Dissertations / Theses on the topic 'Controlled fusion'
To see the other types of publications on this topic, follow the link: Controlled fusion.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Controlled fusion.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Khudur, Alan. "Modification of wall materials in controlled fusion devices." Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-199336.
Full text
2
Eliasson, Oskar, and Pawel Kupsc. "Modification of wall materials in controlled fusion devices." Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-199364.
Full text
3
Jackson, Danika Rae. "A study of poloidal asymmetries in tokamaks." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/21531.
Full text
4
Huang, Billy Kiat. "Development of FPGA controlled diagnostics on the MAST fusion reactor." Thesis, Durham University, 2013. http://etheses.dur.ac.uk/9415/.
Full textAbstract:
Field Programmable Gate Array technology (FPGA) is very useful for implementing high performance digital signal processing algorithms, data acquisition and real-time control on nuclear fusion devices. This thesis presents the work done using FPGAs to develop powerful diagnostics. This has been achieved by developing embedded Linux and running it on the FPGA to enhance diagnostic capabilities such as remote management, PLC communications over the ModBus protocol and UDP based ethernet streaming. A closed loop real-time feedback prototype has been developed for combining laser beams onto a single beam path, for improving overall repetition rates of Thomson Scattering systems used for plasma electron temperature and density radial profile measurements. A controllable frequency sweep generator is used to drive the Toroidal Alfven Eigenmode (TAE) antenna system and results are presented indicating successful TAE resonance detection. A fast data acquisition system has been developed for the Electron Bernstein Wave (EBW) Synthetic Aperture Microwave Imaging system and an active probing microwave source where the FPGA clock rate has been pushed to the maximum. Propagation delays on the order of 2 nanoseconds in the FPGA have been finely tuned with careful placement of FPGA logic using a custom logic placement tool. Intensity interferometry results are presented on the EBW system with a suggestion for phase insensitive pitch angle measurement.
5
Harley, David. "Nuclear and molecular processes in muon-catalyzed fusion." Diss., The University of Arizona, 1991. http://hdl.handle.net/10150/185443.
Full textAbstract:
The dt-αn continuum in the presence of the muon is studied in detail, and it is shown that the existence of extended continuum states just beneath the d+(tμ)₁(s) threshold can lead to a variety of 'pseudoresonant' fusion processes with a temperature and density dependence distinct from those leading to molecular formation. Various in-flight and pseudoresonant fusion reaction cross sections involving the excitation of electromolecular states and two or three scattering bodies are computed. Fusion processes in very dense plasmas of ∼10³ liquid hydrogen density are studied, and it is shown that in this environment both sticking and muon transfer problems are eliminated, and that pseudoresonant fusion processes should dominate. In this context, the use of negatively charged hadrons as potential catalytic particles is also considered.
6
Evans, Peter John. "Laser plasma interaction for application to fusion energy /." View thesis, 2002. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030724.133202/index.html.
Full text
7
Montoya-Pelaez, Pedro Jose. "Design and synthesis of hemithioindigo lipids for photo-controlled membrane fusion." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ37355.pdf.
Full text
8
Meyer, Ryan. "Multiple potential well structure in inertial electrostatic confinement devices." Diss., Columbia, Mo. : University of Missouri-Columbia, 2004. http://hdl.handle.net/10355/4098.
Full textAbstract:
Thesis (M.S.) University of Missouri-Columbia, 2004.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (June 30, 2006) Vita. Includes bibliographical references.
9
Evans, Peter J., University of Western Sydney, of Science Technology and Environment College, and of Science Food and Horticulture School. "Laser plasma interaction for application to fusion energy." THESIS_CSTE_SFH_Evans_P.xml, 2002. http://handle.uws.edu.au:8081/1959.7/293.
Full textAbstract:
This thesis presents an investigation into inertial confinement fusion through mathematical models and computer simulations. Salient features affecting fusion are identified, in both energy absorption and fusion gains. Mathematical tools are applied to a directed investigation into plasma structure. Parameters such as these involved in electromagnetic energy absorption are identified first, and the next step is to model the immediate response of the plasma to this energy input, with a view to how this may be advantageous to initiating fusion. Models are developed that best suit plasma behaviour. The parameters are presented graphically against time and distance into a small plasma fuel pellet. It is noted how field density and ions form undulations through the plasma. Types of plasma fuels are discussed with regards to their key parameters. Computations are performed using the laser driven inertial energy option based on volume ignition with the natural adiabatic self-similarity compression and expansion hydrodynamics. The relative merits of each fuel are discussed against the parameters of density, volume and energy input versus fusion gains.Master of Science (Hons)
10
McCollam, Karsten James. "Investigation of magnetic relaxation in coaxial helicity injection /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/9741.
Full text
11
Sayer, Min-hee Shin. "Evolution of radial force balance and radial transport over L-H transition." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45911.
Full textAbstract:
Understanding of plasma confinement modes is an essential component in development of a fusion reactor. Plasma confinement directly relates to performance of a fusion reactor in terms of energy replacement time requirements on other design parameters. Although a variety of levels of confinement have been achieved under different operating conditions in tokamaks, tokamak confinement is generally identified as being either Low (L-mode--poor confinement) or High (H-mode--good confinement)
In operation of a tokamak experiment, the plasma confinement condition generally changes from L-mode to H-mode over a few hundred milliseconds, sometimes quite sharply. Such a difference in transition period seems to be largely due to operating conditions of the plasma. Comparison of experimental data exhibits various distinctions between confinement modes. One noteworthy distinction between confinement modes is development of steep density and temperature gradients of electrons and ions in the plasma edge region of High confinement, H-modes, relative to Low-confinement, L-modes.
The fundamental reason for the change for L-mode to H-mode is not understood. Previous studies have suggested i) the development of reduced diffusive transport coefficients that require a steepening of the gradients in a localized region in the edge plasma, the "transport barrier" in H-mode confinement ii) the radial force balance between pressure gradient forces and electromagnetic (radial electric field and VxB) forces require radial particle fluxes to satisfy a pinch-diffusion relation. A recent study suggests that the major difference between L-mode and H-mode are associated with the electromagnetic forces in the "pinch velocity" and the pressure gradient, not in the diffusion coefficients that multiplies the pressure gradient.
The research will examine in detail the time evolution of the radial force balance and the particle and energy transport during the L-H transition. For the analysis, DIII-D shot #118897 is selected for transition between L- and H-mode confinements. Plasma conditions in L-mode, near the L-H transition and following the transition are selected for analysis of various parameter profiles.
The initial analysis will be based on the four principal equations for plasma: particle balance, momentum balance, force balance and heat conduction. Based on these equations, specific equations have been derived: toroidal and radial momentum balances, diffusion coefficient, pinch velocity and heat conduction relation for calculation of parameters. The analysis of these equations, using the measured data, will establish how various terms in the radial force balance (radial electric field, VXB (electromagnetic) force, and pressure gradient) and the diffusive transport coefficients evolve over the confinement mode transition.
12
Shellabarger, Brian Tebelman. "Experimental studies of high-speed liquid films on flat and curved downward-facing surfaces for IFE applications." Thesis, Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04082004-180413/unrestricted/shellabarger%5fbrian%5ft%5f200312%5fms.pdf.
Full text
13
Nallagatla, Vishnu Priya. "Sequential decision fusion of multibiometrics applied to text-dependent speaker verification for controlled errors." Thesis, Queensland University of Technology, 2012. https://eprints.qut.edu.au/63348/1/Vishnu_Nallagatla_Thesis.pdf.
Full textAbstract:
Reliability of the performance of biometric identity verification systems remains a significant challenge. Individual biometric samples of the same person (identity class) are not identical at each presentation and performance degradation arises from intra-class variability and inter-class similarity. These limitations lead to false accepts and false rejects that are dependent. It is therefore difficult to reduce the rate of one type of error without increasing the other. The focus of this dissertation is to investigate a method based on classifier fusion techniques to better control the trade-off between the verification errors using text-dependent speaker verification as the test platform.
A sequential classifier fusion architecture that integrates multi-instance and multisample fusion schemes is proposed. This fusion method enables a controlled trade-off between false alarms and false rejects. For statistically independent classifier decisions, analytical expressions for each type of verification error are derived using base classifier performances. As this assumption may not be always valid, these expressions are modified to incorporate the correlation between statistically dependent decisions from clients and impostors. The architecture is empirically evaluated by applying the proposed architecture for text dependent speaker verification using the Hidden Markov Model based digit dependent speaker models in each stage with multiple attempts for each digit utterance. The trade-off between the verification errors is controlled using the parameters, number of decision stages (instances) and the number of attempts at each decision stage (samples), fine-tuned on evaluation/tune set. The statistical validation of the derived expressions for error estimates is evaluated on test data.
The performance of the sequential method is further demonstrated to depend on the order of the combination of digits (instances) and the nature of repetitive attempts (samples). The false rejection and false acceptance rates for proposed fusion are estimated using the base classifier performances, the variance in correlation between classifier decisions and the sequence of classifiers with favourable dependence selected using the 'Sequential Error Ratio' criteria. The error rates are better estimated by incorporating user-dependent (such as speaker-dependent thresholds and speaker-specific digit combinations) and class-dependent (such as clientimpostor dependent favourable combinations and class-error based threshold estimation) information.
The proposed architecture is desirable in most of the speaker verification applications such as remote authentication, telephone and internet shopping applications. The tuning of parameters - the number of instances and samples - serve both the security and user convenience requirements of speaker-specific verification. The architecture investigated here is applicable to verification using other biometric modalities such as handwriting, fingerprints and key strokes.
14
Floyd, John-Patrick II. "A numerical investigation of extending diffusion theory codes to solve the generalized diffusion equation in the edge pedestal." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39607.
Full textAbstract:
The presence of a large pinch velocity in the edge pedestal of high confinement
(H-mode) tokamak plasmas implies that particle transport in the plasma edge must be
treated by a pinch-diffusion theory, rather than a pure diffusion theory. Momentum
balance also requires the inclusion of a pinch term in descriptions of edge particle
transport. A numerical investigation of solving generalized pinch-diffusion theory using
methods extended from the numerical solution methodology of pure diffusion theory has
been carried out. The generalized diffusion equation has been numerically integrated
using the central finite-difference approximation for the diffusion term and three finite
difference approximations of the pinch term, and then solved using Gauss reduction. The
pinch-diffusion relation for the radial particle flux was solved directly and used as a
benchmark for the finite-difference algorithm solutions to the generalized diffusion
equation. Both equations are solved using several mesh spacings, and it is found that a
finer mesh spacing will be required in the edge pedestal, where the inward pinch velocity
is large in H-mode plasmas, than is necessary for similar accuracy further inward where
the pinch velocity diminishes. An expression for the numerical error of various finite-differencing
algorithms is presented.
15
Amrolia, Zarathustra J. "Linear and nonlinear fluid instabilities in tokamaks." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670336.
Full text
16
PARLETTE, EDWARD BRUCE. "GENERALIZED FUNCTION SOLUTIONS TO THE FOKKER-PLANCK EQUATION." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/187933.
Full textAbstract:
In problems involving highly forward-peaked scattering, the Boltzmann transport equation can be simplified using the Fokker-Planck model. The purpose of this project was to develop an analytical solution to the resulting Fokker-Planck equation. This analytical solution can then be used to benchmark numerical transport codes. A numerical solution to the Fokker-Planck equation was also developed. The analytical solution found is a generalized function. It satisfies the purpose of the project with two limitations. The first limitation is that the solution can only be evaluated for certain sources. The second limitation is that the solution can only be evaluated for small times. The moments of the Fokker-Planck equation can be evaluated for any time. The numerical solution developed works for all sources and all times. The analytical solution, then, provides an accurate and precise benchmark under certain conditions. The numerical solution provides a less accurate benchmark under all conditions.
17
Morast, Embla, and Einar Svantesson. "Efficiency of a Time-of-Flight Detection System for Analysis of Wall Material From Controlled Fusion Devices." Thesis, KTH, Skolan för teknikvetenskap (SCI), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-214736.
