Das Hauptmerkmal eines fehlertoleranten Regelungssystems ist die Aufrechterhaltung der Gesamtsystemstabilität und einer akzeptablen Leistung angesichts von Fehlern und Ausfällen innerhalb des Systems. In dieser Arbeit wird ein Verfahren zur Fehlererkennung und Ansätze der fehlertoleranten Regelung (FTR) mit einer Anwendung gegen Aktorfehler von Regelungssystemen, die aus sowohl einem einzelnen Aktor als auch mehreren Aktoren (z.B. Softrobotik) bestehen, vorgestellt. Diese Methode beruht hauptsächlich auf einem Index, genannt Fitnessindex (FI. Der FI wird durch den Vergleich der aktuellen Parameter des Aktors und die im Normalzustand mittels eines Modells geschätzt. Die Ergebnisse des Fitnessindex werden mit Hilfe des Performanceindex verwendet zur Bewertung des Schweregrades eines Aktorfehlers während des Betriebes in einem geschlossenen Regelkreis und sind die entscheidende Grundlage zur automatischen Fehlerdetektion, Fehlerdiagnose und der anschließenden FTR. Diese Methode wird in einem Simulationsmodell getestet, das dem Versuchsaufbau eines Formgedächtnislegierungs-Aktors entspricht. Die Simulationsergebnisse zeigen die Berechnungsergebnisse über den FI und anschließend die Verwendung der Ergebnisse des FIs zur Durchführung der FTR, um die Leistung zu gewährleisten und die Zuverlässigkeit der Regelungssysteme zu verbessern, wenn ein Fehler im Aktor auftritt. / The main feature of a fault tolerant control system is to maintain overall system stability and acceptable performance in the face of errors and failures within the system. In this thesis, a method for fault detection and approaches of the fault tolerant control (FTC) with an application against actuator errors of control systems, which consist of a single actuator as well as several actuators (soft robotics), is presented. This method is mainly based on an index called the fitness index (FI). The FI is estimated by comparing the current parameters of the actuator and in the normal state, based on a model. The results of the fitness index are used with the help of the performance index to evaluate the severity of an actuator fault during an operation in a control loop and are the decisive basis for automatic fault detection, fault diagnosis and subsequent the FTC. This method is tested in a simulation model that corresponds to the experimental setup of a shape memory alloy actuator. The simulation results show the calculation results about the FI and in addition the use the results of the FI to perform the FTC in order to ensure the performance and improve the reliability of the control systems when a fault occurs in the actuator.

No description available.

The development of micro and nano-electromechanical systems (MEMS and NEMS) with entirely new or improved functionalities is typically based on novel or improved designs, materials and fabrication methods. However, today’s micro- and nano-fabrication is restrained by manufacturing paradigms that have been established by the integrated circuit (IC) industry over the past few decades. The exclusive use of IC manufacturing technologies leads to limited material choices, limited design flexibility and consequently to sub-optimal MEMS and NEMS devices. The work presented in this thesis breaks new ground with a multitude of novel approaches for the integration of non-standard materials that enable the fabrication of 3D micro and nanoelectromechanical systems. The objective of this thesis is to highlight methods that make use of non-standard materials with superior characteristics or methods that use standard materials and fabrication techniques in a novel context. The overall goal is to propose suitable and cost-efficient fabrication and integration methods, which can easily be made available to the industry. The first part of the thesis deals with the integration of bulk wire materials. A novel approach for the integration of at least partly ferromagnetic bulk wire materials has been implemented for the fabrication of high aspect ratio through silicon vias. Standard wire bonding technology, a very mature back-end technology, has been adapted for yet another through silicon via fabrication method and applications including liquid and vacuum packaging as well as microactuators based on shape memory alloy wires. As this thesis reveals, wire bonding, as a versatile and highly efficient technology, can be utilized for applications far beyond traditional interconnections in electronics packaging. The second part presents two approaches for the 3D heterogeneous integration based on layer transfer. Highly efficient monocrystalline silicon/ germanium is integrated on wafer-level for the fabrication of uncooled thermal image sensors and monolayer-graphene is integrated on chip-level for the use in diaphragm-based pressure sensors. The last part introduces a novel additive fabrication method for layer-bylayer printing of 3D silicon micro- and nano-structures. This method combines existing technologies, including focused ion beam implantation and chemical vapor deposition of silicon, in order to establish a high-resolution fabrication process that is related to popular 3D printing techniques. / <p>QC 20121207</p>

