Kohlenstoffnanoröhrchen (engl. carbon nanotubes, CNTs) sind Dank ihrer außergewöhnlichen elektrischen Eigenschaften Kandidaten für eine Vielzahl von Anwendungen im Bereich der Mikroelektronik. Ihre ballistischen Transporteigenschaften und die geringe Anfälligkeit auf Elektromigration sind vorteilhaft für die Anwendung von CNTs in Interconnectsystemen. Die Abhängigkeit der elektrischen Transporteigenschaften von mechanischer Verformung bildet weiterhin die Grundlage für die Produktion neuartiger Sensoren auf CNT-Basis. Durch die Besetzung mit Adatomen können diese Eigenschaften dabei weiter verbessert und bei der Herstellung gezielt eingestellt werden. Die Verformung besetzter CNTs ist dabei ein noch relativ unerforschtes Gebiet. In dieser Arbeit wird dieses Verhalten untersucht. Zu Beginn wird gezeigt, dass die Eigenschaften von CNTs durch die Besetzung mit verschiedenen Metallen auf unterschiedliche Weise beeinflusst werden können. Dazu gehören auch Unterschiede zwischen den Spinzuständen, welche bei einigen der untersuchten Metalle auftreten. Durch die axiale Verformung der CNTs wird abschließend gezeigt, dass die Sensoreigenschaften von CNTs auch nach der Besetzung mit Metallen erhalten bleiben.

Flapping-wing micro air vehicle (MAV) is an emerging micro-robotic technology, which has several challenges toward its practical implementation. Inspired by insect flight, researchers have adopted bio-mimicking approach to accomplish its engineering model. There are several methods to synthesize such an electromechanical system. A piezoelectric actuator driven flapping mechanism, being voltage controlled, monolithic, and of solid state type exhibits greater potential than any conventional motor driven flapping wing mechanism at small scale. However, the demand for large tip deflection with constrained mass introduces several challenges in the design of such piezoelectric actuators for this application. The mass constraint restricts the geometry, but applying high electric field we can increase the tip deflection in a piezoelectric actuator. Here we have investigated performance of rectangular piezo-actuator at high electric field. The performance measuring attributes such as, the tip deflection, block force, block moment, block load, output strain energy, output energy density, input electrical energy, and energy efficiency are analytically calculated for the actuator at high electric field. The analytical results suggest that the performance of such an actuator can be improved by tailoring the geometry while keeping the mass and capacitance constant. Thereby, a tapered piezoelectric bimorph cantilever actuator can provide better electromechanical performance for out-of-plane deflection, compared to a rectangular piezoelectric bimorph of equal mass and capacitance. The constant capacitance provides facility to keep the electronic signal bandwidth unchanged. We have analytically presented improvement in block force and its corresponding output strain energy, energy density and energy effi- ciency with tapered geometry. We have quantitatively and comparatively shown the per- formance improvement. Then, we have considered a rigid extension of non-piezoelectric material at the tip of the piezo-actuator to increase the tip deflection. We have an- alytically investigated the effect of thick and thin rigid extension of non-piezoelectric material on the performance of this piezo-actuator. The formulation provides scope for multi-objective optimization for the actuator subjected to mechanical and electrical con- straints, and leads to the findings of some useful pareto optimal solutions. Piezoelectric materials are polarized in a certain direction. Driving a piezoelectric actuator by high electric field in a direction opposite to the polarized direction can destroy the piezo- electric property. Therefore, unipolar high electric field is recommended to drive such actuators. We have discussed the drawbacks of existing switching amplifier based piezo- electric drivers for flapping wing MAV application, and have suggested an active filter based voltage driver to operate a piezoelectric actuator in such cases. The active filter is designed to have a low pass bandwidth, and use Chebyshev polynomial to produce unipolar high voltage of low flapping frequency. Adjustment of flapping frequency by this voltage driver is compatible with radio control communication. To accomplish the flapping-wing mechanism, we have addressed a compatible dis- tributed compliant mechanism, which acts like a transmission between the flapping wing of a micro air vehicle and the laminated piezoelectric actuator, discussed above. The mechanism takes translational deflection at its input from the piezoelectric actuator and provides angular deflection at its output, which causes flapping. The feasibility of the mechanism is investigated by using spring-lever (SL) model. A basic design of the com- pliant mechanism is obtained by topology optimization, and the final mechanism is pro- totyped using VeroWhitePlus RGD835 material with an Objet Connex 3D printer. We made a bench-top experimental setup and demonstrated the flapping motion by actuating the distributed compliant mechanism with a piezoelectric bimorph actuator.

