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Tsai, Frank J. (Frank Jin-Fong) 1976. "Distributed active control for tension structures." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/81544.
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McCabe, Brian John. "Underslung Payload Tension Control from an Autonomous Unmanned Helicopter." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/32679.
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A tension control algorithm for the deployment of a unmanned ground vehicle from an
autonomous helicopter is designed and tested in this thesis. The physical hardware which
the controller will run on is detailed. The plant model and underlying controllers are derived
and modeled. The tension controller algorithm is selected, derived, and modeled. The
parameters of the tension controller are chosen and simulations are run with the chosen
parameters. The tension control algorithm is run on the physical hardware, successfully
demonstrating tension control on a ground vehicle. Robustness simulations are run for a
change in the radius of the spool and the length of the tether. Lastly, Future work is
outlined on several paths to move forward with the tension controller.Master of Science
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Andrade, Virgínia Ribeiro de. "Caveolae control intercellular tension during cytokinesis and promote successful abscission." Electronic Thesis or Diss., Sorbonne université, 2021. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2021SORUS533.pdf.
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Pendant la cytocinèse, le pont intercellulaire qui relie les cellules filles subit des forces de traction qui retardent l'abscission en empêchant l'assemblage de la machinerie de scission ESCRT. L'abscission est donc déclenchée par la libération de la tension, mais la façon dont la tension du pont intercellulaire est contrôlée est inconnue. Nous rapportons ici que les cavéoles, connues pour contrôler la tension membranaire lors d'un stress mécanique dans les cellules en interphase, sont situées au niveau du midbody, du site d'abscission et à l'interface du pont intercellulaire/cellule dans les cellules en division. Fonctionnellement, la perte des cavéoles retarde le recrutement de l'ESCRT-III pendant la cytocinèse et retarde l'abscission. Ceci est la conséquence d'une multiplication par 2 de la tension du pont intercellulaire mesurée par ablation laser, associée à une augmentation locale de l'activité de la myosine II à l'interface du pont intercellulaire/cellule. Nous proposons donc que les cavéoles tamponnent la tension membranaire et limitent la contractilité au niveau du pont intercellulaire pour favoriser l'assemblage de l'ESCRT-III et l'abscissionDuring cytokinesis, the intercellular bridge (ICB) connecting the daughter cells experiences pulling forces, which delay abscission by preventing the assembly of the ESCRT scission machinery. Abscission is thus triggered by tension release, but how ICB tension is controlled is unknown. Here, we report that caveolae, which are known to control membrane tension upon mechanical stress in interphase cells, are located at the midbody, at the abscission site and at the ICB/cell interface in dividing cells. Functionally, the loss of caveolae delays ESCRT-III recruitment during cytokinesis and impairs abscission. This is the consequence of a 2-fold increase of ICB tension measured by laser ablation, associated with a local increase in myosin II activity at the ICB/cell interface. We thus propose that caveolae buffer membrane tension and limit contractibility at the ICB to promote ESCRT-III assembly and cytokinetic abscission
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Kim, Myeongseop. "MICRO-GAS EXCHANGER FOR OXYGEN TENSION CONTROL IN BIOLOGICAL MICROFLUIDIC SYSTEMS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1462871978.
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Dye, M. G. "The MCS algorithm for the co-ordinated control of web tension and transport." Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294367.
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Eren, Recep. "An integrated electronic control of take-up and let-off motions in a weaving machine." Thesis, University of Manchester, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295662.
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Morin, Juliette. "Coordination des moyens de réglage de la tension à l'interface réseau de distribution et de transport; et évolution du réglage temps réel de la tension dans les réseaux de distribution." Thesis, Paris, ENSAM, 2016. http://www.theses.fr/2016ENAM0020/document.
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Le réglage de la tension et la gestion de la puissance réactive est d’une importance capitale pour le bon fonctionnement du système électrique. Les réseaux de distribution connaissent des modifications profondes qui sont tant techniques avec l’insertion de la production décentralisée ou l’enfouissement des lignes aériennes, que réglementaires avec l’entrée en vigueur des codes de réseaux Européens. Aussi, des alternatives aux réglages traditionnels de tension et la mise en place de contrôle des échanges de puissance réactive à l’interface réseau de transport/distribution peuvent être développées. Dans le cadre de ces travaux de doctorat, une solution basée sur l’amélioration du réglage temps réel des réseaux de distribution ainsi que la mise en place d’une gestion conjointe de la puissance réactive entre les gestionnaires du réseau de transport et distribution a été proposée. Ce réglage temps réel est basé sur une méthode de commande prédictive, et s’appuie notamment sur le régleur en charge ou les productions décentralisées pour réaliser un réglage de la tension au sein d’un réseau de distribution et contrôler les échanges de puissance réactive. Les références de puissance réactive à atteindre à l’interface entre réseau de distribution et de transport sont déterminées par le gestionnaire du réseau de transport pour ses propres besoins et en connaissance des réserves de puissance réactive disponible depuis les réseaux de distribution. Par rapport à la littérature, notre démarche a pour originalité de prendre en compte les problèmes à l’interface des réseaux de distribution et de transport et démontre l’intérêt de mener des études conjointes entre gestionnairesVoltage and reactive power control are of paramount importance to ensure safe and reliable operation of the power system. Distribution grids are undergoing major changes, namely the insertion of distributed generation and the replacement of overhead lines. Along with these physical evolutions, new distribution networks should comply with the requirements of the European Grid Codes on the reactive power exchange at the HV/MV interface. To handle these new operational concerns, alternative solutions to the traditional voltage and reactive power control can be found. In our work, a scheme based on the evolution of the real-time Volt Var Control (VVC) of distribution networks and a joint coordination for the reactive power management of a HV system has been proposed. The real-time VVC of MV grids is based on a predictive control method. This control uses in a coordinated manner the on load tap changer, the distributed generation and the capacitor banks to enforce a suitable MV voltage profile and an appropriate HV/MV reactive power exchange. The reactive power targets at the HV/MV interface are determined by the Transmission System Operator for its own requirements but considering the true MV reactive power reserve. Compared to the literature, the novelty of our approach consists in considering the concerns at the HV/MV system interface. Next our works have shown the relevance of performing joint transmission and distribution system operators analysis
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Zhou, Wankun. "Robust and Decentralized Control of Web Winding Systems." Cleveland State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=csu1199774017.
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Grier, Finlay. "The Reduction of Tension Headache Using EMG Biofeedback and Locus of Control as Predictors." Thesis, University of North Texas, 1989. https://digital.library.unt.edu/ark:/67531/metadc332051/.
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This study investigates the status of biofeedback treatment and locus of control (LOC) affiliation on the reduction of tension headache. Three LOC groups designated as internals, powerful-other externals and chance externals (using Wallston and Wallston's, 1978, Multidimensional Health Locus of Control Scale) were administered an eight week electromyogram (EMG) frontalis muscle biofeedback training program using an Autogen 1700 biofeedback unit. Subjects were 12 female and four male undergraduate students who had a history of tension headache. Results indicated no significant difference in frontalis muscle tension between the beginning and end of sessions in either a biofeedback or self-control condition for any of the LOC groups. Further, there was no significant difference among LOC groups in ability to reduce muscle tension in either the training or self-control condition. Finally, neither biofeedback training nor LOC groups were significant predictors of headache reduction. Extreme within-group variability and small sample size affected study findings and these and other implications for future research are discussed.
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Kuchar, Olga Anna. "Development of animated finger movements via a neural network for tendon tension control." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq39322.pdf.
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Mondragon-Teran, P. "Impact of oxygen tension control on neuronal differentiation of Embryonic Stem Cells (ESC)." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1302283/.
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Embryonic Stem Cells (ESC) have the potential to differentiate into any adult cell type even after extended in-vitro culture. These cells have the scope to be a source of specialized cells for pharmaceutical screening and potential cell based transplantation therapies. The successful commercialization of ESCderived products will be highly dependent on the development of cost-effective production bioprocesses. Currently, the most inefficient phase of these bioprocesses is cell differentiation, resulting in low numbers and purity of the target phenotype. Research described in this thesis investigated whether physiological oxygen tensions would influence the yield and purity of neuronal cells during mouse ESC (mESC) differentiation. A chemically defined media, monolayer protocol for the neuronal differentiation of mouse ESC in conjunction with a hypoxia chamber to control the oxygen tension on the growth surface was used. In the first part of the study, it was found that 2% O2 enhanced the yield of cells expressing neuron specific markers (βIII-tubulin and MAP2) as compared with traditional culture conditions (20% O2). Further experiments demonstrated that higher neuronal production was achieved when mES cells were differentiated in the range 4 – 10% O2; an increase in neural rosette diameter was detected within the same oxygen conditions. Embryo development is carried out under hypoxic conditions before week 11 (in humans) of gestation and before 9 days of gestation in the case of mouse embryo. After these indicated stages, blood starts to flow from mother to embryo and oxygen conditions rises from hypoxic to different physiological oxygen values (generally rises from 0% to 2%, 5% or 8% depending of the organ or tissue analyzed). Step changes in oxygen tension during mESC neuronal in vitro differentiation were performed in order to mimic the described in vivo conditions. These results highlight that mimicking in-vivo oxygen tensions during early embryo development can be used to achieve significant enhancements in the yield of neuronal cells from ESC differentiation protocols. Automated mES neuronal differentiation under static oxygen conditions was implemented in order to avoid transient changes from in vitro controlled physiological values to laboratory environmental 20% O2 conditions while manual processing. This lead to an increase of neuronal maturation as observed in the higher MAP2 (mature neuronal marker) expression. Interestingly cell metabolism was also influenced by static oxygen conditions. Results described in this thesis establish the importance of controlling oxygen tension either in a manual or automated way during the in vitro mESC neuronal differentiation. The strategies proposed in this thesis will allow developing higher efficiency and higher purity of neurons from a stem cell bioprocessing perspective.
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Günnel, Andreas, and Roland Herzog. "Optimal Control Problems in Finite-Strain Elasticity by Inner Pressure and Fiber Tension." Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-209295.
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Optimal control problems for finite-strain elasticity are considered. An inner pressure or an inner fiber tension is acting as a driving force. Such internal forces are typical, for instance, for the motion of heliotropic plants, and for muscle tissue. Non-standard objective functions relevant for elasticity problems are introduced. Optimality conditions are derived on a formal basis, and a limited-memory quasi-Newton algorithm for their solution is formulated in function space. Numerical experiments confirm the expected mesh-independent performance.
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Vidal, Renaud. "La haute fiabilité comme gestion de la tension entre le contrôle et l'écoute : l'étude empirique des opérations de secours." Thesis, Aix-Marseille 3, 2011. http://www.theses.fr/2011AIX32070.
