The electromechanical design and development of a sophisticated roller rig testing facility at the Railway Technologies Laboratory (RTL) of Virginia Polytechnic and State University (VT) is presented. The VT Roller Rig is intended for studying the complex dynamics and mechanics at the wheel-rail interface of railway vehicles in a controlled laboratory environment. Such measurements require excellent powering and driving architecture, high-performance motion control, accurate measurements, and relatively noise-free data acquisition systems. It is critical to accurately control the relative dynamics and positioning of rotating bodies to emulate field conditions. To measure the contact forces and moments, special care must be taken to ensure any noise, such as mechanical vibration, electrical crosstalk, and electromagnetic interference (EMI) are kept to a minimum. This document describes the steps towards design and development of all electromechanical subsystems of the VT Roller Rig, including the powertrain, power electronics, motion control systems, sensors, data acquisition units, safety and monitoring circuits, and general practices followed for satisfying the local and international codes of practice. The VT Roller Rig is comprised of a wheel and a roller in a vertical configuration that simulate the single-wheel/rail interaction in one-fourth scale. The roller is five times larger than the scaled wheel to keep the contact patch distortion that is inevitable with a roller rig to a minimum. This setup is driven by two independent AC servo motors that control the velocity of the wheel and roller using state-of-the-art motion control technologies. Six linear actuators allow for adjusting the simulated load, wheel angle of attack, rail cant, and lateral position of the wheel on the rail. All motion controls are performed using digital servo drives, manufactured by Kollmorgen, VA, USA. A number of sensors measure the contact patch parameters including force, torque, displacement, rotation, speed, acceleration, and contact patch geometry. A unified communication protocol between the actuators and sensors minimizes data conversion time, which allows for servo update rates of up to 48kHz. This provides an unmatched bandwidth for performing various dynamics, vibrations, and transient tests, as well as static steady-state conditions. The VT Roller Rig has been debugged and commissioned successfully. The hardware and software components are tested both individually and within the system. The VT Roller Rig can control the creepage within 0.3RPM of the commanded value, while actively controlling the relative position of the rotating bodies with an unprecedented level of accuracy, no more than 16nm of the target location. The contact force measurement dynamometers can dynamically capture the contact forces to within 13.6N accuracy, for up to 10kN. The instantaneous torque in each driveline can be measured with better than 6.1Nm resolution. The VT Roller Rig Motion Programming Interface (MPI) is highly flexible for both programmers and non-programmers. All common motion control algorithms in the servo motion industry have been successfully implemented on the Rig. The VT Roller Rig MPI accepts third party motion algorithms in C, C++, and any .Net language. It successfully communicates with other design and analytics software such as Matlab, Simulink, and LabVIEW for performing custom-designed routines. It also provides the infrastructure for linking the Rig's hardware with commercial multibody dynamics software such as Simpack, NUCARS, and Vampire, which is a milestone for hardware-in-the-loop testing of railroad systems. / Ph. D.

