Cette thèse étudie la problématique du fonctionnement sans capteur et à basse vitesse des moteurs synchrones à aimant permanent par l'injection des signaux. Nous nous focalisons sur les effets de la saturation magnétique car leur compensation est primordiale pour résoudre cette problématique. Nous proposons une méthode originale pour modéliser la saturation magnétique en utilisant une approche énergétique (les formulations Lagrangienne et Hamiltonienne), où les symétries physiques sont exploitées pour simplifier l'expression de l'énergie magnétique. Les données expérimentales montrent qu'un polynôme de degré 4 est suffisant pour décrire avec précision les effets de la saturation. Ensuite, nous proposons une analyse claire et originale basée sur la moyennisation de second ordre et qui explique comment obtenir l'information de position à partir de l'injection des signaux (en utilisant le modèle proposé). Nous donnons une relation explicite entre les oscillations des courants statoriques et la position du rotor; cette relation est utilisée en temps réel. Ce modèle de saturation magnétique ainsi que la procédure d'estimation de position ont été testés et validés sur deux types de moteurs : avec des aimants permanents à l'intérieur ou sur la surface du rotor. Les résultats expérimentaux obtenus sur un banc de test montrent que les erreurs d'estimation de la position du rotor n'excèdent pas quelques degrés électriques dans la zone d'opération à basse vitesse.

This thesis studies the negative impact that control signal saturation may have on a controlled system. Different methods that are used to compensate for this problem are also studied and evaluated. Both sensitivity to disturbances and the effect the method has on the systems'ability to follow a reference signal will be examined. Stability will be discussed, but no conclusions whether the systems are stabilized or not can be drawn. Control signal saturation will lead to a slower behavior in general. For controllers with integral action this performance degradation will cause an extended growth in the integrating part of the controller. This leads to large overshoots and possibly to instability. As an alternative to the more ad-hoc based methods, model based predictive control is studied. This metod can explicitly handle constrained control signals. Here, too, sensitivity to disturbances and the effect the method has on the systems'ability to follow a reference signal is examined.

Trafiksystemet i Linköpings tätort bygger på två ringar, Y-ringen (yttre) och C- ringen (centrum), vilkas syfte är att avlasta stadens olika centrala delar. Den signalreglerade korsningen Industrigatan-Östgötagatan är en del av den så kallade Y-ringen och under vissa tider på dygnet finns det risk för köbildning. Antalet inkommande fordon i korsningen uppgick år 1999 till ca 28 000 per dygn och idag uppgår antalet till någonstansmellan 30 400-32 400 fordon/dygn. Kommunen har planer på att på att etablera ett bostadsområde i Övre Vasastaden, vilket kan komma att påverka trafikmängderna i den studerade korsningen. En garanterad orsak till ökade trafikmängder är det faktum att Linköping ständigt ökar i invånarantal, med ökad folkmängd ökar även trafiken. Storleken på trafikökningen finns prognostiserad i olika trafikprognoser och dessa visar att när staden har 150 000 respektive 180 000 invånare kommer det inkommande flödet i aktuell korsning uppgå till ca 35 000 respektive ca 40 000 fordon/dygn. Framtida kö- och framkomlighetsproblem är därmed en realitet. Med stöd av effektberäkningsprogrammet Capcal presenteras tre olika förslag på åtgärder där framkomlighetsproblemen undviks. Alternativ 1 innebär modifiering av trafiksignalerna och en förbjuden vänstersväng, alternativ 2 är en rund cirkulationsplats och alternativ 3 motsvaras av en oval cirkulationsplats. I de två sistnämnda alternativen föreslås även fyra alternativa lösningar för gång- och cykeltrafik. En jämförelse mellan de olika alternativen visar att de ”bästa” effektmåtten erhålls vid alternativ 3 även om resultaten i alternativ 2 nästan är lika ”bra”. Däremot om kommunens prognoser skulle slå fel med 10 %, dvs om trafiken skulle öka med 10 % mer än beräknat, skulle endast alternativ 1 visa på godkända värden. Resonemanget kring rekommendationer av alternativ har delvis gjorts utifrån de framräknade effektmåtten men även med tanke på trafiksäkerheten för både de oskyddade trafikanterna och fordonstrafikanterna.

