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Dissertations / Theses on the topic 'Electromechanical simulation'
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1
Konstandin, Alexander. "Simulation of the constitutive behavior of PZT ceramics under electromechanical loading." Aachen Shaker, 2008. http://d-nb.info/989363090/04.
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Kirk, Nathan Robert. "An adaptive, preconditioned, electromechanical model for the simulation of cardiac arrhythmias." Thesis, University of Leeds, 2012. http://etheses.whiterose.ac.uk/2865/.
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In this thesis a coupled model of cardiac electromechanical activity is presented, using the finite element method to model both electrophysiology and mechanics within a deforming domain. The efficiency of the electrical model was improved using adaptive mesh refinement and the mechanical system performance was improved with the addition of preconditioning. Unstructured triangular meshes were used throughout. The electrophysiology model uses the ten Tusscher-Panfilov 2006 detailed cellular model, and includes anisotropic diffusion, uses a semi-implicit time stepping scheme, stores data in an efficient sparse storage format and applies a Reverse Cuthill-McKee ordering algorithm to reduce the matrices’ bandwidths. Linear elements were used to approximate the transmembrane voltage and spatial and temporal convergence tests were undertaken. Local mesh adaptivity is added to the electrical component of the model and improvements to the performance and efficiency gained by this technique were investigated. Two different monitor functions were utilised and these demonstrated that by targeting adaptive mesh refinement at the front of the electrical wave significant efficiency and performance benefits could be achieved. The cardiac mechanical model is based on finite deformation elasticity theory, enforces the incompressibility of the tissue and incorporates anisotropic tension to simulate fibre orientation. This uses isoparametric quadratic elements for deformation, linear elements for pressure, was integrated with numerical quadrature and the resulting non-linear system solved with the iterative Newton method. Preconditioning was added to the mechanical component of the model and improvements in the performance of the solver due to this were investigated. An ILUT (Incomplete Lower Upper factorisation with drop Tolerance) preconditioner was implemented and this demonstrated performance improvements of up to 27 times on the meshes tested. The resulting cardiac electromechanical solver was then used to consider how known changes in cardiac electrophysiology, which are manifest in end-stage heart disease, affect the stability of the electrical wave. Specifically, investigations were undertaken into the introduction of fibrotic regions (with different sizes and concentrations) and electrical remodelling caused by end-stage cardiac disease. These were modelled on both static and deforming domains to consider whether deformation can alter the stability of a spiral wave. These simulations demonstrated that fibrotic regions and tissue deformation can have significant disruptive effects on the stability of a re-entrant spiral wave and that remodelling the electrophysiology stabilises the wave.
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Zhai, Pei. "The hybrid real-time simulation system based on the electromechanical transient process simulation of power systems." Thesis, University of Macau, 2007. http://umaclib3.umac.mo/record=b1678026.
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Leichsenring, Peter, and Thomas Wallmersperger. "Time-dependent chemo-electromechanical behavior of hydrogelbased structures." SPIE, 2018. https://tud.qucosa.de/id/qucosa%3A35174.
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Charged hydrogels are ionic polymer gels and belong to the class of smart materials. These gels are multiphasic materials which consist of a solid phase, a fluid phase and an ionic phase. Due to the presence of bound charges these materials are stimuli-responsive to electrical or chemical loads. The application of electrical or chemical stimuli as well as mechanical loads lead to a viscoelastic response. On the macroscopic scale, the response is governed by a local reversible release or absorption of water which, in turn, leads to a local decrease or increase of mass and a respective volume change.
Furthermore, the chemo-electro-mechanical equilibrium of a hydrogel depends on the chemical composition of the gel and the surrounding solution bath. Due to the presence of bound charges in the hydrogel, this system can be understood as an osmotic cell where differences in the concentration of mobile ions in the gel and solution domain lead to an osmotic pressure difference.
In the present work, a continuum-based numerical model is presented in order to describe the time-dependent swelling behavior of hydrogels. The numerical model is based on the Theory of Porous Media and captures the fluid-solid, fluid-ion and ion-ion interactions. As a direct consequence of the chemo-electro-mechanical equilibrium, the corresponding boundary conditions are defined following the equilibrium conditions. For the interaction of the hydrogel with surrounding mechanical structures, also respective jump condtions are formulated. Finaly, numerical results of the time-dependent behavior of a hydrogel-based chemo-sensor will be presented.
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Liang, Darwin Tat Wai. "Simulation and analysis of induction motor drive systems." Thesis, Heriot-Watt University, 1993. http://hdl.handle.net/10399/1427.
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Choi, Hong Fei. "Numerical simulation of atrium fire using two CFD tools." Thesis, University of Macau, 2007. http://umaclib3.umac.mo/record=b1694321.
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Li, Jian. "Implementation and simulation of various vector controlled induction motor drives." Thesis, University of Aberdeen, 1995. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU083755.
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The development of AC drives has gained momentum with the advancement of power electronic devices, control theory and technology of microprocessors. Based on high speed digital signal processing theory and power transistor hardware, two axis machine model and adaptive control techniques, a vector controlled fully digital induction motor drive is a high performance, low cost drive which is becoming increasingly popular in many industrial applications in all power ranges and will succeed the dc drive in the near future. The main goal of the thesis is to investigate the various forms of implementations of vector controlled digital signal processor based high performance induction motor drives. For this purpose, a TMS320C30 digital signal processor board with transducer and interfacing circuits has been designed, manufactured and built. Furthermore a conventional bipolar transistor inverter has been modified and interfaced to the DSP board. The entire hardware has been tested and successfully implemented. The control software is versatile and provides a platform for implementing various control configurations. The first part of the thesis reviews the development of various vector controlled drives; different mathematical models are presented and discussed together with digital simulation results of different vector controlled schemes. Intelligent control algorithms based on neural networks, fuzzy control, self-tuning control are also considered, some of them are tested by using real-time simulation or on a real drive. Different PWM strategies are investigated and compared, and a versatile and reliable real-time PWM algorithm is generated and integrated into the drive control software. Various parameter identification and auto-commissioning techniques are included in the control software. Details of experimentally obtained results for various vector drives are presented.
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Konstandin, Alexander [Verfasser]. "Simulation of the Constitutive Behavior of PZT Ceramics under Electromechanical Loading / Alexander Konstandin." Aachen : Shaker, 2008. http://d-nb.info/1162792043/34.
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Donolo, Marcos A. "A continuum Approach to Power system simulation." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/29002.
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The behavior of large and tightly interconnected power systems resembles, in certain circumstances, the behavior of a continuously distributed system. This resemblance motivated the derivation of continuum models, which were used to explain and predict disturbance propagation, un-damped power oscillations, and the stability of power systems. In this dissertation, we propose a one-dimensional continuum representation suitable for meshed power systems. Previous continuous representations of meshed power systems used two-dimensional spatial domains. Thus our approach has the potential to provide better resolution for comparable computational burden. It is important to note that, the computational burden required to obtain solutions for PDEs involved in the continuum representation varies notably with the solver implementation.
The contributions of this dissertation are: a) Reviewing a previous continuum model and providing a detailed derivation for the one-dimensional version of it. b) Providing and describing in detail a parameter distribution technique adequate for the continuum approach. c) Identifying and documenting limitations on the continuum model voltage calculation. e) Providing a procedure to simulate the behavior of meshed power systems using the one dimensional continuum model. And f) Identifying and applying a numerical PDE solver for the continuum approach.<br>Ph. D.
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Rezaei-Lori, Ahmad Ali. "Design and simulation of brushless DC drive systems for industrial applications." Thesis, Cardiff University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336117.
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Huang, F. "On-line simulation of inverter-induction motor drives for rapid transit." Thesis, University of Bath, 1991. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292819.
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Frotscher, Ralf Verfasser], and Jörg [Akademischer Betreuer] [Schröder. "Electromechanical Modeling and Simulation of Thin Cardiac Tissue Constructs / Ralf Frotscher. Betreuer: Jörg Schröder." Duisburg, 2016. http://d-nb.info/1090785461/34.
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Safi, Sabah Kati. "Analysis and simulation of the high-speed torque performance of brushless D.C. motor drives." Thesis, University of Newcastle Upon Tyne, 1994. http://hdl.handle.net/10443/367.
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The work presented in this thesis is concerned with the analysis, modelling, simulation and control of a surface mounted permanent magnet motor supply by a voltage controlled Pulse-Width Modulation (PWM) inverter. In Chapter 1 an overall description of the design and construction of individual components of the brushless dc drive system is presented along with a review of the general concept of the drive system. This type of machine is compared with other types of machine and the potential advantages of this new concept, both technical and economic, outlined. In Chapter 2 the operation and the control aspects of the brushless dc motor are described, with particular emphasis placed on the basic requirements for the operation, torque production, performance characteristic and control. The high-speed torque control methods are also described and their merits are reviewed. In addition the effects of different parameters of machine design on the torque-speed characteristics are discussed. Chapter 3 elaborates on the analysis and simulation work by presenting a comprehensive analysis which aims to show that direct three-phase representation can be used as an effective tool for performance assessement of brushless dc drive systems operating over a wide speed range. In Chapter 4 the performance of the brushless dc motor supplied by a PWM inverter with a view to improving the high-speed torque performance is investigated. Simulation and analysis of the brushless dc motor is presented in which the actual parameters of the experimental machine are used. The aim of the analysis is to simulate a brushless d. c. drive system operating in closed-loop control modes, which use high speed torque control techniques in conjunction with a PWM control technique. A detailed analytical model which makes possible the use of machine theory for representing the performance of the brushless dc motor is presented in Chapter 5. The method utilizes the phasor diagram, where machine performance in terms of the main control variables such as voltage and phase advance angle is demonstrated. Chapter 5 also presents an analytical expression for the phase-advance angle which yields maximum torque at a given motor speed. An analytical study concerning the optimum phase advance is developed in Chapter 6. In this work two analytical approaches to the problem of obtaining an optimum phase advance angle are presented. Chapter 6 presents a detailed analysis of the shape of the current and back-emf waveforms in a trapezoidal brushless dc motor drive and their effects on the torque/speed performance. Chapter 7 presents the implementation of a microprocessor based system, which can set the phase advance angle to its optimum value at any motor speed. This implementation is done in real time on the protortype drive using a TMS320C30 digital signal processor. Features of the method proposed in this thesis include the estimation algorithms for predicting the time advance. Experimental results on a drive system demonstrate the satisfactory performance of both the hardware and software of the control scheme.