Les dernières décennies ont donné lieux à d'énormes progrès dans la simulation numérique des phénomènes physiques. D'une part grâce au raffinement des méthodes de discrétisation des équations aux dérivées partielles. Et d'autre part grâce à l'explosion de la puissance de calcul disponible. Pourtant, de nombreux problèmes soulevés en ingénierie tels que les simulations multi-physiques, les problèmes d'optimisation et de contrôle restent souvent hors de portée. Le dénominateur commun de ces problèmes est le fléau des dimensions. Un simple problème tridimensionnel requiert des centaines de millions de points de discrétisation auxquels il faut souvent ajouter des milliers de pas de temps pour capturer des dynamiques complexes. L'avènement des supercalculateurs permet de générer des simulations de plus en plus fines au prix de données gigantesques qui sont régulièrement de l'ordre du pétaoctet. Malgré tout, cela n'autorise pas une résolution ``exacte'' des problèmes requérant l'utilisation de plusieurs paramètres. L'une des voies envisagées pour résoudre ces difficultés est de proposer des représentations ne souffrant plus du fléau de la dimension. Ces représentations que l'on appelle séparées sont en fait un changement de paradigme. Elles vont convertir des objets tensoriels dont la croissance est exponentielle $n^d$ en fonction du nombre de dimensions $d$ en une représentation approchée dont la taille est linéaire en $d$. Pour le traitement des données tensorielles, une vaste littérature a émergé ces dernières années dans le domaine des mathématiques appliquées.Afin de faciliter leurs utilisations dans la communauté des mécaniciens et en particulier pour la simulation en mécanique des fluides, ce manuscrit présente dans un vocabulaire rigoureux mais accessible les formats de représentation des tenseurs et propose une étude détaillée des algorithmes de décomposition de données qui y sont associées. L'accent est porté sur l'utilisation de ces méthodes, aussi la bibliothèque de calcul texttt{pydecomp} développée est utilisée pour comparer l'efficacité de ces méthodes sur un ensemble de cas qui se veut représentatif. La seconde partie de ce manuscrit met en avant l'étude de l'écoulement dans une cavité entraînée à haut nombre de Reynolds. Cet écoulement propose une physique très riche (séquence de bifurcation de Hopf) qui doit être étudiée en amont de la construction de modèle réduit. Cette étude est enrichie par l'utilisation de la décomposition orthogonale aux valeurs propres (POD). Enfin une approche de construction ``physique'', qui diffère notablement des développements récents pour les modèles d'ordre réduit, est proposée. La connaissance détaillée de l'écoulement permet de construire un modèle réduit simple basé sur la mise à l'échelle des fréquences d'oscillation (time-scaling) et des techniques d'interpolation classiques (Lagrange,..). / Numerical simulation has experienced tremendous improvements in the last decadesdriven by massive growth of computing power. Exascale computing has beenachieved this year and will allow solving ever more complex problems. But suchlarge systems produce colossal amounts of data which leads to its own difficulties.Moreover, many engineering problems such as multiphysics or optimisation andcontrol, require far more power that any computer architecture could achievewithin the current scientific computing paradigm. In this thesis, we proposeto shift the paradigm in order to break the curse of dimensionality byintroducing decomposition and building reduced order models (ROM) for complexfluid flows.This manuscript is organized into two parts. The first one proposes an extendedreview of data reduction techniques and intends to bridge between appliedmathematics community and the computational mechanics one. Thus, foundingbivariate separation is studied, including discussions on the equivalence ofproper orthogonal decomposition (POD, continuous framework) and singular valuedecomposition (SVD, discrete matrices). Then a wide review of tensor formats andtheir approximation is proposed. Such work has already been provided in theliterature but either on separate papers or into a purely applied mathematicsframework. Here, we offer to the data enthusiast scientist a comparison ofCanonical, Tucker, Hierarchical and Tensor train formats including theirapproximation algorithms. Their relative benefits are studied both theoreticallyand numerically thanks to the python library texttt{pydecomp} that wasdeveloped during this thesis. A careful analysis of the link between continuousand discrete methods is performed. Finally, we conclude that for mostapplications ST-HOSVD is best when the number of dimensions $d$ lower than fourand TT-SVD (or their POD equivalent) when $d$ grows larger.The second part is centered on a complex fluid dynamics flow, in particular thesingular lid driven cavity at high Reynolds number. This flow exhibits a seriesof Hopf bifurcation which are known to be hard to capture accurately which iswhy a detailed analysis was performed both with classical tools and POD. Oncethis flow has been characterized, emph{time-scaling}, a new ``physics based''interpolation ROM is presented on internal and external flows. This methodsgives encouraging results while excluding recent advanced developments in thearea such as EIM or Grassmann manifold interpolation.