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La fréquence et la sévérité des feux de forêt de grande ampleur ont augmenté dans les vingt dernières années, par la conjonction de trois tendances lourdes : le réchauffement climatique, l’extension des interfaces périurbaines et l’augmentation de la biomasse. Par conséquent, la fiabilisation des opérations de lutte, et en particulier des équipes de commandement, devient un enjeu important. Mais les opérations de secours constituent surtout une fenêtre particulièrement intéressante sur le fait organisationnel en général et les processus de construction de sens en particulier. En effet, les pompiers sont confrontés à des exigences organisationnelles en conflit : stabiliser le sens des situations pour assurer l’efficacité de l’action collective (processus de contrôle), et le réévaluer en permanence pour détecter et s’adapter aux évolutions inattendues (processus d’écoute). Le contrôle cherche à fiabiliser les apprentissages, capitalise les succès, ignore le bruit, simplifie, privilégie l’anticipation, et oriente l’attention sur les objectifs de l’action et sur la structure. L’écoute cherche à accroitre la validité des apprentissages, valorise l’improvisation, invente, détecte les signaux faibles, complexifie, rebondit, et oriente l’attention sur les conséquences de l’action et sur les relations interpersonnelles.L’hypothèse centrale de cette recherche est que la gestion de ces exigences contradictoires est une source majeure de haute fiabilité. Son design se base sur la comparaison de deux territoires (l’Ouest américain et le sud de la France), et combine plusieurs méthodes : l’observation directe des opérations de secours, l’observation des sessions d’entrainement, et des formations, ainsi qu’une expérimentation sur la plateforme de simulation de la Sécurité Civile françaiseThe frequency and impact of large wildland fires have been increasing for the past 20 years, due to the conjunction of three long term trends: global warming, growing wildland-urban interface and increase in biomass. As a result, enhancing organizational reliability in Incident Management Teams is becoming increasingly important. Examining how firefighters face large disasters is also relevant for organization studies because these situations offer a perspective on organizing and sensemaking. Indeed, firefighters are under conflicting organizational requirements: stabilizing the sense of situations for effective collective action (control processes) and reassessing situations to detect and adapt to unexpected changes (mindful processes). Control focuses on lessons learned, capitalizes on success, ignores noise, simplifies, values anticipation and direct attention on plans and strategies. Mindfulness focuses on improvising, detects weak signals, is reluctant to simplify, values resilience and interpersonal relationships.The central hypothesis of this research is that the successful management of these opposite requirements is an important source of operational reliability. The research is based on a comparison between two territories (the American West and Southern France) and combines several methods: direct observation of firefighting operations, direct observation of Incident Management Teams trainings, the analysis of available archival data, as well as controlled experiments on a France’s Civil Protection simulation training platform
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New, Karl James. "Exercise, arterial pressure control & systemic O₂ tension : implications for post exercise hypotension in hypertension." Thesis, University of South Wales, 2008. https://pure.southwales.ac.uk/en/studentthesis/exercise-arterial-pressure-control--systemic-o2-tension(b1d2c65b-00ef-429c-9afd-7c0452f13dbb).html.
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This thesis presents four studies investigating the phenomenon of post exercise hypotension in the human condition of pre (borderline)-hypertension. Study one investigated the effects of an acute bout of 30-minutes upright cycling on post exercise haemodynamics and compared the results to a non-exercise control condition. 9 pre-hypertensive males, mean arterial pressure (MAP) = 106 ± 5 mmHg (50 ± 10 yr), not on medication, were studied for 6 hours following 30-minutes of cycle exercise at 70% maximal oxygen consumption and following 30-minutes of seated rest. Results demonstrate that moderate intensity exercise exerts a modest fall (~6 mmHg) in arterial pressure with the hypotension sustained for 6-hours post exercise. The fall in arterial pressure equates to a significantly reduced after load when compared to both pre-exercise baseline and non-exercise control data taken at the same time of day. The arterial pressure responses transcended into a sustained reduction (20%) in systemic vascular resistance and reciprocal increase in vascular conductance for up to 2-hours post-exercise. Venous atrial natriuretic peptide (ANP) demonstrated an elevation (44%) following exercise and a significant decline (33%) in the post-exercise period mirroring the haemodynamic response. This research reveals that acute exercise is capable of sustained reductions in arterial pressure and vascular resistance beyond the usual labile fluctuations and that the octapeptide ANP may exert a modulatory influence over the post-exercise response. Increases in 02 tension beyond the physiological range induces complex effects on the circulatory system with a dominant vasoconstriction following hyperoxia. The purpose of study 2 was to assess the effects of hypoxic (16% 02) and hyperoxic (50% 62) exercise on subsequent haemodynamic control when compared with normoxia. 9 pre-hypertensive males, MAP = 106 ± 5 mmHg (50 ±10 yr), not on medication, performed 30-minutes of cycle exercise at 70% normoxic maximal oxygen consumption in hypoxia (16% O 2 ), hyperoxia (50% O 2) and normoxia(21% O2 ). Hyperoxic exercise blunted post-exercise haemodynamics by significantly attenuating the reductions (from normoxic baseline) in SVR (-45%, PO.05 vs. normoxic & hypoxic exercise immediately post-exercise) that persisted throughout 120-minutes recovery in normoxia (-35% vs. normoxic & hypoxic exercise, during recovery) and elicited a mildly hypertensive effect, with regards to MAP, whereas normoxic and hypoxic exercise elicited a hypotension compared to baseline (P < 0.05). Circulating ANP was decreased in the hyperoxic trial when compared with normoxic and hypoxic exercise [24.3 (13.4) v. 31.5 (16.3) and 29.6 (13.9) pg/ml, respectively; P < 0.05, pooled for state]. Changes in MAP were related to changes in ANP concentration only following hyperoxic exercise (r = 0.50, P < 0.01). These findings indicate that acute modest hyperoxia reflexively induces measurable physiological derangement partly explained by decreased circulating concentrations of ANP. Study three determined the role of free-radical mediated oxidative stress and redox regulation of circulating NO metabolism as a primary modulator of vascular tone following exercise in pre-hypertensive humans. Utilising the same cohort and exercise protocol as in study 1 venous blood was sampled from an antecubital vein. Plasma NO metabolites nitrate (NO" 3 ) and nitrite (NO"2 ) were determined fluorometrically, whilst S-Nitrosothiol (RSNO) concentrations were assayed by the Saville reaction Indirect markers of oxidative stress were determined spectrophotometrically detecting lipid hydroperoxides (LOOH). Exercise led to a delayed increase in LOOH by 60- minutes post-exercise (0.69 ± 0.13 v. 0.86 ± 0.18 umol/1, respectively, P < 0.05), that remained elevated until termination of the trial 6-hours post-exercise. NO'a significantly fell below baseline by 120-minutes post-exercise (10.8 ± 3.3 v. 1.1 ±1.1 u.mol/1, respectively, P < 0.05), remaining attenuated for the remainder of the study.NO'i and RSNO were unmodified in the post-exercise period. In parallel to this finding the data also indicates a significant blunting in the hyperaemic response [SVR decreased from a 31% reduction immediately (within 1-minute) post-exercise to -13 and 8% at 60- and 120-minutes post-exercise, respectively, P < 0.05] and reversal of the hypotension (P < 0.05) over the same time frame as the augmented lipid peroxidation and attenuated circulating NO~3. These results indicate that augmented oxidative stress exerts a deleterious effect on post-exercise haemodynamics and implicates a potential redox regulation pathway of NO as being a mechanism by which free radical-induced oxidative stress blunts the degree of PEH in the recovery period. The final study investigated the potential role of a redox-mediated regulation of circulating NO bioavailability as a modulator of the augmented vasoconstriction following hyperoxic exercise. The same cohort and exercise protocol were employed as in study 2 and venous blood was assayed for NO"3 , NO'a, RSNO, LOOK, & lipid /water-soluble antioxidant concentrations. Similar adverse haemodynamic effects were noted following hyperoxic exercise as reported previously in study 2. RSNO showed a significant increase following hypoxic exercise only (P < Q.Q5, state x time, interaction), whereas NO~3, NO~2 and LOOH failed to differ between conditions (P > 0.05, main effect for state [02] and state x time, interaction effects). Ascorbic acid was mobilised in response to hyperoxic exercise when compared to normoxia (P < 0.05, main effect for state [O2] and state x time, interaction effects) being significantly elevated by 120-minutes post-exercise in hyperoxia compared to normoxia and hypoxia [75.1 (31) v. 39.5 (18.3) v. 46.7 (14.2) |amol/l, respectively, P < 0.05]. This data demonstrates an effective endogenous antioxidant response and argues against a redox regulation pathway of NO metabolism as a primary mediator of blunted vasodilatation in this scenario. This elucidates a more complex regulation of arterial tone, resulting from a metabolic pathway independent of NO in older subjects with pre-hypertension. This work demonstrates that (1) aerobic exercise exerts a hypotensive effect in humans with pre-hypertension, (2) ANP plays a part in the vasodilatation following exercise, (3) Free-radical mediated oxidative stress & subsequent modulation of NO metabolism exerts a deleterious influence on post-exercise haemodynamics (4) Acute hyperoxic exercise induces a sustained vasoconstriction that is mediated via circulating ANP concentration but not by redox regulation of NO metabolism.
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Shankam, Narayana Vivek Prasad. "A Novel Method for Dynamic Yarn Tension Measurement and Control in Direct Cabling Process." NCSU, 2005. http://www.lib.ncsu.edu/theses/available/etd-12142005-110719/unrestricted/etd.pdf.
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Freyer, Burkhard Heinrich. "Gauge and tension control during the acceleration phase of a steckel hot rolling mill." Diss., University of Pretoria, 2002. http://hdl.handle.net/2263/24580.
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Please read the abstract in the section, 00front of this documentDissertation (M Eng (Electronic Engineering))--University of Pretoria, 2002.
Electrical, Electronic and Computer Engineering
MEng
unrestricted
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Gao, Guangyue. "Some Controllability and Stabilization Problems of Surface Waves on Water with Surface tension." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/64377.
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The thesis consists of two parts. The first part discusses the initial value problem of a fifth-order Korteweg-de Vries type of equation
wt + wxxx - wxxxxx - n∑j=1 ajwjwx = 0, w(x, 0) = w0(x)
posed on a periodic domain x ∈ [0, 2π] with boundary conditions wix(0, t) = wix(2π, t), i = 0, 2, 3, 4 and an L2-stabilizing feedback control law wx(2π, t) = αwx(0, t) + (1 - α)wxxx(0; t) where n is a fixed positive integer, aj, j = 1, 2, ... n, α are real constants, and |α| < 1. It is shown that for w0(x) ∈ H1α(0, 2π) with the boundary conditions described above, the problem is locally well-posed for w ∈ C([0, T]; H1α(0, 2π)) with a conserved volume of w, [w] = ∫2π0 w(x, t)dx. Moreover, the solution with small initial condition exists globally and approaches to [w0(x)]/(2π) as t → + ∞. The second part concerns wave motions on water in a rectangular basin with a wave generator mounted on a side wall. The linear governing equations are used and it is assumed that the surface tension on the free surface is not zero. Two types of generators are considered, flexible and rigid. For the flexible case, it is shown that the system is exactly controllable. For the rigid case, the system is not exactly controllable in a finite-time interval. However, it is approximately controllable. The stability problem of the system with the rigid generator controlled by a static feedback is also studied and it is proved that the system is strongly stable for this case.Ph. D.
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Schnupp, Keith Otto. "Effects of Head Size on the Performance of Twist-Off Bolts." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/43600.
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This study examines a specific application of button-head type twist-off bolts. Currently, the Research Council on Structural Connections Specification (2000) removes the requirement for ASTM F436 washers (ASTM 2000a) under the bolt head of twist-off bolts where the head diameter equals or exceeds that of an ASTM F436 washer when oversized and slotted holes are used. The need for washers is also removed for A490 strength bolts used on steels with specified yield strengths less than 40 ksi provided that the head diameter equals or exceeds an ASTM F436 washer.
The ASTM F1852 Specification (ASTM 2000b) allows for head diameter dimensions that are slightly smaller than an ASTM F436 washer. Following the RCSC Specification, manufacturers that produce bolts using the ASTM F1852 dimensions are required to use ASTM F436 washers under the bolt head. The discrepancies between the specifications lead to this study, which involved the testing of button-head type twist-off bolts with two different head diameters, both of which were smaller than an ASTM F436 washer.
Five bolt diameters between 5/8 in and 1-1/8 in. were tested in standard, oversized, and long-slotted holes. The performance of the twist-off bolts was determined by measuring and comparing the achieved relaxed pretension force in the bolt after tightening. It was found that twist-off bolts with head diameters less than an ASTM F436 washer had no trouble attaining their required minimum pretension force. Bolt head diameter and hole size were found to have no significant influence on the pretension force that was achieved for all bolts tested.Master of Science
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Stairs, Mary E. "Dialectic tension of emancipation and control in staff/client interaction at shelters for battered women." Virtual Press, 1996. http://liblink.bsu.edu/uhtbin/catkey/1020184.
