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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.
1

[en] DIGITAL CONTROL OF A PNEUMATIC POSITIONING SYSTEM FOR BIOMAGNET MEASUREMENTS / [pt] CONTROLE DIGITAL DE UM SISTEMA PNEUMÁTICO DE POSICIONAMENTO PARA MEDIDAS BIOMAGNÉTICAS

GUILHERME SESTO KUHNER 11 December 2006 (has links)
[pt] Este trabalho apresenta uma solução para o problema de posicionamento automático preciso de um corpo em um plano horizontal, atendendo à restrição de não gerar campo magnético significativo junto ao objeto a ser posicionado. A motivação do trabalho reside na necessidade, por parte do Laboratório de Supercondutividade Aplicada e Magnetismo (LSAM) do Departamento de Física, de um posicionador para experimentação em magnetocardiografia. Inicialmente são discutidas as tecnologias de automação aplicáveis ao problema, justificando-se a opção por um sistema pneumático de atuação. O sistema posicionar montado é então descrito em profundidade, abordando-se os aspectos relacionados à geometria do problema em questão, materiais, montagens mecânicas e o sistema de controle digital. A seguir é apresentada uma abordagem matemática para o problema de controle de posição em malha fechada, visando à definição de uma lei de controle aplicável ao caso em estudo. Alguns resultados analíticos são obtidos para controle de sistema caracterizados por atrito Coulombiano, ao mesmo tempo em que se desenvolve um modelo para simulação numérica da dinâmica de movimento do posicionador. Com base nestas duas ferramentas, é apresentada uma discussão sobre a aplicabilidade dos controladores da família PID ao caso específico considerado. Por fim, resultados reais obtidos com a lei de controle proposta são comparadores aos resultados simulados, mostrando-se a validade e a utilidade do modelo teórico. / [en] This thesis presents a solution or the problem of automatic precise positioning of na object in the horizontal plane, not generating any significative magnetic field in the region close to the object to be positioned. The study presented was developed as part of an effort to fulfill a necessity for a positioning system for magnetocardiography experimentation in the Magnetism and Applied Supercondutivity Laboratory of the Departament of Physics of this University. A discussion over applicable automation option is presents, along with a justification for a choice of a pneumatic actuating system. The whole precise positioning assembly is described in detail, including subjects such as movement geometry, material, mechanical structures and the digital control system. A mathematical study of the closed of the closed loop position control problem is then developed, aiming to define a control algorithm applicable to the problem. Algebraic analysis is used to describe the influence of Coulomb friction over the equations of motion of a proportional position control system, while a model for simulations experiments of the assembly´s positioning dynamics is developed. These tools are used as the basis for a discussion over the applicability of the PID controlers in the case in study. Moreover, the behavior of the proposed algorithm is recorded and compared to the results of the simulations, showing the correctness and the utility of the theoretical analysis.
2

Transfer Learning for Machine Diagnostics

Al Chalati, Abdul Aziz, Naveed, Syed Asad January 2020 (has links)
Fault detection and diagnostics are crucial tasks in condition-based maintenance. Industries nowadays are in need of fault identification in their machines as early as possible to save money and take precautionary measures in case of fault occurrence. Also, it is beneficial for the smooth interference in the manufacturing process in which it avoids sudden malfunctioning. Having sufficient training data for industrial machines is also a major challenge which is a prerequisite for deep neural networks to train an accurate prediction model. Transfer learning in such cases is beneficial as it can be helpful in adapting different operating conditions and characteristics which is the casein real-life applications. Our work is focused on a pneumatic system which utilizes compressed air to perform operations and is used in different types of machines in the industrial field. Our novel contribution is to build upon a Domain Adversarial Neural Network (DANN) with a unique approach by incorporating ensembling techniques for diagnostics of air leakage problem in the pneumatic system under transfer learning settings. Our approach of using ensemble methods for feature extraction shows up to 5 % improvement in the performance. We have also performed a comparative analysis of our work with conventional machine and deep learning methods which depicts the importance of transfer learning and we have also demonstrated the generalization ability of our model. Lastly, we also mentioned a problem specific contribution by suggesting a feature engineering approach, such that it could be implemented on almost every pneumatic system and could potentially impact the prediction result positively. We demonstrate that our designed model with domain adaptation ability will be quite useful and beneficial for the industry by saving their time and money and providing promising results for this air leakage problem in the pneumatic system.
3

[pt] MODELAGEM DE UM SIMULADOR DE MOVIMENTOS PARA VEÍCULOS TERRESTRES EM ESCALA / [en] MODELING OF A SCALE GROUND VEHICLES MOTION SIMULATOR

