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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
381

Έλεγχος μηχανής συνεχούς ρεύματος τροφοδοτούμενης από τριφασικό πλήρως ελεγχόμενο αντιστροφέα

Μιχαλόπουλος, Ιωάννης 07 July 2015 (has links)
Σήμερα η ανάγκη για δημιουργία ποιοτικών και φθίνων και ανταγωνιστικών βιομηχανικών προϊόντων έχει σαν αποτέλεσμα να χρειαζόμαστε αυτοματισμούς και αυτόματο έλεγχο ηλεκτρικών μηχανών με μεγάλη ακρίβεια και αδιάλειπτη λειτουργία απο διαταραχές του περιβάλλοντος . Επιπλέον το ενεργειακό πρόβλημα που είναι από τα σπουδαιότερα προβλήματα του πλανήτη και του ανθρώπου σήμερα οδηγούν στην ανάγκη ελαχιστοποίησης των ενεργειακών απωλειών με αποτέλεσμα συνήθως να επιθυμούμε λειτουργία των ηλεκτρομηχανικών συστημάτων με μηδενική κατανάλωση/ παραγωγή άεργου ισχύος . Η Ηλεκτρική μηχανή συνεχούς ρεύματος με διέγερση σε σειρά χρησιμοποιείται λόγω των ιδιαίτερων χαρακτηριστικών της σε πολλές εφαρμογές που χρειάζονται υψηλή ροπή εκκίνησης όπως ανυψωτικά μηχανήματα, σιδηροδρομικά οχήματα. Οι ανορθωτές με ελεγχόμενη έναυση αλλά και σβέση κατά PWM προτιμούνται έναντι των διόδων και των θυρίστορς γιατί μας δίνουν περισσότερες δυνατότητες ελέγχου . Η Μοντελοποίηση , σχεδιασμός συστήματος ελέγχου, ευστάθειας του συστήματος για την μηχανή συνεχούς ρεύματος οδηγούμενης από τριφασικό ανορθωτή ερευνάται. Γίνεται εξαγωγή του μοντέλου, στο τριφασικό σύστημα και στο πλαίσιο park, με βάση την δυναμική ανάλυση Εuler -Lagrange . Για την εξαγωγή του μοντέλου γίνεται ακόμα χρήση του Averaging Analysis . Ανάλυση που βασίζεται στην παθητικότητα μάς δείχνει ότι το σύστημα είναι ευσταθές πεπερασμένης εισόδου-πεπερασμένης κατάστασης. Οι ελεγκτές που αναπτύσσονται σε αυτή τη εργασία είναι ο ασαφής ελεγκτής, ο νευροασαφής που χρησιμοποιούνται ευρέως σε μη γραμμικά συστήματα στην βιομηχανία, ο PI σειριακός (cascade) ελεγκτής που συνηθίζεται στις ηλεκτρικές μηχανές. Τέλος επιχειρείται ο σχεδιασμός ενός PI ελεγκτή με υπολογισμό κερδών από νευροασαφή εκτιμητή. Ο ασαφής ελεγκτής σχεδιάζεται με πρόβλεψη σφάλματος και επιτυγχάνει πολύ καλή ρύθμιση των στροφών και καλό έλεγχο στης αέργου ισχύος, εξομοιώσεις επιβεβαιώνουν την απόδοση του ελεγκτή. Ομοίως ισχύουν για τον νευροασαφή ελεγκτή με το πλεονέκτημα μικρότερου υπολογιστικού χρόνου αλλά μειονεκτεί μεγαλύτερης εμφάνισης ενός μόνιμου σφάλματος. Ο PI σειριακός (cascade) επιτυγχάνει άριστη ρύθμιση αέργου ισχύος και καλή ρύθμιση στροφών ενώ ο PI casacde- Anfis μας δίνει ελαφριά καλύτερα αποτελέσματα αλλά αφήνει αρκετές δυνατότητες για περαιτέρω σχεδιασμό και έρευνα. Επίσης γίνεται κάποια ανάλυση για εξαγωγή συμπερασμάτων ευστάθειας και σύγκλισης για τα σύστημα κλειστού βρόχου. Τα αποτελέσματα τα επιβεβαιώνουμε και τα συγκρίνουμε μέσω εξομοιώσεων. / Nowadays , the demand for precise control in industrial applications require the design and development of advanced controllers. Also the energy problem which is one of the most important global problems lead to the need of high energy efficient systems. In industrial applications in most cases ,due to the energy problem , we desire operation with unity power factor. The dc series connected motor is preferred in many application such as railway and levitating systems due to its high starting torque. We choose the 3 -phase pulse width modulation rectifier because of its many capabilities comparison with thyristor rectifiers. Modeling, control design and stability analysis of series connected dc motor fed by three-phase PWM ac/dc voltage converter are investigated. The designed controllers are fuzzy , neuro fuzzy, PI cascade and Anfis- pi cascade controller. The model is obtained via Euler -Lagrange dynamic analysis. Also we used the averaging analysis in order to determine the dynamic model of the system in a-b-c frame and d-q park's frame. We prove the ISS stability of the open loop system based on passivity analysis. The fuzzy use a predictive logic based on the acceleration of the motor, we result excellent precise control of angular velocity and a satisfied control of reactive power. Neuro Fuzzy controller has the same effectiveness with less computational effort but has a possibility to occur a small permanent error in angular velocity. PI cascade controller has as a result a excellent response at reactive power and good response in angular velocity with more less computational effort. ANFIS -PI cascade controller have a bit better results from PI-cascade controllers but it leaves hopes for more optimum designs in feature. Furthermore there are some stability and convergence analysis for the closed loop system. Simulation results verify the effectiveness of each controller for comparison.
382

