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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.
211

Multiplicative robust and stochastic MPC with application to wind turbine control

Evans, Martin A. January 2014 (has links)
A robust model predictive control algorithm is presented that explicitly handles multiplicative, or parametric, uncertainty in linear discrete models over a finite horizon. The uncertainty in the predicted future states and inputs is bounded by polytopes. The computational cost of running the controller is reduced by calculating matrices offline that provide a means to construct outer approximations to robust constraints to be applied online. The robust algorithm is extended to problems of uncertain models with an allowed probability of violation of constraints. The probabilistic degrees of satisfaction are approximated by one-step ahead sampling, with a greedy solution to the resulting mixed integer problem. An algorithm is given to enlarge a robustly invariant terminal set to exploit the probabilistic constraints. Exponential basis functions are used to create a Robust MPC algorithm for which the predictions are defined over the infinite horizon. The control degrees of freedom are weights that define the bounds on the state and input uncertainty when multiplied by the basis functions. The controller handles multiplicative and additive uncertainty. Robust MPC is applied to the problem of wind turbine control. Rotor speed and tower oscillations are controlled by a low sample rate robust predictive controller. The prediction model has multiplicative and additive uncertainty due to the uncertainty in short-term future wind speeds and in model linearisation. Robust MPC is compared to nominal MPC by means of a high-fidelity numerical simulation of a wind turbine under the two controllers in a wide range of simulated wind conditions.
212

Control of a Multivariable Lighting System

Halldin, Axel January 2017 (has links)
This master’s thesis examines how a small MIMO lighting system can be identified and controlled. Two approaches are examined and compared; the first approach is a dynamic model using state space representation, where the system identification technique is Recursive Least Square, RLS, and the controller is an LQG controller; the second approach is a static model derived from the physical properties of light and a feedback feed-forward controller consisting of a PI controller coupled with a Control Allocation, CA, technique. For the studied system, the CA-PI approach significantly outperforms the LQG-RLS approach, which leads to the conclusion that the system’s static properties are predominant compared to the dynamic properties.
213

Evaluation of Model-Based Design Using Rapid Control Prototyping on Forklifts / Utvärdering av modelbaserad utveckling med Rapid Control Prototyping på gaffeltruckar

Jansson, Lovisa, Nilsson, Amanda January 2019 (has links)
The purpose of this thesis is to evaluate Rapid Control Prototyping which is apart of the Model-Based Design concept that makes it possible to convenientlytest prototype control algorithms directly on the real system. The evaluation ishere done by designing two different controllers, a gain-scheduled P controllerand a linear Model Predictive Controller (mpc), for the lowering of the forks of aforklift.The two controllers are first tested in a simulation environment. The thesis con-tains two different simulation models: one physical where only minor parameteradjustments are done and one estimated black-box model. After evaluating thecontrollers in a simulation environment they are tested on a real forklift with areal-time target machine.The designed controllers have different strengths and weaknesses as one is non-linear and single variable, the P controller, and the other linear and multivariable,thempc. The P controller has a smooth movement in all situations without be-ing slow, unlike thempc. The disadvantage of the P controller compared to thempcis that there is no guarantee that the P controller will keep the speed limit,whereas thempcapproach gives such a guarantee.The better performance of the P controller outweighs the speed limit guaranteeand thus a conclusion is drawn that the nonlinearities of the system has a largereffect than the multivariable aspect. Also, another conclusion drawn is that work-ing with Model-Based Design and Rapid Control Prototyping makes it possibleto test many different ideas on a real forklift without spending a lot of time onimplementation. / Syftet med detta examensarbete är att utvärdera Rapid Control Prototyping vil-ket är en del av modellbaserad utveckling som gör det möjligt att enkelt testamodeller av styralgoritmer direkt på det riktiga systemet. Utvärderingen är gjordgenom att testa två olika regulatorer, en P-regulator med parameterstyrning ochen linjär modelbaserad prediktionsregulator (mpc), för sänkningen av gafflarnapå en truck.De två regulatorerna testas först i en simuleringsmiljö. I arbetet används två olikasimuleringsmodeller: en fysikalisk där endast mindre parameterjusteringar görsoch en estimerad black-box modell. Efter att regulatorerna utvärderas i simule-ringsmiljön testas de även på en riktig truck med hjälp av automatisk kodgenere-ring och exekvering på en dedikerad hårdvaruplattform.De konstruerade regulatorerna har olika för- och nackdelar eftersom en är olinjäroch envariabel, P-regulatorn, och en är linjär men flervariabel,mpc:n. P-regulatornhar en mjuk rörelse i alla lägen utan att bli för långsam, till skillnad frånmpc:n.Nackdelen med P-regulatorn, jämfört medmpc:n är att det inte finns någon ga-ranti för att P-regulatorn håller hastighetsbegränsningen sommpc:n gör.P-regulatorns bättre prestanda överväger garantin om att hålla hastighetsbegräns-ningen och därför dras slutsatsen att olinjäriteterna i systemet överväger effekter-na av det faktum att det också är flervariabelt. En annan slutsats är att modell-baserad utveckling och Rapid Control Prototyping gör det möjligt att testa fleraolika idéer på en riktig gaffeltruck utan att spendera för mycket tid på implemen-tationen.
214