Full textAbstract:
Time-of-flight elastic recoil detection analysis (ToFERDA)is a method for material analysis which has provenadvantageous when examining wall samples from fusion devicesas well as for tracking tracer isotopes such as deuterium, oxygen-18 and nitrogen-15. When ToF-ERDA data is processed tocalculate the composition of a material, the detection efficiencyis used to compensate for the lower detection rate of lighterelements. The aim of this project is to examine how the efficiencyof the time-of-flight detector in a ToF-ERDA experimental setupdepends on its settings and determine efficiency parameters touse when producing atomic composition depth profiles with ToFERDA.Experiments were performed at the Tandem Laboratoryin Uppsala. The outcome is a suggested set of changes toexperimental settings and a four-parameter fit to measureddetection efficiencies for efficiency compensation.
18
MILANESIO, DANIELE. "Development and Validation of a software for the Analysis of Antennas for Controlled Magnetically Confined Nuclear Fusion." Doctoral thesis, Politecnico di Torino, 2008. http://hdl.handle.net/11583/2498895.
Full textAbstract:
Ion-Cyclotron Resonance Heating (ICRH) and Lower-Hybrid (LH)Resonance Heating are key parts of all present-day experiment toward the realization of controlled nuclear fusion with magnetic confinement.
Both auxiliary heating systems are essentially antennas made up of complex plasma facing components, charged with the difficult mission of delivering extremely high RF powers to the plasma with typically poor loadings (as compared to antennas in radar or broadcasting), and high near-field reactive energies that generate serious mismatches to the feeding power lines. Because of the impossibility of testing these antennas in plasmas outside the actual experiments for which they have to be designed, availability of accurate simulation tools is a key factor in assisting their design: this work is concerned with the numerical analysis of these plasma facing antennas, through the upgrade of an existing code called TOPICA and its recent extension named TOPLHA.
The antenna simulation code must be able to handle the actual geometry of both antennas (including their housing in the experiment, the protective screens, etc.), which have witnessed a constant increase in complexity. On the other hand, plasma loading on the antenna is extremely sensitive to the plasma profile, especially near the antenna itself: the antenna code must
therefore be able to correctly account for the plasma conditions,
which makes it necessary to include non-cold plasma terms (that
affect resonances).
More specifically, since the frequency range of the two heating
systems is quite different (below 100 MHz for ICRH and around few GHz for LH), the two antennas differ not only in the geometrical features (ICRH antennas are essentially metal loops while LH antennas are open-ended waveguide arrays), but also in the way the wave propagates in the plasma and the heating process happens.
The problem can be solved with a considerable numerical efficiency by formally separating it into two parts: the vacuum region around the antenna conductors and the plasma region. This approach leads to the problem formulation via a set of two coupled integral equations, further discretized via the Method of Moments (MoM). The MoM is used in a hybrid form: spatial-domain approach is employed for the antenna and other conductors (with high geometrical complexity), while a spectral-domain approach is used for the plasma region (as plasma description is naturally available in this domain).
Numerical tests have already been performed for simple ICRH launchers, and results compared with available experimental data both in vacuum and with real plasmas.
Eventually, this work has extended the existing capabilities of TOPICA in two directions: the efficient handling of IC antennas housed in near, but distinct recesses and the LH range. Both problems are multi-cavity, in the sense that the antennas are recessed in a modular way. Starting from the validated version of
TOPICA, a new approach has been developed to allow the code handle a much greater number of unknowns (from 10,000 to more than 150,000). In the IC range, this is dictated primarily by
geometrical complexity, while the overall electrical length of one
recess does not exceed one half free-space wavelength; in the LH
range, conversely, geometry is smoother, but electrical size is
larger.
The multi-cavity approach addressed in this work exploits the fact
that the inner parts of the individual cavities are coupled one to
each other only through the equivalent currents on their apertures, and accordingly solves the global MoM linear system
block-wise, with significant memory and time saving. Furthermore,
this modular approach led to a heavy parallelization of the code,
with an astonishing increase in the overall performances.
19
PISANO, FABIO. "Analysis and synthesis techniques of nonlinear dynamical systems with applications to diagnostic of controlled thermonuclear fusion reactors." Doctoral thesis, Università degli Studi di Cagliari, 2013. http://hdl.handle.net/11584/266202.
Full textAbstract:
Nonlinear dynamical systems are of wide interest to engineers, physicists and mathematicians, and this is due to the fact that most of physical systems in nature are inherently non-linear. The nonlinearity of these systems has consequences on their time-evolution, which in some cases can be completely unpredictable, apparently random, although fundamentally deterministic. Chaotic systems are striking examples of this.
In most cases, there are no hard and fast rules to analyse these systems. Often, their solutions cannot be obtained in closed form, and it is necessary to resort to numerical integration techniques, which, in case of high sensitivity to initial conditions, lead to ill-conditioning problems and high computational costs.
The dynamical system theory, the branch of mathematics used to describe the behaviour of these systems, focuses not on finding exact solutions to the equations describing the dynamical system, but rather on knowing if the system stabilises to a steady state in the long term, and what are the possible attractors, e.g. a quasi-periodic or chaotic attractors.
Regarding the synthesis, from both a practical and a theoretical standpoint, it is very desirable to develop methods of synthesizing these systems. Although extensive theory has been developed for linear systems, no complete formulation for nonlinear systems synthesis is present today.
The main topic of this thesis is the solution of engineering problems related to the analysis and synthesis of nonlinear and chaotic systems.
In particular, a new algorithm which optimizes Lyapunov exponents estimation in piecewise linear systems has been applied to PWL and polynomial chaotic systems. In the field of complex systems synthesis, a systematic method to project systems of order 2n characterized by two positive Lyapunov exponents, has been proposed. This procedure couples nth-order chaotic systems with a suitable nonlinear coupling function. Furthermore, a method for the fault detection has been developed. In the field of time series analysis, a new denoising method, based on the wavelet transform of the noisy signal, has been described. The method implements a variable thresholding, whose optimal value is determined by analysing the cross-correlation between the denoised signal and the residuals and by applying different criteria depending on the particular decomposition level. Finally, a study of dynamical behaviour of Type I ELMs has been performed for a future modelization of the phenomenon. In this context, a statistical analysis of time intervals between successive Type I ELMs has been proposed.---------------------------------- Il tema principale di questa tesi è la soluzione di problemi ingegneristici legati all’analisi e alla sintesi di sistemi dinamici non lineari. I sistemi dinamici non lineari sono di largo interesse per ingegneri, fisici e matematici, e questo è dovuto al fatto che la maggior parte dei sistemi fisici in natura è intrinsecamente non lineare.
La non linearità di questi sistemi ha conseguenze sulla loro evoluzione temporale, che in certi casi può rivelarsi del tutto imprevedibile, apparentemente casuale, seppure fondamentalmente deterministica. I sistemi caotici sono un esempio lampante di questo comportamento. Nella maggior parte dei casi non esistono delle regole standard per l’analisi di questi sistemi. Spesso, le soluzioni non possono essere ottenute in forma chiusa, ed è necessario ricorrere a tecniche di integrazione numerica, che, in caso di elevata sensibilità alle condizioni iniziali, portano a problemi di mal condizionamento e di elevato costo computazionale.
La teoria dei sistemi dinamici, la branca della matematica usata per descrivere il comportamento di questi sistemi, non si concentra sulla ricerca di soluzioni esatte per le equazioni che descrivono il sistema dinamico, ma piuttosto sull’analisi del comportamento a lungo termine del sistema, per sapere se questo si stabilizzi in uno stato stabile e per sapere quali siano i possibili attrattori, ad esempio, attrattori quasi-periodici o caotici.
Per quanto riguarda la sintesi, sia da un punto di vista pratico che teorico, è molto importante lo sviluppo di metodi in grado di sintetizzare questi sistemi. Sebbene per i sistemi lineari sia stata sviluppata una teoria ampia e esaustiva, al momento non esiste alcuna formulazione completa per la sintesi di sistemi non lineari.
In questa tesi saranno affrontati problemi di caratterizzazione, analisi e sintesi, legati allo studio di sistemi non lineari e caotici.
La caratterizzazione dinamica di un sistema non lineare permette di individuarne il comportamento qualitativo a lungo termine. Gli esponenti di Lyapunov sono degli strumenti che permettono di determinare il comportamento asintotico di un sistema dinamico. Essi danno informazioni circa il tasso di divergenza di traiettorie vicine, caratteristica chiave delle dinamiche caotiche. Le tecniche esistenti per il calcolo degli esponenti di Lyapunov sono computazionalmente costose, e questo fatto ha in qualche modo precluso l’uso estensivo di questi strumenti in problemi di grandi dimensioni. Inoltre, durante il calcolo degli esponenti sorgono dei problemi di tipo numerico, per ciò il calcolo deve essere affrontato con cautela. L’implementazione di algoritmi veloci e accurati per il calcolo degli esponenti di Lyapunov è un problema di interesse attuale.
In molti casi pratici il vettore di stato del sistema non è disponibile, e una serie temporale rappresenta l’unica informazione a disposizione. L’analisi di serie storiche è un metodo di analisi dei dati provenienti da serie temporali che ha lo scopo di estrarre delle statistiche significative e altre caratteristiche dei dati, e di ottenere una comprensione della struttura e dei fattori fondamentali che hanno prodotto i dati osservati. Per esempio, un problema dei reattori a fusione termonucleare controllata è l’analisi di serie storiche della radiazione Dα, caratteristica del fenomeno chiamato Edge Localized Modes (ELMs). La comprensione e il
16
controllo degli ELMs sono problemi cruciali per il funzionamento di ITER, in cui il type-I ELMy H-mode è stato scelto come scenario di funzionamento standard. Determinare se la dinamica degli ELM sia caotica o casuale è cruciale per la corretta descrizione dell’ELM cycle. La caratterizzazione dinamica effettuata sulle serie temporali ricorrendo al cosiddetto spazio di embedding, può essere utilizzata per distinguere serie random da serie caotiche.
Uno dei problemi più frequenti che si incontra nell’analisi di serie storiche sperimentali è la presenza di rumore, che in alcuni casi può raggiungere anche il 10% o il 20% del segnale. È quindi essenziale , prima di ogni analisi, sviluppare una tecnica appropriata e robusta per il denosing.
Quando il modello del sistema è noto, l’analisi di serie storiche può essere applicata al rilevamento di guasti. Questo problema può essere formalizzato come un problema di identificazione dei parametri. In questi casi, la teorie dell’algebra differenziale fornisce utili informazioni circa la natura dei rapporti fra l’osservabile scalare, le variabili di stato e gli altri parametri del sistema.
La sintesi di sistemi caotici è un problema fondamentale e interessante. Questi sistemi non implicano soltanto un metodo di realizzazione di modelli matematici esistenti ma anche di importanti sistemi fisici reali. La maggior parte dei metodi presentati in letteratura dimostra numericamente la presenza di dinamiche caotiche, per mezzo del calcolo degli esponenti di Lyapunov. In particolare, le dinamiche ipercaotiche sono identificate dalla presenza di due esponenti di Lyapunov positivi.
20
Benea, Claudia-Roxana. "Morphing Structures : An exploration of the fusion between marbled coating and triaxial weave." Thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-15746.
Full textAbstract:
The purpose of this study is to investigate the effects of a marbled coating applied on a triaxial woven structure. Although both of these techniques are traditionally used for many years, they are nowadays utilized in innovative ways, the marbling being applied on a large variety of surfaces such as wooden floors or ceramics and the triaxial weave being used as a hi-tech material for sports or in the automotive industry and having applications in diverse fields, from art to architecture. Their fusion, however, is a topic that has yet to be thoroughly explored, which makes for the motive of this thesis work, as an opening has been observed for the exploration of the expressive power of their combination. The experimental approach that has been taken towards this exploration will determine how the marbling effect may contribute to the visual expression of the structure. Multiple cycles of experiments have been conducted in an attempt to understand the behaviour of the chosen materials and their combination, the effect that various colour combinations have and the best possible pairings between the elements. The organic marbling combined with the geometric triaxial weave proved to generate the most powerful visual expression and the clearest result out of all the experiments. Thus five experimental textiles were developed in order to illustrate different aspects of this complex relationship, where the marbling would affect the visual expression of the structure by either enhancing or concealing the structural aspect and the contrast between the graphic element and the organic one would be a constant presence throughout the work. This work pushes the boundaries of conventional textile design and through the application of a textile thinking to unconventional materials a different type of expression is born. By mixing a limited amount of variables in multiple ways, a large range of visual effects may be achieved.