Visual Discrimination of Speed-accuracy Tradeoffs

Young, Scott Jason 08 March 2011 (has links)
Although research has highlighted the importance of decisions when learning and performing motor actions, few studies have focused on individuals’ ability to choose between potential motor actions. To help bridge this gap, this thesis presents a series of studies that investigate the behaviour of able-bodied individuals when attempting to choose movements based on a speed-accuracy tradeoff. In the first study, a two-alternative forced-choice task was used to determine whether people are consistent with Fitts’s law when choosing the movement they perceive to require the least movement duration. Participants performed almost perfectly when clear visual cues were available—when one of the targets was closer, wider, or both. Contrary to Fitts’s law, however, participants showed a preference for closer targets when visual cues were not informative—when one of the targets was closer and narrower. This study demonstrates that motor decisions are not always optimal, especially when participants are naïve at the task. To determine the basis of individuals’ preference for closer targets, a pair of studies explored the relation between motor decisions, imagined movements, and visual perception. Participants showed a similar deviation from Fitts’s law when imagining movements—believing that movement duration increased with distance within the same index of difficulty. Participants did not behave similarly, however, in a perceptual version of the decision task. These results suggest that imagined movements and motor decisions are linked, but they are not always based on veridical representations of actual movement. To further probe the origin of individuals’ erroneous belief about movement duration, the final study of this thesis measured movement duration for movements made at speeds other than ‘as fast as possible’. Movements made at more natural movement speeds shared important similarities with decisions and imagined movements. This study suggests that the biases seen in naïve motor decisions might originate from participants considering movements for which they have more experience, such as target-directed movements made at a naturally-selected pace. Together, the findings presented in this thesis may help to identify the ways that motor decisions can deviate from optimal, suggesting how those decisions must change with practice to better accomplish a task.
383

DPA – 1 testų patikimumas ir informatyvumas po priekinių kryžminių raiščių rekonstruojamosios operacijos / Reliability and validity of DPA-1 testing procedures after anterior cruciate ligament recontruction

