Dissertations / Theses on the topic 'Linear electric machines'

Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2008.
Committee Chair: Steven Y Liang; Committee Member: Chen Zhou; Committee Member: David G Taylor; Committee Member: Min Zhou; Committee Member: Shreyes N Melkote.

The overarching goal of this work is to address the design of next-generation, high torque density electrical machines through numerical optimization using an integrated thermal-electromagnetic design tool that accounts for advanced cooling technology. A parametric thermal model of electric machines was constructed and implemented using a finite difference approach incorporating an automated, self segmenting mesh generation. A novel advanced cooling technology is proposed to improve thermal transport in the machine by removing heat directly from the windings via heat exchangers located between the winding bundles. Direct winding heat exchange (DWHX) requires high convective transport and low pressure loss. The heat transfer to pressure drop tradeoff was addressed by developing empirically derived Nusselt number and friction factor correlations for micro-hydrofoil enhanced meso-channels. The parametric thermal model, advanced cooling technique, Nusselt number and friction factor correlations were combined with a parametric electromagnetic model for electric machines. The integrated thermal-electromagnetic model was then used in conjunction with particle swarm optimization to determine optimal conceptual designs. The Nusselt number correlation achieves an R² value of 0.99 with 95% of the data falling within ± 2.5% similarly the friction factor correlation achieves an R² value of 0.92 with 95% of the data falling within ± 10.2%. The integrated thermal-electromagnetic design tool, incorporating DWHX, generated an optimized 20 kW permanent magnet electric machine design achieving a torque density of 23.2 N-m/L based on total system volume.

This dissertation focus on a Maximum Torque per Ampere (MTPA) control scheme for a non-linear synchronous reluctance motor (Sync-Rel). Due to the absence of permanent magnets, Sync-Rel motors have poor torque production capability and relatively low power factor. Therefore, it is important to maximize the torque given the maximum current of the power inverter. In the classical solution to the MTPA control problem, the d-q current components are considered equal. This solution assumes a linear magnetic circuit for the Sync-Rel motor. In practical applications, the Sync-Rel motor has a non-linear magnetic core. As a consequence, the linear solution to the MTPA problem is not the best one anymore. In this dissertation, we model a non-linear Sync-Rel motor using a simplified magnetic model, taking into account the magnetic saturation. Then, we design a non-linear MTPA controller. The Sync-Rel motor drive is simulated, and the performance of both linear and non-linear controller are compared.

Wave power is not an energy source takenadvantage of partly due to the lack of effective generatorsfor slow speeds. There is an ongoing project at the RoyalInstitute of Technology in Sweden where a transversive fluxmachine specialised for slow speeds is being developed.This paper aims to design the core of this machine toachieve high efficiency and low cost. The basic design ispresented along with the approach to the different aspectsof the manufacturing. After examining possible losses thesehave been bypassed or minimised using various methods.If this is not done properly, the losses will be too severe forthe machine to prove useful. A study of the results showthat a very high efficiency will be achieved, way superiorto that of currently existing wave power generators.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 189-208).
We study fast algorithms for linear algebraic problems that are ubiquitous in data analysis and machine learning. Examples include singular value decomposition and low-rank approximation, several varieties of linear regression, data clustering, and nonlinear kernel methods. To scale these problems to massive datasets, we design new algorithms based on random sampling and iterative refinement, tools that have become an essential part of modern computational linear algebra. We focus on methods that are provably accurate and efficient, while working well in practical applications. Open source code for many of the methods discussed in this thesis can be found at https://github.com/cpmusco.
by Christopher Paul Musco.
Ph. D.

