Tesi sul tema "Structure vibration"
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1
Griffin, Steven F. "Acoustic replication in smart structure using active structural/acoustic control". Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/13085.
2
Kari, Leif. "Structure-borne sound properties of vibration isolators /". Stockholm, 1998. http://www.lib.kth.se/abs98/kari0312.pdf.
3
Sénéchal, Aurélien. "Réduction de vibrations de structure complexe par shunts piézoélectriques : application aux turbomachines". Phd thesis, Conservatoire national des arts et metiers - CNAM, 2011. http://tel.archives-ouvertes.fr/tel-00862517.
Abstract (sommario):
L'objet de cette thèse est d'étudier différents dispositifs d'amortissement de vibrations en basses fréquences des aubes de rotor de soufflante ("fan") d'un turboréacteur. Les solutions étudiées utilisent des pastilles piézoélectriques, liées à l'aube et connectées à un circuit électrique passif ou semi-passif. Dans la première partie, il s'agit de mettre en pratique le modèle électromécanique développé dans la thèse de Julien Ducarne, puis de l'étendre au cas tridimensionnel par l'utilisation de la méthode des éléments finis. Ce modèle de comportement prend en compte le couplage entre une structure mécanique quelconque et des pastilles piézoélectriques planes ou courbes. Par la suite, un modèle réduit à faible nombre de degrés de liberté est construit, ce qui permet après résolution de prédire l'efficacité des dispositifs amortissants. Deux techniques, nommées "shunt" et "switch" sont appliquées au cas d'une aube fan. La première consiste à utiliser un circuit électrique résistif ou résonant. La seconde, encore à l'état de recherche, comporte un circuit muni d'un interrupteur synchronisé aux oscillations de la structure, ce qui produit un amortissement analogue à celui d'un frottement sec. La modélisation et l'optimisation électrique de ces circuits, issus de différents travaux antérieurs, ne font l'objet que d'un rappel dans ce mémoire. Une procédure d'optimisation est développée pour pouvoir trouver les géométries et les emplacements des pastilles qui maximisent le couplage électromécanique. Deux algorithmes différents (recuit simulé et recherche avec liste taboue) sont utilisés et mis en interaction avec les outils de calcul éléments finis pour trouver des solutions optimisées. Afin de valider sur un cas industriel l'ensemble des travaux sur les dispositifs piézoélectriques, une campagne d'essai est menée sur une aube fan de CFM56-7b. Les niveaux d'atténuation mesurés et ceux prévus par le modèle sont ensuite comparés. La seconde partie est consacrée à l'évaluation de l'effet des nonlinéarités géométriques sur la dynamique d'une structure tournante. Initialement prévue pour être intégrée à la partie shunt piézoélectrique, ceci afin de pouvoir estimer l'efficacité de ce dernier lorsque la structure tourne et vibre en grande amplitude, l'étude n'a pas été poursuivie et constitue une partie sans lien avec les techniques de réduction de vibrations. Néanmoins, les résultats obtenus en 1D, ainsi que la méthode de prise en compte des nonlinéarités dans le cas 3D viennent compléter et enrichir les différentes études actuelles menées sur le sujet, raison pour laquelle ce chapitre a été ajouté à ce mémoire. La détermination des caractéristiques dynamiques modales et leurs évolutions en fonction de certains paramètres de fonctionnement de l'aube constituent l'objet de cette partie. Plusieurs modèles sont développés et comparés pour pouvoir juger de la présence et de l'importance des divers phénomènes non linéaires dans la réponse forcée d'une poutre en rotation.
4
Purohit, Ashish. "Aeroacoustics of a vibrating structure in flow". Thesis, IIT Delhi, 2016. http://localhost:8080/iit/handle/2074/7077.
5
Sun, Xiangkun. "Elastic wave propagation in periodic structures through numerical and analytical homogenization techniques". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC041/document.
Abstract (sommario):
Dans ce travail, la méthode homogénéisation de multi-échelle, ainsi que diverses méthodes non homogénéisation, seront présentés pour étudier le comportement dynamique des structures périodiques. La méthode de multi-échelle commence par la séparation d'échelles. Dans ce cas, une échelle microscopique pour décrire le comportement local et une échelle macroscopique pour décrire le comportement global sont introduites. D'après la théorie de l'homogénéisation, la longueur d'onde est supposée grande, et la longueur de la cellule doit être beaucoup plus petite que la longueur caractéristique de la structure. Ainsi, le domaine d'homogénéisation est limité à la première zone de propagation. Le modèle d'homogénéisation traditionnel utilise des valeurs moyennes des éléments, mais le domaine de validité pratique est beaucoup plus petit que la première bande interdite. Alors, le développement de nouveaux modèles homogénéisés est beaucoup motivé par cet inconvénient. Par rapport au modèle d'homogénéisation traditionnel, équations d'ordre supérieur sont proposées pour fournir des modèles homogénéisation plus précises. Deux méthodes multi-échelles sont introduites: la méthode de développement asymptotique, et la méthode de l'homogénéisation des milieux périodiques discrètes (HMPD). Ces méthodes seront appliquées de façon séquentielle dans le cas d'onde longitudinale et le cas d'onde transversale. Les mêmes modèles d'ordre supérieur sont obtenus par les deux méthodes dans les deux cas. Ensuite, les modèles proposés sont validés en examinant la relation de dispersion et de la fonction de réponse fréquentielle. Des solutions analytiques et la méthode des ondes éléments finis(WFEM) sont utilisés pour donner les références. Des études paramétriques sont effectuées dans le cas infini, et deux différentes conditions aux limites sont prises en compte dans le cas fini. Ensuite, le HMPD et CWFEM sont utilisés pour étudier les vibrations longitudinales et transversales des structures réticulées dans le cas 1D et 2D. Le domaine de validité du HPDM est réévalué à l'aide de la fonction de propagation identifiée par le CWFEM. L'erreur relative au nombre d'onde obtenue par HPDM est illustré sur la fonction de la fréquence et le rapport d'échelle. Des études paramétriques sur l'épaisseur de la structure sont réalisées par la relation de dispersion. La dynamique des structures finies sont également étudiés en utilisant la HPDM et CWFEMIn this work, the multi-scale homogenization method, as well as various non homogenization methods, will be presented to study the dynamic behaviour of periodic structures. The multi-scale method starts with the scale-separation, which indicates a micro-scale to describe the local behaviour and a macro-scale to describe the global behaviour. According to the homogenization theory, the long-wave assumption is used, and the unit cell length should be much smaller than the characteristic length of the structure. Thus, the valid frequency range of homogenization is limited to the first propagating zone. The traditional homogenization model makes use of material properties mean values, but the practical validity range is far less than the first Bragg band gap. This deficiency motivated the development of new enriched homogenized models. Compared to traditional homogenization model, higher order homogenized wave equations are proposed to provide more accuracy homogenized models. Two multi-scale methods are introduced: the asymptotic expansion method, and the homogenization of periodic discrete media method (HPDM). These methods will be applied sequentially in longitudinal wave cases in bi-periodic rods and flexural wave cases in bi-periodic beams. Same higher order models are obtained by the two methods in both cases. Then, the proposed models are validated by investigating the dispersion relation and the frequency response function. Analytical solutions and wave finite element method (WFEM) are used as references. Parametric studies are carried out in the infinite case while two different boundary conditions are considered in the finite case. Afterwards, the HPDM and the CWFEM are employed to study the longitudinal and transverse vibrations of framed structures in 1D case and 2D case. The valid frequency range of the HPDM is re-evaluated using the wave propagation feature identified by the CWFEM. The relative error of the wavenumber by HPDM compared to CWFEM is illustrated in the function of frequency and scale ratio. Parametric studies on the thickness of the structure is carried out through the dispersion relation. The dynamics of finite structures are also investigated using the HPDM and CWFEM
6
Dayou, Jedol. "Global control of flexural vibration of a one dimensional structure using tuneable vibration neutralisers". Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310842.
7
Baran, Ismet. "Optimization Of Vibration Characteristics Of A Radar Antenna Structure". Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612978/index.pdf.
Abstract (sommario):
Radar antenna structures especially array antennas which are integrated onto structures of aerial vehicles are subject to dynamic structural and aerodynamic loads. Due to occurrences of these dynamic loads there will be certain dynamic deformations which affect the antenna&rsquos performance in an adverse manner. The influence of deformations and vibrations are important on array antenna structures, since they cause a change in orientation of elements of the phased array antenna which affects the gain of the antenna negatively. In this study, vibration characteristics of a particular radar antenna structure are optimized using topology and stiffener design optimization methods such that negative effects of mechanical vibrations on functional performance of radar antenna are minimized. Topology and stiffener design optimization techniques are performed separately by the use of ANSYS Finite Element (FE) software in order to modify the design of the radar antenna structure such that its critical natural frequencies in the range of 0-500 Hz are shifted out of the dominant peak sinusoid frequency range of the air platform. As a result of this, it will be possible to minimize the vibration response of the phased array elements in the frequency range of 0-500 Hz
hence better antenna performance can be achieved. In addition to this, it will also be possible to minimize the broadband random vibration response of base excitation coming from air platform.
