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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
231

Advanced Connection Allocation Techniques in Circuit Switching Network on Chip

Chen, Yong 14 September 2017 (has links) (PDF)
With the advancement of semiconductor technology, the System on Chip (SoC) is becoming more and more complex, so the on-chip communication has become a bottleneck of SoC Design. Since the traditional bus system is inefficient and not scalable, the Network-On-Chip (NoC) has emerged as the promising communication mechanism for complex SoCs. As some systems have specific performance requirements, such as a minimum throughput (for real-time streaming data) or bounded latency (for interrupts, process synchronization, etc), communication with Guaranteed Service (GS) support becomes crucial for predictable SoC architectures. Circuit Switching (CS) is a popular approach to support GS, which firstly has to allocate an exclusively connection (circuit) between the source and destination nodes, and then the data packets are delivered over this connection. However, it is inefficient and inflexible because the resource is occupied by single connection during its whole lifetime, which can block other communications. Hence, two extensions of CS have been proposed to share resources: i) Time-Division Multiplexing (TDM), in which the available link capacity is split into multiple time slots to be shared by different flows in TDM scheme; and ii) Space-Division-Multiplexing (SDM), in which only a subset (sub-channel) of the link wires is exclusively allocated to a specific connection, while the remaining wires of the link can be used by other flows. The connection allocation is critical for CS, since the data delivery can start only after the associated connection is allocated. In this thesis, we propose a dedicated hardware connection allocator to solve the dynamic connection allocation problem for CS NoCs, which has to i) allocate a contention-free path between source-destination pairs and ii) allocate appropriate portions of link bandwidth (appropriate number of time slots and subsets) along the path. The dedicated connection allocator, called NoCManager, solves the connection allocation problem by employing a trellis-search based shortest path algorithm. The trellis search can explore all possible paths between source node and destination. Moreover, it shall find the requested path in a fixed low latency and can guarantee the path optimality in terms of path length if the path is available. In this thesis, two different trellis graphs, Forward-Backtrack trellis and Register-Exchange trellis are proposed. The Forward-Backtrack trellis completes the path search in two steps: forward search and backtracking. Firstly, the forward search begins at source node that traverses the network to find the free path. When destination node is reached, the backtrack starts from destination to select the survivor path and collect the associated path parameters. However, Register-Exchange trellis saves the entire survivor path sequences during forward search. Consequently, the backtracking step can be omitted, and thus the allocation time is halved compared to forward-backtrack approaches. Moreover, each trellis graph consists of three categories, unfolded structure, folded structure and bidirectional structure. The unfolded structure can provide high allocation speed while folded structure is more efficient from a hardware point of view. The bidirectional structure starts the search at two sides, source node and destination node simultaneously, so the allocation speed is 2 times faster than previous unidirectional search. Furthermore, in order to address the scalability issue of previous centralized systems, the partitioned architecture (i.e. spatial partitioning technique) is proposed to divide the large system into multiple smaller differentiated logical partitions served by local NoCManagers. This partitioning technique keeps the request load of the manager and manager-node communication overhead moderate. Inside each partition, the path search problem is solved by a local manager with trellis-search algorithm. To establish a path that crosses partitions, the managers communicate with each other in distributed manner to converge the global path. In order to further enhance the path diversity and resource utilization, we adopt the combined TDM and SDM technique. In combined TDM-SDM approach, each SDM sub-channel is split into multiple time slots so that can be shared by multiple flows. Hence, the number of sub-channels can be kept moderate to reduce router complexity, while still providing higher path diversity than TDM scheme. In order to investigate and optimize TDM-SDM partitioning strategy, we studied the influence of different TDM-SDM link partitioning strategies on success rate and path length that allowed us to find the optimal solution. The dedicated connection allocator using the trellis-search algorithm is employed for TDM, SDM and TDM-SDM CS. In the end, we present the router architecture that combines the circuit-switching network (for GS communication) and packet-switching network (for best-effort communication).
232

Resource Allocation for Multiple Access and Broadcast Channels under Quality of Service Requirements Based on Strategy Proof Pricing