The UE investments for the renewable source development, in order to achieve the set goals (Kyoto protocol and “20-20-20” targets), push to investigate in new technologies and to develop the existing. In this context, the cogeneration (CHP) plays a fundamental role, and in particular, the micro-CHP has wide development margins. Among the different cogeneration process, the systems driven by a free-piston Stirling engine are one of the most significant challenges in the research area. In such systems, the thermal energy, coming from primary energy source (for example renewable energy), is converted into mechanical energy through a Stirling engine, and then a linear generator converts the mechanical energy into electrical energy, finally, the generator is connected to the electric grid or to the load by means of an electric converter. The use of the linear generator, instead of the traditional systems of linear to alternating motion conversion (rod-crank system), allows achieving several advantages, including: improving the system reliability, noise and cost reduction. Finally, this kind of system, if well-designed, allows improving the system efficiency. In this thesis a linear generator, directly coupled to a free-piston Stirling engine in a CHP system, was developed and analysed. It was found, after a first phase of the study and literature review, that the most convenient choice, from the technical and economic point of view, is a single-phase tubular permanent magnet linear generator. In particular, the magnets are made of plasto-neodymium, while, for the realization of the stator magnetic circuit, due to the geometrical complexity, soft magnetic composites (SMC) materials have been considered. In order to determine the generator performance, an analysis method based on FEAs was developed. This simplified method (HFEA) allows the study and the comparison of different magnetization patterns and current supply strategies. The proposed methodology exploits the representation of the magnetization spatial harmonics through an analytical processing that allows taking into account different magnetization profile of the permanent magnets. Thus, it was possible to reconstruct the most important quantities, such as the flux density and the flux linkage, superposing the effect of each harmonic obtained through the Fourier analysis. Furthermore, a procedure, able to reproduce the effects of magnetic saturation of the mover, generally not negligible in such kind of machines, was developed. For this purpose, an appropriate surface current distribution on the yoke of the mover was introduced, in order to reproduce the demagnetizing effect due to the saturation. By means of the air gap flux density, the force provided by linear generator was calculated, while, by means of the flux density sampled on suitable points on the stator and mover yokes, the iron losses were estimated and then the machine efficiency. By means of the flux linkage the emf provided by linear generator was determined. The results show a very good agreement with corresponding FEAs. The proposed analysis method allows carrying out a parametric analysis with a lower computational effort. Thanks to this feature, different magnetization patterns, supply strategies and SMC materials can be compared in order to optimize the machine design. A prototype based on the design guidelines was built; then, a procedure based on experimental measurement was developed to characterize the electromagnetic parameters. To determine the magnetization profile of the magnets, the flux density on the mover surface was carried out by means of a Gaussmeter. As regards the SMC materials that compose the stator core, a calculation method was developed from suitable experimental elaborations, in order to determine the most important magnetic properties, such as the BH curve and core loss coefficients. From experimental results, it can be noted that the actual characteristics are poorer than those provided by the manufactured datasheets, likely due to the manufacturing processes and spurious air gaps between the SMC modules. The update electromagnetic parameters are used to determine the actual performance of the machine, particularly to estimate the efficiency, the emf and the force. Finally, a simplified model of the cogeneration system was developed in order to predict the dynamic behaviour and particularly, the actual values of the speed, output power and efficiency. This model allows developing the control strategy of the linear generator acting on the electric converter.
Gli investimenti da parte dei paesi della UE per lo sviluppo delle fonti rinnovabili, al fine di raggiungere gli obiettivi preposti (Protocollo di Kioto e Piano “20-20-20”), spingono a ricercare nuove tecnologie e a sviluppare quelle già esistenti. In questo ambito, la cogenerazione ricopre un ruolo fondamentale, ed in particolare, la micro-cogenerazione, anche in ambito domestico, presenta ancora ampi margini di sviluppo. Tra le diverse modalità di cogenerazione, i sistemi free-piston azionati da motori Stirling rappresentano una tra le sfide più importanti nell’ambito della ricerca. In tali sistemi l’energia termica, proveniente da una fonte di energia primaria (ad esempio di tipo rinnovabile), è convertita in energia meccanica attraverso un motore Stirling; successivamente un generatore lineare converte l’energia meccanica in elettrica; ed infine, un convertitore elettrico interfaccia il generatore con un carico o con la rete elettrica. L’utilizzo del generatore lineare, al posto dei tradizionali sistemi di conversione del moto da lineare ad alternato (sistema biella-manovella), consente di ottenere diversi benefici, tra cui: migliorare l’affidabilità del sistema, limitare il rumore e ridurre i costi. Infine, questo sistema, se ben progettato, permette di aumentare il rendimento dell’impianto di cogenerazione. In questo lavoro di tesi è stato progettato ed analizzato un generatore lineare da accoppiare direttamente ad un motore Stirling free-piston in un sistema di cogenerazione domestico. Dopo una prima fase di studio e ricerca bibliografica, è stato riscontrato che la scelta più conveniente dal punto di vista tecnico-economico, risulta essere quella di un generatore monofase tubolare a magneti permanenti. In particolare, i magneti sono a base di plasto-neodimio, mentre, per la realizzazione del circuito magnetico di statore, data la complessità geometrica, si sono considerati materiali magnetici compositi (SMC). Al fine di determinare le prestazioni del generatore, è stata sviluppata una metodologia di analisi, basata su analisi FEM, che permettesse lo studio ed il confronto di diverse tipologie di magnetizzazione, in particolare radiale e Halbach, e considerare diverse strategie di alimentazione. Tale metodologia (HFEA) sfrutta la rappresentazione delle armoniche spaziali di magnetizzazione attraverso un'elaborazione di tipo analitico che permette di riprodurre diverse funzioni di magnetizzazione dei magneti permanenti. In tal modo, è stato possibile ricostruire le principali grandezze di interesse (induzione e flusso concatenato) sovrapponendo l’effetto di ciascuna armonica ricavata attraverso l'analisi di Fourier. Inoltre, è stata sviluppata una procedura in grado di riprodurre gli effetti della saturazione magnetica del traslatore, generalmente non trascurabile in questo tipo di macchine. A questo proposito sono state introdotte opportune distribuzioni superficiali di corrente sul giogo del traslatore che riproducono l'effetto smagnetizzante dovuto alla saturazione. Dai valori dell’induzione al traferro, è possibile risalire al valore della forza esplicata dal generatore; mentre, dai valori dell’induzione, campionati in opportuni punti all’interno dei nuclei magnetici dello statore e del traslatore, è stato possibile stimare le perdite nel ferro e quindi il rendimento della macchina. Dal profilo del flusso concatenato è stato possibile stimare l’andamento della forza elettromotrice generata. I risultati hanno evidenziato un ottimo accordo con le corrispondenti analisi agli elementi finiti, con il vantaggio rispetto a queste di poter effettuare analisi parametriche che coinvolgono diverse grandezze progettuali con tempi di calcolo inferiori. Grazie a questa caratteristica, è stato possibile confrontare le prestazioni con varie tipologie di magnetizzazioni, strategie di alimentazione e caratteristiche di materiali SMC, effettuando una prima ottimizzazione del progetto della macchina. Dopo aver realizzato un prototipo sulla base delle indicazioni progettuali, è stata sviluppata una procedura sperimentale atta a determinare i parametri elettromagnetici del generatore, per verificarne la congruenza con le ipotesi progettuali e mettere a punto quindi i modelli per le analisi successive. Per determinare il profilo di magnetizzazione dei magneti sono state effettuate delle misure di induzione sulla superficie del materiale magnetico mediante l’uso di un Gaussmetro. Invece, per i materiali SCM che costituiscono lo statore della macchina, a partire da opportune elaborazioni sperimentali, è stato sviluppato un metodo di calcolo in grado di determinare le principali proprietà magnetiche (permeabilità, caratteristica BH e coefficienti delle perdite nel ferro per isteresi, correnti parassite ed eccesso). Dai risultati sperimentali si nota che le caratteristiche reali sono meno performanti rispetto a quelle fornite dai datasheet dei costruttori, molto probabilmente a causa dei processi di lavorazione e dei traferri spuri presenti tra i moduli di SMC. I valori delle grandezze magnetiche aggiornate sono stati utilizzati per stimare le reali condizioni di esercizio della macchina, in particolare per determinare il valore del rendimento, della tensione e della forza sviluppata dalla macchina. È poi stato sviluppato un modello semplificato che consente di riprodurre il comportamento dinamico del sistema di cogenerazione completo e di ricavare il profilo effettivo di velocità, la potenza erogata e il rendimento complessivo del sistema. Considerando l'interazione tra i singoli componenti, l'applicazione di questo modello risulta di estrema importanza per eseguire l’analisi e permette di mettere a punto la strategia di controllo del generatore agendo sul convertitore di interfacciamento con il carico.