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Miller, Justin (Justin Lee). "Simulation of a novel electromechanical engine valve drive to quantify performance gains in fuel consumption." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67767.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 67-68).<br>This thesis describes the modeling and simulation of a novel electromechanical valve drive known as the MIT EMV. This valve drive allows an engine to achieve variable valve timing which has been shown to produce improvements in engine fuel efficiency. To test this improvement, a reference engine model with fixed valve timing was obtained from the engine simulation software package WAVE® by Ricardo. A model of the MIT EMV was generated based on the details of the physical actuator, and it was incorporated into the WAVE® engine model. An interface between MATLAB® and WAVE® was developed for simulating the actuator at desired engine speeds and loads. Specific test points were chosen based on corporate operating points and operating points that were used to test the BMW Valvetronic actuator. Through simulation, it was determined that the MIT EMV can provide a reduction of approximately 10% in fuel consumption at the corporate operating points when compared to the reference engine model. The drive was also able to achieve performance gains similar to the BMW Valvetronic actuator, showing that it is able to compete with other actuators on the market even without variable lift capabilities.<br>by Justin Miller.<br>S.M.
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Voyantzis, Mitchell D. "CloudMEMS Platform for Design and Simulation of MEMS: Physics Modules & End-to-End Testing." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1533226484963866.
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Mroue, Fatima. "Couplage Électromécanique du coeur : Modélisation, analyse mathématique et simulation numérique." Thesis, Ecole centrale de Nantes, 2019. http://www.theses.fr/2019ECDN0039/document.
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Cette thèse est dédiée à l'analyse mathématique et la simulation numérique des équations intervenant dans la modélisation de l’électrophysiologie cardiaque. D'abord, nous donnons une justification mathématique rigoureuse du processus d’homogénéisation périodique à l’aide de la méthode d'éclatement périodique. Nous considérons des conductivités électriques tensorielles qui dépendent de l’espace et des modèles ioniques non linéaires physiologiques et phénoménologiques. Nous montrons l'existence et l'unicité d’une solution du modèle microscopique en utilisant une approche constructive de Faedo- Galerkin suivie par un argument de compacité dans L2. Ensuite, nous montrons la convergence de la suite de solutions du problème microscopique vers la solution du problème macroscopique. À cause des termes non linéaires sur la variété oscillante, nous utilisons l’opérateur d’éclatement sur la surface et un argument de compacité de type Kolmogorov pour les modèles phénoménologiques et de type Minty pour les modèles physiologiques. En outre, nous considérons le modèle monodomaine couplé au modèle physiologique de Beeler-Reuter. Nous proposons un schéma volumes finis et nous analysons sa convergence. D'abord, nous dérivons la formulation variationnelle discrète correspondante et nous montrons l'existence et l'unicité de sa solution. Par compacité, nous obtenons la convergence de la solution discrète. Comme le schéma TPFA (two point flux approximation) est inefficace pour approcher les flux diffusifs avec des tenseurs anisotropes, nous proposons et analysons, ensuite, un schéma combiné non-linéaire qui préserve le principe de maximum. Ce schéma est basé sur l’utilisation d’un flux numérique de Godunov pour le terme de diffusion assurant que les solutions discrètes soient bornées sans restriction sur le maillage du domaine spatial ni sur les coefficients de transmissibilité. Enfin, dans la perspective d'étudier la solvabilité des modèles électromécaniques couplés avec des modèles ioniques physiologiques, nous considérons un modèle avec une description linéarisée de la réponse élastique passive du tissu cardiaque, une linéarisation de la contrainte d'incompressibilité et une approximation tronquée des diffusivités non linéaires intervenant dans les équations du modèle bidomaine. La preuve utilise des approximations par des systèmes non-dégénérés et la méthode Faedo-Galerkin suivie par un argument de compacité<br>This thesis is concerned with the mathematical analysis and numerical simulation of cardiac electrophysiology models. We use the unfolding method of homogenization to rigorously derive the macroscopic bidomain equations. We consider tensorial and space dependent conductivities and physiological and simplified ionic models. Using the Faedo-Galerkin approach followed by compactness, we prove the existence and uniqueness of solution to the microscopic bidomain model. The convergence of a sequence of solutions of the microscopic model to the solution of the macroscopic model is then obtained. Due to the nonlinear terms on the oscillating manifold, the boundary unfolding operator is used as well as a Kolmogorov compactness argument for the simplified models and a Minty type argument for the physiological models. Furthermore, we consider the monodomain model coupled to Beeler- Reuter's ionic model. We propose a finite volume scheme and analyze its convergence. First, we show existence and uniqueness of its solution. By compactness, the convergence of the discrete solution is obtained. Since the two-point flux approximation (TPFA) scheme is inefficient in approximating anisotropic diffusion fluxes, we propose and analyze a nonlinear combined scheme that preserves the maximum principle. In this scheme, a Godunov approximation to the diffusion term ensures that the solutions are bounded without any restriction on the transmissibilities or on the mesh. Finally, in view of adressing the solvability of cardiac electromechanics coupled to physiological ionic models, we considered a model with a linearized description of the passive elastic response of cardiac tissue, a linearized incompressibility constraint, and a truncated approximation of the nonlinear diffusivities appearing in the bidomain equations. The existence proof is done using nondegenerate approximation systems and the Faedo-Galerkin method followed by a compactness argument
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Ghorbel, Salma. "Couplage électromécanique effectif dans les structures piézoélectriques : expérimentations, simulations et corrélations." Phd thesis, Ecole Centrale Paris, 2009. http://tel.archives-ouvertes.fr/tel-00453865.
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Le coefficient de couplage électromécanique (CCEM) est un paramètre essentiel pour la description des matériaux piézoélectriques, il traduit la conversion d'énergie électrique en énergie mécanique et vice versa. Ce coefficient de couplage est étudié et déterminé dans le cadre de cette thèse pour des céramiques piézoélectriques. Ces dernières sont utilisées pour trois structures différentes ; la première structure étudiée est constituée d'une poutre longue et mince avec des petits patchs collés symétriquement sur les deux faces de la poutre en Aluminium, la seconde structure se compose d'une poutre courte et épaisse avec deux grands patchs. La dernière structure étudiée est une plaque composite multicouche du type aéronautique avec un seul grand patch. Ces trois structures ont été étudiées afin de déterminer le coefficient de couplage électromécanique effectif qui est considéré comme un indicateur de performance de l'amortissement passif shunté. Ce coefficient de couplage a été évalué de différentes manières en utilisant différents paramètres dont les conditions limites électriques, les propriétés élastiques des patchs, les propriétés modales de la poutre seule ainsi que les facteurs de couplages piézoélectriques. Une première étude expérimentale a été menée sur la poutre longue pour deux types de configurations en court circuit et circuit ouvert pour identifier ses propriétés modales. La poutre longue a été simulée pour deux types de polarisations, identiques et opposées, et simulée dans les deux codes Ansys® et Abaqus®. L'influence de la condition d'équipotentielle sur le coefficient de couplage a été étudiée. Une seconde campagne expérimentale et numérique sur une autre structure a été nécessaire pour valider les résultats obtenus. Pour pouvoir atteindre cet objectif, il était nécessaire de travailler sur une structure plus courte et plus rigide. Ainsi, la poutre courte a été simulée dans Ansys® et les résultats obtenus ont confirmé la nécessité de prendre en compte l'équipotentialité sur les faces des patchs. Cette condition a pour effet de réduire le couplage électromécanique et parfois de découpler certains modes. L'écart résultant de la corrélation expérimentale / numérique des deux poutres instrumentées a incité à recaler les modèles numériques. Ce recalage peut se présenter sous trois formes : mécanique en remplaçant l'encastrement par des ressorts linéaires, électrique en remplaçant les capacités fournies par le fabricant par les valeurs mesurées expérimentalement et électromécanique en utilisant les deux recalages précédents simultanément. Les deux poutres ont ensuite été simulées en déformations planes et contraintes planes et recalées afin d'approcher les résultats expérimentaux. L'étude de ces deux structures a permis de confronter les différentes méthodes d'évaluation du CCEM effectif, d'évaluer l'influence de l'équipotentialité sur les faces des électrodes et de comparer les simulations bidimensionnelles aux tridimensionnelles. Une plaque composite multicouche du type aéronautique a été ensuite étudiée pour généraliser la méthode d'évaluation du CCEM effectif pour les structures minces composites. La plaque seule a d'abord été simulée dans Ansys® pour valider le modèle numérique. Des tests sur la structure adaptative ont ensuite été menés pour l'évaluation du CCEM expérimental. La position choisie du patch a été déterminée par une analyse de l'énergie de déformation de la plaque seule pour les modes d'intérêt. Cette méthode de placement du patch s'est avérée efficace dans le sens où elle a conduit à des CCEM effectifs élevés pour certains modes de la bande de fréquence retenue.
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Rossander, Morgan. "Electromechanics of Vertical Axis Wind Turbines." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-331844.
