This thesis discusses a power electronics module (PEM) that is used to extract power from a human energy harvesting generator according to the user’s desired input power, and stores all of the extracted energy into an appropriately sized battery while staying within the charging limitations of the battery. The PEM can temporarily store the peak power produced by the generator allowing the reduction in the size of the battery required to the average power production level of the generator. The battery’s safety and longevity is maintained by charging them at the constant current and constant voltage rate. The design of the two-stage PEM, the requirements of the Energy Storage Capacitor (ESC) and battery size are discussed. The two controllers that control the PEM are explained and the different operating modes of the controllers are reviewed. A two-stage prototype digitally controlled average current mode control Boost converter and average current mode controlled Buck converter were designed and experimental waveforms were captured to test and validate the control theories used in the PEM. A Voltage Adaptive Gain compensator was used to optimize the closed loop response of both the Boost and Buck converters over their respective output and input voltage ranges. The DC efficiency of the prototype was measured with the peak efficiency of the Boost converter equal to 93% and the peak efficiency of the Buck converter measured at 93.7%. The total PEM system efficiency was measured at 87.9% at an input power level of 10 watts. The AC efficiency of the PEM was also measured with a peak efficiency of 91% with Vin = 15 V at Rin = 60 Ω. The software considerations for an embedded system, including power consumption and timing of real time events are reviewed. A software flow chart and timing diagram are provided to help visualize the sequence of the code. A design chart for selection of the size and voltage rating of the ESC was created. An experimental comparison of a single stage design without energy storage capability and the current PEM design was performed, with a power limited source, in order to show the effectiveness of the PEM and controllers at maximizing the power extraction from the generator. The PEM design was able to extract 50% more power than the single stage converter without energy storage capability. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2012-03-20 01:25:20.986

<p>The focus of this dissertation is on the dynamics of electromagnetic systems for energy harvesting and filtering applications. The inclusion of magnets into systems generates nonlinearity due to the nature of electromagnetic interactions. In this work, magnetic nonlinearity manifests in tip interactions for cantilever beams, coupling effects for electromagnetic transduction, and bistable potential wells for a two beam system. These electromagnetic interactions are used to add non-contact coupling effects for the creation of bistable oscillators or arrays of coupled beams for energy filtering.</p><p>Nonlinearity at the tip of cantilever beams acts to change the dynamic and static behavior of the system. In this dissertation, these interactions are analyzed both with and without the nonlinear tip interactions. A linear analysis of the system without the tip interaction first provides insight into the shifting frequencies of the first four natural oscillation modes when considering a rigid body tip mass with rotational inertia and a center of mass that is offset from the tip of the beam. Then, the characterization of the nonlinearities in the beam stiffness and magnetic interaction provide insight into the static and dynamic behavior of the beam. The analytical and numerical investigations, using Rayleigh-Ritz methods and an assumed static deflection, are shown to be consistent with experimental tests. These methods provide a framework for theoretically establishing nonlinear static modes and small-amplitude linear modes that are consistent with physical behavior.</p><p>In electromagnetic coupling, the role of nonlinearity can have a detrimental or beneficial effect on energy harvesting. This work includes an investigation of the response of an energy harvester that uses electromagnetic induction to convert ambient vibration into electrical energy. The system's response behavior with linear coupling or a physically motivated form of nonlinear coupling is compared with single and multi-frequency base excitation. This analysis is performed with combined theoretical and numerical studies.</p><p>The ability of magnets to add nonlinearity to a system allows for the expansion of the phenomenological behavior of said system and potential advantages and disadvantages for energy harvesting. This work studies a two beam system made up of carbon fiber cantilever beams and attached magnetic tip masses with a focus on energy harvesting potential. Numerical and experimental investigations reveal an array of phenomena from static bifurcations, chaotic oscillations, and sub-harmonic orbits. These features are used to highlight the harvesting prospects for a similarly coupled system.</p><p>Beyond nonlinearity, the non-contacting coupling effects of magnets allow for the hypothetical creation of energy filtering systems. In this work, the band structure of a two dimensional lattice of oscillating beams with magnetic tip masses is explored. The focus of the wave propagation analysis is primarily on regions in the band structure where propagation does not occur for the infinite construction of the system. These band gaps are created in this system of 2 x 2 repeating unit cells by periodically varying the mass properties and, for certain configurations, the frequency band gaps manifest in different size and band location. Uncertainty in these regions is analyzed using potential variations associated with specific physical parameters in order to elucidate their influence on the band gap regions. Boundary effects and damping are also investigated for a finite-dimensional array, revealing an erosion of band gaps that could limit the expected functionality.</p> / Dissertation