Shen, Fei 16 April 2015 (has links) (PDF)
The efficient allocation of power is a major concern in today’s wireless communications systems. Due to the high demand in data rate and the scarcity of wireless resources such as power, the multi-user communication systems like the multiple access channel (MAC) and broadcast channel (BC) have become highly competitive environments for the users as well as the system itself. Theory of microeconomics and game theory provide the good analytical manner for the selfish and social welfare conflict problems. Instead of maximizing the system sum rate, our proposed system deals with fulfilling the utility (rate) requirement of all the users with efficient power allocation. The users formulate the signal to interference-plus-noise ratio (SINR) based quality-of-service (QoS) requirements. We propose the framework to allocate the power to each user with universal pricing mechanisms. The prices act as the control signal and are assumed to be some virtual currency in the wireless system. They can influence the physical layer operating points to meet the desired utility requirements. Centralized and distributed power allocation frameworks are discussed separately in the thesis with different pricing schemes. In wireless systems we have users that are rational in the game theoretic sense of making decisions consistently in pursuit of their own individual objectives. Each user’s objective is to maximize the expected value of its own payoff measured on a certain utility scale. Selfishness or self-interest is an important implication of rationality. Therefore, the mobiles which share the same spectrum have incentives to misinterpret their private information in order to obtain more utility. They might behave selfishly and show also malicious behavior by creating increased interference for other mobiles. Therefore, it is important to supervise and influence the operation of the system by pricing and priority (weights) optimization. In the centralized resource allocation, we study the general MAC and BC (with linear and nonlinear receiver) with three types of agents: the regulator, the system optimizer and the mobile users. The regulator ensures the QoS requirements of all users by clever pricing and prevents cheating. The simple system optimizer solves a certain system utility maximization problem to allocate the power with the given prices and weights (priorities). The linear and nonlinear pricing mechanisms are analyzed, respectively. It is shown that linear pricing is a universal pricing only if successive interference cancellation (SIC) for uplink transmission or dirty paper coding (DPC) for downlink transmission is applied at the base station (BS). For MAC without SIC, nonlinear pricing which is logarithmic in power and linear in prices is a universal pricing scheme. The prices, the resulting cost terms, the optimal power allocation to achieve the QoS requirement of each user in the feasible rate region are derived in closed form solutions for MAC with and without SIC using linear and nonlinear pricing frameworks, respectively. The users are willing to maximize their achievable rate and minimize their cost on power by falsely reporting their channel state information (CSI). By predicting the best cheating strategy of the malicious users, the regulator is able to detect the misbehavior and punish the cheaters. The infinite repeated game (RG) is proposed as a counter mechanism with the trigger strategy using the trigger price. We show that by anticipating the total payoff of the proposed RG, the users have no incentive to cheat and therefore our framework is strategy-proof. In the distributed resource allocation, each user allocates its own power by optimizing the individual utility function. The noncooperative game among the users is formulated. The individual prices are introduced to the utility function of each user to shift the Nash equilibrium (NE) power allocation to the desired point. We show that by implicit control of the proposed prices, the best response (BR) power allocation of each user converges rapidly. The Shannon rate-based QoS requirement of each user is achieved with minimum power at the unique NE point. We analyse different behavior types of the users, especially the malicious behavior of misrepresenting the user utility function. The resulting NE power allocation and achievable rates of all users are derived when malicious behavior exists. The strategy-proof mechanism is designed using the punishment prices when the types of the malicious users are detected. The algorithm of the strategy-proof noncooperative game is proposed. We illustrate the convergence of the BR dynamic and the Price of Malice (PoM) by numerical simulations. The uplink transmission within the single cell of heterogeneous