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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.
81

Ferramenta pneumática para movimentação de carrocerias rodoviárias em linhas de montagem / Pneumatic tool to drive road vehicles on assembly lines

Taborda, Gustavo Gomes January 2009 (has links)
Este trabalho apresenta um estudo de caso na indústria de implementos e veículos rodoviários para solução do processo específico de movimentação de veículos e carrocerias rodoviárias nas linhas de montagem. A solução é o desenvolvimento do projeto de uma ferramenta pneumática para atender os parâmetros identificados no processo de movimentação utilizando uma metodologia de projeto. A metodologia adotada é uma composição de modelos sugeridos por autores mostrando uma sequência clara e objetiva do ciclo de vida do projeto, estruturada em quatro fases principais: Projeto Informacional, Projeto Conceitual, Projeto Executivo e Otimização de Projeto. A identificação das informações relevantes ao processo de movimentação dos produtos deu início ao Projeto Informacional. Com a finalidade de conhecer melhor as características dos processos dos potenciais usuários da ferramenta, foram levantadas as características e os parâmetros do processo. Os parâmetros abordam as principais grandezas envolvidas no sistema e suas limitações. Os dados resultantes do levantamento foram analisados gerando uma síntese de todos os parâmetros identificados para o desenvolvimento das próximas fases. No projeto conceitual, houve a evolução da solução através do detalhamento de um conceito, escolhido mediante a proposição de alternativas durante a geração de conceitos. O detalhamento é apresentado através de desenhos, segundo a diretriz de projeto orientado ao computador, com base na estrutura funcional de funcionamento da ferramenta, salientando os principais sistemas e suas configurações. Os dimensionamentos são apresentados no projeto executivo e contemplam dois tipos de análise: a análise cinemática e a análise estrutural do sistema. Na análise cinemática são apresentadas duas propostas de configuração para o motor pneumático que será utilizado na ferramenta. As propostas são expostas através de desenhos de montagem, desenhos explodidos e gráficos dos parâmetros do motor pneumático para cada uma das configurações adotadas. Nesta fase também é mostrada a construção do protótipo. Os resultados do projeto são obtidos através da realização de teste em bancada e em campo para confirmação dos parâmetros estabelecidos. Completando o ciclo de vida do projeto, propõem-se as tendências evolutivas, analisando as possíveis melhorias para a ferramenta. As conclusões do trabalho são baseadas nos resultados apresentados nos testes realizados com a ferramenta, na eficiência da metodologia adotada para o desenvolvimento do projeto e na análise do cumprimento dos objetivos definidos no trabalho. / This paper presents a case study in industry of road road vehicles for solution of the specific handling of road vehicles and truck trailers in assembly lines. The solution is to develop the design of a pneumatic tool to meet the criteria identified in the move process using a design methodology. The methodology used is a composite of models suggested by the authors showed a clear sequence and objective of the life cycle of the project, divided into four main phases: Informational Design, Conceptual Design, Executive Design and Optimization Project. The identification of information relevant to the process of transferring products initiated the Informational Design. In order to better understand the nature of the processes of potential users of the tool has been raised the characteristics and process parameters. The parameters to approach the main quantities involved in the system and its limitations. Data from the survey were analyzed by generating a synthesis of all parameters identified for the development of the next phases. In conceptual design, was the evolution of the solution through the details of a concept, chosen by proposing alternatives for the generation of concepts. The detail is presented through drawings, according to the guideline of design aided computer based functional structure operating the tool, highlighting the major systems and their configurations. The detail is presented in the executive project and includes two types of analysis: kinematic analysis and structural analysis of the system. In the kinematic analysis are presented two proposals for setting for the air motor to be used in the tool. The proposals are exposed through the assembly drawings, exploded drawings and graphics of the parameters of the air motor for each of the configurations adopted. This stage is also shown a prototype. The project results are obtained by performing test bench and field tests to confirm the established parameters. Completing the life cycle of the project, propose to the changing trends, and review possible improvements to the tool. The conclusions of the study are based on the results presented in the tests with the tool, the efficiency of the methodology used to develop the design and analysis of compliance with the defined objectives at work.
82