21
Cantin, Oriane. "PEO hot melt extrudates for controlled drug delivery." Thesis, Lille 2, 2016. http://www.theses.fr/2016LIL2S035/document.
Full textAbstract:
Parmi les procédés de fabrication continue, l’extrusion par fusion à chaud est une technique dont l’intérêt dans le domaine pharmaceutique est grandissant. Ce procédé permet la formation des dispersions solides des substances actives au sein des matrices polymériques ou lipidiques. En fonction de l’excipient et de la substance active, cela peut être largement utilisé pour la conception des systèmes: (i) pour une libération immédiate, (ii) pour une libération modifiée et (iii) pour le masquage de goût. Les systèmes à libération modifiée sont des dispositifs intéressants qui permettent d’améliorer la biodisponibilité de la substance active, son efficacité ainsi que l’observance des patients. En fonction de la nature de l’excipient, différents systèmes avec des mécanismes de libération variés peuvent être produit, notamment des matrices inerte, érodable ou gonflante. Le poly éthylène oxide est un polymère semi- cristallin et hydrophile qui peut être utilisé pour la libération contrôlée. Son point de fusion compris entre 63 et 67 °C le rend adapté pour l’extrusion. Surtout, ses capacités de gonflement permettent d’administrer la substance active de façon contrôlée en fonction du poids moléculaire du poly éthylène oxide. Les objectifs de ce travail sont (i) d’étudier l’impact des paramètres critiques du procédé (température d’extrusion et vitesse des vis d’extrudeuse) sur le profil de libération de la substance active, (ii) de déterminer l’impact des paramètres de formulations (poids moléculaire du poly éthylène oxide, charge et type de la substance active) sur le profil de libération de la substance active et (iii) d’évaluer des formes galéniques solides conçues par le procédé d’extrusion à celui de la compression directe. Il a été montré que la variation de la température d’extrusion et de la vitesse des vis altérait l’apparence de l’extrudat et ainsi la distribution de la substance active au sein de l’extrudat. Il s’est avéré dans notre étude que la libération de la substance active n’était pas particulièrement affectée par ces changements de température et vitesse de vis de l’extrudeuse. De plus, cette étude a permis de fixer les paramètres pour les projets suivants: température 100 °C ; vitesse des vis 30 rpm ; longueur de la forme galénique 1 cm. Des extrudats de poly ethylène oxide contenant 10 % de théophylline et du poly éthylène oxide de 100 à 7000 kDa ont été utilisés dans ce travail. Il a été observé que lorsque le poids moléculaire du poly ethylène oxide augmente de 100 à 600 kDa, la libération en substance active diminue de façon importante alors qu’une augmentation jusqu’à 7000 kDa ne diminue que légèrement la libération. Des études du gonflement ont montré que ce phénomène corrélait aux variations de volume de la partie opaque de l’extrudat (gel non transparent et cœur solide)Among continuous manufacturing processes, hot melt extrusion is a technique with growing interest in the pharmaceutical field. This process enables the formation of solid dispersions of many drugs within a polymeric or lipidic carrier. Hot melt extrusion can be widely used for different issues using the appropriate carrier and drug. Here are the mostly used concepts in pharmaceutical solid dosage forms: (i) immediate release, (ii) modified release and (iii) taste masking. Modified release systems have been taken into account to be very interesting devices for the improvement of drug- bioavailability, drug- efficacy as well as the patient compliance. Various systems with different release mechanisms can be manufactured, depending on the nature of the carrier (inert, erodible, and swelling matrices). Poly ethylene oxide is a semi crystalline and hydrophilic polymer which can be used to control drug delivery. The poly ethylene oxide melting point ranging from 63 to 67 °C makes it suitable for hot melt extrusion. Importantly, the swelling capacities of the hydrophilic poly ethylene oxide matrices are able to deliver drug in a time controlled manner, in respect of the poly ethylene oxide molecular weights. The purposes of this work were (i) to study the impact of critical process parameters (extrusion temperature and screw speed) on the drug release behavior, (ii) to determine the impact of formulation parameters (poly ethylene oxide molecular weight, nature of drug and drug loading) on drug release kinetics, and (iii) to evaluate solid dosage forms prepared by hot melt extrusion versus direct compression. Interestingly, the variation of the extrusion temperature and the screw speed leads to the altering of the extrudate appearance and thus the distribution of drug into the extrudate. However, this changing has not influenced the drug release remarkably. Thus, this study was useful to set the parameters for the following projects (temperature 100 °C; screw speed 30 rpm; dosage form size 1 cm). Poly ethylene oxide hot melt extrudates containing 10 % theophylline and based on 100 - 7,000 kDa poly ethylene oxide are used for this thesis. Importantly, the drug release decreased substantially with the increase of the poly ethylene oxide molecular weight from 100 to 600 kDa. However, further increasing of the molecular weights leads to only a slight decrease in the release rate. Swelling studies have shown that this phenomenon correlated with the change in volume of the opaque part of the extrudates (non-transparent gel and solid core)
22
Greenwood, James. "Development and evaluation of a complex rehabilitation programme for use following lumbar fusion surgery : a feasibility randomised controlled study with mixed methodology." Thesis, St George's, University of London, 2018. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.754061.
Full textAbstract:
One year after lumbar fusion surgery as many as 40% of patients are unsure or dissatisfied with their outcome. Despite this the use of lumbar fusion surgery is increasing, most notably in those over 60 years of age. Post-operative rehabilitation may improve clinical outcome, but the optimum rehabilitation strategy is currently unclear. Exploratory proof of concept work, evaluating a provisional rehabilitation programme, provided evidence of engagement and possible clinical impact. A systematic review with meta-analysis demonstrated complex rehabilitation, combining exercise with psychologically mediated strategies, may enhance post-operative outcome. The Medical Research Council promotes the inclusion of theory in the development complex healthcare interventions. Accordingly, a theoretical framework, based on the behavioural change wheel methodology and Social Cognitive Theory, was developed to inform the content and delivery of the REhabilitation following lumbar Fusion Surgery (REFS) programme. A randomised controlled feasibility study, with 3, 6, and 12-month follow-up, compared REFS with ‘usual care’. Between-group analyses showed statistically significant short-term improvements in disability and pain self-efficacy favouring REFS. Smaller, but potentially relevant, improvements were observed for physical function and quality of life. Longer-term results suggested a meaningful clinical impact for REFS participants. A ‘nested’ qualitative study explored participant’s rehabilitation experiences. This identified potential mechanisms of action, such as ‘sharing the rehabilitation experience’, and highlighted the complexity and inter-dependence of programme content. Emergent themes, including the association between kinesiophobia and concerns regarding the structural integrity of the surgical instrumentation, were identified. In conclusion, the studies reported in this thesis demonstrated that the theoretically informed REFS programme was feasible for delivery within the UK NHS, was associated with potential clinical impact, and with further refinement may provide a useful rehabilitation programme after lumbar fusion surgery. Overall, the researchers original contribution to knowledge relates to the inception, development, and evaluation of the REFS programme.
23
Cadell, Philip. "BabelFuse data fusion unit with precision wireless clock synchronisation." Thesis, Queensland University of Technology, 2012. https://eprints.qut.edu.au/55225/1/Philip_Cadell_Thesis.pdf.
Full textAbstract:
A significant issue encountered when fusing data received from multiple sensors is the accuracy of the timestamp associated with each piece of data. This is particularly important in applications such as Simultaneous Localisation and Mapping (SLAM) where vehicle velocity forms an important part of the mapping algorithms; on fastmoving vehicles, even millisecond inconsistencies in data timestamping can produce errors which need to be compensated for. The timestamping problem is compounded in a robot swarm environment due to the use of non-deterministic readily-available hardware (such as 802.11-based wireless) and inaccurate clock synchronisation protocols (such as Network Time Protocol (NTP)). As a result, the synchronisation of the clocks between robots can be out by tens-to-hundreds of milliseconds making correlation of data difficult and preventing the possibility of the units performing synchronised actions such as triggering cameras or intricate swarm manoeuvres.
In this thesis, a complete data fusion unit is designed, implemented and tested. The unit, named BabelFuse, is able to accept sensor data from a number of low-speed communication buses (such as RS232, RS485 and CAN Bus) and also timestamp events that occur on General Purpose Input/Output (GPIO) pins referencing a submillisecondaccurate wirelessly-distributed "global" clock signal. In addition to its timestamping capabilities, it can also be used to trigger an attached camera at a predefined start time and frame rate. This functionality enables the creation of a wirelessly-synchronised distributed image acquisition system over a large geographic area; a real world application for this functionality is the creation of a platform to facilitate wirelessly-distributed 3D stereoscopic vision.
A ‘best-practice’ design methodology is adopted within the project to ensure the final system operates according to its requirements. Initially, requirements are generated from which a high-level architecture is distilled. This architecture is then converted into a hardware specification and low-level design, which is then manufactured. The manufactured hardware is then verified to ensure it operates as designed and firmware and Linux Operating System (OS) drivers are written to provide the features and connectivity required of the system. Finally, integration testing is performed to ensure the unit functions as per its requirements.
The BabelFuse System comprises of a single Grand Master unit which is responsible for maintaining the absolute value of the "global" clock. Slave nodes then determine their local clock o.set from that of the Grand Master via synchronisation events which occur multiple times per-second. The mechanism used for synchronising the clocks between the boards wirelessly makes use of specific hardware and a firmware protocol based on elements of the IEEE-1588 Precision Time Protocol (PTP). With the key requirement of the system being submillisecond-accurate clock synchronisation (as a basis for timestamping and camera triggering), automated testing is carried out to monitor the o.sets between each Slave and the Grand Master over time. A common strobe pulse is also sent to each unit for timestamping; the correlation between the timestamps of the di.erent units is used to validate the clock o.set results.
Analysis of the automated test results show that the BabelFuse units are almost threemagnitudes more accurate than their requirement; clocks of the Slave and Grand Master units do not di.er by more than three microseconds over a running time of six hours and the mean clock o.set of Slaves to the Grand Master is less-than one microsecond.
The common strobe pulse used to verify the clock o.set data yields a positive result with a maximum variation between units of less-than two microseconds and a mean value of less-than one microsecond.
The camera triggering functionality is verified by connecting the trigger pulse output of each board to a four-channel digital oscilloscope and setting each unit to output a 100Hz periodic pulse with a common start time. The resulting waveform shows a maximum variation between the rising-edges of the pulses of approximately 39¥ìs, well below its target of 1ms.
24
Andersen, Nicholas J. "Microsphere Spray System for Wound Coverage." UKnowledge, 2014. http://uknowledge.uky.edu/cbme_etds/23.
Full textAbstract:
Spinal fusion is used to treat diseases or disorders of the spine by fusing together two or more vertebrae. Two associated risks with spinal fusion are infection and blood loss. Administration of tranexamic acid is used to prevent blood loss, and transfusions are given following blood loss. Surgical site infections are prevented with vancomycin powder spread into the surgical wound, while established infections are treated by debridement and delivery of antibiotics for 4 to 6 weeks. The present research explored an alternate method to prevent and treat blood loss or infection in spinal fusion. Poly(lactic-co-glycolic acid) (PLGA) microspheres was used to encapsulate vancomycin for 42 days to treat infection. Vancomycin encapsulated in gelatin microspheres had a controlled release of 7 days to prevent infection. Tranexamic acid was dissolved into phosphate-buffered saline or carboxymethylcellulose to provide a release of 6 hours to prevent blood loss after surgery. The microspheres and tranexamic acid were delivered to a target region using a water based spray system. The spray system demonstrated the delivery and distribution of drugs to a target region. The microsphere spray system is capable of spraying drugs onto a target region to prevent or treat blood loss and infection over time.