Direct Lift Control of Fighter Aircraft

Öhrn, Philip, Åstrand, Markus January 2019 (has links)
Direct lift control for aircraft has been around in the aeronautical industry for decades but is mainly used in commercial aircraft with dedicated direct lift control surfaces. The focus of this thesis is to investigate if direct lift control is feasible for a fighter aircraft, similar to Saab JAS 39 Gripen, without dedicated control surfaces. The modelled system is an aircraft that is inherently unstable and contains nonlinearities both in its aerodynamics and in the form of limited control surface deflection and deflection rates. The dynamics of the aircraft are linearised around a flight case representative of a landing scenario. Direct lift control is then applied to give a more immediate relation from pilot stick input to change in flight path angle while also preserving the pitch attitude. Two different control strategies, linear quadratic control and model predictive control, were chosen for the implementation. Since fighter aircraft are systems with fast dynamics it was important to limit the computational time. This constraint motivated the use of specialised methods to speed up the optimisation of the model predictive controller. Results from simulations in a nonlinear simulation environment supplied by Saab, as well as tests in high-fidelity flight simulation rigs with a pilot, proved that direct lift control is feasible for the investigated fighter aircraft. Sufficient control authority and performance when controlling the flight path angle were observed. Both developed controllers have their own advantages and which strategy is the most suitable depends on what the user prioritises. Pilot workload during landing as well as precision at touch down were deemed similar to conventional control.
215

Uso do espaço do marsupial Caluromys philander (Didelphimorphia, Didelphidae) no Parque Nacional da Serra dos Órgãos - Rio de Janeiro, Brasil / Space use by Woolly opossum Caluromys philander (Didelphimorphia; Didelphidae) in Serra dos Órgãos Nacional Park - Rio de Janeiro, Brasil