Kanavolaitė, Agnė 30 June 2011 (has links)
Temos aktualumas: Siekiant įvertinti kelio sąnario funkciją po priekinio kryžminio raiščio plyšimo naudojami įvairūs metodai: izokinetinis testavimas dinamometru (Kannus et al., 1992; Risberg et al., 2009), judesio analizė (Risberg et al., 2009), elektromiografija, klinikiniai testai (Irrgang, 2003; Lee et al., 2008) ir klausimynai (Irrgang, 2001; Lee et al., 2008). Ieškodami patikimesnių būdų įvertinti žmogaus nervų- raumenų sistemos valdymo efektyvumą, Kauno technologijos universiteto ir UAB „Katra“ specialistai kartu su Lietuvos kūno kultūros akademija sukūrė naują originalų prietaisą – žmogaus rankų ir kojų judesių dinaminių parametrų analizatorių (DPA–1). Tyrimo objektas: DPA testų patikimumas ir informatyvumas. Tyrimo tikslas: Nustatyti DPA–1 testų patikimumą ir informatyvumą po priekinio kryžminio raiščio rekonstruojamosios operacijos. Tyrimo uždaviniai: 1. Nustatyti DPA–1 testų patikimumą, atliekant standartines ir variabilias užduotis po priekinių kryžminių raiščių rekonstruojamosios operacijos. 2. Nustatyti DPA–1 testų informatyvumą, atliekant standartines ir variabilias užduotis po priekinių kryžminių raiščių rekonstruojamosios operacijos. Tyrimas atliktas Lietuvos kūno kultūros akademijoje „Žmogaus motorikos“ laboratorijoje. Jame dalyvavo 34 tiriamieji, kurie buvo suskirstyti į dvi grupes. Pirmąją grupę sudarė pacientai, patyrę kelio sąnario priekinio kryžminio raiščio rekonstruojamąją operaciją (n=17). Šių tiriamųjų amžiaus vidurkis – 31,3 ± 7,8 metai, ūgis –... [toliau žr. visą tekstą] / Relevancy: Different methods are used to assess capabilities of knee function after ACL injury including isokinetic dynamometry (Kannus et al., 1992, Risberg et al., 2009), motion analysis (Chmielewski et al., 2005, Risberg et al., 2009), electromyography (Chmielewski et al., 2005), clinical testing (Irrgang, 2003, Lee et al., 2008) and questionnaires (Irrgang, 2001, Lee et al., 2008). In order to devise more reliable methods to evaluate the efficiency of human neuromuscular control, the dynamic parameters’ analyzer of human’s hands and legs movements (DPA-1, Patent No. 5251; 2005 08 25) was constructed by Kaunas Technology University and „Katra“ engineers in collaboration with Lithuanian Academy of Physical Education. The object of the study: the reliability and validity of DPA-1 testing procedures. The aim of the study is to establish the reliability and validity of DPA-1 testing procedures after anterior cruciate ligaments reconstructive surgery. The goals of the study are the following: 1. To establish the reliability of DPA-1 testing procedures while performing standard and variable tasks after anterior cruciate ligaments reconstructive surgery. 2. To establish the validity of DPA-1 testing procedures while performing standard and variable tasks after anterior cruciate ligaments reconstructive surgery. The recearch was performed in the Laboratory of Human Motorics at the Lithuanian Academy of Physical Education. 34 participants, who were divided into two groups... [to full text]
384

Hierarchical error processing during motor control

Krigolson, Olave 26 September 2007 (has links)
The successful execution of goal-directed movement requires the evaluation of many levels of errors. On one hand, the motor system needs to be able to evaluate ‘high-level’ errors indicating the success or failure of a given movement. On the other hand, as a movement is executed the motor system also has to be able to correct for ‘low-level’ errors - an error in the initial motor command or change in the motor command necessary to compensate for an unexpected change in the movement environment. The goal of the present research was to provide electroencephalographic evidence that error processing during motor control is evaluated hierarchically. The present research demonstrated that high-level motor errors indicating the failure of a system goal elicited the error-related negativity, a component of the event-related brain potential (ERP) evoked by incorrect responses and error feedback. The present research also demonstrated that low-level motor errors are associated with parietally distributed ERP component related to the focusing of visuo-spatial attention and context-updating. Finally, the present research includes a viable neural model for hierarchical error processing during motor control.
385