Permanent magnet motors are known to provide higher torque and better efficiency than induction motors. They have found applications such as propulsion, motion control, traction, etc in industry. To reduce production costs by eliminating the use of position sensor, many sensorless drive schemes have emerged to fulfil this aim. Most of these sensorless algorithms utilise the back-EMF and magnetic saliency of PM motors to predict the rotor position, which is necessary for any closed loop vector controlled drive implementation. At zero or low speed operation, most sensorless schemes failed to perform well because of the inaccuracy in determining the small induced back-EMF. Contrary, at high-speed, the sampling rate of the rotor position must be sufficiently high. Moreover, the stator resistance varies after prolonged operation due to dissipated heat from the motor, which is significant when the motor is loaded and stalled. The author has proposed several sensorless algorithms to tackle these problems. Compensations are made to take account of the non-linearity of the switching devices in the inverter and the effect of dead time phenomenon. Small signal analyses of PM machine models and systems that include the speed and current regulators are carried out to ensure that they are stable for all operating conditions. Simulations and experimental results are presented to demonstrate that the sensorless drives work in practical implementations. Stability analyses are conducted to verify that the proposed sensorless algorithms are stable in both motoring and regenerating regions.

Electrical machines in electrified heavy-duty vehicles are subjected to dynamic temperature loadings during normal operation due to the different driving conditions. The Electrical Insulation System (EIS) in a stator winding is aged as an effect of these dynamic thermal loads. The thermal loads are usually high constant temperatures and thermal cycling. The high average constant thermal load is well-known in the electrical machine industry but little is known about the effect of temperature cycling. In this project, the ageing of the EIS in stator windings due to temperature cycling is examined. In this project, computational simulations of different simplified models that represent the electrical insulation system are made to analyse the thermo-mechanical stresses that is induced due to thermal cycling. Furthermore, a test object was designed and simulated to replicate the stress levels obtained from the simulations. The test object is to ease the physical testing of electrical insulation system. Testing a complete stator takes time and has the disadvantage of having a high mass, therefore a test object is designed and a test method is provided. The results from the finite element analysis indicate that the mechanical stresses induced will affect the lifetime of the electrical insulation system. A sensitivity study of several thermal cycling parameters was performed, the stator core length, the cycle rate and the temperature cycle amplitude. The results obtained indicate that the stator core length is too short to have a significant effect on the thermo-mechanical stresses induced. The results of the sensitivity study of the temperature cycle rate and the temperature cycle amplitude showed that these parameters increase the thermo-mechanical stresses induced. The results from the simulations of the test object is similar to the results from the simulations of the stator windings, which means that the tests object is valid for testing. The test method that is most appropriate is the power cycling test method, because it replicates the actual application of stator windings. The thermally induced stresses exposing the slot insulation exceeds the yield strength of the material, therefore plastic deformation may occur only after one thermal cycle. The other components in the stator are exposed to stresses below the yield strength. The thermally induced stresses exposing the slot insulation are high enough to low cycle fatigue the electrical insulation system, thus thermo-mechanical fatigue is an ageing factor of the electrical insulation system.

We develop in this work a procedure for obtaining the fatigue life of complex structures directly from Computer-Aided Design (CAD) data, without any mesh generation or regeneration as the cracks evolve. The method relies on a standard isogeometric boundary element method (IGABEM) where the same basis functions are used to both describe the geometry of the component and approximate the displacement and traction fields. The contributions of this work include: (1) Dual boundary integral equations have been applied to model 2D/3D fracture problems in the framework of IGA and that such simulations require no meshing or remeshing in the conventional sense; (2) Graded knot insertion and partition of unity enrichment have been used to capture the stress singularity around the crack tip. The contour-integral based methods and the virtual crack closure integral method are adopted to extract stress intensity factors in the framework of IGABEM; (3) Modifications on the singularity subtraction technique for (hyper-)singular integration are proposed to enhance the quadrature on distorted elements which commonly arise in IGA; (4)ANURBS-based geometry modification algorithm is developed to simulate fatigue crack growth in 2D/3D. smooth crack trajectory and crack front are obtained; (5) An implementation on trimmed NURBS is realized based on a localized double mapping method to perform the quadrature on trimmed elements. A phantom element method is subsequently proposed to model the surface crack (breaking crack) problem and the displacement discontinuity can be introduced without any reparametrization on the original patch.