networks is exactly the same model as MAC. Therefore, the results of the pricing-based power allocation for MAC can be implemented into heterogeneous networks. Femtocells deployed in the Macrocell network provide better indoor coverage to the user equipments (UEs) with low power consumption and maintenance cost. The industrial vendors show great interest in the access mode, called the hybrid access, in which the macrocell UEs (MUEs) can be served by the nearby Femtocell Access Point (FAP). By adopting hybrid access in the femtocell, the system energy efficiency is improved due to the short distance between the FAP and MUEs while at the same time, the QoS requirements are better guaranteed. However, both the Macrocell base station (MBS) and the FAP are rational and selfish, who maximize their own utilities. The framework to successively apply the hybrid access in femtocell and fulfill the QoS requirement of each UE is important. We propose two novel compensation frameworks to motivate the hybrid access of femtocells. To save the energy consumption, the MBS is willing to motivate the FAP for hybrid access with compensation. The Stackelberg game is formulated where the MBS serves as the leader and the FAP serves as the follower. The MBS maximizes its utility by choosing the compensation prices. The FAP optimizes its utility by selecting the number of MUEs in hybrid access. By choosing the proper compensation price, the optimal number of MUEs served by the FAP to maximize the utility of the MBS coincides with that to maximize the utility of the FAP. Numerous simulation results are conducted, showing that the proposed compensation frameworks result in a win-win solution. In this thesis, based on game theory, mechanism design and pricing framework, efficient power allocation are proposed to guarantee the QoS requirements of all users in the wireless networks. The results are applicable in the multi-user systems such as heterogeneous networks. Both centralized and distributed allocation schemes are analyzed which are suitable for different communication scenarios. / Aufgrund der hohen Nachfrage nach Datenrate und wegen der Knappheit an Ressourcen in Funknetzen ist die effiziente Allokation von Leistung ein wichtiges Thema in den heutigen Mehrnutzer-Kommunikationssystemen. Die Spieltheorie bietet Methoden, um egoistische und soziale Konfliktsituationen zu analysieren. Das vorgeschlagene System befasst sich mit der Erfüllung der auf Signal-zu-Rausch-und-Interferenz-Verhältnis (SINR) basierenden Quality-of-Service (QoS)-Anforderungen aller Nutzer mittels effizienter Leistungsallokation, anstatt die Übertragungsrate zu maximieren. Es wird ein Framework entworfen, um die Leistungsallokation mittels universellen Pricing-Mechanismen umzusetzen. In der Dissertation werden zentralisierte und verteilte Leistungsallokationsalgorithmen unter Verwendung verschiedener Pricing-Ansätze diskutiert. Die Nutzer in Funksystemen handeln rational im spieltheoretischen Sinne, indem sie ihre eigenen Nutzenfunktionen maximieren. Die mobilen Endgeräte, die dasselbe Spektrum nutzen, haben den Anreiz durch bewusste Fehlinterpretation ihrer privaten Informationen das eigene Ergebnis zu verbessern. Daher ist es wichtig, die Funktionalität des Systems zu überwachen und durch Optimierung des Pricings und Priorisierungsgewichte zu beeinflussen. Für den zentralisierten Ressourcenallokationsansatz werden der allgemeine Mehrfachzugriffskanal (Multiple Access Channel, MAC) und der Broadcastkanal (BC) mit linearen bzw. nichtlinearen Empfängern untersucht. Die Preise, die resultierenden Kostenterme und die optimale Leistungsallokation, mit der die QoS-Anforderungen in der zulässigen Ratenregion erfüllt werden, werden in geschlossener Form hergeleitet. Lineare und nichtlineare Pricing-Ansätze werden separat diskutiert. Das unendlich oft wiederholte Spiel wird vorgeschlagen, um Spieler vom Betrügen durch Übermittlung falscher Kanalinformationen abzuhalten. Für die verteilten Ressourcenvergabe wird das nichtkooperative Spiel in Normalform verwendet und formuliert. Die Nutzer wählen ihre Sendeleistung zur Maximierung ihrer eigenen Nutzenfunktion. Individuelle Preise werden eingeführt und so angepasst, dass die QoS-Anforderungen mit der Leistungsallokation im eindeutigen Nash-Gleichgewicht erfüllt werden. Verschiedene Arten des Nutzerverhaltens werden bezüglich der Täuschung ihrer Nutzenfunktion analysiert, und ein Strategy-Proof-Mechanismus mit Strafen wird entwickelt. Die Ergebnisse für den MAC sind anwendbar auf heterogene Netzwerke, wobei zwei neuartige Ansätze zur Kompensation bereitgestellt werden, die den hybriden Zugang zu Femtozell-Netzwerken motivieren. Mithilfe des Stackelberg-Spiels wird gezeigt, dass die vorgeschlagenen Ansätze in einer Win-Win-Situation resultieren.
233