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This study investigates the dialectic of emancipation and control in the relationship between staff and clients at shelters for battered women. The dialectic of emancipation and control represents the tension shelter workers feel in trying to empower their clients while, at the same time, maintaining control over the programs and domestic order of the shelter. Past research has introduced this dialectic, but no studies exist which view it in the context of the staff/client relationship. Additionally, very little communication research exists exploring the interaction that takes place in shelters for battered women.Four employees of four different shelters were interviewed by this researcher. Their accounts were recorded, transcribed, and analyzed using the constant comparative review method consistent with grounded theory. The workers' accounts indicated that the nature of their profession requires them to be dominant over their clients in five areas. Additionally, the workers discussed four contradictory aspects of their work which reflect the existence of the dialectic of emancipation and control in their interaction with clients.Department of Speech Communication
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CARAVITA, Andrea. "Macchine per il converting: funzionalità e implementazione di tecniche di controllo." Doctoral thesis, Università degli studi di Bergamo, 2012. http://hdl.handle.net/10446/26698.
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The functionalities of Converting machines and the related techniques to control the production process remain at the center of this work, carried out in collaboration with the company IMS Deltamatic SpA, that needed to renew the electrical drive systems in order to create a new standard to be implemented on all machines produced. Working systematically within the industrial framework, the principle of operation of machines - consisting briefly in the transformation of webs wound on reels - was analyzed to detect the control parameters which allow to obtain optimal products. The way is to make an accurate web tension control, which is obtained by implementing the specific winder functions in the control systems of electrical drives. In particular two configurations were examined: in the first one the management of drives is provided by a PLC; the second one is characterized by the introduction of a system dedicated to motion control. The projects have been tested and validated by commissioning the orders of the company, getting an acceptable operation of the machine with either configuration. Tests revealed also the differences of the two systems: the higher performance of the new controller, compared to the PLC, allows to perform more effective regulations, a faster update of the speed reference and a more correct torque compensation. These advantages result in a better tension control in all phases of operation of the machine, in particular during critical situations. In consequence of the greater complexity in designing and programming the device dedicated to motion control, the company has considered valid both solutions, deciding to choose, for each next order, the most suitable configuration for the required performance.
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Terrazas, Mallea Ronald. "Thermocapillary micromanipulation : laser-induced convective flows towards controlled handling of particles at the free surface." Doctoral thesis, Universite Libre de Bruxelles, 2017. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/262343.
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EN: There is an industrial need for new technologies that can manipulate objects in the micrometric scale (1-1000 μm). In this thesis, an original non-contact actuation technique for the manipulation of microscale objects is proposed. The proposal is to use laser-induced thermocapillary convective flows to manipulate particles at the fluid/gas interface. These flows are generated when a surface tension stress is generated at the fluid/gas interface due to a thermal gradient. Laser heating is used because the generated thermal gradients produce fast, localized flows that improve the actuation performance. The particles are manipulated at the interface because the flow generated there is the fastest in the entire fluid. To ensure the precise positioning of a particle, closed-loop controllers are implemented in the system which are designed based on models proposed for the system. Experimental tests are performed that show that positioning precision can be ensured. In addition, the interaction forces between particles have been studied which is a preliminary step towards parallel manipulation. To counteract those forces during the manipulation, a different control strategy has been proposed, implemented and tested using simulations. Overall, the results obtained are comparable to the ones obtained with the other techniques. Therefore, the proposed technique can be considered as an attractive alternative that offers different advantages and disadvantages. FR: Il existe un besoin industriel croissant de nouvelles technologies capables de manipuler des objets à l’échelle micrométrique (1-1000 μm). Dans cette thèse, une technique originale d’actionnement sans contact pour la manipulation d’objets à l’échelle micrométrique est proposée. Elle est basée sur les écoulements thermocapillaires convectifs induits par un laser pour manipuler des particules à l’interface fluide/gaz. Le laser chauffe localement la surface de l’eau, ce qui induit un gradient de tension de surface. Ce gradient génère un écoulement fluidique. Ces écoulements sont rapides et localisés, ce qui confère des performances intéressantes à cette technique d’actionnement. Les particules sont manipulées à l’interface fluide/gaz, où l’écoulement généré est le plus rapide.Pour assurer le positionnement précis d’une particule, des contrôleurs en boucle fermée sont implémentés dans le système. Ils sont basés sur les modèles développés dans cette thèse. Des essais expérimentaux montrent que le positionnement précis de particules peut être assuré. De plus, les forces d’interaction entre des particules placées à l’interface ont été étudiées, et une stratégie de contrôle a été proposée, en vue de la manipulation en parallèle de plusieurs particules. Tant les études analytiques et les simulations numériques que les tests expérimentaux soulignent l’intérêt des écoulements thermocapillaires convectifs pour la manipulation contrôlée d’objets micrométriques. Cette technique est donc une alternative prometteuse aux approches classiques d’actionnement sans contact.Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
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Wright, Ian C. "The design of a yarn tension control system for the high speed formation of conical packages." Thesis, Loughborough University, 1990. https://dspace.lboro.ac.uk/2134/13630.
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The research described was primarily concerned with working towards the solution of the problem of yarn tension control when building conical packages on an open-end spinning machine at yarn delivery speeds of 500 m1min"cause of the total lack of published work on the mathematical modelling of the parameters affecting tension variation, a considerable amount of effort was spent in the establishment of this basic understanding. This mathematical analysis appears, in the main, in the appendices to this thesis. In addition to the analysis of yarn tension variations depending on machine geometry parameters, mathematical models have also been produced which predict the effect on tension of fitting curved distribution bars of various shapes. The work includes the development of concept ideas which appeared capable of providing routes for solution of the tension control problem. These ideas were evaluated and compared against a design specification which was also developed as part of this research. Two promising concepts were selected for detailed investigation. These were: a pneumatic passive compensator and, a positive mechanical compensator. The pneumatic compensator was a novel idea which was conceived by the author, and which eventually provided a solution which met the design specification in every way. The mechanical compensator was shown to be a far less attractive concept with several serious problems which have been explored but not eliminated. A preliminary investigation of a third concept involving microprocessor control was not sufficiently well developed at the time of publication to be included in this thesis.
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Steckler, Pierre-Baptiste. "Contribution à la conversion AC/DC en Haute Tension." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI075.
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Le courant alternatif (AC) se prêtant bien à la majorité des problématiques de production, de transport et de distribution de l'électricité, on comprend qu'il soit massivement utilisé. Cependant, depuis plus d'un siècle, les bénéfices du courant continu haute tension (HVDC, pour High Voltage Direct Current) pour les longues distances sont bien connus. Aux interfaces, des convertisseurs AC/DC sont requis, leur composition évoluant au fil des avancées technologiques. Après avoir présenté les spécificités du HVDC et les contraintes qu'il introduit sur les convertisseurs AC/DC, ce manuscrit se focalise sur trois topologies : Modular Multilevel Converter (MMC), Alternate Arm Converter (AAC) et Series Bridge Converter (SBC). Elles sont présentées, dimensionnées et analysées en détail, puis comparées de façon quantitative en utilisant des indicateurs de performance originaux. Il en ressort que le MMC et le SBC sont particulièrement intéressants. La méthode de commande conventionnelle du MMC est ensuite présentée et ses propriétés structurelles sont mises en évidence. Une première loi de commande originale est présentée, avec des performances similaires mais une complexité inférieure à l'état de l'art. La seconde est non linéaire, basée sur la théorie de la platitude différentielle, et permet un suivi de puissance très rapide tout en assurant la stabilité exponentielle globale du système. Ces lois de commande sont évaluées en simulation, avec un modèle moyen et un modèle détaillé intégrant 180 sous-modules par bras. La dernière partie concerne le SBC. Après l'avoir modélisé, des résultats concernant une analyse structurelle de la topologie sont présentés ainsi qu'une loi de commande originale. Le rôle fondamental du transformateur pour les convertisseurs à structure série comme le SBC est souligné. Enfin, les performances de la loi de commande proposée sont testées en simulationAs Alternating Current (AC) is well suited for most of the production, transmission, and distribution applications, its massive use is easy to understand. However, for over a century, the benefits of High Voltage Direct Current (HVDC) for long-distance energy transmission are well known. To connect both, AC/DC converters are mandatory, whose nature evolves with technological progress. After the problematic induced by HVDC on AC/DC converters is presented, this manuscript is focused on three topologies: Modular Multilevel Converter (MMC), Alternate Arm Converter (AAC) and Series Bridge Converter (SBC). They are presented, sized, analyzed thoroughly, and compared in quantitative terms, using original key performance indicators. It appears that MMC and SBC are particularly promising. The conventional control method of the MMC is then presented, and its structural properties are highlighted. A first original control law is presented, with similar performances but less complexity than the state-of-the-art. A second control law, non-linear and based on differential flatness theory, is introduced. It allows a very fast power tracking response while ensuring the global exponential stability of the system. These control laws are tested in simulation, using an average model and a detailed model with 180 sub-modules per arm. The last part is dedicated to the SBC. After a modeling step, some results regarding its structural analysis are presented, and an original control law is introduced. The essential role of the transformer for series converters like the SBC is highlighted. Finally, the performance of the proposed control law is assessed in simulation
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David, Alain. "Insensibilisation des convertisseurs de fréquence aux creux et coupures de tension." Cachan, Ecole normale supérieure, 1993. http://www.theses.fr/1993DENS0009.
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Les convertisseurs de fréquence pour machine asynchrone sont en fort développement depuis une dizaine d'années. Cette structure s'avère cependant très sensible aux creux et coupures brèves de tension du réseau d'alimentation. Ces perturbations peuvent occasionner une perte de contrôle du convertisseur, entrainant, le plus souvent, un arrêt total du système, avec un redémarrage rarement automatique de l'équipement au retour de l'alimentation. Ces arrêts impromptus sont problématiques et couteux pour beaucoup d'applications industrielles. De nouvelles stratégies de commande du convertisseur pour palier à ce problème sont proposées dans cette thèse. Un modèle de l'ensemble convertisseur de fréquence-machine asynchrone est développé en régime transitoire en supposant une tension d'alimentation quelconque. Les effets des perturbations réseau sur le système sont ensuite étudies. Plusieurs techniques d'insensibilisation sont ensuite proposées: a) une régulation du système pour compenser les effets des creux de tension, b) une identification de la vitesse de la machine en roue libre (nécessaire pour un rattrapage au vol après une coupure brève triphasée), c) une technique de rattrapage au vol basée sur une synchronisation du convertisseur sur les tensions résiduelles générées par le flux rémanent de la machine, d) une régulation a glissement nul assurant le maintien du synchronisme entre le convertisseur et la machine lors de coupures brèves triphasées. Ces techniques ont été validées sur simulations numériques et sur un banc d'essais de 7. 5 kw, avec des performances satisfaisantes: contrôle permanent du système, minimisation des chutes de vitesse, redémarrage automatique du système au retour de la tension normale sans surcourant ou à-coup de couple. L'ensemble des résultats et les performances des commandes sont étudies d'un point de vue théorique sur la base du modèle développé
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Raul, Pramod Rajaram. "Design and analysis of feedback and feedforward control systems for web tension in Roll-to-Roll manufacturing." Thesis, Oklahoma State University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10139848.
