31 |
NEUTRON ACTIVATION ANALYSIS OF MANGANESE, IRON AND ZINC IN A RODENT MODEL OF DYSMYELINATIONLobo, Lianne R. 10 1900 (has links)
<p>Transition metals such as manganese (Mn), iron (Fe) and zinc (Zn) are some of the essential metals for normal CNS development and function. Each must be present at specific levels to avoid deficiencies or toxic excess. The research in this thesis investigates the role of transition metals in diseases in which myelin is lost in the central nervous system (CNS). A loss of myelin is termed demyelination, and an example of a disease with prominent demyelination is multiple sclerosis. An incomplete formation of myelin sheaths is termed dysmyelination. This thesis focused on the measurements of manganese, iron and zinc concentrations in a rodent model of dysmyelination; the Long Evans Shaker (<em>les</em>) rat.<strong></strong></p> <p>The Long Evans Shaker (<em>les</em>) rat is a fragile, severely dysmyelinated rodent model with body tremors at a young age and severe ataxia in older rats. The mutation causing the severe dysmyelination in these rats is transmitted as an autosomal recessive trait. With a lifespan of 4 to 5 months, the <em>les</em> rat is markedly deficient in myelin in the CNS, where most axons are entirely naked and the remaining ones are surrounded by a loosely woven, thin myelin sheath.</p> <p>In this thesis we studied alterations in manganese, iron and zinc transition metal levels in 3 and 16-week-old <em>les</em> rats and their age-matched control counterparts. Using neutron activation analysis (NAA), manganese measurements were made in the brain, spinal cord and visceral organs using an existing protocol, while a new assay was developed for iron and zinc measurements that were made in the spinal cord tissues. The higher trend in manganese concentration observed within the 3 and 16 week old <em>les</em> rats in comparison to the controls, where there was a significant increase (ples cerebellum, supports evidence suggesting that manganese levels are associated with astrogliosis. Whereas for iron and zinc, which were measured in the spinal cord tissues, there was also an overall increase in the levels of these metals in the <em>les</em> mutant strain when compared to the controls; however, only significant increases in zinc concentration within the 16 week old <em>les </em>spinal cords were observed.</p> <p>The characterization of the <em>les</em> rodent model mutation and its biochemical abnormality will advance our understanding of not only the process of myelination, but also diseases related to aberrant myelination or the maintenance of myelin sheaths.</p> / Master of Science (MSc)
|
32 |
MUTANT DROSOPHILA LACKING SIALIC ACID EXHIBIT NEURODEGENERATION AND METABOLIC DYSFUNCTION LEADING TO A DIABETIC STATEAKAN, ILHAN January 2012 (has links)
Sialylation, a posttranslational modification of both glycolipids and glycoproteins, is typically found on the terminal positions of glycan chains. Unique among most other sugars, sialic acids are nine carbon sugars that are negatively charged and undergo a variety of side group modifications, which contribute to its role in cell-cell interactions and receptor recognition. While the majority of Drosophila glycoproteins do not terminate in sialic acid compared to mammalian glycoproteins, a sialic acid synthetic pathway is present in Drosophila but it is developmentally regulated and appears to be restricted to the nervous system (Kim et al., 2002; Koles et al., 2004). In order to investigate the role of the sialic acid pathway in Drosophila, we generated a null mutation of the sialic acid synthase gene (SAS) by imprecise excision of a nearby transposable element. Homozygous null flies exhibit partial lethality, male sterility and undergo age dependent neurodegeneration as evidenced by loss of locomotion and increased vacuolization in the brain. Mutant flies also have a shortened life span and display increased sensitivity to heat as they age. To identify protein targets of sialylation that possibly contributed to these phenotypes, a very sensitive solid-phase extraction method was used to capture sialylated glycopeptides from head extracts of wild type and SAS null flies. In collaboration with M. Betenbaugh and H. Zhang at Johns Hopkins University, I identified three sialylated peptides; the major peptide target was derived from the Shaker voltage-dependent potassium channel. The other two peptides were encoded by genes of unknown function. Electrophysiological measurements performed on control and SAS mutant larvae at the pre- and post-synaptic larval neuromuscular junction (in collaboration with T. Dean and A. Seghal, University of Pennsylvania) showed that loss of sialylation induced a