25
Annovazzi, Alicia. "Contribution à l'étude - interaction laser-matière à différentes pressions résiduelles : Application au procédé micro-fusion laser sur lit de poudre." Thesis, Bourgogne Franche-Comté, 2020. http://www.theses.fr/2020UBFCA024.
Full textAbstract:
Le procédé de micro-fusion sur lit de poudre par faisceau laser (LBM) et par faisceau d’électrons (EBM) sont deux procédés de fabrication additive permettant la réalisation de pièces métalliques. L’intense densité d’énergie fournie par ces deux sources permet la fusion locale de la matière formant ainsi un bain liquide, qui se solidifie après refroidissement. Ce changement d’état, qui se déroule sur des temps très courts, induit de complexes phénomènes thermodynamiques. Chacun de ces procédés offre des avantages qu’il serait intéressant de combiner. De ce fait, une combinaison des deux technologies a été investiguée. Le procédé EBM nécessitant un vide poussé dans l’enceinte de travail, l’enjeu de cette thèse repose donc sur l’étude de la fusion laser à faible pression environnante. Outre la combinaison recherchée, la fusion laser sous vide peut s’avérer intéressante dans l’amélioration de la santé matière des pièces, en particulier pour des matériaux sensibles à l’oxygène. Cependant, une nette diminution du rendement du procédé est observée. Ce travail de thèse s’articule en deux parties : a) En premier lieu, une étude expérimentale de la fabricabilité d’échantillons à différentes pressions a été réalisée. Pourdes paramètres de fabrication identiques, il en ressort qu’une diminution significative de la densification des échantillons est obtenue lors de la fabrication à faibles pressions. Les paramètres densité d’énergie volumique et vitesse de déplacement du laser ont dû être alors adaptés en fonction de la pression environnante utilisée. b) La seconde partie a été consacrée à l’explication des mouvements du bain liquide qui ont évolué en fonction de la pression résiduelle. A cet effet, une caméra rapide a permis de montrer les importantes instabilités présentes dans le lit de poudre par la zone de dénudation, et le bain liquide par sa morphologie, pour certains paramètres laser. Ces phénomènes ont été d’autant plus observés pour des pressions résiduelles inférieures à 30 mbar. Enfin, le pré-frittage du lit de poudredans le but d’effectuer un recuit "in-situ" des matériaux étudiés, a montré un effet bénéfique lors de l’interaction laser-matière sous vide. Une amélioration de la qualité de fusion et une augmentation du rendement de fabrication ont été alors démontréesThe laser beam melting (LBM) and electron beam melting (EBM) processes are two additive manufacturing technologies allowing the production of metallic parts. The intense energy density provided by the power supply is sufficient in order to melt the material creating a molten pool, and will solidify after cooling. This change of phase which takes place in a very short time, induced complexthermodynamics phenomena. Each of the processes offer advantages that could be interesting to be combined. Hence, a combination of the two technologies has been investigated. The EBM process requiring a rough vacuum in the work chamber, the issue of this work is based on the study of the laser melting at low pressure. Besides the intended combination, the selective laser melting under vacuum pressure can be attractive with the aim of improving the material integrity, in particular on the oxygen-sensitive materials. However, a clear decrease of the process efficiency has been observed. This work includes two parts: a) Firstly, an experimental study of samples fabricability at different pressures conditions is observed. For the same manufacturing parameters, a significant decrease of samples densification is observed in rough vacuum. The parameters volumetric energy density and the laser displacement speed have to beadapted in function of the chamber pressure. b) The second part is an attempt to explain the molten pool motion which change depending on the pressure. This can be achieved with a fast cam allowing the observations of strong instabilities in the powder bed with the denudation zone, and the molten pool with the morphology, for specific laser parameters. These phenomena are more important for residual pressures under 30 mbar. Then, a powder bed pre-sintering for the purpose of ”in-situ” annealing of the materials studied, has shown the beneficial effect during the interaction laser-powder under vacuum. Improvement melt quality and increased manufacturing efficiency have beenachieved
26
Bedin, Antonio. "A duloxetina como analgésico reduz o consumo de opioides após cirurgia de coluna, estudo duplo encoberto, aleatório e controlado." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/5/5152/tde-04012018-093145/.
Full textAbstract:
Introdução: a analgesia multimodal é amplamente usada para o controle da dor perioperatória em um esforço para reduzir o uso de opioides. A duloxetina é um inibidor seletivo da recaptação da serotonina e noradrenalina com eficácia para estados de dor crônica. O objetivo principal deste estudo foi avaliar a eficácia de duas doses orais de 60 mg de duloxetina em termos de consumo de fentanil durante o período pós-operatório em pacientes submetidos à cirurgia eletiva de artrodese de coluna lombar. Método: este estudo foi um ensaio clínico prospectivo, duplo encoberto, aleatório e controlado com placebo. Os pacientes receberam 60 mg de duloxetina ou placebo idêntico uma hora antes da cirurgia e 24 horas depois. Os sujeitos do estudo foram divididos em dois grupos: grupo C (controle) de indivíduos que receberam o placebo; e grupo D (duloxetina) de indivíduos que receberam 60 mg de duloxetina. O consumo total de fentanil administrado pelo próprio paciente em 24 e 48 horas após a cirurgia foi mensurado. Os desfechos secundários foram os escores de dor e a presença ou ausência de efeitos adversos, tais como cefaleia, náuseas, vômitos, prurido, tonturas e sonolência. Resultados: as características demográficas não diferiram entre os grupos. Houve uma diferença significativa no consumo de fentanil nas primeiras 24 horas entre os grupos C e D (diferença média, 223,11 ± 39,32 ?g; p < 0,001). O consumo de fentanil também diferiu entre os grupos C e D após 48 horas (diferença média, 179,35 ± 32,55 ug; p < 0,00). Os escores de dor em mais de 48 horas não diferiram significativamente entre os grupos. A incidência de efeitos colaterais foi semelhante nos dois grupos. Conclusão: a duloxetina foi associada à redução do consumo de fentanil no pós-operatório de cirurgias sobre a coluna lombar, portanto, sendo eficaz como adjuvante para a analgesia pós-operatória e redução do consumo de opioidesBackground: Multimodal analgesia is widely advocated for the control of perioperative pain in an effort to reduce the use of opioids. Duloxetine is a selective serotonin and noradrenaline reuptake inhibitor with efficacy for chronic pain states. The main objective of this study was to evaluate the efficacy of two oral doses of 60 mg duloxetine in terms of fentanyl submitted to elective lumbar spine arthrodesis surgery. Method: This study was prospective, double blind, randomized, and placebo controlled clinical trial. Patients received duloxetine 60 mg or identical placebo one hour before surgery and 24 hours later. The study subjects were divided into two groups: group C (control) of subjects who received placebo; and group D (duloxetine) from subjects received 60 mg. The total fentanyl consumption by the patient himself at 24 and 48 hours after surgery was measured. Secondary outcomes were pain scores and the presence or absence of adverse effects such as headache, nausea, vomiting, pruritus, dizziness and drowsiness. Results: Demographic characteristics did not differ between groups. There was a significant difference in fentanyl consumption in the first 24 hours between groups C and D (mean difference, 223.11 ± 39.32 ?g; p < 0.001). Fentanyl consumption also differed between groups C and D after 48 hours (mean difference, 179.35 ± 32.55 ?g; p < 0.00). Pain scores in more than 48 hours did not differ significantly between groups. The incidence of side effects was similar in both groups. Conclusion: Duloxetine was associated with reduction of fentanyl consumption in the postoperative period of surgeries on the lumbar spine, therefore, it was effective as adjuvant for postoperative analgesia and reduction of opioid consumption
27
Claasen, Göntje Caroline. "Capteur de mouvement intelligent pour la chirurgie prothétique naviguée." Phd thesis, Ecole Nationale Supérieure des Mines de Paris, 2012. http://pastel.archives-ouvertes.fr/pastel-00691192.
Full textAbstract:
Nous présentons un système de tracking optique-inertiel qui consiste en deux caméras stationnaires et une Sensor Unit avec des marqueurs optiques et une centrale inertielle. La Sensor Unit est fixée sur l'objet suivi et sa position et orientation sont déterminées par un algorithme de fusion de données. Le système de tracking est destiné à asservir un outil à main dans un système de chirurgie naviguée ou assistée par ordinateur. L'algorithme de fusion de données intègre les données des différents capteurs, c'est-à-dire les données optiques des caméras et les données inertielles des accéléromètres et gyroscopes. Nous présentons différents algorithmes qui rendent possible un tracking à grande bande passante avec au moins 200Hz avec des temps de latence bas grâce à une approche directe et des filtres dits invariants qui prennent en compte les symmétries du système. Grâce à ces propriétés, le système de tracking satisfait les conditions pour l'application désirée. Le système a été implementé et testé avec succès avec un dispositif expérimental.
28
Anderson, Taurug. "Iterative Learning Control model for a Resistive Wall Mode Active Controller." Thesis, KTH, Fusionsplasmafysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-125897.
Full textAbstract:
The EXTRAP T2R is a Reversed Field Pinch (RFP) device purposed to conduct magnetic confinement fusion research. Magnetic confinement works on the principle of isolating the hot plasma from the cool walls by locking in the plasma onto the magnetic field lines. Due to the generally unstable nature of plasma, the plasma column will shift off its centered position and encroach upon the cooling walls. To counteract this, a series of magnetic sensor coil are placed around the torus that serve as the input for another set of coils that will generate a magnetic field to force the plasma column back in place. This is a feedback mechanism that uses a Proportional-Integral-Derivative (PID) as the loop gain control mechanisms. While this was effective in stabilizing the system it was discovered that during the start up phase of the experiment there was a repeatable pattern of disturbance. As such it offers the opportunity to make use of a feedforward Iterative Learning Control (ILC) that could provide a much more precise stabilization and occlude the possibility of saturating the feedback coils. In this thesis an ILC system will be built upon the existing PID system, it will be modeled in MATLAB and SIMULINK then run to simulate and gauge its performance.
29
Russell, Jared S. "An optimization approach to plant-controller co-design /." Online version of thesis, 2009. http://hdl.handle.net/1850/10769.
Full text
30
Gautier, Stéphane. "Fusion de donnees gammagraphiques et ultrasonores. Aplication au controle non destructif." Paris 11, 1996. http://www.theses.fr/1996PA112521.
Full textAbstract:
Nous nous interessons au developpement d'une methode de fusion pour obtenir une image tridimensionnelle d'un objet a partir de gammagraphies et d'echographies. Ces deux jeux de donnees apportent des informations complementaires sur l'objet. Ils sont relies de facon independante a deux jeux de parametres : l'attenuation pour les gammagraphies et la reflectivite pour les echographies. Dans le cadre bayesien retenu, il apparait que le cur du processus de fusion reside dans l'introduction d'un modele a priori joint pour l'attenuation et la reflectivite. Dans un premier temps, nous etudions les modeles a priori separes pour l'attenuation et la reflectivite et montrons que dans les deux cas la modelisation d'evenements rares souleve des difficultes analogues ; compte tenu du faible contenu informationnel des donnees traitees, nous retenons des fonctions regularisantes convexes. Concernant la fusion, l'apparition d'une grande reflectivite est a priori reliee a une rupture dans l'attenuation, ce qui nous amene a chernche a correler la reflectivite et la derivee de l'attenuation. En nous inspirant des modeles separes, nous construisons alors des modeles joints markoviens et retenons finalement un potentiel convexe. Les resultats de traitement montrent l'amelioration obtenue, par rapport au cas ou seules des gammagraphies sont utilisees. Par ailleurs, la methode s'avere robuste vis-a-vis de problemes de recalage des donnees. Enfin, nous proposons d'ameliorer le modele d'observation convolutif pour les echographies d'une part, en estimant conjointement le noyau et la reflectivite et d'autre part, en introduisant une double reflectivite qui permet de modeliser des rotations de phase du noyau. Le travail presente concerne une application en controle non destructif mais pourrait etre adapte a d'autres problemes, notamment en imagerie biomedicale.
31
Séjean, Joseph. "Implementation of a biologically relevant gaze controller using sensory fusion and shared motor drives." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80141.
