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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Efficient and high performing hydraulic systems in mobile machines

Frerichs, Ludger, Hartmann, Karl January 2016 (has links)
Hydraulic systems represent a crucial part of the drivetrain of mobile machines. The most important drivers of current developments, increasing energy efficiency and productivity, are leading to certain trends in technology. On a subsystem level, working hydraulics are utilizing effects by improving control functions and by maximum usage of energy recovery potential. Independent metering and displacement control, partly in combination with hybrid concepts, are the dominating approaches. Traction drives gain advantage from optimized power split transmissions, which consequently are being used in a growing number of applications. On the level of components, increase of efficiency and dynamics as well as power density are important trends. Altogether, design of systems and components is more and more based on modular concepts. In this sense, among others, sensors and control elements are being integrated to actuators; electric and hydraulic technology is being merged. In order to achieve maximum efficiency and performance of the entire machine, control of hydraulics has to include the whole drivetrain and the entire mobile machine in its application. In modern words, mobile hydraulic systems are a part of cyber physical systems.
12

Planejamento de sistemas de transmissão em área com fonte de geração intermitente, apoiado no uso de tecnologias avançadas. / Planning of transmission systems in an area with an intermittent generation source, based on the use of advanced technologies.

Silveira, Patrícia Oliveira da 02 May 2017 (has links)
O Brasil é um país de dimensões continentais, onde existe uma considerável distância entre a geração e os principais centros de consumo. Dessa forma, o estudo e desenvolvimento de novas tecnologias de transmissão a longas distâncias é de fundamental importância para o desenvolvimento do país. A solução mais utilizada atualmente é a transmissão em corrente alternada. Entretanto a transmissão em corrente continua também é uma solução viável para longas distâncias. O sistema brasileiro é composto principalmente por linhas 500 kV em corrente alternada (também há 230; 345; 440 e 750 kV), bem como em corrente continua (em ±600 e ±800 kV). O presente estudo apresenta uma solução de transmissão em corrente alternada por linhas de 1000 kV, que se mostrou mais econômico na transmissão de potências superiores a 3.500 MW e distâncias de 1400km. Nos próximos anos, a geração de energia elétrica no Brasil será expandida de forma significativa, ocorrerá um aumento principalmente na geração de energia eólica e solar, localizadas em sua maioria na região Nordeste do país. Esse aumento na geração exigirá a transmissão de grandes blocos de energia elétrica por distâncias significativas, devido à falta de proximidade entre a geração e os principais centros consumidores, que estão localizados no Sudeste. Neste estudo, serão mostradas as etapas de definição de condutor economicamente mais adequado e projeto da geometria da torre. Com base nos dados obtidos, será feita a avaliação do desempenho da linha 1000 kV, durante a operação normal de fluxo de carga, curtos-circuitos e estabilidade. / Brazil, a country of continental proportions, have significant distance between the power generation centers and the main consumer centers. In such way, the study and development of new transmission technologies over long distances is of fundamental importance for the development of the country. Nowadays, the most commonly used solution is alternating current transmission. However, direct current transmission is also a viable solution for long distances. The Brazilian system mainly consists of 500 kV alternating current lines (along with 230, 345, 440 and 750 kV) and direct current lines (± 600 and ± 800 kV). This study provides a solution for transmission in alternating current by lines of 1000 kV, which proved to be more economical in power transmission over 3,500 MW and distances beyond 1400km. In the coming years, the electric power generation in Brazil will expand significantly; a boost will take place mainly in wind and solar power generation, located mostly in the Northeast of the country. This generation expansion will require transmission of large blocks of electric power over considerable distances, due to the lack of proximity between generation sites and main consumer centers located in the Southeast. This study will show the setting stages of the most economically applicable conductor and tower geometry design. Based on the data obtained, the performance of the 1000 kV line will be evaluated during the regular load flow operation, short circuits and stability.
13

Planejamento de sistemas de transmissão em área com fonte de geração intermitente, apoiado no uso de tecnologias avançadas. / Planning of transmission systems in an area with an intermittent generation source, based on the use of advanced technologies.