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In Roll-to-Roll (R2R) manufacturing, efficient transport of flexible materials (webs) on rollers requires simultaneous control of web speed and tension. Webs experience disturbing forces during transport due to nonideal machine elements and processes such as printing, coating, lamination, etc. Since rotating machine elements are employed, these disturbances are in the form of periodic oscillations in web tension and speed. Design of efficient model-based web tension and speed control systems employing both feedback and feedforward actions that can adapt to changes in parameters and reject periodic disturbances were investigated in this research. Tools from adaptive and robust control theory and singular perturbation method were utilized for the design and analysis of these control systems.
Model reference and relay feedback based adaptive Proportional-Integral (PI) tension control schemes were developed to regulate web tension; these schemes overcome the tedious tuning procedures required for fixed gain PI schemes when process parameters and conditions change. To directly control the roll speed when belt-pulley and gear transmissions are employed, a control scheme that uses both motor and load speed feedback is developed. In the presence of a compliant transmission system, it is shown that using pure load speed feedback must be avoided as it results in an unstable system. In situations where linearization of the nonlinear web tension governing equation is not possible due to changes in operating conditions, a nonlinear tension regulator is designed via a solution method employed in the nonlinear servomechanism problem. The feedforward action is synthesized by considering a discretized form of the tension governing equation in conjunction with adaptive estimation of periodic disturbance parameters. It is also shown that interaction between different subsystems of the R2R system may be minimized by employing feedforward action. The strategy of utilizing tension signal from the web tension zone downstream of the driven roller is shown to result in minimization of propagation of disturbances into further downstream tension zones. For each of the developed designs, experiments were conducted on a large R2R platform for different web materials and transport conditions to evaluate and compare their performance. Implementation guidelines are provided for ease of applying the designs to other industrial R2R machines.
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Dai, Jing. "Frequency control coordination among non-synchronous AC areas connected by a multi-terminal HVDC grid." Phd thesis, Supélec, 2011. http://tel.archives-ouvertes.fr/tel-00783519.
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This thesis addresses the problem of frequency control in a power system composed of several non-synchronous AC areas connected by a multi-terminal HVDC grid. For this system, we propose three control schemes, two for primary frequency control and one for secondary frequency control. Based on remote measurements of the other areas' frequencies, the first control scheme modifies the power injections from the different AC areas into the DC grid so as to make the system collectively react to load imbalances. This collective reaction allows each individual AC area to downscale its primary reserves. The second control scheme has the same objective with the first one, but acts on the DC voltages of the HVDC converters. In particular, it modifies the DC voltage of each converter based on the frequency deviation of the AC area it is connected to. The last control scheme aims at restoring the frequencies and the power exchanges to their nominal or scheduled values in the aftermath of a power imbalance. It can be combined with the other two control schemes. Theoretical studies reveal the stability properties of the three control schemes. Simulation results on a benchmark power system with five AC areas confirm their good performance.
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Peng, Ling. "Reconfiguration du dispositif de commande d’une éolienne en cas de creux de tension." Thesis, Ecole centrale de Lille, 2010. http://www.theses.fr/2010ECLI0005/document.
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Avec le développement de l’éolien, les prescriptions techniques de raccordement de cette technologie obligeront le maintient de sa connexion lors d’incidents sur la tension du réseau électrique. L’enjeu pour le gestionnaire du réseau est de pouvoir utiliser tous les générateurs pour garantir la stabilité du système électrique.A partir d’un modèle dynamique d’une éolienne à base de Machine Asynchrone à Double Alimentation (MADA), une commande vectorielle améliorée a été proposée en prenant en compte la dynamique du flux statorique engendrée par la chute de tension. Les performances supérieures en terme de maintient de la production ont été établies par comparaison avec la méthode de commande classique. Son domaine d’utilisation a été également déterminé.Pendant les creux de tension importants, une protection matérielle (crowbar) est implémentée avec un contrôle de la démagnétisation de la MADA. En outre, de la puissance réactive peut être produite à la fois par la MADA et par le convertisseur connecté au réseau électrique au cours de la défaillance du réseau.Un contrôle vectoriel à hystérésis des courants pour les deux convertisseurs électroniques multiniveaux est proposé et évalué pour améliorer la réponse dynamique de ces convertisseurs et pour réduire les effets des variations des paramètres sur les performances de la commande. Selon la durée du défaut, des objectifs différents de contrôle doivent être réalisés en priorité pour empêcher des surintensités rotoriques et pour fournir de la puissance réactive. Une reconfiguration complète du dispositif de commande de cette éolienne est détaillée pour renforcer le maintient de la production éolienne lors de défaillancesWith the massive development of wind energy, the technical requirements for connecting this technology will require the improvement of the fault ride-through capability of grid-connected wind turbines. The task for the grid system operator is to use all generators to ensure the stability of the electrical system.From a dynamic model of a Doubly Fed Induction Generator (DFIG) based wind generator, an improved vector control has been proposed by taking into account the dynamics of the magnetic flux, which are generated by the voltage dip. The higher performances have been established by comparison with the conventional control method. The operation domain was also determined.During serious voltage dips, a hysteresis control scheme of the active Crowbar is proposed to protect the system within a demagnetization method of the DFIG. Moreover, additional reactive power can be produced both by the MADA and the grid-side converter in order to support the electric network during the grid fault.A space vector hysteresis current control strategy of both three-level converters is proposed to improve the dynamic response of the system and to reduce the parameter variation effects on the control performanceDepending on the grid fault duration, different control objectives have to be achieved with priority to restrain the rotor over-current or to supply reactive power. Then the reconfiguration scheme of the control strategies of high power DFIG wind turbine system is proposed to enhance the fault ride-through capability of the DFIG system. With this specific methodology, the DFIG can stay connected and can supply maximal reactive current during voltage dips to help voltage recovery
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Casciaro, Francesca <1991>. "Role of nuclear redox control, intra-population heterogeneity and oxygen tension in human amniotic fluid stem cells aging." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amsdottorato.unibo.it/9125/1/tesifrancescacasciaro.pdf.
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Amniotic fluid stem cells (hAFSC) are emerging as a potential therapeutic approach for various disorders. The low number of available hAFSC requires their ex vivo expansion prior to clinical use, however, during their in vitro culture, hAFSC quickly reach replicative senescence.
The principal aim of this study was to investigate the aging process occurring during in vitro expansion of hAFSC, focusing on the redox control that has been reported to be affected in premature and physiological aging.
My results show that a strong heterogeneity is present among samples that reflects their different behaviour in culture. I identified three proteins, namely Nox4, prelamin A and PML, which expression increases during hAFSC aging process and could be used as new biomarkers to screen the samples. Furthermore, I found that Nox4 degradation is regulated by sumoylation via proteasome and involves interactions with PML bodies and prelamin A.
Since various studies revealed that donor-dependent differences could be explained by cell-to-cell variation within each patient, I studied in deep this phenomenon.
I showed that the heterogeneity among samples is also accompanied by a strong intra-population heterogeneity. Separation of hAFSC subpopulations from the same donor, using Celector® technology, showed that an enrichment in the last eluted fraction could improve hAFSC application in regenerative medicine.
One of the other problems is that nowadays hAFSC are expanded under atmospheric O2 concentration, which is higher than the O2 tension in their natural niches. This higher O2 concentration might cause environmental stress to the in vitro cultured hAFSCs and accelerate their aging process.
Here, I showed that prolonged low oxygen tension exposure preserves different hAFSC stemness properties.
In conclusion, my study pointed different approaches to improve in vitro hAFSC expansion and manipulation with the purpose to land at stem cell therapy.
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Pramono, Hadi Sasongko. "Etude et réalisation de régulateurs adaptatifs numériques de tension et de vitesse d'un groupe turbo-alternateur." Grenoble INPG, 1988. http://www.theses.fr/1988INPG0052.
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Cette thèse décrit l'étude et la réalisation d'un régulateur numérique de groupe turbo alternateur dont les paramètres varient en fonction du point de fonctionnement de la machine. D'abord, une étude comparative d'application de la commande adaptative aux groupes de production est présentée. Les méthodes de commande adaptative comportant le schéma, la stratégie, le type et le nombre de variables sont analysées dans la suite de façon à trouver la plus convenable. Ensuite, est présentée l'étude théorique de la conception de régulateurs adaptatifs modal et optimal. Les performances des régulateurs proposés sont décrites par simulation numérique et par l'implantation sur un modèle dynamique du réseau construit autour d'un micro alternateur et commandé par un microprocesseur. Enfin, la conclusion comporte l'analyse des résultats obtenus avec les avantages et les inconvénients ainsi que les propositions pour la poursuite de cette étude
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Hennan, James Kenneth. "Role of cyclic GMP, cyclic GMP-dependent protein kinase and protein phosphorylation in the control of smooth muscle tension." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0017/NQ56558.pdf.
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Abdi, Arash. "Control of Quad-copter with suspended load." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16490/.
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A Quadrotor (QR) is a type of unmanned aerial vehicles which has been absorbed lots of attention recently with many institutes have investigated on many application with this tools include search and rescue, surveillance, supply of food and medicine in emergency sub-problem of load transportation by the control of the cable suspended load or directly control of the QR robustly.
The goal of this thesis is to present a nonlinear control approach and investigate on novel approach. The focus is lies on the quadrotor-load subsystem where the cable tension is not zero, which analogous to modeling a rigid link between the quadrotor and load.
After introducing the basic concept, an introduction is given on geometric mechanics. This differential geometric based approach is used to model and control the system, based on the geometric properties of the system dynamics. It is shown how the configuration spaces and analyzed with the principles of differential geometry. Also the common approach for second approach will be hired for illustrate the configuration of the Quadrotor-load, while both approach avoiding the problem of singularities would occur on local charts.
Next, the geometric properties are utilized to define tracking error functions on these same space. A back-stepping approach is applied to generate a cascade structure with multiple nonlinear geometric controllers, allowing control of several flight modes that are responsible for the control of a) quadrotor attitude b) load attitude c) load position.
Finally, simulation illustrate the stability and ability of the geometric controller. Also Zero-dynamics is derived to compare both performances. The tracking performances of both controllers are discussed for many different experiences.
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Růžička, Kamil. "Řízení tahových sekcí podélné řezačky." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-316376.
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This diploma thesis deals with the control of unwinding and winding tension sections on the slitter rewinder for packaging material. The essay was created in collaboration with SOMA company, which provided a machine for testing and measuring. The theoretical part describes the function of bitter rewinder, possible mechanical approaches of control the tension sections, and real mechanics of control on our machine. The next part explores selected hardware and its use on the rewinder. Further chapters are focused on the individual measuring chains, calibration, computations of required quantities and control algorithms. The last part compares the theoretical and measured values and evaluates the results of this essay.
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Abouda, Salim. "Contribution à la commande des systèmes photovoltaiques : application aux systèmes de pompages." Thesis, Reims, 2015. http://www.theses.fr/2015REIMS005/document.