Bernardo Silveira Papi 21 February 2011 (has links)
Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / Uso do espaço é um padrão bem estudado em ecologia. Entretanto, formação de área de vida e posição relativa dos abrigos com área de uso são pouco estudados, principalmente para marsupiais didelfídeos. Dentre estes animais, podemos destacar Caluromys philander, devido ao seu baixo registro em armadilhas na Mata Atlântica e características peculiares dentro do grupo, como seu desenvolvimento, longevidade e hábito alimentar. Neste estudo foram investigadas as formações das áreas de uso destes animais através da comparação com seus movimentos diários, e a posição dos seus abrigos dentro das suas áreas de uso. Para isso foram monitorados seis indivíduos de C. philander através de colares rádio transmissores. Estes indivíduos se deslocaram em média 534 153 m por noite. Além disso, apresentaram área diária de 9548 3591 m e área de vida de 2,8 0,4 ha. Noventa e sete por cento das áreas diárias apresentaram sobreposição entre si, com média de 19,4% de sobreposição. Não houve diferença nos locais dos abrigos dos indivíduos monitorados, dentro dos seus Mínimos Polígonos Convexos. Entretanto, estes mesmos abrigos não estiveram localizados nas áreas de maior intensidade de uso. A média de abrigos utilizados por indivíduo foi de 6,3 (3-10) com utilização média de 2,9 (1-17) vezes em cada abrigo, sendo que 48% das vezes os animais só possuíram um registro em cada abrigo, demonstrando baixa fidelidade. Entretanto, dois indivíduos apresentaram diferença de utilização entre seus abrigos, com três destes sendo mais utilizados que os outros. O trabalho sugere que os indivíduos de C. philander monitorados apresentam área de vida propriamente dita (restrita), onde ocorrem as sobreposições entre suas áreas diárias. C. philander utilizam mais de um abrigo em suas vidas, trocando com frequência de abrigos, apesar de alguns destes abrigos poderem ser mais utilizados que outros. Além disso, os abrigos destes animais não são localizados nas suas áreas de maior intensidade de uso. / Use of space is a well studied topic in ecology. However, the structuring of the home range and shelters position, have not received enough attention, especially for didelphid marsupials. One of these, Caluromys philander, is an interesting species because of its low record in traps studies in the Atlantic Forest and its unique characteristics among marsupials related to development, longevity and feeding habits. The present study analyses how daily movements can contribute to the home range formation and how the shelters are positioned within the home range of these animals. Six individuals of C. philander were equipped with radio transmitters necklaces and followed during the night. These individuals moved 534 153 m in average per night. They also had daily ranges of 9548 3591 m and home ranges of 2.8 0.4 ha. There was a 97% overlap between days, with an average of 19.4%. There was no difference in shelters positions and Minimum Convex Polygon areas, although these same shelters were not located in the areas with the greatest use intensity. The average number of shelters used per individual was 6.3 (3-10), with an average of 2.9 (1-17) records per shelter, where shelters were used only one time in 47% of the cases, suggesting low shelter fidelity of these animals. However, two individuals showed difference of shelters use, with three of those being used more than the others. Therefore, I conclude that these individuals of C. philander have real home ranges, where they concentrate their daily movements. C. philander uses more than one shelter in its life, changing shelters frequently, although some shelters can be more used than others. Forthermore, shelters were not located in the areas with the greatest use intensity.
216

Gouvernance à la BCEAO et à la BEAC : expériences monétaires en zone franc africaine / Governance at the BCEAO and the BEAC : monetary experiments in African franc zone

Bokino, Régis 02 December 2014 (has links)
Si la littérature du biais inflationniste de la Nouvelle École Classique, au travers des concepts decrédibilité et de transparence, a conduit à l'indépendance des Banques centrales, sa critique par laNouvelle École Keynésienne l'a réduit à une indépendance instrumentale et a mis en exergue le rôlede sa gouvernance, de l'importance de sa relation avec la sphère politique pour la légitimité de sonaction, ainsi que le rôle essentiel des Conseils de politique monétaire (CPM).Aussi bien en théorie que dans les faits, ce cadre institutionnel qui reflète la gouvernance montre uneBanque centrale non pas séparée du politique mais plutôt en relation avec celui-ci. Dans la mesure oùles décisions de politique monétaire sont prises par un CPM, la gouvernance concerne également sonorganisation et les procédures d’élaboration de la décision.L’objectif de cette thèse est d’analyser à la lumière de ses développements récents, la gouvernance àla BCEAO et à la BEAC qui sont les Banques centrales couvrant les deux unions monétaires de lazone franc, à savoir l’UEMOA pour la première et la CEMAC pour la seconde. Cette thèse a aussipour objectif de montrer que la pérennisation de ces deux unions monétaires passe par une meilleuregouvernance et la nécessité d’un fédéralisme budgétaire en leur sein impliquant donc une plus forteunion politique. Toutefois, nous soulignons les obstacles rendant très difficile la réalisation de cetteultime étape de l’intégration. / If the literature of the inflationary bias of the New Classical School, through the concepts of credibilityand transparency, led to the independence of Central Banks, its review by the New Keynesian Schoolreduced it to an instrumental independence and has highlight the role of its governance, of theimportance of its relationship with politicians for the legitimacy of its action and the essential role of theCouncils of monetary policy.In theory and in practice, this institutional framework that reflects governance shows a Central Bank(MPC) not separated from politics but rather in connection therewith. Insofar the monetary policydecisions, the governance, and procedures for the preparation of the decision are taken by a CPM.The objective of this thesis is to analyze in the light of recent developments, governance at theBCEAO and the BEAC which are the central banks covering two monetary unions from franc zonenamely WAEMU and CAEMC. This thesis also aims to show that the sustainability of these twomonetary unions through the benefits might enjoy better governance and the need for fiscal federalismwithin them thus implying a stronger political union. However, we highlight the barriers embarrassingthis final stage of integration.
217