Patrícia Oliveira da Silveira 02 May 2017 (has links)
O Brasil é um país de dimensões continentais, onde existe uma considerável distância entre a geração e os principais centros de consumo. Dessa forma, o estudo e desenvolvimento de novas tecnologias de transmissão a longas distâncias é de fundamental importância para o desenvolvimento do país. A solução mais utilizada atualmente é a transmissão em corrente alternada. Entretanto a transmissão em corrente continua também é uma solução viável para longas distâncias. O sistema brasileiro é composto principalmente por linhas 500 kV em corrente alternada (também há 230; 345; 440 e 750 kV), bem como em corrente continua (em ±600 e ±800 kV). O presente estudo apresenta uma solução de transmissão em corrente alternada por linhas de 1000 kV, que se mostrou mais econômico na transmissão de potências superiores a 3.500 MW e distâncias de 1400km. Nos próximos anos, a geração de energia elétrica no Brasil será expandida de forma significativa, ocorrerá um aumento principalmente na geração de energia eólica e solar, localizadas em sua maioria na região Nordeste do país. Esse aumento na geração exigirá a transmissão de grandes blocos de energia elétrica por distâncias significativas, devido à falta de proximidade entre a geração e os principais centros consumidores, que estão localizados no Sudeste. Neste estudo, serão mostradas as etapas de definição de condutor economicamente mais adequado e projeto da geometria da torre. Com base nos dados obtidos, será feita a avaliação do desempenho da linha 1000 kV, durante a operação normal de fluxo de carga, curtos-circuitos e estabilidade. / Brazil, a country of continental proportions, have significant distance between the power generation centers and the main consumer centers. In such way, the study and development of new transmission technologies over long distances is of fundamental importance for the development of the country. Nowadays, the most commonly used solution is alternating current transmission. However, direct current transmission is also a viable solution for long distances. The Brazilian system mainly consists of 500 kV alternating current lines (along with 230, 345, 440 and 750 kV) and direct current lines (± 600 and ± 800 kV). This study provides a solution for transmission in alternating current by lines of 1000 kV, which proved to be more economical in power transmission over 3,500 MW and distances beyond 1400km. In the coming years, the electric power generation in Brazil will expand significantly; a boost will take place mainly in wind and solar power generation, located mostly in the Northeast of the country. This generation expansion will require transmission of large blocks of electric power over considerable distances, due to the lack of proximity between generation sites and main consumer centers located in the Southeast. This study will show the setting stages of the most economically applicable conductor and tower geometry design. Based on the data obtained, the performance of the 1000 kV line will be evaluated during the regular load flow operation, short circuits and stability.
14

Conception préliminaire des actionneurs électromagnétiques basée sur les modèles : lois d'estimations et règles de conception pour la transmission de puissance mécanique. / Model based preliminary design of electromechanical actuators : estimation and design rules for mechanical power transmission

Hospital, Fabien 22 October 2012 (has links)
Dans la continuité des travaux de recherches sur les systèmes de transmission mécanique embarqués, l’objectif de cette thèse est double : approfondir les modèles d’estimations des pièces d’un Actionneur Electromécanique (EMA) et étendre la vision transversale de la conception préliminaire aux aspects dynamiques. En effet, cette recherche permet, lors de la conception préliminaire basée sur les modèles, d’adapter les choix d’architectures et de technologies vis-à-vis des performances statiques et dynamiques à atteindre. Les modèles développés à partir des lois d’échelles sont étendus et exploités afin de modéliser les pièces élémentaires de l’EMA et de faire ressortir les règles de « bonnes pratiques » en conception préliminaire. On s’intéresse en particulier au dimensionnement des EMAs dans le domaine aéronautique. Dans un premier temps, nous avons donc créé des modèles d’estimation et des métamodèles des pièces de l’EMA. A cet effet, il est décomposé en carter et pièces élémentaires qu’il intègre.Dans un second temps, nous avons établis des règles de bonne conception et des pistes de dimensionnement de l’actionneur asservi en position. Contrairement aux recherches antérieures, qui se centraient sur le dimensionnement en puissance, nous avons pris en compte la synthèse de la commande pour établir ces règles. A partir de modèles de simulations, nous qualifions et quantifions l’influence des défauts (inertie et saturations, élasticité/jeu, frottement) sur les performances limites de l’EMA. En effet, les structures de commande usuelles et le choix des éléments de contrôle-commande sont intimement liés aux performances dynamiques et à ces défauts. Enfin, afin de se doter de moyens d’essais pour identifier finement un modèle de frottement dans des conditions aéronautiques de température, un banc d'essai sur le réducteur Harmonic Drive a été conçu et mis en œuvre. Il permet également d’amorcer la validation des règles de bonne conception / In the continuity of work of research on embedded systems of mechanical transmission, this these has two objectives: to improve estimation models of Electromechanical Actuator (EMA) pieces and to extend the cross-cutting vision of preliminary design to the dynamic aspects. Indeed, in the preliminary design based on models, this research should allow to adapt the choice of architectures and technologies to static and dynamic performance to achieve. The models developed from the scaling laws will be extended and exploited to modelize elementary pieces of the EMA and to highlight rules of "good practices" in preliminary design. We focus in particular on the design of EMA in aeronautic field. In the first time, we developed estimations models and métamodèles of elementary components of EMA which was decomposed in housing and elementary pieces.In a second time, we established rules of good practices for actuator sizing in control position loop. Contrary to older researches, we take into account control synthesis to create these rules. From simulations models, we quantified the influence of technological defects of components (inertia and saturations, elasticity (backlash), friction) on EMA performances. Indeed, the usual command structures and the choice of the elements of control are intimately linked to the dynamic performance and these defects.Finally, to give test way to identify with accuracy a friction model in aeronautical conditions of temperature, a test bench of Harmonic Drive was create, integrated and implemented. It allows booting the validation of rules of good practices in preliminary design.
15