Orientador: Edson Bim
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
Made available in DSpace on 2018-08-16T22:20:50Z (GMT). No. of bitstreams: 1 Franca_AlexPereira_M.pdf: 3058764 bytes, checksum: beb5e6bdbba91505ff0ef14262e6be5c (MD5) Previous issue date: 2010
Resumo: Uma abordagem preditiva global-local para o controle de um motor de indução é apresentado nesta tese. O conceito de controle preditivo diz respeito a uma classe de controladores que tem se desenvolvido muito no âmbito do controle de sistemas de conversão de energia nos últimos anos, acompanhando o desenvolvimento da capacidade computacional dos sistemas microprocessados ao longo da última década. A técnica proposta é fundamentada numa lei de controle baseada em uin modelo identificado de um motor de indução. A identificação se dá de maneira experimental a partir da simulação de um motor de indução indiretamente orientado em função do fluxo do rotor, através de um modelo fuzzy do tipo Takagi-Sugeno TS com Funções de Base Ortonormal no consequente das regras.As ações de controle locais são combinadas são combinadas pela ativação das regras do modelo local devido, e a ação de controle global resultante é aplicada ao controle de velocidade do motor de indução. Este método permite ao controlador a inclusão nos parâmetros de controle das não-linearidades e restrições inerentes ao controle do máquinas elétricas
Abstract: A predictive global-local approach technic for induction motor control is presented in this thesis. Predictive control is a very wide class of controllers that have found rather recent applications in the control of electrical machines. Research on this topic has been increased in the last years due to the possibilities of today s microprocessors used for control. The proposed technique is founded on a identified model based predictive control. The identification technique applied in this method is based on the black box modeling of a Indirect Rotor Flux Oriented Induction Motor in stationary reference system through Takagi-Sugeno-TS fuzzy models with orthonormal base functions - OBF - on the rules consequents. Control actions are matched by local activation of the model rule because local and global control action is applied to speed control of an induction motor. This method allows the inclusion in the control parameters of non-linearities and constraints inherent the control of electrical machines
Mestrado
Energia Eletrica
Mestre em Engenharia Elétrica

Considerando-se o atual estagio de desenvolvimento das máquinas elétricas, tanto em termos de ferramentas computacionais auxiliares nas simulações e nos projetos, quanto de materiais e sistemas eletrônicos de acionamento e controle, propõe neste trabalho a construção de um dispositivo eletromecânico, na classe dos motores elétricos lineares, que atenda as necessidades e se aplique a bioengenharia, mais propriamente as próteses de membro superior, na forma de acionador translacional. Este dispositivo deve substituir os sistemas que utilizam motores elétricos rotativos com mecanismos de adaptação mecânica (roldanas, vários fios, redutores), que convertem o movimento rotacional em linear. Também, os dispositivos híbridos, como atuadores eletro-hidráulicos e eletropneumáticos, que necessitam de fontes de energia de naturezas diferentes da eletroeletrônica, podem ser substituídos pelas maquinas elétricas lineares. Uma revisão dos conceitos relacionados a área de bioengenharia e feita, destacando-se os mecanismos de transmissão existentes. E apresentada uma analise comparativa entre os principais motores lineares, enfatizando-se as características construtivas, as vantagens e as desvantagens de cada um, relacionados a aplicação. A escolha da maquina a ser projetada e construída recaiu no motor linear síncrono, com imas permanentes na superfície da parte móvel, em uma estrutura tubular. Para esta maquina, e exposta uma metodologia de projeto, baseando-se nos seguintes tópicos: equacionamento do circuito magnético, cálculos de parâmetros utilizando-se o método dos elementos finitos e modelagem matemática por meio das equações por fase. Apos a etapa teórica, a construção da maquina e apresentada juntamente com os ensaios experimentais, possibilitando a comparação das características reais em relação ao projeto inicial. Por fim, o motor e aplicado ao dedo artificial, verificando-se a sua capacidade de substituição do motor rotativo.
By means of the latest technological advances of the electrical machines, both in terms of computational aids in simulations and designs, materials and electronic systems of drive and control, this work put forward the construction of an electromechanical device, in the class of the linear motors. It will be applied to bioengineering area, in particular in upper limb prostheses, in the form of a translational actuator. This linear motor must substitute the systems that use electric rotational motors with planetary gears and lead screw transmission, to convert the rotational movement into linear. The hybrid mechanisms, like electro pneumatic/hydraulic actuators, which need energy sources different from electronics, can be changed for the linear electric machines too. A review about bioengineering topics is done, where the existent mechanical mechanisms are highlighted. According to the application necessities, the advantages and disadvantages of different topologies of electric linear machines are compared and the constructive characteristics are emphasized. The tubular linear synchronous motor, with permanent magnets on the surface of the mobile part, was chosen to be applied to hand prostheses. To this machine, a design methodology is presented for calculating the motor dimensions, based on the following subjects: magnetic circuit equating, finite element analyses to evaluate parameters and machine dynamic modeling. After the theorethical stage, the construction of the machine is presented with the experimental results, allowing comparisons between the real characteristics and the initial design features of the motor. Finally, the machine is applied to an artificial finger to verify its capability to replace the rotational motor.