8
Tratch, Jorge. "Vibration transmission through machinery foundation and ship bottom structure". Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15216.
Abstract (sommario):
Thesis (Mech.E)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.
Includes bibliographical references.
by Jorge Tratch Junior.
Mech.E
9
Thomas, Benjamin. "Dynamique d’une structure complexe à non linéarités localisées sous environnement vibratoire évolutif : Application à l'isolation vibratoire d'un équipement automobile". Thesis, Lyon, INSA, 2012. http://www.theses.fr/2012ISAL0106/document.
Abstract (sommario):
Cette recherche porte sur le développement d’un modèle de structure de géométrie complexe équipée de composants à comportement non linéaire viscoélastique dans le but de simuler sa réponse à des excitations définies par des densités spectrales de puissance (DSP). L’application industrielle concerne l’isolation vibratoire d’un module de refroidissement automobile monté sur plot de suspension en élastomère. Une revue du comportement des élastomères en fonction de leurs conditions d’environnement et de sollicitations identifie les paramètres des différents modèles analysés. Des essais préliminaires ont été menés pour définir les intervalles des niveaux de sollicitations et quantifier l’échauffement des plots. La caractérisation expérimentale de la suspension porte sur des plots en élastomère munis de leurs interfaces afin d’agréger dans un seul modèle les non linéarités du comportement viscoélastique, des glissements et des frottements. Les boucles effort-déflexion axiales et radiales mesurées sont traitées avec un système expert développé spécialement pour caler les paramètres du modèle retenu. Il s’agit du modèle de Dahl généralisé qu’il a fallu étendre aux aspects viscoélastiques. Ce processus de calage automatique a été codé avec un logiciel développé sous Octave/Matlab. Des méthodes d’interpolations et extrapolations rendent opérationnel ce modèle sur toute la gamme fonctionnement de l’application définie dans l’espace fréquence-déflexion. Ce processus a été codé dans le module UserSubroutine pour Abaqus. Soumettre le système mécanique non linéaire à des excitations définies par une DSP nécessite de s’appesantir sur le traitement des vibrations aléatoires. En effet il faut, pour calculer les réponses, considérer le passage fréquence-temps et inversement pour les comparer éventuellement aux exigences des normes. De plus, la taille et la complexité du modèle EF de la structure industrielle rendent impossible une résolution temporelle sur l’ensemble de ses degrés de liberté. Il s’agit alors de faire appel à des techniques d’homogénéisation et de condensation dynamique afin de prévoir la réponse aux excitations à large bande fréquentielle dans le but d’analyser les performances de l’isolation vibratoireThis research work regards the development of a complex structure model with non-linear viscoelastic components. The purpose of this study is to simulate the response of this structure submitted to a random vibration excitation based on a power spectral density definition (PSD). The industrial applicative case is the vibratory insulation of a automotive engine cooling module supported by elastomer mounts. A brief review of elastomers behavior depending on solicitations types enables to identify the parameters of the different investigated models. Preliminary tests have been conducted to define the range of amplitudes of excitations and evaluate the internal warming of rubbers during the full structure validation test. The experimental characterization of the suspension is based on rubbers mounts and their interfaces with the cooling module, in order to take into account in a unique model all nonlinearities due to the viscoelastic behavior, the slidings, and the friction. Measured force-deflection hysteretic cycles in axial and radial direction are post-processed with an expert system developed to obtain the parameters of the retained model: the modified Dahl’s model, generalized to viscoleastic aspect. This process has been developed with Octave/Matlab code. Interpolation and extrapolation methods enable to obtain a good model response on the global operating range. These methods have been coded in an Abaqus UserSubroutine. Imposing random vibration excitation of a non linear mechanical system based on PSD imposes to take into account signal processing aspects. To evaluate response levels versus norms requirements, it’s mandatory to consider the time-frequency transfer. In addition, the size and the complexity of the total finite element model of the industrial structure don’t allow a global resolution in the time domain for all the degrees of freedom. Homogenization and dynamic reduction techniques are used to evaluate the response of the system submitted to large frequency range excitations, and to analyse the behavior of the suspension
10
Thomas, Benjamin. "Dynamique d’une structure complexe à non linéarités localisées sous environnement vibratoire évolutif : Application à l'isolation vibratoire d'un équipement automobile". Electronic Thesis or Diss., Lyon, INSA, 2012. http://www.theses.fr/2012ISAL0106.
Abstract (sommario):
Cette recherche porte sur le développement d’un modèle de structure de géométrie complexe équipée de composants à comportement non linéaire viscoélastique dans le but de simuler sa réponse à des excitations définies par des densités spectrales de puissance (DSP). L’application industrielle concerne l’isolation vibratoire d’un module de refroidissement automobile monté sur plot de suspension en élastomère. Une revue du comportement des élastomères en fonction de leurs conditions d’environnement et de sollicitations identifie les paramètres des différents modèles analysés. Des essais préliminaires ont été menés pour définir les intervalles des niveaux de sollicitations et quantifier l’échauffement des plots. La caractérisation expérimentale de la suspension porte sur des plots en élastomère munis de leurs interfaces afin d’agréger dans un seul modèle les non linéarités du comportement viscoélastique, des glissements et des frottements. Les boucles effort-déflexion axiales et radiales mesurées sont traitées avec un système expert développé spécialement pour caler les paramètres du modèle retenu. Il s’agit du modèle de Dahl généralisé qu’il a fallu étendre aux aspects viscoélastiques. Ce processus de calage automatique a été codé avec un logiciel développé sous Octave/Matlab. Des méthodes d’interpolations et extrapolations rendent opérationnel ce modèle sur toute la gamme fonctionnement de l’application définie dans l’espace fréquence-déflexion. Ce processus a été codé dans le module UserSubroutine pour Abaqus. Soumettre le système mécanique non linéaire à des excitations définies par une DSP nécessite de s’appesantir sur le traitement des vibrations aléatoires. En effet il faut, pour calculer les réponses, considérer le passage fréquence-temps et inversement pour les comparer éventuellement aux exigences des normes. De plus, la taille et la complexité du modèle EF de la structure industrielle rendent impossible une résolution temporelle sur l’ensemble de ses degrés de liberté. Il s’agit alors de faire appel à des techniques d’homogénéisation et de condensation dynamique afin de prévoir la réponse aux excitations à large bande fréquentielle dans le but d’analyser les performances de l’isolation vibratoireThis research work regards the development of a complex structure model with non-linear viscoelastic components. The purpose of this study is to simulate the response of this structure submitted to a random vibration excitation based on a power spectral density definition (PSD). The industrial applicative case is the vibratory insulation of a automotive engine cooling module supported by elastomer mounts. A brief review of elastomers behavior depending on solicitations types enables to identify the parameters of the different investigated models. Preliminary tests have been conducted to define the range of amplitudes of excitations and evaluate the internal warming of rubbers during the full structure validation test. The experimental characterization of the suspension is based on rubbers mounts and their interfaces with the cooling module, in order to take into account in a unique model all nonlinearities due to the viscoelastic behavior, the slidings, and the friction. Measured force-deflection hysteretic cycles in axial and radial direction are post-processed with an expert system developed to obtain the parameters of the retained model: the modified Dahl’s model, generalized to viscoleastic aspect. This process has been developed with Octave/Matlab code. Interpolation and extrapolation methods enable to obtain a good model response on the global operating range. These methods have been coded in an Abaqus UserSubroutine. Imposing random vibration excitation of a non linear mechanical system based on PSD imposes to take into account signal processing aspects. To evaluate response levels versus norms requirements, it’s mandatory to consider the time-frequency transfer. In addition, the size and the complexity of the total finite element model of the industrial structure don’t allow a global resolution in the time domain for all the degrees of freedom. Homogenization and dynamic reduction techniques are used to evaluate the response of the system submitted to large frequency range excitations, and to analyse the behavior of the suspension
11
Dhruna, Chetan J. "Experimentally-Based Analytical Prediction of Structural Vibration". Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/35875.
Abstract (sommario):
This study evaluates the vibration isolation effect of various mounting systems in a heavy freight locomotive cab, and provides an analytical method for the prediction of structural vibration. The cab is set up in a controlled laboratory environment in a manner similar to the installation on a locomotive. Field measurements are used to emulate actual vibration input to the cab structure. A 16-channel data acquisition system is used to collect vibration data at various points on and inside the cab structure.