Today in the scientific and technological world, physical and artificial processes are often described by mathematical models which can be used for simulation, optimization or control. As the mathematical models get more detailed and different coupling effects are required to include, usually the dimension of these models become very large. Such large-scale systems lead to large memory requirements and computational complexity. To handle these large models efficiently in simulation, control or optimization model order reduction (MOR) is essential. The fundamental idea of model order reduction is to approximate a large-scale model by a reduced model of lower state space dimension that has the same (to the largest possible extent) input-output behavior as the original system. Recently, the system-theoretic method Balanced Truncation (BT) which was believed to be applicable only to moderately sized problems, has been adapted to really large-scale problems. Moreover, it also has been extended to so-called descriptor systems, i.e., systems whose dynamics obey differential-algebraic equations. In this thesis, a BT algorithm is developed for MOR of index-1 descriptor systems based on several papers from the literature. It is then applied to the setting of a piezo-mechanical system. The algorithm is verified by real-world data describing micro-mechanical piezo-actuators. The whole algorithm works for sparse descriptor form of the system. The piezo-mechanical original system is a second order index-1 descriptor system, where mass, damping, stiffness, input and output matrices are highly sparse. Several techniques are introduced to reduce the system into a first order index-1 descriptor system by preserving the sparsity pattern of the original models. Several numerical experiments are used to illustrate the efficiency of the algorithm.

The door lock - a key function in every modern home, as well as a product which is today undergoing drastic change. The digital revolution has not left the door lock untouched, and there is today a wide variety of digital door locks utilizing technologies ranging from touch displays to fingerprint readers. The premises of the project was to try a different approach to the digital door lock and implement it schoolyard-style using a secret knock sequence, set by the user. The secret sequence would consist of two elements, both a rhythmical and a positional pattern. To unlock the door, the user would therefore need to simultaneously knock the correct rhythm and knock at the correct positions. To record and analyze the knock vibrations, piezo electric sensors connected to an Arduino Uno were used. To unlock the door, a small servo motor, two gears and a timing belt were used to turn the lock turning knob . Despite a short time frame and hardships due to the limitations caused by the coronavirus outbreak, a fully functional prototype which fulfilled both reliability and consistency was achieved. It could with good consistency recognize the test sequence, which was the intro rhythm to ”We Will Rock You” knocked in a square pattern. But even with flawless functionality, the conclusion would have been the same. The security of the system may be exceptional from a technical perspective, but it falls flat when the human factor is taken into account. The ability for a potential burglar to simply watch as one executes the secret knock is too much of a security hazard for the system to ever be considered as a competitor to other alternatives. The usage of the system is therefore better suited for applications where the thrill of using the product is more important than the actual security of it. / Dörrlåset - en grundläggande funktion i varje modernt hem, och samtidigt en produkt som idag genomgår drastisk förändring. Som resultat av den digitala revolutionen finns det idag en uppsjö av olika digitala dörrlås som utnyttjar allt från touchskärmar till fingeravtrycksläsare. Syftet med projektet var att testa en annorlunda tappning på det digitala dörrlåset, och förverkliga något många hade drömt om i barndomen - ett dörrlås aktiverat genom ett eget hemligt knackningsmönster. Det hemliga knackningsmönstret skulle då bestå av både ett rytmiskt och ett positionellt mönster. Därmed skulle den som ville öppna dörren behöva knacka både rätt rytm, och på rätt ställen på dörren. För att spela in och analysera vibrationerna från knackningarna användes piezoelektriska sensorer kopplade till en Arduino Uno. Mekanismen som styrde själva upplåsningen bestod av en liten servomotor, två kugghjul och en kuggrem som kopplade samman det hela. Trots en begränsad tidsram och motgångar orsakade av coronaviruset lyckades en fullt fungerande prototyp med hög pålitlighet färdigställas. Den kunde med hög tillförlitlighet känns igen testsekvensen, som var introrytmen till ”We Will Rock You” knackat i mönstret av en kvadrat. Men även med felfri prestanda hade slutsatsen varit densamma. Säkerheten för systemet må vara exeptionell ur ett rent tekniskt perspektiv, men den faller platt när den mänskliga faktorn tas med i beräkningen. Risken att en potentiell inbrottstjuv helt enkelt tittar på när någon knackar det hemliga mönstret är för stor för att systemet någonsin skulle kunna betraktas som en seriös konkurrent till andra digitala dörrlås. Produkten är därmed bäst lämpad för användningsområden där nöjet av att använda den är av högre prioritet än själva säkerheten.