depolarizing shift in the gating parameters of the Shaker ion channels, similar to what was previously reported in mammalian cell culture (Johnson and Bennett, 2007). Pre-synaptic neurons from the mutants displayed a two to three fold increase in the number of miniature excitatory peaks suggesting that the neurons were hyperactive. Since Shaker is a major target of sialylation in brain neurons, I suggest that the loss of sialylation of Shaker plays a major role in the neurodegeneration phenotype observed in our SAS null mutant flies. SAS mutant flies are unusually sensitive to starvation, typical of flies that cannot maintain metabolic homeostasis. Upon 24 h of starvation, mutant flies differed from control flies in that they consumed most of their triglyceride stocks, they displayed poor locomotion, had smaller sized cells in their fat body, and reduced their glycogen stores significantly. Mutant flies expressed and likely secreted an excess of insulin like protein, hyperinsulinemia, for the first five days after eclosion. However, as the flies aged (14-21 days) they had high hemolymph sugar, low insulin like protein expression and fewer number of insulin producing cells. All these phenotypes are similar to diabetic patients, as diabetic patients also have metabolic inflexibility, high blood sugar, low insulin secretion, and fewer number of insulin producing cells. It is now known that the Shaker homolog KV1 is expressed in human pancreatic β cells which secrete insulin (Ma et al., 2011). I propose that in our mutants the failure to sialylate the Shaker channel, which is known to be present in insulin producing cells (IPC ), will result in those cells secreting an excess of insulin , which in turn causes the metabolic defects leading to a diabetic state. By studying our sialic acid null mutants we can obtain useful information about how diabetes develop. Using the powerful genetics of flies, we can perform screens to identify novel genes that either enhance or reduce the sensitivity to starvation of our SAS mutants and thus play a role in the development or potential treatment of diabetes / Biology
|
33 |
Examensarbete Saz : stilanalysarbete Mohamed Abdelkarim- Bizqens prinsAli Shaker, Alex Ali January 2016 (has links)
Sammanfattning Efter att ha skrivit biografin om Mohamad Abdelkarim och analyserat hans olika stilar genom att skriva noter till melodierna så har jag förstått ännu mer varför Mohamad anses vara en av dem som genom historien haft bäst teknik och känsla för sitt instrument, Bizq. Han behärskade instrumentet och var väldigt självsäker i sin musik. Han hade rest runt, bekantat sig med många olika kulturer och tagit influsenser av respektive kultur, vilket gör honom till en unikt mångsidig instrumentalist och komponist. Jag har lärt mig mycket teknik om instrumentet genom att försöka spela låtarna som Mohamad gjorde. / Biografi Ali shaker Ali Ali känd som Ali Shaker, föddes år 1985 i staden Hassake i den syriska delen av Kurdistan. Ali växte upp i en musikalisk familj- hans pappa sjöng kurdisk folkmusik på fritiden och hans storebror spelade saz och buzuq. Själv började Ali spela darbukka, arabisk trumma, samtidigt som han började skolan. När Ali skulle börja andra klass, dvs. när han var 8 år gammal började han spela trummor på bröllop och mindre fester för att kunna försörja sin familj. Det hände ofta att Ali blödde i händerna då han var tvungen att spela i flera timmar- det var ju hans jobb. När Ali var 13 år gammal började han spela saz då det var lättare instrument att spela i flera timmar i sträck, det var därför han började spela saz på bröllop. Dessutom är instrumentet en viktig del av den kurdiska vardagen- det finns nästan i varje kurdiskt hem i Syrien. Vid 17 års ålder började ryktet om en duktig sazspelare sprida sig i Hassake-regionen. 19 år gammal kallas Ali in för att göra lumpen i huvudstaden Damaskus. Ali hade tur som blev placerad just där, då alla kända studior var där. Ali började visa framfötterna och snart var han känd bland de flesta verksamma musiker i landet. Efter lumpen började Ali även verka utomlands. I bl.a. Beirut och Dubai, som är navet för arabisk popmusik har Ali medverkat i en otalig mängd låtar och skivor, tillhörande många av arabvärldens största stjärnor. En dröm kvarstod dock- att studera musik på en hög akademisk nivå, en dröm som inte var möjlig tidigare efetrsom Ali var tvungen att jobba hela tiden och hjälpa sin familj. I början på år 2012 flyttade Ali till Sverige, efter att ha gift sig med den kända kurdiska sångerskan Narin Feqe. Han började snabbt att ta de steg som krävdes för att förverkliga sin dröm och studera musik, och det gick snabbt. År 2013 började Ali studera folkmusik från andra kulturer på Kungliga Musikhögskolan.