Modellierung und Entwurf von resonanten Mikroaktoren mit elektrostatischem Antrieb / Modelling and design of resonant microactuators with electrostatic drive

Klose, Thomas 15 April 2016 (has links) (PDF)
Resonante Mikrobauelemente mit elektrostatischem Antrieb finden seit einigen Jahren vermehrt Anwendung in vielen Bereichen der Technik. So beruhen beispielsweise Drehraten- oder Beschleunigungssensoren, die im Automobilbau eingesetzt werden auf diesem Prinzip. Neue Anwendungsfelder ergeben sich vor allem für Aktoren, beispielsweise für die am Fraunhofer IPMS entwickelten Mikroscannerspiegel mit Out-of-plane-comb-Antrieb. Sie dienen zur geometrischen Ablenkung von Licht und können zur Realisierung von hochintegrierten Systemen zur Ausgabe (Laser-Projektor) oder Aufnahme (Laser-Imager) von Daten genutzt werden. Zum Entwurf von Mikroaktoren gibt es eine Reihe von Arbeiten, die sich meist auf ein konkretes Antriebsprinzip beziehen oder den Entwurf im Allgemeinen behandeln. Die vorliegende Arbeit verfolgt daher das Ziel, speziell die Randbedingungen beim Entwurf resonanter Mikroaktoren mit Out-of-plane-comb-Antrieb zu identifizieren bzw. zu systematisieren sowie die gewonnenen Erkenntnisse in einem effizienten Entwurfsprozess umzusetzen. Dabei sollen möglichst auch relevante nichtlineare Effekte berücksichtigt werden, sodass sich neue Möglichkeiten zur Optimierung der Bauelemente und damit zur Erweiterung des Entwurfsraums ergeben. / Electrostatically driven microsystems are utilized in technical systems for several years. For instance, they are used in automotive applications as acceleration sensors or angular rate sensors. New fields of applications appear especially for actuators. The scanning micromirror of the Fraunhofer Institute for Photonic Microsystems is such an actuator. It is a micro-­optical-­electrical microsystem (MOEMS) which is driven resonantly by an electrostatic comb drive and can be used in scanning laser imaging systems or laser projectors. Several technical and scientific publications occupy with the design and the simulation of microactuators, which refer usually to a concrete drive principle or to the issues of design in general. The intention of this thesis is to identify and systematize particularly the boundary conditions of design regarding to resonant micro actuators with out-­of-­plane­comb drive. The findings are implemented in efficient design tools and design processes. One emphasis thereby is the investigation of nonlinear properties and effects. This includes geometrically non-­linearities of suspensions as well as non-linearities caused by fluid damping and the electrostatic comb drive. The findings are utilized in an analytical, nonlinear stability analysis of the device's equation of motion as well as in an object oriented software library for the MATLAB environment, which can be used to create nonlinear reduced order models of scanning micromirrors. With the developed techniques for design and optimization the available parameter range of scanning micromirrors can be extended. By that means, it is possible to improve the properties of existing devices as well as create new devices with outreaching performance.
234

Off-state Impact on FDSOI Ring Oscillator Degradation under High Voltage Stress

Trommer, Jens, Havel, Viktor, Chohan, Talha, Mehmood, Furqan, Slesazeck, Stefan, Krause, Gernot, Bossu, Germain, Arfaoui, Wafa, Mühlhoff, Armin, Mikolajick, T. 09 December 2021 (has links)
The degradation predicted by classical DC reliability methods, such as bias temperature instability (BTI) and hot carrier injection (HCI), might not translate sufficiently to the AC conditions, which are relevant on the circuit level. The direct analysis of circuit level reliability is therefore an essential task for hardware qualification in the near future. Ring oscillators (RO) offer a good model system, where both BTI and HCI contribute to the degradation. In this work, it is qualitatively shown that the additional off-state stress plays a crucial role at very high stress voltages, beyond upper usage boundaries. To yield an accurate RO lifetime prediction a frequency measurement setup with high resolution is used, which can resolve small changes in frequency during stress near operation conditions. An ACDC conversion model is developed predicting the resulting frequency change based on DC input data. From the extrapolation to 10 years of circuit lifetime the model predicts a very low frequency degradation below 0.2% under nominal operation conditions, where the off-state has a minor influence.
235

Hafnium oxide based ferroelectric devices for memories and beyond

Mikolajick, Thomas, Schroeder, Uwe, Slesazeck, Stefan 10 December 2021 (has links)
Ferroelectricity is a material property were a remanent polarization exists under zero electrical field that can be reversed by applying an electrical field [1]. As consequence, two nonvolatile states exist that can be switched by an electrical field. This feature makes ferroelectrics ideally suited for nonvolatile memories with low write energy. Therefore, already in the 1950s first attempts have been made to realize ferroelectric nonvolatile memories based on ferroelectric barium titanate (BTO) crystals having evaporated electrodes on both sides [2]. The success of this approach was hindered by disturb issues that could be solved in the early 1990s by adding a transistor device as a selector [3]. Such a memory is referred to as a ferroelectric random access memory (FeRAM). Since reading of the ferroelectric polarization from a capacitor requires switching of the ferroelectric [1], the information will be destroyed and a write back is necessary. This can be avoided if the ferroelectric is placed inside of the gate stack of a MOS transistor resulting in a ferroelectric field effect transistor (FeFET) [1]. Conventional ferroelectric materials like BTO or lead- zirconium titanate (PZT) cannot be placed directly on silicon since unwanted interface reactions will occur. The necessary interface layer together with the space charge region of the transistor device leads to a rather low capacitance in series with the ferroelectric dielectric and consequently results in a strong depolarization field that has destroyed the nonvolatility of the FeFET device for many years and hinters scaling as well [4]. Today FeRAM devices are established on the market [3,5], but are limited to niche application since scaling is hindered by many integration problems associated to materials like PZT.
236

