Nowadays MEMS (Micro Electro-Mechanical System) technology is widely used in a vast range of applications, from automotive, to personal or industrial electronics and much more. They offer both the possibility of sensing an external force and moving (by displacement or deformation) induced by an electrical force: all of this in an unique micro-scale structure provided with micro-mechanical parts and electrical interconnections. In this thesis is discussed a novel application of this device, conceived and developed by STMicroelectronics, company leader in semiconductor and, particularly, MEMS technologies, where I had the possibility to conduct the activities for the fulfillment of my master’s degree in Electronic Engineering. In this project torsional MEMS devices, actuated through the electro-mechanical properties of the piezo-resistive material PZT, are leveraged, with the deposition of a reflective coating (thus, they are called MEMS mirrors), to allow a controlled reflection of a laser beam to perform image projection inside a pair of smart glasses. However, this technology can be implemented in any other Augmented, Virtual or Mixed Reality application, but also for 3D sense and reconstruction purposes as well. The projection technique is called Laser Beam Scanning and exploits one mirror actuated with a linear behavior and another driven at its natural resonance frequency in order to perform a raster scan that would permit, by mean of electronic control, high performances (resolution, brightness etc.) while guaranteeing a compact design. With the development of mirrors with high quality factor, born from the demand of high performing resonant mirrors, the problem of a low responsive device at the initial aperture arise. From this problem a novel architecture for resonant MEMS mirror actuation has been proposed in order to overcome the lower start-up transient and to offer an optimized actuation able to minimize the mirror electrical excitement, thus the power consumption, to maintain it at constant oscillation. The design flow of this architecture started with the development and test of a Simulink model that, subsequently, has been implemented into an FPGA (Field Programmable Gate Array) to run the tests on a real mirror: the implementation of this solution has been achieved together with a study of the pre-existing analog and digital architecture in order to comprehend how the system works and where to implement the new driving module.
Oggi la tecnologia MEMS (Micro Electro-mechanical System) è ampiamente utilizzata in una vasta gamma di applicazioni, dall'automotive, all'elettronica personale o industriale e molto altro ancora. Offrono sia la possibilità di misurare una forza esterna che di muoversi (per spostamento o deformazione) se sottoposti ad eccitamento elettrico: tutto questo in un'unica micro-struttura dotata di parti micro-meccaniche e interconnessioni elettriche. In questa tesi viene discussa una nuova applicazione di questo dispositivo, concepito e sviluppato da Stmicroelectronics, azienda leader nel settore dei semiconduttori e, in particolare, di tecnologie MEMS, dove ho avuto la possibilità di condurre le attività in conclusione del mio percorso di laurea magistrale in Ingegneria Elettronica. In questo progetto dispositivi MEMS di tipo torsionale che sfruttano le proprietà piezo-elettriche del materiale PZT, sono utilizzati, con la deposizione di un rivestimento riflettente (da qui vengono chiamati MEMS mirrors), per consentire una riflessione controllata di un fascio laser per eseguire la proiezione di immagini all'interno di un paio di smart glasses Tuttavia, questa tecnologia può essere implementata in qualsiasi altra applicazione di realtà aumentata, virtuale o mista, ma anche per rilevamento ricostruzione 3D. La tecnica di proiezione si chiama Laser Beam Scanning e sfrutta uno specchio azionato con un comportamento lineare e un altro pilotato alla sua frequenza di risonanza al fine di eseguire una scansione “raster” che consentirebbe, mediante controllo elettronico, alte prestazioni (risoluzione, luminosità ecc.) garantendo un design compatto. Con lo sviluppo di specchi con elevato quality factor, nato dalla necessità di specchi risonanti ad alte prestazioni, sorge il problema di un dispositivo a bassa reattività all'apertura iniziale. Da questo problema è stata proposta una nuova architettura per l'attuazione del MEMS mirror risonante al fine di superare l’elevato transitorio iniziale e di offrire un controllo ottimizzato in grado di minimizzare l'eccitazione elettrica dello specchio, quindi il consumo di energia, per mantenerlo ad oscillazione costante. Il processo di sviluppo di questa architettura è iniziato con lo la costruzione e il test di un modello Simulink che, successivamente, è stato implementato in una FPGA (Field Programmable Gate Array) per eseguire i test su un vero e proprio specchio: l'implementazione di questa soluzione è stata realizzata insieme ad uno studio dell'architettura analogica e digitale preesistente al fine di comprendere il funzionamento del sistema e dove poter implementare il nuovo modulo di drive.
Optimized actuation of resonant MEMS mirror for laser beam scanning application
De BIASI, LORENZO
2019/2020
Abstract
Nowadays MEMS (Micro Electro-Mechanical System) technology is widely used in a vast range of applications, from automotive, to personal or industrial electronics and much more. They offer both the possibility of sensing an external force and moving (by displacement or deformation) induced by an electrical force: all of this in an unique micro-scale structure provided with micro-mechanical parts and electrical interconnections. In this thesis is discussed a novel application of this device, conceived and developed by STMicroelectronics, company leader in semiconductor and, particularly, MEMS technologies, where I had the possibility to conduct the activities for the fulfillment of my master’s degree in Electronic Engineering. In this project torsional MEMS devices, actuated through the electro-mechanical properties of the piezo-resistive material PZT, are leveraged, with the deposition of a reflective coating (thus, they are called MEMS mirrors), to allow a controlled reflection of a laser beam to perform image projection inside a pair of smart glasses. However, this technology can be implemented in any other Augmented, Virtual or Mixed Reality application, but also for 3D sense and reconstruction purposes as well. The projection technique is called Laser Beam Scanning and exploits one mirror actuated with a linear behavior and another driven at its natural resonance frequency in order to perform a raster scan that would permit, by mean of electronic control, high performances (resolution, brightness etc.) while guaranteeing a compact design. With the development of mirrors with high quality factor, born from the demand of high performing resonant mirrors, the problem of a low responsive device at the initial aperture arise. From this problem a novel architecture for resonant MEMS mirror actuation has been proposed in order to overcome the lower start-up transient and to offer an optimized actuation able to minimize the mirror electrical excitement, thus the power consumption, to maintain it at constant oscillation. The design flow of this architecture started with the development and test of a Simulink model that, subsequently, has been implemented into an FPGA (Field Programmable Gate Array) to run the tests on a real mirror: the implementation of this solution has been achieved together with a study of the pre-existing analog and digital architecture in order to comprehend how the system works and where to implement the new driving module.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/174451