This thesis presents methods for the wafer-level integration of shape memory alloy (SMA) and electrostatic actuators to functionalize MEMS devices. The integration methods are based on heterogeneous integration, which is the integration of different materials and technologies. Background information about the actuators and the integration method is provided. SMA microactuators offer the highest work density of all MEMS actuators, however, they are not yet a standard MEMS material, partially due to the lack of proper wafer-level integration methods. This thesis presents methods for the wafer-level heterogeneous integration of bulk SMA sheets and wires with silicon microstructures. First concepts and experiments are presented for integrating SMA actuators with knife gate microvalves, which are introduced in this thesis. These microvalves feature a gate moving out-of-plane to regulate a gas flow and first measurements indicate outstanding pneumatic performance in relation to the consumed silicon footprint area. This part of the work also includes a novel technique for the footprint and thickness independent selective release of Au-Si eutectically bonded microstructures based on localized electrochemical etching. Electrostatic actuators are presented to functionalize MEMS crossbar switches, which are intended for the automated reconfiguration of copper-wire telecommunication networks and must allow to interconnect a number of input lines to a number of output lines in any combination desired. Following the concepts of heterogeneous integration, the device is divided into two parts which are fabricated separately and then assembled. One part contains an array of double-pole single-throw S-shaped actuator MEMS switches. The other part contains a signal line routing network which is interconnected by the switches after assembly of the two parts. The assembly is based on patterned adhesive wafer bonding and results in wafer-level encapsulation of the switch array. During operation, the switches in these arrays must be individually addressable. Instead of controlling each element with individual control lines, this thesis investigates a row/column addressing scheme to individually pull in or pull out single electrostatic actuators in the array with maximum operational reliability, determined by the statistical parameters of the pull-in and pull-out characteristics of the actuators. / QC20100729

Dehnungssensoren werden zur Überwachung von sicherheitsrelevanten Bauteilen, besonders in Bauteilen aus faserverstärkten Polymermatrixverbundwerkstoffen eingesetzt. Durch deren Integration in das Bauteilinnere werden sie vor schädigenden mechanischen sowie korrosiven Einwirkungen geschützt. Dies gewährleistet eine zuverlässige sowie dauerhafte Funktion. Verschiedene Ansätze zur Weiterentwicklung integrierbarer Dehnungssensoren werden international untersucht. Die Verringerung des Sensordurchmessers auf Abmaße im Bereich des Durchmessers von Verstärkungsfasern ist dabei ein bedeutendes Entwicklungsziel. Insbesondere bei der Integration in Bauteile aus faserverstärkten Kunststoffen sorgen zum Durchmesser von Fasern vergleichbare Sensordurchmesser für eine optimale Sensoranbindung. Die Bildung von Harznestern sowie schwächender Unstetigkeiten kann mittels dünner Sensoren verhindert werden. Dies gewährleistet eine artefaktefreie Dehnungsmessung. Drei verschiedene Ansätze für neuartige Dehnungssensoren mit kleinem Querschnitt wurden in dieser Arbeit untersucht. / Strain sensors are used for structural health monitoring issues, certainly in parts with high safety requirements made of fibre-reinforced plastic composites. The integration of these sensors inside the parts protects them against any mechanical and corrosive impact. The sensor functionality can be enhanced by integration. There is a lot of international research effort to further develop integratable strain sensors. Different approaches are currently pursued. This thesis presents the results of investigations on three different approaches for novel strain sensors. The main goal of these investigations was to minimise the sensor diameter down to the diameter of reinforcing fibres. The small diameter allows for an optimum and artefact free integration of the sensors. The formation of resin nests and notches to the material structure can be prevented by integrating sensor with a smaller diameter. The strain measurement and monitoring is enhanced and more reliable then.

