Special Issue on IWPMA (International Workshop on Piezoelectric Materials and Applications in Actuators) 2019

[No abstract available

Analysis and practical considerations of linear and nonlinear piezoelectric energy conversion and harvesting techniques

La décroissance de la consommation électrique des dispositifs électroniques leur a permis une croissance sans précédent. Néanmoins, les éléments de stockage d énergie (piles et batteries), bien qu ayant initialement promus ce développement, sont devenus un frein à la prolifération des microsystèmes électroniques, de part leur durée de vie limitée ainsi que des considérations environnementales (recyclage). Pour palier à ce problème, la possibilité d exploiter l énergie de l environnement immédiat du dispositif a été proposée et a fait l objet de nombreuses recherches au cours des dernières années. En particulier, la récupération d énergie mécanique exploitant l effet piézoélectrique est l une des pistes les plus étudiées actuellement pour la conception de microgénérateurs autonomes capables d alimenter les dispositifs électroniques. Par ailleurs, dans ce domaine, il a été démontré qu un traitement non-linéaire de la tension de sortie de l élément actif permet d améliorer les capacités de récupération de l énergie vibratoire. L une de ces approches, nommée Synchronized Switch Harvesting on Inductor (récupération par commutation synchronisée sur inductance) et consistant en une inversion de la tension de manière synchrone avec le déplacement, s est montrée particulièrement efficace, pouvant augmenter la quantité d énergie récupérée par un facteur supérieur à 10. Cette dernière conduit à un processus cumulatif qui augmente artificiellement la tension de sortie de l élément piézoélectrique ainsi qu à une réduction du déphasage entre tension et vitesse de déplacement ; ces deux effets conduisant à l augmentation importante des capacités de conversion. Néanmoins, l étude des microgénérateurs d énergie s est quasiment toujours faite en considérant une excitation sinusoïdale, ce qui correspond rarement à la réalité. Peu de travaux expérimentaux, et encore moins théoriques, ont été menés en considérant une excitation large bande ; ceci étant d autant plus vrai pour les dispositifs incluant un élément non-linéaire. Ainsi l objectif de cette thèse est d étudier le comportement des récupérateurs d énergie piézoélectriques interfacés de manière non-linéaire. Pour ce faire, différentes approches seront envisagées, en considérant le processus de commutation comme un auto-échantillonnage du signal, ou en appliquant des théories d analyse stochastique pour quantifier les performances du dispositif. Ainsi, plusieurs formes d excitation appliquée au système pourront être analysées, permettant d étudier la réponse du système sous des conditions plus réalistes. Toujours dans l optique d une implémentation réaliste, un autre objectif de cette thèse consistera à évaluer l impact de la récupération d énergie par couplage sismique sur la structure hôte, démontrant la nécessité d envisager le système dans sa globalité afin de disposer de systèmes performants capables de convertir efficacement l énergie vibratoire sous forme électrique pour un usage ultérieur.A nonlinear interface consisting in a switching device has been proved to improve the piezoelectric harvester performance. Although existing works are usually done under single frequency excitation. practical cases are more likely broadband and random. In addition, the coupling effect due to the harvesting process is also an interesting issue to discuss. In terms of energy conversion process in seismic piezoelectric harvesters, mechanical interactions between host structure and harvester is an essential issue as well. The purpose of this work is to analysis seismic type piezoelectric harvesters from a practical perspective and to provide an optimal design of the latter. The broadband modeling based on the concepts of self-sampling and self-aliasing is described under broadband excitations for the nonlinear interface called "Periodic Switching Harvesting on Inductor" (PSHI). For this technique, the switching device is considered to be turned on at a fixed switching frequency. Then stochastic modeling is applied to have mathematical expressions that can describe broadband performance of the harvester with power spectral density (PSD) function of signals. As the switch is turned on at a given frequency, the modeling can be derived using cyclostationary theory. The effectiveness of stochastic modeling is validated with experimental measurements and time-domain iterative calculations, and the harvester performance under a band-limited noise excitation is discussed under bell-curved spectra excitations. An optimal switching frequency slightly less than twice the harvester resonant frequency is proved to have the optimal power output under the optimal resistive load. This switching frequency is however dependent on the electromechanical coupling factor of the harvester. Another part of this work discusses the interaction between the host structure and the harvester. The analysis is conducted with a Two-Degree-of-Freedom (TDOF) model. An energy conversion loop is therefore formed between the host structure and the harvester, within the harvester and the resistive load. The TDOF model is verified with Finite Element model and experimental work. An optimal mass ratio is proved to provide the maximal power output. The modeling is further applied to a practical self-powered Structural Health Monitoring system providing the best design of the harvester. A practical consideration of the broadband excitation is also introduced showing the effect of frequency detuning between the host structure and the harvester. Compared to constant force factor case, the harvester performance with a constant electromechanical coupling factor is surprisingly with very little decreases due to the mismatching of harvester and host structure resonant.VILLEURBANNE-DOC'INSA-Bib. elec. (692669901) / SudocSudocFranceF

Synthesis of anthraquinone based electroactive polymers: A critical review

Conducting polymers or synthetic monomers have revolutionized the world and are at the heart of scientific research having a scope of vast diverse applications in many technological fields. The conducting and redox polymers have been investigated as energy storage systems because of their better sustainability, ease of synthesis, and environmental compatibility. Owing to the conducting properties of quinones, they gain too much importance among the researchers. Keeping in view the importance and sustainability of conducting polymers, for the first time, this study compiles a detailed overview of synthetic approaches followed by investigations on electrochemical properties and future directions. This study critically examines the synthetic process of simple monomers, substituted monomers, and polymers of anthraquinone (AQ) under the classification of low- and high-molecular-weight AQ–based derivatives, their working principles, and their electrochemical applications, which enable us to explore their novel possible application in automotive, solar cell devices, aircraft aileron, and biomedical equipment. Irrefutably, we confirm that high-molecular-weight polymeric AQ compounds are best in comparison with low-molecular-weight AQ monomers because they have pre-eminent properties over monomeric systems. Because of the significant properties of AQ, polymeric systems are high demanding and have emerged as a hot topic among the researchers these days. In the current scenario, this study is of immense importance because it identifies and discusses the right and sustainable combination and paves the way to utilize these novel materials in different technologies

Design and analysis of vibration energy harvesters based on peak response statistics

Energy harvesting using cantilever piezoelectric vibration energy harvesters excited by Gaussian broadband random base excitation is considered. The optimal design and analysis of energy harvesters under random excitation is normally performed using the mean and standard deviation of a response quantity of interest, such as the voltage. An alternative approach based on the statistics of the peak voltage is developed in this paper. Three extreme response characteristics, namely (a) level crossing, (b) response peaks above certain level, and (c) fractional time spend above a certain level, have been employed. Two cases, namely the harvesting circuit with and without an inductor, have been considered. Exact closed-form expressions have been derived for number of level crossings, statistics of response peaks and fractional time spend above a certain level for the output voltage. It is shown that these quantities can be related to the standard deviation of the voltage and its derivative with respect to time. Direct numerical simulation has been used to validate the analytical expressions. Based on the analytical results, closed-form expressions for optimal system parameters have been proposed. Numerical examples are given to illustrate the applicability of the analytical results