Le problème de la commande de machine asynchrone sans capteur mécanique de vitesse est très étudié dans les domaines de l'automatique et de l'électrotechnique. Ce travail porte sur la faisabilité de ce type de commande sur l'ensemble de la plage de vitesse et pour tout type de machine asynchrone afin d'être utilisée en traction ferroviaire. Une étude poussée de l'observabilité permet de définir une mesure quantitative continue de l'observabilité de la vitesse de la machine, appelée index d'observabilité. La synthèse d'un observateur confirme ainsi la correspondance entre les zones de faible index d'observabilité et celles où l'observation est de mauvaise qualité. L'index d'observabilité défini dans cette thèse permet donc de prédire les performances d'observation d'un système. L'originalité principale des travaux présentés tient dans l'utilisation de cet index d'observabilité dans la commande de la machine asynchrone sans capteur mécanique de vitesse. En tirant profit du degré de liberté qu'offre la variation d'amplitude du flux, nous proposons de garantir un index d'observabilité au-dessus d'un seuil tout en respectant les autres contraintes de la commande. L'observation de la vitesse devient alors précise sur toute la plage de vitesse, et un fonctionnement long est possible en tout point sans perturber le couple réalisé. Des expérimentations sur simulateur numérique viennent confirmer ces résultats, y compris lors de phases de patinage. L'observation des paramètres électriques est également étudiée afin de garantir la précision de l'observation de vitesse. Pour cela, la sensibilité de l'observation de vitesse aux variations de paramètres électriques et l'observabilité de ces paramètres sont étudiées, permettant de définir une nouvelle stratégie d'observation des paramètres électriques. Des essais sur banc de puissance, puis en application réelle sur un train régional, valident les performances de la commande sans capteur de vitesse proposée sur toute la plage de vitesse, et son adéquation aux contraintes d'une application ferroviaire. / The problem of speed sensorless control of induction machine is a well-studied problem in the field of automatic control and electrical engineering. This work addresses the problem of the feasibility of induction machine control over the whole speed range and for any type of induction machine, aiming at being used in a railway application. An intensive study of observability has defined a continuous quantitative measurement of the speed observability, named observability index. An observer was developped to confirme the correspondence between low-observability index areas and poor observation quality. The observability index defined in this thesis is thus a way to predict the observation performance of systems. The main originality of the work presented in this thesis is the use of this observability index in the induction machine speed sensorless drive. By taking advantage of the degree of freedom given by the variation of the flux amplitude, we propose to guarantee the observability index value above a given threshold while respecting the other constraints of the control. The speed observation becomes precise over the entire speed range, and a long time operation is possible on any point, without interfering with torque regulation. Experiments on real-time simulator confirm these results, including when slipping and sliding occurs. The electrical parameter observation is also studied to ensure the accuracy of speed observation. For this, the sensitivity of the speed observation to electrical parameter variations and the observability of these parameters are studied, leading to the definition of the electrical parameter observation strategy. The testings on power bench, and in real application on a regional train, validate the performance of the speed sensorless drive proposed on the entire speed range, and its suitability to the constraints of a railway application.

The VCOST budgeting tool uses a drive cycle simulator to improve fuel economy predictions for vehicle fleets. This drive cycle simulator needs to predict the efficiency of various components of the vehicle's powertrain including any differentials. Existing differential efficiency models either lack accuracy over the operating conditions considered or require too great an investment. A fundamental model for differential efficiency is a cost-effective solution for predicting the odd behaviors unique to a differential. The differential efficiency model itself combines the torque balance equation and the Navier-Stokes equations with models for gear pair, bearing, and seal efficiencies under a set of appropriate assumptions. Comparison of the model with existing data has shown that observable trends in differential efficiency are reproducible in some cases to within 10% of the accepted efficiency value over a range of torques and speeds that represents the operating conditions of the differential. Though the model is generally an improvement over existing curve fits, the potential exists for further improvement to the accuracy of the model. When the model performs correctly, it represents an immense savings over collecting data with comparable accuracy. / text

Ausgangspunkt der Untersuchung ist die Frage, ob Hybridkonzepte auf hydrostatischer Grundlage eine realistische Alternative zu elektrohybriden Antriebskonfigurationen für Dieseltriebwagen sein können. Die Untersuchung dieser Fragestellung erfolgt mit Hilfe von Simulationsmodellen, die auf der 1-d-Simulationsumgebung Imagine.Lab AMESim beruhen. Zunächst wird die fahrdynamische und antriebstechnische Modellierung eines dieselhydraulischen Regionaltriebwagens unter Berücksichtigung einer energiesparenden Fahrweise dargestellt. Ausgehend von Massenbilanzen werden untereinander vergleichbare Hybridkonfigurationen auf hydrostatischer (Gasdruckspeicher), elektrostatischer (Doppelschichtkondensatoren) und elektrochemischer (Li-Ionen-Speicher) Basis entwickelt. Die Modellierung der hydraulischen und elektrischen Antriebsstränge wird eingehend diskutiert. Die abgeleiteten Hybridkonfigurationen werden anschließend bezüglich spezieller Fahrspiele und Betriebskonzepte detailliert untersucht, um auf dieser Grundlage günstige Parametrierungen der Systeme ableiten und die günstigste Betriebsstrategie identifizieren zu können. Anschließend wird eine umfangreiche Analyse des Verhaltens der verschiedenen Hybridkonfigurationen auf ausgewählten realen Nahverkehrsstrecken vorgenommen. Im Rahmen der durchgeführten Simulationen wird schließlich das Kraftstoffeinsparpotential in Abhängigkeit von Streckenprofil, Hybridkonfiguration und Zugart ermittelt und verglichen.