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L'objectif des travaux présentés dans cette thèse est d'apporter une contribution à l'étude d'un système photovoltaïque fonctionnant à sa puissance maximale et énergétiquement autonome. Le cas étudié, dans cette thèse, concerne la commande d'une chaine de pompage photovoltaïque dans un site isolé. Dans ce sens, et pour que le système photovoltaïque fonctionne à sa puissance maximale, il doit comporter un étage d'adaptation associé à un algorithme MPPT. Dans notre étude, nous avons utilisé deux algorithmes MPPT, l'algorithme “Perturb and Observe” (P&O) puis l'algorithme “ Increment of Conductance” (IncCond). Dans quelques applications industrielles, il est parfois nécessaire de maintenir la tension délivrée par le système photovoltaïque constante. Pour cela, un système de contrôle de cette tension est présenté. Les méthodes utilisées pour la simulation de ce système sont basées sur l'utilisation d'un régulateur PID, puis sur le contrôle par mode glissant, et enfin sur un contrôleur par logique floue. Ce système est testé pour une charge résistive puis pour le cas d'une pompe centrifuge entrainée par un moteur à courant continu à aimant permanent. Ensuite, nous avons étudié le cas d'une chaine de pompage utilisant un moteur asynchrone triphasé comme moteur d'entrainement. Dans le but d'avoir la possibilité de régler le débit d'eau, et en se basant sur la caractéristique de proportionnalité entre la vitesse et le débit, la méthode de contrôle direct du couple, Direct Torque Control - DTC est utilisée pour la commande de la vitesse du moteur asynchroneThe aim of the work presented in this thesis is to contribute to the study of a photovoltaic system operating at its maximum power and energetically autonomous. The case studied in this thesis relates to the control of a chain of photovoltaic pumping in an isolated site. In this sense and for the PV system operates at its maximum power, it must include a converter associated with a MPPT algorithm. In our study, we used two MPPT algorithms, the algorithm “Perturb and Observe” (P & O), then the algorithm “Increment of Conductance” (IncCond). In some industrial applications, it is sometimes necessary to maintain the voltage delivered by the PV system constant. For this, a control system of this voltage is presented. The methods used for the simulation of this system are based on the use of a PID controller and the sliding mode control, and finally a fuzzy logic controller. This system was tested for a resistive load then for the case of a centrifugal pump driven by a permanent magnetic DC motor. Then we studied the case of a pumping chain using a three-phase induction motor as a drive motor. In order to be able to regulate the flow of water, the Direct Torque Control method “DTC” is used to control the speed of the induction motor because it is proportional with the water flow
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Lorenzen, Michael E. "A balancing act: Managing the tension between competitive outcomes and educational development in collegiate athletics." Scholarly Commons, 2010. https://scholarlycommons.pacific.edu/uop_etds/2418.
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Student-athletes have the opportunity for significant development that can enhance their undergraduate experience through participation in intercollegiate athletics. The commercial and cultural influence of professional sports has, however, increasingly challenged the efforts of the National Collegiate Athletic Association (NCAA) to maintain a developmental focus. Some college sports, particularly football and men's basketball, are now relied upon to generate revenue, which requires successful outcomes and accountability to commercial interests. The disproportionate influence of those revenue sports on Division I athletic culture challenges the credibility of all collegiate sports as appropriate components of higher education. This case study examines the women's gymnastics team at a large Division I institution, Big State University (BSU), over the course of the 2010 season. BSU Gymnastics has achieved sufficient competitive success that the coaches were subject to similar pressure to that which their football and basketball colleagues experienced. The study is a qualitative investigation of the leadership and mentoring practices of the coaching staff, particularly in regard to their ability to maintain a focus on student-athlete development in the face of external pressure from various stakeholders to prioritize winning. Using control systems theory and a new typology of sport, the researcher interviewed coaches and student-athletes, analyzed BSU's 2010 season, and found that the coaches consistently prioritized the developmental experience of their student-athletes. A significant additional finding of the study is that coaches play a critical buffering role, sheltering student-athletes from influences that might otherwise undermine the beneficial aspects of intercollegiate athletics participation.
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Dörrich, Matthea. "Book Consumption in Convergence Culture : An Exploratory Audience Study of Media Repertoires of Book Consumption in the Tension between Participation and Corporate Control." Thesis, Stockholms universitet, Institutionen för mediestudier, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-107235.
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Book consumption is no longer only a solitary practice of one person sitting in an armchair with a bound volume of their favorite novel or the latest paperback bestseller. Books have become part of what Henry Jenkins has termed convergence culture. Books are no longer just books, they are also adapted into films, they are available as audiobooks and e-books, they are accompanied by websites, author blogs, and dedicated Facebook pages, they are continued by fans writing their own stories based on the original, they are discussed in online forums and communities, and they are being reviewed in Youtube videos, to just name a few. Convergence culture refers to the spread of content over different platforms and devices, the conglomeration of media companies on the production side, and the new possibilities for participation on the side of consumers. Media and communication studies have curiously neglected book consumption in its re-examination of audience studies in the light of convergence. This study assumes that audience studies, redefined to account for cross-media use and active as well as passive aspects of consumption, are well suited to investigate contemporary book consumption. The aim of this study is to explore media use surrounding books in the broad sense described above. It also investigates how commercial structures on the one hand and participation on the other shape book consumption. To do so, this study exemplarily analyzes the book related media use of members of an online reading community (Lovelybooks). Methodologically this study follows a mixed-methods approach by adopting the concept of media repertoires. Media repertoires describe patterns of habitual media use, thus integrating the quantitative mapping of media use with the analysis of the meaningful principles behind it. The results from a survey that was distributed to Lovelybooks’ members describe which media components are used, how they are combined and to what extent they are participatory. Semi-structured interviews complement the survey results by exploring which influence commercial structures and the attitudes towards them have on Lovelybooks members’ participatory media use. The interpretation is informed by critical political economy, discussing the implications of an online community being commercially owned and run, the consequences of commercial structures for participation, and the appropriation of personal data and labor by corporations.
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Chen, Yijing. "Nonlinear Control and Stability Analysis of Multi-Terminal High Voltage Direct Current Networks." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112041/document.
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Cette thèse a été consacrée à l'étude des réseaux multi-terminaux haute tension à courant continu (MTDC). Les principales contributions étaient dans le domaine du contrôle automatique non linéaire, appliquées aux systèmes électriques, électronique de puissance et les sources d'énergie renouvelables. Le travail de recherche a été lancé avec l'intention de combler certaines lacunes entre la théorie et la pratique, en particulier: 1) d'enquêter sur diverses approches de contrôle pour le but d'améliorer la performance des systèmes MTDC; 2) d'établir des connexions entre la conception du contrôle empiriques existantes et analyse théorique; 3) d'améliorer la compréhension du comportement multi-échelle de temps des systèmes MTDC caractérisés par la présence de transitoires lents et rapides en réponse aux perturbations externes. En conséquence, ce travail de thèse peut être mis en trois domaines, à savoir la conception non linéaire de commande de systèmes MTDC, analyse des comportements dynamiques de système MTDC et l'application de systèmes MTDC pour le contrôle de fréquence des systèmes de climatisationThis dissertation was devoted to the study of multi-terminal high voltage direct current (MTDC) networks. The main contributions were in the field of nonlinear automatic control, applied to power systems, power electronics and renewable energy sources. The research work was started with the intention of filling some gaps between the theory and the practice, in particular: 1) to investigate various control approaches for the purpose of improving the performance of MTDC systems; 2) to establish connections between existing empirical control design and theoretical analysis; 3) to improve the understanding of the multi-time-scale behavior of MTDC systems characterized by the presence of slow and fast transients in response to external disturbances. As a consequence, this thesis work can be put into three areas, namely nonlinear control design of MTDC systems, analysis of MTDC system's dynamic behaviors and application of MTDC systems for frequency control of AC systems
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Al-Shaibie, Mahmoud, and Saima Batool. "The Effects of Tight Budgetary Control on Employee Behavior in the Public Sector of Jordan, Pakistan and Sweden." Thesis, Karlstads universitet, Handelshögskolan, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-34657.
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This thesis aims to explore the effects of tight budgetary control on employee behavior focusing on employee loyalty, employee satisfaction, job related tension and tendency towards data manipulation in public sectors. The study explores the subject on the population of three countries which includes Sweden, Jordan and Pakistan. In Pakistan and Jordan, no previous study has ever been performed which tried to explore effects of tight budgetary control in employee behavior. Method: Keeping the above fact in view, method derived for this study was the combination of qualitative and quantitative approach. Questionnaires were formulated and sent to employees of the sampled companies receiving 740 responses. For qualitative method, 5 employees were interviewed from entire three countries. Finding: the study revealed that all three countries are experiencing tight budgetary control whereas Jordan and Pakistan are experiencing it on higher level and Sweden is experiencing it in lower level as compared to Pakistan and Jordan. As far employee behavior is concerned, both the method proved that loyalty was negatively related to tight budgetary control for Pakistan and Sweden whereas positively related in case of Jordan. Satisfaction is also negatively related to tight budgetary control for Sweden and Pakistan while positively related for Jordan. Job related tension and tendency towards data manipulation are positively related to tight budgetary control for all three countries. Research type: Master’s thesis.
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Cavalcanti, santos João. "Model Predictive Tracking Control of Cable-Driven Parallel Robots : From Concept to Real-Time Validation." Thesis, Montpellier, 2020. http://www.theses.fr/2020MONTS017.
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Cette thèse traite de la commande pour le suivi de position des Robots Parallèles à Câbles (RPCs) dans le cadre du projet Hephaestus (projet européen H2020). L'objectif principal de ce projet est de développer une solution robotique pour l'installation de modules de panneaux vitrés sur les façades de bâtiments. Une exigence primordiale est que le RPC fonctionne en toute sécurité à proximité des contraintes du modèle mathématique du système. Il a été observé que les stratégies de l'état de l'art de commande ne répondent pas à cette exigence car elles ne sont pas en mesure de considérer les contraintes du système comme faisant partie intégrante du contrôleur principal.La commande prédictive étant l'une des rares stratégies de commande capable de gérer explicitement les contraintes du système, cette thèse se concentre sur la conception et l'analyse de schémas de commande prédictive pour la poursuite de trajectoire des RPC. Deux approches sont donc proposées : une commande prédictive linéaire (CPL) et une commande prédictive non linéaire (CPNL).La CPL proposée est basée sur une approximation linéaire du modèle dynamique des RPCs. Les tests expérimentaux ont prouvé que la CPL peut fonctionner en toute sécurité près des contraintes du système. Cette capacité est validée en appliquant une trajectoire désirée qui ne peut être effectuée sans violer les limites de tensions des câbles. Dans ce cas, la CPL proposée est capable d'effectuer un suivi de trajectoire le mieux possible tout en satisfaisant les limites de tensions dans les câbles. En revanche, les schémas existants ne sont pas capables de répondre convenablement dans de telles conditions. La comparaison de comportement entre la CPL linéaire proposée et une commande de l'état de l'art permet de conclure que la capacité à fonctionner à proximité des contraintes du système représente un résultat important lié à la sécurité de fonctionnement des RPC.Néanmoins, il a été noté que la CPL peut être sensible à des non-linéarités significatives. La précision de suivi en position peut notamment se dégrader le long de trajectoires présentant des vitesses relativement élevées. En conséquence, une CPNL capable de prendre en compte les non-linéarités du système est proposée. Contrairement à son homologue linéaire, la stabilité du système en boucle fermée résultant a pu être analysée. Des détails sur sa mise en œuvre numérique sont présentés et l'amélioration des performances est validée par des simulations.Outre la conception de commandes prédictives, cette thèse présente également des contributions liées au modèle cinématique des RPC et à la commande des tensions des câbles. Un algorithme de résolution du modèle géométrique direct prenant en compte la cinématique des poulies est proposé. Une expression explicite de la cinématique a permis la mise en œuvre d'une solution numérique basée sur une méthode de moindres carrés non linéaire. Ses capacités de convergence ont été évaluées expérimentalement et numériquement.Les algorithmes et schémas de commande proposés dans cette thèse ont été implémentés dans un logiciel industriel, ce qui démontre l'applicabilité potentielle des solutions proposées dans des applications commercialesThis thesis addresses the position tracking control of Cable-Driven Parallel Robot (CDPR) within the framework of the European H2020 project named Hephaestus. The main goal of this project is to develop a robotic solution for the installation of curtain wall modules on building facades. An essential requirement is that the CDPR should safely operate close to the system constraints. It was observed that state-of-the-art control schemes do not cope with this requirement. The control strategies used in the design of such schemes are not able to consider system constraints as an integral part of the main controller.Since Model Predictive Control (MPC) is one of the few control strategies able to explicitly handle the system constraints, this thesis is focused on the design and analysis of MPC schemes for position tracking of CDPRs. Two approaches are then proposed: a linear MPC and a nonlinear MPC (NMPC).The proposed linear MPC is based on a linear approximation of the CDPR dynamic model. The Experimental tests proved that the linear MPC may safely operate close to system constraints. This capability is validated by applying a desired trajectory that cannot be performed without violating the cable tension limits. In this case, the proposed linear MPC scheme is able to perform a trajectory tracking as best as possible while satisfying the cable tension bounds. Conversely, state-of-the-art control schemes are not able to suitably respond under such conditions. Comparing the behavior obtained with the proposed linear MPC and a state-of-the-art control scheme, one may conclude that the capability to operate close to the system constraints represents an important result related to the safety of the operation of CDPRs.Nevertheless, it was noted that the proposed linear MPC may be sensitive to increased nonlinearities. The precision of positioning tracking may be deteriorated for trajectories presenting relatively high velocities. Accordingly, an NMPC able to consider the system nonlinearities is proposed. In contrast to its linear counterpart, the stability of the resulting closed-loop system could be analyzed. Details on its numerical implementation are presented and the improved performance is validated through simulations.In addition to the design of MPC control schemes, this thesis also presents contributions related to the kinematic model of CDPRs and the control of cable tensions. A Forward Kinematic (FK) algorithm considering the pulley kinematics is proposed. An explicit expression for the differential kinematics enabled the implementation of a numerical solution of the nonlinear least-squares system representing the FK problem. Its convergence capabilities are evaluated experimentally and numerically.It is worth noting that the algorithms and control schemes proposed in this thesis were implemented in an industrial software, which demonstrates the applicability of the proposed solutions in commercial applications
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He, Yujun. "Contribution au réglage de la tension sur un réseau HTA avec producteurs. Apport de la flexibilité de la demande." Thesis, CentraleSupélec, 2015. http://www.theses.fr/2015SUPL0005/document.