It is widely known in oil industry that changes in fluid flow conditions such as water breakthrough or unsteady flow due to well shut-in can lead to sand destabilization, with a possible consequent sand production. In this research, different flow situations are incorporated into stress and stability analysis for the region around a wellbore producing oil from weak or unconsolidated sands, and the analyses involve strength weakening, stress redistribution, and decrease of rock stiffness. Two main mechanisms, chemical reactions of rock with formation water and variations of rock capillary strength, are identified and analyzed to study strength weakening after water breakthrough, both qualitatively and quantitatively. Using theories from particle mechanics, rock mechanics, and interfacial science, four novel capillarity models are developed and verified to analytically capture the physical behaviors of capillary strength at the grain scale. Based on model calculations, significantly better understanding of strength behavior in two-phase fluid environments is achieved. Based on a simplified model that can conservatively but efficiently quantify capillary strength with only two input parameters (i. e. particle radius and water saturation), a verified new method that physically calculates pore pressure in a multiphase environment, and a coupled poro-inelastic stress model, the redistributions of effective stresses with water saturation around a wellbore are solved. In terms of stress changes and growth of a plastic radius defining shear-failure zone, the effects of different stability factors, including capillarity through water-oil menisci, pore pressure changes due to the variations of fluid relative permeabilities, and loss of strength through chemical reactions of water-sensitive cementation materials, are quantified and compared in order to clarify when and how they contribute to sand production after water breakthrough. The nonlinearities of rock elastic properties in stressed and biphasic fluid environments is analytically addressed, based on an improved nonlinear theory that considers both a failure-based mechanism and a confining-stress-based mechanism, the strength model, and the coupled stress model. The calculations demonstrate the redistributions of stress-dependent rock stiffness around a wellbore and its evolution with increase of water saturation, clarify the relative importance of each mechanism in reducing rock stiffness, and fundamentally explain why current predictive technologies are invalid when water appears in a flowing wellbore. To quantify the effect of well shut-down on rock stability, the redistributions of fluid pressure in reservoir are analytically solved and coupled with the stress model, while the water hammer equations provide a boundary condition for the bottom-hole pressure. This approach allows direct solution of the relationships among fluid properties, rock properties and production parameters, within the context of rock stability. The proposed new approaches and models can be applied to evaluate sand production risk in multiphase and unsteady fluid flow environment. They can also serve as points of departure to develop more sophisticated models, or to develop more useful constitutive laws for numerical solutions.

This thesis extends the use of neural-network-based model reference adaptive control to systems that occur as cascades. In general, these systems are not feedback linearizable. The approach taken is that of approximate feedback linearization of upper subsystems whilst treating the lower-subsystem states as virtual actuators. Similarly, lower-subsystems are also feedback linearized. Typically, approximate inverses are used for linearization purposes. Model error arising from the use of an approximate inverse is minimized using a neural-network as an adaptive element. Incorrect adaptation due to (virtual) actuator saturation and dynamics is avoided using the Pseudocontrol Hedging method. Using linear approximate inverses and linear reference models generally result in large desired pseudocontrol for large external commands. Even if the provided external command is feasible (null-controllable), there is no guarantee that the reference model trajectory is feasible. In order to mitigate this, nonlinear reference models based on nested-saturation methods are used to constrain the evolution of the reference model and thus the plant states. The method presented in this thesis lends itself to the inner-outer loop control of air vehicles, where the inner-loop controls attitude dynamics and the outer-loop controls the translational dynamics of the vehicle. The outer-loop treats the closed loop attitude dynamics as an actuator. Adaptation to uncertainty in the attitude, as well as the translational dynamics, is introduced, thus minimizing the effects of model error in all six degrees of freedom and leading to more accurate position tracking. A pole-placement approach is used to choose compensator gains for the tracking error dynamics. This alleviates timescale separation requirements, allowing the outer loop bandwidth to be closer to that of the inner loop, thus increasing position tracking performance. A poor model of the attitude dynamics and a basic kinematics model is shown to be sufficient for accurate position tracking. In particular, the inner-outer loop method was used to control an unmanned helicopter and has subsequently been applied to a ducted-fan, a fixed-wing aircraft that transitions in and out of hover, and a full-scale rotorcraft. Experimental flight test results are also provided for a subset of these vehicles.

Due to dramatic growth of capacity in optical fiber communication, the fiber dispersion has become one of major factors affecting the quality of optical signal transmission with different modulation scheme, leading to the importance in controlling optical chirp. Among the elements used for optical fiber communications, electroabsorption modulator (EAM) and semiconductor optical amplifier (SOA) are served as optical amplitude and phase modulation. In this work, EAM-integrated SOA is used to realize the pre-chirp technique through their inherently reversed phase modulation as well as amplitude modulation. In the experiment, tunable optical filter and a 10Gb/s data pattern are used for extracting the frequency chirp of the timely signal. With the positive chirp operation in EAM, it is found that the overall chirp of EAM-integrated SOA can be varied from 3GHz to -9GHz by adjusting current injection through SOA. Also, as inspecting the 10Gb/s pattern, the pattern effect can also be controlled by the reversed carrier dynamics between EAM and SOA. Finally, a 10Gb/s data transmission with 43km transmission is demonstrated by using such pre-chirp technique, showing that such technique can be applied to other type signal processing.