The cab was isolated from the sill structure through six elastomeric mounts fixed at the base of the cab and at the crash posts. The mounts at the base were selected such that they support the static weight of the cab and offer good lateral and longitudinal stability. Two cylindrical elastomeric mounts were placed between the cab structure and the crash posts which attach to the front of the sill structure.
Upon establishing the baseline for laboratory vibration measurements and correlating them with field data, acceleration data was collected at discrete locations, both inside and outside of the cab. The data was used in conjunction with an analytical formulation to generate vibration approximations of the discrete locations. To validate the analytical approximations, experimental results were compared with the analytical predictions using simulated field input to the cab
The test results from the analytical model approximations proved to have a strong correlation with experimental results. Vibration approximations of locations outside the cab had a higher correlation to the experimental data than the points on the inside. Although the model did not yield exact results for several positions inside the cab, it resulted in several recommendations for future work.Master of Science
12
Ng, S. L. D. "Transmission of ground-borne vibration from surface railway trains". Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243156.
13
Badiane, Doudou. "Simulation numérique et étude expérimentale d'un viscosimètre à principe vibrant". Thesis, Orléans, 2012. http://www.theses.fr/2012ORLE2057/document.
Abstract (sommario):
La connaissance de la viscosité est un défi majeur dans les technologies de pointe (biomédical, pétrochimie, imprimerie, cosmétique, agroalimentaire, etc). Cette étude présente un capteur de viscosité qui exploite la vibration transversale forcée d’une poutre mince. L’amortissement induit par le fluide permet d’évaluer sa viscosité et sa masse volumique par la seule connaissance des caractéristiques à la résonance de la poutre (amplitude et fréquence). Cette mesure est réalisée par un circuit électromagnétique. Dans ce travail, la simulation numérique et l’étude expérimentale du viscosimètre sont réalisées en vue de mieux cerner les paramètres influençant le fonctionnement du capteur. Les différentes investigations menées dans ce travail sont d’une grande importance pour l’optimisation du viscosimètre d’une part. D’autre part, c’est une contribution à l’ensemble des études qui traitent de l’aspect du couplage fluide-structure-électromagnétismeKnowing the viscosity becomes increasingly a major challenge in leading-edge technologies (biomedical, petrochemical, printing, cosmetic, food industry, etc). This study presents a viscosity sensor based on a thin beam immersed in a newtonian fluid and subjected to transverse vibrations due to an electromechanical excitation system. The damped vibration can be used to evaluate the fluid viscosity and density by measuring the beam’s resonance characteristics (amplitude, frequency). This measurement is done by an electromagnetic feedback circuit. In this work, numerical model and experimental studies of the vibrating viscometer are conducted to better understand the influencing factors of the sensor’s operation. The different investigations carried out in this work are of great importance for the viscometer optimization on one hand. On the other hand, it’s a contribution to all studies dealing with the aspect of fluid-structure-electromagnetism coupling
14
Asyikin, Muhammad Tedy. "CFD Simulation of Vortex Induced Vibration of a Cylindrical Structure". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bygg, anlegg og transport, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18814.
Abstract (sommario):
This thesis presents the investigation of the flow characteristic and vortex induced vibration (VIV) of a cylindrical structure due to the incompressible laminar and turbulent flow at Reynolds number 40, 100, 200 and 1000. The simulations were performed by solving the steady and transient (unsteady) 2D Navier-Stokes equation. For Reynolds number 40, the simulations were set as a steady and laminar flow and the SIMPLE and QUICK were used as the pressure-velocity coupling scheme and momentum spatial discretization respectively. Moreover, the transient turbulent flow was set for Re 100, 200 and 1000 and SIMPLE and LES (large Eddies Simulation) were selected as the pressure-velocity coupling solution and the turbulent model respectively. The drag and lift coefficient (Cd and Cl) were obtained and verified to the previous studies and showed a good agreement. Whilst the vibration frequency (fvib), the vortex shedding frequency (fv), the Strouhal number (St) and the amplitude of the vibration (A) were also measured.
15
SANTEE, DONALD MARK. "NONLINEAR VIBRATION AND STRUCTURE STABILITY ANALYSIS OF IMPERFECTION SENSITIVE ELEMENTS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1999. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=1897@1.
Abstract (sommario):
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORO objetivo desta tese é estudar os mecanismos de escape em sistemas estruturais sensíveis a imperfeições quando submetidos a certas classes de carregamentos dinâmicos, identificar os parâmetros que controlam o escape e criar critérios capazes de prever a fronteira de escape e a perda de estabilidade da estrutura no espaço dos parâmetros de controle. Isto permitirá um melhor entendimento dos processos de perda de estabilidade e servirá de base para o cálculo e controle da integridade dessas estruturas. Após a descrição dos fenômenos que podem ocorrer na dinâmica dessa classe de estruturas, são testados e adaptados alguns critérios existentes na literatura, que verificam a estabilidade de uma estrutura a partir do conhecimento dos parâmetros de controle. Em seguida estuda-se a evolução da estabilidade global do conjunto das soluções medida pela área da bacia de atração, e pelas características de sua fronteira. Desenvolvem-se expressões gerais para o critério de Melnikov, e mostra-se, a partir de perturbações aleatórias nos parâmetros de controle e na força externa, que essas expressões podem ser tomadas como um limite inferior para o carregamento de escape e conseqüentemente como uma contribuição para o desenvolvimento de critérios de projeto. Verifica-se também que os valores obtidos pelos critérios de escape podem ser tomados como limites superiores para o valor da força de escape.
The purpose of this thesis is to study the escape mechanisms in imperfection sensitive structural systems under certain dynamical loading conditions. Other objectives are to identify the parameters that control the escape phenomenon and to create some criteria capable of predicting the escape boundary and the structures stability in the control parameters space. This will allow a better understanding of the stability loss process and can serve as a basis to the integrity control and design of these structures. After a description of the phenomena that can occur in the dynamics of this class of structures, some predictive criteria, found in literature, that verify the structure stability based on the control parameters knowledge, are adapted and tested. Following is a study of the evolution of the global stability of the set of solutions measured by the basin of attraction area, and by the characteristics of its boundary. Some general expressions for the Melnikov criterion are developed, and it is shown by randomly perturbing the control parameters and the external force, that these expressions can be taken as a lower bound for the escape load, and consequently as a contribution to the development of design criteria. It is also observed that the values obtained by the escape criteria can be taken as an upper bound for the values of the escape force.
EL objetivo de esta tesis es estudiar los mecanismos de escape en sistemas extructurales que son sensibles a imperfecciones cuando son sometidos a ciertas clases de cargas dinámicas. Outro objetivo es identificar los parámetros que controlan el escape y crear criterios capaces de preveer la frontera de escape y la pérdida de estabilidad de la extructura en el espacio de los parámetros de control. Esto permitirá una mejor comprensión de los procesos de pérdida de estabilidad y servirá de base para el cálculo y control de la integridad de esas extructuras. Después de describir los fenómenos que pueden ocurrir en la dinámica de esta clase de extructuras, se prueban y adaptan algunos criterios existentes en la literatura, que verifican la estabilidad de una extructura a partir del conocimiento de los parámetros de control. Seguidamente, se estudia la evolución de la estabilidad global del conjunto de las soluciones, se dearrollan expresiones generales para el criterio de Melnikov, y se muestra, a partir de perturbaciones aleatorias en los parámetros de control y en la fuerza externa, que esas expresiones pueden ser tomadas como límite inferior para la carga de escape y conseqüentemente como una contribución para el desarrollo de criterios de proyecto. Se verifica también que los valores obtenidos por los criterios de escape pueden ser tomados como límites superiores para el valor de la fuerza de escape.
16
Wang, Wei-Hui. "Modelling machine induced noise and vibration in a ship structure". Thesis, University of Plymouth, 2000. http://hdl.handle.net/10026.1/2823.
Abstract (sommario):
Most high speed vessels are fitted with powerful high speed engines which are installed in confined spacesa nd, as a consequencec, ausea n extremely high level of noise and vibration. Often structure-borne sound power is transmitted to a sound carrying structure from a source via a number of contact points. In turn, the noise and vibration are propagated in the structure and could possibly cause an undesired noise radiation. In this study, a model for predicting power flow based on the mobility theory has been addressed. The unique parts of the study include the establishment of the relationship of mobility functions with respect to four-pole parameters and the dynamic stiffness coefficients of a coupled machine/mount/foundation system. Also expressions to represent the sound input power, the output power and the transmitted power in relation to mobility functions are clarified. From a detailed analysis of relevant literature, it is shown that no validated models for predicting the propagation of structure-bome noise within the intermediate frequency range of 125 Hz to lkHz exist. As a consequence, a new numerical stress wave model has been developed to bridge this knowledge gap. This innovative approach extends the earlier works of Cremer, Heckl and Ungar in the field of stress wave propagation. Finally, a novel holistic model has been developed to line up the transmission, propagation and radiation predictions of a machine induced noise and vibration in ship's structure to take in account the fluid-structure interaction effect. A number of experiment measurements have been performed to validate the established models. From the comparisons, the prediction models are shown to be credible with an accuracy higher than 95 per cent. The established models are of a generic nature and can be applicable to diverse engineering fields regarding to the predictions of structure-borne noise and vibration transmission, propagation and radiation. Applications of these models to characterize the vibration reduction countermeasures,a s in the case of resilient mounts and squeeze-film damping plates, from a machine are also discussed.