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Wind power is an established mean of clean energy production and the modern horizontal axis wind turbine has become a common sight. The need for maintenance is high and future wind turbines may need to be improved to enable more remote and offshore locations. Vertical axis wind turbines have possible benefits, such as higher reliability, less noise and lower centre of gravity. This thesis focuses on electromechanical interaction in the straight bladed Darrieus rotor (H-rotor) concept studied at Uppsala University. One of the challenges with vertical axis technology is the oscillating aerodynamic forces. A force measurement setup has been implemented to capture the forces on a three-bladed 12 kW open site prototype. The normal force showed good agreement with simulations. An aerodynamic torque could be estimated from the system. The total electrical torque in the generator was determined from electrical measurements. Both torque estimations lacked the expected aerodynamic ripple at three times per revolution. The even torque detected is an important result and more studies are required to confirm and understand it. The force measurement was also used to study the loads on the turbine in parked conditions. It was discovered that there is a strong dependence on wind direction and that there is a positive torque on the turbine at stand still. The results can assist to determine the best parking strategies for an H-rotor turbine. The studied concept also features diode rectification of the voltage from the permanent magnet synchronous generator. Diodes are considered a cheap and robust solution for rectification at the drawback of inducing ripple in the torque and output voltage. The propagation of the torque ripple was measured on the prototype and studied with simulations and analytical expressions. One key conclusion was that the mechanical driveline of the turbine is an effective filter of the diode induced torque ripple. A critical speed controller was implemented on the prototype. The controller was based on optimal torque control and according to the experiments and the simulations it was able to avoid a rotational speed span. Finally, the optimal torque control was evaluated for multiple turbines with diode rectification to a common DC-link. The setup can potentially reduce the overall complexity of wind farms. The simulations suggest that stability of the system can be obtained by controlling the DC-link load as a semi constant voltage. The thesis is based on nine papers of which six are treated in the thesis summary.
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Tao, Ran. "Piezoelectric generators based on semiconducting nanowires : simulation and experiments." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAT094/document.
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L’alimentation en énergie des réseaux de capteurs miniaturisés pose une question fondamentale, dans la mesure où leur autonomie est un critère de qualité de plus en plus important pour l’utilisateur. C’est même une question cruciale lorsque ces réseaux visent à assurer une surveillance d’infrastructure (avionique, machines, bâtiments…) ou une surveillance médicale ou environnementale. Les matériaux piézoélectriques permettent d’exploiter l’énergie mécanique inutilisée présente en abondance dans l’environnement (vibrations, déformations liées à des mouvements ou à des flux d’air…). Ils peuvent ainsi contribuer à rendre ces capteurs autonomes en énergie. Sous la forme de nanofils (NF), les matériaux piézoélectriques offrent une sensibilité qui permet d’exploiter des sollicitations mécaniques très faibles. Ils sont également intégrables, éventuellement sur substrat souple.Dans cette thèse nous nous intéressons au potentiel des nanofils de matériaux semi-conducteurs piézoélectriques, tels que ZnO ou les composés III-V, pour la conversion d’énergie mécanique en énergie électrique. Depuis peu, ceux-ci ont fait l’objet d’études relativement nombreuses, avec la réalisation de nanogénérateurs (NG) prometteurs. De nombreuses questions subsistent toutefois avec, par exemple, des contradictions notables entre prédictions théoriques et observations expérimentales.Notre objectif est d’approfondir la compréhension des mécanismes physiques qui définissent la réponse piézoélectrique des NF semi-conducteurs et des NG associés. Le travail expérimental s’appuie sur la fabrication de générateurs de type VING (Vertical Integrated Nano Generators) et sur leur caractérisation. Pour cela, un système de caractérisation électromécanique a été construit pour évaluer les performances des NG réalisés et les effets thermiques sous une force compressive contrôlée. Le module d’Young et les coefficients piézoélectriques effectifs de NF de GaN; GaAs et ZnO et de NF à structure cœur/coquille à base de ZnO ont été évalués également dans un microscope à force atomique (AFM). Les nanofils de ZnO sont obtenus par croissance chimique en milieu liquide sur des substrats rigides (Si) ou flexibles (inox) puis sont intégrés pour former un générateur. La conception du dispositif VING s’est appuyée sur des simulations négligeant l’influence des porteurs libres, comme dans la plupart des études publiées. Nous avons ensuite approfondi le travail théorique en simulant le couplage complet entre les effets mécaniques, piézoélectriques et semi-conducteurs, et en tenant compte cette fois des porteurs libres. La prise en compte du piégeage du niveau de Fermi en surface nous permet de réconcilier observations théoriques et expérimentales. Nous proposons notamment une explication au fait que des effets de taille apparaissent expérimentalement pour des diamètres au moins 10 fois plus grands que les valeurs prévues par simulation ab-initio ou au fait que la réponse du VING est dissymétrique selon que le substrat sur lequel il est intégré est en flexion convexe ou concave<br>Energy autonomy in small sensors networks is one of the key quality parameter for end-users. It’s even critical when addressing applications in structures health monitoring (avionics, machines, building…), or in medical or environmental monitoring applications. Piezoelectric materials make it possible to exploit the otherwise wasted mechanical energy which is abundant in our environment (e. g. from vibrations, deformations related to movements or air fluxes). Thus, they can contribute to the energy autonomy of those small sensors. In the form of nanowires (NWs), piezoelectric materials offer a high sensibility allowing very small mechanical deformations to be exploited. They are also easy to integrate, even on flexible substrates.In this PhD thesis, we studied the potential of semiconducting piezoelectric NWs, of ZnO or III-V compounds, for the conversion from mechanical to electrical energy. An increasing number of publications have recently bloomed about these nanostructures and promising nanogenerators (NGs) have been reported. However, many questions are still open with, for instance, contradictions that remain between theoretical predictions and experimental observations.Our objective is to better understand the physical mechanisms which rule the piezoelectric response of semiconducting NWs and of the associated NGs. The experimental work was based on the fabrication of VING (Vertical Integrated Nano Generators) devices and their characterization. An electromechanical characterization set-up was built to evaluate the performance and thermal effects of the fabricated NGs under controlled compressive forces. Atomic Force Microscopy (AFM) was also used to evaluate the Young modulus and the effective piezoelectric coefficients of GaN, GaAs and ZnO NWs, as well as of ZnO-based core/shell NWs. Among them, ZnO NWs were grown using chemical bath deposition over rigid (Si) or flexible (stainless steel) substrates and further integrated to build VING piezoelectric generators. The VING design was based on simulations which neglected the effect of free carriers, as done in most publications to date. This theoretical work was further improved by considering the complete coupling between mechanical, piezoelectric and semiconducting effects, including free carriers. By taking into account the surface Fermi level pinning, we were able to reconcile theoretical and experimental observations. In particular, we propose an explanation to the fact that size effects are experimentally observed for NWs with diameters 10 times higher than expected from ab-initio simulations, or the fact that VING response is non-symmetrical according to whether the substrate on which it is integrated is actuated with a convex or concave bending
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Webber, Kyle Grant. "Effect of Domain Wall Motion and Phase Transformations on Nonlinear Hysteretic Constitutive Behavior in Ferroelectric Materials." Diss., Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22695.
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The primary focus of this research is to investigate the non-linear behavior of
single crystal and polycrystalline relaxor ferroelectric PMN-xPT and PZN-xPT through
experimentation and modeling.
Characterization of single crystal and polycrystalline specimens with similar
compositions was performed. These data give experimental insight into the differences
that may arise in a polycrystal due to local interaction with inhomogeneities. Single
crystal specimens were characterized with a novel experimental technique that reduced
clamping effects at the boundary and gave repeatable results. The measured
experimental data was used in conjunction with electromechanical characterizations of
other compositions of single crystal specimens with the same crystallographic orientation
to study the compositional effects on material properties and phase transition behavior.
Experimental characterization provided the basis for the development of a model
of the continuous phase transformation behavior seen in PMN-xPT single crystals. In the
modeling it is assumed that a spatial chemical and structural heterogeneity is primarily
responsible for the gradual phase transformation behavior observed in relaxor
ferroelectric materials. The results are used to simulate the effects of combined electrical
and mechanical loading.
An improved rate-independent micromechanical constitutive model based on the
experimental observations of single crystal and polycrystalline specimens under large
field loading is also presented. This model accounts for the non-linear evolution of
variant volume fractions. The micromechanical model was calibrated using single crystal data. Simulations of the electromechanical behavior of polycrystalline ferroelectric materials are presented. These results illustrate the effects of non-linear single crystal behavior on the macroscopic constitutive behavior of polycrystals.
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Woodburn, David. "Modeling and Simulation of All-electric Aircraft Power Generation and Actuation." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6037.
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Modern aircraft, military and commercial, rely extensively on hydraulic systems. However, there is great interest in the avionics community to replace hydraulic systems with electric systems. There are physical challenges to replacing hydraulic actuators with electromechanical actuators (EMAs), especially for flight control surface actuation. These include dynamic heat generation and power management.
Simulation is seen as a powerful tool in making the transition to all-electric aircraft by predicting the dynamic heat generated and the power flow in the EMA. Chapter 2 of this dissertation describes the nonlinear, lumped-element, integrated modeling of a permanent magnet (PM) motor used in an EMA. This model is capable of representing transient dynamics of an EMA, mechanically, electrically, and thermally.
Inductance is a primary parameter that links the electrical and mechanical domains and, therefore, is of critical importance to the modeling of the whole EMA. In the dynamic mode of operation of an EMA, the inductances are quite nonlinear. Chapter 3 details the careful analysis of the inductances from finite element software and the mathematical modeling of these inductances for use in the overall EMA model.
Chapter 4 covers the design and verification of a nonlinear, transient simulation model of a two-step synchronous generator with three-phase rectifiers. Simulation results are shown.<br>Ph.D.<br>Doctorate<br>Electrical Engineering and Computer Science<br>Engineering and Computer Science<br>Electrical Engineering
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Fan, Yu. "Multi-scale approaches for the vibration and energy flow through piezoelectric waveguides : simulation strategies, control mechanisms and circuits optimization." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC019/document.
