The objective of this dissertation is to analytically model a parallel plate electrostatic actuator operating in a liquid electrolyte and experimentally verify the analysis. The model assumes the system remains in thermodynamic equilibrium during actuation, which enables the ion mass balance equations and Guass’ Law to be combined into the Poisson-Boltzmann equation. The governing equations also include the linear momentum equation including the following forces: the electric force, the osmotic force, the spring force, the viscous damping force, and the van der Waals force. Equations are also derived for the energy stored in the actuator. The analytical results emphasize the stored energy at mechanical equilibrium and the voltage versus electrode separation behavior including the instability. The analytical results predict that the system may not be a good actuator because the displacement has a very limited stable range, although the actuator would be suitable for bistable applications. The experiment consisted of a fixed flat gold electrode and a movable gold electrode consisting of a gold sphere several micrometers in diameter mounted on the end of an Atomic Force Microscope (AFM) cantilever, which serves as the spring. The electrodes were separated by approximately 100nm of 1mM NaCl aqueous solution. The analytical results were not verified by the experiment. Relative to the analysis, the experiments did not show distinct critical points, and the experiments showed less electrode separation for a given applied electric potential. The experiments did show points at which the electrode separation versus electric potential rapidly changed slope, which may be instability points. It is suggested that this phenomenon may be due to coalesced gas bubbles on hydrophobic regions of the electrode surfaces, which are not included in the model. Although clean gold surfaces are hydrophilic, gold surfaces may become hydrophobic due to impurities.

A reflective type Fresnel lens using an array of micromirrors is designed and fabricated using the MUMPs?? surface micromachining process. The focal length of the lens can be rapidly changed by controlling both the rotation and translation of electrostatically actuated micromirrors. The suspension spring, pedestal and electrodes are located under the mirror to maximize the optical efficiency. The micromirror translation and rotation are plotted versus the applied voltage. Relations are provided for the fill-factor and the numerical aperture as functions of the lens diameter, the mirror size, and the tolerances specified by the MUMPs?? design rules. Linnik interferometry is used to measure the translation, rotation, and flatness of a fabricated micromirror. The reflective type Fresnel lens is controlled by independent DC voltages of 16 channels with a 0 to 50V range, and translational and torsional stiffness are calibrated with measured data. The spot diameter of the point source by the fabricated and electrostatically controlled reflective type Fresnel lens is measured to test focusing quality of the lens.

A reflective type Fresnel lens using an array of micromirrors is designed and fabricated using the MUMPs?? surface micromachining process. The focal length of the lens can be rapidly changed by controlling both the rotation and translation of electrostatically actuated micromirrors. The suspension spring, pedestal and electrodes are located under the mirror to maximize the optical efficiency. The micromirror translation and rotation are plotted versus the applied voltage. Relations are provided for the fill-factor and the numerical aperture as functions of the lens diameter, the mirror size, and the tolerances specified by the MUMPs?? design rules. Linnik interferometry is used to measure the translation, rotation, and flatness of a fabricated micromirror. The reflective type Fresnel lens is controlled by independent DC voltages of 16 channels with a 0 to 50V range, and translational and torsional stiffness are calibrated with measured data. The spot diameter of the point source by the fabricated and electrostatically controlled reflective type Fresnel lens is measured to test focusing quality of the lens.