17
Kim, Seungbo. "Structure-borne noise transmission through a multi-dimensional vibration isolator /". The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486399451959589.
18
Martins, Daniel. "Vibration control on a tensegrity structure using shape memory alloys /". Bauru, 2019. http://hdl.handle.net/11449/183354.
Abstract (sommario):
Orientador: Paulo José Paupitz GonçalvesBanca: Marcos Silveira
Banca: Carlos de Marqui Junior
Resumo: Um sistema de tensegrity é composto por dois tipos de elementos, elementos de tração e compressão, os quais promovem a estabilidade estrutural do sistema, neste trabalho as partes de tração são cabos (cabos de aço), e as partes compressivas são barras de aço. Uma característica atrativa de uma estrutura de tensegridade é a capacidade de ser retrátil, por esta razão, é interessante para aplicações espaciais devido ao pequeno volume que ocupa um possível transporte para uma estação espacial. Em geral, essas estruturas podem ser grandes com muitas células repetitivas. Neste trabalho, estuda-se uma estrutura de tensegrity composta por dez células periódicas de barras e cabos. O modelo matemático, obtido pelo método dos elementos finitos, é validado experimentalmente considerando o caso de uma célula estrutural. Para tornar o sistema adaptável à excitação externa, um dos cabos de aço na célula elementar é substituído por um fio de liga de memória de forma (SMA) que permite que as características dinâmicas do sistema sejam alteradas de acordo com uma corrente elétrica aplicada no SMA, para que através do efeito Joule a liga seja aquecida. Diferentes configurações para a colocação do cabo SMA são estudadas com o objetivo de reduzir as amplitudes de vibração para uma excitação de força harmônica.
Abstract: A tensegrity system is composed by two types of elements, tensile and compressive parts, which promotes the structural stability of the system, in this case the tensile parts are cables (steel cables), and the compressive parts are bars, in this work made of steel. An attractive characteristic of a tensegrity structure is the capability to be deployable, for this reason, is interesting for space applications due to the small volume that it occupies in a possible transport to a station outside the Earth. In general, these structures can be large with many repetitive cells. In this work, a tensegrity boom structure consisting of ten periodic cells made of bars and cables is studied. The mathematical model, obtained by finite element method is validated experimentally considering the case of one structural cell. In order to make the system adaptable to external excitation, one of the steel cables in the elementary cell is replaced by a SMA (shape memory alloy) wire (Nitinol) allowing the dynamics characteristics of the system to be changed according to an electrical current applied to the SMA, to heat the alloy through Joule effect. Different configurations for placing the SMA cable are studied with the objective of reducing the vibration amplitudes for harmonic force excitation.
Mestre
19
Fraser, Grant. "Structure borne sound in motor-vehicles using statistical energy analysis". Thesis, Heriot-Watt University, 1998. http://hdl.handle.net/10399/1285.
Abstract (sommario):
This Thesis is about the application of Statistical Energy Analysis (SEA) to the study of noise and vibration in motor vehicles. Methods for predicting the transmission of structural waves between body panels in motor cars are given. A complex joint technique based on the wave dynamic stiffness approach is discussed in detail. This technique can account for the complexities of the joint structures found in motor vehicles. Transmission of vibration energy between panels connected by a curved section of panel has been investigated using the complex joint modelling technique. Wave Intensity Analysis(WIA) and SEA were used to calculate the coupled panel vibration levels based on transmission coefficients calculated using the complex joint techniques. Energy Level Differences (ELDs) were measured for comparison with predicted results using laboratory models. SEA failed to accurately predict the ELDs except at low frequencies. However WIA was able to predicted the ELDs with reasonable accuracy using an existing expression for transmission at a panel corner joint. Two SEA models of a small passenger car have also been constructed. One assumes simpler joint configurations when calculating transmission coefficients and the other uses the complex joint technique. Panel ELDs were measured using a small passenger car. The SEA model using the complex joint method gives better agreement with measured ELDs than did the model using the simpler joints. saloon Sound Pressure Level (SPL) as a result of engine noise was measured. Both SEA models of the vehicle gave good agreement between measured and predicted Saloon SPL. A noise problem associated with exhaust misalignment is also investigated.
20
Côté, François. "Développement par éléments finis de la région active d'une structure intelligente multi-couches". Sherbrooke : Université de Sherbrooke, 2002.
21
Zhang, Qingwen. "Models of a standing human body in structural vibration". Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/models-of-a-standing-human-body-in-structural-vibration(00dfea7a-dbff-4396-b816-8e81a1891fa8).html.
Abstract (sommario):
It has been widely accepted that a stationary human body, such as a person when sitting or standing, acts as a single degree of freedom (SDOF) system in structural vibration. However, it is not clear what form the SDOF model should take and what are the appropriate parameters for the model. The significance of considering human body models in structural vibration comes from the fact that human involvement affects the dynamic behaviour of the structure when a crowd is present and that human body response is different from structural vibration. This forms the basis of this study.This thesis presents both experimental and theoretical studies to develop human body models. It examines the characteristics of two interaction human body models, determines the parameters of the two body models in structural vibration and explores their applications.A continuous model of a standing human body in vertical vibrations is first developed using an anthropomorphic model and two available natural frequencies obtained from shaking table tests. A standing human body is represented as a bar with seven mass segments using the anthropomorphic model and two stiffnesses of the model are identified using the two natural frequencies. The relationships between the continuous model and discrete body models are provided.The masses, damping ratios and stiffnesses of two interaction body models are identified by curve fitting of the measured apparent mass curves from shaking table tests in published biomechanics studies. In this identification process it was identified that one or two conditions have to be applied which can be derived from the outcome of the continuous body model.The characteristics of human-structure interaction models are investigated using both theoretical and experimental Fourier Response Functions. The comparative studies based on 10 tests help to show that the interaction body model is more appropriate than the conventional body model used in structural vibration, and identify the appropriate parameters for the interaction model. The theoretical study shows that the response of stationary people is always larger than structural vibration when human loads are applied, such as walking, jumping and bouncing. The conditions for observing two resonance frequencies are provided graphically for a human-structure system where the interaction body model is used.A method is proposed to identify the parameters of the interaction model through 45 free vibration tests of a standing person on a test rig. The identified values of the natural frequency and damping ratio of a standing body are not close to those from the biomechanics tests. Sensitivity studies show that the two parameters are sensitive to the input data, the damped natural frequency and damping ratio of the human-structure system, which are obtained from free vibration tests.As an extension of the application of FRF and the human-structure model, the optimum parameters of a tuned-mass-damper are obtained based on the concept of equivalent damping ratio of a SDOF structure system. The results are tabulated for practical use. An example of floor vibration induced by rhythmic crowd loads is provided to demonstrate the use of the optimum TMDs and shows the effect of vibration reduction.This thesis entitled “Models of a Standing Human Body in Structural Vibration” is submitted to the University of Manchester by Qingwen Zhang for the degree of Doctor of Philosophy in 2013.
22
MURUGAN, JAYA MAHESH. "Vibration monitoring and control of industrial structures". Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2858351.
23
Hui, Yi. "Development and experimental validation of vibration based damage indicator on a specific twin-wall sandwich structure". Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEC032.
