Our times are characterized by the ever-increasing need to have interconnected networks of smart objects that exchange data between them. This concept takes the name Internet of Things (IoT). The purposes of having interconnected networks are mainly related to observe the environment around us which, technically, takes the name of monitoring and it is done through sensors. Often, such observation is then exploited to perform further operations through actuators. The application of the concept is very huge and covers different fields, such as monitoring of medical, structural, and infrastructural parameters or machinery control. The last few years have seen the inclusion of monitoring systems even in the field of recreation activities and sports, given the spread of smart technology goods in consumer markets (smartphones, smartwatches and so on). As a consequence, what has been discussed, the insertion of very high quantities of sensors in the environment is required. These should not be invasive in the physical space and, at the same time, they should not consume large amount of energy both for maintenance costs and environmental reasons. It is desiderabile for them to be completely autonomous in terms of energy consumption. On the one hand, the issue of invasiveness can be solved by the so-called Micro Electro-Mechanical Systems (MEMS), which are devices that exploit the silicon technology to integrate electrical and mechanical components at the small scale. On the other hand, the issue of the energetic consumption, can be solved by environmental energy harvesting techniques. Among many possibilities, one promising technique is the exploitation of the mechanical energy of the environmental vibration and its conversion into electrical energy through piezoelectric materials. The combination of the two concepts brings with it a large number of fascinating challenges, some of them purely scientific that involve different Physics area: mechanics, advanced material sciences, and electromagnetism. Other challenges are related to the purely technological and industrial development aspects. In this context this Doctoral Thesis fits. More in detail, this work presents recent detailed investigations on the magnetic frequency up-conversion (FuC) for piezoelectric energy harvesters and its implications. The main original contributions of this Thesis are the following. Theoretical, computational and experimental investigations of the magnetic force for frequency up-converting piezoelectric energy harvesters. Highlighting in a theoretical, computational and experimental framework the dependency of the dynamical response of magnetically actuated oscillators on the interaction velocity and its scientific implications. It is pointed out that the magnetic FuC is not a frequency-driven phenomenon. Highlighting the practical limits of this technique in the context of low-velocity energy harvesting. Proposal of a magnetic shielding technique to overcome the operational limitation of the classical magnetic FuC technique. Design, prototyping and testing of a piezoelectric vibration energy harvester based on the combination of magnetic plucking and indirect impacts. Study of electromagnetic levitation-based phenomena for motion of a mass or a collateral mechanism (i.e. when the plucking does not occur) for energy scavenging. Consideration of observed inherent material nonlinearities in modelling magnetic plucking phenomenon for piezoelectric vibration energy harvesting. Design and analysis of a MEMS piezoelectric energy harvester compatible with the existing microfabrication process for Piezoelectric Micromachined-Ultrasound-Transducers (PMUT). This part is developed in collaboration with the industry STMicroelectronics.
I nostri tempi sono caratterizzati dalla crescente necessità di avere reti interconnesse di oggetti intelligenti che scambiano dati tra loro. Questo concetto prende il nome di Internet of Things (IoT). Gli scopi di avere reti interconnesse sono principalmente legati all'osservazione dell'ambiente che ci circonda che, tecnicamente, prende il nome di monitoraggio e viene effettuato attraverso sensori. Spesso, tale osservazione viene poi sfruttata per eseguire ulteriori operazioni attraverso gli attuatori. L'applicazione del concetto è molto vasta e copre diversi campi, come il monitoraggio di parametri medici, strutturali e infrastrutturali, o il controllo di macchine. Negli ultimi anni si è assistito all'inserimento di sistemi di monitoraggio anche nel campo delle attività ricreative e sportive, vista la diffusione di beni tecnologici intelligenti nei mercati consumer (smartphone, smartwatch e così via). Di conseguenza, è richiesto l'inserimento di quantità molto elevate di sensori nell'ambiente. Questi non devono essere invasivi e, allo stesso tempo, non devono consumare grandi quantità di energia, sia per i costi di manutenzione che per ragioni ambientali. È auspicabile che siano completamente autonomi in termini di consumo energetico. Da un lato, il problema dell'invasività può essere risolto dai cosiddetti Micro Electro-Mechanical Systems (MEMS), dispositivi che sfruttano la tecnologia del silicio per integrare componenti elettriche e meccaniche su piccola scala. D'altra parte, il problema del consumo energetico può essere risolto con tecniche di raccolta di energia ambientale. Tra le tante possibilità, una tecnica promettente è lo sfruttamento dell'energia meccanica associata a vibrazioni ambientali e la sua conversione in energia elettrica attraverso materiali piezoelettrici. La combinazione di questi due concetti porta con sé un gran numero di sfide affascinanti, alcune delle quali puramente scientifiche che coinvolgono diverse aree della Fisica: meccanica, scienza