ROBERTH WALDO ANGULO LLERENA 10 April 2012 (has links)
[pt] No presente trabalho desenvolveu-se o projeto básico de um Simulador de Movimentos em Escala, que é um equipamento utilizado para reproduzir as excitações de base provocadas pelo pavimento sobre o qual um veículo em escala trafega. Utilizando modelos consagrados na literatura, obteve-se a representação matemática do Simulador, que é tratado como 3 subsistemas acoplados entre si, mediante a aplicação de um procedimento baseado no Fluxo de Potência. Para o tratamento dos modelos em escala é empregada a Teoria de Similaridade, através da qual são determinados números adimensionais que relacionam o sistema real com o seu equivalente reduzido ou ampliado. São apresentadas 3 metodologias, das quais duas tradicionais, e uma outra que é conhecida como Método por Inspeção. Aplicam-se estes procedimentos a modelos de veículos com 1, 2, 4 e 7 graus de liberdade. Emprega-se também a Análise Dimensional para achar um modelo em escala do Simulador e do sistema completo, isto é um conjunto Simulador – Veículo acoplado. Para todos os casos são realizadas simulações para os modelos real e em escala, utilizando parâmetros típicos encontrados na literatura ou em manuais de operação de equipamentos semelhantes, com o objetivos de verificar o comportamento dos sistemas, determinar a influência da redução ou ampliação do tamanho, e validar os procedimentos empregados. / [en] In this work a Scale Ground Simulator was developed. This is na equipment used to reproduce the base motion in a vehicle, due the Road where it is running. Using a procedure based on the Power flow, coupling the 3 main Simulator subsystems, a mathematical representation for the Simulator was obtained, from classical models mentioned in the bibliography. The scale models treatment was perfomed using the Similarity Theory, that permits the determination of non dimensional numbers relating the real system with its equivalent reduced or amplified. It was presented 3 methodologies, two of them are traditional and other one which is known as Inspection Method. These procedures were applied to 1, 2, 4, and 7 degrees of freedom vehicle models. Dimensional Analysis is also used to find scale models for the Simulator and for the complete system, i.e. the coupled set Simulator – Vehicle. Simulations were made for all situations, in real and scale models, using typical parameters found in literature or in equipment operation manuals, aiming to verify the systems performance, to determine the size reduction or amplification influence of and to validate the procedures presented.
4

Designing of A Pneumatic Cushion for Supporting Standing and Sitting Process

Yu, Mingyue, Lu, Yixuan January 2018 (has links)
As is known to all, the aging problem becomes more and more serious in recent years. The issues “get into and out of a chair”, from one of the self-care tasks of aging people named Functional mobility in ADLs (Activity of daily livings), need to be solved carefully in efficient ways to help seniors and patients who have physical problems dealing with their daily life. In this previous investigation, the existing products in the market are normally quite heavy and importable. After combined with the advantages of the existing products and some improvements in portability and comfort which is related to human engineering. A Pneumatic Cushion for Supporting Standing and Sitting Process, based on airbag and pneumatic system which has been designed in this thesis, can be used by user who has physical-trouble for standing up and sitting down. Meanwhile, after being assembled with some specific extra components, it can be used as a mobility aid device. For the whole designing process, many relevant article, video sources and websites are referred for the previous researches, including Google Scholar, BTH Digital Library and YouTube. The product was designed and analysed in Inventor 2018 and the fluid dynamic simulation has been done in Abaqus. Studies involved lifting function are selected after the survey about assist appliance and aid appliance market.
5

Commercial Vehicle Air Consumption: Simulation, Validation and Recommendation / Luftförbrukning i kommersiella fordon: Simulering, validering och rekommendationer

Karanja, Bethuel, Broukhiyan, Parsa January 2017 (has links)
This report details the work done in a master thesis project. The project was conducted at the Brake Performance Department at Scania CV AB. The project involves the development of a numerical model (in Matlab) that calculates and predicts air consumption in a truck under different drive cycles. The report first details tests and experiments done so as to acquire the necessary information for the development of the model. The report then presents the model that was created and delves into tests that were conducted for its validation. A model is created that allows the user to select different component combinations on the trucks along with different loading scenarios and drive cycles. Finally the model is used to evaluate air consumption in trucks during particularly strenuous cycles. The model developed is found to be reliable and accurate to with 7% with regard to amount of air consumed. With its help, several recommendations on how air consumption in commercial vehicles can be improved are made. The best components’ combination is also found and presented. / I denna rapport beskrivs ett examensarbete som genomfördes på bromsavdelningen på Scania CV AB. Projektet innefattar utveckling av en numerisk modell (i Matlab) som beräknar och förutspår luftförbrukningen i en lastbil under olika körcykler. I rapporten beskrivs det tester och experiment som gjordes för att ta fram nödvändiga uppgifter för utvecklingen av modellen. Sedan presenteras modellen som skapades och alla valideringstester som genomfördes. Modellen är gjord så att användaren kan kombinera olika komponentkombinationer för lastbilar med olika lastningskonfigurationer och körcykler. Slutligen används modellen för att utvärdera luftförbrukningen i lastbilar under särskilt ansträngande körcykler. Den utvecklade modellen visade sig vara pålitlig och korrekt med en felmarginal på 7% med avseende på mängden luft som konsumeras. Med dess hjälp kunde flera rekommendationer ges om hur luftförbrukningen i kommersiella fordon kan förbättras. De bästa komponentkombinationerna hittades också och presenteras i denna rapport

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