Abstract (sommario):
La surveillance de santé structurale (SHM) a attiré beaucoup d'attention dans de nombreux domaines tels que l'industrie civile, aéronautique, mécanique, etc., car il est important de surveiller l'état de la structure afin d'éviter des défaillances structurelles imprévues. Le processus d'identification des endommagements à quatre niveaux: existence, localisation, sévérité et prédiction de l'évolution des endommagements peut être partiellement réalisé si un propre indicateur est bien choisi. Il existe différents indicateurs d'endommagements dont la gamme d'application de la fréquence s'étend de la réponse vibratoire à basses fréquences aux régimes ultrasoniques dans la gamme méga hertz.Les structures sandwich sont largement utilisées dans diverses applications d'ingénierie en raison de son rapport rigidité / poids exceptionnellement élevé par rapport aux structures monocoques. Dans ce travail, une structure sandwich a été étudiée et des indicateurs basés sur la réponse vibratoire ont été conçus en utilisant ses caractéristiques de directivité de propagation et d'amortissement relativement élevé de la structure. Des investigations numériques sur différents scénarios d'endommagement (càd, différents types d'endommagement et leurs combinaisons) et une discussion associée sur la plage d'application ont d'abord été effectuées. La configuration expérimentale a été facilement réalisée à l'aide d'un vibromètre laser à balayage Doppler (SLDV). L'endommagement a été détecté avec succès par les indicateurs proposésStructural health monitoring (SHM) has attracted much attention in many engineering fields like civil, aeronautic, mechanical industry, etc. since it is important to monitor the healthy condition of the operational structure in order to avoid unpredicted structural failure which may have severe consequences. The four-level damage identification process: existence, localization, severity and prediction of damage evolution, can be partly realized if a suitable indicator is chosen. It exists different damage indicators whose application range of frequency spans from vibrational response at low frequencies to the ultrasonic regimes in the mega hertz range.The sandwich structures are widely used in various engineering applications due to its exceptionally high flexural stiffness-to-weight ratio compared to monocoque structures. In this thesis a specified twin-wall sandwich structure in polypropylene was studied and vibration-based indicators were designed by taking use of its relative high damping and propagation directivity characteristics. Numerical investigations on different damage scenarios (i.e., different types of defect and their combinations) and an associated discussion on the range of application were first carried out. Experimental configuration was easily realized with the help of a scanning laser doppler vibrometer (SLDV). Defect was successfully detected by the proposed indicators
24
Ozsoy, Serhan. "Vibration Induced Stress And Accelerated Life Analyses Of An Aerospace Structure". Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12606966/index.pdf.
Abstract (sommario):
Fatigue failure of metallic structures operating under dynamic loading is a
common occurrence in engineering applications. It is difficult to estimate the
response of complicated systems analytically, due to structure’
s dynamic characteristics and varying loadings. Therefore, experimental, numerical or a combination of both methods are used for fatigue evaluations. Fatigue failure can occur on systems and platforms as well as components to be mounted on the platform. In this thesis, a helicopter&
#8217
s Missile Warning Sensor - Cowling assembly is analyzed. Analytical, numerical and experimental approaches are used wherever necessary to perform stress and fatigue analyses. Operational flight tests are used for obtaining the loading history at the analyzed location by using sensors. Operational vibration profiles are created by synthesizing the data (LMS Mission Synthesis). Numerical fatigue analysis of the assembly is done for determining the natural modes and the critical locations on the assembly by using a finite element model (MSC Fatigue). In addition, numerical multiaxial PSD analysis is performed for relating the experimental results (Ansys). Residual stresses due to riveting are determined (MSC Marc) and included in experimental analysis as mean stresses. Bolt analysis is performed analytically (Hexagon) for keeping the v assembly stresses in safe levels while mounting the experimental prototype to the test fixture. Fatigue tests for determining the accelerated life parameters are done by an electromagnetic shaker and stress data is collected. Afterwards, fatigue test is performed for determining whether the assembly satisfies the required operational life. Resonance test is performed at the frequency in which the critical location is at resonance, since there was no failure observed after fatigue testing. A failure is obtained during resonance test. At the end of the study, an analytical equation is brought up which relates accelerated life test durations with equivalent alternating stresses. Therefore, optimization of the accelerated life test duration can be done, especially in military applications, by avoiding the maximum stress level to reach or exceed the yield limit.
25
Iu, Vai-pan, e 姚偉彬. "Nonlinear vibration analysis of multilayer sandwich structure by incremental finite elements". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1985. http://hub.hku.hk/bib/B31230623.
26
Priest, Eric M. "Free Vibration Response Comparison of Composite Beams with Fluid Structure Interaction". Thesis, Monterey, California. Naval Postgraduate School, 2012. http://hdl.handle.net/10945/17443.
Abstract (sommario):
Approved for public release; distribution is unlimitedThe analysis of the dynamic response of a vibrating structure in contact with a fluid medium can be interpreted as an added mass effect known as the Fluid Structure Interaction (FSI) problem. This effect is critical in the study of composites for marine applications since the densities of the composites and water are relatively close to one another. In this study, experimental testing was conducted to compare the free vibration response of composite beams in air with those in FSI immersed in water. Composite beams with six layers of non-biased, plain weave, 6 oz E-glass were used with two different layer orientations and boundary conditions. Five samples were layered at the 0 and 90 degree orientations and five samples were layered at the plus and minus 45 degree orientation. The Digital Image Correlation (DIC) technique was used to test each of the ten samples in a cantilever boundary condition with an initial displacement to induce a free vibration response both in air and immerse in water. A High Speed Camera (HSC) was also used to gain further frequency information during each of these tests. A second set of two composite beams were constructed with 16 layers at both of the described orientations. These were instrumented with accelerometers to conduct a modal analysis from an impact hammer test. These tests were conducted with the beams in a free-free boundary condition while in air and immersed in water. Prior to conducting these tests, an aluminum beam was tested with the same conditions to verify the waterproofing of the accelerometers and to ensure valid data was collected. The findings of this study will provide a better understanding for the use of composite materials in marine applications where various excitations can occur.
27
Brandsen, Jacobus Daniel. "Prediction of axial compressor blade vibration by modelling fluid-structure interaction". Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/85616.
Abstract (sommario):
Thesis (MScEng)-- Stellenbosch University, 2013.ENGLISH ABSTRACT: The Council for Scientific and Industrial Research has developed a vibration excitation system. The system is designed to excite the rotor blades of an axial compressor in the specified vibration mode and at the specified frequency. The vibration excitation system was tested on Stellenbosch University’s Rofanco compressor test bench. A two-way staggered fluid-structure interaction (FSI) model was created that was capable of simulating the vibration of the rotor blades excited by the system. The results of the FSI model were verified using available experimental data. It was concluded that the FSI model is able to recreate the vibration excited by the system to within the desired level of accuracy. In addition, the results of the FSI model showed that the vibration excitation system should be able to excite the blades in the selected vibration mode and at the selected frequency provided that the excitation frequency is close the natural frequency of the first bending mode. The results also suggested that a transient computational fluid dynamics model should be sufficient for the prediction of the aerodynamic forces acting on the rotor blades. Furthermore, a one-way staggered FSI model should be adequate for calculating the motions of the blades.
AFRIKAANSE OPSOMMING: Die Wetenskaplike en Nywerheidnavorsingsraad het ’n vibrasie-opwekkingstelsel ontwerp om die rotorlemme van ’n aksiaalvloei kompressor in die gespesifiseerde vibrasiemodus en teen die gespesifiseerde frekwensie op te wek. Die vibrasieopwekkingstelsel is met behulp van die Universiteit Stellenbosch se Rofanco kompressortoetsbank getoets. Daarna is ’n tweerigting vloeistof-struktuur-interaksie model geskep om die vibrasie van die rotorlemme, wat deur die stelsel opgewek is, te simuleer. Beskikbare eksperimentele data is gebruik om die resultate van die vloeistof-struktuur-interaksie model te bevestig. Die gevolgtrekking is gemaak dat die model wél die vibrasie van die lemme met die nodige akkuraatheid kan simuleer. Die resultate van die vloeistof-struktuur-interaksie model toon ook dat die stelsel die lemme in die gekose vibrasiemodus en teen die gekose frekwensie behoort te kan opwek, solank die opwekkingsfrekwensie na aan die natuurlike frekwensie van die eerste buigmodus is. Voorts dui die resultate daarop dat ’n berekeningsvloeimeganika model die aërodinamiese laste van die lemme sal kan voorspel. ’n Eenrigting vloeistof-struktuur-interaksie model behoort voldoende te wees om die beweging van die rotorlemme te bereken.
28
Chaudhari, Devendra. "Experiments on the vibration control of a flexible structure using FPGA". Thesis, California State University, Long Beach, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10014956.
Abstract (sommario):
The goal of this project is to develop, implement and test experimentally a state-feedback controller for the vibration control of a flexible structure, using an Active Mass Damper (AMD). Based on a previously developed model of the structure, a state-feedback controller with full observer has been implemented in the LabView (Laboratory Virtual Instrument Engineering Workshop) computational environment using the myRIO FPGA board (Field Programmable Gate Array). Experimental results show that the controller improves the structural response significantly by reducing the amplitude and duration of the response when the structure is subject to random earthquake-like excitations.
29
Iu, Vai-pan. "Nonlinear vibration analysis of multilayer sandwich structure by incremental finite elements /". [Hong Kong : University of Hong Kong], 1985. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12322945.
30
Robu, Bogdan. "Active vibration control of a fluid/plate system". Phd thesis, Toulouse 3, 2010. http://thesesups.ups-tlse.fr/1103/.