Pemrlovací stroj pneumatický / Bush–hammer pneumatic machine

Matula, Tomáš January 2008 (has links)
This thesis deals with the design of a pneumatic facing machine used to dress pavement surfaces aesthetically and anti-slip-wise. The introduction describes the general overview and examples of pavement. The second part deals with the analysis of the machine and its technical specifications. Further parts contain proposals for the pneumatic circuit, paint system and functional calculations. The drawing documentation has been prepared to the extent of manufacturing drawings and sets.
83

Development and initial evaluation of wireless self-monitoring pneumatic compression sleeves for preventing deep vein thrombosis in surgical patients

Cheung, William Ka Wai 05 1900 (has links)
This thesis describes the successful development and initial evaluation of a proof-of-concept wireless monitoring system for improving the effectiveness and safety of pneumatic compression therapy to help prevent deep vein thrombosis (DVT). In the development, an important objective was to make feasible the practical and commercial deployment of such improved therapy systems in future, by focusing on a cost-effective design and implementation. Over the years, pneumatic compression has been shown to be an effective solution for the prevention of DVT. However, different problems and complications related to the use of commercial pneumatic compression de-vices that typically include automatic pressure controllers and pneumatic compression sleeves have been reported. For example, one study reported a high percentage of improperly applied or nonfunctional pneumatic compression devices in routine usage. Technical problems, non-compliance, and human error were identified as the causes behind the failed therapies. Also, it was reported that dedicated in-service instruction did not improve the proper use of the pneumatic compression controllers and sleeves. In another study, significant unanticipated variations between expected and delivered pneumatic compression therapy were reported: expected therapy delivered only an average of 77.8% of the time during the therapy, and much of the time key values related to the outcome of the therapy were found to have variations great than 10%. Specific hazards have also been reported. For example, one patient developed acute compartment syndrome after wearing a pair of pneumatic compression sleeves with faulty pressure release valves. In another case, epidural analgesia masked a malfunction resulting from a reversed connection between four-way plastic tubing of the sleeves and the controller, exposing a patient to a hazardous pressure of around 300mmHg,blocking all blood flow for a prolonged period of time. Newer models of pneumatic compression sleeves and controllers from various manufacturers claim to improve therapy by, for example, increasing the peak blood flow velocity. However, there is no evidence in the published literature to support such claims. A published review of the literature from1970-2002 reached the conclusion that the most important factors in im-proving therapy with pneumatic compression devices, particularly during and after surgery, were the degree of conformance of delivered therapy to the prescribed therapy, patient compliance, and the appropriateness of the site of compression. The inability to monitor delivered therapy and patient compliance remains a problem in efforts to improve pneumatic compression therapy. The above-described problems were addressed in the successful development of the innovative prototype described in this thesis. This wireless monitoring system should improve the effectiveness and safety of pneumatic compression therapy. Also, innovative aspects of the system design allow for cost-effective integration into existing commercial controllers and sleeves. For example, an innovative and potentially patentable usage and reprocess indicator was developed for pneumatic compression sleeves to significantly improve their safety and to reduce their cost of use per patient. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate
84

Development and Testing of an Unpowered Ankle Exoskeleton for Walking Assist

Leclair, Justin January 2016 (has links)
Assistive technologies traditionally rely on either strong actuation or passive structures to provide users with increased strength, support or the ability to perform lost functions. At one end of the spectrum are powered exoskeletons, which significantly increase a user’s strength, but require strong actuators, complex control systems, and heavy power sources. At the other end are orthoses, which are generally unpowered and lightweight devices that rely on their structure’s mechanical behaviour to enhance user’s support and stability. Ideally, assistive technologies should achieve both systems’ characteristics by enhancing human motion abilities while remaining lightweight and efficient. This can be achieved by using distinctive actuators to harness gait energy, towards enhancing human mobility and performance. Pneumatic Artificial Muscles (PAMs), compliant and flexible, yet powerful and lightweight, present a unique set of characteristics compared to other mechanical actuators in human mobility applications. However, given the need of a compressor and power source, PAMs present a significant challenge, limiting their application. In contrast, PAMs can be implemented as unpowered actuators that act as non-linear elastic elements. This thesis aims to develop a wearable lightweight unpowered ankle exoskeleton, which relies on the PAM to harness gait energy and compliment the human ankle biomechanical abilities at the push off movement, thusly assisting the user in propelling the body forward during walking. Presently, limited PAM models have been developed to analyse PAM passive behaviour and to assist in designing and selecting the appropriate PAM for unpowered application. Thus, this thesis aims to develop a passive model for the PAM. To mechanically validate the proposed exoskeleton design, a prototype is fabricated, and tested within an Instron tensile machine setup. The unpowered exoskeleton has shown its ability to provide significant contribution to the ankle timed precisely to release at the push off phase of the gait cycle. Furthermore, the proposed PAM stiffness model is validated experimentally, and accounts for muscle pressure, geometry, material and stretching velocity. This enables the evaluation of the impact of various parameters on the muscle behaviour and designs the PAM accordingly for the unpowered ankle exoskeleton
85