Phase, Frequency, and Timing Synchronization in Fully Digital Receivers with 1-bit Quantization and Oversampling

Schlüter, Martin 16 November 2021 (has links)
With the increasing demand for faster communication systems, soon data rates in the terabit regime (100 Gbit/s and beyond) are required, which yields new challenges for the design of analog-to-digital converters (ADCs) since high bandwidths imply high sampling rates. For sampling rates larger than 300MHz, which we now achieve with 5G, the ADC power consumption per conversion step scales quadratically with the sampling rate. Thus, ADCs become a major energy consumption bottleneck. To circumvent this problem, we consider digital receivers based on 1-bit quantization and oversampling. We motivate this concept by a brief comparison of the energy efficiency of a recently proposed system employing 1-bit quantization and oversampling to the conventional approach using high resolution quantization and Nyquist rate sampling. Our numerical results show that the energy efficiency can be improved significantly by employing 1-bit quantization and oversampling at the receiver at the cost of increased bandwidth. The main part of this work is concerned with the synchronization of fully digital receivers using 1-bit quantization and oversampling. As a first step, we derive performance bounds for phase, timing, and frequency estimation in order to gain a deeper insight into the impact of 1-bit quantization and oversampling. We identify uniform phase and sample dithering as crucial to combat the non-linear behavior introduced by 1-bit quantization. This dithering can be implemented by sampling at an irrational intermediate frequency and with an oversampling factor with respect to the symbol rate that is irrational, respectively. Since oversampling results in noise correlation, a closed form expression of the likelihood function is not available. To enable an analytical treatment we thus study a system model with white noise by adapting the receive filter bandwidth to the sampling rate. Considering the aforementioned dithering, we obtain very tight closed form lower bounds on the Cramér-Rao lower bound (CRLB) in the large sample regime. We show that with uniform phase and sample dithering, all large sample properties of the CRLB of the unquantized receiver are preserved under 1-bit quantization, except for a signal-to-noise ratio (SNR) dependent performance loss that can be decreased by oversampling. For the more realistic colored noise case, we discuss a numerically computable upper bound of the CRLB and show that the properties of the CRLB for white noise still hold for colored noise except that the performance loss due to 1-bit quantization is reduced. Assuming a neglectable frequency offset, we use the least squares objective function to derive a typical digital matched filter receiver with a data-and timing-aided phase estimator and a timing estimator that is based on square time recovery. We show that both estimators are consistent under very general assumptions, e.g., arbitrary colored noise and stationary ergodic transmit symbols. Performance evaluations are done via simulations and are compared against the numerically computable upper bound of the CRLB. For low SNR the estimators perform well but for high SNR they converge to an error floor. The performance loss of the phase estimator due to decision-directed operation or estimated timing information is marginal. In summary, we have derived practical solutions for the design of fully digital receivers using 1-bit quantization and oversampling and presented a mathematical analysis of the proposed receiver structure. This is an important step towards enabling energy efficient future wireless communication systems with data rates of 100 Gbit/s and beyond.
237

Propagation effects influencing polarimetric weather radar measurements

Otto, Tobias 16 March 2011 (has links)
Ground-based weather radars provide information on the temporal evolution and the spatial distribution of precipitation on a macroscopic scale over a large area. However, the echoes measured by weather radars are always a superposition of forward and backward scattering effects which complicates their interpretation. The use of polarisation diversity enhances the number of independent observables measured simultaneously. This allows an effective separation of forward and backward scattering effects. Furthermore, it extends the capability of weather radars to retrieve also microphysical information about the precipitation. The dissertation at hand introduces new aspects in the field of polarimetric, ground-based, monostatic weather radars at S-, C-, and X-band. Relations are provided to change the polarisation basis of reflectivities. A fully polarimetric weather radar measurement at circular polarisation basis is analysed. Methods to check operationally the polarimetric calibration of weather radars operating at circular polarisation basis are introduced. Moreover, attenuation correction methods for weather radar measurements at linear horizontal / vertical polarisation basis are compared to each other, and the robustly working methods are identified. / Bodengebundene Wetterradare bieten Informationen über die zeitliche Entwicklung und die räumliche Verteilung von Niederschlag in einer makroskopischen Skala über eine große Fläche. Die Interpretation der Wetterradarechos wird erschwert, da sie sich aus einer Überlagerung von Vorwärts- und Rückwärtsstreueffekten ergeben. Die Anzahl der unabhängigen Wetterradarmessgrößen kann durch den Einsatz von Polarisationsdiversität erhöht werden. Dies ermöglicht eine effektive Trennung von Vorwärts- und Rückwärtsstreueffekten. Desweiteren erlaubt es die Bestimmung von mikrophysikalischen Niederschlagsparametern. Die vorliegende Dissertation betrachtet neue Aspekte für polarimetrische, bodengebundene, monostatische Wetterradare im S-, C- und X-Band. Gleichungen zur Polarisationsbasistransformation von Reflektivitätsmessungen werden eingeführt. Eine vollpolarimetrische Wetterradarmessung in zirkularer Polarisationsbasis wird analysiert. Neue Methoden, die eine Überprüfung der polarimetrischen Kalibrierung von Wetterradarmessungen in zirkularer Polarisationsbasis erlauben, werden betrachtet. Weiterhin werden Methoden zur Dämpfungskorrektur von Wetterradarmessungen in linearer horizontaler / vertikaler Polarisationsbasis miteinander verglichen und Empfehlungen von zuverlässigen Methoden gegeben.
238

