• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 34
  • 5
  • 3
  • 2
  • 1
  • 1
  • Tagged with
  • 67
  • 67
  • 26
  • 25
  • 22
  • 19
  • 17
  • 15
  • 12
  • 12
  • 12
  • 9
  • 9
  • 8
  • 8
  • 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.
41

Dynamic control of the permanent magnet assisted reluctance synchronous machine with constant current angle

De Kock, Hugo Werner 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006. / This thesis is about the dynamic control of a permanent magnet assisted reluctance synchronous machine (PMA RSM). The PMA RSM in this thesis is a 110 kW traction machine and is ideal for the use in electrical rail vehicles. An application of the dynamic control of the PMA RSM in electrical rail vehicles is to reduce wheel slip. The mathematical model of the PMA RSM is derived and explained in physical terms. Two methods of current control for the PMA RSM are investigated, namely constant field current control (CFCC) and constant current angle control (CCAC). It is shown that CCAC is more appropriate for the PMA RSM. A current controller for the PMA RSM that guarantees stability is derived and given as an analytic formula. This current controller can be used for any method of current control, i.e. CFCC or CCAC. An accurate simulation model for the PMA RSM is obtained using results from finite element analysis (FEA). The accurate model is used in a simulation to verify CCAC. A normal proportional integral speed controller for the PMA RSM is designed and the design is also verified by simulation. Practical implementation of the current and speed controllers is considered along with a general description of the entire drive system. The operation of the resolver (for position measurement) is given in detail. Important safety measures and the design of the electronic circuitry to give protection are shown. Practical results concerning current and speed control are then shown. To improve the dynamic performance of the PMA RSM, a load torque observer with compensation current feedback is investigated. Two observer structures are considered, namely the reduced state observer and the full state observer. The derivation of the full state observer and the detail designs of the observer elements are given. The accurate simulation model of the PMA RSM is used to verify the operation of the observer structures and to evaluate the dynamic performance. Both observer structures are implemented practically and practical results are shown. One method of position sensorless control, namely the high frequency voltage injection method, is discussed in terms of the PMA RSM. This work is additional to the thesis but it is shown, because it raises some interesting questions regarding the dynamic control of the PMA RSM.
42

Noise in School Power Laboratories: Its Effects and Control

Schwab, David L. 08 1900 (has links)
This study was made to find the effects of noise on the human body, to measure sound levels that exist in school power laboratories, and to design and evaluate the effectiveness of two noise control devices. An accurately calibrated testing device was used to measure sound levels in an attempt to determine if excessive noise exists in school power laboratories and to find the extent to which such noise can be reduced by shielding or enclosing the engine test area. It was found that noise has undesirable physical and psychological effects on the human organism. Sixty-two and one-half per cent of the engines tested registered sound levels above 90 dBA; even so, simple, inexpensive noise control devices do control the noise levels generated in the school power laboratories.
43

Favela do Aço: pensando os dispositivos de controle da assistência social / Favela do Aço: thinking control devices of social assistance.

Vivian de Almeida Fraga 30 June 2009 (has links)
Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / Vamos falar sobre uma favela chamada Favela do Aço. Localizada na periferiada cidade do Rio de Janeiro, chega à academia a partir do meu contato com alguns moradores locais, cujas filhas participavam de um projeto executado pela Secretaria Municipal da Assistência Social. Duas características chamam a atenção na realidade dessa comunidade: o grande quantitativo de moradores em situação de rua podem ser encontrados na zona sul da cidade, e um dispositivo político inaugurado pela Secretaria chamado Pólo de Vigilância da Exclusão. Partimos da hipótese de que o Pólo de Vigilância da Exclusão foi um dispositivo político pensado como uma forma de barrar os moradores da favela de circular pelas ruas da zona sul da cidade, já que, uma vez incluídos em projetos sociais da prefeitura e mapeados por estes técnicos, o retorno para a rua pode significar a perda de projetos de transferência de renda, como o bolsa família ou outros projetos sociais.Nessa dissertação, buscamos, com a interlocução com o Serviço Social, trazer a perspectiva histórica das políticas sociais instituídas em nosso país, onde pudemos perceber a manutenção de algumas práticas construídas dentro de parâmetros sociais conservadores. Outras discussões também são contempladas nesse trabalho, onde convocamos a Sociologia, presentificada por Loïc Wacqüant, em sua análise a respeito da segregação social e a guetificação e a Filosofia, na figura de Foucault, com suas ponderações sobre os mecanismos de controle da sociedade. É nesse espírito que convido e desejo a todos uma boa leitura. / Lets talk about a slum called Slum of Steel. Located in the suburbia of the city of Rio de Janeiro, it gets to the Academy through my contact with some of the local habitants, whose daughters participated in a project done by the citys Secretary of Social Assistance. Two features call our attention about the reality of this community: the large amount of habitants living on the streets may be found in the south zone of the town, and also a politic appliance inaugurated by the Secretary named Pole of Vigilance and Exclusion. We depart from the hypothesis which the Pole of Vigilance and Exclusion has been a politic appliance thought as a way to stop slums habitants from walking by the south zone streets of the town, because, once they are included in social projects by the prefecture and also mapped by these technicians, returning to the streets might mean the loss of such money transference, such as Bolsa Família and other projects as well. In this dissertation, we search, with the exchange with Social Service, bring historical perspective of instituted social politics in our country, where we could notice the maintenance of some built-up practices within conservative social parametres. Other discussions are also contemplated in this work, where we convoke Sociology personified by Loïc Wacqüant, in his analysis towards social segregation and gethification and Philosophy, in the image of Foucault, from his concerns about controlling society mechanisms. It is in this spirit that I invite and wish you all a good read.
44