This thesis describes the methods and procedures used in designing production lines, focusing on the production line for machining of train wheels. The thesis also describes the basic types of railway wheels, their design and important design elements. It also deals with the complete manufacturing process of train wheel from material selection through the technological processes of forming, heat treatment, mechanical tests, machining and non-destructive testing and measuring. Suitable equipment for the construction of automatic lines for machining, inspection and measurement of train wheels is selected according to the specified parameters of the wheel types, manufacturing productivity and production shop dimensions, These devices include vertical machining center, single-purpose machine for grease outlet drilling, device for ultrasonic inspection, magnetic particle inspecton device, measuring station and train wheel balancing machine. Several variants of the production line including detailed specification of manipulation cycle times is created. These variants are mutually compared and evaluated to find the optimal solution.

Quantification of stochastic or quantum systems by a joint probability density or wave function is a notoriously difficult computational problem, since the solution depends on all possible states (or realizations) of the system. Due to this combinatorial flavor, even a system containing as few as ten particles may yield as many as $10^{10}$ discretized states. None of even modern supercomputers are capable to cope with this curse of dimensionality straightforwardly, when the amount of quantum particles, for example, grows up to more or less interesting order of hundreds. A traditional approach for a long time was to avoid models formulated in terms of probabilistic functions, and simulate particular system realizations in a randomized process. Since different times in different communities, data-sparse methods came into play. Generally, they aim to define all data points indirectly, by a map from a low amount of representers, and recast all operations (e.g. linear system solution) from the initial data to the effective parameters. The most advanced techniques can be applied (at least, tried) to any given array, and do not rely explicitly on its origin. The current work contributes further progress to this area in the particular direction: tensor product methods for separation of variables. The separation of variables has a long history, and is based on the following elementary concept: a function of many variables may be expanded as a product of univariate functions. On the discrete level, a function is encoded by an array of its values, or a tensor. Therefore, instead of a huge initial array, the separation of variables allows to work with univariate factors with much less efforts. The dissertation contains a short overview of existing tensor representations: canonical PARAFAC, Hierarchical Tucker, Tensor Train (TT) formats, as well as the artificial tensorisation, resulting in the Quantized Tensor Train (QTT) approximation method. The contribution of the dissertation consists in both theoretical constructions and practical numerical algorithms for high-dimensional models, illustrated on the examples of the Fokker-Planck and the chemical master equations. Both arise from stochastic dynamical processes in multiconfigurational systems, and govern the evolution of the probability function in time. A special focus is put on time propagation schemes and their properties related to tensor product methods. We show that these applications yield large-scale systems of linear equations, and prove analytical separable representations of the involved functions and operators. We propose a new combined tensor format (QTT-Tucker), which descends from the TT format (hence TT algorithms may be generalized smoothly), but provides complexity reduction by an order of magnitude. We develop a robust iterative solution algorithm, constituting most advantageous properties of the classical iterative methods from numerical analysis and alternating density matrix renormalization group (DMRG) techniques from quantum physics. Numerical experiments confirm that the new method is preferable to DMRG algorithms. It is as fast as the simplest alternating schemes, but as reliable and accurate as the Krylov methods in linear algebra.