|
34 |
Interação entre os excitadores de vibração e a estrutura sob estudo em ensaios com múltipla excitação / Interaction between electrodynamic exciters and the structure under test in multiple input testsOliveira, Leopoldo Pisanelli Rodrigues de 30 April 2003 (has links)
Apresenta-se um estudo analítico e experimental do fenômeno de interação entre excitadores eletrodinâmicos e a estrutura em ensaios de vibração e discutem-se causas e efeitos desta interação na qualidade dos resultados obtidos. Inicialmente, realizam-se simulações numéricas que contemplam as características mecânicas e eletromagnéticas do excitador. Definido o modelo para o excitador, realizam-se simulações de teste com estruturas, dos quais obtêm-se as forças de entrada e funções de resposta em freqüência (FRFs) estimadas que serão comparadas às FRF reais da estrutura. Posteriormente, considera-se a inclusão de graus de liberdade rotacionais aos modelos do excitador e da estrutura. Finalmente, as simulações de testes com múltipla excitação têm como objetivo principal o de observar os fenômenos de queda de força de excitação e seus efeitos sobre as FRFs estimadas. Com os resultados experimentais verificam-se os principais fenômenos da interação excitador / estrutura observados nas simulações numéricas tais como a queda da força de excitação e a influência da dinâmica do conjunto excitador / amplificador na resposta da estrutura. Através dos resultados experimentais obtidos com uma viga metálica observam-se os principais efeitos previstos pelas simulações. Ainda, comparam-se as alterações nos dados obtidos com outros métodos de excitação tais como, martelo impulsivo e excitação em malha fechada. Testes realizados com diferentes estruturas, como um pneumático e um chassi tubular, vêem complementar os dados obtidos até então para excitação com um único excitador. Os testes realizados com a finalidade de validar os modelos que incluem graus de liberdade rotacionais mostram que tais grandezas não podem ser negligenciadas, principalmente no que se referem aos testes com excitação via base, em que o item de teste é montado diretamente sobre o excitador. Ainda, verificam-se os resultados obtidos com diversos estimadores de FRFs em ensaios com acréscimo de ruído aos sinais de entrada e saída. Os resultados experimentais realizados com dois excitadores mostram os mesmos efeitos observados nas simulações, em geral uma redução na queda da força de excitação e uma melhor distribuição de energia pela estrutura. / An analytical and experimental study of the interaction between electrodynamic exciters and the structure under test is presented, and the causes and effects of this interaction on the obtained data quality are discussed. Initially, some numerical simulations are performed concerning the shaker\'s mechanical and electrical features. Once the shaker model is defined, some tests with structures were simulated in order to obtain the input forces and the estimated frequency response functions to be compared with the measured FRFs. Afterwards, the rotational degrees of freedom were included in the shaker and structure models. Ending this section, tests with multiple input forces were simulated. The experimental results confirm most of the phenomena observed in the simulation section, such as the input force drop-off and the influence of the shaker / power amplifier assembly on the structure\'s response. The tests conducted with a steal beam confirmed the effects predicted by the simulations. Therefore, these results are compared with others, obtained from alternative methods such as impact test and closed loop shaker tests. Tests with structures like a truck tyre and a tubular chassis complement the assessment of single input tests. The tests performed with the objective of validating the models considering rotational degrees of freedom show that these quantities cannot be neglected, mainly when base driven tests are concerned. Also, the efficiency of FRF estimators applied to shaker tests, in the presence of noise on the input and output channels is verified experimentally. The multiple input tests corroborate the effects observed in the simulations, in general, a reduction of the droopoff on the force and an improvement on the input energy distribution on the structure.
