysis of the effect of using stochastic resources (e.g., energy harvesting) on the performance of decentralized optimization methods. Throughout this work, we apply our developments to distribution estimation and rate maximization. The simulation results obtained help to provide verification of algorithm performance. This research provides valuable intuition concerning the trade-offs between energy-conservation and system performance in WSNs.

This thesis introduces the circuit and system design of interactive Radio-Frequency Identification (RFID) for Internet of Things (IoT) applications. IoT has the vision of connectivity for anything, at anytime and anywhere. One of the most important characteristics of IoT is the automatic and massive interaction of real physical world (things and human) with the virtual Internet world.RFID tags integrated with sensors have been considered as one suitable technology for realizing the interaction. However, while it is important to have RFID tags with sensors as the input interaction, it is also important to have RFID tags with displays as the output interaction.Display interfaces vary based on the information and application scenarios. On one side, remote and centralized display interface is more suitable for scenarios such as monitoring and localization. On the other side, tag level display interface is more suitable for scenarios such as object identification and online to offline propagation. For tag level display, though a substantial number of researches have focused on introducing sensing functionalities to low power Ultra-High Frequency (UHF) RFID tags, few works address UHF RFID tags with display interfaces. Power consumption and integration with display of rigid substrate are two main challenges.With the recent emerging of Electronic Paper Display (EPD) technologies, it becomes possible to overcome the two challenges. EPD resembles ordinary ink on paper by characteristics of substrate flexibility, pattern printability and material bi-stability. Average power consumption of display is significantly reduced due to bi-stability, the ability to hold color for certain periods without power supplies. Among different EPD types, Electrochromic (EC) display shows advantage of low driving voltage compatible to chip supply voltage.Therefore this thesis designs a low power UHF RFID tag integrated in 180 nm CMOS process with inkjet-printed EC polyimide display. For applications where refresh rate is ultra-low (such as electronic label in retailing and warehouse), the wireless display tag is passive and supplied by the energy harvested from UHF RF wave. For applications where refresh rate is not ultra-low (such as object identification label in mass customized manufacturing), the wireless display tag is semi-passive and supplied by soft battery. It works at low average power consumption and with out-of-battery alert. For remote and centralized display, the limitations of uplink (from tags to reader) capacity and massive-tag information feedback in IoT scenarios is the main challenge. Compared to conventional UHF RFID backscattering whose data rate is limited within hundreds of kb/s, Ultra-wideband (UWB) transmission have been verified with the performance of Mb/s data rate with several tens of pJ/pulse energy consumption.Therefore, a circuit prototype of UHF/UWB RFID tag replacing UHF backscattering with UWB transmitter is implemented. It also consists of Analog-to-Digital Converter (ADC) and Electrocardiogram (ECG) electrodes for healthcare applications of real-time remote monitoring of multiple patients ECG signals. The ECG electrodes are fabricated on paper substrate by inkjet printing to improve patient comfort. Key contribution of the thesis includes: 1) the power management scheme and circuit design of passive UHF/UWB RFID display tag. The tag sensitivity (the input RF power) is -10.5 dBm for EC display driving, comparable to the performance of conventional passive UHF RFID tags without display functions, and -18.5 dBm for UWB transmission, comparable to the state-of-the-art performance of passive UHF RFID tag. 2) communication flow and circuit design of UHF/UWB RFID tag with ECG sensing. The optimum system throughout is 400 tags/second with 1.5 KHz ECG sampling rate and 10 Mb/s UWB pulse rate. / <p>QC 20151012</p>

This report deals with the development of a wireless sensor system that measures the environmental energy and predicts if energy harvesting could be possible in different areas. It provides an overview over the hardware used to build this system and gives a detailed description of the software implementation of the system. The hardware part presents the microcontroller and platform that is used, as well as the sensors integrated in the system. The software part explains how the used hardware was put together in a program that controls the different components. It explains the possibility to save captured sensor values on an SD card or send them to a remote receiver with an XBee radio module in real time. Also the inclusion of the mbed software library, which provides a lot of useful applications and functions for the project, is an important part. The final part of the report presents the results, showing how the system works.

The goal of this dissertation consists of improving the efficiency of energy harvesting using pyroelectric and piezoelectric materials in a system by the proper characterization of electrical parameters, widening frequency, and coupling of both effects with the appropriate parameters. A new simple stand-alone method of characterizing the impedance of a pyroelectric cell has been demonstrated. This method utilizes a Pyroelectric single pole low pass filter technique, PSLPF. Utilizing the properties of a PSLPF, where a known input voltage is applied and capacitance Cp and resistance Rp can be calculated at a frequency of 1 mHz to 1 Hz. This method demonstrates that for pyroelectric materials the impedance depends on two major factors: average working temperature, and the heating rate. Design and implementation of a hybrid approach using multiple piezoelectric cantilevers is presented. This is done to achieve mechanical and electrical tuning, along with bandwidth widening. In addition, a hybrid tuning technique with an improved adjusting capacitor method was applied. An toroid inductor of 700 mH is shunted in to the load resistance and shunt capacitance. Results show an extended frequency range up to 12 resonance frequencies (300% improvement) with improved power up to 197%. Finally, a hybrid piezoelectric and pyroelectric system is designed and tested. Using a voltage doubler, circuit for rectifying and collecting pyroelectric and piezoelectric voltages individually is proposed. The investigation showed that the hybrid energy is possible using the voltage doubler circuit from two independent sources for pyroelectrictity and piezoelectricity due to marked differences of optimal performance.