Vibration-based energy harvesting has been investigated by several researchers over the last decade. The ultimate goal in this research field is to power small electronic components (such as wireless sensors) by using the vibration energy available in their environment. Among the basic transduction mechanisms that can be used for vibration-to-electricity conversion, piezoelectric transduction has received the most attention in the literature. Piezoelectric materials are preferred in energy harvesting due to their large power densities and ease of application. Typically, piezoelectric energy harvesters are cantilevered structures with piezoceramic layers that generate alternating voltage output due to base excitation. This work presents distributed-parameter electromechanical models that can accurately predict the coupled dynamics of piezoelectric energy harvesters. First the issues in the existing models are addressed and the lumped-parameter electromechanical formulation is corrected by introducing a dimensionless correction factor derived from the electromechanically uncoupled distributed-parameter solution. Then the electromechanically coupled closed-form analytical solution is obtained based on the thin-beam theory since piezoelectric energy harvesters are typically thin structures. The multi-mode electromechanical frequency response expressions obtained from the analytical solution are reduced to single-mode expressions for modal vibrations. The analytical solutions for the electromechanically coupled voltage response and vibration response are validated experimentally for various cases. The single-mode analytical equations are then used for deriving closed-form relations for parameter identification and optimization. Asymptotic analyses of the electromechanical frequency response functions are given along with expressions for the short-circuit and the open-circuit resonance frequencies. A simple experimental technique is presented to identify the optimum load resistance using only a single resistor and an open-circuit voltage measurement. A case study is given to compare the power generation performances of commonly used monolithic piezoceramics and novel single crystals with a focus on the effects of plane-stress material constants and mechanical damping. The effects of strain nodes and electrode configuration on piezoelectric energy harvesting are discussed theoretically and demonstrated experimentally. An approximate electromechanical solution using the assumed-modes method is presented and it can be used for modeling of asymmetric and moderately thick energy harvester configurations. Finally, a piezo-magneto-elastic energy harvester is introduced as a non-conventional broadband energy harvester. / Ph. D.

Low-power requirements of contemporary sensing technology attract research on alternate power sources that can replace batteries. Energy harvesters function as power sources for sensors and other low-power devices by transducing the ambient energy into usable electrical form. Energy harvesters absorbing the ambient vibrations that have potential to deliver uninterrupted power to sensing nodes installed in remote and vibration rich environments motivate the research in vibrational energy harvesting. Piezoelectric bimorphs have been demonstrating a pre-eminence in converting the mechanical energy in ambient vibrations into electrical energy. Improving the performance of these harvesters is pivotal as the energy in ambient vibrations is innately low. The present work is organized in three major sections: firstly, audit of the energy available in a vibrating source and design for effective transfer of the energy to harvesters, secondly, design of vibration energy harvesters with a focus to enhance their performance, and lastly, identification of key performance metrics influencing conversion efficiencies and scaling analysis for MEMS harvesters. Typical vibration levels in stationary installations such as surfaces of blowers and ducts, and in mobile platforms such as light and heavy transport vehicles, are determined by measuring the acceleration signal. The frequency content in the signal is determined from the Fast Fourier Transform. A method of determining the energy associated with the vibrating source and the associated power using power spectral density of the signal is proposed. Power requirements of typical sensing nodes are listed with an intent to determine the adequacy of energy harvesting. Effective transfer of energy from a given vibration source is addressed through the concept of dynamic vibration absorption, which is a passive technique for suppressing unintended vibrations. Optimal absorption of energy from a vibration source entails the determination of absorber parameters such as resonant frequency and damping. We propose an iterative method to obtain these parameters for a generic case of large number of identical vibration absorbers resembling harvesters by minimizing the total energy absorbed by the system. The proposed method is verified by analysing the response of a set of cantilever absorber beams placed on a vibrating cantilever plate. We find, using our method, the values of the absorber mass, resonant frequency and damping of the absorber at which significant amount of energy supplied to the system flows into the absorber, a scenario which is favourable for energy harvesting. We emphasize through our work that monitoring energies in the system and optimizing their flow is both rational and vital for designing multiple harvesters that absorb energy from a given vibration source optimally. Enhancing the performance of piezoelectric energy harvesters through a multilayer and, in particular, a multistep configuration is presented. Partial coverage of piezoelectric material in steps along the length of a cantilever beam results in a multistep piezoelectric energy harvester. We find that the power generated by a multistep beam is almost twice of that generated by a multilayer harvester made out of the same volume of polyviny-lidine fluoride (PVDF), further corroborated experimentally. Improvements observed in the power generated prove to be a boon for weakly coupled, low pro le, piezoelectric materials. Thus, in spite of the weak piezoelectric coupling observed in PVDF, its energy harvesting capability can be improved significantly by using it in a multistep piezoelectric beam configuration. Besides, the effect of piezoelectric step length and thickness in a piezoelectric unimorph harvester and performance metrics such as piezoelectric coupling factor and efficiency of conversion are presented. Modeling of a hybrid energy harvester composed of piezoelectric and electromagnetic mechanisms of energy conversion motivated by the need to determine the contribution of each domain to the power generated by the harvester is presented, particularly, when multiple domains exist in a single harvester. Two exclusive schemes of energy transduction are represented using equivalent circuits, which allow modeling any additional transduction scheme employed in the hybrid harvester with relative ease. Furthermore, a method of determining optimal loads in the respective domains using the equivalent circuit of the hybrid harvester is presented. Four different hybrid energy harvesters were fabricated and evaluated for their performance in comparison with that estimated from the proposed models. Additionally, scaling laws for hybrid energy harvesters are presented. The power developed by both piezoelectric and electromagnetic domains is observed to decrease with width and length cubed. Power indices and figures of merit in a hybrid harvester are proposed and are used to estimate the efficiencies of the four fabricated hybrid harvesters. The important design parameters for micro scale harvesting are identified by performing scaling analysis on MEMS piezoelectric harvesters. Performance of energy harvesters is directly related to the harvester attributes, viz., size, material, and end-mass. Depending on the contribution from each attribute, the power developed by MEMS harvesters can vary widely. A novel method of delineating the power developed by a harvester using five exclusive factors representing scaling, composition, inertia, material, and power (SCIMP) factors is presented. Although the proposed method can be extended to bi-morph and multilayer harvesters, in the present work, we elucidate it by applying it to a MEMS unimorph. We also present a unique coupling factor that ensures maximum power factor in a harvester. As any tiny increment in the power generated would considerably improve the power densities of MEMS harvesters, we focus on enhancing the power developed by maximizing each of the five exclusive factors irrespective of material and size. Furthermore, we demonstrate the competence of the proposed method by applying it on nine different MEMS harvesters reported in the literature. Considering the close match between the reported and predicted performance, we emphasize that monitoring the proposed factors is sufficient to attain the best performance from a harvester.