Full textAbstract:
The goal of this thesis is the analysis, implementation and testing of a binocular active vision system. The robotic head has six degrees of freedom: two independently actuated eyes can perform yaw and pitch movements. They are both mounted on a head also capable of yaw and pitch. The system uses both visual inputs, from two CCD cameras, and inertial input, from an angular velocity sensor, to track targets and hold gaze. This work is centered on the robotic head's binocular gaze controller: a simple method to modify the controller's parameters to reach specified dynamics is provided. The gaze controller, based on biological gaze control, can accommodate a wide range of movements: smooth pursuit, version, vergence, saccades, vestibulo-ocular reflex, gaze holding, and gaze control with an added head. Unlike other controllers that independently model each movement, the bilateral controller fuses sensory error signals to drive a single controller; the output drives to the different motors are also shared. All that is required is a simple switching strategy for transitions from slow phase to fast phase. Results illustrate the similarity between simulation and experimentation: this allows easy modification to the controller.
32
Mechhoud, Sarah. "Estimation de la diffusion thermique et du terme source du modèle de transport de la chaleur dans les plasmas de tokamaks." Phd thesis, Université de Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-00954183.
Full textAbstract:
Cette thèse porte sur l'estimation simultanée du coefficient de diffusion et du terme source régissant le modèle de transport de la température dans les plasmas chauds. Ce phénomène physique est décrit par une équation différentielle partielle (EDP) linéaire, parabolique du second-ordre et non-homogène, où le coefficient de diffusion est distribué et le coefficient de réaction est constant. Ce travail peut se présenter en deux parties. Dans la première, le problème d'estimation est traité en dimension finie ("Early lumping approach"). Dans la deuxième partie, le problème d'estimation est traité dans le cadre initial de la dimension infinie ("Late lumping approach"). Pour l'estimation en dimension finie, une fois le modèle établi, la formulation de Galerkin et la méthode d'approximation par projection sont choisies pour convertir l'EDP de transport en un système d'état linéaire, temps-variant et à entrées inconnues. Sur le modèle réduit, deux techniques dédiées à l'estimation des entrées inconnues sont choisies pour résoudre le problème. En dimension infinie, l'estimation en-ligne adaptative est adoptée pour apporter des éléments de réponse aux contraintes et limitations dues à la réduction du modèle. Des résultats de simulations sur des données réelles et simulées sont présentées dans ce mémoire.
33
Axelsson, Patrik. "Sensor Fusion and Control Applied to Industrial Manipulators." Doctoral thesis, Linköpings universitet, Reglerteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-105343.
Full textAbstract:
One of the main tasks for an industrial robot is to move the end-effector in a predefined path with a specified velocity and acceleration. Different applications have different requirements of the performance. For some applications it is essential that the tracking error is extremely small, whereas other applications require a time optimal tracking. Independent of the application, the controller is a crucial part of the robot system. The most common controller configuration uses only measurements of the motor angular positions and velocities, instead of the position and velocity of the end-effector. The development of new cost optimised robots has introduced unwanted flexibilities in the joints and the links. The consequence is that it is no longer possible to get the desired performance and robustness by only measuring the motor angular positions. This thesis investigates if it is possible to estimate the end-effector position using Bayesian estimation methods for state estimation, here represented by the extended Kalman filter and the particle filter. The arm-side information is provided by an accelerometer mounted at the end-effector. The measurements consist of the motor angular positions and the acceleration of the end-effector. In a simulation study on a realistic flexible industrial robot, the angular position performance is shown to be close to the fundamental Cramér-Rao lower bound. The methods are also verified in experiments on an ABB IRB4600 robot, where the dynamic performance of the position for the end-effector is significantly improved. There is no significant difference in performance between the different methods. Instead, execution time, model complexities and implementation issues have to be considered when choosing the method. The estimation performance depends strongly on the tuning of the filters and the accuracy of the models that are used. Therefore, a method for estimating the process noise covariance matrix is proposed. Moreover, sampling methods are analysed and a low-complexity analytical solution for the continuous-time update in the Kalman filter, that does not involve oversampling, is proposed. The thesis also investigates two types of control problems. First, the norm-optimal iterative learning control (ILC) algorithm for linear systems is extended to an estimation-based norm-optimal ILC algorithm where the controlled variables are not directly available as measurements. The algorithm can also be applied to non-linear systems. The objective function in the optimisation problem is modified to incorporate not only the mean value of the estimated variable, but also information about the uncertainty of the estimate. Second, H∞ controllers are designed and analysed on a linear four-mass flexible joint model. It is shown that the control performance can be increased, without adding new measurements, compared to previous controllers. Measuring the end-effector acceleration increases the control performance even more. A non-linear model has to be used to describe the behaviour of a real flexible joint. An H∞-synthesis method for control of a flexible joint, with non-linear spring characteristic, is therefore proposed.En av de viktigaste uppgifterna för en industrirobot är att förflytta verktyget i en fördefinierad bana med en specificerad hastighet och acceleration. Exempel på användningsområden för en industrirobot är bland annat bågsvetsning eller limning. För dessa typer av applikationer är det viktigt att banföljningsfelet är extremt litet, men även hastighetsprofilen måste följas så att det till exempel inte appliceras för mycket eller för lite lim. Andra användningsområden kan vara punktsvetsning av bilkarosser och paketering av olika varor. För dess applikationer är banföljningen inte det viktiga, istället kan till exempel en tidsoptimal banföljning krävas eller att svängningarna vid en inbromsning minimeras. Oberoende av applikationen är regulatorn en avgörande del av robotsystemet. Den vanligaste regulatorkonfigurationen använder bara mätningar av motorernas vinkelpositioner och -hastigheter, istället för positionen och hastigheten för verktyget, som är det man egentligen vill styra. En del av utvecklingsarbetet för nya generationers robotar är att reducera kostnaden men samtidigt förbättra prestandan. Ett sätt att minska kostnaden kan till exempel vara att minska dimensionerna på länkarna eller köpa in billigare växellådor. Den här utvecklingen av kostnadsoptimerade robotar har infört oönskade flexibiliteter i leder och länkar. Det är därför inte längre möjligt att få den önskade prestandan och robustheten genom att bara mäta motorernas vinkelpositioner och -hastigheter. Istället krävs det omfattande matematiska modeller som beskriver dessa oönskade flexibiliteter. Dessa modeller kräver mycket arbete att dels ta fram men även för att identifiera parametrarna. Det finns automatiska metoder för att beräkna modellparametrarna men oftast krävs det en manuell justering för att få bra prestanda. Den här avhandlingen undersöker möjligheterna att beräkna verktygspositionen med hjälp av bayesianska metoder för tillståndsskattning. De bayesianska skattningsmetoderna beräknar tillstånden för ett system iterativt. Med hjälp av en matematisk modell över systemet predikteras vad tillståndet ska vara vid nästa tidpunkt. Efter att mätningar av systemet vid den nya tidpunkten har genomförts justeras skattningen med hjälp av dessa mätningar. De metoder som har använts i avhandlingen är det så kallade extended Kalman filtret samt partikelfiltret. Informationen på armsidan av växellådan ges av en accelerometer som är monterad på verktyget. Med hjälp av accelerationen för verktyget och motorernas vinkelpositioner kan en skattning av verktygspositionen beräknas. I en simuleringsstudie för en realistisk vek robot har det visats att skattningsprestandan ligger nära den teoretiska undre gränsen, känd som Raooch mätstörningar som påverkar roboten. För att underlätta trimningen så har en metod för att skatta processbrusets kovariansmatris föreslagits. En annan viktig del som påverkar prestandan är modellerna som används i filtren. Modellerna för en industrirobot är vanligtvis framtagna i kontinuerlig tid medan filtren använder modeller i diskret tid. För att minska felen som uppkommer då de tidskontinuerliga modellerna överförs till diskret tid har olika samplingsmetoder studerats. Vanligtvis används enkla metoder för att diskretisera vilket innebär problem med prestanda och stabilitet. För att hantera dessa problem införs översampling vilket innebär att tidsuppdateringen sker med en mycket kortare sampeltid än vad mätuppdateringen gör. För att undvika översampling kan det motsvarande tidskontinuerliga filtret användas för att prediktera tillstånden vid nästa diskreta tidpunkt. En analytisk lösning med låg beräkningskomplexitet till detta problem har föreslagits. Vidare innehåller avhandlingen två typer av reglerproblem relaterade till industrirobotar. För det första har den så kallade norm-optimala iterative learning control styrlagen utökats till att hantera fallet då en skattning av den önskade reglerstorheten används istället för en mätning. Med hjälp av skattningen av systemets tillståndsvektor kan metoden nu även användas till olinjära system vilket inte är fallet med standardformuleringen. Den föreslagna metoden utökar målfunktionen i optimeringsproblemet till att innehålla inte bara väntevärdet av den skattade reglerstorheten utan även skattningsfelets kovariansmatris. Det innebär att om skattningsfelet är stort vid en viss tidpunkt ska den skattade reglerstorheten vid den tidpunkten inte påverka resultatet mycket eftersom det finns en stor osäkerhet i var den sanna reglerstorheten befinner sig. För det andra har design och analys av H∞-regulatorer för en linjär modell av en vek robotled, som beskrivs med fyra massor, genomförts. Det visar sig att reglerprestandan kan förbättras, utan att lägga till fler mätningar än motorns vinkelposition, jämfört med tidigare utvärderade regulatorer. Genom att mäta verktygets acceleration kan prestandan förbättras ännu mer. Modellen över leden är i själva verket olinjär. För att hantera detta har en H∞-syntesmetod föreslagits som kan hantera olinjäriteten i modellen.
Vinnova Excellence Center LINK-SIC
34
Fil, Nicolas. "Caractérisation et modélisation des propriétés d’émission électronique sous champ magnétique pour des systèmes RF hautes puissances sujets à l’effet multipactor." Thesis, Toulouse, ISAE, 2017. http://www.theses.fr/2017ESAE0025/document.
Full textAbstract:
La fusion nucléaire contrôlée par confinement magnétique avec les réacteurs de type Tokamaks et les applications spatiales ont en commun d’utiliser des composants Haute-Fréquence (HF) sous vide à forte puissance. Ces composants peuvent être sujets à l’effet multipactor qui augmente la densité électronique dans le vide au sein des systèmes, ce qui est susceptible d’induire une dégradation des performances des équipements et de détériorer les composants du système. Ces recherches consistent à améliorer la compréhension et la prédiction de ces phénomènes. Dans un premier temps nous avons réalisé une étude de sensibilité de l’effet multipactor au rendement d’émission électronique totale (noté TEEY). Cette étude a permis de montrer que l’effet multipactor est sensible à des variations d’énergies autour de la première énergie critique et dans la gamme d’énergies entre la première énergie critique et l’énergie du maximum. De plus, les composants HF utilisés dans les réacteurs Tokamak et dans le domaine du spatial peuvent être soumis à un champ magnétique continu. Nous avons donc développé un nouveau dispositif expérimental afin d’étudier ce phénomène. Le fonctionnement du dispositif et la méthode de mesure ont été analysées et optimisées à l’aide de modélisations numériques avec le logiciel PIC SPIS. Une fois que l’utilisation du dispositif a été optimisée et que le protocole de mesures a été validé, nous avons étudié l’influence d’un champ magnétique uniforme et continu sur le TEEY du cuivre. Nous avons démontré que le rendement d’émission électronique totale du cuivre est influencé par la présence d’un champ magnétique et par conséquent également l’effet multipactorSpace communication payload as well as magnetic confinement fusion devices, among other applications, are affected by multipactor effect. This undesirable phenomenon can appear inside high frequency (HF) components under vacuum and lead to increase the electron density in the vacuum within the system. Multipactor effect can thus disturb the wave signal and trigger local temperature increases or breakdowns. This PhD research aims to improve our understanding and the prediction of the multipactor effect. The multipactor phenomenon is a resonant process which can appear above a certain RF power threshold. To determine this power threshold, experimental tests or/and simulations are commonly used. We have made a study to evaluate the multipactor power threshold sensitivity to the TEEY. Two particular critical parameters have been found: first cross-over energy and the energies between the first cross-over and the maximum energies. In some situations, the HF components are submitted to DC magnetic fields which might affect the electron emission properties and hence the multipactor power threshold. Current multipactor simulation codes don’t take into account the effect of the magnetic field on the TEEY. A new experimental setup specially designed to investigate this effect was developed during this work. Our new experimental setup and the associated TEEY measurement technique were analysed and optimized thanks to measurements and SPIS simulations. We used the setup to study the influence of magnetic field perpendicular to the sample surface on the TEEY of copper. We have demonstrated that the magnetic field affects the copper TEEY, and hence multipactor power threshold
35
Tsitrone, Emmanuelle. "Controle des flux de particules dans un tokamak au moyen d'une structure a events." Aix-Marseille 1, 1995. http://www.theses.fr/1995AIX11050.