Visual Discrimination of Speed-accuracy Tradeoffs

Young, Scott Jason 08 March 2011 (has links)
Although research has highlighted the importance of decisions when learning and performing motor actions, few studies have focused on individuals’ ability to choose between potential motor actions. To help bridge this gap, this thesis presents a series of studies that investigate the behaviour of able-bodied individuals when attempting to choose movements based on a speed-accuracy tradeoff. In the first study, a two-alternative forced-choice task was used to determine whether people are consistent with Fitts’s law when choosing the movement they perceive to require the least movement duration. Participants performed almost perfectly when clear visual cues were available—when one of the targets was closer, wider, or both. Contrary to Fitts’s law, however, participants showed a preference for closer targets when visual cues were not informative—when one of the targets was closer and narrower. This study demonstrates that motor decisions are not always optimal, especially when participants are naïve at the task. To determine the basis of individuals’ preference for closer targets, a pair of studies explored the relation between motor decisions, imagined movements, and visual perception. Participants showed a similar deviation from Fitts’s law when imagining movements—believing that movement duration increased with distance within the same index of difficulty. Participants did not behave similarly, however, in a perceptual version of the decision task. These results suggest that imagined movements and motor decisions are linked, but they are not always based on veridical representations of actual movement. To further probe the origin of individuals’ erroneous belief about movement duration, the final study of this thesis measured movement duration for movements made at speeds other than ‘as fast as possible’. Movements made at more natural movement speeds shared important similarities with decisions and imagined movements. This study suggests that the biases seen in naïve motor decisions might originate from participants considering movements for which they have more experience, such as target-directed movements made at a naturally-selected pace. Together, the findings presented in this thesis may help to identify the ways that motor decisions can deviate from optimal, suggesting how those decisions must change with practice to better accomplish a task.
386

&quot / high Precision Cnc Motion Control&quot

Ay, Gokce Mehmet 01 September 2004 (has links) (PDF)
This thesis focuses on the design of an electrical drive system for the purpose of high precision motion control. A modern electrical drive is usually equipped with a current regulated voltage source along with powerful motion controller system utilizing one or more micro-controllers and/or digital signal processors (DSPs). That is, the motor drive control is mostly performed by a dedicated digital-motion controller system. Such a motor drive mostly interfaces with its host processor via various serial communication protocols such as Profibus, CAN+, RS-485 etc. for the purpose of receiving commands and sending out important status/control signals. Considering that the motor drives lie at the heart of every (multi-axis) motion control system, the aim of this thesis is to explore the design and implementation of a conventional DC motor drive system suitable for most industrial applications that require precision and accuracy. To achieve this goal, various underlying control concepts and important implementation details are rigorously investigated in this study. A low power DC motor drive system with a power module, a current regulator and a motion controller is built and tested. Several design revisions on these subsystems are made so as to improve the overall performance of the drive system itself. Consequently, important &ldquo / know-how&rdquo / required for building high performance (and high power) DC motor drives is gained in this research.
387

Hierarchical error processing during motor control

Krigolson, Olave 26 September 2007 (has links)
The successful execution of goal-directed movement requires the evaluation of many levels of errors. On one hand, the motor system needs to be able to evaluate ‘high-level’ errors indicating the success or failure of a given movement. On the other hand, as a movement is executed the motor system also has to be able to correct for ‘low-level’ errors - an error in the initial motor command or change in the motor command necessary to compensate for an unexpected change in the movement environment. The goal of the present research was to provide electroencephalographic evidence that error processing during motor control is evaluated hierarchically. The present research demonstrated that high-level motor errors indicating the failure of a system goal elicited the error-related negativity, a component of the event-related brain potential (ERP) evoked by incorrect responses and error feedback. The present research also demonstrated that low-level motor errors are associated with parietally distributed ERP component related to the focusing of visuo-spatial attention and context-updating. Finally, the present research includes a viable neural model for hierarchical error processing during motor control.
388

