Dissertations / Theses on the topic 'Motor Redundancy'

Je jasné, že nejúspěšnější konstrukce zahrnuje postup vícefázového řízení, ve kterém každá fáze může být považována za samostatný modul. Provoz kterékoliv z jednotek musí mít minimální vliv na ostatní, a to tak, že v případě selhání jedné jednotky ostatní mohou být v provozu neovlivněny. Modulární řešení vyžaduje minimální elektrické, magnetické a tepelné ovlivnění mezi fázemi řízení (měniče). Synchronní stroje s pulzním tokem a permanentními magnety se jeví jako atraktivní typ stroje, jejíž přednostmi jsou vysoký kroutící moment, jednoduchá a robustní konstrukce rotoru a skutečnost, že permanentní magnety i cívky jsou umístěny společně na statoru. FS-PMSM jsou poměrně nové typy střídavého stroje stator-permanentní magnet, které představují významné přednosti na rozdíl od konvenčních rotorů - velký kroutící moment, vysoký točivý moment, v podstatě sinusové zpětné EMF křivky, zároveň kompaktní a robustní konstrukce díky umístění magnetů a vinutí kotvy na statoru. Srovnání výsledků mezi FS-PMSM a klasickými motory na povrchu upevněnými PM (SPM) se stejnými parametry ukazuje, že FS-PMSM vykazuje větší vzduchové mezery hustoty toku, vyšší točivý moment na ztráty v mědi, ale také vyšší pulzaci díky reluktančnímu momentu. Pro stroje buzené permanentními magnety se jedná o tradiční rozpor mezi požadavkem na vysoký kroutící moment pod základní rychlostí (oblast konstantního momentu) a provozem nad základní rychlostí (oblast konstantního výkonu), zejména pro aplikace v hybridních vozidlech. Je předložena nová topologie synchronního stroje s permanentními magnety a spínaným tokem odolného proti poruchám, která je schopná provozu během vinutí naprázdno a zkratovaného vinutí i poruchách měniče. Schéma je založeno na dvojitě vinutém motoru napájeném ze dvou oddělených vektorově řízených napěťových zdrojů. Vinutí jsou uspořádána takovým způsobem, aby tvořila dvě nezávislé a oddělené sady. Simulace a experimentální výzkum zpřesní výkon během obou scénářů jak za normálního provozu, tak za poruch včetně zkratových závad a ukáží robustnost pohonu za těchto podmínek. Tato práce byla publikována v deseti konferenčních příspěvcích, dvou časopisech a knižní kapitole, kde byly představeny jak topologie pohonu a aplikovaná řídící schémata, tak analýzy jeho schopnosti odolávat poruchám.

Cette thèse aborde principalement trois grands aspects tels que la systématisation et l'analyse structurale, la modélisation géométrique et cinématique et les stratégies de contrôle. La première partie de la thèse est consacrée à l'élaboration d'une approche pour la systématisation des mécanismes reconfigurables selon leurs paramètres structuraux tels que la mobilité, la connectivité, la redondance et l’hyperstatisme. Ces paramètres nous permettent de comprendre les mécanismes et de les systématiser selon leur type de mouvement ; le mécanisme peut être isostatique ou hyperstatique, redondant ou non-redondant, avec ou sans mobilités internes, etc. Afin de résoudre les problèmes pratiques de modélisation, contrôle, simulation et développement du robot, les paramètres structuraux sont nécessaires. Différents types de singularités sont systématisés et analysés en tenant compte de paramètres structuraux. En plus, pour connaître les positions et les orientations relatives des membres du robot, nous avons besoin de calculer le modèle géométrique. Nous utilisons la méthode du Système de Coordonnées Voyageur pour déterminer la position et l'orientation des membres à chaque instant. Pour connaître les vitesses linéaires et angulaires des membres, nous devons formuler les équations cinématiques pour le robot étudié. La partie contrôle est dédiée à l'élaboration de stratégies de génération de trajectoire et de contrôle, sur la base de la redondance d’actionnement. La difficulté dans la commande est de développer une loi de contrôle avancée pour la synchronisation de plusieurs actionneurs afin d'avoir une transition fluide d'un mode d'assemblage à un autre, ceci sans endommager le robot. Le choix des liaisons actionnées joue également un rôle essentiel en garantissant une haute performance et la contrôlabilité du mécanisme au passage par les configurations singulières. Dans cette thèse, nous nous concentrons sur le mécanisme à une seule boucle fermée de type 8-bar afin d’illustrer les développements réalisés dans les trois parties mentionnées ci-dessus. Il a été démontré que ce mécanisme présente une capacité intéressante de reconfiguration. Il dispose de deux degrés de mobilité dans une configuration générale, mais a besoin d'au moins cinq moteurs pour être entièrement contrôlés dans toutes les configurations singulières<br>This thesis mainly addresses three major aspects such as systematization and structural analysis, geometric and kinematic formulation and control strategies. The first part of the thesis is dedicated to the development of a systematization approach for reconfigurable mechanisms with respect to their structural parameters such as mobility, connectivity, redundancy and number of overconstraints. These parameters help us to understand the mechanism and to systematize it according to type of motion, whether the mechanism is overconstrained or non-overconstraint, redundant or non-redundant, with/without internal mobilites, etc. To resolve the practical problems of modeling, control, simulation and development of the robot, the structural parameters are required. Various types of singularities are also systematized and analyzed by taking into account the structural parameters. Further to know the relative location of robot links, we need to compute the geometric model. We use Travel Coordinate System method to determine the position and orientation of links at each instant. To find out the linear and angular velocities of links, we need to formulate the kinematic equations for the robot under consideration. The control part is dedicated to the development of trajectory generation and control strategies, based on actuation redundancy. The challenging task is to develop an advanced control law in order to synchronize several actuators to have a smooth transition from one assembly mode to another without causing wear and tear to the robot. Choice of actuated joints also plays a vital role in ensuring high performance and controllability of the mechanism when crossing singular configurations. In this thesis we focus on the 8-bar single loop mechanism to illustrate the developments achieved in the three parts mentioned above. It has been shown that, this mechanism exhibits an interesting capacity to reconfigure. It has two degrees of mobility in a general configuration but needs at least five motors to be fully controlled in all singular configurations