|
35 |
Immobilizing Mutation in an Unconventional Myosin15a Affects not only the Structure of Mechanosensory Stereocilia in the Inner Ear Hair Cells but also their Ionic ConductancesSyam, Diana 01 January 2014 (has links)
In the inner and outer hair cells (OHCs) of the inner ear, an unconventional myosin 15a localizes at the tips of mechanosensory stereocilia and plays an important role in forming and maintaining their normal structure. A missense mutation makes the motor domain of myosin 15a dysfunctional and is responsible for the congenital deafness DFNB3 in humans and deafness and vestibular defects in Shaker-2 (Sh2) mouse model. All hair cells of homozygous Shaker-2 mice (Myo15sh2/sh2) have abnormally short stereocilia, but, only stereocilia of Myo15sh2/sh2OHCs start to degenerate after the first few days of postnatal development and lose filamentous tip links between stereocilia that are crucial for mechanotransduction. The exact mechanisms of this degeneration are unknown even though they may underlie DFNB3 deafness in humans. We hypothesize that structural abnormalities in Myo15sh2/sh2 OHCs may alter the mechanical forces applied to the mechano-electrical transduction (MET) channels resulting in abnormal ionic homeostasis, which may lead to eventual degeneration of Myo15sh2/sh2 OHCs. Therefore, we investigated the ionic conductances and integrity of mechanotransduction apparatus in Myo15sh2/sh2 OHCs. Surprisingly, we found that myosin 15a-deficiency is associated not only with structural abnormalities of OHC stereocilia but also with alterations of voltage-gated ion conductances.
|
36 |
Experimental Determination Of Transfer Functions For A Car Body-in-whiteSenturk, Sabri 01 April 2004 (has links) (PDF)
Vibration generated from various sources (engine, road surface, tires, exhaust, etc.) should be considered in the design of a car body. These vibrations travel through transfer systems (drivetrain, suspension, body, etc.) to the steering wheel, seats and other areas where it is detected by the passengers of the vehicle. Transmission routes must be studied and efforts made to keep transfer systems from amplifying vibration and to absorb it instead. Since the superior vibration transfer system is the car body, finite element analysis and experimental vibration analysis are performed on car body-in-white. Body vibration analysis entails understanding and improving the body&rsquo / s dynamic characteristics that act as vibration transfer channels.
In the previous study, a finite element model has been created for a car body-in-white available in Automotive Laboratory (Mechanical Engineering Department, Middle East Technical University, Ankara) and its natural frequencies and mode shapes have been determined using finite element analysis software. In this study, vibration tests have been performed on actual car body-in-white. Frequency response functions between 34 response locations and force application point have been measured. Using these frequency response functions, natural frequencies and mode shapes of the body-in-white have been determined. Finite element analysis and experimental results have been compared to evaluate the finite element model reliability.