The mutant-prevention concentration concept and its application to <i>Staphylococcus aureus</i>

Metzler, Kelli Leigh 17 June 2004
<i>Staphylococcus aureus</i> is a ubiquitous organism causing world-wide morbidity and mortality. This species readily develops resistance to antimicrobial agents. Current dosing strategies are based, in part, on minimum inhibitory concentrations (MICs). This susceptibility test fails to detect the presence of first-step resistant mutants often present in large heterogeneous populations of infecting bacteria. Dosing strategies based on MIC results may, in fact, allow for the selective proliferation of resistant subpopulations. The mutant-prevention concentration (MPC) is the drug concentration at which all first-step resistant mutants will be eradicated along with the susceptible cells. Determination of the mutant-selection window (MSW) is possible using MIC and MPC data. When considered together with achievable drug concentrations in human bodily sites, the MSW helps determine which antimicrobials are likely to select for resistance. MIC and MPC testing on clinical isolates of methicillin-susceptible (MSSA) and -resistant (MRSA) S. aureus was performed. Characterization via the polymerase chain reaction, sequencing, and electron microscopy (EM) was done on selected organisms recovered from MPC studies (MPC-recovered). MIC and MPC testing was performed on organisms isolated sequentially from patients with recurring S. aureus infections. Pulsed field gel electrophoresis was performed on these sequential isolates. Based on the MIC and the MPC values, the most potent agents for systemic MSSA and MRSA infections are gemifloxacin and vancomycin, respectively. Re-testing MPC-recovered populations by the MIC showed increased MIC results compared to the parent populations. Macrolide-resistance genes were discovered in S. aureus MPC-recovered populations; in contrast, parental isolates lacked these resistance determinants. EM revealed an increase in cell wall thickness of a vancomycin MPC-recovered population compared to its parental population. Moxifloxacin and vancomycin had the lowest and narrowest MSWs for systemic MSSA and MRSA infections, respectively, compared to the other agents tested. Sequential isolates showed no change in MIC and MPC values. The data presented provides evidence for the application of the MPC test to S. aureus organisms. The MPC data is significant when determining appropriate dosing strategies aimed at preventing resistance.
218

Stratégies optimales multi-critères, prédictives, temps réel de gestion des flux d'énergie thermique et électrique dans un véhicule hybride

Debert, Maxime 09 November 2011 (has links) (PDF)
La gestion d'énergie d'un véhicule hybride consiste à développer une stratégie, qui détermine à chaque instant la répartition des flux d'énergie thermique et électrique, minimisant la consommation globale du véhicule. La modélisation de la consommation du véhicule hybride permet d'écrire cette problématique sous la forme d'un problème d'optimisation dynamique sous contraintes d'évolutions. Ce problème est résolu de façon optimale lorsque l'ensemble des conditions de roulage sont connues à priori. La commande optimale obtenue sert de référence pour évaluer la performance des stratégies embarquées dans le véhicule. En s'appuyant sur la théorie de l'optimisation optimale, deux stratégies ont été crées : l'une prédictive qui a été testée sur un simulateur numérique et une autre, reposant sur le principe du problème dual, qui a été embarqué avec succès sur deux véhicules hybrides conventionnels. Pour les hybrides rechargeables, leur capacité énergétique et la possibilité de se recharger sur le réseau électrique libère des contraintes dans la problématique d'optimisation énergétique. C'est pourquoi, une nouvelle stratégie spécifique a été développée dans l'objectif de profiter au maximum de l'énergie électrique embarquée pour minimiser les émissions du véhicule. Pour l'ensemble des véhicules hybrides, la batterie est un composant clef dont le vieillissement vient modifier sa rentabilité économique et énergétique. C'est pourquoi un observateur a été conçu pour fournir une information précise de la température interne des cellules. Cette information est utilisée par une stratégie spécifique optimisant la consommation tout en préservant la batterie des températures extrêmes, nuisibles à sa longévité.
219

The mutant-prevention concentration concept and its application to <i>Staphylococcus aureus</i>