Full textAbstract:
Deux problemes restant a resoudre dans le developpement d'un reacteur a fusion sont: le controle des cendres des reactions de fusion (helium) et des impuretes, qui affectent les performances du plasma. L'evacuation de la chaleur atteignant la paroi (plusieurs dizaines de mw par m#2). Aucune des configurations existantes, limiteur a gorges et divertor axisymetrique, ne s'impose comme la solution ideale au controle simultane des flux de chaleur et de particules. Cela justifie l'etude de configurations alternatives, comme le limiteur a events, sujet de cette these, teste pour la premiere fois sur le tokamak tore supra. Le principe du limiteur a events repose sur la collection des neutres de recyclage, ce qui permet d'eviter une surcharge thermique locale. De fait, on constate qu'experimentalement, la temperature du prototype installe sur tore supra reste uniforme. En ce qui concerne la collection des particules, la pression obtenue, inferieure a celle d'un limiteur a gorges d'un facteur 3 en deuterium et 4 en helium, est neanmoins suffisante pour controler la densite du plasma. De plus, elle presente la meme evolution quadratique en fonction de la densite du plasma que celle du limiteur a gorges. Une modelisation a ete developpee pour interpreter ces resultats, decrivant le recyclage du plasma sur le limiteur et le pompage par les events. Une confrontation avec les donnees experimentales a permis de valider le modele. On a ensuite propose une optimisation du prototype en profilant les events, ce qui permet d'ameliorer d'un facteur 2 le pompage en deuterium comme en helium, sans pour autant retablir le desequilibre entre les deux. Par consequent, si le comportement thermique du limiteur a events est satisfaisant, son avenir depend fortement de la faisabilite d'un reacteur fonctionnant avec une efficacite de pompage moindre en helium qu'en deuterium/tritium
36
Hu, Yu. "Human Friendly Robot." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31501.
Full textAbstract:
In this project, a novel human friendly mobile robot navigation controller is investigated. By applying this controller, the mobile robot is able to work in a complicated environment with several humans and other obstacles avoiding them before a collision happens. This robot will have a preference in avoiding humans over other obstacles keeping human safety as its first consideration. To achieve this goal, three problems have to be solved. The first one is the robot should be able to “see” the environment and distinguish the human and the obstacles. The functions of human sensor and sonar sensor are presented. A new sensor fusion method for combining the information collected by these two sorts of sensors based on Dempster-Shafer evidence theory is also proposed. By using the sensor fusion method, the robot will have a better view of human. The second problem is the robot has to know how to avoid collision. A new navigation algorithm, based on an improved velocity potential field method, is then described. The way of calculating the distances of avoidance based on different kinds of obstacles is presented as well. The last problem is how to make the mobile robot put human as its first priority when avoiding collision. A summary of the methods which are used to protect human is mentioned. According to the simulation and the experimental results, the new mobile robot navigation controller successfully led the robot avoid collisions in complicated situations and always put human safety as its first consideration.
37
Schneider, Scott J. "A sensor fault controller scheme (SFCS) for multisensor fusion, validation, and fault tolerance issues associated with intelligent vehicle systems." The Ohio State University, 1998. http://rave.ohiolink.edu/etdc/view?acc_num=osu1407508995.
Full text
38
Mavkov, Bojan. "Control of coupled transport in Tokamak plasmas." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAT004/document.
Full textAbstract:
L'objectif de cette thèse est le développement de nouvelles méthodes d'analyse et de commande pour une classe d'équations aux dérivées partielles couplées permettant de modéliser le transport combiné du flux magnétique et de la pression (produit de la densité et de la température) dans les plasmas tokamak. Le système couplé est représenté par deux équations 1D de diffusion résistive. Dans cette thèse, on a obtenu deux types de modèles: le premier repose sur des principes physiques et le second exploite les données obtenues en utilisant des techniques d'identification des systèmes. La conception de commande est basée sur l'etude en dimension infinie en utilisant l'analyse de Lyapunov. Le contrôle composite est synthétisé en utilisant la théorie des perturbations singulières pour isoler la composante rapide de la composante lente. Tout le travail théorique est implémenté et testé dans des simulations basées sur la physique avancée en utilisant le simulateur de plasma pour les tokamaks DIII-D, ITER et TCVThe objective of this thesis is to propose new methods for analysis and control of partial differential equations that describe the coupling between the transport models of the electron pressure (density multiplied by the temperature) and the magnetic flux in the tokamak plasma. The coupled system is presented by two1D resistive diffusion equations. In this thesis two kinds of control models are obtained. The first is a first-principle driven model and the second one is the data-driven model obtained using system identification techniques. The control design is based on an infinite dimensional setting using Lyapunov analysis. Composite control is designed using singular perturbation theory to divide the fast from the slow component. All the theoretical work is implemented and benchmarked in advanced physics based on simulations using plasma simulator dor DIII-D, ITER and TCV tokamaks
39
Freire, Eduardo Oliveira. "Controle de Robos Moveis por Fusao de Sinais de Controle Usando Filtro de Informacao Descentralizado." Universidade Federal do Espírito Santo, 2002. http://repositorio.ufes.br/handle/10/4098.
Full textAbstract:
Made available in DSpace on 2016-08-29T15:32:39Z (GMT). No. of bitstreams: 1
tese_2261_Tese de Doutorado Eduardo Oliveira Freire20150522-151412.pdf: 2117717 bytes, checksum: 40e3a6f457916b01e2f6d67a7e9597c4 (MD5)
Previous issue date: 2002-08-14Esta Tese de Doutorado propõe uma abordagem alternativa para lidar com o problema da navegação de robôs móveis. Esta nova abordagem foi denominada fusão de sinais de controle. A técnica proposta apresentou bons resultados ao ser utilizada para controlar um robô na execução de tarefas relativamente complexas, como é demonstrado nos experimentos apresentados. A técnica é desenvolvida com base no Filtro de Informação Descentralizado, que é derivado aqui a partir das equações do Filtro de Kalman Descentralizado e do Filtro de Informação. Controladores de movimento disponíveis na literatura, e outros introduzidos aqui pela primeira vez, são utilizados para gerar sinais de controle. Estes sinais são fusionados utilizando um Filtro de Informação Descentralizado para produzir o sinal de saída o qual é enviado aos atuadores do robô. Também é realizada uma análise de estabilidade da arquitetura de controle proposta.
40
Tronko, Natalia. "Hamiltonian Perturbation Methods for Magnetically Confined Fusion Plasmas." Thesis, Aix-Marseille 2, 2010. http://www.theses.fr/2010AIX22088/document.
Full textAbstract:
Les effets auto-consistantes sont omniprésents dans les plasmas de fusion. Ils sont dus au fait que les équations de Maxwell qui décrivent l’évolution des champs électromagnétiques contiennent la densité de charge et de courant des particules.D’autre côté à son tour les trajectoires des particules sont influencés par les champs à travers les équations de mouvement ( où l’équation de Vlasov). Le résultat decette interaction auto-consistente se résume dans un effet cumulatif qui peut causer le déconfinement de plasma à l’intérieur d’une machine de fusion. Ce travail de thèse traite les problèmes liés à l’amélioration de confinement de plasma de fusion dans le cadre des approches hamiltonienne et lagrangien par le contrôle de transport turbulent et la création des barrières de transport. Les fluctuations auto-consistantes de champs électromagnétiques et de densités des particules sont à l’origine de l’apparition des instabilités de plasma qui sont à son tour liés aux phénomènes de transport. Dans la perspective de comprendre les mécanismes de la turbulence sousjacente,on considère ici l’application des méthodes hamiltoniennes pour des plasmasnon-collisionnellesThis thesis deals with dynamicla investigation of magnetically confined fusion plasmas by using Lagrangian and Hamilton formalisms. It consists of three parts. The first part is devoted to the investigation of barrier formation for the EXB drift model by means of the Hamiltonian control method. The strong magnetic field approach is relevant for magnetically confined fusion plasmas ; this is why at the first approximation one can consider the dynamics of particles driven by constant and uniform magnetic field. In this case only the electrostatic turbulence is taken into account. During this study the expressions for the control term (quadratic in perturbation amplitude) additive to the electrostatic potential, has been obtained. The effeciency of such a control for stopping turbulent diffusion has been shown analytically abd numerically. The second and the third parts of this thesis are devoted to study of self consistent phenomena in magnetized plasmas through the Maxwell-Vlasov model. In particular, the second part of this thesis treats the problem of the monumentum transport by derivation of its conservation law. the Euler-Poincare variational principle (with constrained variations) as well as Noether's theorem is apllied here. this derivation is realized in two cases : first, in electromagnetic turbulence case for the full Maxwell-Vlasov system, and then in electrostatic turbulence case for the gyrokinetic Maxwell-Vlasov system. Then the intrinsic mechanisms reponsible for the intrinsic plama rotation, that can give an important in plasma stabilization, are identified. The last part of this thesis deals with dynamicla reduction for the Maxwell-Vlaslov model. More particularly; the intrisic formulation for the guiding center model is derived. Here the term 'intrinsis" means that no fixed frame was used during its construction. Due to that not any problem related to the gyrogauge dependence of dynamics appears. The study of orbits of trapped particles is considered as one of the possible for illustration of the first step of such a dynamical reduction
41
Sala, Davi Alberto. "Controle de posição com múltiplos sensores em um robô colaborativo utilizando liquid state machines." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/163752.
Full textAbstract:
A ideia de usar redes neurais biologicamente inspiradas na computação tem sido amplamente utilizada nas últimas décadas. O fato essencial neste paradigma é que um neurônio pode integrar e processar informações, e esta informação pode ser revelada por sua atividade de pulsos. Ao descrever a dinâmica de um único neurônio usando um modelo matemático, uma rede pode ser implementada utilizando um conjunto desses neurônios, onde a atividade pulsante de cada neurônio irá conter contribuições, ou informações, da atividade pulsante da rede em que está inserido. Neste trabalho é apresentado um controlador de posição no eixo Z utilizando fusão de sensores baseado no paradigma de Redes Neurais Recorrentes. O sistema proposto utiliza uma Máquina de Estado Líquido (LSM) para controlar o robô colaborativo BAXTER. O framework foi projetado para trabalhar em paralelo com as LSMs que executam trajetórias em formas fechadas de duas dimensões, com o objetivo de manter uma caneta de feltro em contato com a superfície de desenho, dados de sensores de força e distância são alimentados ao controlador. O sistema foi treinado utilizando dados de um controlador Proporcional Integral Derivativo (PID), fundindo dados de ambos sensores. Resultados mostram que a LSM foi capaz de aprender o comportamento do controlador PID em diferentes situações.The idea of employing biologically inspired neural networks to perform computation has been widely used over the last decades. The essential fact in this paradigm is that a neuron can integrate and process information, and this information can be revealed by its spiking activity. By describing the dynamics of a single neuron using a mathematical model, a network in which the spiking activity of every single neuron will get contributions, or information, from the spiking activity of the embedded network. A positioning controller based on Spiking Neural Networks for sensor fusion suitable to run on a neuromorphic computer is presented in this work. The proposed framework uses the paradigm of reservoir computing to control the collaborative robot BAXTER. The system was designed to work in parallel with Liquid State Machines that performs trajectories in 2D closed shapes. In order to keep a felt pen touching a drawing surface, data from sensors of force and distance are fed to the controller. The system was trained using data from a Proportional Integral Derivative controller, merging the data from both sensors. The results show that the LSM can learn the behavior of a PID controller on di erent situations.