The development of self-powered wireless sensor networks for structural and machinery health monitoring has attracted considerable attention in the research field during the last decade. Since the low-duty-cycle wireless sensor networks have significantly reduced the power requirements to the range of tens to hundreds of microwatts, it is possible to harvest environmental energy as the power supply instead of using batteries. Vibration energy harvesting using piezoelectric materials has become the most popular technique, which has a good potential to generate adequate power. However, there is a limitation for the conventional beam-shaped harvester designs in real applications due to their limited bandwidth. In order to overcome this limitation, the essential objective of this thesis is to develop harvesters with multi-resonance structures. The multi-resonance harvester with good broadband performance can achieve close resonance frequencies and relatively large power output in each vibration mode. The main tasks and contributions of this thesis are summarised as follows: • A parametric analysis is presented to determine how the modal structural and electromechanical performances of cantilevered beam harvesters are affected by two modal factors designated as mass ratio and electromechanical coupling coefficient (EMCC). The modal performance of using rectangular, convergent and divergent tapered configurations with and without extra masses are systematically analysed by geometric variation using the finite element analysis (FEA) software ABAQUS. • A modal approach using the two modal factors to evaluate the modal performance of harvesters is introduced and a configurational optimization strategy based on the modal approach is developed to pre-select the configurations of multi-resonance harvesters with better modal structural performance and close resonance frequencies in multiple modes. Using this optimization strategy obviates the need to run the full analysis at the first stage. • A novel two-layer stacked harvester, which consists of a base cantilevered beam that is connected to an upper beam by a rigid mass, is developed. By altering the dimensions and the locations of the masses, the two-layer harvester can generate two close resonance frequencies with relatively large power output. The effects of using rectangular, convergent and divergent tapered beam configurations are systematically analysed. • Multi-layer stacked harvesters with up to five layers are developed. The three-layer harvesters with different mass positions, which can generate three close resonance frequencies, are optimized using the configurational optimization strategy. • A novel doubly-clamped multi-layer harvester, which is able to generate five close resonance frequencies with relatively large power output, is developed and thoroughly analysed. • An experimental study of the multi-layer stacked harvester is presented to validate the simulated results and the configurational optimization strategy. • An experimental study of the two-layer stacked harvester using high performance single crystal piezoelectric material PIMNT is presented. The harvester using PIMNT can generate nearly 10 times larger power output and 3.5 times wider bandwidth than using PZT. Besides, by modifying the location of the piezoelectric layer, anti-resonances between two adjacent modes can be eliminated.