This dissertation presents a free-space, long-range, passive optical communication system that uses electrostatically modulated microelectromechanical systems (MEMS) structures coupled with a glass total internal reflection (TIR)-type corner cube retroreflector (CCR) as a non-emitting data transmitter. A CCR consists of three mirrors orthogonal to each other, so that the incident beam is reflected back to the incident beam, source. The operational concept is to have a MEMS modulator fusion with TIR CCR, such that the modulators are working periodically to disrupt the evanescent waves at the air interface of one of the three back glass faces of a TIR CCR. The MEMS chip has two primary components: (1) an array of movable light scattering silicon structures with nano roughness and (2) a glass lid with a transparent conductive indium tin oxide (ITO) film. The MEMS structures are bonded to a glass lid using flip-chip bonding. Once bonded, the MEMS structures can be modulated either toward or away from the glass lid, thus disrupting evanescent energy delivered from a probing laser beam. The MEMS structure is precisely bonded to the TIR CCR with an accuracy of 10-30 arc-seconds using a Michelson interferometry feedback system. This is a novel step by which an existing passive commercial CCR can be converted into a modulating active CCR. This CCR-MEMS unit acts as the key element of the transmitter. To illustrate the concept of a low-power, unattended, sensor-monitoring system, we developed a sensor board containing temperature, humidity, and magnetic sensors along with a microprocessor and other electronics. The sensor board and CCR board are packed together and act as the transmitter unit. We developed a benchtop system and an improved portable receiver system. The receiver system contains the laser (as source), a collimating lens (to collect retroreflected signal), an optical, narrow band pass filter, and a detector. The detector signal was amplified and filtered and sent either to the oscilloscope, a lock-in-amplifier, or a laptop to display the sensor data. Using the receiver system, a sensor-CCR-based transmitter unit, and receiver with 635 nm as source, we achieved retroreflective communication over a distance of 300 m.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18585号 / 工博第3946号 / 新制||工||1606(附属図書館) / 31485 / 京都大学大学院工学研究科機械理工学専攻 / (主査)教授 西脇 眞二, 教授 田畑 修, 教授 松原 厚 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Στην παρούσα διδακτορική διατριβή αναλύθηκαν και μελετήθηκαν διάφορα συστήματα (ΗμΕ) προκειμένου να παρουσιαστεί η μοντελοποίηση τους. Κατά τη μοντελοποίηση αυτή, μελετήθη-καν τα χαρακτηριστικά τους και αναλύθηκε η συμπεριφορά τους. Στη συνέχεια, αναπτύχθηκαν νόμοι ελέγχου, οι οποίοι εφαρμόστηκαν στα συστήματα των ΗμΕ προκειμένου να επιτευχθεί ο έλεγχος της συμπεριφοράς τους. Αναλυτικότερα τα ζητήματα με τα οποία ασχολήθηκε η διατριβή αυτή παρουσιάζονται παρακάτω. Αρχικά πραγματοποιήθηκε η μοντελοποίηση των κάτωθι συστημάτων ΗμΕ: α) ένα σύστημα ΗμΕ του κυρίαρχου βαθμού ελευθερίας, β) ένα σύστημα ΗμΕ δύο βαθμών ελευθερίας και γ) ένα σύστημα ΗμΕ του κυρίαρ-χου βαθμού ελευθερίας στη μοντελοποίηση του οποίου λαμβάνεται υπόψιν η παρουσία του αέρα. Στη συνέχεια της διδακτορικής αυτής παρουσιάζονται και αναλύονται οι ελεγκτές οι οποίοι αναπτύχθηκαν και χρησιμοποιήθηκαν για τη μελέτη των συστημάτων αυτών και οι οποίοι είναι οι εξής: α) ένας Σθεναρός PID ελεγκτής, β) ένας Σθεναρός Η-infinity ελεγκτής, γ) ένας Σθεναρός Διακοπτικός PID ελεγκτής και δ) ένας H-infinity ελεγκτής προκαθορισμένων κερδών. Από την εφαρμογή των προτεινόμενων νόμων ελέγχου στα συστήματα ΗμΕ προκύπτουν τα αποτελέσματα της διδακτορικής αυτής διατριβής. Τα αποτελέσματα αυτά χωρίζονται σε δύο κατηγορίες. Αρχικά σε αυτά που αφορούν τη συμπεριφορά και τα χαρακτηριστικά των συστημάτων των ΗμΕ και στη συνέχεια σε αυτά τα οποία σχετίζονται με την εφαρμογή των νόμων ελέγχου στα συστήματα των ΗμΕ. Η κύρια συνεισφορά της διδακτορικής διατριβής αναφέρεται τόσο στην πρόταση νέων τεχνικών ελέγχου για τα συστήματα των ΗμΕ καθώς και η εφαρμογή με επιτυχία των τεχνικών αυτών στα συστήματα τα οποία μελετήθηκαν κατά τη διεκπόνηση της διατριβής. / In the present Phd thesis different systems of Electrostatic micro Actuators (EmA) have been presented and analyzed. During the modeling process the systems have been observed in order to provide the special characteristics and the special behavior of each model. In addition special control laws have been presented in order to control the movement of the movable parts of the EmAs. In general the main issues of this PhD thesis are presented in the sequel. Firstly the modeling of the following EmAs is presented: a) an EmA whose one plate is moving parallel to the x-axis b) an EmA whose plate is moving parallel to the x-axis and is also making an angular rotation c) an EmA system with squeezed film damping effects (presence of air between the moving surfaces). In the sequel the control laws that have been designed for the aforementioned systems are presented. The designed controllers are: a) a Robust PID controller b) a Robust Switching PID controller c) a robust Η-infinity controller and d) a robust Gain Scheduled H-infinity controller. In the last part of this thesis, the simulation results are presented concering both the behavior of the systems as well as the results provided by the application of the control laws.