42
Alvarez, Bestard Guillermo. "Sensor fusion and embedded devices to estimate and control the depth and width of the weld bead in real time." reponame:Repositório Institucional da UnB, 2017. http://repositorio.unb.br/handle/10482/31429.
Full textAbstract:
Tese (doutorado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2017.Submitted by Raquel Almeida (raquel.df13@gmail.com) on 2018-03-13T20:33:59Z No. of bitstreams: 1 2017_GuillermoAlvarezBestard.pdf: 9664678 bytes, checksum: 358024e196bf55e45bb81b4815254ad7 (MD5)
Approved for entry into archive by Raquel Viana (raquelviana@bce.unb.br) on 2018-03-13T21:24:34Z (GMT) No. of bitstreams: 1 2017_GuillermoAlvarezBestard.pdf: 9664678 bytes, checksum: 358024e196bf55e45bb81b4815254ad7 (MD5)
Made available in DSpace on 2018-03-13T21:24:34Z (GMT). No. of bitstreams: 1 2017_GuillermoAlvarezBestard.pdf: 9664678 bytes, checksum: 358024e196bf55e45bb81b4815254ad7 (MD5) Previous issue date: 2018-03-13
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).
O processo GMAW é amplamente utilizado na indústria, mas seu controle automático está limitado pela dificuldade existente em medir as principais grandezas do processo e fechar a malha de controle. As condições ambientais adversas dificultam o uso dos sistemas de medição convencionais para obter informações da geometria do cordão de solda. Nestas condições o desenvolvimento do sistema de medição é complexo e o correto desempenho não é garantido. Neste trabalho desenvolvem-se sistemas e ferramentas para coletar os valores das variáveis e fornecer estímulos ao processo de soldagem GMAW convencional com fonte de soldagem de tensão constante, permitindo a estimação da geometria do cordão de solda em um sistema de controle em malha aberta. Os estimadores da penetração e a largura do cordão são implementados baseados na fusão dos dados termográficos, a intensidade da corrente e a tensão de soldagem em uma rede neural. Desenvolveu-se um algoritmo para extrair as caraterísticas da imagem infravermelha e para fornecer essas informações aos estimadores. Para validar os modelos dos estimadores foi implementado um perfilômetro a laser para obter as dimensões externas do cordão de solda e um algoritmo de processamento de imagem para medir a penetração fazendo um corte longitudinal no cordão. Os resultados obtidos são documentados e discutidos no texto. Este trabalho também inclui uma proposta de projeto para um emulador robótico de soldagem orbital e seu sistema de controle multivariável para controlar a geometria do cordão de solda utilizando os estimadores desenvolvidos. Os algoritmos são otimizados para dispositivos embarcados e processamento em tempo real.
The GMAW process is widely used in industry, but the automatic control is limited by the difficulty in the process for measuring the main magnitudes and for closing the control loop. Adverse environmental conditions in the process make it harder to use conventional measurement systems to obtain information about the weld bead geometry. Under these conditions, the control system design is complex and good performance is not guaranteed. In this research, systems and tools were developed to collect the values of the welding variables and send stimuli to the GMAW conventional process with constant voltage power source, which us allows to estimate the geometry of the weld bead in an open-loop control. The depth and width estimates of the weld bead are implemented based on the fusion of the thermographic data, the welding current and the welding voltage in a neural network. An algorithm was developed to extract the features of the infrared image and deliver this information to the estimators. To validate the estimator models, a laser profilometer was implemented to measure the external dimensions of the bead and an image processing algorithm to measure the depth by making a longitudinal cut in the weld bead. The results obtained are documented and discussed in the text. This work also includes a design proposal for a robotic orbital welding emulator and its multivariable control system to control the geometry of the weld bead using the developed estimators. The algorithms are optimized for embedded devices and real-time processing.
43
Pontelli, Cristiano Okada. "Estratégias de controle para isolação ativa de vibrações em barras de pulverizadores agrícolas." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18146/tde-03102013-093840/.
Full textAbstract:
A utilização de sistemas de controle para estabilidade de conjuntos de barras para pulverizadores agrícolas é uma tendência devida principalmente aos problemas ambientais e de custo. Neste trabalho, o comportamento dinâmico de um pulverizador de arrasto é analisado através de um modelo não linear, obtido através de técnicas de modelagem de sistemas multicorpos utilizando-se o programa ADAMS. Foram utilizadas duas estratégias de controle PID e \"fuzzy\" a partir de medidas obtidas com fusão de sensores. A estratégia de controle clássica PID foi desenvolvida e implementada no modelo não linear no ADAMS através de ferramentas internas existentes no programa. Já a estratégia \"fuzzy\" foi desenvolvida e implementada no modelo não linear no ADAMS através da técnica de co-simulação ADAMS/Matlab. O comportamento dos sistemas de controle foi investigado através de simulação computacional. Foram testados alguns tipos de entradas (entrada degrau, entrada harmônica, entrada randômica e entrada randômica com descontinuidades bruscas). Em todas as simulações os resultados obtidos com os sistemas de controles ativos mostraram melhor estabilidade do conjunto de barras. Entre as leis de controle implementadas (PID e \"fuzzy\") não houve grandes diferenças entre as oscilações da barra exceto na entrada do tipo randômica com descontinuidades bruscas. Neste caso a lei de controle \"fuzzy\" apresentou uma grande melhoria com boa atenuação das oscilações do conjunto de barras quando comparadas com a aplicação do sistema de controle PID.The use of active control systems for stability of booms in agricultural sprayers trend is mainly due to the environmental and costs question. In this work, the dynamic behavior of a trailed sprayer is analyzed using a nonlinear model, obtained through techniques of modeling multibody systems using the ADAMS. It is used two active control strategies, PID classical control and fuzzy, with measured data from sensor fusion. The classical PID control strategy was developed and implemented in a nonlinear model on ADAMS software using existing tools built into the program. Fuzzy was another strategy developed and implemented in the nonlinear model on ADAMS software using a technique of co-simulation ADAMS/Matlab. The behavior of control systems was investigated through computer simulation. It was tested some types of inputs (step input, harmonic input, random input and random input with abrupt discontinuities). All simulations data obtained from the applications of active systems showed better stability for boom assembly. Among the implemented two active control laws (PID and \"fuzzy\") there were no significant differences between the oscillations attenuation of the boom, except with the random input with abrupt discontinuities. wherein this case the application of the active control \"fuzzy\" strategy developed better stability on boom than the application of PID control.
44
Ventura, José Miguel Vilca. "Estudo de coordenação de robôs móveis com obstáculos." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/18/18153/tde-08112011-090037/.
Full textAbstract:
Coordenação de robôs móveis é um tópico importante de pesquisa dado que existem tarefas que podem ser desenvolvidas de forma mais eficiente e com menor custo por um grupo de robôs do que por um só robô. Nesta dissertação é apresentado um estudo sobre coordenação de robôs móveis para o problema de navegação em ambientes externos. Para isso, foi desenvolvido um sistema de localização utilizando os dados de odometria e do receptor GPS, e um sistema de desvio de obstáculos para planejar a trajetória livre de obstáculos. Os movimentos coordenados foram realizados em função de um líder e qualquer robô da formação pode assumir a liderança. A liderança é assumida pelo robô que ultrapassar a distância mínima a um obstáculo. Movimentos estáveis são gerados através de uma lei de controle descentralizada baseada nas coordenadas dos robôs. Para garantir a estabilidade da formação quando há alternância de líder ou remoção de robôs, foi feito controle tolerante a falhas para um grupo de robôs móveis. O controle tolerante a falhas é baseado em controle H \'INFINITO\' por realimentação da saída de sistemas lineares sujeitos a saltos Markovianos para garantir a estabilidade da formação quando um dos robôs é perdido durante o movimento coordenado. Os resultados do sistema de localização mostram que o uso de filtro robusto para a fusão de dados produz uma melhor estimativa da posição do robô móvel. Os resultados também mostram que o sistema de desvio de obstáculos é capaz de gerar uma trajetória livre de obstáculos em ambientes desconhecidos. E por fim, os resultados do sistema de coordenação mostram que o grupo de robôs mantém a formação desejada percorrendo a trajetória de referência na presença de distúrbios ou quando um robô sai da formação.Coordination of mobile robots is an important topic of research because there are tasks that may be too difficult for a single robot to perform alone, these tasks can be performed more efficiently and cheaply by a group of mobile robots. This dissertation presents a study on the coordination of mobile robots to the problem of navigation in outdoor environments. To solve this problem, a localization system using data from odometry and GPS receiver, and an obstacle avoidance system to plan the collision-free trajectory, were developed. The coordinated motions are performed by the robots that follow a leader, and any robot of the formation can assume the leadership. The leadership is assumed by a robot when it exceeds the threshold distance to an obstacle. Stable motions are generated by a decentralized control law based on the robots coordinates. To ensure the stability formation when there is alternation of leader or one of the robots is removed, we made a fault tolerant control for a group of mobile robots. The fault tolerant approach is based on output feedback H \'INFINITE\' control of Markovian jump linear systems to ensure stability of the formation when one of the robots is lost during the coordinated motion. The results of the localization system show that the use of robust filter for data fusion produces a better estimation of the mobile robots position. The results also show that the obstacle avoidance system is capable of generating a path free from obstacles in unknown environments. Finally, the results of the coordination system show that the group of robots maintain the desired formation along the reference trajectory in the presence of disturbance or removal of one of them.
45
Silva, Natássya Barlate Floro da. "Development of an autonomous unmanned aerial vehicle specification of a fixed-wing vertical takeoff and landing aircraft." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/55/55134/tde-16102018-100220/.
Full textAbstract:
Several configurations of Unmanned Aerial Vehicles (UAVs) were proposed to support different applications. One of them is the tailsitter, a fixed-wing aircraft that takes off and lands on its own tail, with the high endurance advantage from fixed-wing aircraft and, as helicopters and multicopters, not requiring a runway during takeoff and landing. However, a tailsitter has a complex operation with multiple flight stages, each one with its own particularities and requirements, which emphasises the necessity of a reliable autopilot for its use as a UAV. The literature already introduces tailsitter UAVs with complex mechanisms or with multiple counter-rotating propellers, but not one with only one propeller and without auxiliary structures to assist in the takeoff and landing. This thesis presents a tailsitter UAV, named AVALON (Autonomous VerticAL takeOff and laNding), and its autopilot, composed of 3 main units: Sensor Unit, Navigation Unit and Control Unit. In order to choose the most appropriate techniques for the autopilot, different solutions are evaluated. For Sensor Unit, Extended Kalman Filter and Unscented Kalman Filter estimate spatial information from multiple sensors data. Lookahead, Pure Pursuit and Line-of-Sight, Nonlinear Guidance Law and Vector Field path-following algorithms are extended to incorporate altitude information for Navigation Unit. In addition, a structure based on classical methods with decoupled Proportional-Integral-Derivative controllers is compared to a new control structure based on dynamic inversion. Together, all these techniques show the efficacy of AVALONs autopilot. Therefore, AVALON results in a small electric tailsitter UAV with a simple design, with only one propeller and without auxiliary structures to assist in the takeoff and landing, capable of executing all flight stages.Diversas configurações de Veículos Aéreos Não Tripulados (VANTs) foram propostas para serem utilizadas em diferentes aplicações. Uma delas é o tailsitter, uma aeronave de asa fixa capaz de decolar e pousar sobre a própria cauda. Esse tipo de aeronave apresenta a vantagem de aeronaves de asa fixa de voar sobre grandes áreas com pouco tempo e bateria e, como helicópteros e multicópteros, não necessita de pista para decolar e pousar. Porém, um tailsitter possui uma operação complexa, com múltiplos estágios de voo, cada um com suas peculiaridades e requisitos, o que enfatiza a necessidade de um piloto automático confiável para seu uso como um VANT. A literatura já introduz VANTs tailsitters com mecanismos complexos ou múltiplos motores contra-rotativos, mas não com apenas um motor e sem estruturas para auxiliar no pouso e na decolagem. Essa tese apresenta um VANT tailsitter, chamado AVALON (Autonomous VerticAL takeOff and laNding), e seu piloto automático, composto por 3 unidades principais: Unidade Sensorial, Unidade de Navegação e Unidade de Controle. Diferentes soluções são avaliadas para a escolha das técnicas mais apropriadas para o piloto automático. Para a Unidade Sensorial, Extended Kalman Filter e Unscented Kalman Filter estimam a informação espacial de múltiplos dados de diversos sensores. Os algoritmos de seguimento de trajetória Lookahead, Pure Pursuit and Line-of-Sight, Nonlinear Guidance Law e Vector Field são estendidos para considerar a informação da altitude para a Unidade de Navegação. Além do mais, uma estrutura baseada em métodos clássicos com controladores Proporcional- Integral-Derivativo desacoplados é comparada a uma nova estrutura de controle baseada em dinâmica inversa. Juntas, todas essas técnicas demonstram a eficácia do piloto automático do AVALON. Portanto, AVALON resulta em um VANT tailsitter pequeno e elétrico, com um design simples, apenas um motor e sem estruturas para auxiliar o pouso e a decolagem, capaz de executar todos os estágios de voo.