No description available.

The proposed vibration energy harvesting IC harvests energy from a piezoelectric transducer (PZT) to provide power for a wireless sensor node (WSN). With a traditional rectification stage, a two-path three-switch dual-input dual-output architecture is adopted to extract power and regulate the output voltage for the load with one stage. The power stage is controlled with a new maximum power point tracking (MPPT) algorithm, which integrates both fraction open circuit voltage (FOCV) and perturb and observe (PandO). The proposed algorithm was able to extract maximum power from a transducer due to high accuracy on the maxim power point (MPP) and low power dissipation. The proposed circuit is implemented in TSMC 180 nm BCD technology and the post-layout simulation verifies the functionality of the proposed design. The simulation results show that the circuit operates under the maximum power point to extract maximum power from a PZT. / Master of Science / The battery life has always been problematic ever since electronic devices exist. As semiconductor technology advances, more transistors could fit in the same area. Resultantly, portable, and mobile devices become more powerful but usually dissipate more power. Unfortunately, the development of the batteries has not been improved significantly. So, it is necessary to charge portable and mobile devices often or replace batteries frequently. In some applications where a device is hard to reach once installed, charging or replacing the battery is difficult. Under these circumstances, energy harvesting from ambient sources is an effective alternative. There are many types of sources of energy widely available in the environment such as vibration, thermal, solar, RF and etc. Solar energy harvesting is the most popular owing to high power density. However, sunlight is unavailable during night time. Vibration energy, although the power density is lower compared with solar, is a viable solution when solar is not a good source of energy. The proposed work utilizes abundant vibration energy at factories to power wireless sensor nodes (WSNs), which can monitor the temperature, light intensity, pressure, etc.

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.

Energy harvesting is playing an increasingly important role in supplying power to monitoring and automation systems such as structural health monitoring using wireless sensor networks. This importance is most notable when the structures to be monitored are in rural, hazardous, or limited access environments such as busy highway bridges where traffic would be greatly disrupted during maintenance, inspection, or battery replacement. This thesis provides an overview of energy harvesting technologies and details the design, prototyping, testing, and simulation of an energy harvester which converts the vibrations of steel highway bridges into stored electrical energy through the use of a translational electromagnetic generator, to power a wireless sensor network for bridge structural health monitoring. An analysis of bridge vibrations, the use of nonlinear and linear harvester compliance, resonant frequency tuning, and bandwidth widening to maximize the energy harvested is presented. The design approach follows broad and focused background research, functional analysis, broad and focused concept generation and selection, early prototyping, parametric modeling and simulation, rapid prototyping with selective laser sintering, and laboratory testing with replicated bridge vibration. The key outcomes of the work are: a breadth of conceptual designs, extensive literature review, a prototype which harvests an average of 80µW under bridge vibration, a prototype which provides quick assembly, mounting and tuning, and the conclusion that a linear harvester out performs a nonlinear harvester with stiffening magnetic compliance for aperiodic vibrations such as those from highway bridges. / text