Manual Motor Development in Infancy : Execution and Observation of Actions

Ljunghammar Ekberg, Therese January 2015 (has links)
Of all motor skills, manual reaching might be the one ability that matters most for infants’ perceptual, cognitive and social development. Reaching allows infants to learn about object properties, but also gives opportunities for socializing with others. The general aim of the present thesis was to study the importance of manual motor development in infancy from different perspectives; first, through examining stereopsis as a prerequisite for efficient reaching development, second, with regard to understanding others goal-directed reach actions by means of the mirror neuron system (MNS), and third, in relation to possible atypical development, with a specific focus on autism spectrum disorder (ASD). Study I shows that under monocular viewing conditions, infants at six, eight and 10 months of age perform slower and less accurate reaches. Longer times to object contact during monocular trials specifically imply that motor prediction is less effective when depth and distance information is compromised. Study II demonstrates that, by eight months of age, infants seem to have a MNS that functions in a similar manner to the adult MNS, thus activity can be registered over the motor cortex when infants simply observe an action they can master themselves. This activation is predictive, indicating anticipation of the goal of the observed reach. Study III indicates that infants at elevated familial risk for ASD present with reduced prospective motor control at 10 months of age. Compared to a low-risk control sample, high-risk infants perform reactive rather than predictive reach actions. Follow-up assessment at 36 months will show whether this measure can be used as a predictive diagnostic marker for ASD. The main contribution given by this work is the insight that it is important to take manual motor aspects into account when considering typical as well as atypical cognitive and social development, and in addition, that motor prediction is a key factor behind being able to timely execute and understand reaching actions.
389

Les dystonies focales : leurs dysfonctionnements sensori-moteurs et leurs conséquences sur l'organisation du mouvement / Focal dystonia : sensory-motor dysfunctions and consequences on the organization of movement

Bleton, Jean-Pierre 11 December 2015 (has links)
L’identification des muscles responsables des dystonies focales est un prérequis à l’instauration des traitements par toxine botulique et exercices correcteurs. A partir de deux dystonies apparemment dissemblables: la crampe de l’écrivain et la dystonie cervicale, nous avons montré que la réponse aux traitements est tributaire de la distribution des muscles impliqués. L’enregistrement des mouvements du segment tête-cou dans la dystonie cervicale , au moyen de capteurs inertiels 3-D, a montré qu’au mouvement volontaire de la tête, dans un plan, s’associent des mouvements non physiologiques dans les deux autres plans. Pour déterminer les actions musculaires en cause, nous avons réalisé une modélisation numérique du segment tête-cou permettant d’associer le muscle responsable aux déformations. Par ailleurs, sachant l’importance des phénomènes sensitifs dans le contrôle du mouvement, nous avons, au cours de tâches d’ajustement de la force musculaire, montré que ce contrôle de la force est perturbé dans chacune des deux dystonies focales étudiées.Nos résultats devraient avoir une implication dans les traitements symptomatiques de ces dystonies. / The identification of the muscles responsible for focal dystonia is a prerequisite to the introduction of botulinum toxin treatment and tailored exercises. From two apparently dissimilar dystonia: writer's cramp and cervical dystonia, we showed that the response to the treatments depends on the distribution of the muscles involved. Recording the movement of the head-neck segment in cervical dystonia, using 3-D inertial sensors, showed that voluntary head movement in a plane is associated with non-physiological movement in the two other planes. To determine the muscular actions involved, we performed a digital modeling of the head-neck segment which allows us to link the responsible muscle with abnormal postures.Therefore, knowing the importance of sensory phenomena in the control of movement, we have, during tasks of muscular force adjustment, demonstrated that force control is altered in both studied dystonia.Our results should have implications in the symptomatic treatment of these dystonias.
390