Il s'agit de l'analyse et la mise en oeuvre pratique de lois de commande non linéaire sur machines asynchrones. On s'est intéressé, en particulier, à la commande basée sur la passivité (PBC) dont l'idée de base est de tenir compte, dans l'élaboration du contrôleur, des propriétés physiques du procédé en utilisant la nature de systèmes d'Euler-Lagrange. Elle se résume par un façonnement de l'énergie totale du système en boucle fermée plus une injection d'amortissement faisant appel aux propriétés de dissipation d'énergie de système. On a collaboré avec deux équipes et on a utilisé deux plates-formes différentes, pour valider les résultats pratiques: 1) la mise en oeuvre de la commande en courant a été effectuée, en collaboration avec la division électromécanique de l'UTC, en utilisant le banc d'essai constitué de os9 et M68000, on a implanté deux contrôleurs d'une commande en courant (PBC et celle basée sur la linéarisation exacte) et la comparaison entre ces deux méthodes a confirmé les bonnes performances de la PBC ; 2) une version, concernant la commande en tension, de la PBC a été testé sur le benchmark du GDR d'automatique au LAN, et on a utilisé le banc d'essai équipe d'un matériel complètement différent (Simulink, Dspace)

In modern days electric power systems, the penetration of renewable resources and the introduction of free market principles have led to new challenges facing the power producers and regulators. Renewable production is intermittent which leads to fluctuations in the grid and requires more control for regulators, and the free market principle raises the challenge for power plant producers to operate their plants in the most profitable way given the fluctuating prices. Those problems are addressed in the literature as the Economic Dispatch, and they have been discussed from both regulator and producer view points. Combined Cycle Power plants have the privileges of being dispatchable very fast and with low cost which put them as a primary solution to power disturbance in grid, this fast dispatch-ability also allows them to exploit price changes very efficiently to maximize their profit, and this sheds the light on the importance of prices forecasting as an input for the profit optimization of power plants. In this project, an integrated solution is introduced to optimize the dispatch of combined cycle power plants that are bidding for electricity markets, the solution is composed of two models, the forecasting model and the optimization model. The forecasting model is flexible enough to forecast electricity and fuel prices for different markets and with different forecasting horizons. Machine learning algorithms were used to build and validate the model, and data from different countries were used to test the model. The optimization model incorporates the forecasting model outputs as inputs parameters, and uses other parameters and constraints from the operating conditions of the power plant as well as the market in which the plant is selling. The power plant in this mode is assumed to satisfy different demands, each of these demands have corresponding electricity price and cost of energy not served. The model decides which units to be dispatched at each time stamp to give out the maximum profit given all these constraints, it also decides whether to satisfy all the demands or not producing part of each of them.

The objective of this project is to develop an operational scheduling model for Sasol Mining’s coal handling facility, Sasol Coal Supply (referred to as SCS), to optimise daily operations. In this document, the specific scheduling problem at SCS is presented and solved using Mixed Integer Non-Linear Programming (MINLP) continuous time representation techniques. The most recent MINLP scheduling techniques are presented and applied to an example problem. The assumption is made that the results from the example problem will display trends which will apply to the SCS scheduling problem as well. Based on this assumption, the unit-specific event based continuous time formulation is chosen to apply to the SCS scheduling problem. The detail mathematical formulation of the SCS scheduling problem, based on the chosen technique, is discussed and the necessary changes presented to customise the formulation for the SCS situation. The results presented show that the first phase model does not solve within 72 hours. A solution time of more than three days is not acceptable for an operational scheduling model in a dynamic system like SCS. Various improvement approaches are applied during the second phase of the model development. Special Ordered Sets of Type 1 (SOS1) variables are successfully applied in the model to reduce the amount of binary variables. The time and duration constraints are restructured to simplify the structure of the model. A specific linearization and solution technique is applied to the non-linear equations to ensure reduced model solution times and reliable results. The improved model for one period solves to optimality within two minutes. This dramatic improvement ensures that the model will be used operationally at SCS to optimise daily operations. The scheduling model is currently being implemented at SCS. Examples of the input variables and output results are presented. It is concluded that the unit-specific event based MINLP continuous time formulation method, as presented in the literature, is not robust enough to be applied to an operational industrial-sized scheduling problem such as the SCS problem. Customised modifications to the formulation are necessary to ensure that the model solves in a time acceptable for operational use. However, it is proved that Mixed Integer Non-linear Programming (MINLP) can successfully be applied to optimise the scheduling of an industrial-sized plant such as SCS. Although more research is required to derive robust formulation techniques, the principle of using mathematical methods to optimise operational scheduling in industry can dramatically impact the way plants are operated. The optimisation of daily schedules at SCS by applying the MINLP continuous time scheduling technique, has made a significant contribution to the coal handling industry. Finally, it can be concluded that the SCS scheduling problem was successfully modelled and the operational scheduling model will add significant value to the Sasol Group.
Dissertation (MEng (Industrial Engineering))--University of Pretoria, 2006.
Industrial and Systems Engineering
unrestricted

When boring machines are used, large loads are exerted on their structure. The load cycles cause material fatigue on the boring machine structure. If the material fatigue can be estimated in real-time, maintenance can be planned more efficiently and the effect of different types of usage can be evaluated. Because of the many advantages of knowing the material fatigue, the goal of this thesis is to develop a model to predict the strain of a boring machine structure and then derive an estimate of the material fatigue caused by the strain. To do this several approaches using machine learning techniques are evaluated. The input signals were selected using both coherence analysis and mutual information. It was found that linear models outperform the tested non-linear model structures, and that non-linear mechanical connections cause difficulties. The signals to be modelled contained high frequency components that were not present in the available input signals. The results show that given favorable sensor positions, an estimate of the material fatigue can be made with sufficient accuracy when using a noise model and noise realization to cover the non-existent high frequency components.