Abstract (sommario):
Cette thèse s’intéresse au problème du contrôle actif des vibrations structurelles d’une aile d’avion induites par le ballottement du carburant dans les réservoirs qu’elle contient. L'étude proposée ici est concentrée sur l'analyse d'un dispositif expérimental composé d'une longue plaque rectangulaire en aluminium équipée d'actionneurs et de capteurs piézoélectriques et d'un réservoir cylindrique. La difficulté principale réside dans le couplage complexe entre les modes de vibration de l’aile et les modes de ballottement du liquide. Un modèle de ce dispositif à l’aide d’équations aux dérivées partielles est tout d’abord construit. Ce modèle de dimension infinie couple une équation des plaques avec l'équation de Bernoulli pour le mouvement du fluide dans le réservoir. En analysant la contribution énergétique des modes, une approximation en dimension finie, de type espace d'état est alors construite. Après une méthode de recalage fréquentiel du modèle, un contrôle est réalisé en utilisant dans un premier temps une méthode par placement de pôle et dans un deuxième temps, la théorie de la commande robuste H-infini. La dimension du modèle et les performances demandées imposent le calcul d’un contrôleur H-infini d'ordre réduit, conçu en utilisant la librairie HIFOO 2. 0 et testé sur le dispositif expérimental pour différents niveaux de remplissage. Finalement, le problème de la correction simultanée avec un correcteur HIFOO d'ordre réduit est aussi analyséWe consider the problem of the active reduction of structural vibrations of a plane wing induced by the sloshing of large masses of fuel inside partly full tank. This study focuses on an experimental device composed of an aluminum rectangular plate equipped with piezoelectric actuators/sensors at the clamped end and with a cylindrical tip-tank, more or less filled with liquid, at the opposite free end. The control is performed through piezoelectric actuators and the main difficulty comes from the complex coupling between the flexible modes of the wing and the sloshing modes of the fuel. First, a partial derivative equation model is computed by coupling a plate equation with a Bernoulli equation for the fluid motion. After analyzing the energetic contribution of each mode, a state space approximation is established. After a model matching procedure, a control is computed by using the pole placement method and the H-infinity theory. Due to the large scale of the synthesis model and to the simultaneous performance requirements, a reduced-order H-infinity controller is computed using the HIFOO 2. 0 package and tested on the experimental device for different filling levels. Finally, the problem of simultaneous control with a reduced order HIFOO controller is tackled. Experimental results of this non-convex optimization problem are given and commented
31
Deng, Fengyan. "Contrôle modal autoadaptatif de vibrations de structures évolutives". Phd thesis, INSA de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00749905.
Abstract (sommario):
L'allègement des structures imposé par les réductions de coût se traduit par des structures de plus en plus souples qui les rendent de plus en plus sensibles aux vibrations. Le contrôle des vibrations devient donc un enjeu majeur dans de nombreuses applications industrielles et les limites des matériaux imposent maintenant un recours au contrôle actif de plus en plus fréquent. L'évolution des structures au cours du temps (viellisement, conditions aux limites, architecture, ...) pose le problème de la robustesse du contrôle. Par ailleurs, l'actionnement de plus en plus présent dans le domaine mécanique constitue à la fois une source supplémentaire de vibrations, mais aussi de contrôle et d'évolution d'architecture des structures. La thèse s'intéresse au contrôle actif autoadaptatif des vibrations permettant de maintenir automatiquement la performance et la stabilité des structures évolutives. Il s'agit donc de s'affranchir de la connaissance des causes et des informations sur les évolutions. La méthode proposée s'appuie sur un développement modal permettant de limiter le nombre de composants de contrôle et de cibler les modes à contrôler en limitant l'énergie de contrôle. Ainsi, il est nécessaire de reconstruire les caractéristiques du modèle modal indispensables pour réactualiser le contrôle en figeant seulement une structure de modèle. S'affranchissant à la fois des causes d'évolution de la structure et utilisant seulement une structure de modèle, la méthode est généralisable à toute application en mécanique des structures. La méthode proposée, basée sur l'utilisation d'un identificateur exploitant à la fois excitation et réponse de la structure, prend en compte les limites imposées par le contrôleur. Le modèle constitue le lien qui doit être établi entre identificateur et contrôle pour permettre la réactualisation. Par ailleurs, un compromis entre l'objectif d'atténuation des vibrations et les performances de l'identification est alors nécessaire du fait du couplage identification/contrôle apparaissant dans la boucle fermée. Ce compromis est également conditionné par le matériel utilisé. La méthode proposée est exploitée sur une structure discrète mettant en évidence une inversion de formes modales au cours de son évolution qui déstabilise un contrôle figé. Le choix opéré pour répondre aux différents compromis cités ci dessus a conduit à l'utilisation d'un contrôleur classique (LQG) et un identificateur basé sur la méthode des sous-espaces (N4SID). Cette application sur une structure simple a permis de caractériser un certain nombre de limites physiques : la bande passante, densité modale, vitesse d'évolution, Le contrôle modal autoadaptatif proposé s'avère robuste en performance et efficace lorsque la réactualisation est systématique. Une variante conditionnelle, toujours basée sur l'analyse de la réponse de la structure, est enfin proposée pour optimiser le processus de réactualisation afin de suivre plus efficacement les évolutions.
32
Dickens, John D. Aerospace & Mechanical Engineering Australian Defence Force Academy UNSW. "Dynamic characterisation of vibration isolators". Awarded by:University of New South Wales - Australian Defence Force Academy. School of Aerospace and Mechanical Engineering, 1998. http://handle.unsw.edu.au/1959.4/38675.
Abstract (sommario):
A vibration isolator is designed to reduce the vibration and structure borne noise transmitted from a vibratory source, such as machinery and equipment, to the supporting structure. The vibration and structure borne noise transmitted depends upon the dynamic properties of the foundation, the source mounting point and the vibration isolator. Therefore knowledge of the frequency dependent dynamic properties of vibration isolators is a necessary part of the acoustic prediction and control/reduction process. Vibration isolators may be characterised by measuring their four-pole parameters. A measurement procedure is proposed that employs the floating mass method, measures the direct forces and corrects for the errors introduced by the direct force measurement. Compared to the basic method, it extends the frequency limits of measurement in both directions. The development of a novel vibration isolator test facility that implements the proposed measurement procedure is described, and its satisfactory operation is experimentally demonstrated. The vibration isolator test facility is capable of characterizing vibration isolators commonly used in industrial and maritime applications, under service conditions. A method is proposed for measuring the four-pole parameters of a uni-directional asymmetrical vibration isolator under static load. The method is called the two masses method, and is suitable for determining the four???pole parameters of active vibration isolators with feedback control. The method is also applicable to uni-directional symmetrical and bi-directional symmetrical and bi-directional asymmetrical vibration isolators. It may be regarded as a universal method for characterising vibration isolators. Experimental data is presented and the method is validated. Modelling of vibration isolators is complicated by the highly non-linear nature of their rubber elements. The notion of an effective rubber cylinder is proposed to account for the barrelling of rubber elements under static load. Consequently, a general static compression model is proposed that applies to vibration isolators having unfilled and filled rubber elements of regular prismatic shapes. The model predicts the dependence of the four-pole parameters on the compression ratio of the rubber element. The predictions derived from the effective rubber cylinder and general static compression model agree excellently with experimental work of this study and other researchers.
33
Jubinville, François. "Calcul de la réponse d'une structure soumise à une excitation aléatoire". Sherbrooke : Université de Sherbrooke, 2001.
34
Ducarne, Julien. "Modélisation et optimisation de dispositifs non-linéaires d’amortissement de structures par systèmes piézoélectriques commutés". Thesis, Paris, CNAM, 2009. http://www.theses.fr/2009CNAM0633/document.