Les alliages à base de Ni-Mn-In ont attiré une attention considérable en raison de leurs propriétés multifonctionnelles depuis leur découverte en 2004, telles que l’effet de mémoire de forme métamagnétique (Metamagnetic shape memory effect MMSME), l'effet magnétocalorique (MCE) et l'effet de magnétorésistance (MR). Cependant, certaines connaissances fondamentales sur ces alliages manquent toujours jusqu'à présent, telles que la structure cristalline de la martensite, les caractéristiques cristallographiques de microstructure et de transition magnétostructurale. Dans cette thèse, les caractéristiques cristallographiques, les comportements mécaniques et les propriétés magnétiques des alliages Ni-Mn-In base ont été étudiés théoriquement et expérimentalement. Tout d'abord, les structures cristallines des alliages Ni-Mn-In ont été déterminées avec précision par la méthode de Rietveld dans le cadre de la théorie du superespace. Ensuite, la microstructure de la martensite, notamment l'organisation et l'interface des variantes, ainsi que les caractéristiques cristallographiques de la transformation martensitique, telles que les relations d'orientation (OR), le chemin de déformation de la transformation et la compatibilité géométrique entre l'austénite et la martensite, ont été systématiquement étudiés. Enfin, avec cette connaissance fondamentale sur les alliages Ni-Mn-In, les comportements et les mécanismes de sélection /réarrangement des variantes de martensite sous deux types de stratégies de chargement mécanique, à savoir le chargement à l'état martensitique et le chargement durant la transition structurelle, et les effets du recuit sur l'effet MCE et les pertes d'hystérésis associées ont été explorées. Les principaux résultats sont les suivants. La martensite modulé a une structure cristalline incommensurable avec la structure cristalline 6M et le groupe de superespace I2/m(α0γ)00 qui peut être approximée par un modèle de superstructure de multiplicité 3 dans l'espace à tridimensionnel. La microstructure de martensite est en forme de plaques et auto-organisée en colonies. Chaque colonie a quatre variantes d'orientations distinctes. Le maximum de 6 colonies distinctes et 24 variantes peut être généré à l'intérieur d'un grain austénitique. Bien que jusqu'à 14 types de relations de maclage sont proposées dans le cadre des théories cristallographiques de transformation martensitique, seuls trois types de relations de maclage sont généralement observés, à savoir des macles de type I, type II et composées. Les interfaces des variantes sont définies à l'échelle mésoscopique par leur plan de maclage K1 correspondant. Cependant, à l'échelle atomique, la macle de type I a une interface cohérente, alors que celles de type-II et les macles composées ont des interfaces étagées. Les deux relations d'orientations K-S et Pitsch sont appropriés pour décrire la correspondance de réseau entre austénite et martensite dans les alliages Ni-Mn-In. Cependant, le chemin de déformation lié à la relation de Pitsch est mis en évidence pour être efficace pour la déformation de la structure. Avec le chemin de transformation déterminé, le mécanisme sous-jacent de l'organisation des variantes est révélé. À travers la transformation martensitique, en dépit de l'existence d'une relativement large couche contrainte (de l'ordre de 20 nm), le plan d'habitat est bordé par une variante de martensite simple avec l'austénite plutôt que la structure généralement observée "en sandwich", ce qui suggère une relativement bonne compatibilité géométrique entre les phases correspondantes. Pour le chargement en compression à l'état martensitique, l'arrangement des variantes est réalisé par des processus de démaclage. Il est démontré que l'état de variante unique dans certaines colonies pourrait être obtenu lorsque l'orientation de chargement est située dans la zone de Facteur de Schmid (SF) positif commune pour les trois systèmes de démaclage. [...] / Ni-Mn-In based alloys have attracted considerable attention due to their multifunctional properties since its discovery in 2004, such as metamagnetic shape memory effect (MMSME), magnetocaloric effect (MCE) and magnetoresistance (MR) effect. However, some fundenmental knowledge on these alloys is still missing until now, such as crystal structure of martensite, crystallographic features of microstructure and magnetostructural transition. In this dissertation, the crystallographic features, mechanical behaviors and magnetic properties of Ni-Mn-In based alloys were studied theoretically and experimentally. First, the crystal structures of Ni-Mn-In alloys were accurately determined by Rietveld method in the frame of superspace theory (Chapter 3). Then, the microstructure of martensite (Chapter 4), such as variant organization and interface structure, and the crystallographic features of martensitic transformation, such as orientation relationship (OR), transformation strain path and geometrical compatibility between austenite and martensite, were systematically studied (Chapter 5). Finally, with this fundamental knowledge on Ni-Mn-In alloys, the behaviors and mechanisms of martensite variant rearrangement/ selection under two kinds of mechanical loading strategies, i.e. loading at martensite state and loading across the structural transition, and the effects of annealing on MCE and its related hysteresis loss were explored (Chapter 6). The main results are as follows. The modulated martensite has an incommensurate 6M crystal structure with superspace group I2/m(α0γ)00 that can be approximated by a three-fold superstructure model in the three-dimensional space. The microstructure of martensite is in plate shape and self-organized in colonies. Each colony has four distinct orientation variants. The maximum of 6 distinct colonies and 24 variants can be generated within one austenite grain. Although as many as 14 kinds of twin relations are suggested in the frame of crystallographic theories of martensitic transformation, only three types of twin relations are generally detected, i.e. type-I, type-II and compound twin. Variant interfaces are defined by their corresponding twinning plane K1 at mesoscopic scale. However, at atomic scale, the type-I twin has a coherent interface, whereas type-II and compound twins have “stepped” interfaces. Both the K-S and Pitsch ORs are appropriate to describe the lattice correspondence between austenite and martensite in Ni-Mn-In alloys. However, the strain path related to the Pitsch relation is evidenced to be the effective for the structural distortion. With the determined transformation path, the underlying mechanism of variant organization is revealed. Across the martensitic transformation, despite the existence of a relative wide stressed layer (around 20 nm), the habit plane is bordered by single martensite variant with austenite rather than the generally observed “sandwich-like” structure, implying a relative good geometrical compatibility between the corresponding phases. For compressive loading at martensite, variant arrangement is realized by the detwinning process. It is evidenced that a single variant state in some colonies can be obtained when the loading orientation is located in the common positive Schmid factor (SF) zone of the three detwinning systems. For loading across the structural transition, the prestrain is obtained by variant selection in which the number of colonies is significantly reduced and the variant organization within colony is greatly changed. The SF for transformation strain path is introduced to evaluate the possible selection of variants. Heat treatment can significantly enhance the magnetic entropy change ΔSM but simultaneously increase the magnetic hysteresis loss. For ΔSM, the chemical ordered degree should play a prominent role [...]