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.09.01 – електричні машини та апарати. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2016. Дисертацію присвячено розробці комплексу науково-технічних рішень, спрямованих на оцінку показників лінійних електромеханічних перетворювачів ударної дії з високою магнітною сумісністю. Запропонована імітаційна математична модель лінійного електромеханічного перетворювача ударної дії, що описує взаємопов'язані просторово-часові електричні, магнітні, механічні та теплові процеси із змінними параметрами. Визначено геометричні параметри електропровідного якоря, феромагнітних осердя та екрана, при яких перетворювач забезпечує найбільші показники. Отримала подальший розвиток методика синтезу параметрів високоефективного лінійного електромеханічного перетворювача ударної дії, заснована на використанні комплексного критерію ефективності, який враховує основні показники при різних варіантах стратегії вибору. Встановлено, що кріогенне охолодження до температури рідкого азоту обмотки індуктора дозволяє збільшити ККД лінійних електромеханічних перетворювачів ударної дії в 1,6 раз, при охолодженні якоря – в 5 разів, а при одночасному їх охолодженні – в 11 разів. Розроблено конструктивні схеми лінійних електромеханічних перетворювачів ударної дії індукційно-електромагнітного типу ударної і ударно-поворотної дії. Розроблено методику експериментальних досліджень лінійних електромеханічних перетворювачів ударної дії з одночасним вимірюванням електричних і механічних показників.
The thesis for the degree of candidate of technical sciences, specialty 05.09.01 – electrical machinery and apparatus. – National technical university "Kharkiv polytechnic institute", Kharkіv, 2016. The thesis is devoted to development of complex scientific and technical solutions aimed at improving the efficiency linear electromechanical transducers with high magnetic compatibility. The proposed computer model linear electromechanical transducers with ferro-magnetic core, describing connected field-temporal electrical, magnetic, mechanical and thermal processes with variable parameters. The optimum form of section and parameters conductive anchor linear electromechanical transducers induction type. The influence of the configuration and geometrical parameters ferromagnetic core, ferromagnetic shield, electromagnetic shield and combined on screen indicators linear electromechanical transducers. Further developed methods of synthesis parameters highly linear electromechanical transducers, based on a comprehensive criteria. The effect of cryogenic cooling efficiency linear electromechanical transducers. Developed design schemes linear electromechanical transducers electromagnetic induction-type. The method of experimental studies linear electromechanical transducers simultaneous measurement of electrical and mechanical performance. Experimentally confirmed the basic theoretical training is shown linear electromechanical transducers efficiency.

Диссертация на соискание ученой степени кандидата технических наук по специальности 05.09.01 – электрические машины и аппараты. – Национальный технический университет "Харьковский политехнический институт", Харьков, 2016. Диссертация посвящена разработке комплекса научно-технических решений, направленных на оценку эффективности линейных электромеханических преобразователей ударного действия с высокой магнитной совместимости. На основе анализа научно-технических источников установлено, что линейные электромеханические преобразователи ударного действия широко при-меняются в ударно-силовых устройствах и для ускорения объектов до высоких скоростей. Однако КПД существующих линейных электромеханических преобразователей ударного действия находится на низком уровне. Кроме того, во время работы линейных электромеханических преобразователей ударного действия последние создают очень значительные импульсные магнитные поля рассеяния, которые резко негативно влияют на близко расположенное оборудование и экологическую чистоту для биологических объектов. Предложена имитационная математическая модель линейного электроме-ханического преобразователя ударного действия, описывающая взаимосвязанные пространственно-временные электрические, магнитные, механические и тепловые процессы с переменными параметрами. Определены геометрические параметры электропроводящего якоря, ферромагнитных сердечника и экрана, при которых преобразователь обеспечивает наибольшие показатели. Предложена конструкция комбинированного экрана, обеспечивающего снижение магнитных полей рассеяния до 4 раз по сравнению с ферромагнитным экраном.
The thesis for the degree of candidate of technical sciences, specialty 05.09.01 – electrical machinery and apparatus. – National technical university "Kharkiv polytechnic institute", Kharkіv, 2016. The thesis is devoted to development of complex scientific and technical solutions aimed at improving the efficiency linear electromechanical transducers with high magnetic compatibility. The proposed computer model linear electromechanical transducers with ferro-magnetic core, describing connected field-temporal electrical, magnetic, mechanical and thermal processes with variable parameters. The optimum form of section and parameters conductive anchor linear electromechanical transducers induction type. The influence of the configuration and geometrical parameters ferromagnetic core, ferromagnetic shield, electromagnetic shield and combined on screen indicators linear electromechanical transducers. Further developed methods of synthesis parameters highly linear electromechanical transducers, based on a comprehensive criteria. The effect of cryogenic cooling efficiency linear electromechanical transducers. Developed design schemes linear electromechanical transducers electromagnetic induction-type. The method of experimental studies linear electromechanical transducers simultaneous measurement of electrical and mechanical performance. Experimentally confirmed the basic theoretical training is shown linear electromechanical transducers efficiency.