Low-temperature magnetic force microscopy was used to study the phase diagram of a La1/3Pr1/3Ca1/3MnO3 thin film grown on a (110) NdGaO3 (NGO) substrate by pulsed laser deposition. Traditionally, one can observe the phase change at the nanoscale level as the sample is cooled from room temperature through the transition temperature to liquid nitrogen temperatures, but in this case a fixed voltage ranging from 0 V to 31 V was applied before each cooling cycle. From in and ex situ transport measurements, it is observed that the temperature of the peak of the transition increases with applied field; however, the MFM images show that the magnetic transition begins at a lower temperature with the same increase in field. Thus, this dissertation shows that a new voltage control exists for the phase transition in certain manganites. / text

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: There is a need for a coarse-to-fine positioning system as per a case study presented by the project collaboration partner, the Technical University of Chemnitz. The case study involves the picking and placing of piezo-ceramic micro parts into milled micro cavities. The focus of the project is the creation and development of a systematic approach for the design and the implementation of a coarse-to-fine positioning system for micro material handling. A second focus is to determine the applicability of the system for highly accurate and repeatable micro drilling and micro-milling. A systematic approach entails combining innovation management (assists in overall project structure), systems engineering (assists in specific design steps and tools) and research questions. Micro-milling was achieved, however the system proved unsuitable for highly accurate and repeatable micro drilling. The coarse-to-fine positioning system was successfully designed, built, and tested for accurate micro material handling. / AFRIKAANSE OPSOMMING: Daar bestaan ’n behoefte aan ’n grof-tot-fyn-posisioneringstelsel - soos blyk uit die gevallestudie uiteengesit deur die samewerkende projekvennoot, die Tegniese Universiteit van Chemnitz. Die gevallestudie behels die uitsoek en plasing van piezo-keramiek partikels in gefreesde mikroholtes. Hierdie projek het gefokus op die skepping en ontwikkeling van ’n stelselmatige benadering tot die ontwerp en implementering van ’n grof-tot-fyn-posisioneringstelsel vir mikromateriaalhantering en mikromasjienering. ’n Stelselmatige benadering behels dat innovasiebestuur (hulp met die algehele projekstruktuur), stelselingenieurswese (hulp met spesifieke ontwerpstappe en -hulpmiddels) en navorsingsdoelwitte gekombineer word. Die geïmplementeerde stelsel is eksperimenteel getoets en daar is bevind dat dit aan die spesifikasies en vereistes voldoen.