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L’intégration des producteurs décentralisés (DG) dans un réseau de distribution peut modifier le profil de tension et influencer le réglage de tension conventionnel. Pour le bon fonctionnement du réseau, le raccordement des DG ainsi que les charges grosses sont limités par le dimensionnement du réseau. Les travaux de cette thèse ont pour but de proposer une approche du réglage de tension dans un réseau de distribution avec producteur, en appuyant sur la flexibilité de la demande. Les moyens de réglage de tension seront constitués du régleur en charge (OLTC), la régulation de DG ainsi que la demande flexible. Une optimisation centralisée de type MINLP est proposée pour coordonner ces moyens de réglage. Il est montré que si les moyens de l’OLTC et de la puissance réactive ne suffissent pas de lever la contrainte de tension, il faut réduire la puissance active de producteur. Pour le gain de producteur, la demande flexible peut être considérée comme une source active. La modulation de « demand response » (DR) utilisant les charges thermiques est alors proposée au réglage de tension. L’effet de rebond est pris en compte pour les charges thermiques afin de ne pas affecter le profil de tension après l’action de DR. Ces travaux permettent d’envisager un réglage de tension plus active dans le réseau intelligent et augmenter la flexibilité du réseauGrowth of distributed generations (DG) in actual distribution networks will bring voltage issues that cannot be fixed by conventional voltage control means. For the sake of network safety, the size of DG and load in a distribution network is limited by the network parameters. The research described in this thesis aims to propose a voltage control strategy on distribution networks using the flexibility of demand. The voltage control means will consist of the on load tap changer (OLTC), the regulation of DG, and flexible demand. A centralized optimization of MINLP type is proposed to coordinate these voltage control means. It shows if it is not able to remove the voltage constraint with OLTC and reactive power regulation, then it must reduce the active power of DG. In order not to reduce active power of DG, the flexible demand is considered as an active source to take part in voltage control. The demand response (DR) modulation using thermal loads is thus proposed for voltage control. For the thermal load, the cold load pick-up (CLPU) effect must be taken into account in order not to affect the voltage profile after DR action. This work allows us to consider a voltage control strategy more active in smart distribution network and improve the flexibility of network
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Ahmidi, Amir. "Participation de parcs de production éolienne au réglage de la tension et de la puissance réactive dans les réseaux électriques." Phd thesis, Ecole Centrale de Lille, 2010. http://tel.archives-ouvertes.fr/tel-00590371.
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Nous proposons dans cette thèse, différents outils de réglage de tension et de gestion de la puissance réactive en fonction des conditions de raccordement des éoliennes au réseau électrique. Trois cas figure sont étudiés : raccordement direct sur un poste source de distribution, raccordement des éoliennes réparties dans un réseau de distribution et raccordement d'un ensemble de parcs éoliens au réseau de transport.Un algorithme de réglage basé sur l'asservissement de la puissance réactive est proposé pour le raccordement direct d'un parc sur un poste source. Un réglage coordonné de tension en présence de régleur en charge est proposé (D-RCT) pour le raccordement des éoliennes reparties dans un réseau de distribution. On propose aussi une version plus décentralisée du réglage coordonné (D2-RCT) qui pourrait être implantée sous forme de système multi-agents intelligents (SMA). Un system de control multi-niveaux est proposé pour le raccordement d'un ensemble de parcs éoliens au réseau de transport. Il permet de répondre de manière optimale à une demande puissance réactive envoyée par le gestionnaire du réseau de transport. Les différents types de réglages proposés sont basés sur des algorithmes d'optimisation multi-objectifs. Afin de valider en temps réel le bon fonctionnement des stratégies de réglages développées ainsi que leurs modes de communication, une implantation expérimentale sous simulateur temps réel RT-Lab a été effectuée. Enfin, les résultats des simulations montrent l'amélioration de l'intégration de la production décentralisée dans les réseaux électriques
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Cuenot, Jérémy. "Architectures d'alimentation et de commande des actionneurs haute-vitesse connectés aux réseaux avioniques à tension variable." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0263/document.
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La révolution technologique majeure des nouveaux aéronefs repose sur une électrification intensive de nombreux constituants de l'appareil et le fait que la vitesse des génératrices électriques n'est plus fixe mais variable. Cette nouvelle manière de générer la puissance électrique engendre des variations de tension sur les réseaux DC. De plus, pour accroître la compacité des Machines Synchrones à Aimants Permanents (MSAP) à puissance donnée, on augmente autant que possible leur vitesse d'entrainement, en les associant pour certaines applications à des réducteurs mécaniques. La variation du niveau de tension du bus DC alimentant une MSAP haute vitesse implique son dimensionnement afin d'assurer sa contrôlabilité sur toute la plage de vitesse reportant d'importantes contraintes sur l'onduleur de tension. Pour pallier ce problème, une solution consiste à intercaler un convertisseur DC/DC entre le filtre d'entrée et l'onduleur de tension pour maintenir la tension DC d'entrée de l'onduleur à une valeur adaptée au fonctionnement de la MSAP et optimiser son dimensionnement. Cependant, cette solution augmente l'ordre du système, ce qui accroît la complexité de son contrôle, accentuée par les contraintes liées à la nature haute-fréquence des MSAP considérées.Les travaux menés dans cette thèse concernent l'étude, l'optimisation et le contrôle des structures d'alimentation des actionneurs haute vitesse connectés aux réseaux DC avioniques à tension variable. Il en résulte que pour les applications avioniques considérées, ces architectures d'alimentation intégrant un convertisseur DC/DC supplémentaire permettent de réduire sa masse et son volume sans dégrader le rendement global de la chaîne de conversion notamment avec les convertisseurs à source impédante qui permettent de supprimer structurellement les ondulations de courant en entrée du convertisseur. De plus, des stratégies de commande Pulse Amplitude Modulation employées avec des architectures de contrôle non-linéaires (platitude, passivité) permettent d'assurer le contrôle de ces MSAP haute-vitesse tout en assurant leur stabilité sur toute la plage de fonctionnementThe main technological revolution of the new aircrafts is based on intensive electrification of many components of the aircraft. Moreover, the speed of electrical generators is no longer fixed but variable. This new way of generating electrical power generates voltage variations on DC networks. Besides, to increase the compactness of the Permanent Magnet Synchronous Machines (PMSM) at a given power, their mechanical speed is increased as much as possible by combining them with mechanical reducers for certain applications. The variation of the voltage level of the DC bus supplying a high-speed PMSM implies its sizing in order to ensure its controllability over the entire speed range which carries significant stresses on the Voltage Source Inverter (VSI). To solve this problem, one solution consists in adding an extra DC / DC converter between the input filter and the VSI to maintain the inverter input voltage at a value adapted to the operating point of the PMSM and to optimize its dimensioning. However, this solution increases the order of the system, which increases the complexity of its control, accentuated by the constraints related to the high-frequency nature of the PMSMs considered. The work carried out in this thesis concerns the study, the optimization and the control of the power supply architecture of the high-speed actuators connected to variable-voltage avionic DC networks. As a result, for the avionics applications considered, these power supply architectures integrating an additional DC / DC converter make it possible to reduce the mass and the volume of the power supply structure without degrading the overall efficiency of the conversion chain, in particular by using the impedance-source converters which allow to cancel the DC input current ripples. In addition, Pulse Amplitude Modulation (PAM) control strategies used with non-linear control architectures (flatness, passivity) make it possible to control these high-speed PMSMs while ensuring their stability over the entire operating range
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Dasco, Antony. "Contrôle et modélisation du convertisseur multi-modulaire AC-AC pour les liaisons offshore à haute tension et basse fréquence." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAT057/document.
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L’objectif principal de cette thèse consiste à développer des stratégies de modélisation et de contrôle pour la conversion de fréquence en utilisant un convertisseur multi-modulaire sans utilisation de lien en continu. Ce convertisseur est nécessaire pour l’intégration des énergies renouvelables offshore dans un réseau de transport à basse fréquence. La basse fréquence électrique profite à la fois des avantages des réseaux alternatif et continu. L’utilisation de convertisseurs modulaires dans ces réseaux permet, entre autres, de supprimer le transformateur du côté de la basse fréquence électrique. Dans cette optique, l’énergie est convertie depuis la fréquence nominale à 50 Hz ou 60 Hz (considérée comme la haute fréquence) vers un tiers de 50 Hz. Le convertisseur est aussi capable de transformer d’autres valeurs de fréquence. Dans un premier temps, la méthode de modélisation du convertisseur est reliée à la théorie du transformateur de voltage triphasé avec un couplage en YDY. En deuxième lieu, l’application du théorème de superposition nous permet d’évaluer séparément la contribution de chaque fréquence. Dans un dernier temps, le contrôle principal du convertisseur utilise des correcteurs résonants, capables donc de travailler directement avec les courants internes du convertisseur qui sont à deux fréquences nominales. Grâce au découplage entre l’entrée du convertisseur et sa sortie, les défauts et les situations de déséquilibre ne se propagent pas vers la sortie du convertisseur, fonctionnement requis pour l’application en offshoreThe purpose of this thesis is to develop strategies to model and control a modular multilevel converter in order to transform frequency without passing through a direct current link. This converter is needed for application in offshore systems where the energy, produced by the offshore renewables, is transmitted using low frequency links. Low frequency presents benefits from alternative and direct current technologies. Moreover, a voltage transformer is not required at the low frequency side when the proposed converter is used as a frequency transformer. In this scenario, frequencies are converted from the highest nominal frequency (50 Hz or 60 Hz) to one third of 50 Hz. Conversion to other frequency values has been tested as well using the same converter. A methodology based on the electrical transformer theory when connected in YΔY coupling and, the superposition theorem to separate the contribution from both frequencies, are proposed to link these currents with the two three-phase systems at different nominal frequencies. Resonant controllers are introduced to efficiently correct internal current signals of the converter that nominally are constituted of two frequencies: input and output frequencies. The converter is able to decouple the input side from the output. Therefore, faults and unbalanced conditions on the input side are not propagated to the output-side of the converter, which is required for offshore applications
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Aimene, Merzak. "Services au système et gestion d'interactions énergétiques transitoires dans un parc éolien offshore." Thesis, Le Havre, 2016. http://www.theses.fr/2016LEHA0020/document.