Návrh a realizace laboratorní úlohy řízení elektro-pneumatického manipulátoru FESTO / Realization of control system for electro-pneumatic manipulator FESTO

Jurníček, Jakub January 2013 (has links)
Presented thesis deals with pneumatic actuators, PLC control systems and physical properties of compressed air. The thesis introducing short view of pneumatic components of FESTO manipulator and LabVIEW programming. Experimental results are presented on three axis FESTO manipultor programmed by NI LabVIEW.
86

Multi-state hydro-pneumatic suspension system through the use of Magneto-Rheological (MR) valves

Grobler, Jacob Frederick January 2015 (has links)
This study is focused on modifying an existing solenoid valve based semi-active hydropneumatic spring-damper system using Magneto-Rheological (MR) fluid. The MR fluid's effective viscosity can be altered by application of a magnetic field. Therefore, using a magnetic/ MR valve makes it possible to change the state of the system by simply changing the applied magnetic field. A prototype MR valve was developed to determine whether a unit small enough for installation was possible. This prototype valve was designed from first principles and properties such as pressure drop over the valve (damping) and flow blocking (for switching between spring characteristics) were measured. The measured pressure drop over the valve was higher than what was design for which was due to an incorrect assumption for the viscosity of the thixotropic MR Fluid. The flow blocking ability of the valve was determined by constant force tests. Results showed that the valve could virtually block the flow of fluid for approximately a quarter of the vehicles weight. With the second prototype, the valve design and magnetic circuit design were improved. Two valves were constructed and implemented on a prototype suspension system. The damping characteristics of the system were lower than expected, however they can be improved by changing the valve geometry. The base spring characteristics are acceptable, however the higher spring characteristics fail when a high force is exerted on the strut that exceeds the valves flow blocking capability. The response time of the valve is not yet sufficient to make the system viable for real world implementation, especially under extreme conditions that can change more rapidly than the current valves. / Dissertation (MEng)--University of Pretoria, 2015. / Mechanical and Aeronautical Engineering / MEng / Unrestricted
87

Desempenho energético e de qualidade de uma semeadora-adubadora de precisão à vácuo na implantação da cultura do milho de segunda safra /