Dans le domaine de l’aéronautique, l’acception ‘shape morphing’ a été utilisée pour identifier ces avions qui subissent certaine modifications géométrique pour améliorer leur adaptation au différents profils de missions. Différemment de la solution classique, celle ‘shape morphing’ exige : une distribution d’actionnement avec une densité de puissance élevée, une mécanisation des structures, des revêtements souples, et le développement des loi de contrôle. Dans ce scénario, un modèle capable reconnaitre l'insertion de capteur et d'actionneur de nouvelle génération, et capable de réduire au minimum le coût du calcul devient très intéressant. Ce travail essaye d'affronter deux aspects différents du problème. Dans la première partie, la question suivante a été exploitée: pour un problème donné, géométrie, chargement, etc. .. condition aux limites, quel est le modèle le plus précis en terme de résultats, fidélité et avec le plus réduit coût de calcul? Deux approches différentes ont été utilisées pour donner une réponse. Le diagramme de la « Théorie Meilleur Plate (RTPB) » a été dessiné. Avec cet instrument il est possible, pour un problème donné, d'identifier les modèles ayants les meilleurs temps de calcul et une bonne fidélité des résultats. Dans la deuxième partie de la thèse un modèle avancé mono dimensionnel et multi domaine en éléments fini est présenté. Le modèle est capable de capturer l'insertion d'éléments piézo-électriques dans l'aile composite. Il a été développé à partir de la formulation Carrera unifiée et à partir de l'équation de comportement électro-mécanique. Une comparaison avec la bibliographie actuelle a été fait afin de valider les résultats. / In the field of aeronautics, shape morphing has been used to identify those aircraft that un-dergo certain geometrical changes to enhance or adapt to their mission profile. Different formthe classical solution the shape morphing required: distributed high-power density actuation, structural mechanization, flexible skins, and control law development. In these scenario, model able to capture the insertion of new generation sensor and actuator, and able to minimize the computational cost become very interesting. These work try to affront two different aspect of the problem. In the first part the following question has been exploited: for a given problem, geometry, loading, boundary condition etc... which is the most accurate model in term of results fidelity with the lowest computational cost? Two different approaches have been used to give an answer. The Best Plate Theory Diagram (BPTD) has been drawn. Trough the BPTD it is possible, for a given problem, to identify those models with the lowest computational time and a good results fidelity. An advanced mono-dimensional multi-field FEM model is presented in the second part of the thesis. The model is able to capture the insertion of piezo-electric elements in composite wing. It has been developed starting from the Carrera Unified Formulation and from the electro-mechanical constitutive equation. Comparison with the bibliography have be done in order to validate the results. / Nel campo dell’aeronautica il termine shape morphing identifica quei velivoli in grado di apportare determinati cambiamenti geometrici al fine di adattarsi a diversi profili di missione. Diversamente dalle soluzioni convenzionali la progettazione di velivoli shape morphing richiede : un’attuazione distribuita, uno skin flessibile in grado di pemettere le deformazioni e delle leggi di controllo. Divengono quindi di notevole interesse modelli in grado di cogliere l’inserzione di attuatori e sensori di nuova generazione all’interno dell’ala, e di esibire al contempo un basto costo computazionale. Nel lavoro presentato in questa tesi vengono trattati entrabi gli aspetti. Nella prima parte si è andati a dare una risposta alla segunete domanda: per un dato problema, geometria, condizioni di carico, etc..., qual è il modello più accurato, in termini di fedeltà dei risultati, che presenta il minor costo computazionale? Il problema è stato affrontato attraverso due differenti approcci, che hanno portato alla creazione della "Best Plate Theory Curve", attraverso la quale è possibile, per un dato problema, identificare il modello più idoneo in termini di fedeltà dei risultati e di costo computazionale. Nella seconda parte del lavoro viene presentato un modello mono-dimensionale multi-campo avanzato in grado di cogliere l’inserzione di elementi piezo-elettrici in ali in materiale composito. Questo elemento è stato viluppato partendo dalla Carrera Unified Formulation e dalle equazioni costitutive elettromeccaniche. Sono state effettuate poi delle validazioni attraverso confronti con la bibliografia.

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Purpose of this master´s thesis is a construction proposal of German Equatorial Mount capable to load capacity to 20kg inclusive both shaft-actuators. The solution contains design options of actuators of mount, design proposal of partial systems and parts and calcualtions. More is contain drafts of overal assembly, motor pinion and shaft.

Main purpose of the paper is to present high-response hydraulic linear drive, which is controlled with new digital piezo valve and where the new position transducer is integrated as a part of hydraulic cylinder. Hydraulic digital piezo valve with main static and dynamic characteristics as well as its functionality is presented in detail. The main static and dynamic characteristics of dygital piezo valve which influence directly on the linear drive performance are high resolution of the volume flow rate and high resposne of the valve. Beside valve characteristics the new integrated position transducer, the digital controller and control method, presented in the paper, have major impact on linear drive preformance. At the end of the paper the step response and position resolution of the hydraulic linear drive controlled with the new digital valve is compared with the results of reference hydraulic drive controlled with high response proportional valve.