46
Martins, Caroline Gameiro Lopes [UNESP]. "Controle de dinâmica caótica com toros robustos." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/91880.
Full textAbstract:
Made available in DSpace on 2014-06-11T19:25:31Z (GMT). No. of bitstreams: 0
Previous issue date: 2010-07-21Bitstream added on 2014-06-13T20:14:01Z : No. of bitstreams: 1
martins_cgl_me_rcla.pdf: 5684050 bytes, checksum: 3934e04161c8cf598ab0e9e151d9f8fe (MD5)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Investigamos nesta dissertação a introdução de uma barreira dinâmica em diferentes sistemas físicos caóticos, a fim de analisar a influência que esta barreira causa na dinâmica e topologia destes sistemas. A barreira principal deste estudo é a barreira denominada Toro Robusto, que nada mais é do que uma curva invariante no espaço de fases em meio a estruturas de ressonância, mares de caos, etc. A barreira Toro Robusto bloqueia a difusão caótica no espaço de fases associado ao sistema físico, e causa também uma estabilização em sua vizinhança linear. Introduziremos Toros Robustos em vários tipos de sistemas dinâmicos, como por exemplo, em uma Hamiltoniana “Toy Model” a fim de entender o seu efeito no processo de reconexão ou “overlap” de ressonâncias isócronas. Toros Robustos quebrando a dimerização de cadeias de ressonância também foram estudados no mapa padrão “não-twist”. O bloqueio da difusão de Arnold no mapa padrão acoplado também foi mostrado, assim como, a introdução de Toros Robustos em sistemas utilizados em física de plasmas, como meio de controle de caos em plasma confinado em Tokamak. Outra barreira apresentada aqui é a barreira do tipo “meander” que surge através do processo de reconexão de ressonâncias no espaço de fases. Introduziremos um novo mapa discreto que chamamos de Mapa padrão “não-twist” labiríntico, que apresenta múltiplas regiões de barreiras “meanders” por todo o espaço de fases
We investigated in this work the introduction of a dynamical barrier in different chaotic physical systems in order to analyze the influence that it causes in the topology and in the dynamics of them. The main barrier studied here is called Robust Tori which is an invariant curve in the phase space permeated by resonance structures and chaotic seas. The Robust Torus barrier blocks the chaotic diffusion in the phase space of the associated physical system, and it also causes a linear stabilization in its neighborhood. Robust Tori will be introduced in several types of dynamic systems, such as in a Toy Model Hamiltonian in order to understand their effect on the reconnection process or overlap of isochronous resonances. The breakdown of resonance dimerization by Robust Tori was also studied using the nontwist standard map. The blocking of Arnold diffusion in the coupled standard map was also shown, as well as the introduction of Robust Tori in relevant models for plasma physics as a tool for controlling chaos in confined plasmas in Tokamaks. Another barrier, which is presented here, is the meander barrier that emerges through the reconnection process of resonances in phase space. We will also introduce a new discrete map, which we call labyrinthic standard non-twist map that shows multiple regions of meanders barriers around the phase space
47
Martins, Caroline Gameiro Lopes. "Controle de dinâmica caótica com toros robustos /." Rio Claro : [s.n.], 2010. http://hdl.handle.net/11449/91880.
Full textAbstract:
Orientador: Ricardo Egydio de CarvalhoBanca: Iberê Luiz Caldas
Banca: Marisa Roberto
Resumo: Investigamos nesta dissertação a introdução de uma barreira dinâmica em diferentes sistemas físicos caóticos, a fim de analisar a influência que esta barreira causa na dinâmica e topologia destes sistemas. A barreira principal deste estudo é a barreira denominada Toro Robusto, que nada mais é do que uma curva invariante no espaço de fases em meio a estruturas de ressonância, mares de caos, etc. A barreira Toro Robusto bloqueia a difusão caótica no espaço de fases associado ao sistema físico, e causa também uma estabilização em sua vizinhança linear. Introduziremos Toros Robustos em vários tipos de sistemas dinâmicos, como por exemplo, em uma Hamiltoniana "Toy Model" a fim de entender o seu efeito no processo de reconexão ou "overlap" de ressonâncias isócronas. Toros Robustos quebrando a dimerização de cadeias de ressonância também foram estudados no mapa padrão "não-twist". O bloqueio da difusão de Arnold no mapa padrão acoplado também foi mostrado, assim como, a introdução de Toros Robustos em sistemas utilizados em física de plasmas, como meio de controle de caos em plasma confinado em Tokamak. Outra barreira apresentada aqui é a barreira do tipo "meander" que surge através do processo de reconexão de ressonâncias no espaço de fases. Introduziremos um novo mapa discreto que chamamos de Mapa padrão "não-twist" labiríntico, que apresenta múltiplas regiões de barreiras "meanders" por todo o espaço de fases
Abstract: We investigated in this work the introduction of a dynamical barrier in different chaotic physical systems in order to analyze the influence that it causes in the topology and in the dynamics of them. The main barrier studied here is called Robust Tori which is an invariant curve in the phase space permeated by resonance structures and chaotic seas. The Robust Torus barrier blocks the chaotic diffusion in the phase space of the associated physical system, and it also causes a linear stabilization in its neighborhood. Robust Tori will be introduced in several types of dynamic systems, such as in a Toy Model Hamiltonian in order to understand their effect on the reconnection process or overlap of isochronous resonances. The breakdown of resonance dimerization by Robust Tori was also studied using the nontwist standard map. The blocking of Arnold diffusion in the coupled standard map was also shown, as well as the introduction of Robust Tori in relevant models for plasma physics as a tool for controlling chaos in confined plasmas in Tokamaks. Another barrier, which is presented here, is the meander barrier that emerges through the reconnection process of resonances in phase space. We will also introduce a new discrete map, which we call labyrinthic standard non-twist map that shows multiple regions of meanders barriers around the phase space
Mestre
48
Dota, Mara Andréa. "Modelo para a classificação da qualidade da água contaminada por solo usando indução por árvore de decisão." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/3/3141/tde-14082015-151933/.
Full textAbstract:
A possibilidade de avaliar remotamente e de forma instantânea alterações na qualidade das águas em função da entrada de solos permite o monitoramento de processos ecológicos como o assoreamento, perdas e solos, carreamento de pesticidas e degradação de habitats aquáticos. Com a utilização de um modelo automatizado, torna-se possível um monitoramento em tempo real remoto coletando dados por meio de Redes de Sensores Sem Fio. Esta pesquisa propõe um modelo de classificação da qualidade da água contaminada por solo usando técnicas de Árvore de Decisão. Com este modelo torna-se possível acompanhar alterações que venham a ocorrer em águas superficiais indicando o nível de contaminação por solo com maior rapidez do que a forma convencional que necessita de análise em laboratório e coleta de amostra manual. A classificação proposta considera sete classes de qualidade da água, conforme dados de um experimento conduzido em laboratório. Foram utilizadas técnicas de Inteligência Artificial com o intuito de realizar a Fusão de Sensores para avaliar, em tempo real, as leituras dos sensores, indicando a qual classe de qualidade a amostra se enquadra. Na verificação de quantas classes seria o ideal, utilizou-se o algoritmo k-means++. Para a construção do modelo de classificação foram usadas técnicas de Indução por Árvore de Decisão, tais como: Best-First Decision Tree Classifier BFTree, Functional Trees FT, Naïve Bayes Decision Tree NBTree, Grafted C4.5 Decision Tree J48graft, C4.5 Decision Tree J48, LADTree. Os testes realizados indicam que a classificação proposta é coerente, visto que os diferentes algoritmos comprovaram uma relação estatística forte entre as instâncias das classes, garantindo que o modelo proposto irá predizer saídas para entradas de dados desconhecidas com acurácia. Os algoritmos com melhores resultados foram FT, J48graft e J48.The possibility to remotely and instantaneously evaluate changes in water quality due to soil contamination allows monitoring ecological processes such as siltation, soil losses, loading of pesticides and degradation of aquatic habitats. Using an automated model to classify soil-contaminated water quality allows for a remote realtime monitoring by collecting data using Wireless Sensor Networks. This study proposes a model to classify soil-contaminated water quality by using Decision Tree techniques. With this model, it is possible to track changes that may occur in surface waters indicating the level of contamination by soil faster than the conventional way, which requires laboratory analysis and manual sampling. The classification proposed considers seven classes of water quality, according to data from an experiment carried out in laboratory. Artificial Intelligence techniques were used in order to implement Sensor Fusion to evaluate, in real time, sensor readings to which class the sample quality fits. By checking how many classes would be ideal, the k-means + + algorithm was used. To build the classification model, Decision Tree Induction techniques were used, such as: Best-First Decision Tree Classifier BFTree, Functional Trees FT, Naïve Bayes Decision Tree NBTree, Grafted C4.5 Decision Tree J48graft, C4.5 Decision Tree J48, LADTree. Tests indicated that the proposed classification is consistent because different algorithms results confirmed a strong statistical relationship between instances of classes, ensuring that this model will predict outputs to unknown inputs accurately. The algorithms with best results were FT, J48graft and J48.
49
CICIARELLO, MARILENA. "Ruolo del sistema Ran/importine nel controllo del fuso mitotico in cellule di mammifero." Doctoral thesis, La Sapienza, 2005. http://hdl.handle.net/11573/916955.
Full text
50
Boucher, Dominique. "Etude et modelisation du transport de l'energie et des particules dans un plasma de fusion thermonucleaire controlee. Application au transport anormal et aux conditions de fonctionnement du tokamak." Palaiseau, Ecole polytechnique, 1992. http://www.theses.fr/1992EPXX0019.
Full textAbstract:
L'objet de cette these est d'aboutir a une modelisation de l'ensemble des phenomenes de transport observes dans le plasma d'un tokamak que ce soit pour le transport des particules ou celui de l'energie. Pour cela, une methode predictive a ete choisie: la modelisation se traduit en equations mathematiques qui sont ensuite resolues numeriquement de maniere auto-consistante. Cela permet d'ecrire un simulateur de tokamak dont on peut ensuite comparer les predictions aux observations experimentales. Le modele de transport de l'energie est celui de gradient de temperature electronique critique developpe par p-h rebut et al. Tandis que le transport des particules est un travail original presente dans la these. Ce dernier modele met en evidence le lien etroit entre le profil de facteur de securite et le pinch' des particules. L'ensemble de ces deux modeles, complete par une modelisation adequate de la geometrie torique et des termes source, est ensuite compare a une gamme tres large d'observations experimentales (principalement realisees dans le tokamak du jet). En particulier des experiences aussi diverses que les chauffages hors de l'axe, les modes h, les modes a ions chauds ou les plasmas a performances ameliorees suite a une injection de glacon (modes p. E. P. ) sont reproduits avec succes par le simulateur. Ces simulations donnent de solides indications en faveur de l'existence d'un gradient de temperature critique et permettent de comprendre de maniere coherente le transport des particules. Dans un dernier temps les consequences d'un tel modele pour le fonctionnement d'un reacteur de fusion thermonucleaire controlee sont detaillees