Abstract (sommario):
Afin de réduire les vibrations d'une structure, on utilise des éléments piézoélectriques connectés à des circuits électriques passifs. L'objectif est de se rapprocher de l'efficacité du contrôle actif sans en supporter la complexité et la consommation. On considère d'abord l'association d'une résistance (qui a un effet similaire à un amortissement visqueux) et éventuellement d'une inductance (permettant de réaliser un oscillateur accordé) aux éléments piézoélectriques. Ces systèmes ont des propriétés intéressantes, mais sont peu efficaces à moins d'un accord très précis de l'inductance. Afin d'obtenir des performances élevées sans accord précis, on étudie un circuit à commutation, qui se ferme et s'ouvre à des instants bien précis. L'effet de la charge, qui freine la structure, s'apparente à un frottement sec. En synchronisant les commutations sur les vibrations, le système est auto-adaptatif et peut être auto-alimenté. Les fortes non-linéarités entraînent une excitation haute fréquence de la structure qui peut rendre la synchronisation problématique. Deux modèles électromécaniques (analytique et éléments finis) réduits sont proposés, permettant de décrire la dynamique du système complet de manière précise et de mettre en valeur le couplage entre un mode de vibration et le circuit électrique. Ce couplage est déterminant pour la réduction de vibrations. Une étude de l'influence de divers paramètres permet d'optimiser les éléments piézoélectriques, les circuits, et les instants de commutation. Ces résultats sont vérifiés expérimentalement. On constate un bon accord avec la théorie ; la difficulté de synchroniser correctement la commutation est aussi constatéeIn order to reduce the vibrations of a mechanical structure, one can use piezoelectric elements connected to passive electrical circuits. The goal is to achieve the same efficiency as active vibration control without the associated complexity and energy consumption. First the use of a resistor (with an effect similar to viscous damping) and eventually of an inductor (allowing the creation of a tuned resonator) for the circuit is considered. These systems have interesting properties, but are not very efficient, except in the case of a finely tuned inductor. In order to obtain good performance without requiring a precise tuning, a switching circuit is considered. The switching process is synchronized on the vibrations, and the effect of the free electric charge (similar to a dry damping) reduces the vibrations. This system is self-adaptive and can be self-powered. However, the strong non-linearities create a high frequency excitation which may disturb the switch timing. Two different reduced electromechanical models (analytical and finite element) are proposed, allowing a description of the whole system dynamics with accuracy and to emphasize the coupling between one vibration mode and the circuit. This coupling is found to be decisive for the performance in vibration reduction. A study of the influence of various parameters allow the optimisation of the piezoelectric elements, electric circuits and switch timing. These results are experimentally tested and a good agreement with the predictions is obtained ; the difficulty of switch timing is also noticed
35
Pan, Zhifang. "AB initio calculation of vibration frequencies, infrared intensities, and structures for: H₄+, LI₂H₂+ and LI₄+, and deuterated analogs : AB initio study of potential surface for decomposition of H₄ cluster derived from charge neutralization of H₄+Ion : AB initio study of the structures and vibrational frequencies of CF₄-and CF₃CL-". Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/27073.
36
Bail, Justin L. "Non-desctructive investigation & FEA correlation on an aircraft sandwich composite structure". Akron, OH : University of Akron, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1196702586.
Abstract (sommario):
Thesis (M.S.)--University of Akron, Dept. of Civil Engineering, 2007."December, 2007." Title from electronic thesis title page (viewed 02/25/2008) Advisor, Wieslaw Binienda; Faculty readers, Craig Menzemer, Robert Goldbert; Department Chair, Wieslaw Binienda; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
37
Zäll, Emma. "Footbridge Dynamics : Human-Structure Interaction". Licentiate thesis, KTH, Bro- och stålbyggnad, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-224527.
Abstract (sommario):
For aesthetic reasons and due to an increased demand for cost-effective and environmentally friendly civil engineering structures, there is a trend in designing light and slender structures. Consequently, many modern footbridges are susceptible to excessive vibrations caused by human-induced loads. To counteract this, today's design guidelines for footbridges generally require verification of the comfort criteria for footbridges with natural frequencies in the range of pedestrian step frequencies. To ensure that a certain acceleration limit is not exceeded, the guidelines provide simplified methodologies for vibration serviceability assessment. However, shortcomings of these methodologies have been identified. First, for certain footbridges, human-structure interaction (HSI) effects might have a significant impact on the dynamic response. One such effect is that the modal properties of the bridge change in the presence of a crowd; most importantly, the damping of the bridge is increased. If this effect is neglected, predicted acceleration levels might be overestimated. Second, as a running person induces a force of greater amplitude than a walking person, a single runner might cause a footbridge to vibrate excessively. Hence, the running load case is highly relevant. These two aspects have in common that they are disregarded in existing design guidelines. For the stated reasons, the demand for improvements of the guidelines is currently high and, prospectively, it might be necessary to require the consideration of both the HSI effect and running loads. Therefore, this licentiate thesis aims at deepening the understanding of these subjects, with the main focus being placed on the HSI effect and, more precisely, on how it can be accounted for in an efficient way. A numerical investigation of the HSI effect and its impact on the vertical acceleration response of a footbridge was performed. The results show that the HSI effect reduces the peak acceleration and that the greatest reduction is obtained for a crowd to bridge frequency ratio close to unity and a high crowd to bridge mass ratio. Furthermore, the performance of two simplified modelling approaches for consideration of the HSI effect was evaluated. Both simplified models can be easily implemented and proved the ability to predict the change in modal properties as well as the structural response of the bridge. Besides that, the computational cost was reduced, compared to more advanced models. Moreover, a case study comprising field tests and simulations was performed to investigate the effect of runners on footbridges. The acceleration limit given in the design guideline was exceeded for one single person running across the bridge while a group of seven people walking across the bridge did not cause exceedance of the limit. Hence, it was concluded that running loads require consideration in the design of a footbridge.På grund av estetiska skäl och en ökad efterfrågan på kostnadseffektiva och miljövänliga konstruktioner är merparten av de gångbroar som konstrueras idag förhållandevis lätta och slanka. Med anledning av detta ökar risken för att stora svängningar uppstår på grund av dynamisk belastning från människor på bron. För att motverka att detta inträffar kräver dagens normer att komforten verifieras för gångbroar med egenfrekvenser inom området för människans stegfrekvens. Komforten verifieras genom att säkerställa att ett visst accelerationskriterium inte överskrids. För detta ändamål finns handböcker som tillhandahåller förenklade beräkningsmetoder för uppskattning av accelerationsnivåer. Brister i dessa beräkningsmetoder har emellertid identifierats. För det första kan olika typer av människa-bro-interaktion (HSI) ha en betydande inverkan på responsen hos vissa broar. Exempel på en HSI-effekt är att brons modala egenskaper förändras när människor befinner sig på bron; i huvudsak sker en ökning av brons dämpning. Om denna effekt inte tas i beaktande föreligger stor risk att överskatta förväntade accelerationsnivåer. För det andra är kraften från en löpare större än kraften från en gående person vilket gör att en ensam löpare på en gångbro kan ge upphov till accelerationsnivåer som överskrider gränsvärdena för komfort. Löpande personer är därför ett mycket relevant lastfall. Befintliga normer uttrycker inte explicit att någon av dessa aspekter bör tas i beaktande. Behovet av förbättrade riktlinjer för hur normerna bör tillämpas är därför mycket stort och i framtiden kan det bli nödvändigt att kräva att både HSI-effekter och löparlaster tas i beaktande. Därför syftar denna licentiatavhandling till att bidra till en fördjupad förståelse inom dessa två ämnen, med huvudfokus på ovan nämnda HSI-effekt i allmänhet och hur den kan beaktas på ett enkelt, noggrant och tidseffektivt sätt i synnerhet. En numerisk undersökning av HSI-effekten och dess inverkan på den vertikala responsen hos en gångbro genomfördes. Resultaten visar att HSI-effekten reducerar den maximala accelerationen och att störst reduktion erhålls då folksamlingen och bron har ungefär samma egenfrekvens och då folksamlingens massa är stor i förhållande till brons massa. Vidare utvärderades två förenklade metoder för beaktande av HSI-effekten vilka kan implementeras av konstruktörer med grundläggande kunskaper inom strukturdynamik. Det konstaterades att båda metoderna uppskattar HSI-effekten såväl som brons respons förhållandevis väl samtidigt som de reducerar beräkningstiden något jämfört med mer avancerade metoder. Effekten av löpare på gångbroar studerades genom en fallstudie med fältmätningar. Utifrån resultaten från dessa fältmätningar kunde det konstateras att accelerationsgränsen som anges i normerna överskreds när en ensam löpare sprang över bron men inte när en grupp på sju personer gick i takt över samma bro. Därför drogs slutsatsen att löparlaster bör tas i beaktande vid dimensionering av en gångbro.
QC 20180320
38
Robert, Séverine. "Description globale de la structure de vibration-rotation de la molécule d'acétylène". Doctoral thesis, Universite Libre de Bruxelles, 2009. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210307.