Controlling a Passive Haptic Master During Bilateral Teleoperation

Black, Benjamin Andrew 27 August 2007 (has links)
Haptic devices allow a human to interact physically with a remote or virtual environment by providing tactile feedback to the user. In general haptic devices can be classified in two groups according to the energetic nature of their actuators. Devices using electric motors, pneumatic or hydraulic cylinders or other similar actuators that can add energy to the system are considered "active." Devices using brakes, clutches or other passive actuators are considered "passive" haptic devices. The research presented here focuses on the use of passive haptic devices used during teleoperation, the remote control of a "slave" device by the haptic "master" device. An actuation scheme as well as three different control methods is developed for providing the user with haptic feedback. As a final step, the effectiveness of the controllers is compared to that of a commercially available active haptic device. Twenty subjects provide data that shows the usefulness of the passive device in three typical teleoperation tasks.
45

Modelling and control of an electric wheelchair virtual reality platform.

Motaung, Mokete Isaac. January 2014 (has links)
M. Tech. Electrical Engineering. / Discusses how to develop the kinematic and dynamic model and the controller for the 2-DOf motion platform used in an augmented reality environment for wheelchair driving. This comes as a motivation to help to train disabled and elderly people to drive wheelchairs.. With accurate inverse dynamic model, it is possible to achieve high performance control algorithms of robots and direct dynamic model is required for their simulation. The other part of this research was to model and control the roller for the feedback of the wheelchair wheels.
46

A multiple accounts approach for analyzing the effectiveness of NOx emissions controls in the GVRD airshed

Smailes, Robert L. 11 1900 (has links)
This thesis presents an analysis of air quality control initiatives in the GVRD. Starting with an examination of deteriorating regional air quality, oxides of nitrogen emissions (NOx), are the focus (as a precursor to ground level ozone.) The research demonstrates that if the status quo is maintained, episodes of ground level ozone will get worse and the effects will be far reaching and expensive. The Greater Vancouver Regional District's Air Quality Management Plan is reviewed, with emphasis on analysis and evaluation of emission reduction strategies. Emission Reduction Measures (ERMs) are various methods of reducing air pollution (including scrubbers on smoke stacks, transportation demand management, alternative fuels and motor vehicle inspection/maintenance programs.) Emission Reduction Measures are viewed as the tools that must be implemented to solve air quality problems. Environmentally, the most desirable solution would be to implement all ERMs. However, factors such as cost effectiveness and social, financial, political and customer service impacts must be considered and the best measures should be implemented first. The best solutions are those that meet as many objectives as possible while causing the least amount of negative impacts on the economy, society, government and the environment. Finding optimal solutions is a task that requires formalization of common sense. Analytical frameworks such as the cost/benefit analysis, decision analysis and the multiple account/objective analysis are considered as potential tools to help "make sense" of the complexity of air quality policy decisions. The intent is to provide useful and readily understandable information to decision makers. The Multiple Account Analysis (as used by The Crown Corporations Secretariat) is applied to an assortment of Emission Reduction Measures to help identify the "best" order for implementation. This method provides results that compare accounts of importance (such as cost effectiveness and emission reduction potential) and presents decision makers with quality information highlighting tradeoffs and preferences. In the scope of this paper, four ERMs are analyzed across accounts and the results presented in a matrix. The AirCare Program appears as the best choice for effective reduction of oxides of nitrogen when compared to alternative fuels, vanpooling and the Burrard thermal generating plant rebuild.
47

Reducing emissions of older vehicles through fuel system conversion to natural gas

Udell, Thomas Gregory 05 1900 (has links)
No description available.
48

Favela do Aço: pensando os dispositivos de controle da assistência social / Favela do Aço: thinking control devices of social assistance.