Wireless sensing applications have extended into power transmission line monitoring applications. Minimal power consumption of sensor electronics have enabled kinetic energy harvesting systems to provides a means of self sustainability in the form of parasitic energy harvesting from power transmission lines. With this goal in mind, a miniature piezoelectric bimorph cantilever harvester has been developed using a magnetic tip mass which interacts with the oscillating magnetic flux surrounding power transmission wires. The focus of this thesis is develop an analytical model which can be used to optimize the amount of piezoelectric material to support sensory electronics. Special emphasis has also been placed on magnet orientation and geometry to ensure optimal magnetic flux interaction between input and output mechanisms. A single prototype harvester is designed with an arbitrary piezoelectric material length and experimentally validated at different conductor wire currents. The analytical model shows excellent agreement in frequency prediction for the prototype tested. Two damping techniques are used to experimentally extract modal damping ratios to predict peak mechanical and electrical responses at resonance frequencies. The miniature prototype design is less than 30 mm in length with only 10 mm piezoelectric material to produce a total volume of 154 10^-12 cm^3. The power output is measured at 174.1 W of power when positioned over top a 10 AWG copper conductor a distance of 6 mm with approximately 16 Amps of current passing though the conductor.

The emergence of microwave energy harvesting systems, commonly referred to as rectenna or Wireless Power Transfer (WPT) systems, has enabled numerous applications in many areas since their primary goal is to recycle the ambient microwave energy. In such systems, microstrip antennas are used as the main source for collecting the electromagnetic energy. In this work, a novel collector based on metamaterial particles, in what is known as a Split Ring Resonator (SRR), to harvest electromagnetic energy is presented. Such collectors are much smaller in size and more efficient than existing collectors (antennas). A feasibility study of SRRs to harvest electromagnetic energy is conducted using a full wave simulator (HFSS). To prove the concept, a 5.8 GHz SRR is designed and fabricated and then tested using a power source, an Infiniium oscilloscope and a commercially available patch antenna array. When excited by a plane wave with an H-field normal to the structure, a voltage build up of 611 mV is measured across a surface mount resistive load inserted in the gap of a single loop SRR. In addition, a new efficiency concept is introduced, taking into account the microwave-to-AC conversion efficiency which is missing from earlier work. Finally, a 9X9 SRR array is compared with a 2X2 patch antenna array, both placed in a fixed footprint. The simulation results show that the array of SRRs can harvest electromagnetic energy more efficiently and over a wider bandwidth range.

Vibration energy harvesting devices have been widely used to power many electronic self-sustainable devices. The aim of this study is to introduce an alternative design to an existing electromagnetic energy harvesting devices to improve the power production of the unit. This thesis presents a multiple degree of freedom compared design and it has demonstrated higher power efficiency over a wider range of frequencies. The power outputs for both the previous single degree of freedom and the current designs are compared and the developed models are validated against their experimental values. Finally, the numerical model is used to find an optimal arrangement to produce the maximum power for the unit.

<p>Over the past decade, a significant amount of research activity has been devoted to developing electromechanical systems that can convert ambient mechanical vibrations into usable electric power. Such systems, referred to as vibratory energy harvesters, have a number of useful of applications, ranging in scale from self-powered wireless sensors for structural health monitoring in bridges and buildings to energy harvesting from ocean waves. One of the most challenging aspects of this technology concerns the efficient extraction and transmission of power from transducer to storage. Maximizing the rate of power extraction from vibratory energy harvesters is further complicated by the stochastic nature of the disturbance. The primary purpose of this dissertation is to develop feedback control algorithms which optimize the average power generated from stochastically-excited vibratory energy harvesters. </p><p>This dissertation will illustrate the performance of various controllers using two vibratory energy harvesting systems: an electromagnetic transducer embedded within a flexible structure, and a piezoelectric bimorph cantilever beam. Compared with piezoelectric systems, large-scale electromagnetic systems have received much less attention in the literature despite their ability to generate power at the watt--kilowatt scale. Motivated by this observation, the first part of this dissertation focuses on developing an experimentally validated predictive model of an actively controlled electromagnetic transducer. Following this experimental analysis, linear-quadratic-Gaussian control theory is used to compute unconstrained state feedback controllers for two ideal vibratory energy harvesting systems. This theory is then augmented to account for competing objectives, nonlinearities in the harvester dynamics, and non-quadratic transmission loss models in the electronics.</p><p>In many vibratory energy harvesting applications, employing a bi-directional power electronic drive to actively control the harvester is infeasible due to the high levels of parasitic power required to operate the drive. For the case where a single-directional drive is used, a constraint on the directionality of power-flow is imposed on the system, which necessitates the use of nonlinear feedback. As such, a sub-optimal controller for power-flow-constrained vibratory energy harvesters is presented, which is analytically guaranteed to outperform the optimal static admittance controller. Finally, the last section of this dissertation explores a numerical approach to compute optimal discretized control manifolds for systems with power-flow constraints. Unlike the sub-optimal nonlinear controller, the numerical controller satisfies the necessary conditions for optimality by solving the stochastic Hamilton-Jacobi equation.</p> / Dissertation