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L’intégration massive de la production d’énergie éolienne intermittente au niveau des réseaux électriques pose un problème de stabilité du système électrique. En effet les caractéristiques sont très différentes de celles de sources conventionnelles maîtrisées par les gestionnaires de réseau. Par conséquent, l’injection de cette énergie induit de nouveaux challenges pour les gestionnaires de réseaux électriques. De plus, les conditions de raccordement évoluent et tendent à ce que toutes les sources participent aux services rendus aux systèmes électriques. Les travaux de cette thèse sont focalisés sur la proposition d’une nouvelle stratégie de commande non-linéaire basée sur la commande par « platitude à une boucle » d’un système de conversion d’énergie éolienne. Cette stratégie de contrôle vise la gestion des interactions au point de connexion par la génération et le suivi de trajectoires de références. De par le fait que toutes les variables du système sont liées à la « sortie plate » de ce système, cette commande procure une rapidité de réponse et une bonne maitrise des régimes transitoires. La mise en œuvre de cette nouvelle stratégie de contrôle pour la constitution d’un parc éolien offshore, capable de satisfaire différentes conditions de raccordement a été simulée avec succès. Plus particulièrement, l’évaluation de l’impact de différents défauts du réseau sur les services proposés (Régulation de fréquence et de tension, la tenue aux creux de tension.) a été réaliséeThe massive integration of intermittent production of wind energy in electrical networks creates an electrical system stability problem. Indeed, its characteristics are very different from those of conventional sources controlled by Grid managers. Therefore, the injection of this energy makes new challenges for power Grid operators. Moreover, the connection conditions are evolving and go towards the situations that all different sources participate into services of electrical systems. This thesis proposes a new nonlinear control strategy based on a « one loop flatness control » of a wind energy conversion system. This control strategy has aim of energy interactions management at the connection point through generation and tracking of reference trajectories. As all system variables are functions of the « flat output » of the system, this control provides fast response and good control in transient state. The application of this new control strategy into an offshore wind farm which is able to satisfy different connection conditions was simulated successfully. Specifically, effects of various grid faults on the proposed ancillary services (frequency and voltage regulation, and low-voltage ride through capabilities) were performed
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Wu, Cong Martin. "Etude prospective de la topologie MMC et du packaging 3D pour la réalisation d’un variateur de vitesse en moyenne tension." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAT027/document.
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La topologie modulaire multiniveaux est une structure d'électronique de puissance construite par la mise en série de sous-modules identiques, composés chacun d'une cellule de commutation et d'un condensateur. Un tel système de conversion pouvant comporter un grand nombre de cellules permet d'augmenter le rendement global et la qualité des signaux en sortie. De plus, il permet d'utiliser des composants basse tension présentant un meilleur comportement dynamique et un rapport qualité-prix bien supérieur aux composants moyenne tension. Il permet également, par rapport aux structures conventionnelles, une grande souplesse pour la conception et la fabrication du fait de son aspect modulaire, tout en s'affranchissant d'un transformateur volumineux et onéreux en entrée. Comparé aux autres types de topologies, avantageuses avec un nombre limité de niveaux, le convertisseur modulaire multiniveaux semble être mieux adapté aux applications en moyenne et haute tensions, qui sont tributaires de l'association des composants de puissance. Néanmoins, pour la variation de vitesse, un certain nombre de défis technologiques ont été mis en évidence, compte tenu du fonctionnement particulier de l'onduleur modulaire multiniveaux et des contraintes imposées par l'opération en très basse fréquence. En le fonctionnement normal, la forme d'onde des courants internes, contrairement aux autres types de topologies, n'est pas symétrique en raison de la distribution du courant direct dans chaque bras. Cela entraîne une disparité significative en termes de dissipation thermique parmi les interrupteurs constituant un sous-module. Avec le choix d'une technologie de packaging 3D, la possibilité de refroidir les puces semi-conductrices en double-face offre une meilleure capacité de refroidissement et une nouvelle perspective de conception des modules pour cette application. Un nouveau concept de report de puces est présenté et un prototype de tel module a été réalisé, modélisé et caractérisé. Il permet d'équilibrer globalement la chaleur dissipée par les puces sur les deux faces du module, problème inhérent à l'emploi de structure 3D. Conjugué à la mutualisation d'un interrupteur par deux puces en parallèle, la nouvelle architecture a aussi pour objectif d'équilibrer le refroidissement double-face dans le temps. En effet, pour les opérations en basse fréquence, les interrupteurs fonctionnent en régime instationnaire avec de forte variation de température, il n'est donc plus possible de compenser les effets thermomécaniques de chaque composant l'un par l'autre, comme en régime stationnaire et avec un positionnement planaire des puces. D'autre part, d'un point de vu systémique, la stratégie de commande et le dimensionnement des condensateurs flottants de l'onduleur modulaire multiniveaux sont deux aspects intimement liés. En effet, les condensateurs flottants sont le siège d'ondulations de tension de très forte amplitude. Cela a pour effet de déstabiliser l'onduleur, voire de provoquer la destruction des composants en atteignant des niveaux de tension trop élevés. Ainsi, des contrôleurs judicieusement conçus permettent de réduire les ondulations indésirables, et a fortiori, d'embarquer des capacités moins importantes dans le système, tant que ces dernières sont inversement proportionnelles à l'ondulation de la tension. Afin d'avoir une compréhension approfondie sur les dynamiques régissant le convertisseur modulaire multiniveaux, un modèle dynamique global basé sur la représentation d'état a été établi. Bien que cette représentation soit limitée à l'harmonique 2 des grandeurs caractéristiques, elle permet une fidèle interprétation du mécanisme de conversion sans passer par des modèles énergétiques bien plus complexes à exploiter, et de proposer des lois de commande montrant leur efficacité notamment autour de la fréquence nominale. Cela a été vérifié sur une maquette de puissance réalisée dans le cadre de cette thèseMultilevel modular topology converts energy between two direct and alternative endings. This structure is constructed by the series connection of identical sub-modules, composed of a switching cell and a floating capacitor, and with arm inductors. Such a conversion system may reach a large number of levels increases the overall efficiency and quality of the output signals. In addition, it allows the use of low voltage components with better dynamics and cost effectiveness above the high voltage components. It also allows flexibility in the work of design and manufacture due to its modularity, while avoiding a bulky and expensive input transformer, regarding the conventional technology. Compared with other types of topologies, advantageous with a limited number of levels, the modular multilevel converter seems to be more suited for medium and high voltage applications, which are dependent on the association of power components. However, for variable speed drive application, a certain number of technological challenges have been highlighted, given the specific functional characteristics of the modular multilevel inverter and the constraints imposed by the very low frequency operation. On the one hand, for the normal operation of a multilevel modular converter, the waveform of the internal currents, in contrast to other types of topologies, is not symmetrical due to the distribution of the direct current in each phase leg. This may entail a significant disparity in terms of heat dissipation within the switching devices constituting a sub-module. Therefore, the problem of thermal management of active components is emphasized in the use of a modular multilevel converter. With the choice of a 3D packaging technology, interconnection by bumps, the ability to cool the semiconductor chips through the both sides of a module offers better cooling effects and a new perspective to design the power module for the studied structure. The concept of laying chips on both the two substrates of module without facing each other provides overall balanced dissipation in the space and permit to overcome the unbalanced heat distribution induced by bumps. Combined with the sharing of a switch by two chips in parallel, the proposal of the new architecture for 3D power module also aims to balance the double-sided cooling in the time range. Indeed, for the very low frequency operation, the switches operate in unsteady state where each switch has its own thermal behavior, it is no longer possible to compensate the thermo-mechanical constraints over each component with the help of the others, as in steady state and with a planar chips positioning scheme. On the other hand, from a systemic point of view, the control strategy and the dimensioning of floating capacitors of modular multilevel inverter are two interrelated aspects. Because the floating capacitors, having the role of energy sources, are loaded / unloaded through the modulation period, which causes very high voltage ripples across those capacitors with a very low frequency. This will destabilize the inverter and even provoke the destruction of components by approaching too high voltage levels. Thus, wisely designed controllers reduce unwanted ripples and, furthermore, allow embarking much smaller capacity in the system, as they are inversely proportional to the voltage ripple. In order to have a thorough understanding on the dynamics governing the modular multilevel converter, a comprehensive dynamic model based on state-space representation was established. Although this representation is limited to the second harmonic of characteristic variable, it allows a faithful interpretation of the conversion mechanism without using energy models, more complex to operate, and control laws can also be proposed and their effectiveness around the nominal frequency has been underlined. Concerning the very low frequency operations, another solution has been proposed and is ongoing patent pending
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Ramachandran, Ragavendran. "Gestion des flux énergétiques d'une ferme éolienne offshore connectée à un système HVDC au travers d'un redresseur à diodes." Thesis, Ecole centrale de Lille, 2019. http://www.theses.fr/2019ECLI0015.
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La transition énergétique pour un monde plus durable est désormais la priorité de nombreux pays. Dans cet objectif, notamment en Europe, le développement de l’énergie éolienne en mer (offshore) a été rapide. Le transport de l’électricité en Courant Continu Haute Tension (HVDC) basé sur un convertisseur électronique à source de tension (VSC) est la solution de transport, pour les fermes éoliennes en mer éloignées de plus de 50 km de la côte. La solution d’un redresseur à diodes dans les stations de conversion en mer est plus compacte, robuste et moins cher. Cette thèse porte sur les divers problèmes technologiques et scientifiques liés au contrôle du réseau alternatif isolé en mer permettant le raccordement des fermes éoliennes. Ces verrous sont d’abord examinés en détail dans l’état de l’art. Ensuite, une organisation du contrôle de la tension et de la fréquence de ce réseau (dit Grid Forming) est proposée en utilisant les caractéristiques techniques P-V et Q-f avec une solution pour la synchronisation entre les éoliennes. Certaines des solutions de contrôle en Grid Forming sont comparées et évaluées à l'aide de simulations dans le domaine temporel, pour un cas d'étude donné. Puis, une nouvelle solution est proposée pour le démarrage du réseau offshore (black start) et un contrôle automatisé de la supervision, basé sur la modélisation sous forme d’un système à événements discrets (SED). La théorie du contrôle par supervision (TCS) est implémentée et testée pour un cas d'étude. Ensuite, les différents types de défauts du système sont analysés à l’aide de la littérature; et le schéma de contrôle du Grid Forming conçu dans cette thèse est complétée pour apporter une capacité de fonctionnement lors d’un défaut du réseau AC offshore. Enfin, une brève analyse est faite sur les défis pour l’intégration de ce type de ferme au réseau MTDCEnergy Transition for a more sustainable world is now the priority in societies. Towards this objective, especially in Europe, the offshore wind energy development has been fast. For Offshore Wind Power Plants (OWPP) farther from the shore (50 km and beyond) Voltage Source Converter (VSC) based High Voltage DC (HVDC) Transmission has become a the prominent solution. Replacement of offshore VSC station by multiple Diode Rectifier Units (DRUs) led to a cheaper, more compact and robust solution. This thesis focusses on various technological and scientific problems involved in the control system of the Offshore Wind power Plant with Diode Rectifier (DR) based HVDC transmission. These challengess are first reviewed in detail along with the state of the art. Then, based on the system dynamics, a grid forming control scheme is proposed by using the P-V and Q-f droop relationships with a solution for the synchronization of the wind generators. Following this, some of the selected control solutions in the literature for this topology are reviewed, compared and assessed by using time domain simulations of a study case. Following this, a novel black start strategy is devised for the offshore network and a Supervisory Control is implemented for a study case by using a Discrete Event System (DES) based modeling and Supervisory Control Theory (SCT). The various faults in the offshore system are then analyzed and the above designed Grid forming control scheme is extended with Fault Ride through (FRT) capability, for offshore AC grid faults. Finally, a brief analysis is done on the challenges for the integration of this OWPP topology into a Multi Terminal DC (MTDC) network
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Shinoda, Kosei. "Contrôle et opération des réseaux HVDC multi-terminaux à base de convertisseurs MMC." Thesis, Ecole centrale de Lille, 2017. http://www.theses.fr/2017ECLI0017.