Human sensorimotor control can achieve highly reliable movements under circumstances of noise, redundancy, uncertainty, and sensory delays. Our ability to achieve reliable and accurate movements is in the fact we have a nervous system that learns these limitations and continuously compensates for them. The purpose of the thesis is to understand brain mechanisms and computations underlying supervised motor learning, its interaction with reinforcement learning and study its relation to motor variability. To address these issues, we have investigated factors influencing supervised motor learning such as neurological disease condition, the role of the reinforcement signal, motor variability and motor redundancy. Traditionally, supervised or error-based learning and reinforcement or reward based learning are thought to be occurring at anatomically different places and have functionally separate mechanisms. By leveraging the performance of human patients with Parkinson disease and cerebellar ataxia disease, we demonstrate how the presence and absence of dopamine medication and subthalamic deep brain stimulation (STN-DBS) influenced supervised learning. Furthermore, we also show that the presence and absence of reinforcement at the end of the trial profoundly affected learning such that the difference in learning as a consequence of medication reduced significantly. These results suggest that the basal ganglia modulate the gain of supervised learning in the cerebellum based on the reinforcement received at the end of the trial. Furthermore, we explored motor variability (thought to be an unwanted characteristic of the motor system) and investigated its significance and effect on supervised motor learning. We propose that some part of motor variability arises out of the redundancy in the joints in the human arm. We showed that greater uses of redundancy in the arm lead to faster learning across healthy subjects. We observed these both in dynamic perturbation learning and kinematic perturbation learning. Interestingly, we also found differences in the use of redundancy between the dominant hand and non-dominant hand, suggesting that the nervous system actively controls the redundancy. Furthermore, we also observed some directions in reaching are difficult to learn in comparison to others directions. To understand such behavior, we separated direction wise errors and constructed errors ellipses and found out that eccentricity of ellipse change with learning, which suggests brain while reducing errors in learning, is also trying to homogenize the distribution of errors caused by the perturbation. We also found interesting differences between redundancy and motor learning that was selectively impaired in PD patients but not cerebellar patients, possibly pointing to a role of the basal ganglia in processing of the use of redundancy in motor learning. In summary, the results in the thesis provide experimental support for the hypothesis that the basal ganglia modulate the gain of supervised learning and exploration of redundancy aids in learning and that the redundancy component of the motor variability is not noise. In future, we hope that this relationship between basal ganglia, reinforcement, and redundancy in supervised motor learning can be leveraged to enhance motor rehabilitation and motor skills in patients with motor deficits.