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Cette thèse s’interesse au contrôle des flux d’énergie mécanique dans les structures périodiques. Les problèmes de dynamiques des structures considérés dans cette thèse sont abordés sous l'angle d'une description ondulatoire : la réponse forcée d’un système est calculée comme une superposition d’ondes dans la structure, tandis que les modes propres sont interprétés comme des ondes stationnaires.Un des avantages de l’approche ondulatoire est qu’elle permet de réduire de manière importante la taille des problèmes de dynamique. Ceci se révèle particulièrement utile dans le domaine des hautes et moyennes fréquences, où les calculs par éléments finis deviennent très coûteux en temps à cause du grand nombre de degrés de liberté nécessaire à la convergence du modèle. Afin de contourner ce problème, cette thèse s'appuie sur la méthode des éléments finis ondulatoires (Wave Finite Element Method (WFEM)). Une des principales améliorations proposées est l’utilisation de plusieurs méthodes de synthèses modales (Component Mode Synthesis (CMS)) pour accélérer l’analyse des guides d’ondes généraux en présence d’amortissement ou de matériaux piézo-électriques. Les erreurs numériques restent faibles du fait de l’utilisation d'une base de projection réduite constituée d'ondes propagatives. Une autre contribution est le procédé de modélisation multi-échelle pour les assemblages de structures périodiques et non-périodiques. L’idée principale est de modéliser les parties non-périodiques par la méthode des éléments finis, et les parties périodiques par WFEM. Les interactions entre les différentes sous-structures sont modélisées par des coefficients de réflexion ou des impédances mécaniques. Ces travaux réalisent une extension de la WFEM à des structures plus complexes et plus proches des applications industrielles. Un autre intérêt de la vision ondulatoire est qu’elle mène à de nouvelles idées pour le contrôle des vibrations. Dans cette thèse, des matériaux piézo-électriques et des circuits de shunt, distribués de façon périodique sont utilisés afin de modifier artificiellement la propagation des ondes grâce au couplage électromécanique. Un nouveau critère, nommé « Wave Electromechanical Coupling Factor (WEMCF) », est proposé pour évaluer, en termes énergétiques, l’intensité du couplage entre le champ électrique et le champ mécanique lors du passage d'une onde. Ce facteur peut être obtenu à partir des caractéristiques ondulatoires obtenues par la WFEM. On montre que le WEMCF est fortement lié à l'atténuation dans le guide d’ondes piézo-électrique. La conception des paramètres géométriques et électriques peut être ainsi être effectuée séparément. Ce principe est appliqué à la réduction des vibrations d’une poutre encastrée. Le WEMCF est utilisé comme fonction objectif pour l'optimisation durant la conception géométrique, la masse totale de matériau piézo-électriques étant contrainte. Un circuit à capacité négative est utilisé pour élargir le band-gap de Bragg. La stabilité du système est prise en compte comme une contrainte sur la valeur de cette capacité. Les vibrations sont localisées et facilement dissipées par l’introduction d’absorbeurs sur la frontière. Ce procédé de conception basée sur une approche ondulatoire aboutit à des solutions stables, légères, et insensibles aux conditions aux limites dans une large gamme de fréquence. Par conséquent, il est prometteur pour analyser les structures en moyenne et haute fréquence où il est difficile d’accéder aux informations modales exactes<br>This thesis describes analysis and control approaches for the vibration and energy flow through periodic structures. The wave description is mainly used to address the structural dynamic problems considered in the thesis: forced response is calculated as the superposition of the wave motions; natural modes are understood as standing waves induced by the propagating waves that recover to the same phase after traveling a whole circle of the finite structure. One advantage of the wave description is that they can remarkably reduce the dimensions of structural dynamic problems. This feature is especially useful in mid- and high frequencies where directly computing the full Finite Element Method (FEM) model is rather time-consuming because of the enormous number of degree-of-freedoms. This thesis extends one widely used wave-based numerical tool termed Wave Finite Element Method (WFEM). The major improvements are the use of several Component Mode Synthesis (CMS) methods to accelerate the analysis for general waveguides with proportional damping or piezoelectric waveguides. The numerical error is reduced by using the proposed eigenvalue schemes, the left eigenvectors and the reduced wave basis. Another contribution is the multi-scale modeling approach for the built-up structures with both periodic and non-periodic parts. The main idea is to model the non-periodic parts by FEM, and model the periodic parts by WFEM. By interfacing different substructures as reflection coefficients or mechanical impedance, the response of the waveguide is calculated in terms of different scales. These two contributions extend WFEM to more complex structures and to more realistic models of the engineering applications.Another benefit of the wave perception is that it leads to new ideas for vibration control. In this thesis periodically distributed piezoelectric materials and shunt circuit are used to artificially modify the wave properties by electric impedance. A novel metrics termed the Wave Electromechanical Coupling Factor (WEMCF) is proposed, to quantitatively evaluate the coupling strength between the electric and mechanical fields during the passage of a wave. This factor can be post-processed from the wave characteristics obtained from WFEM through an energy formula. We show that WEMCF is strongly correlated to the best performance of the piezoelectric waveguide. Hence the design for the geometric and electric parameters can be done separately. An application is given, concerning the vibration reduction of a cantilever beam. WEMCF is used as an optimization objective during the geometric design, when the overall mass of the piezoelectric materials is constrained. Then the negative capacitance is used with a stability consideration to enlarge the Bragg band gap. The vibration is localized and efficiently dissipated by few boundary dampers. The wave-based design process yields several broadband, stable, lightweight and boundary condition insensitive solutions. Therefore, it is promising at mid- and high frequencies where exact modal information is difficult to access
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Fu, Jian. "Prototypage virtuel incrémental des actionneurs électromécanique pour la synchronisation en position." Thesis, Toulouse, INSA, 2016. http://www.theses.fr/2016ISAT0008/document.
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Dans le domaine de l'aéronautique, les concepts basés sur l’usage étendu de l'électricité dans les aéronefs plus électriques (MEA) et même tout électriques (AEA) font appel à des actionneurs électromécaniques (EMA) en replacement des actionneurs servo-hydrauliques conventionnels (HSA). Lorsque les EMA sont utilisés pour des applications d'actionnement critique comme les commandes de vol, certains problèmes spécifiques liés à l’équilibre thermique, l'inertie réfléchie, le mouvement parasite dû aux élasticités structurelles, la réponse aux fautes (grippage et rupture) et la synchronisation d’EMA actifs sur charges indépendantes ne peuvent être ignorés. La simulation apporte un support indéniable à la conception pour l’évaluation et la validation des concepts. A cet effet, il est nécessaire de développer des prototypes virtuels des EMA avec une vision système et de façon structurée pour répondre aux besoins des ingénieurs. Malheureusement, les phénomènes physiques qui apparaissent dans les EMA sont multidisciplinaires, couplés et fortement non linéaires. De nombreux logiciels commerciaux de simulation système multi-domaines sont désormais disponibles. Cependant, le processus de modélisation et les besoins des ingénieurs sont rarement pris en compte selon une vision globale, en raison du manque d'approches scientifiques pour la définition d’architectures, la modélisation incrémentale et l’amélioration de l’implémentation numérique des modèles. Dans cette thèse, le prototypage virtuel de l'EMA est adressé en utilisant le formalisme Bond-Graph. De nouvelles approches sont proposées pour permettre la modélisation incrémentale de l'EMA en vue de fournir des modèles pour la synthèse de la commande, l’évaluation de la consommation d'énergie, l'analyse thermique, le calcul des forces de réaction, la simulation de la pollution du réseau d'alimentation électrique, la réponse aux fautes et l'influence de la température. L’intérêt des modèles proposés est illustré sur l’exemple de la synchronisation de position de deux EMA actionnant des charges indépendantes<br>In the aerospace field, the concepts based on extended use of electricity in “More Electric Aircraft” (MEA) and even “All Electric Aircraft” (AEA), involve electromechanical actuators (EMAs) to replace conventional hydraulic servo actuators (HSAs). When EMAs are used for safety-critical actuation applications like flight controls, some specific issues related to thermal balance, reflected inertia, parasitic motion due to compliance, response to failure (jamming and free-run) and synchronization of EMAs driving independent loads cannot be ignored. The simulation-aided design process can efficiently support the assessment and validation of the concepts fixing these issues. For that, virtual prototypes of EMAs at system-level have to be developed in a structured way that meets the engineers’ needs. Unfortunately, the physical effects governing the EMAs behavior are multidisciplinary, coupled and highly nonlinear. Although numerous multi-domain and system-level simulation packages are now available in the market of simulation software, the modelling process and the engineers’ needs are rarely addressed as a whole because of lack of scientific approaches for model-based architecting, multi-purpose incremental modelling and model implementation for efficient numerical simulation. In this thesis, the virtual prototyping of EMAs is addressed using the Bond-Graph formalism. New approaches are proposed to enable incremental modelling of EMAs that provides models supporting control design, energy consumption and thermal analysis, calculation of reaction forces, power network pollution simulation, prediction of response to faults and influence of temperature. The case of preliminary design of EMAs position synchronization is used to highlight the interests and advantages of the proposed process and models of EMAs
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Sun, Ho I. "Experimental investigations and simulations of indoor air quality for wet market." Thesis, University of Macau, 2006. http://umaclib3.umac.mo/record=b1636571.
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Otten, James S. (James Stewart). "Design of a gas force simulator for the MIT Electromechanical Valve Drive project." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36718.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.<br>Includes bibliographical references (leaf 29).<br>The MIT electromechanical Valve Drive (EMVD) is a continuously variable valve actuation device for an automotive internal combustion engine. Current experimentation of the EMVD has been limited to intake valve events. When the exhaust valve opens into the cylinder it must do so against gas forces arising from high pressure in the engine cylinder. This gas force causes power losses in the EMVD. A gas force simulator has been designed to simulate the pressure acting against the exhaust valve in the engine cylinder. This allows the power loss as a result of the gas force to be measured for the EMVD.<br>by James S. Otten.<br>S.B.