Full textAbstract:
Cette thèse porte sur la commande de réseaux multi-terminaux à courant continu (MTDC) basés sur des convertisseurs multiniveaux modulaires (MMCs).Tout d’abord, notre attention se focalise sur l'énergie stockée en interne dans le MMC qui constitue un degré de liberté additionnel apporté par sa topologie complexe. Afin d’en tirer le meilleur parti, les limites de l’énergie interne sont formulées mathématiquement.Afin de maîtriser la dynamique de la tension DC, l’utilisation de ce nouveau degré de liberté s’avère d’une grande importance. Par conséquent, une nouvelle de stratégie de commande, nommée «Virtual Capacitor Control», est proposée. Cette nouvelle méthode de contrôle permet au MMC de se comporter comme s’il possédait un condensateur de taille réglable aux bornes, contribuant ainsi à l’atténuation des fluctuations de la tension DC.Enfin, la portée de l’étude est étendue au réseau MTDC. L'un des défis majeurs pour un tel système est de faire face à une perte soudaine d'une station de convertisseur qui peut entraîner une grande variation de la tension du système. A cet effet, la méthode de statisme de tension est la plus couramment utilisée. Cependant, l'analyse montre que l'action de contrôle souhaitée risque de ne pas être réalisée lorsque la marge disponible de réserve de puissance du convertisseur est insuffisante. Nous proposons donc une nouvelle structure de contrôle de la tension qui permet de fournir différentes actions en fonction du signe de l'écart de la tension suite à une perturbation, associée à un algorithme qui détermine les paramètres de statisme en tenant compte du point de fonctionnement et de la réserve disponible à chaque stationThe scope of this thesis includes control and management of the Modular Multilevel Converter (MMC)-based Multi-Terminal Direct Current (MTDC).At first, our focus is paid on the internally stored energy, which is the important additional degree of freedom brought by the complex topology of MMC. In order to draw out the utmost of this additional degree of freedom, an in-depth analysis of the limits of this internally stored energy is carried out, and they are mathematically formulated.Then, this degree of freedom of the MMC is used to provide a completely new solution to improve the DC voltage dynamics. A novel control strategy, named Virtual Capacitor Control, is proposed. Under this control, the MMC behaves as if there were a physical capacitor whose size is adjustable. Thus, it is possible to virtually increase the equivalent capacitance of the DC grid to mitigate the DC voltage fluctuations in MTDC systems.Finally, the scope is extended to MMC-based MTDC grid. One of the crucial challenges for such system is to cope with a sudden loss of a converter station which may lead to a great variation of the system voltage. The voltage droop method is commonly used for this purpose. The analysis shows that the desired control action may not be exerted when the available headroom of the converter stations are insufficient. We thus propose a novel voltage droop control structure which permits to provide different actions depending on the sign of DC voltage deviation caused by the disturbance of system voltage as well as an algorithm that determines the droop parameters taking into account the operating point and the available headroom of each station
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Li, Yafang. "Etude d’un convertisseur DC-DC pour les réseaux haute tension à courant continu (HVDC) : modélisation et contrôle du convertisseur DC-DC modulaire multiniveaux (M2DC)." Thesis, Ecole centrale de Lille, 2019. http://www.theses.fr/2019ECLI0006/document.
Full textAbstract:
Les travaux présentés dans ce mémoire portent sur les convertisseurs continu-continu (DC/DC) pour les réseaux de transport à Courant Continu (HVDC) dans un contexte de réseau maillé de type Multi Terminaux DC (MTDC). Dans ce genre de réseau, les convertisseurs DC/DC sont nécessaires pour interconnecter ces réseaux. L’objectif de ce travail est donc d’étudier un convertisseur DC/DC pour des applications à haute tension et forte puissance. De nombreux convertisseurs DC/DC classiques existent, mais ne sont pas adaptés à ces niveaux de tension et puissance. Le volume et coût sont les points clés de l’étude pour l’industrialisation des structures dédiées aux réseaux HVDC. Parmi les structures identifiées, le convertisseur DC-DC Modulaire Multiniveaux (M2DC), récent et compact, a été finalement choisi. Le travail proposé développe l’étude du M2DC en régime établi et une modélisation en modèle moyen de ce convertisseur. Ensuite, des lois de contrôle sont proposées pour valider les analyses précédentes sur la base du principe de l’inversion du modèle. Le travail vise enfin à valider les analyses et le contrôle à l’aide de la maquette du Convertisseur Modulaire Multiniveaux (MMC) du L2EP. Pour cela, un dimensionnement du M2DC basé sur le MMC existant est proposé. Enfin, des simulations HIL (Hardware-In-the-Loop) valident les analyses et montrent la faisabilité du prototypage du M2DCThis work is based on Multi Terminal Direct Current (MTDC) grids. In the MTDC grid, DC/DC converter stations are needed to connect different HVDC grids. A lot of DC/DC converters have been studied and developed, but are not suitable for high voltage and great power constraints. Therefore, the objective of this work is the study of a DC/DC converter for high voltage and great power applications. For the potentially HVDC applications, the volume and costs are major criteria. According to this, a high voltage and great power potential DC/DC converter is selected, which is the DC-DC Modular Multilevel Converter (M2DC). Focusing on the M2DC, the work proposes analyses in steady state and builds an average model for the converter. Based on the average model, the basic control algorithm for the converter is developed to validate the previous analysis. Since the thesis aims to use the existing L2EP Modular Multilevel Converter (MMC) to test the M2DC model and control, a design of the M2DC based on MMC is proposed. Finally, the M2DC HIL (Hardware In-the-Loop) simulations results are presented confirming previous analyses and allowing to go on to prototyping the M2DC on the base of the existing MMC
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Denis, Guillaume. "Les nouvelles stratégies de contrôle d’onduleurs pour un système électrique 100% interfacé par électronique de puissance." Thesis, Ecole centrale de Lille, 2017. http://www.theses.fr/2017ECLI0020/document.
Full textAbstract:
Dans un contexte de développement des énergies renouvelables et des liaisons HVDC dans les systèmes électriques, les travaux présentés s’attachent au fonctionnement technique de tels systèmes. La génération éolienne, photovoltaïque et les liaisons HVDC sont interfacées par dispositifs d’électronique de puissance au réseau de transport électrique. Dès lors, serait-il envisageable d’alimenter la demande électrique uniquement via des sources électriques interfacées par des convertisseurs statiques ?Le pilotage du système électrique par électronique de puissance constitue un changement radical du fonctionnement dynamique des réseaux. La traditionnelle stratégie de commande « grid-following » des onduleurs a montré ses limites lorsque la pénétration de ces dispositifs devient importante. Elle doit être révisée au profit de stratégies dîtes « parallel grid-forming ».Dans cette thèse, les besoins fondamentaux du système électrique sont d’abord analysés pour définir les exigences de la stratégie « parallel grid-forming », ainsi que les défis associés. Selon ces spécifications, une méthode de synchronisation de sources « grid-forming » est ensuite proposée ainsi qu’un contrôle de tension, adapté aux limitations physiques des convertisseurs de tension PWM. La stabilité de la solution est discutée pour différentes configuration de réseau. Enfin, une stratégie de limitation du courant a été spécifiquement développée pour palier la sensibilité des VSC aux sur courants, lors d’évènements réseaux éprouvant. Les idées développées sur un convertisseur unique sont appliquées à petits réseaux afin d’extraire des interprétations physiques depuis des simulations temporellesIn the context of renewable energy and HVDC links development in power systems, the present work concerns the technical operations of such systems. As wind power, solar photovoltaics and HVDC links are interfaced to the transmission grid with power-electronics, can the system be operated in the extreme case where the load is fed only through static converters?Driving a power system only based on power electronic interfaced generation is a tremendous change of the power system paradigm that must be clearly understood by transmission grid operators. The traditional “grid-feeding” control strategy of inverters exhibits a stability limit when their proportion becomes too important. The inverter control strategy must be turned into a “parallel grid-forming” strategy.This thesis first analyses the power system needs, proposes the requirements for “parallel grid-forming” converters and describes the associated challenges. Accordingly, the thesis gives a method for designing a stable autonomous synchronization controls so that grid-forming sources can operate in parallel with a good level of reliability. Then, a method is proposed to design a voltage control for a grid-forming PWM source taking into account the limited dynamic of large converters. The robustness of the solution is discussed for different configuration of the grid topology. A current limiting strategy is presented to solve the current sensitivity issue of grid-forming converters, subject to different stressing events of the transmission grid. The ideas developed on a single converter are then applied on small grids with a limited number of converters to allow a physical interpretation on the simulation results
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Weng, Jian-Ping, and 翁健評. "Tension Control for Web-fed Machine." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/55902579756512981435.
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碩士國立成功大學
航空太空工程學系
87
Abstract Subject: Tension Control for Web-fed Machine Student: Jian-Ping Weng Advisor: Chieh-Li Chen Tension control systems are commonly used in our daily life and business, such as VHS, tape rewinder, recorder, tape-making procedure, etc. In these systems, it is clear that the quality of products and the performance of systems are determined by tension and velocity control of the moving web. Too small tension in the winding process will make the web flagging. Oppositely, too large tension will make the web overreach, leading to permanent distortion. Besides, the slow winding rate will make efficiency down and the fast winding rate will amplify the vibration amplitude of moving web so that it will be hard to control. In this paper, the web-fed machine modeling and control are presented. SMC (Sliding Mode Control) method is employed to control the tension and velocity of the moving web. The robustness of SMC method can be suitable for more uncertainties and external disturbances. It makes the operation range more flexible, and upgrades the system performance and the system stability. Further, it improves the manufacture efficiency and the product quality of the web-fed machine.
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Lu, Ming-Jain, and 呂銘展. "Digital Control and Computer Communicationof Tension Meters." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/a24hqm.
Full textAbstract:
碩士國立臺北科技大學
機電整合研究所
98
Most of tension meters for coil winding machines are implemented by analog circuit. However, as the diameter or material of the wire or coil type change, the tension of the wire should be changed too. The adjustment for each tension meter is quite troublesome and hard to maintain consistent. Thus, the quality of winded coils are difficult to be uniform. Hence, in this study, the tension meter is implemented by digital circuit which provides several functions such as the initial setup for accurate reading of tension, the tensile value display, monitoring and adjusting from pushbuttoms or from a remoted personal computer (PC). These functions can let up to 16 tension meters be adjusted, monitored and controlled simultaneously through computer network. The digital tension meter consists of RS-232 or RS-485 to communicate with a PC (simulating main controller of coil winding machine). Also, a stepper motor and a small size liquid crystal display (LCD) are integrated into the designed digital circuit with the micro-processor W78E516B to control the tension meter. Finally, we have designed two systems for the digital tension meter. One is for off-line system (operating individually), and the other one is for on-line system (controlled and communicated through PC). Both of these two systems contain the functions of initial setup, tensile value display, saving and control. For the on-line system, the digital tension meter can receive the operation code from the PC. Above all, the tension meter with above functions have been proved its versatility with coil winding machine. And the commercialization of the digital tension meter is left for the future work.