In 2005 the highest global surface temperature ever was recorded. A virtual consensus exists today among scientists that global warming is underway and that human greenhouse gas (GHG) emissions are a significant cause. Possible mitigation of climate change through reduction of net GHG emissions has become a worldwide concern. Under the United Nation’s Framework convention on Climate Change, the Kyoto Protocol was formed in 1997 and required ratifying countries to co-operate in stabilizing atmospheric GHG concentrations. The protocol took effect on February 16, 2005. The mitigation cost for reducing GHG emissions for the US economy has been argued to be high particularly through the energy sector. Agriculture and Forestry (AF) can provide some low cost strategies to help with this mitigation principally through carbon sequestration but must be competitive with mitigation costs in the rest of the economy. A general equilibrium approach is used herein to evaluate the role of AF mitigation in an economy wide setting. The results show that the AF sectors have significant mitigation potential. Higher carbon prices lead to more sequestration, less emissions, reduced consumer and total welfare, improved environmental indicators and increased producer welfare. AF mitigation increases as the carbon price increase over time. In the earlier periods, while the carbon price is low, AF emissions and sink are quite small compared to the energy sector. As carbon prices increase over time, the AF sectors mitigate about 25% of the net emissions. This verifies McCarl et al's (2001) argument that the AF sectors “may be very important in a world that requires time and technological investment to develop low-cost greenhouse gas emission offsets.” AF GHG emission mitigation is sensitive to saturation of sequestration sinks. This research finds that ignoring saturation characteristics leads to a severe overestimate of mitigation potential with estimates being inflated by as much as a factor of 6.

Simultaneous blood perfusion and oxygenation monitoring is crucial for patients undergoing a transplant procedure. This becomes of great importance during the surgical recovery period of a transplant procedure when uncorrected loss of perfusion or reduction in oxygen saturation can result in patient death. Pulse oximeters are standard monitoring devices which are used to obtain the perfusion level and oxygen saturation using the optical absorption properties of hemoglobin. However, in cases of varying perfusion due to hemorrhage, blood clot or acute blockage, the oxygenation results obtained from traditional pulse oximeters are erroneous due to a sudden drop in signal strength. The long term goal of the project is to devise an implantable optical sensor which is able to perform better than the traditional pulse oximeters with changing perfusion and function as a local warning for sudden blood perfusion and oxygenation loss. In this work, an optical sensor based on a pulse oximeter with an additional source at 810nm wavelength has been developed for in situ monitoring of transplant organs. An algorithm has been designed to separate perfusion and oxygenation signals from the composite signal obtained from the three source pulse oximetry-based sensor. The algorithm uses 810nm reference signals and an adaptive filtering routine to separate the two signals which occur at the same frequency. The algorithm is initially applied to model data and its effectiveness is further tested using in vitro and in vivo data sets to quantify its ability to separate the signals of interest. The entire process is done in real time in conjunction with the autocorrelation-based time domain technique. This time domain technique uses digital filtering and autocorrelation to extract peak height information and generate an amplitude measurement and has shown to perform better than the traditional fast Fourier transform (FFT) for semi-periodic signals, such as those derived from heart monitoring. In particular, in this paper it is shown that the two approaches produce comparable results for periodic in vitro perfusion signals. However, when used on semi periodic, simulated, perfusion signals and in vivo data generated from an optical perfusion sensor the autocorrelation approach clearly (Standard Error, SE = 0.03) outperforms the FFT-based analysis (Standard Error, SE = 0.62).

Du fait de sa robustesse et de son faible coût, la machine synchro-réluctante (MSR) constitue une alternative intéressante à la machine asynchrone. A pertes égales, une MSR bien optimisée offre un couple et par suite un rendement plus élevés. Ainsi, la MSR est très compétitive pour les applications à haute vitesse, à forte puissance ou à haute température. Cette thèse se propose d'optimiser les machines synchro-réluctantes à rotor massif et avec barrières de flux pour produire le maximum de couple avec un facteur de puissance le plus élevé possible. Pour cela, une modélisation originale utilisant des réseaux de perméances non linéaires a été mise au point pour les deux types de MSR. Les modèles proposés sont significativement plus rapides et aussi précis que les modèles par éléments finis. De plus, la réalisation d'un prototype à barrières de flux a permis de les valider expérimentalement.

We review the Regge theory and the minijet model for pp and pp collisions. We show that, in the conventional minijet approach, the asymptotic behavior of the total cross section calculated using currently accepted gluon distribution function and perturbative QCD rises too rapidly when compared with the data and fails to satisfy Froissart bound. To tame the rise, we have developed a new formalism for the interaction between QCD gluon and the classical color field of the colliding nucleons, and show how the gluon propagator is modified. The corresponding gauge invariance condition of the propagator is derived and shown to be satisfied. The modified gluon propagator leads to a suppression of the minijet cross section due to the gg [rightwards arrow] gg sub-process in the small-x region. We show that the pp and pp total cross section from [square root]s = 5 GeV to 30 TeV can be described as a sum of a hard component contributed by the classical field modified minijet model and a soft component due to the exchange of the Pomeron and the I=0 exchange-degenerate [omega] and f Regge trajectories. The soft-component model is motivated by the notion of duality. The predicted total cross section has a ln s asymptotic behavior. / text