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Zeroukhi, Youcef. "Analyse de la résistance d'un conducteur électrique en fonction des paramètres du procédé d'écrouissage et de sa géométrie." Thesis, Artois, 2014. http://www.theses.fr/2014ARTO0202/document.
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Le mémoire de thèse propose une méthode de modélisation multi physique capable de quantifier l’influence des paramètres des processus d’écrouissage, le câblage et le compactage, sur le comportement mécanique et électrique des câbles électriques. Les propriétés électriques d’un câble dépendent de la nature du matériau utilisé, de son état métallurgique, des contraintes mécaniques exercées et de la conductance électrique des aires de contact inter-fils. De nombreuses mesures ont permis de définir les caractéristiques des câbles mais aussi des matériaux utilisés, comme par exemple la variation de la conductivité électrique d’un fil de cuivre en fonction de l’écrouissage. La modélisation mécanicoélectrique, réalisée avec le logiciel Abaqus®, est utilisée pour étudier les différents paramètres impliqués dans les processus de câblage et de compactage. Cela a permis de déterminer les déformations géométriques des fils ainsi que les contraintes mécaniques dans le câble. Les résultats de simulation sont comparés aux mesures afin de valider la précision des modèles numériques développés.Un couplage faible entre les modèles mécanique et électrique permet de mettre en évidence la distribution non-homogène de la conductivité électrique à l’intérieur d’un conducteur après qu’il ait subi des contraintes mécaniques dues au processus de déformation à froid, le câblage et le compactage. Ensuite, en appliquant une procédure d’optimisation, nous avons identifié les paramètres capables de réduire de 2 % la masse du matériau conducteur utilisés dans les processus de fabrication, tout en conservant des propriétés mécaniques et électrique répondant aux exigences normatives des constructeurs de câbles<br>The presented PhD thesis propose multi-physics modeling method able to predict the impact of stranding and compacting processes parameters on the mechanical and electrical behavior of stranded conductors. The electrical properties of stranded conductors depend on the nature of the material, on its metallurgical state, on the mechanical pressure within the conductor and on the electrical conductance of contact areas between wires. A wide range of measurements has allowed us to define the characteristics of structures and materials, such as for example the resistivity as a function of the stresses due to material hardening. The electromechanical modeling with Abaqus and Vector Fields software are used to study different parameters involved in the stranding and compacting processes to determine actual wires shapes, induced deformations and actual stresses between wires within the conductor. The results obtained by simulation were compared with experimental measurements to analyze the accuracy of the model. By coupling mechanical and electrical simulations, we pointed out the non-homogeneous distribution of the electrical conductivity along conductor cross sections resulting from the hardness of each single wire. Applying the optimization procedure, we have identified the parameters able to reduce the mass of conducting material by 2 % while maintaining mechanical and electrical properties that meet the prescriptive requirements of cables manufacturers and standards
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Berhane, Rufael. "An electromechanical synchronization of driving simulator and adaptive driving aide for training persons with disabilities." [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002350.
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Tsai, Shu-Jen Steven. "Study of Global Power System Frequency Behavior Based on Simulations and FNET Measurements." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/28303.
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A global view of power system's frequency opens up a new window to the "world" of large system's dynamics. With the aid of global positioning system (GPS), measurements from different locations can be time-synchronized; therefore, a system-wide observation and analysis would be possible. As part of the U.S. nation-wide power frequency monitoring network project (FNET), the first part of the study focuses on utilizing system simulation as a tool to assess the frequency measurement accuracy needed to observe frequency oscillations from events such as remote generation drops in three U.S. power systems. Electromechanical wave propagation phenomena during system disturbances, such as generation trip, load rejection and line opening, have been observed and discussed. Further uniform system models are developed to investigate the detailed behaviors of wave propagation. Visualization tool is developed to help to view frequency behavior simulations. Frequency replay from simulation data provides some insights of how these frequency electromechanical waves propagate when major events occur. The speeds of electromechanical wave propagation in different areas of the U.S. systems, as well as the uniform models were estimated and their characteristics were discussed. Theoretical derivation between the generator's mechanical powers and bus frequencies is provided and the delayed frequency response is illustrated.
Field-measured frequency data from FNET are also examined. Outlier removal and wavelet-based denoising signal processing techniques are applied to filter out spikes and noises from measured frequency data. System's frequency statistics of three major U.S. power grids are investigated. Comparison between the data from phasor measurement unit (PMU) at a high voltage substation and from FNET taken from 110 V outlets at distribution level illustrates the close tracking between the two. Several generator trip events in the Eastern Interconnection System and the Western Electricity Coordinating Council system are recorded and the frequency patterns are analyzed. Our trigger program can detect noticeable frequency drop or rise and sample results are shown in a 13 month period. In addition to transient states' observation, the quasi-steady-state, such as oscillations, can also be observed by FNET. Several potential applications of FNET in the areas of monitoring & analysis, system control, model validation, and others are discussed. Some applications of FNET are still beyond our imagination.<br>Ph. D.
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Reysset, Aurelien. "Conception préliminaire d'actionneurs électromécaniques - outils d'aide à la spécification et à la génération de procédures de dimensionnement pour l'optimisation." Thesis, Toulouse, INSA, 2015. http://www.theses.fr/2015ISAT0003/document.
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Cette thèse a pour objectif d’apporter un ensemble d’outils logiciels s’inscrivant dans une méthodologie globale de conception de systèmes mécatroniques. Elle arrive en complément de travaux déjà menés au sein du laboratoire sur le pré-dimensionnement d’actionneurs aéronautiques de nouvelle génération : les actionneurs électromécaniques (EMA). Cette technologie apporte de nouvelles problématiques qui forcent les ingénieurs à modifier leur processus de développement et ce dès la phase de spécification où des profils de mission devront être générés/transformés/analysés de manière à simplifier la conception et assurer leur validation. Une toolbox Simulink a donc été créée dans cette thèse pour répondre à ce besoin de transformation de l’information entre avionneur et systémier. Comme tout système embarqué, le concepteur fait face à des compromis entre performances, durée de vie et intégration, qui peuvent se résumer à un problème d’optimisation décrit par un ensemble d’équations et de contraintes. Un effort particulier de description a été mené sur le conditionnement de ces équations sous la forme d’un séquencement de calculs explicites adaptés aux algorithmes d’optimisation. La méthode et son implémentation logicielle, toutes deux basées sur la théorie des graphes, interagissent avec le concepteur de manière à l’informer des erreurs de singularité ou de bouclages algébriques apparaissant dans son problème et à lui fournir des pistes de résolution. Pour finir, des études de pré-dimensionnement d’actionneurs de train d’atterrissage et de surfaces de vol primaires (aileron et spoiler), réalisées dans le cadre de cette thèse, dresseront les possibilités offertes par cette approche innovante : conception intégrée avec une cinématique complexe, conception collaborative pluri-partenaires découplée, utilisation de surfaces de réponse pour accélérer l’optimisation<br>The aim of this thesis is to bring a package of software tools included in a whole methodology dealing with mechatronic systems design. It comes as an add-on to the work already carried out at the laboratory in the field of the new generation of aircraft actuation systems: electromechanical actuators (EMA). This technology triggers new problematics leading the engineers to modify their development process as early as the specification phase, when mission profiles have to be generated/transformed/analyzed in order to simplify the design and ensure the validation step. Thus a Simulink toolbox has been created to meet the need for an information translator working as an intermediate between airframer and system-supplier. As for all the embedded systems, the designer has to face some performance-lifetime-integration trade-off, which can be considered as an optimization problem described by a set of equations and constraints. Particular attention is paid here to the conditioning of those explicit equations in order to obtain a standardized calculation sequence adapted to many optimization algorithms. The method and implemented software, both based on the graph theory, interact with the designer to inform him on the possible singularity and algebraic loop issues, providing some leads for their resolution. Finally, some preliminary sizing studies of landing gear and primary flight control surfaces (aileron and spoiler) actuation systems are presented to highlight the possibilities brought out by this innovative approach: integrated design with complex kinematics, collaborative multi-partners design, use of response surfaces to speed up the optimization
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Peng, Shuiran. "Analyse mathématique et numérique de plusieurs problèmes non linéaires." Thesis, Poitiers, 2018. http://www.theses.fr/2018POIT2306/document.
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Cette thèse est consacrée à l’étude théorique et numérique de plusieurs équations aux dérivées partielles non linéaires qui apparaissent dans la modélisation de la séparation de phase et des micro-systèmes électro-mécaniques (MSEM). Dans la première partie, nous étudions des modèles d’ordre élevé en séparation de phase pour lesquels nous obtenons le caractère bien posé et la dissipativité, ainsi que l’existence de l’attracteur global et, dans certains cas, des simulations numériques. De manière plus précise, nous considérons dans cette première partie des modèles de type Allen-Cahn et Cahn-Hilliard d’ordre élevé avec un potentiel régulier et des modèles de type Allen-Cahn d’ordre élevé avec un potentiel logarithmique. En outre, nous étudions des modèles anisotropes d’ordre élevé et des généralisations d’ordre élevé de l’équation de Cahn-Hilliard avec des applications en biologie, traitement d’images, etc. Nous étudions également la relaxation hyperbolique d’équations de Cahn-Hilliard anisotropes d’ordre élevé. Dans la seconde partie, nous proposons des schémas semi-discrets semi-implicites et implicites et totalement discrétisés afin de résoudre l’équation aux dérivées partielles non linéaire décrivant à la fois les effets élastiques et électrostatiques de condensateurs MSEM. Nous faisons une analyse théorique de ces schémas et de la convergence sous certaines conditions. De plus, plusieurs simulations numériques illustrent et appuient les résultats théoriques<br>This thesis is devoted to the theoretical and numerical study of several nonlinear partial differential equations, which occur in the mathematical modeling of phase separation and micro-electromechanical system (MEMS). In the first part, we study higher-order phase separation models for which we obtain well-posedness and dissipativity results, together with the existence of global attractors and, in certain cases, numerical simulations. More precisely, we consider in this first part higher-order Allen-Cahn and Cahn-Hilliard equations with a regular potential and higher-order Allen-Cahn equation with a logarithmic potential. Moreover, we study higher-order anisotropic models and higher-order generalized Cahn-Hilliard equations, which have applications in biology, image processing, etc. We also consider the hyperbolic relaxation of higher-order anisotropic Cahn-Hilliard equations. In the second part, we develop semi-implicit and implicit semi-discrete, as well as fully discrete, schemes for solving the nonlinear partial differential equation, which describes both the elastic and electrostatic effects in an idealized MEMS capacitor. We analyze theoretically the stability of these schemes and the convergence under certain assumptions. Furthermore, several numerical simulations illustrate and support the theoretical results
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Zemzemi, Nejib. "Étude théorique et numérique de l'activité électrique du cœur: Applications aux électrocardiogrammes." Phd thesis, Université Paris Sud - Paris XI, 2009. http://tel.archives-ouvertes.fr/tel-00470375.