Netzorientierte Fuzzy-Pattern-Klassifikation nichtkonvexer Objektmengenmorphologien

Hempel, Arne-Jens 06 September 2011 (has links)
Die Arbeit ordnet sich in das Gebiet der unscharfen Klassifikation ein und stellt im Detail eine Weiterführung der Forschung zur Fuzzy-Pattern-Klassifikation dar. Es handelt sich dabei um eine leistungsfähige systemtheoretische Methodik zur klassifikatorischen Modellierung komplexer, hochdimensionaler, technischer oder nichttechnischer Systeme auf der Basis von metrischen Messgrößen und/oder nichtmetrischen Experten-Bewertungen. Die Beschreibung der Unschärfe von Daten, Zuständen und Strukturen wird hierbei durch einen einheitlichen Typ einer Zugehörigkeitsfunktion des Potentialtyps realisiert. Ziel der Betrachtungen ist die weiterführende Nutzung des bestehenden Klassenmodells zur unscharfen Beschreibung nichtkonvexer Objektmengenmorphologien. Ausgehend vom automatischen datengetriebenen Aufbau der konvexen Klassenbeschreibung, deren vorteilhaften Eigenschaften sowie Defiziten wird im Rahmen der Arbeit eine Methodik vorgestellt, die eine Modellierung beliebiger Objektmengenmorphologien erlaubt, ohne das bestehende Klassifikationskonzept zu verlassen. Kerngedanken des Vorgehens sind: 1.) Die Aggregation von Fuzzy-Pattern-Klassen auf der Basis so genannter komplementärer Objekte. 2.) Die sequentielle Verknüpfung von Fuzzy-Pattern-Klassen und komplementären Klassen im Sinne einer unscharfen Mengendifferenz. 3.) Die Strukturierung des Verknüpfungsprozesses durch die Clusteranalyse von Komplementärobjektmengen und damit der Verwendung von Konfigurationen aus komplementären Fuzzy-Pattern-Klassen. Das dabei gewonnene nichtkonvexe Fuzzy-Klassifikationsmodell impliziert eine Vernetzung von Fuzzy-Klassifikatoren in Form von Klassifikatorbäumen. Im Ergebnis entstehen Klassifikatorstrukturen mit hoher Transparenz, die - neben der üblichen zustandsorientierten klassifikatorischen Beschreibung in den Einzelklassifikatoren - zusätzliche Informationen über den Ablauf der Klassifikationsentscheidungen erfassen. Der rechnergestützte Entwurf und die Eigenschaften der entstehenden Klassifikatorstruktur werden an akademischen Teststrukturen und realen Daten demonstriert. Die im Rahmen der Arbeit dargestellte Methodik wird in Zusammenhang mit dem Fuzzy-Pattern-Klassifikationskonzept realisiert, ist jedoch aufgrund ihrer Allgemeingültigkeit auf eine beliebige datenbasierte konvexe Klassenbeschreibung übertragbar. / This work contributes to the field of fuzzy classification. It dedicates itself to the subject of "Fuzzy-Pattern-Classification", a versatile method applied for classificatory modeling of complex, high dimensional systems based on metric and nonmetric data, i.e. sensor readings or expert statements. Uncertainties of data, their associated morphology and therewith classificatory states are incorporated in terms of fuzziness using a uniform and convex type of membership function. Based on the properties of the already existing convex Fuzzy-Pattern-Class models and their automatic, data-driven setup a method for modeling nonconvex relations without leaving the present classification concept is introduced. Key points of the elaborated approach are: 1.) The aggregation of Fuzzy-Pattern-Classes with the help of so called complementary objects. 2.) The sequential combination of Fuzzy-Pattern-Classes and complementary Fuzzy-Pattern-Classes in terms of a fuzzy set difference. 3.) A clustering based structuring of complementary Fuzzy-Pattern-Classes and therewith a structuring of the combination process. A result of this structuring process is the representation of the resulting nonconvex fuzzy classification model in terms of a classifier tree. Such a nonconvex Fuzzy-Classifier features high transparency, which allows a structured understanding of the classificatory decision in working mode. Both the automatic data-based design as well as properties of such tree-like fuzzy classifiers will be illustrated with the help of academic and real word data. Even though the proposed method is introduced for a specific type of membership function, the underlying idea may be applied to any convex membership function.
239