Fault tolerant motor drives are becoming more important in safety critical applications. Although a single motor module fault tolerant drive may be sufficient in some applications, this motor drive only offers limited redundancy. This thesis investigated the dual motor module fault tolerant drive system in which two motor modules were connected electrically in phase and on a common shaft provide redundancy and to increase the reliability of the entire drive system. A general phase current mathematical model to produce the desired output torque was developed to minimize copper loss and torque ripple in the motor drive, which is applicable to both sinusoidal and trapezoidal brushless permanent magnet motor types. A detailed fault effect investigation was performed in this thesis and it is concluded that switch short-circuit fault is the most serious fault since it reduces the electromagnetic torque output significantly and generates larger torque ripple in the motor drive due to the presence of large drag torque. Three fault remedial strategies were proposed to compensate the torque loss and to reduce the torque ripple under different faulty conditions. It is concluded from the analytical results that fault remedial strategy 3 is the tradeoff algorithm in which the zero torque ripple factor can be achieved with only a modest increase in copper loss comparing with the minimum possible value. Two practical dual motor module fault tolerant brushless permanent magnet drive test arrangements with different motor structures were developed in this thesis. The computer simulation studies using the MATLAB Simulink were performed to verify the effectiveness of the proposed fault remedial strategies. The efficiency of the motor drive was predicted based on torque loss measurements and the results were verified in the simulation study. The effect of faults on the drive efficiency was investigated as well. The entire fault tolerant motor drive control system was also developed to verify the analytical and simulation results. A fault detection and identification method to detect switch open-circuit faults, switch short-circuit faults, and the winding short-circuit faults was also proposed. Its advantages are the simplicity of the implementation and reduction of the cost of the drive system. The experimental results demonstrated that the proposed fault remedial strategies can be implemented in real time motor control and are effective to compensate the torque loss and reduce the torque ripple.<br>Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2008

Fault tolerant motor drives are becoming more important in safety critical applications. Although a single motor module fault tolerant drive may be sufficient in some applications, this motor drive only offers limited redundancy. This thesis investigated the dual motor module fault tolerant drive system in which two motor modules were connected electrically in phase and on a common shaft provide redundancy and to increase the reliability of the entire drive system. A general phase current mathematical model to produce the desired output torque was developed to minimize copper loss and torque ripple in the motor drive, which is applicable to both sinusoidal and trapezoidal brushless permanent magnet motor types. A detailed fault effect investigation was performed in this thesis and it is concluded that switch short-circuit fault is the most serious fault since it reduces the electromagnetic torque output significantly and generates larger torque ripple in the motor drive due to the presence of large drag torque. Three fault remedial strategies were proposed to compensate the torque loss and to reduce the torque ripple under different faulty conditions. It is concluded from the analytical results that fault remedial strategy 3 is the tradeoff algorithm in which the zero torque ripple factor can be achieved with only a modest increase in copper loss comparing with the minimum possible value. Two practical dual motor module fault tolerant brushless permanent magnet drive test arrangements with different motor structures were developed in this thesis. The computer simulation studies using the MATLAB Simulink were performed to verify the effectiveness of the proposed fault remedial strategies. The efficiency of the motor drive was predicted based on torque loss measurements and the results were verified in the simulation study. The effect of faults on the drive efficiency was investigated as well. The entire fault tolerant motor drive control system was also developed to verify the analytical and simulation results. A fault detection and identification method to detect switch open-circuit faults, switch short-circuit faults, and the winding short-circuit faults was also proposed. Its advantages are the simplicity of the implementation and reduction of the cost of the drive system. The experimental results demonstrated that the proposed fault remedial strategies can be implemented in real time motor control and are effective to compensate the torque loss and reduce the torque ripple.<br>Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2008

Motor noise and redundancy are vexing issues in motor control; yet their understanding provides great insights on underlying control mechanisms that govern movement. They provide glimpses into how the nervous system organizes and regulates movement within the motor control system. Understand of motor control could spur new advances in motor control could lead to better development of rehabilitation process and technology to counteract debilitating affects of neuromuscular disorders and motor readjustment with prostheses. However, before such process and technology could be developed and adapted for clinical use, a deeper understanding of motor control is needed to unravel the neural roadmap that regulates and generates movement. New theory of motor control could precipitate the development of more robust control mechanisms for robotic-human interaction. This work aims at expanding a more rigorous analytical and mathematical framework to understand how these control mechanisms reconcile redundancy and stochastic noise in human motor control.<br>text

Trial-to-trial variability in human movement is often overlooked and averaged out, but useful information can be gleaned on the brain’s control of variability. A task can be defined by a function specifying a solution manifold along which all task variable combinations will lead to goal success – the Goal-Equivalent Manifold (GEM). We selected a reaching task with variables reach Distance (D) and reach Time (T). Two GEMs were selected: a constant D/T and constant D×T. Subjects had no knowledge of the goal prior to the experiments and were instructed only to minimize error. Subjects learned the generalized tasks by reducing errors and consolidated learning from one day to the next, generalized learning from the D×T to the D/T GEM, and had interference of learning from the D/T to the D×T GEM. Variability was structured along each GEM significantly more than perpendicular to it. Deviations resulting in errors were corrected significantly more quickly than any other deviation. Our results indicate that subjects can learn generalized reaching tasks, and the brain exploits redundancy in those tasks.<br>text