Un nombre croissant d’appareils électroniques portatifs et portables entraîne une demande croissante de module d’alimentation électrique durable et localisé de petite taille et de poids, et offrant une puissance de sortie élevée. En tant que choix prometteur pour l’alimentation électrique, les moissonneuses d’énergie cinétiques (REC), qui transforment les vibrations ou les mouvements ambiants en énergie électrique, sont étudiées de manière intensive ces dernières années. Les performances des RECs miniatures disponibles dans la littérature sont généralement limitées par leur taille. Les vibrations ambiantes sont généralement abondantes en basse fréquence, ce qui est également un facteur majeur limitant la puissance de sortie du REC. Afin d’améliorer la puissance de sortie, nous devrions améliorer l’efficacité de la conversion d’énergie, qui est liée au principe de transduction. Ce travail présente l’amélioration de la puissance de sortie des RECs électrostatiques basse fréquence grâce à un mécanisme de conversion de fréquence mécanique couplé par impact, et propose un modèle numérique prédictif du prototype qui prend en compte l’effet d’amortissement de l’air et les impacts dans le prototype. Un prototype est proposé avec une géométrie améliorée du module capacitif réduisant la force d’amortissement de l’air. Des approches alternatives pour ajuster les RECs à des applications variées sont proposées, y compris un REC entièrement flexible conçue pour l’électronique portable, et un REC à basse fréquence 2-D sensible aux vibrations suivant deux directions orthogonales. De plus, un système d’étiquette RFID entièrement autonome en énergie mettant en œuvre le REC à basse fréquence en tant que module d’alimentation électrique et un module de communication RFID semi-passif est présenté / A growing number of portable and wearable electronics results in an increasing demand of sustainable and localized power supply module of small size and weight, and offering high output power. As a promising choice for the power supply, Kinetic energy harvesters (KEHs), transforming the ambient vibrations or motions into electrical energy, are studied intensively in recent yeas. The performance of the miniature KEHs available in literature are generaly confined by their sized. The ambient vibrations are usually abundant in low frequency, which is also a major factor restricting the output power of the KEH. In order to enhance the power output, we should improve the energy conversion efficiency, which is related to the transduction principle. This work presents the improvement of the output power of low frequency electrostatic KEHs through impact-coupled mechanical frequency up conversion mechanism, and proposes a predictive numerical model of the prototype which considers the squeeze film air damping effect and the impacts in the prototype. A prototype is proposed with improved geometry of capacitive module reducing the air damping force. Alternative approaches to adjust the KEHs to varied applications are proposed, including a fully flexible KEH designed for wearable electronics, and a 2-D low frequency KEH that is sensible to vibrations along two orthogonal directions. In addition, a fully energy-autonomous RFID tag system implementing the low frequency KEH as the power supply module and a semi-passive RFID communication module is presented

The aim for this thesis was to investigate if harvesting of ambient radio waves could be a viable source of energy and where and when it can be used. A survey of the signal strengths at different locations in Uppsala, Sweden was performed which showed that the cellular frequency bands were the ones that carried the most energy. One circuit was manufactured and two more were simulated, together with the circuitry required to measure and display how much energy that was being harvested. The design was tested at the same locations as the survey of the signal strength was conducted at. The maximum harvested energy was 35µW which was at a location inside in a window facing a cellular transmittor with an approximate distance of 100m. At 200m away from a cellular transmitter, the output was 1µW. In a typical city environment, the output from the harvester was 0µW. The harvesting technique was also compared to energy from solar- and thermal energy. The comparison showed that it is almost always more beneficial to use an alternative source of energy, such as solar cells, even indoors.