Sverige planerar för en av de största infrastrukturinvesteringarna någonsin i Sveriges historia. I fokus står en ny höghastighetsjärnväg mellan Stockholm, Göteborg och Malmö som ska möjliggöra resor på två till två och en halv timme mellan städerna. Runt denna investering finns en ambition att samla andra samhällsbyggande åtgärder, som ökat bostadsbyggande och förbättringar i lokal och regional kollektivtrafik, för att genom en samordnad planering få ut så stora nyttor som möjligt. För detta ändamål har regeringen tillsatt den statliga utredningen Sverigeförhandlingen. En viktig del av deras arbete är att få fram en finansieringslösning för den nya statliga transportinfrastrukturen där medfinansiering från kommuner, regioner och andra aktörer står för en betydande andel. Idén kring medfinansiering är baserad på att aktörerna ska bidra till finansieringen som motsvarar de nyttor transportinfrastrukturen bidrar till. Alltså måste det gå att uppskatta att på förhand hur mycket nyttor som uppstår och vad de är värda. Sverigeförhandlingen har valt klassificera nyttorna i sex kategorier där ”social nyttor” är en av dessa. Däremot finns ingen etablerad metodik för att uppskatta dessa. Det här examensarbetet undersöker vilken social påverkan transportinfrastrukturen ger upphov till. Detta görs genom att studera samband mellan tillgänglighet, alltså hur transportinfrastrukturen ger möjlighet för människor att nå olika målpunkter, och ett antal sociala förhållanden. Tillgänglighetsmåttet valdes utifrån studier av tidigare forskning samt etablerade modeller för uppskattning av andra nyttor av transportinfrastruktur. För att veta vilka sociala förhållanden som är intressanta att undersöka har en studie av Svensk och internationell litteratur på området genomförts. Sambandsanalysen bygger på statistiska metoder där data för Sveriges kommuner används. Metoden ger möjlighet till att identifiera samvariation mellan tillgänglighet och sociala förhållanden men är inte tillräcklig för att säkerställa att tillgänglighet är en orsak till de sociala förhållandena. Resultaten tyder på att tillgänglighet har statistiskt signifikanta samband med ett antal indikatorer för sociala förhållanden. Exempel på två av dessa är ungdomsidrottande och andelen barn som går i förskola. Det visade sig att de flesta av de sociala förhållanden som har signifikanta samband med tillgänglighet har en samvariation som tyder på att tillgänglighet korrelerar med positiva sociala förhållanden. Detta tyder på att tillgänglighet kan ha samband med faktorer som kan tolkas som sociala nyttor. Dock kan inget sägas om tillgänglighet är en orsak till detta eller om det är någon icke studerad orsak som ger upphov till detta. Dessutom påverkas tillgänglighetsmåttet av andra faktorer än enbart tillgång till transportinfrastruktur och därför går det inte utifrån dessa samband att säkert säga att de beror på transportsystemet. För att sociala nyttor ska kunna kvantifieras och ligga till grund för medfinansiering krävs vidare studier. En viktig uppgift är att med hjälp av bättre data och mer avancerade metoder få fram bättre uppskattningar av sambanden samt orsaksrelationerna. Det krävs också studier för hur sociala nyttor ska värderas i monetära termer ur ett samhällsekonomiskt perspektiv. / Sweden is currently planning for one of its largest investments in transport infrastructure ever. A cornerstone in the project is a new high speed railroad between Stockholm, Gothenburg and Malmö. A considerable portion of the funding will consist of co-funding from municipalities, regions and private actors that will benefit from the infrastructure. The amount of co-funding is based on the total benefits that each actor will receive. Therefore these benefits must be able to be quantified. This report aims to study relationships between transport infrastructure and a number of social consequences that previous research has indicated being interesting. The method used is based on econometric methods that enable identification of statistical relationships using a simple linear model. This requires measures of transport infrastructure and indicators for social well-being which are chosen through a study of literature and established models quantifying wider economic benefits from transport infrastructure.The report suggests that a gravitybased accessibility measure is suitable for quantifying transport infrastructure in this context. The results from the econometrical model ssuggest that there are several significant relationships between accessibility and social well-being. In general accessibility seems to correlate with positive social consequences. However it is likely that endogeneity is biasing the results and make it difficult to draw any conclusions on causal relationships. It is stated that further research studying these relationships more carefully with better adapted data for the purpose is required to be able to obtain quantified estimates that can be used in co-funding of transport infrastructure.