Shape memory alloys (SMAs) exhibit unique combination of structural and functional properties and hence have a variety of current and potential applications. The mechanical behaviour of SMAs, in particular the influence of processing on the microstructure, which in turn influences the performance of the alloy, mechanical properties at the nano-scale, and under cyclic loading conditions, are of great current interest. In this thesis, specific issues within each of these broad areas are examined with a view to suggest further optimize/characterize SMAs. They are the following: (a) For thermo-mechanical secondary processing of SMAs, can we identify the optimum combination of temperature- strain rate window that yields a desirable microstructure? (b) How can indentation be used to obtain information about functional properties of shape memory alloys so as to complement traditional methods? (c) How can the information obtained from indentation be utilized for the identification of the alloy composition that yields a high temperature SMA through the combinatorial diffusion couple approach? Towards achieving the first objective, we study the hot deformation behavior of a cast NiTi alloy with a view of controlling the final microstructure. The “processing maps” approach is used to identify the optimum combination of temperature and strain rate for the thermomechanical processing of a SMA system commonly used in actuators applications (NiTiCu). Uniaxial compressions experiments are conducted in the temperature range of 800- 1050 °C and at strain rate range of 10-3 and 102 s-1. 2-D power dissipation efficiency and instability maps are generated and various deformation mechanisms, which operate in different temperature–strain rate regimes, are identified with the aid of these maps. Complementary microstructural analysis of specimens (post deformation) is performed with the help of electron backscattered diffraction (EBSD) analysis to arrive at a processing route which produces stress free grains. A safe window suitable for industrial processing of this alloy which leads to grain refinement and strain-free grains (as calculated by various methods of misorientation analysis representation) is suggested. Regions of the instability (characterized by the same analysis) result in strained microstructure, which in turn can affect the performance of the SMA in a detrimental manner. Next, to extract useful information from indentation responses, microindentation experiments at a range of temperatures (as the shape memory transformation is in progress) are conducted underneath the Vickers indenter. SME was observed to cause a change in the calculated recovery ratios at temperatures above As. Spherical indentation of austenite and martensite show different characteristics in elastic and elasto- plastic regimes but are similar in the plastic regime. NanoECR experiments are also conducted under a spheroconical indenter at room temperature, where the resistance measured is observed to increase during the unloading of room temperature austenite SMA. This is a signature of the reverse transformation back to austenite during the withdrawal of the indenter. Lastly, recovery ratios are monitored in the case of a NiTiPd diffusion couple before and after heat treatment at different temperature intervals using non- contact optical profilometry. The recovery ratio approach is successfully used to determine the useful temperature and %Pd range for a potential NiTiPd high temperature SMA. The method makes high throughput identification of high temperature shape memory alloys possible due to promising alloy compositions being identified at an early stage.