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La modélisation du vivant, en particulier la modélisation de l'activité cardiaque, est devenue un défi scientifique majeur. Le but de cette thématique est de mieux comprendre les phénomènes physiologiques et donc d'apporter des solutions à des problèmes cliniques. Nous nous intéressons dans cette thèse à la modélisation et à l'étude numérique de l'activité électrique du cœur, en particulier l'étude des électrocardiogrammes (ECGs). L'onde électrique dans le cœur est gouvernée par un système d'équations de réaction-diffusion appelé modèle bidomaine ce système est couplé à une EDO représentant l'activité cellulaire. Afin simuler des ECGs, nous tenons en compte la propagation de l'onde électrique dans le thorax qui est décrite par une équation de diffusion. Nous commençons par une démonstrer l'existence d'une solution faible du système couplé cœur-thorax pour une classe de modèles ioniques phénoménologiques. Nous prouvons ensuite l'unicité de cette solution sous certaines conditions. Le plus grand apport de cette thèse est l'étude et la simulation numérique du couplage électrique cœur-thorax. Les résultats de simulations sont représentés à l'aide des ECGs. Dans une première partie, nous produisons des simulations pour un cas normal et pour des cas pathologiques (blocs de branche gauche et droit et des arhythmies). Nous étudions également l'impact de certaines hypothèses de modélisation sur les ECGs (couplage faible, utilisation du modèle monodomaine, isotropie, homogénéité cellulaire, comportement résistance-condensateur du péricarde,. . . ). Nous étudions à la fin de cette partie la sensibilité des ECGs par apport aux paramètres du modèle. En deuxième partie, nous effectuons l'analyse numérique de schémas du premier ordre en temps découplant les calculs du potentiel d'action et du potentiel extérieur. Puis, nous combinons ces schémas en temps avec un traîtement explicite du type Robin-Robin des conditions de couplage entre le cœur et le thorax. Nous proposons une analyse de stabilité de ces schémas et nous illustrons les résultats avec des simulations numériques d'ECGs. La dernière partie est consacrée à trois applications. Nous commençons par l'estimation de certains paramètres du modèle (conductivité du thorax et paramètres ioniques). Dans la deuxième application, qui est d'originie industrielle, nous utilisons des méthodes d'apprentissage statistique pour reconstruire des ECGs à partir de mesures ('électrogrammes). Enfin, nous présentons des simulations électro-mécaniques du coeur sur une géométrie réelle dans diverses situations physiologiques et pathologiques. Les indicateurs cliniques, électriques et mécaniques, calculés à partir de ces simulations sont très similaires à ceux observés en réalité.
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CALHEIROS, JUNIOR Eduardo Jorge. "Estimação computacional dos esforços eletromecânicos em transformadores de potência no sistema CHESF." Universidade Federal de Campina Grande, 2014. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/257.
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Previous issue date: 2014-06<br>As análises de adequabilidade de equipamentos são indispensáveis para permitir que as
empresas do setor elétrico conheçam as condições em que os mesmos operam,
garantindo assim o desempenho dos ativos da empresa e sua disponibilidade no Sistema
Interligado Nacional. Dentre os equipamentos analisados, destacam-se os
transformadores de potência pelo seu alto custo e a sua importância para o sistema
elétrico. Grande parte das falhas em transformadores de potência é de origem dielétrica,
relacionadas com a danificação da isolação dos condutores devido às deformações
mecânicas ocasionadas pelas altas correntes de curto-circuito passantes nos
enrolamentos, reduzindo a vida útil do equipamento. A partir destas considerações,
propôs-se avaliar os esforços eletromecânicos internos a alguns transformadores de
potência presentes no sistema CHESF, por intermédio de simulações computacionais,
quando da ocorrência de curto-circuito trifásico. A metodologia para as simulações
consistiu em selecionar os transformadores a serem analisados e coletar as informações
técnicas necessárias fornecidas pelos fabricantes. Posteriormente foram determinadas as
condições sistêmicas às quais os transformadores estariam submetidos e obtidos os
níveis de curto-circuito resultantes, para então efetuar as simulações propriamente ditas.
Os resultados das simulações computacionais mostraram os esforços eletromecânicos
estimados em quatro transformadores de potência em operação no sistema elétrico da
CHESF, resultantes do efeito dinâmico da corrente de curto-circuito trifásico que
percorrem os enrolamentos do transformador, considerando diferentes configurações
sistêmicas. As conclusões das análises dos resultados indicaram possíveis casos de
superações de limites admissíveis e revelou a importância dos aspectos construtivos dos
transformadores na sua capacidade de suportar os esforços mecânicos causados por
curtos-circuitos.<br>Analysis of suitability of equipment are indispensable for the electric sector companies
meet the conditions in which they operate, thus ensuring the performance of the
company's assets and its availability in the National Interconnected System (Sistema
Interligado Nacional). The power transformers are included among the analyzed
equipment due to its high cost and importance for the electrical system. Most faults in
power transformers is of dielectric origin, related to insulation damage due to
mechanical deformations, caused by the high short-circuit currents in the windings,
reducing the life of the equipment. Then, it was proposed to evaluate the internal
electromechanical efforts to some power transformers present in the CHESF system,
through computer simulations, in the event of a three-phase short circuit. The
methodology for the simulations consisted to select the transformers to parse and collect
the necessary technical information provided by the manufacturers. Later, certain
systemic conditions in which the transformers would be subjected were defined, it was
obtained the resulting short circuit levels and then was performed the simulations
themselves. The results of the computer simulations showed the electromechanical
efforts estimated at four power transformers in operation in the CHESF electrical
system, resulting from the dynamic effect of three-phase short-circuit current that run
through the windings of the transformer, considering different systemic configurations.
The conclusions of the analysis results indicated possible cases of overruns of
permissible limits and reveal the importance of the transformers constructive aspects in
their ability to withstand the mechanical stress caused by short circuits.
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Kerbouai, Hamza. "Modélisation, dimensionnement et optimisation d'un capteur hybride pour la détection des deux roues motorisées dans le trafic routier." Thesis, Belfort-Montbéliard, 2015. http://www.theses.fr/2015BELF0260/document.
Full textAbstract:
Depuis plusieurs années les chiffres de l'insécurité routière montrent la nécessité de développer un outil technologique qui vise à connaitre le comportement de véhicules deux roues motorisés (2RM) afin d'améliorer leursécurité. De cette problématique découle nos travaux de recherche qui s'inscrivent dans le cadre de projet METRAMOTO (MEsure du TRAfic des deux-roues MOTOrisés pour la sécurité routière et l'évaluation des risques)L’objectif principal visé concerne la modélisation, le dimensionnement et l'optimisation d'un capteur hybride constitué d'une part de boucles électromagnétiques et d'autre part de capteurs de chocs piézo-électriques. L’idée consiste à utiliser les boucles électromagnétiques pour discriminer la présence des 2RM de celle des autresvéhicules, associées à des segments piézo-électriques pour détecter le choc produit par le passage des roues desdifférents véhicules, le tout associé à un algorithme de gestion et de traitement de données. Aujourd'hui redimensionnement des systèmes de détection à base de boucles électromagnétiques ou de câble piézo-électriquese fait de manière expérimentale sur des sites contrôlés en utilisant plusieurs types de véhicules. Cette technique gourmande en temps nécessite une série importante d'essais couteux et dangereux. La présente étude a pour butde modéliser les différentes interactions entre le capteur hybride étudié et les véhicules en vue de son dimensionnement. Des modèles électromagnétiques et électromécaniques sont développés pour décrire les différentes interactions se produisant entre les boucles électromagnétiques d'une part, les boucles électromagnétiques et les véhicules d'autre part ainsi que celles des roues de véhicules et le câble piézoélectrique.Sur la base de ces modèles établis, une démarche générale est élaborée conduisant au dimensionnement du capteur hybride pour une route donnée. Nous nous sommes également intéressés au traitement des données issues du capteur hybride pour lesquelles nous proposons une approche d'identification des différentes catégories de véhicules dont les 2RM. Deux configurations de capteurs pour deux routes différentes sont alors proposées.Elles sont associées à des algorithmes de traitement de données permettant l'acquisition des signaux de boucles et de câbles, la distinction des différents types de véhicules, l'estimation de la position des véhicules sur la chaussée ainsi que la mesure de la vitesse de véhicules<br>For several years the road safety numbers show the need to develop a technological tool that aims to know thepowered two wheelers vehicles behavior (2PW) to improve their security. From this problematic arise our researchworks that come under the project METRAMOTO (Powered two wheelers traffic measurement for road safety andrisks assessment). The main objective is modeling, sizing and optimization of an hybrid sensor consisted ofelectromagnetic loops and piezoelectric shock sensors. The idea is to use electromagnetic loops to discriminate the2PW presence from the other vehicles, combined with piezoelectric segments to detect the shocks produced by thevehicles wheels passage, all associated with a management algorithm and data processing. Today the sizing of thedetection systems based on electromagnetic loops or piezoelectric cables is done experimentally on controlled sitesusing several vehicles types. This technique requires significant test series which are costly and dangerous. Thisstudy aims to modeling the different interactions between the studied sensor and vehicles in order to its sizing.Electromagnetic and electromechanical models are developed to describe the different interactions that take placebetween electromagnetic loops on the one hand, between electromagnetic loops and vehicles on the other handand those between vehicle wheels and piezoelectric cable. On the basis of established models, a general approachis elaborated driving to sizing the hybrid sensor for any given road. We are also interested to the data processingcoming from the hybrid sensor for which we propose an approach to identifying the different vehicle categoriesincluding the 2PW. Two sensor configurations for two different roads are then proposed. They are associated atdata processing algorithms allowing the acquisition of loops and cables signals, the distinction between the differentvehicles classes, the estimation of the vehicles positions on the road and the measuring of their speed
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García, Cañadilla Patricia. "Multiscale cardiovascular analysis and simulations for the understanding of intra-uterine cardiovascular remodelling." Doctoral thesis, Universitat Pompeu Fabra, 2015. http://hdl.handle.net/10803/310949.