Neuronen sind erregbare Systeme. Ihre Antwort auf Anregungen oberhalb eines bestimmten Schwellwertes sind Pulse. Häufig wird die Pulserzeugung von verschiedenen Rückkopplungsmechanismen beeinflusst, die auf langsamen Zeitskalen agieren. Das kann zu Phänomenen wie Feuerraten-Adaptation, umgekehrter Feuerraten-Adaptation oder zum Feuern von Pulsen in Salven führen. Weiterhin sind Neuronen verschiedenen Rauschquellen ausgesetzt und wechselwirken mit anderen Neuronen, in neuronalen Netzen. Doch wie beeinflusst das Zusammenspiel von Rückkopplungsmechanismen, Rauschen und der Wechselwirkung mit anderen Neuronen die Pulserzeugung? Diese Arbeit untersucht, wie die Pulserzeugung in rauschgetriebenen erregbaren Systemen von langsamen Rückkopplungsmechanismen und der Wechselwirkung mit anderen erregbaren Systemen beeinflusst wird. Dabei wird die Pulserzeugung in drei Szenarien betrachtet: (i) in einem einzelnen erregbaren System, das um einen langsamen Rückkopplungsmechanismus erweitert wurde, (ii) in gekoppelten erregbaren Systemen und (iii) in stark gekoppelten salvenfeuernden Neuronen. In jedem dieser Szenarien wird die Pulsstatistik mit Hilfe von analytischen Methoden und Computersimulationen untersucht. Das wichtigste Resultat im ersten Szenario ist, dass das Zusammenspiel von einer stark anregenden Rückkopplung und Rauschen zu rauschkontrollierter Bistabilität führt. Das erlaubt es dem System zwischen verschiedenen Modi der Pulserzeugung zu wechseln. In (ii) wird die Pulserzeugung stark von der Wahl der Kopplungsstärken und der Anzahl der Verbindungen beeinflusst. Analytische Näherungen werden abgeleitet, die einen Zusammenhang zwischen der Anzahl der Verbindungen und der Pulsrate, sowie der Pulszugvariabilität herstellen. In (iii) wird festgestellt, dass eine hemmende Rückkopplung zu sehr unregelmäßigem Verhalten der isolierten Neuronen führt, wohingegen eine starke Kopplung mit dem Netzwerk ein regelmäßigeres Feuern von Salven hervorruft. / Neurons are excitable systems. Their responses to excitations above a certain threshold are spikes. Usually, spike generation is shaped by several feedback mechanisms that can act on slow time scales. These can lead to phenomena such as spike-frequency adaptation, reverse spike-frequency adaptation, or bursting. In addition to these, neurons are subject to several sources of noise and interact with other neurons, in the connected complexity of a neural network. Yet how does the interplay of feedback mechanisms, noise as well as interaction with other neurons affect spike generation? This thesis examines how spike generation in noise-driven excitable systems is influenced by slow feedback processes and coupling to other excitable systems. To this end, spike generation in three setups is considered: (i) in a single excitable system, which is complemented by a slow feedback mechanism, (ii) in a set of coupled excitable systems, and (iii) in a set of strongly-coupled bursting neurons. In each of these setups, the statistics of spiking is investigated by a combination of analytical methods and computer simulations. The main result of the first setup is that the interplay of strong positive (excitatory) feedback and noise leads to noise-controlled bistability. It enables excitable systems to switch between different modes of spike generation. In (ii), spike generation is strongly affected by the choice of the coupling strengths and the number of connections. Analytical approximations are derived that relate the number of connections to the firing rate and the spike train variability. In (iii), it is found that negative (inhibitory) feedback causes very irregular behavior of the isolated bursters, while strong coupling to the network regularizes the bursting.

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