La récupération de l'énergie des vibrations est un concept relativement nouveau qui peut être utilisé dans l'alimentation des dispositifs embarqués de puissance à micro-échelle avec l'énergie des vibrations omniprésentes dans l’environnement. Cette thèse contribue à une étude générale des récupérateurs de l'énergie des vibrations (REV) employant des transducteurs électrostatiques. Un REV électrostatique typique se compose d'un transducteur capacitif, de l'électronique de conditionnement et d’un élément de stockage. Ce travail se concentre sur l'examen du circuit de conditionnement auto-synchrone proposé en 2006 par le MIT, qui combine la pompe de charge à base de diodes et le convertisseur DC-DC inductif de type de flyback qui est entraîné par le commutateur. Cette architecture est très prometteuse car elle élimine la commande de grille précise des transistors utilisés dans les architectures synchrones, tandis qu'un commutateur unique se met en marche rarement. Cette thèse propose une analyse théorique du circuit de conditionnement. Nous avons développé un algorithme qui par commutation appropriée de flyback implémente la stratégie de conversion d'énergie optimale en tenant compte des pertes liées à la commutation. En ajoutant une fonction de calibration, le système devient adaptatif pour les fluctuations de l'environnement. Cette étude a été validée par la modélisation comportementale.Une autre contribution consiste en la réalisation de l'algorithme proposé au niveau du circuit CMOS. Les difficultés majeures de conception étaient liées à l'exigence de haute tension et à la priorité de la conception faible puissance. Nous avons conçu un contrôleur du commutateur haute tension de faible puissance en utilisant la technologie AMS035HV. Sa consommation varie entre quelques centaines de nanowatts et quelques microwatts, en fonction de nombreux facteurs - paramètres de vibrations externes, niveaux de tension de la pompe de charge, la fréquence de la commutation de commutateur, la fréquence de la fonction de calibration, etc.Nous avons également réalisé en silicium, fabriqué et testé un commutateur à haute tension avec une nouvelle architecture de l'élévateur de tension de faible puissance. En montant sur des composants discrets de la pompe de charge et du circuit de retour et en utilisant l'interrupteur conçu, nous avons caractérisé le fonctionnement large bande haute-tension du prototype de transducteur MEMS fabriqué à côté de cette thèse à l'ESIEE Paris. Lorsque le capteur est excité par des vibrations stochastiques ayant un niveau d'accélération de 0,8 g rms distribué dans la bande 110-170 Hz, jusqu'à 0,75 µW de la puissance nette a été récupérée. / Vibration energy harvesting is a relatively new concept that can be used in powering micro-scale power embedded devices with the energy of vibrations omnipresent in the surrounding. This thesis contributes to a general study of vibration energy harvesters (VEHs) employing electrostatic transducers. A typical electrostatic VEH consists of a capacitive transducer, conditioning electronics and a storage element. This work is focused on investigations of the reported by MIT in 2006 auto-synchronous conditioning circuit, which combines the diode-based charge pump and the inductive flyback energy return driven by the switch. This architecture is very promising since it eliminates precise gate control of transistors employed in synchronous architectures, while a unique switch turns on rarely. This thesis addresses the theoretical analysis of the conditioning circuit. We developed an algorithm that by proper switching of the flyback allows the optimal energy conversion strategy taking into account the losses associated with the switching. By adding the calibration function, the system became adaptive to the fluctuations in the environment. This study was validated by the behavioral modeling. Another contribution consists in realization of the proposed algorithm on the circuit level. The major design difficulties were related to the high-voltage requirement and the low-power design priority. We designed a high-voltage analog controller of the switch using AMS035HV technology. Its power consumption varies between several hundred nanowatts and a few microwatts, depending on numerous factors - parameters of external vibrations, voltage levels of the charge pump, frequency of the flyback switching, frequency of calibration function, etc. We also implemented on silicon, fabricated and tested a high-voltage switch with a novel low power level-shifting driver. By mounting on discrete components the charge pump and flyback circuit and employing the proposed switch, we characterized the wideband high-voltage operation of the MEMS transducer prototype fabricated alongside this thesis in ESIEE Paris. When excited with stochastic vibrations having an acceleration level of 0.8 g rms distributed in the band 110-170 Hz, up to 0.75 $\mu$W of net electrical power has been harvested.

No description available.

The contact between the tire and the road is the key enabler of vehicle acceleration, deceleration and steering. However, under the circumstances of sudden changes to the road conditions, the driver`s ability to maintain control of the vehicle maybe at risk. In many cases, this requires intervention from the chassis control systems onboard the vehicle. Although these systems perform well in a variety of situations, their performance can be improved if a real-time estimate of the tire-road contact parameters (ranging from kinematic conditions of the tire to its dynamic properties) are available. At the present stage of development, tire-road contact parameters are indirectly estimated using observers based on vehicle dynamics measurements (acceleration, yaw and roll rates, suspension deflections, etc). Although these methods present a relatively accurate solution, they rely heavily on tire and vehicle kinematic formulations and break down in case of abrupt changes in the measured quantities. To address this problem, researchers have been developing certain sensor based advanced tire concepts for direct measurement of the tire-road contact parameters. Thus the new terms "Intelligent Tire" and "Smart Tire", which mean online tire monitoring are thus enjoying increasing popularity among automotive manufacturers and formed the motivation for this thesis to explore the possibility of developing an intelligent tire system. The development of the so called "intelligent tire/ smart tire system" is expected to spur the development of a new generation of vehicle control system with modified control strategies, leveraging information directly coming from the interface between the tire and the road, and in turn significantly reducing the risk of accidents. The specific contributions of this thesis include the following: • Development of an intelligent tire system, with a special attention to development of measurement and sensor feature extraction methodologies of acceleration signals coming from sensors fixed to the tire innerliner • Design of an integrated vehicle state estimator for application to global chassis control • Development of a model-based tire-road friction estimation algorithm • Development of an intelligent tire based adaptive wheel slip controller for anti-lock brake system (ABS) • Development of a piezoelectric vibration energy harvesting system with an adaptive frequency tuning mechanism for intelligent tires / Master of Science