Transmissão intersetorial dos ganhos de produtividade: evidências para o Brasil no período 2000-2009 / Intersectoral transmission of productivity gains: evidence for Brazil in the period 2000-2009

Gazonato, Mariana Camarin 03 March 2016 (has links)
Submitted by Maria de Lourdes Mariano (lmariano@ufscar.br) on 2016-12-06T10:20:47Z No. of bitstreams: 1 GAZONATO_Mariana_2016.pdf: 1296907 bytes, checksum: e818dc5345f193f3602ce7d5770cd476 (MD5) / Approved for entry into archive by Maria de Lourdes Mariano (lmariano@ufscar.br) on 2016-12-06T10:21:11Z (GMT) No. of bitstreams: 1 GAZONATO_Mariana_2016.pdf: 1296907 bytes, checksum: e818dc5345f193f3602ce7d5770cd476 (MD5) / Approved for entry into archive by Maria de Lourdes Mariano (lmariano@ufscar.br) on 2016-12-06T10:21:17Z (GMT) No. of bitstreams: 1 GAZONATO_Mariana_2016.pdf: 1296907 bytes, checksum: e818dc5345f193f3602ce7d5770cd476 (MD5) / Made available in DSpace on 2016-12-06T10:21:23Z (GMT). No. of bitstreams: 1 GAZONATO_Mariana_2016.pdf: 1296907 bytes, checksum: e818dc5345f193f3602ce7d5770cd476 (MD5) Previous issue date: 2016-03-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / The main purpose of this dissertation is to analyze the capacity of sectors of the Brazilian economy to tranfer their productivity gains over the production chain, in the period 2000-2009. In this way, an adjustment is performed, through the structural decomposition technique of the input-output analysis of Dietzenbacher and Los (1998), of the method proposed by Greenhalgh e Gregory (2000). The fundamental assumptions, based on the structuralist current, are that the Industry tends to have larger increases in productivity and linkages with other segments of the economy, especially when compared to the Services. Together, these attributes would make that the productivity gains of the industrial sector propagate more intensely by the productive chain. The results show that in the period analyzed, the Agricultural and Services were the primarily responsible for transmiting these increments for the rest of the economy, instead of Industry, which moved forward losses of productivity. However, despite the Services have become more productive and transferred these gains over the production chain, the average transmission power of its segments was relatively low compared to the Industry's ability to transmit forward its productivity losses. This is because a considerable portion of the increments of the tertiary sector occurred in Personal Services, segment with reduced links in the production chain and whose goods meet, mainly, the individual consumer. The fact that the Industry ´s power transmission is, on average, higher than that of Services implies that if the industrial sector had increase its productivity, rather than decrease it, greater productivity gains would have been transmitted to the other segments of the economy that have been verified by the productivity gains of Services. However, it is important to stress that certain activities of the tertiary sector showed high potential to transfer these increments. This was the case of the Knowledge-Intensive Business Services. / O objetivo principal desta dissertação é analisar a capacidade dos setores da economia brasileira de transferir seus ganhos de produtividade ao longo da cadeia produtiva, no período 2000-2009. Neste sentido, é realizada uma adaptação, por meio da técnica de decomposição estrutural da análise de insumo-produto de Dietzenbacher e Los (1998), do método proposto por Greenhalgh e Gregory (2000). As hipóteses fundamentais, baseadas na corrente estruturalista, são de que a Indústria tende a apresentar maiores incrementos de produtividade e relações de encadeamento com os demais segmentos da economia, especialmente quando comparadas aos Serviços. Juntos, tais atributos fariam com que com os ganhos de produtividade do setor industrial se espraiassem mais intensamente pela cadeia produtiva.Os resultados apontam que no período analisado,a Agropecuária e os Serviços foram os principais responsáveis por transmitirem este sincrementos para o restante da economia, em detrimento da Indústria, a qual transferiu para frente perdas de produtividade. No entanto, apesar dos Serviços terem se tornado mais produtivos e transferido estes ganhos ao longo da cadeia produtiva, o poder de transmissão médio dos seus segmentos mostrou-se relativamente baixo quando comparado à capacidade da Indústria transmitir para frente suas perdas de produtividade. Isto porque parcela considerável dos incrementos do setor terciário ocorreu nos Serviços Pessoais, segmento com reduzidos elos na cadeia produtiva e cujos bens atendem, majoritariamente, o consumidor individual. O fato do poder de transmissão da Indústria ser, na média,superior ao dos Serviços, implica que se o setor industrial tivesse elevado sua produtividade, ao invés de diminuí-la, maiores ganhos de produtividade teriam sido transbordados para os outros segmentos da economia do que foram verificados pelo aumento da produtividade dos Serviços. É importante ressaltar, no entanto, que determinadas atividades do setor terciário apresentaram elevado potencial de transferir estes incrementos. Este foi o caso dos Serviços Empresariais Intensivos em Conhecimento.

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