|
37 |
Implementação de um sistema de controle heurístico de aceleração e tensão mecânica para ensaios em shaker eletrodinâmicoDonadel, Juliane January 2012 (has links)
Por décadas, a qualidade de produtos é determinada por testes em ambientes de laboratório, como testes de acelerados de vibração, ciclagem térmica, choque mecânicos ou térmicos, entre outros. Porém, mais recentemente um novo tipo de técnica tem adquirido a confiança de pesquisadores e projetistas. As técnicas conhecidas como HALT (Highly Accelerated Life Testing) e HASS (Highly Accelerated Stress Screening), ou seja, testes acelerados e amplificados que submetem produtos a condições severas, têm mostrado sua importância e eficiência no âmbito da detecção de falha em produtos ainda na fase de produção. Este trabalho tem por objetivo desenvolver e implementar um algoritmo de controle baseado em métodos heurísticos para ser usado em ensaios acelerados usando um Shaker eletrodinâmico. Este controlador deve ser robusto o suficiente para se adequar a possíveis efeitos de ressonância do shaker que podem vir a alterar a dinâmica do sistema, inviabilizando controles tradicionais com parâmetros fixos. Os resultados obtidos através de vários ensaios mostraram que ambos os sistemas de controle são eficientes, pois o erro entre o sinal desejado (tensão mecânica ou aceleração) e os medidos experimentalmente, tendem rapidamente a zero não apresentando sobressinais consideráveis ou erro em regime permanente, tanto para frequência fixa quanto para varredura de frequência. A comparação entre o controlador tradicional PID e o controle heurístico baseado em Lógica Fuzzy, que foram aplicados no shaker eletrodinâmico, comprova que, para mudanças na amplitude do sistema, o controle Fuzzy apresentou menor sobressinal, o que é mais favorável do ponto de vista mecânico. Logo, a metodologia proposta pode ser aplicada para ensaios HALT/HASS com o intuito de obter grandes vibrações e, por conseguinte tensões, para identificar possíveis falhas de projeto e então, poder corrigi-las. / For decades, product quality is determined by environmental tests, such as accelerated vibration tests, thermal cycling, mechanical or thermal shock, and others. However, more recently a new type of test has gained the trust of researchers and designers. Known techniques such as HALT (Highly Accelerated Life Testing) and HASS (Highly Accelerated Stress Screening), or accelerated and amplified testing that submit products to severe conditions have shown their importance in the efficiency and fault detection in products still in production phase. This study aims to develop and implement a control algorithm based on heuristic methods in order to be used in a system of accelerated tests in an electrodynamic shaker. This controller must be robust enough to fit the resonance effects of the shaker that it can change the system dynamic, invalidating traditional controls with fixed parameters. The results obtained through tests showed both control systems are efficient, because the error between desired signal (mechanical stress and acceleration) and the experimentally measured tend rapidly to zero, there aren’t overshoots or steady state errors, both for constant frequency and for sweep frequency. Comparing the PID traditional control and the Logic Fuzzy control, applied in electrodynamic shaker, we proved that to change system amplitude, the fuzzy control presented lower overshoot, that is favorable from the standpoint of mechanical. Therefore, the methodology proposed can be applied to HALT/HASS tests in order to obtain large vibrations and, consequently stress, to identify possible flaws in the design and correct them.
|
38 |
Implementação de um sistema de controle heurístico de aceleração e tensão mecânica para ensaios em shaker eletrodinâmicoDonadel, Juliane January 2012 (has links)
Por décadas, a qualidade de produtos é determinada por testes em ambientes de laboratório, como testes de acelerados de vibração, ciclagem térmica, choque mecânicos ou térmicos, entre outros. Porém, mais recentemente um novo tipo de técnica tem adquirido a confiança de pesquisadores e projetistas. As técnicas conhecidas como HALT (Highly Accelerated Life Testing) e HASS (Highly Accelerated Stress Screening), ou seja, testes acelerados e amplificados que submetem produtos a condições severas, têm mostrado sua importância e eficiência no âmbito da detecção de falha em produtos ainda na fase de produção. Este trabalho tem por objetivo desenvolver e implementar um algoritmo de controle baseado em métodos heurísticos para ser usado em ensaios acelerados usando um Shaker eletrodinâmico. Este controlador deve ser robusto o suficiente para se adequar a possíveis efeitos de ressonância do shaker que podem vir a alterar a dinâmica do sistema, inviabilizando controles tradicionais com parâmetros fixos. Os resultados obtidos através de vários ensaios mostraram que ambos os sistemas de controle são eficientes, pois o erro entre o sinal desejado (tensão mecânica ou aceleração) e os medidos experimentalmente, tendem rapidamente a zero não apresentando sobressinais consideráveis ou erro em regime permanente, tanto para frequência fixa quanto para varredura de frequência. A comparação entre o controlador tradicional PID e o controle heurístico baseado em Lógica Fuzzy, que foram aplicados no shaker eletrodinâmico, comprova que, para mudanças na amplitude do sistema, o controle Fuzzy apresentou menor sobressinal, o que é mais favorável do ponto de vista mecânico. Logo, a metodologia proposta pode ser aplicada para ensaios HALT/HASS com o intuito de obter grandes vibrações e, por conseguinte tensões, para identificar possíveis falhas de projeto e então, poder corrigi-las. / For decades, product quality is determined by environmental tests, such as accelerated vibration