Recent improvements in deep learning architectures, combined with the strength of modern computing hardware such as graphics processing units, has lead to significant results in the field of image analysis. In this thesis work, locally connected architectures are employed to reduce noise in flash X-ray diffraction images. The layers in these architectures use convolutional kernels, but without shared weights. This combines the benefits of lower model memory footprint in convolutional networks with the higher model capacity of fully connected networks. Since the camera used to capture the diffraction images has pixelwise unique characteristics, and thus lacks equivariance, this compromise can be beneficial. The background images of this thesis work were generated with an active laser but without injected samples. Artificial diffraction patterns were then added to these background images allowing for training U-Net architectures to separate them. Architecture A achieved a performance of 0.187 on the test set, roughly translating to 35 fewer photon errors than a model similar to state of the art. After smoothing the photon errors this performance increased to 0.285, since the U-Net architectures managed to remove flares where state of the art could not. This could be taken as a proof of concept that locally connected networks are able to separate diffraction from background in flash X-Ray imaging.

This diploma’s thesis discourses the cryptographic systems and ciphers, whose function, usage and practical implementation are analysed. In the first chapter basic cryptographic terms, symmetric and asymetric cryptographic algorithms and are mentioned. Also usage and reliability are analysed. Following chapters mention substitution, transposition, block and stream ciphers, which are elementary for most cryptographic algorithms. There are also mentioned the modes, which the ciphers work in. In the fourth chapter are described the principles of some chosen cryptographic algorithms. The objective is to make clear the essence of the algorithms’ behavior. When describing some more difficult algorithms the block scheme is added. At the end of each algorithm’s description the example of practical usage is written. The chapter no. five discusses the hardware implementation. Hardware and software implementation is compared from the practical point of view. Several design instruments are described and different hardware design programming languages with their progress, advantages and disadvantages are mentioned. Chapter six discourses the hardware implementation design of chosen ciphers. Concretely the design of stream cipher with pseudo-random sequence generator is designed in VHDL and also in Matlab. As the second design was chosen the block cipher GOST, which was designed in VHDL too. Both designs were tested and verified and then the results were summarized.

Abstract The proposed research of investigating the interaction between high-temperature superconductors and linear motors is introduced. Background on levitated transportation, high-temperature superconductor applications and supercon- ductor theory is given. An analytical model is developed for calculating thrust and levitation forces produced by 3-phase windings on a pair bulk high- temperature superconductors. Results produced by this model for a spacing of 1 pole-pitch and 1 2 pole-pitch are presented. In order to verify the analytical model a prototype system is built from a linear motor primary and vehicles containing 2 rows of superconductors. Two vehicles are built with different spacing between the rows of superconductors in order to investigate the ef- fect of their positioning, with respect to the pole-pitch, on the thrust forces produced. Measured forces on these two vehicles are then compared with pre- dicted values showing that the model predicts the forces with less than 5% error. Problems with the analytical model are also discussed. Finally it is con- cluded that the model developed provides insight to the relationship between high-temperature superconductors and travelling magnetic waves, and that a 1 pole-pitch separation between superconductors produces higher forces. Rec- ommendations for further development of the prototype system are also given.

This thesis covers the efforts of the design, analysis, characteristics, and construction of a Linear Brush less Doubly-Fed Machine (LBDFM), as well as the results of the investigations and comparison with its actual prototype. In recent years, attempts to develop new means of high-speed, efficient transportation have led to considerable world-wide interest in high-speed trains. This concern has generated interests in the linear induction motor which has been considered as one of the more appropriate propulsion systems for Super-High-Speed Trains (SHST). Research and experiments on linear induction motors are being actively pursued in a number of countries. Linear induction motors are generally applicable for the production of motion in a straight line, eliminating the need for gears and other mechanisms for conversion of rotational motion to linear motion. The idea of investigation and construction of the linear brushless doubly-fed motor was first propounded at Oregon State University, because of potential applications as Variable-Speed Transportation (VST) system. The perceived advantages of a LBDFM over other LIM's are significant reduction of cost and maintenance requirements. The cost of this machine itself is expected to be similar to that of a conventional LIM. However, it is believed that the rating of the power converter required for control of the traveling magnetic wave in the air gap is a fraction of the machine rating. The constructional design of the machine is such that the primary contains two 3-phase windings. One of these 3-phase systems is connected directly to the utility grid; the second 3-phase system, with a different number of poles, is connected to a power electronic converter which has the capability of providing adjustable frequency and amplitude of voltage or current. The speed of the traveling magnetic field can be varied simply by controlling the output frequency of the power electronic converter. The design of the actual machine is such that the two 3-phase systems laid in the primary of the machine are magnetically decoupled from each other because of the difference in pole number of the two systems, (e.g. 6-pole and 2-pole for the test prototype machine in our research lab). The other degree of freedom that this machine provides, is the operation of the machine under two distinct speeds by implementing the pole change technique. This mode of operation can give only discrete changes in speed, however, it provides efficient running at those speeds with a minimum of control mechanism. On the other hand, it is anticipated that the LBDFM with two actively fed windings will produce a continuously adjustable speed over a wide range. Hence, LBDFM will be superior if it can be designed to function effectively.
Graduation date: 1991