Dehnungssensoren werden zur Überwachung von sicherheitsrelevanten Bauteilen, besonders in Bauteilen aus faserverstärkten Polymermatrixverbundwerkstoffen eingesetzt. Durch deren Integration in das Bauteilinnere werden sie vor schädigenden mechanischen sowie korrosiven Einwirkungen geschützt. Dies gewährleistet eine zuverlässige sowie dauerhafte Funktion. Verschiedene Ansätze zur Weiterentwicklung integrierbarer Dehnungssensoren werden international untersucht. Die Verringerung des Sensordurchmessers auf Abmaße im Bereich des Durchmessers von Verstärkungsfasern ist dabei ein bedeutendes Entwicklungsziel. Insbesondere bei der Integration in Bauteile aus faserverstärkten Kunststoffen sorgen zum Durchmesser von Fasern vergleichbare Sensordurchmesser für eine optimale Sensoranbindung. Die Bildung von Harznestern sowie schwächender Unstetigkeiten kann mittels dünner Sensoren verhindert werden. Dies gewährleistet eine artefaktefreie Dehnungsmessung. Drei verschiedene Ansätze für neuartige Dehnungssensoren mit kleinem Querschnitt wurden in dieser Arbeit untersucht. / Strain sensors are used for structural health monitoring issues, certainly in parts with high safety requirements made of fibre-reinforced plastic composites. The integration of these sensors inside the parts protects them against any mechanical and corrosive impact. The sensor functionality can be enhanced by integration. There is a lot of international research effort to further develop integratable strain sensors. Different approaches are currently pursued. This thesis presents the results of investigations on three different approaches for novel strain sensors. The main goal of these investigations was to minimise the sensor diameter down to the diameter of reinforcing fibres. The small diameter allows for an optimum and artefact free integration of the sensors. The formation of resin nests and notches to the material structure can be prevented by integrating sensor with a smaller diameter. The strain measurement and monitoring is enhanced and more reliable then.

No description available.

No description available.