tests, thermal cycling, mechanical or thermal shock, and others. However, more recently a new type of test has gained the trust of researchers and designers. Known techniques such as HALT (Highly Accelerated Life Testing) and HASS (Highly Accelerated Stress Screening), or accelerated and amplified testing that submit products to severe conditions have shown their importance in the efficiency and fault detection in products still in production phase. This study aims to develop and implement a control algorithm based on heuristic methods in order to be used in a system of accelerated tests in an electrodynamic shaker. This controller must be robust enough to fit the resonance effects of the shaker that it can change the system dynamic, invalidating traditional controls with fixed parameters. The results obtained through tests showed both control systems are efficient, because the error between desired signal (mechanical stress and acceleration) and the experimentally measured tend rapidly to zero, there aren’t overshoots or steady state errors, both for constant frequency and for sweep frequency. Comparing the PID traditional control and the Logic Fuzzy control, applied in electrodynamic shaker, we proved that to change system amplitude, the fuzzy control presented lower overshoot, that is favorable from the standpoint of mechanical. Therefore, the methodology proposed can be applied to HALT/HASS tests in order to obtain large vibrations and, consequently stress, to identify possible flaws in the design and correct them.
|
39 |
Interação entre os excitadores de vibração e a estrutura sob estudo em ensaios com múltipla excitação / Interaction between electrodynamic exciters and the structure under test in multiple input testsLeopoldo Pisanelli Rodrigues de Oliveira 30 April 2003 (has links)
Apresenta-se um estudo analítico e experimental do fenômeno de interação entre excitadores eletrodinâmicos e a estrutura em ensaios de vibração e discutem-se causas e efeitos desta interação na qualidade dos resultados obtidos. Inicialmente, realizam-se simulações numéricas que contemplam as características mecânicas e eletromagnéticas do excitador. Definido o modelo para o excitador, realizam-se simulações de teste com estruturas, dos quais obtêm-se as forças de entrada e funções de resposta em freqüência (FRFs) estimadas que serão comparadas às FRF reais da estrutura. Posteriormente, considera-se a inclusão de graus de liberdade rotacionais aos modelos do excitador e da estrutura. Finalmente, as simulações de testes com múltipla excitação têm como objetivo principal o de observar os fenômenos de queda de força de excitação e seus efeitos sobre as FRFs estimadas. Com os resultados experimentais verificam-se os principais fenômenos da interação excitador / estrutura observados nas simulações numéricas tais como a queda da força de excitação e a influência da dinâmica do conjunto excitador / amplificador na resposta da estrutura. Através dos resultados experimentais obtidos com uma viga metálica observam-se os principais efeitos previstos pelas simulações. Ainda, comparam-se as alterações nos dados obtidos com outros métodos de excitação tais como, martelo impulsivo e excitação em malha fechada. Testes realizados com diferentes estruturas, como um pneumático e um chassi tubular, vêem complementar os dados obtidos até então para excitação com um único excitador. Os testes realizados com a finalidade de validar os modelos que incluem graus de liberdade rotacionais mostram que tais grandezas não podem ser negligenciadas, principalmente no que se referem aos testes com excitação via base, em que o item de teste é montado diretamente sobre o excitador. Ainda, verificam-se os resultados obtidos com diversos estimadores de FRFs em ensaios com acréscimo de ruído aos sinais de entrada e saída. Os resultados experimentais realizados com dois excitadores mostram os mesmos efeitos observados nas simulações, em geral uma redução na queda da força de excitação e uma melhor distribuição de energia pela estrutura. / An analytical and experimental study of the interaction between electrodynamic exciters and the structure under test is presented, and the causes and effects of this interaction on the obtained data quality are discussed. Initially, some numerical simulations are performed concerning the shaker\'s mechanical and electrical features. Once the shaker model is defined, some tests with structures were simulated in order to obtain the input forces and the estimated frequency response functions to be compared with the measured FRFs. Afterwards, the rotational degrees of freedom were included in the shaker and structure models. Ending this section, tests with multiple input forces were simulated. The experimental results confirm most of the phenomena observed in the simulation section, such as the input force drop-off and the influence of the shaker / power amplifier assembly on the structure\'s response. The tests conducted with a steal beam confirmed the effects predicted by the simulations. Therefore, these results are compared with others, obtained from alternative methods such as impact test and closed loop shaker tests. Tests with structures like a truck tyre and a tubular chassis complement the assessment of single input tests. The tests performed with the objective of validating the models considering rotational degrees of freedom show that these quantities cannot be neglected, mainly when base driven tests are concerned. Also, the efficiency of FRF estimators applied to shaker tests, in the presence of noise on the input and output channels is verified experimentally. The multiple input tests corroborate the effects observed in the simulations, in general, a reduction of the droopoff on the force and an improvement on the input energy distribution on the structure.