Full textAbstract:
Cardiovascular diseases are nowadays one of the major causes of death in developed countries. Besides the already known risk factors such as lifestyle and genetics, there is a growing evidence that adverse remodelling during prenatal life presents a risk factor for some cardiovascular diseases at later life. Recent studies have demonstrated that fetuses with intra-uterine growth restriction show cardiovascular remodelling at organ, vascular and also cellular and subcellular level, and moreover these changes persist postnatally. However this is a complex mechanism that needs to be further investigated. Currently, Doppler ultrasonography is one of the techniques most used to assess the fetal cardiovascular status and to study the heart and vascular remodelling in clinical practice. However, some of underlying hemodynamic and vascular changes cannot be assessed clinically and more sophisticated techniques are needed. Computational modelling of biological systems arises as a powerful tool to overcome this challenge, to support clinicians and to improve the understanding of different pathologies. In this thesis we proposed the use of computational models of fetal circulation, of cardiac cells and also image-processing tools, to improve the understanding of intra-uterine cardiac remodelling that takes place at different scales of the fetal cardiovascular system, and also to estimate the patient-specific hemodynamic properties that cannot be directly assessed from clinical measurements. The results arising from this thesis demonstrate that computational models are able to improve the understanding and detection of the intra-uterine cardiovascular remodelling by means of patient-specific simulations.<br>Les malalties cardiovasculars són avui en dia una de les principals causes de mortalitat en països desenvolupats. Deixant de banda els factors de risc relacionats amb l'estil de vida i la genètica, existeix una creixent evidència de què la remodelació adversa durant la vida prenatal esdevé un factor de risc per a algunes malalties cardiovasculars en l'edat adulta. S'ha demostrat que els fetus amb restricció de creixement intrauterina mostren signes de remodelació cardiovascular tant a nivell d'òrgan, vascular com a nivell cel•lular i subcel•lular, i molts cops aquests canvis persisteixen postnatalment. No obstant, és tracta d'un mecanisme complex que necessita ser investigat en profunditat. Actualment, l'ecografia Doppler és una de les tècniques més empradres per avaluar l'estat cardiovascular fetal i per estudiar la remodelació tant cardiaca com vascular durant la pràctica clínica. No obstant, alguns dels canvis hemodinàmics i vasculars subjacents no es poden avaluar clínicament, requerint de tècniques més sofisticades. El modelatge computacional de sistemes biològics es presenta com un potent instrument per superar aquest repte, per donar suport als metges i millorar la comprensió de les diferents patologies. En aquesta tesi es presenta per una banda l'ús de models computacionals tant de la circulació fetal com també de la cèl•lula cardíaca i la utilització d'eines de processat d'imatge amb la finalitat de millorar la comprensió de la remodelació cardiovascular intrauterina que té lloc a diferents escales del sistema cardiovascular fetal, i estimar les propietats hemodinàmiques específiques de cada pacient, les quals no es poden extreure directament a partir de mesures clíniques. Els resultats derivats d'aquesta tesi demostren que els models computacionals són capaços de millorar la comprensió i la detecció de la remodelació cardiovascular intrauterina mitjançant simulacions específiques del pacient.
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Maisser, Peter, and Peter Tenberge. "Advanced Driving Systems." Universitätsbibliothek Chemnitz, 2002. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200201248.
Full textAbstract:
Modern product development is a highly complex process characterized by a pronounced interdisciplinary cooperation. Interdisciplinary cooperation accompanied with firm strategic and integrating concep ts leads to innovation potentials in context of cooperative product engineering. The phrase "Mechatronics" represents exactly these novel methodological concepts in the developing process of innova tive products with highly innovative functionality and structure. The concept Mechatronics has been exemplary proven successfully in high-tech sectors. A glance at the automobile or high speed train technology gives an impressive and pursuing figure of the far reach ing Mechatronics philosophy. SME in general have not enough research and development resources to their disposal in order to comply with the ever increasing market demands. Ways out of this dilemma are strategic alliances on one hand and the education of young "Mechatronicans" at universities on the other hand. ISOM 2002 aims to contribute by inviting SME representatives and students from universities and supplementary instit utions in Saxony. The key words of Mechatronics are sensors and actuators, integrated control strategies, modeling and simulation, effective design, safety and reliability. The symposium focuses on state-of-the-art in Mechatronics, especially regarding to controlled high precision systems and particularly to novel electromechanical driving systems. It will point toward future research directions in these subjects. ISOM 2002 is intended as a forum for those engineers and researchers from universities and industry in and outside Europe who actively participate in the young field of Mechatronics and uphold the old spirit of exchanging theoretical and practical results within the scientific community<br>Die moderne industrielle Produktentwicklung ist ein hochkomplexer Prozess, der gekennzeichnet ist durch eine stark ausgeprägte interdisziplinäre Arbeit. Diese Interdisziplinarität gepaart mit fundiert en Strategie- und Integrationskonzepten führt zu erheblichen Innovationspotentialen im kooperativen Produkt-Engineering. Das Kunstwort Mechatronik steht genau für dieses neuartige methodologische Konz ept im Entwicklungsprozess innovativer Produkte mit einem hohen Integrationsgrad von Funktionalität und Struktur. Die Industrie hat in vielen High-Tech-Bereichen das Konzept Mechatronik beispielhaft realisiert. Ein Blick auf die Automobil- und Hochgeschwindigkeitszugtechnik zeigt in eindrucksvoller Weise die Tr agfähigkeit der Mechatronik-Philosophie. KMU verfügen oft nicht über das erforderliche FuE-Personal und die entsprechenden materiellen Ressourcen, um das enorme Entwicklungstempo mitzugehen. Wege zur Überwindung dieser Defizite sind strategi sche Allianzen und eine gezielte Ausbildung von Mechatronikern an Hoch- und Fachschulen. Auch hierzu soll das Symposium einen Beitrag leisten, indem insbesondere Vertreter von KMU und Studenten der ga stgebenden Universität sowie anderer Hochschuleinrichtungen Sachsens eingeladen wurden. Zu den Schlüsselworten in der Mechatronik gehören Sensoren und Aktoren, integrierte Steuerstrategien, Modellierung und Simulation, effektiver Entwurf, Sicherheit und Zuverlässigkeit. Der derzeitige Sta nd der Mechatronikforschung, vor allem mit Blick auf hochgenaue, gesteuerte mechatronische Systeme und insbesondere neuartige integrierte elektromechanische Antriebssysteme, soll im Mittelpunkt dieses Symposiums stehen. Auch zukünftige Forschungsaufgaben für die Grundlagen- und anwendungsorientierte Forschung in den genannten Themenbereichen sollen aufgezeigt werden. Das Symposium versteht sich als Treffpunkt für diejenigen Forscher und Entwickler, die in Europa an Hochschulen ebenso wie in der Industrie auf diesem Gebiet aktiv sind und sich auf einen Austausch th eoretischer, experimenteller und anwendungsspezifischer Erfahrungen, die bei der wissenschaftlichen Arbeit auf dem noch jungen Gebiet der Mechatronik erlangt wurden, freuen
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Funieru, Mariana. "Simulation of Electromechanical Actuators Using the Finite Integration Technique." Phd thesis, 2007. http://tuprints.ulb.tu-darmstadt.de/842/1/MarianaFunieru_1.pdf.
Full textAbstract:
The coupling methods allow the use of two independent meshes for mobile and fixed armature within the simulation of an electrical machine. The technique is applicable when the air gap is cylindrical or planar for a rotational or translational device respectively. Hence, the modeling of the movement of particular magnetic relays or plungers is not possible with this technique. Although both meshes are independent, it is recommended that big differences in the grid resolution are avoided. This ensures that the interpolation error is acceptable and also that the FIT stiffness matrix structure is not significantly altered. The coupling by trigonometric interpolation leads to more accurate results than computed to the coupling by linear interpolation, but requires also substantially more computational time. The force calculation is carried out at a surface in the middle of the air gap. The accuracy of the field values is improved by computing local analytical solutions relaying upon FFTs. The more accurate field values leads to better results for the forces. The simulation of electromechanical system with body motion is possible, and mechanical and electromagnetical damping effect can be considered. The coupling techniques allow to calculate cylindrical and linear machines.
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Meng-TaLin and 林孟達. "Application of Micro electromechanical system (MEMS) Processing Modeling Simulation." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/38651311642455278279.