Prediction of the Average Value of State Variables for Switched Power Converters Considering the Modulation and Measuring Method

Rojas Vidal, Sebastian Sady 29 January 2020 (has links)
In power electronics, the switched converter plays a fundamental role in the efficient conversion and dynamical control of electrical energy. Due to the switching operation of these systems, overlaid disturbances come into existence in addition to the desired behavior of the variables, causing deviations in the current and voltages. From a control perspective, these disturbances are of no interest since they cannot be compensated. They can even alter the measurements given to the control system, affecting its behavior. Furthermore, during the control design, averaged models are often used, by which the switching operation is somehow disregarded. They consider instead the average behavior of the system variables. Thus, it is essential that the measuring setup provides a measurement of the average value to the control system. To accomplish this goal, there are in practice different approaches. For example, the disturbances originated by the switching operation can be either suppressed using an analog or digital filter, or the sampling of the variables can be carried out in a suitable manner, synchronous to the carrier of the modulation method. Unfortunately, the use of filters adds an extra phase shift or delay to the control loop, reducing its dynamical performance. Moreover, the synchronous sampling method provides a good approximation of the average value only if certain conditions are met, otherwise a distortion due to aliasing takes place. A method is developed in this work to predict, in every switching cycle, the average value of the system variables in a switched power converter. In this context, the work presents an alternative method to carry out the measurement of the average value, avoiding the principal drawbacks of the standard measuring methods. To achieve this, a suitable model of the converter is used, incorporating the modulation method and the type of analog-to-digital converter, either a conventional sample-and-hold or a sigma-delta converter. The measurement given by the analog-to-digital converter is used to predict the time behavior of the system variables during the present switching period and then to evaluate its average value, before the period is completed. The method allows to obtain simultaneously the average value of currents and voltages, to get rid of the delay introduced by filtering, and to avoid the drawback of sampling in the measurement, i.e. aliasing. In this work, an overview of the standard measuring methods for switched power converters is first presented. The problematics that arise from the sampling process are also discussed. Next, the theoretical grounds of the method are developed and the tools needed to implement it are derived. To illustrate its applicability, the method is used first in DC-DC converters, where the case of the buck converter is analyzed in detail. Similarly, the method is applied to a three-phase two-level voltage source converter. In both cases, simulation results and experimental verification are presented for different operational modes. The usage of the method in open and closed loop is discussed, and its effect in the system behavior is shown. The performance of the prediction method is contrasted with other standard measuring methods.
240

Untersuchungen zum Einfluss der elektrischen Felder auf das Design von Kompakthöchstspannungsmasten aus ultrahochfestem Beton (UHPC) und zur Identifizierung der elektrischen und thermischen Parameter des UHPCs