碩士
國立成功大學
系統及船舶機電工程學系碩博士班
95
All-electric injection molding machines possess advantages such as energy saving, high accuracy and clean operation, and hence have become the development trend of injection molding machines. Most all-electric injection molding machines are driven by servo motors with ball screws, which limit the operating speed and acceleration. Therefore, for high speed and large thrust, two parallel linear motors can be used to provide the joint thrust for injection. However, the mechanical coupling between the two linear motors will raise the concern about synchronization for operating under high speed and high accuracy condition. This thesis presents a new control scheme and system identification approach for linear motor synchronous control with mechanical coupling. This linear servo system and the synchronous control technique are applied to the injection unit of all-electric injection molding machines. The control modes for injection include velocity, thrust and position so that the synchronous control method with mode-switching is investigated. A synchronous controller is also designed and incorporated into the control scheme whose effectiveness in reducing synchronization error between the two linear motors is experimentally verified. A disturbance observer is developed to estimate the pressure within the mold and set the condition of filling-to-packing in the injection molding process. Therefore, the installation of sensors inside the mold becomes unnecessary.

碩士
聖約翰科技大學
自動化及機電整合研究所
101
To fulfill the customers’ diverse requirements, the manufacturer shall use the concept of flexible manufacturing to build their own production line. This purpose of the thesis focus on developing a servo linear motion system in a flexible automation machine applied on assembling electrical connectors with different poles, pitches, length, etc. The requirement of flexible user-defined distance and high positioning accuracy, endless metal convey is designed. The brand new design of linear motion system using servo-drive screw , instead of traditional cam indexer, is proposed to overcome the effect of polycon motion at end side by shaping compensation. This is not possible to be achieved with traditional of transfer system. The servo linear motion system is integrated to an automation assembly machine for electrical connector and demonstrated to increase not only the assembly efficiency but also shorten the time of changeover between different numbers of poles. The manufacturer could also reduce the numbers of automation machines by applying the modular design .

abstract: This thesis presents efficient implementations of several linear algebra kernels, machine learning kernels and a neural network based recommender systems engine onto a massively parallel reconfigurable architecture, Transformer. The linear algebra kernels include Triangular Matrix Solver (TRSM), LU Decomposition (LUD), QR Decomposition (QRD), and Matrix Inversion. The machine learning kernels include an LSTM (Long Short Term Memory) cell, and a GRU (gated Recurrent Unit) cell used in recurrent neural networks. The neural network based recommender systems engine consists of multiple kernels including fully connected layers, embedding layer, 1-D batchnorm, Adam optimizer, etc. Transformer is a massively parallel reconfigurable multicore architecture designed at the University of Michigan. The Transformer configuration considered here is 4 tiles and 16 General Processing Elements (GPEs) per tile. It supports a two level cache hierarchy where the L1 and L2 caches can operate in shared (S) or private (P) modes. The architecture was modeled using Gem5 and cycle accurate simulations were done to evaluate the performance in terms of execution times, giga-operations per second per Watt (GOPS/W), and giga-floating-point-operations per second per Watt (GFLOPS/W). This thesis shows that for linear algebra kernels, each kernel achieves high performance for a certain cache mode and that this cache mode can change when the matrix size changes. For instance, for smaller matrix sizes, L1P, L2P cache mode is best for TRSM, while L1S, L2S is the best cache mode for LUD, and L1P, L2S is the best for QRD. For each kernel, the optimal cache mode changes when the matrix size is increased. For instance, for TRSM, the L1P, L2P cache mode is best for smaller matrix sizes ($N=64, 128, 256, 512$) and it changes to L1S, L2P for larger matrix sizes ($N=1024$). For machine learning kernels, L1P, L2P is the best cache mode for all network parameter sizes. Gem5 simulations show that the peak performance for TRSM, LUD, QRD and Matrix Inverse in the 14nm node is 97.5, 59.4, 133.0 and 83.05 GFLOPS/W, respectively. For LSTM and GRU, the peak performance is 44.06 and 69.3 GFLOPS/W. The neural network based recommender system was implemented in L1S, L2S cache mode. It includes a forward pass and a backward pass and is significantly more complex in terms of both computational complexity and data movement. The most computationally intensive block is the fully connected layer followed by Adam optimizer. The overall performance of the recommender systems engine is 54.55 GFLOPS/W and 169.12 GOPS/W.
Dissertation/Thesis
Masters Thesis Electrical Engineering 2019

This thesis investigates the behavior of electron temperature gradient (ETG) driven instabilities in the Columbia Linear Machine (CLM). Building on prior work in CLM, the primary goal of this research is to produce, identify, and illuminate the basic physics of these instabilities, and explore the behavior of these instabilities under the presence of trapping and curved magnetic field lines. The first part of this thesis is focused on studying the saturated ETG mode, and the general behavior of the mode under varying levels of magnetic curvature. Measuring ETG modes can be problematic since they have large real frequencies, fast growth rates (~MHz) and small spatial scales, but carefully designed probe diagnostics can overcome these limits. In order to produce curved magnetic field lines, we modified CLM to operate with an internal movable mirror coil. We determined the temperature and density profiles under varying curvature, and measured changes in the mode structure and frequency. We found small changes in the azimuthal/poloidal structure and frequency, characterized by an increase in the m-number (m_slab~10-13 and Δ m~1), along with small changes in the axial/toroidal structure (k_ǁcurvature