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Wen, Fuh-Liang, and 溫富亮. "Simulation, Analysis and Application for Electromechanical Behavior of Piezoceramic Actuators." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/40728552652887606681.
Full textAbstract:
博士<br>國立清華大學<br>工程與系統科學系<br>92<br>Pervious art of ultrasonic motors (USM) or actuators are made of piezoelectric bulky material or piezoelectric stacked disc; however, the cost is so high that the commercial ultrasonic motor is quite expensive. In current study, all ultrasonic actuators are primarily bought from the hardware stores or commercial market available, such as piezoceramic buzzers and Langevin vibrators. The buzzer is composed of piezoelectric ceramic of zirconium-titanium-acid-lead material (PZT or called as piezoceramic) and bound a metal thin-disc in which is added on the constraint condition, called as a thin-disc vibrator. A Langevin vibrator comprises two PZT disks abutting against each other with two copper rings as electrodes. At the end sides of a vibrator, an aluminum block and a stainless block were screwed to the ceramic disk and the copper electrode respectively, as far from each other. When an ultrasonic AC power is applied onto a piezoceramic, the piezoceramic and its attached metal will be forced to generate mechanically extended-contracted phenomena. Electromechanical energy is transferred in wave-form-like. The piezoceramic can work within an ultrasonic frequency with the amplitude of several micrometers, which is controllable by input voltages. Therefore, it can be used as a driving actuator of a compact structure or system.
In this paper, the dynamic behaviors of piezoceramic vibrators would be patterned by means of carbon powder observation and simulated via commercial finite element software ANSYS to identify the compound mode shapes in longitudinal and transverse for the driving purpose in thin-disc actuators. Otherwise, an elastic-bouncing tester was designed to estimate the dynamic mechanism in levitated objects for an ultrasonic transportation system using Langevin vibrators. A design philosophy for piezoceramic actuators is adopted that it would be maximized in its probability of success by reducing repeatable and non-repeatable errors. Motion errors of actuators in mechanism design have to be measured and evaluated in terms of preload adjustment due to power transmission via friction contact. The successful control of ultrasonic actuator depends on the interaction of all elements that compose the system and its environment. The advanced closed-loop servo positioning control i.e. Sliding-Mode Control (SMC) is used to compensate automatically for nonlinearly mechanical behaviors such as dry friction, ultrasonic vibrating, slip-stick phenomena. In this study, in comparison of proportional-integral-derivative (PID) controller, SMC scheme has been successfully applied to position tracking to prove the excellent robust performance in noise rejection.
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Funieru, Mariana [Verfasser]. "Simulation of electromechanical actuators using the finite integration technique / von Mariana Funieru." 2007. http://d-nb.info/984937110/34.
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Wu, Jhih-Sin, and 吳志信. "Simulation of Moving Characteristics for Impact Drive MechanismBased on Electromechanical Equivalent Circuit." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/66813108428235887444.
Full textAbstract:
碩士<br>國立高雄第一科技大學<br>系統與控制工程研究所<br>94<br>Abstract
In this thesis, the investigations on the single-layer and multi-layer of
PZT elements based on Martin’s equivalent circuit were carried out.
According to the multi-layer equivalent circuit, the motion characteristics
of impact drive mechanism (IDM) were examined. By comparing the
experimental result to the simulation result based on MATLAB package,
the derived equivalent model was effectively verified. When the first
voltage waveform for the actuation of forward motion was given to the
IDM, the simulation error in displacement was obtained as 1.92%; on the
other hand, when the second voltage waveform for the actuation of
backward motion was given, the simulation error in displacement was
obtained as 0%.
The equivalent circuits studied in this thesis can represent both the
electrical and mechanical characteristics of the PZT elements
simultaneously. It will be very useful in the developments of power
sources using PZT elements, the designs of micro-generator based on
piezoelectric effect, and the characteristic studies on precision positioning
devices using PZT impact force.
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"Electromagnetic Transient and Electromechanical Transient Stability Hybrid Simulation: Design, Development and its Applications." Doctoral diss., 2016. http://hdl.handle.net/2286/R.I.38604.
Full textAbstract:
abstract: Two significant trends of recent power system evolution are: (1) increasing installa-tion of dynamic loads and distributed generation resources in distribution systems; (2) large-scale renewable energy integration at the transmission system level. A majority of these devices interface with power systems through power electronic converters. However, existing transient stability (TS) simulators are inadequate to represent the dynamic behavior of these devices accurately. On the other hand, simulating a large system using an electromagnetic transient (EMT) simulator is computationally impractical. EMT-TS hybrid simulation approach is an alternative to address these challenges. Furthermore, to thoroughly analyze the increased interactions among the transmission and distribution systems, an integrated modeling and simulation approach is essential.
The thesis is divided into three parts. The first part focuses on an improved hybrid simulation approach and software development. Compared to the previous work, the pro-posed approach has three salient features: three-sequence TS simulation algorithm, three-phase/three-sequence network equivalencing and flexible switching of the serial and par-allel interaction protocols.
The second part of the thesis concentrates on the applications of the hybrid simula-tion tool. The developed platform is first applied to conduct a detailed fault-induced de-layed voltage recovery (FIDVR) study on the Western Electricity Coordinating Council (WECC) system. This study uncovers that after a normally cleared single line to ground fault at the transmission system could cause air conditioner motors to stall in the distribu-tion systems, and the motor stalling could further propagate to an unfaulted phase under certain conditions. The developed tool is also applied to simulate power systems inter-faced with HVDC systems, including classical HVDC and the new generation voltage source converter (VSC)-HVDC system.
The third part centers on the development of integrated transmission and distribution system simulation and an advanced hybrid simulation algorithm with a capability of switching from hybrid simulation mode to TS simulation. Firstly, a modeling framework suitable for integrated transmission and distribution systems is proposed. Secondly, a power flow algorithm and a diakoptics based dynamic simulation algorithm for the integrated transmission and distribution system are developed. Lastly, the EMT-TS hybrid simulation algorithm is combined with the diakoptics based dynamic simulation algorithm to realize flexible simulation mode switching to increase the simulation efficiency.<br>Dissertation/Thesis<br>Doctoral Dissertation Electrical Engineering 2016
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Lin, Wen-Tai, and 林文泰. "Simulation of Dynamic Characteristics for a PZT Actuator Based on Electromechanical Equivalent Circuit." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/20048227992277152881.
Full textAbstract:
碩士<br>國立高雄第一科技大學<br>機械與自動化工程所<br>94<br>Abstract
In this thesis, the electromechanical property of a piezoelectric (PZT)
element was studied based on Martin equivalent circuit in which the input port
is the excitation voltage and the output ports are the generating forces of PZT
element. The equivalent circuits for both single-layer and multi-layer of PZT
elements were derived and discussed. Furthermore, the equivalent circuit of
multi-layer of PZT element was verified through both numerical and
experimental methods.
In numerical method, the simulation of the equivalent circuit was carried
out based on MatLAB package, and the parametric identification was made
based on impedance analyzer. In experimental method, the dynamic
characteristics of a PZT element being fixed on one side with different mass
loads were examined. With the consideration of the stiffness reduction
probably caused by glue and mechanical structure, the simulation errors for
the resonant frequency and the maximum velocity are 11.1% and 9.3%,
respectively. Though with simulation errors, the effectiveness of the
equivalent circuit was verified due to that both the simulation and
experimental results had the same waveforms of dynamic characteristics.
Since the analysis method studied in this thesis can simultaneously
express both the electrical and mechanical characteristics of a PZT element in
the equivalent circuit, it can be cost-effectively applied to the developments
of power source for the PZT actuator, the designs of micro-generator based on
piezoelectric effect, and also the characteristic studies on precision
positioning devices using PZT impact force.
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Kuan-WeiChen and 陳冠維. "Co-Simulation of FEM-Analytic Method-SPICE for Electromechanical Coupling Systems Applying to Optimal Design of High-Power Density Piezoelectric Energy Harvesting Modules." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/3x7g9c.
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Shao, Hung-Hsu, and 邵宏旭. "Parameters design simulations and integrated parameter test for small linear electromechanical conversion system." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/9j68b6.
Full textAbstract:
碩士<br>國立臺灣海洋大學<br>系統工程暨造船學系<br>105<br>In recent years, renewable energy has become the trend of energy policy. Taiwan is an island and the abundance natural energy resource is the marine energy. Among the several types of the marine energies, wave energy density is highest and worthy to be developed. The work to design a power conversion of point absorption nearshore wave energy conversion system is illustrated in this thesis. The power conversion system contains a linear electromechanical conversion device is demonstrated here. The float drives the conversion device to carry out periodic linear reciprocating motion to generate electricity. Due to the real generator volume is quite large and the price is higher, a small linear generator model is as the research object in this paper.The software Maxwell developed by ANSYS Inc. is used to simulate the magnetic field intensity and the induced voltage of small linear electromechanical conversion device. The space between of the inner magnet-sets and the turns and the dimension of the coils of the moving part are the variable parameters to calculate the electromechanical conversion ability. The induced electromotive force(emf) and electricity power computed by using of Matlab are also evaluated to determine the proper design parameters of the small linear electromechanical conversion device. The experiments of the best small model device were done to measure coil properties from the relationship between the moving part’s position and the induced emf.The wave energy point absorption device contains a rope which was tied with the float and was round through the pulley and connected to the moving part of the electromechanical conversion device was made in the thesis. There were two types: with fixed pulley and with moving pulley. The moving pulley type point absorption device can drive the moving part of the electromechanical conversion device faster and the induced emf was larger. Furthermore, the induced emf produce by the coils inside the moving part which was driven by the two type point absorption devices was simulated under same wave simulation condition. The results showed that electromechanical conversion device with larger space between the inner magnet-sets would own higher energy transfer ability and the electricity power of the induced emf would be larger.
Keywords: Linear generator, wave energy conversion device, point absorption nearshore wave energy conversion system, a block and tackle