Bakka, Maher 11 October 2018 (has links)
Freileitungsmaste aus herkömmlichen Beton werden bereits heute in großer Zahl in Mittelspan-nungsnetzen eingesetzt. Im Bereich der Hochspannungsfreileitungen existieren bisher international nur wenige erste Freileitungen mit Masten aus herkömmlichen Beton. Um zukünftig Elektroenergie über große Entfernungen über Trassen mit geringen Flächenbedarf transportieren zu können, sind neue Hochspannungsfreileitungen in kompakter Bauweise notwendig. Um dieses Ziel zu erfüllen, sollen die Kompaktmaste aus ultra-hochfestem Beton (UHPC) hergestellt werden. Dafür ist eine neue Sorte von UHPC mit hoher Festigkeitsklasse zu entwickeln. Die mechanischen, elektrischen und thermischen Eigenschaften des neuen Betonmaterials waren zunächst unbekannt. Bisher gab es kaum Kenntnisse über die elektrischen und thermischen Belas-tungen, die auf die Betonmaste einer Freileitung in kompakter Bauweise einwirken. Ein Teilthema im interdisziplinären Forschungsprojekt „KoHöMaT“ (gefördert durch das Bundesmi-nisterium für Wirtschaft und Energie) war es, gemeinsam mit Forschungsinstituten (IMB, Fichtner, Lapp, Europoles, KIT, iBMB) die Materialparameter des neuen UHPC zu bestimmen. Den Einfluss der elektromagnetischen Belastungen auf die Lebensdauer und die Festigkeit des Ver-bundes aus Stahl und Beton habe ich untersucht. Aufgabe meiner Arbeit ist es auch, die elektrischen und thermischen Eigenschaften, wie die elektrische Leitfähigkeit, die elektrische Festigkeit, die Per-mittivität, den Verlustfaktor und die Wärmeleitfähigkeit experimentell zu bestimmen. Anhand der experimentellen Untersuchungen wurde der Versagensmechanismus des UHPC-Betons bei Span-nungsbelastung identifiziert. Die am Betonmast auftretenden elektrischen und thermischen Belas-tungen wurden mit Hilfe von verschiedenen FEM-Modellen berechnet und den gemessenen Fes-tigkeiten gegenübergestellt. Es wurde der Einfluss permanenter elektrischer Felder auf die mechanischen Eigenschaften des UHPC bestimmt. Hierfür wurde die Druckfestigkeit des Betons vor und nach Dauerversuchen bei verschiedenen Spannungsbelastung gemessen. Der Verbund zwischen Stahl und Beton wurde in Lastwechselversuchen thermisch hoch beansprucht und dessen mechanische Festigkeit vor und nach der thermischen Belastung bei Auszugsversuchen gemessen. Aufgrund der befürchtenden gesundheitlichen Risiken für Menschen und Tiere, sowie der gegen-seitigen Beeinflussung benachbarter elektronischer Systeme (EMV) dürfen die elektromagnetischen Felder von Freileitungen die jeweiligen maximal zulässigen Grenzwerte nicht überschreiten. Ich habe die Berechnungen der elektrischen und magnetischen Feldverteilung für die im Verbundvorhaben entwickelten Mastdesigns durchgeführt. Gemeinsam mit den Forschungsinstituten (Europoles, Fichtner, Lapp) wurden die Mastdesigns hinsichtlich der Feldverteilung optimiert. / The Overhead line towers made of conventional concrete are already used in large numbers in the medium voltage nowadays. So far, only a few towers of overhead transmission line made of con-ventional concrete which exists internationally in the area of high voltage. In order to be able to transmit electrical energy over long distances by routes of less floor space requirements, new high voltage overhead lines in compact construction are necessary. To achieve this goal, the compact towers have to be made of ultra-high-performance concrete (UHPC). Therefore, a new kind of UHPC with a high strength class has to be developed. For this kind of new concrete, the mechanical, electrical and thermal characteristics were unknown till now either, there was rare knowledge about the electric and thermal loads which have an effect on the concrete towers of an overhead line in compact construction method. The main purpose part of this interdisciplinary research project 'KoHöMaT “, which funded by the Federal Ministry for Economic Affairs and Energy), was to identify the material parameters of the new UHPC together with the following research institutes (IMB, Fichtner, Lapp, Europoles, KIT, iBMB). It was examined the influence of electromagnetic loads on the lifetime and its’ strength bond be-tween both of composite steel and concrete, also as my major involve was to determine the elec-trical and thermal properties experimentally, such as electrical conductivity, electrical strength, per-mittivity, dissipation factor and finally thermal conductivity. As a result, the failure mechanism of the UHPC under the electrical stresses has been identified then,the electrical and thermal loads on the concrete towers were calculated by using various FEM models accordingly, the measured values were used in the determination of electrical strength. All mentioned theoretical calculated parameters were compared with the real measured parameters. The influence of permanent electric fields on mechanical properties of the UHPC was determined as well. Mainly, the compressive strength of the concrete was measured before and after durability tests at different voltage loads. In addition, the composite (interface) between steel and concrete was thermal extremely loaded by alternating load tests. Its mechanical strength has been measured by pull-out tests before and after this thermal loads. Due to the fear of health risks for both humans and animals, as well as the mutual influence of neighboring electronic systems (EMV), the electromagnetic fields of open lines must not exceed the respective maximum permissible limit values. The calculations of the electrical and magnetic field distribution were carried out for the mast design developed in the composite project. Together with the other research institute (Europoles, Fichtner, Lapp). the tower designs were optimized with re-gard to the field distribution.

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