|
40 |
Implementação de um sistema de controle heurístico de aceleração e tensão mecânica para ensaios em shaker eletrodinâmicoDonadel, Juliane January 2012 (has links)
Por décadas, a qualidade de produtos é determinada por testes em ambientes de laboratório, como testes de acelerados de vibração, ciclagem térmica, choque mecânicos ou térmicos, entre outros. Porém, mais recentemente um novo tipo de técnica tem adquirido a confiança de pesquisadores e projetistas. As técnicas conhecidas como HALT (Highly Accelerated Life Testing) e HASS (Highly Accelerated Stress Screening), ou seja, testes acelerados e amplificados que submetem produtos a condições severas, têm mostrado sua importância e eficiência no âmbito da detecção de falha em produtos ainda na fase de produção. Este trabalho tem por objetivo desenvolver e implementar um algoritmo de controle baseado em métodos heurísticos para ser usado em ensaios acelerados usando um Shaker eletrodinâmico. Este controlador deve ser robusto o suficiente para se adequar a possíveis efeitos de ressonância do shaker que podem vir a alterar a dinâmica do sistema, inviabilizando controles tradicionais com parâmetros fixos. Os resultados obtidos através de vários ensaios mostraram que ambos os sistemas de controle são eficientes, pois o erro entre o sinal desejado (tensão mecânica ou aceleração) e os medidos experimentalmente, tendem rapidamente a zero não apresentando sobressinais consideráveis ou erro em regime permanente, tanto para frequência fixa quanto para varredura de frequência. A comparação entre o controlador tradicional PID e o controle heurístico baseado em Lógica Fuzzy, que foram aplicados no shaker eletrodinâmico, comprova que, para mudanças na amplitude do sistema, o controle Fuzzy apresentou menor sobressinal, o que é mais favorável do ponto de vista mecânico. Logo, a metodologia proposta pode ser aplicada para ensaios HALT/HASS com o intuito de obter grandes vibrações e, por conseguinte tensões, para identificar possíveis falhas de projeto e então, poder corrigi-las. / For decades, product quality is determined by environmental tests, such as accelerated vibration tests, thermal cycling, mechanical or thermal shock, and others. However, more recently a new type of test has gained the trust of researchers and designers. Known techniques such as HALT (Highly Accelerated Life Testing) and HASS (Highly Accelerated Stress Screening), or accelerated and amplified testing that submit products to severe conditions have shown their importance in the efficiency and fault detection in products still in production phase. This study aims to develop and implement a control algorithm based on heuristic methods in order to be used in a system of accelerated tests in an electrodynamic shaker. This controller must be robust enough to fit the resonance effects of the shaker that it can change the system dynamic, invalidating traditional controls with fixed parameters. The results obtained through tests showed both control systems are efficient, because the error between desired signal (mechanical stress and acceleration) and the experimentally measured tend rapidly to zero, there aren’t overshoots or steady state errors, both for constant frequency and for sweep frequency. Comparing the PID traditional control and the Logic Fuzzy control, applied in electrodynamic shaker, we proved that to change system amplitude, the fuzzy control presented lower overshoot, that is favorable from the standpoint of mechanical. Therefore, the methodology proposed can be applied to HALT/HASS tests in order to obtain large vibrations and, consequently stress, to identify possible flaws in the design and correct them.
|
Page generated in 0.0346 seconds