Lo scopo principale di questa dissertazione è di comprendere in maniera più approfondita il controllo dinamico della postura nel movimento umano. In particolare, qui ci approcciamo al problema prendendo in considerazione differenti compiti motori e analizzando differenti popolazioni in tre studi diversi. Nel primo viene presa in considerazione l’azione motoria della salita delle scale. In questo esperimento le popolazioni testate erano giovani ed anziani e lo scopo principale era di comprendere se ci sono differenti strategie posturali e percettive sia durante la pianificazione che durante l’esecuzione del movimento a causa della diminuzione del livello di capacità motorie. Gli altri due studi invece focalizzano più l’attenzione sullo sviluppo degli aggiustamenti posturali, prima e durante l’azione motoria, quando le capacità motorie raggiungono livelli ottimali di prestazione. In questi ultimi due casi le popolazioni prese in considerazione erano atleti di alto livello in cui essi primeggiano nell’azione da loro eseguita nell’esperimento, per cui di conseguenza lo scopo di questi studi era di spiegare come l’alta prestazione emerge in specifiche sinergie muscolari causate dall’esperienze motoria degli atleti. Anche se i tre esperimenti hanno in comune il controllo dinamico della postura, differenti modelli teorici del controllo motorio ispirano ciascuno di essi. Da una parte ci riferiamo al concetto di “equifinalità” formulata da Nicolay Bernstein (1967) e al concetto di “affordance” formulata da J.J. Gibson (1979). Queste due idee prese insieme ispirano il primo studio presentato. Dall’altra parte, la legge formulata da Paul Fitts (1954) ispira gli ultimi due esperimenti. Nel’introduzione presenteremo in sequenza queste idee e i loro relativi modelli: per prima l’equifinalità, seguendo l’affordance e poi la legge di Fitts. Per cui questi tre concetti teorici verranno applicati al controllo dinamico della postura, e un capitolo finale affronterà i modo dettagliato l’argomento riguardante il controllo posturale. Successivamente verranno presentati i tre esperimenti.<br>The main aim of this dissertation is to obtain a deeper understanding about the dynamics of postural control in human movement. In particular here we approach the problem by including several motor tasks and by testing different populations in three separate studies. The first one deals with the action of climbing stairs. In this experiment the populations tested were old and young adults and the main aim was to reveal whether there are different perceptive/motor postural strategies either for planning as well as for executing the action due to the decrease of the level of motor skill. The other two studies instead focalize more the attention on the development of postural adjustments, before and during the action performance, when the level of motor skill reaches its optimality. In these latter two cases the populations tested were elite athletes performing actions in which they excel, and as a consequence the aim of these studies was to reveal how excellence merges from the developments of specific muscular synergies due to practice. Even though the three experiments share issues related to the dynamics of postural control, different models and theoretical frameworks inspire each one. On the one hand, we refer to the concept of movement “equifinality” formulated by Nicolay Bernstein (1967) and to the concept of “affordance” formulated by J.J. Gibson (1979). These two ideas taken together inspired the first study presented. On the other hand, the law formulated by Paul Fitts (1954) inspired the latter two experiments. In the introduction we will present in sequence these ideas and their relative models: first equifinality, followed by affordance, and then Fitts’ law. Since these three theoretical concepts are applied to the dynamics of postural control, a final chapter will discuss more in depth issues related to the control of posture. Then the three experiments will be presented.

Indiana University-Purdue University Indianapolis (IUPUI)<br>This research proposes state-of-the-art multilevel converter topologies and their modulation strategies, the implementation of a conventional flying-capacitor converter topology up to four-level, and a new four-level flying-capacitor H-Bridge converter confi guration. The three phase version of this proposed four-level flying-capacitor H-Bridge converter is given as well in this study. The highlighted advantages of the proposed converter are as following: (1) the same blocking voltage for all switches employed in the con figuration, (2) no capacitor midpoint connection is needed, (3) reduced number of passive elements as compared to the conventional solution, (4) reduced total dc source value by comparison with the conventional topology. The proposed four-level capacitor-clamped H-Bridge converter can be utilized as a multilevel inverter application in an electri fied railway system, or in hybrid electric vehicles. In addition to the implementation of the proposed topology in this research, its experimental setup has been designed to validate the simulation results of the given converter topologies.