Kolachinski, Edson Felipe January 2020 (has links)
Orientador: Paulo Roberto Arbex Silva / Resumo: O potencial produtivo das lavouras de alta performance se define no momento da semeadura e para assegurar altos rendimentos nas culturas agrícolas é importante semear com qualidade. O objetivo geral do experimento foi de estudar parâmetros de qualidade operacional, qualidade de plantio e parâmetros de desempenho agronômico ¬¬na implantação da cultura do milho (Zea mays L.), por meio de uma semeadora-adubadora equipada com dosador pneumático em sistema de plantio direto na segunda safra. O trabalho foi conduzido em lavoura comercial, em esquema fatorial duplo (3x3), combinando-se, três velocidades de deslocamento (4,2; 7,3 e 10,1 km h-1) e três pressões de vácuo do sistema pneumático de dosagem de sementes (8,0; 10,0 e 12,0 MPa). Foram realizados dois experimentos, sendo o primeiro com disco dosador de semente de 40 perfurações e o segundo com disco dosador de 36 perfurações. Os experimentos foram desenvolvidos na fazenda Rio Verdinho localizada no Município de Itararé/SP, no ano agrícola de 2018 (milho da segunda safra). O delineamento experimental utilizado foi em blocos casualizados com 4 repetições. Foram avaliados os seguintes parâmetros: uniformidade na distribuição das sementes e plântulas na linha e em profundidade, distribuição do fertilizante, mobilização e cobertura do solo, demanda energética, dados agronômicos e produtividade da cultura do milho. Para atingir os objetivos propostos, utilizou-se análise estatística: ANOVA -One Way e ANOVA- Two Way com medidas repet... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The production potential of high-performance crops is determined in the moment of sowing. To ensure high yields of agricultural crops, it is important to have a high-quality sow. Therefore, the general objective of the experiment was to study the parameters for implementation of operational quality in the cultivation of second harvest corn (Zea mays L.), by means of vacuum seeder in the no-tillage system of soy straw, and understand to what degree these factors influence the agronomic characteristics and crop productivity. The study was conducted on commercial tillage, in a double factorial scheme (3x3), matching three travel speeds (4,2; 7,3 e 10,1 km h-1), and three vacuum pressures of the pneumatic seed dosing system (8,0; 10,0 e 12,0 MPa). Two experiments were conducted, one with a 36-hole seed disc and the other with a 40-hole disc. The experiments were carried out in the commercial area Farm, Rio Verdinho, located in the county of Itareré/SP, in the agricultural year of 2018 (second harvest corn). The experimental design was conducted in random blocks with four replications. The following parameters were assessed: uniformity of seed and plant distribution in line and in depth, fertilizer distribution, mobilization and ground cover, energy demand, seed quality after passing through the machine dosing mechanism, agronomic data and corn crop yield. To achieve the proposed objectives, we used: ANOVA -One Way and NOVA- Two Way with repeated measures. In these analyzes, a sig... (Complete abstract click electronic access below) / Mestre
88

Conceptual Design of a Pilot-Scale Pressurized Coal-Feed System

Schroedter, Taylor L 01 December 2018 (has links)
This thesis discusses the results and insights gained from developing a CFD model of a pilot-scale pressurized dry coal-feed system using the Barracuda CFD software and modeling various design concepts and operating conditions. The feed system was required to transport approximately 0.00378 kg/s (30 lb/hr) of pulverized coal from a vertical hopper to a 2.07 MPa (20.4 atm or 300 psi) reactor with a CO2-to-coal mass flow ratio of 1-2. Two feed system concepts were developed and tested for coal mass flow, CO2-to-coal mass ratio, steadiness, and uniformity. Piping system components also were evaluated for pressure drop and coal roping.With the first system concept, Barracuda software model parameters were explored to observe their effect on gas and particle flow. A mesh sensitivity study revealed there exists too fine of a mesh for dual-phase flow with Barracuda due to the particle initialization process. A relatively coarse mesh was found to be acceptable since the results did not change with increasing mesh refinement. Barracuda sub-model parameters that control particle interaction were investigated. Other than the close pack volume fraction, coal flow results were insensitive to changes in these parameters. Default Barracuda parameters were used for design simulations.The gravity-fed system (first concept) relied on gravity to transfer coal from a hopper into the CO2 carrier gas. This design was unable to deliver the required coal mass flow rate due to the cohesion and packing of the particles being greater than the gravity forces acting on the particles. The fluidized bed (second concept) relied on CO2 flow injected at the bottom of the hopper to fluidize the particles and transport them through a horizontal exit pipe. Additional CO2 was added post-hopper to dilute the flow and increase the velocity to minimize particle layout. This concept was shown to decouple the fluidized particle flow and dilution CO2 flow, providing significant design and operating flexibility. A non-uniform mesh was implemented to maintain a high mesh refinement in the 0.635-cm (¼-in) diameter transport pipe with less refinement in the hopper/bed region. The two main hopper diameters evaluated measured 5.08-cm (2-in) and 15.24-cm (6-in). Successful designs were achieved for each with appropriate coal mass flow rates and CO2-to-coal ratios. The particle flow was sufficiently steady for use with a coal burner.A piping system study was performed to test pneumatic transport and the effects of pipe length and bend radius. For a 1-to-1 gas-to-particle mass flow, particle layout occurred after 30 cm of travel. Particle roping occurred to various extents depending on the pipe bend radius. Bend radii of 0.318, 60.96, and 182.88 centimeters were simulated. Roping increased with bend radius and high pressure. Greater gas flow rates increased particle flow steadiness and uniformity. A simple methodology was identified to estimate the pressure drop for different piping system configurations based on the piping components simulated.
89