Metzler, Kelli Leigh 17 June 2004 (has links)
<i>Staphylococcus aureus</i> is a ubiquitous organism causing world-wide morbidity and mortality. This species readily develops resistance to antimicrobial agents. Current dosing strategies are based, in part, on minimum inhibitory concentrations (MICs). This susceptibility test fails to detect the presence of first-step resistant mutants often present in large heterogeneous populations of infecting bacteria. Dosing strategies based on MIC results may, in fact, allow for the selective proliferation of resistant subpopulations. The mutant-prevention concentration (MPC) is the drug concentration at which all first-step resistant mutants will be eradicated along with the susceptible cells. Determination of the mutant-selection window (MSW) is possible using MIC and MPC data. When considered together with achievable drug concentrations in human bodily sites, the MSW helps determine which antimicrobials are likely to select for resistance. MIC and MPC testing on clinical isolates of methicillin-susceptible (MSSA) and -resistant (MRSA) S. aureus was performed. Characterization via the polymerase chain reaction, sequencing, and electron microscopy (EM) was done on selected organisms recovered from MPC studies (MPC-recovered). MIC and MPC testing was performed on organisms isolated sequentially from patients with recurring S. aureus infections. Pulsed field gel electrophoresis was performed on these sequential isolates. Based on the MIC and the MPC values, the most potent agents for systemic MSSA and MRSA infections are gemifloxacin and vancomycin, respectively. Re-testing MPC-recovered populations by the MIC showed increased MIC results compared to the parent populations. Macrolide-resistance genes were discovered in S. aureus MPC-recovered populations; in contrast, parental isolates lacked these resistance determinants. EM revealed an increase in cell wall thickness of a vancomycin MPC-recovered population compared to its parental population. Moxifloxacin and vancomycin had the lowest and narrowest MSWs for systemic MSSA and MRSA infections, respectively, compared to the other agents tested. Sequential isolates showed no change in MIC and MPC values. The data presented provides evidence for the application of the MPC test to S. aureus organisms. The MPC data is significant when determining appropriate dosing strategies aimed at preventing resistance.
220

Model predictive control of a magnetically suspended flywheel energy storage system / Christiaan Daniël Aucamp

Aucamp, Christiaan Daniël January 2012 (has links)
The goal of this dissertation is to evaluate the effectiveness of model predictive control (MPC) for a magnetically suspended flywheel energy storage uninterruptible power supply (FlyUPS). The reason this research topic was selected was to determine if an advanced control technique such as MPC could perform better than a classical control approach such as decentralised Proportional-plus-Differential (PD) control. Based on a literature study of the FlyUPS system and the MPC strategies available, two MPC strategies were used to design two possible MPC controllers were designed for the FlyUPS, namely a classical MPC algorithm that incorporates optimisation techniques and the MPC algorithm used in the MATLAB® MPC toolbox™. In order to take the restrictions of the system into consideration, the model used to derive the controllers was reduced to an order of ten according to the Hankel singular value decomposition of the model. Simulation results indicated that the first controller based on a classical MPC algorithm and optimisation techniques was not verified as a viable control strategy to be implemented on the physical FlyUPS system due to difficulties obtaining the desired response. The second controller derived using the MATLAB® MPC toolbox™ was verified to be a viable control strategy for the FlyUPS by delivering good performance in simulation. The verified MPC controller was then implemented on the FlyUPS. This implementation was then analysed in order to validate that the controller operates as expected through a comparison of the simulation and implementation results. Further analysis was then done by comparing the performance of MPC with decentralised PD control in order to determine the advantages and limitations of using MPC on the FlyUPS. The advantages indicated by the evaluation include the simplicity of the design of the controller that follows directly from the specifications of the system and the dynamics of the system, and the good performance of the controller within the parameters of the controller design. The limitations identified during this evaluation include the high computational load that requires a relatively long execution time, and the inability of the MPC controller to adapt to unmodelled system dynamics. Based on this evaluation MPC can be seen as a viable control strategy for the FlyUPS, however more research is needed to optimise the MPC approach to yield significant advantages over other control techniques such as decentralised PD control. / Thesis (MIng (Computer and Electronic Engineering))--North-West University, Potchefstroom Campus, 2013

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