Contrôle de la production de la parole chez l’enfant de 4 ans : l'anticipation comme indice de maturité motrice / Speech motor control in 4-year-old children : anticipation as an index of speech motor control maturity

Barbier, Guillaume 08 September 2016 (has links)
Ce travail de thèse étudie la production de la parole à l'âge de 4 ans, en comparaison avec l'adulte, sous l'angle du contrôle moteur. Un intérêt particulier a été porté à deux indices : la variabilité liée à la répétition de voyelles isolées et la coarticulation anticipatoire intra et extra-syllabique dans le cadre de la production de séquences de type V1-C-V2. Des données acoustiques et articulatoires ont été enregistrées via l'échographie linguale et le dispositif HOCUS. Les données acoustiques ont été analysées pour 20 enfants et 10 adultes et les données articulatoires ont été analysées pour 6 de ces enfants et 2 de ces adultes. En accord avec de nombreuses études de la littérature, la variabilité liée à la répétition est plus importante chez les enfants que chez les adultes. Une forte anticipation de V2 dans la réalisation de V1 a été observée pour tous les adultes. Chez les enfants, cette anticipation n'est pas systématique, et lorsqu'elle est observée, elle est d'amplitude plus faible que chez les adultes. Ainsi, seulement 5 enfants parmi les 20 étudiés montrent des signes d'anticipation, majoritairement dans la dimension antéropostérieure, manifestée dans l'espace acoustique par la dimension F2. La coarticulation anticipatoire intra-syllabique semble également être d'amplitude plus faible chez les enfants. Enfin, les gestes de parole des enfants sont plus lents que ceux des adultes. Dans leur ensemble, ces résultats sont interprétés comme la preuve de l'immaturité du système moteur pour la production de la parole chez l'enfant, selon deux perspectives : des patrons moteurs insuffisamment stables pour la production de gestes vocaliques et un manque d'efficacité dans l'anticipation les gestes futurs lors de la production d'une séquence de sons de parole. Selon une perspective empruntée aux théories du contrôle moteur optimal, nous proposons que la coarticulation anticipatoire repose sur l'usage de modèles internes, représentations sensori-motrices du système moteur de la parole dans le système nerveux central, et que son amplitude reflète la maturation progressive de ces représentations sensori-motrices à mesure que la production de la parole se développe. / This thesis work investigates speech production in 4-year-old children, in comparison with adults, from a speech motor control perspective. It focuses on two indices: measures of token-to-token variability in the production of isolated vowels and on anticipatory intra and extra-syllabic coarticulation within V1-C-V2 sequences. Acoustic and articulatory data were recorded thanks to ultrasound tongue imaging within the HOCUS system. Acoustic data from 20 children and 10 adults have been analyzed. Ultrasound data have been analyzed from a subset of these participants: 6 children and 2 adults. In agreement with former studies, token-to-token variability was greater in children than in adults. Strong anticipation of V2 in V1 realization was found in all adults. In children, anticipation was not systematic, and when observed, it was of smaller amplitude than in adults. In more details, only 5 children among the 20 studied showed a small amount of anticipation, mainly along the antero-posterior dimension, manifested in the acoustic F2 dimension. Anticipatory intra-syllabic coarticulation also seems to be of smaller amplitude in children than in adults. Last, children's speech gestures are slower than those of adults. These results are interpreted as evidence for the immaturity of children's speech motor control from two perspectives: insufficiently stable motor control patterns for vowel production, and a lack of effectiveness in anticipating forthcoming gestures. In line with theories of optimal motor control, we assume that anticipatory coarticulation is based on the use of internal models, i.e. sensori-motor representations of the speech production apparatus in the central nervous system, and that the amplitude of anticipatory coarticulation reflects the increasing maturation of these sensori-motor representations as speech develops.

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