Development and realization of an operator seat with active suspension / Utveckling och realisering av en operatörstol med aktiv dämpning

El Shobaki, Ahmed January 2014 (has links)
In this thesis work, generated design concepts during previous thesis work performed by Doroftei Teodor and Osorio Omar. in 2013 for an operator seat for forestry machines, have been examined. This examination was made in order to design a full-scale prototype of an operator seat featuring active suspension. With the help of this analysis, a proposal for a prototype, which decreases the effects on the operator caused by vibrations in the cabin, was developed. By damping the vibrations in the operator seat, the operator is not exposed to in-time harmful injuries and can therefore work for a longer time. With an actively suspended operator seat, new ways open up for a more effective forestry industry as the work becomes more convenient for the operator. This report presents how the work was performed. The first chapters of the report concern the background for the work, the components and subassemblies of the previous generated design concepts as well as standard components needed in order to realize an active operator seat suspension. Then, the most applicable concept is further developed to a full-scale prototype using CAD-modelling and evaluated using FEM-analysis. Based on the CAD-models, a prototype was manufactured, the vibration control is discussed and conclusions and proposals for future work are presented. Keywords: Operator, seat, active, suspension, pneumatic / I det här examensarbetet har designkoncept för en aktivt dämpad operatörstol för skogmaskiner, framtagna av Doroftei T & Osario O under tidigare examensarbete som ägt rum år 2013, analyserats för att därefter resultera i en prototyp. Med hjälp av dessa analyser har ett förslag utformats i form av en prototyp som minskar påfrestningarna hos maskinoperatören orsakade av vibrationer i hytten. Genom att dämpa vibrationerna i operatörstolen, utsätts inte operatören för skadliga påfrestningar och kan därmed arbeta längre. Med en aktivt dämpad operatörstol öppnas nya möjligheter för en effektivare skogindustri då arbetet blir bekvämare och mindre påfrestande för operatören. I den här rapporten redogörs hur arbetet gått tillväga. Rapporten inleds med bakgrunden till examensarbetet, uppbyggnaden av de tidigare framtagna designkoncepten samt nödvändiga standardkomponenter för att aktivt kunna dämpa operatörstolsvibrationerna. Därefter presenteras det mest tillämpbara konceptet som i sin tur utvecklas till en fullskalig prototyp med hjälp CAD-modellering och utvärderas med hjälp av FEM-analyser. Baserat på de CAD-modeller som tagits fram, tillverkas en fullskalig prototyp, därefter diskuteras den aktiva regleringen. Rapporten avslutas sedan med slutsatser och förslag på framtida arbete. Sökord: Operatör, stol, aktiv dämpning, pneumatik
90

Mechanical Integration of a Versatile Air Suspension Into a Powered Wheelchair

Steinkraus, Joel Michael 01 March 2012 (has links) (PDF)
Mechanical Integration of a Versatile Air Suspension into a Powered Wheelchair Joel Steinkraus It is undeniable that the vibration environment created by prolonged exposure to wheelchair use can cause discomfort for the rider and put him/her at risk of developing more severe medical conditions. While more research must be done to accurately quantify what constitues a harmful vibration environment, improved vibraiton isolation is an essential step. In order to incorporate structurally sound and effetive air suspension systems into motorized wheelchairs, a support structure is necessary. An after market wheelchair suspension system was designed, modeled, built and tested. Approximately 18 inches wide x 14 inches deep and 11 inches tall, the 50 lb suspension system uses a linear guide system and air spring to support the rider. A dashpot was added to prevent the amplification of the air spring’s natural frequency, and a pneumatic system installed to store and regulate the air pressure in the air spring and allow for a longer ride time. Testing of the system validates the mechanical durability of the design with respect to joint separation, plate bending, and bearing breakaway resistance. The penumatic system also is found to support up to 14 ingress/egress cycles before reaching a minimum functional pressure level. This value was achieved using an initial charge pressure of 100 PSI. Further environmental and user testing should be conducted to see if a greater number of ingress/egress cycles is necessary. Further development of the suspension system will incorporate a partially active controller for the air spring in order to to reduce the suspension’s transmisibility. Part respecificaitons are proposed in order to reduce system size and weight.

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