This study investigates energy harvesting characteristics from a spinning device that consists of a proof mass that is supported by two orthogonal elastic structures with the piezoelectric material. Deformation in the piezoelectric structures due to vibration of the proof mass generates voltages to power electrical loads. The governing equations for this electromechanically coupled device are derived using Newtonian mechanics and Kirchhoff's voltage law. The case where the device rotates at a constant speed and is subjected to sinusoidal base excitation is examined in detail. The energy harvesting behavior is investigated for devices with identical piezoelectric support structures (called tuned devices). Closed-form expressions are derived for the steady state response and power harvested. For nonzero rotation speeds, these devices have multifrequency dynamic response and power harvested due to the combined vibration and rotation of the host system. The average power harvested for one oscillation cycle is calculated for a wide range of operating conditions to quantify the devices' performance. Resonances do not occur for cases when the base excitation frequency is fixed and the rotation speed varies. For cases of fixed rotation speed and varying base excitation frequency, however, resonances do occur. The number and location of these resonances depend on the electrical circuit resistances and rotation speed. Resonances do not occur at speeds or frequencies predicted by resonance diagrams, which are commonly used in the study of rotating system vibration. These devices have broadband speed energy harvesting ability. They perform equally well at high and low speeds; high speeds are not necessary for their optimal performance. The impact of the chosen damping model on energy harvesting characteristics for tuned devices is investigated. Two common damping models are considered: viscous damping and structural (hysteretic) damping. Closed-form expressions for steady state dynamic response and power harvested are derived for models with viscous and structural damping. The average power harvested using the model with structural damping behaves similarly at high speeds and low speeds, and at high resistances and low resistances. For the viscous damping model, however, the average power harvested is meaningfully different at high speeds compared to low speeds, and at high resistances compared to low resistances. The characteristics of devices with nonidentical piezoelectric support structures (called mistuned devices) are investigated numerically. Similar to spinning tuned devices, mistuned devices have multifrequency dynamic response and power harvested. In contrast to tuned devices, high amplitude average power harvested occurs near speeds and base excitation frequencies predicted by resonance diagram.

This dissertation presents a case study which attempts to implement a passive Ultra High Frequency Radio Frequency Identification (UHF RFID) system on aircraft landing gear (LG) to permit component configuration management. It is shown that a monostatic RFID system with two reader antennas, one on the LG main fitting and one in the wing bay allows up to 64 kbits of data to be associated with each LG component. A 7 dB system margin allows data on each LG component to be updated wirelessly and will also enable a passive UHF RFID-based LG health and usage monitoring system when tags with required sensors become available. Results from an electromagnetic simulation show that when a metal is illuminated by a nearby antenna the E-field distribution close to its surface is stronger than in free space. To explore if the stronger E-field can be used to enhance the performance of a conventional passive tag, a 5 cm × 6 mm × 3.02 m aluminium bar has been selected as the tagging object and connected to the reader via an RF feed. It is shown that a conventional metal tag which has a maximum free space range of 1.3 m when mounted on a metal plate can be detected up to 30 m along the aluminium bar from the RF feed. When orientated with the long axis normal to the metal surface a conventional passive tag with a dipole antenna can efficiently harvest the E- field and can be read at least 50 m away from the antenna feed. The proposed use of metal objects as a nearfield antenna is well suited to some applications, but in others a significant wireless path is still required. In such a case, a semi-passive tag can be used. It is demonstrated that a semi-passive tag only requires 14.4 ̧&#x9d;&#x153;&#x2021;̧&#x9d;&#x2018;&#x160; to be read over 42 m in a bistatic RFID system. Such a power consumption can be easily achieved by most energy harvesting techniques. It is demonstrated that a solar-powered semi-passive tag can be read at a range of 22 m, but its performance is still limited by multipath effects. A distributed antenna system (DAS) can be used to overcome these effects by using frequency and phase hopping techniques. It is demonstrated that 50 solar-powered semi-passive tags can be read with no missed detections over a 10 m × 20 m office area with 4 dB system margin.