Vivian de Almeida Fraga 30 June 2009 (has links)
Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / Vamos falar sobre uma favela chamada Favela do Aço. Localizada na periferiada cidade do Rio de Janeiro, chega à academia a partir do meu contato com alguns moradores locais, cujas filhas participavam de um projeto executado pela Secretaria Municipal da Assistência Social. Duas características chamam a atenção na realidade dessa comunidade: o grande quantitativo de moradores em situação de rua podem ser encontrados na zona sul da cidade, e um dispositivo político inaugurado pela Secretaria chamado Pólo de Vigilância da Exclusão. Partimos da hipótese de que o Pólo de Vigilância da Exclusão foi um dispositivo político pensado como uma forma de barrar os moradores da favela de circular pelas ruas da zona sul da cidade, já que, uma vez incluídos em projetos sociais da prefeitura e mapeados por estes técnicos, o retorno para a rua pode significar a perda de projetos de transferência de renda, como o bolsa família ou outros projetos sociais.Nessa dissertação, buscamos, com a interlocução com o Serviço Social, trazer a perspectiva histórica das políticas sociais instituídas em nosso país, onde pudemos perceber a manutenção de algumas práticas construídas dentro de parâmetros sociais conservadores. Outras discussões também são contempladas nesse trabalho, onde convocamos a Sociologia, presentificada por Loïc Wacqüant, em sua análise a respeito da segregação social e a guetificação e a Filosofia, na figura de Foucault, com suas ponderações sobre os mecanismos de controle da sociedade. É nesse espírito que convido e desejo a todos uma boa leitura. / Lets talk about a slum called Slum of Steel. Located in the suburbia of the city of Rio de Janeiro, it gets to the Academy through my contact with some of the local habitants, whose daughters participated in a project done by the citys Secretary of Social Assistance. Two features call our attention about the reality of this community: the large amount of habitants living on the streets may be found in the south zone of the town, and also a politic appliance inaugurated by the Secretary named Pole of Vigilance and Exclusion. We depart from the hypothesis which the Pole of Vigilance and Exclusion has been a politic appliance thought as a way to stop slums habitants from walking by the south zone streets of the town, because, once they are included in social projects by the prefecture and also mapped by these technicians, returning to the streets might mean the loss of such money transference, such as Bolsa Família and other projects as well. In this dissertation, we search, with the exchange with Social Service, bring historical perspective of instituted social politics in our country, where we could notice the maintenance of some built-up practices within conservative social parametres. Other discussions are also contemplated in this work, where we convoke Sociology personified by Loïc Wacqüant, in his analysis towards social segregation and gethification and Philosophy, in the image of Foucault, from his concerns about controlling society mechanisms. It is in this spirit that I invite and wish you all a good read.
49

A multiple accounts approach for analyzing the effectiveness of NOx emissions controls in the GVRD airshed

Smailes, Robert L. 11 1900 (has links)
This thesis presents an analysis of air quality control initiatives in the GVRD. Starting with an examination of deteriorating regional air quality, oxides of nitrogen emissions (NOx), are the focus (as a precursor to ground level ozone.) The research demonstrates that if the status quo is maintained, episodes of ground level ozone will get worse and the effects will be far reaching and expensive. The Greater Vancouver Regional District's Air Quality Management Plan is reviewed, with emphasis on analysis and evaluation of emission reduction strategies. Emission Reduction Measures (ERMs) are various methods of reducing air pollution (including scrubbers on smoke stacks, transportation demand management, alternative fuels and motor vehicle inspection/maintenance programs.) Emission Reduction Measures are viewed as the tools that must be implemented to solve air quality problems. Environmentally, the most desirable solution would be to implement all ERMs. However, factors such as cost effectiveness and social, financial, political and customer service impacts must be considered and the best measures should be implemented first. The best solutions are those that meet as many objectives as possible while causing the least amount of negative impacts on the economy, society, government and the environment. Finding optimal solutions is a task that requires formalization of common sense. Analytical frameworks such as the cost/benefit analysis, decision analysis and the multiple account/objective analysis are considered as potential tools to help "make sense" of the complexity of air quality policy decisions. The intent is to provide useful and readily understandable information to decision makers. The Multiple Account Analysis (as used by The Crown Corporations Secretariat) is applied to an assortment of Emission Reduction Measures to help identify the "best" order for implementation. This method provides results that compare accounts of importance (such as cost effectiveness and emission reduction potential) and presents decision makers with quality information highlighting tradeoffs and preferences. In the scope of this paper, four ERMs are analyzed across accounts and the results presented in a matrix. The AirCare Program appears as the best choice for effective reduction of oxides of nitrogen when compared to alternative fuels, vanpooling and the Burrard thermal generating plant rebuild. / Applied Science, Faculty of / Community and Regional Planning (SCARP), School of / Graduate
50

The future and outlook of alternative fuel bus industry and its marketing strategy

Chien, Jui-Yu 01 January 2002 (has links)
According to the current governmental regulations, all diesel buses will be replaced in the United States and the European market within the next ten years. There are over 60,000 buses in the United States and each year over 3,000 new buses of approximately 40 feet in length are purchased. The bus market has a growth rate of four to five percent per year over the last two years. The improvements in technology offered by United States companies prove unsatisfactory in terms of bus performance and the emissions of new buses. The energy crisis in the United States and concern over the health hazards of the diesel fuel exhaust gases and particulates, alternative fuel vehicles are in great demand in the transit market world wide.

Page generated in 0.0459 seconds