dei materiali ed elettromagnetismo. Altre sfide sono legate agli aspetti puramente tecnologici e di sviluppo industriale. In questo contesto si inserisce la presente tesi di dottorato. Più in dettaglio, questo lavoro presenta recenti indagini specifiche sulla conversione di frequenza (FuC) con magneti permanenti per gli energy harvester piezoelettrici e le sue implicazioni. I principali contributi originali della tesi sono i seguenti. Indagini teoriche, computazionali e sperimentali sulla forza magnetica per la conversione di frequenza in harvester piezoelettrici. Studio in un quadro teorico, computazionale e sperimentale della dipendenza della risposta dinamica degli oscillatori attuati magneticamente dalla velocità di interazione e le relative implicazioni scientifiche. Si evidenzia che la FuC magnetica non è un fenomeno governato dalla frequenza. Osservazione dei limiti pratici di questa tecnica nel contesto dell'energy harvesting a bassa velocità. Proposta di una tecnica di schermatura magnetica per superare i limiti operativi della tecnica FuC magnetica classica. Progettazione, prototipazione e sperimentazione di un energy harvester piezoelettrico di energia da vibrazione basato sulla combinazione di plucking magnetico e impatti indiretti. Studio di fenomeni basati sulla levitazione elettromagnetica per il movimento di una massa o di un meccanismo collaterale (cioè quando non si verifica il plucking) per la raccolta di energia. Considerazione delle non linearità intrinseche del materiale attivo osservate nella modellazione del fenomeno di plucking magnetico per energy harveter piezoelettrici. Progettazione e analisi di un energy harvester piezoelettrico MEMS compatibile con un processo industriale esistente. Questa parte è sviluppata in collaborazione con l'industria STMicroelectronics.
Intentional and inherent nonlinearities in advanced piezoelectric vibration energy harvesting
ROSSO, MICHELE
2022/2023
Abstract
Our times are characterized by the ever-increasing need to have interconnected networks of smart objects that exchange data between them. This concept takes the name Internet of Things (IoT). The purposes of having interconnected networks are mainly related to observe the environment around us which, technically, takes the name of monitoring and it is done through sensors. Often, such observation is then exploited to perform further operations through actuators. The application of the concept is very huge and covers different fields, such as monitoring of medical, structural, and infrastructural parameters or machinery control. The last few years have seen the inclusion of monitoring systems even in the field of recreation activities and sports, given the spread of smart technology goods in consumer markets (smartphones, smartwatches and so on). As a consequence, what has been discussed, the insertion of very high quantities of sensors in the environment is required. These should not be invasive in the physical space and, at the same time, they should not consume large amount of energy both for maintenance costs and environmental reasons. It is desiderabile for them to be completely autonomous in terms of energy consumption. On the one hand, the issue of invasiveness can be solved by the so-called Micro Electro-Mechanical Systems (MEMS), which are devices that exploit the silicon technology to integrate electrical and mechanical components at the small scale. On the other hand, the issue of the energetic consumption, can be solved by environmental energy harvesting techniques. Among many possibilities, one promising technique is the exploitation of the mechanical energy of the environmental vibration and its conversion into electrical energy through piezoelectric materials. The combination of the two concepts brings with it a large number of fascinating challenges, some of them purely scientific that involve different Physics area: mechanics, advanced material sciences, and electromagnetism. Other challenges are related to the purely technological and industrial development aspects. In this context this Doctoral Thesis fits. More in detail, this work presents recent detailed investigations on the magnetic frequency up-conversion (FuC) for piezoelectric energy harvesters and its implications. The main original contributions of this Thesis are the following. Theoretical, computational and experimental investigations of the magnetic force for frequency up-converting piezoelectric energy harvesters. Highlighting in a theoretical, computational and experimental framework the dependency of the dynamical response of magnetically actuated oscillators on the interaction velocity and its scientific implications. It is pointed out that the magnetic FuC is not a frequency-driven phenomenon. Highlighting the practical limits of this technique in the context of low-velocity energy harvesting. Proposal of a magnetic shielding technique to overcome the operational limitation of the classical magnetic FuC technique. Design, prototyping and testing of a piezoelectric vibration energy harvester based on the combination of magnetic plucking and indirect impacts. Study of electromagnetic levitation-based phenomena for motion of a mass or a collateral mechanism (i.e. when the plucking does not occur) for energy scavenging. Consideration of observed inherent material nonlinearities in modelling magnetic plucking phenomenon for piezoelectric vibration energy harvesting. Design and analysis of a MEMS piezoelectric energy harvester compatible with the existing microfabrication process for Piezoelectric Micromachined-Ultrasound-Transducers (PMUT). This part is developed in collaboration with the industry STMicroelectronics.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/197057