Abstract (sommario):
Afin de progresser dans la compréhension de la structure de vibration-rotation de l'acétylène dans son état électronique fondamental, un modèle global a été développé avec succès pour trois de ses isotopologues, permettant d'attribuer de nouvelles données de spectres enregistrés sous diverses conditions expérimentales. L'ensemble des programmes d'analyse rovibrationnelle globale conçus à l'Université Catholique de Louvain par le Pr. A. Fayt et al. ont été utilisés pour répondre aux demandes de collaborateurs tels que les Prs. A. Campargue, A. Jolly ou encore R. Georges dans le cadre de plusieurs problèmes de type spectroscopique, notamment pour des applications astrophysiques. Le modèle global et son pouvoir prédictif mis ainsi à l'épreuve, nous avons démontré la validité de nos jeux de paramètres pour ces trois molécules.Concernant l'isotopologue principal, $H^{12}C^{12}CH$, 14 nouvelles bandes ont été mises à jour à partir de spectres enregistrés en CRDS à Grenoble par A. Campargue et al. Une analyse rovibrationnelle globale a été effectuée jusqu'à une énergie de 8600 cm$^{-1}$. 10750 raies ont été ajustées simultanément sur les 12137 attribuées dans la littérature. 266 paramètres ont été déterminés par la méthode de moindres-carrés. La déviation standard sans dimension du fit est de 0.92. La bande $u_{5}$-$u_{4}$, centrée vers 117 cm$^{-1}$ a été simulée. La valeur du moment de transition associé, $
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
39
PONTE, ELAINE CRISTINA RODRIGUES. "EVALUATION OF REFINED MODELS FOR INSTABILITY AND VIBRATION OF TWO-DIMENSIONAL STRUCTURE". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2007. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=11334@1.
Abstract (sommario):
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOEste trabalho consiste em desenvolver e avaliar modelos clássicos de elementos finitos combinados com funções polinomiais adicionais, para a obtenção de cargas críticas de instabilidade e freqüências naturais de estruturas planas, com seus respectivos modos. O objetivo consiste em buscar uma sistemática confiável para obter estimativas de deformações localizadas em regime próximo ao colapso. Utiliza-se o método dos Elementos Finitos em combinação com o método clássico de Rayleigh-Ritz. Como elemento fundamental para tal estudo, emprega-se o elemento retangular de Barber-Weaver, que contém quatro nós, cada nó com duas translações e duas rotações independentes (equivalentes a uma rotação e uma distorção angular). Esse elemento é enriquecido com funções de deslocamentos adicionais internas e de contorno, em forma de séries polinomiais gerais. Esse conjunto de funções é incorporado nas expressões de energia para levar ao estabelecimento de matrizes de rigidez elástica, geométrica e de massa. Tais matrizes permitem estabelecer problemas generalizados de autovalor para obtenção de cargas críticas e freqüências, e respectivos modos de flambagem e vibração. Para os estudos numéricos comparativos apresentados nos exemplos, são implementadas diversas rotinas usando o software Maple 9.0. Os resultados mostram que a metodologia apresentada pode ser usada no desenvolvimento de uma técnica aplicável à obtenção de modos globais e localizados de instabilidade, quando há a combinação de efeitos não lineares geométricos e de material.
This work consists in developing and evaluating classical of finite element models combined with additional polynomial functions, to obtain critical loads of instability and natural frequencies of plane structures, and respective modes. The objective is to search for a reliable technique to get estimates of localized deformations near to collapse. The Finite Elements method is used in combination with the classic method of Rayleigh-Ritz. As a basic element for such study, the rectangular element of Barber-Weaver is used, containing four nodes, each one with two translations and two independent rotations (equivalents to a rotation and an angular distortion). This element is enriched with additional internal displacement functions and with functions on the boundary, forming general polynomial series. These nodal functions are incorporated in the energy expressions leading to the establishment of elastic stiffness, geometric, and mass matrices. Such matrices allow the establishment of generalized eigenvalue problems to obtain critical loads and frequencies, and the respective modes of buckling and vibration. For the comparative numerical studies presented in the examples, several routines are implemented using software Maple 9.0. The results show that the methodology presented herein can be used in the development of an applicable technique to the ascertainment of instability in global and located modes, when there is a combination of geometric nonlinear and material effects.
40
Lu, Ya Nan. "Static and forced vibration analysis of plane truss structure with geometrical nonlinearity". Thesis, University of Macau, 2015. http://umaclib3.umac.mo/record=b3335487.
41
Hsieh, Chih-Wei, e 謝志瑋. "Study of vibrational structure of vibration-based microgenerator". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/80537360038039425709.
Abstract (sommario):
碩士國立中山大學
機械與機電工程學系研究所
92
The main components of the vibration-based microgenerator incorporate vibratile structure, magnetic thin film, and coils. In this thesis work, bulk-micromachining technology and laser-micromachining technology were used to fabricate the vibratile structure of the microgenerator. And this is the beginning of the development of the microgenerator. Bulk-micromachining technology was widely used in micro-electromechanical system (MEMS). The most advantage of the technology is that it can be integrated with IC process in the future. And the roughness of the wafer is the key point of the etching process. In addition, 355nm UV Nd:YAG laser was also used to fabricate the vibratile structure. The period of fabricating prototype can be shortened by laser-micromachining. In laser-micromachining system, the dual-prism was used to change the direction of the laser beam by adjusting the initial phase of one of the prisms. When the laser beam moves relatively to workstation, the cutting process can be proceeded. By this system, the cutting linewidth is controllable. This technology has be used to fabricate the microstructure successfully, and the aspect ratio is up to 10, and the feature size is 50µm. Circular spiral spring structure was fabricated successfully, and it is to be the vibratile structure of the microgenerator. Finite element software ANSYS was used to simulate the dynamic characterization of the vibratile structure and the vibration testing experiment was carried out. The result shows that the experimental resonant frequency is very close to the simulative resonant frequency. So this vibratile structure can be used in microgenerator.
42
Chen, Kuan-Chih, e 陳冠智. "Vibration Reduction Analysis of Dynamic Vibration Absorber in Beam Structure". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/wz8ssn.
Abstract (sommario):
碩士國立臺北科技大學
製造科技研究所
105
In this paper, based on continuous system beam structure as a dynamic vibration absorber and analyzed the vibration reduction of beam structure. The equation of motion of the beam structure with base excitation is derived by using energy principle. The dynamic vibration absorber model of the continuous system is derived from the dynamic vibration absorber model with two-degree of freedom, and then the effect of vibration absorber on the structure of viscous damped beam is analyzed by Transfer Matrix Method. The influence of design parameters, which are the mass ratio and damping ratio, is analyzed to research the vibration reduction of the first two modes of the beam structure. When the resonance frequencies of the vibration absorber are the same as the excitation frequencies of the base, the amplitude of the free end of the beam structure is the smallest. Finally, the results show that the viscous damping is located on the maximum bending moment of the beam structure or absorber can reduce the amount of displacement in the resonance.
43
Li, Tai-Wei, e 李泰緯. "Vibration Control of a Frame Structure". Thesis, 1998. http://ndltd.ncl.edu.tw/handle/62940964616049122921.
44
Chang, Sheng-Tien, e 張勝添. "Vibration Analysis of LCD TV Neck Structure". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/7yf5bd.
Abstract (sommario):
碩士國立臺北科技大學
製造科技研究所
98
In the numerous liquid crystal product design, the neck design is very important. It will affect television''s balance, the unstable balanced design easy to create liquid crystal''s falling and to cause the product broken or falls to make consumer being injured. The major part of neck designs are use die casting, mainstream is light and thin design, so this article will to use punch method to manufacture neck to replace die casting method. This study is mainly using “finite element method” to simulate different strengthens form design and process in Modal analysis and Transient analysis. The result of research showed that from the transient analysis simulation and use of applied 20N force on LCD TV. Type3 is better than Type1 and Type2,it can effectively reduce time and improve the vibration attenuation phenomenon.
45
Hsu, Yu-Hsiung, e 言午裕雄. "Suspended Sediment Concentration Monitoring by Structure Vibration". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/72954591816062687641.
Abstract (sommario):
博士逢甲大學
土木暨水利工程博士學位學程
99
This study proposed an innovative method for real-time monitoring and testing of fluid density and suspended sediment concentration (SSC) based on the principle of acoustic vibration. Loading effects on the boundary of a vibrating tube from the surrounding fluids cause regular variations in the resonance frequencies in a vibrating tube or plate. Physical properties and variation mechanisms of the density and SSC influencing the test fluid were investigated. Measuring devices on established vibrating tubes and plates were used to measure the properties of resonance frequencies, and acoustic vibrations in the tubes and plates were tested using fluids of various densities and conditions. A strain gauge that could sense high frequencies was installed on the vibrating bodies and measured the vibration properties of the tubes or plates. The vibration signals were analyzed by Fourier transform to obtain the main resonance frequency. The preliminary experiment investigated the influences of immersion depth, structure, and arrangement (level or upright) of the vibrating bodies; the formal experiment investigated the impacts of fluid density, sediment particle size, SSC, and structural properties of the vibrating body on the resonance frequencies of the tube or plate. The results were further discussed and analyzed. This study also applied finite element analysis in COMSOL Multiphysics to construct a model and carry out a simulation, the results of which confirmed the experimental results. After comparison of the simulated results and experimental results under the various conditions of vibration tube and plate properties and fluid densities, regularities were found among the combinations of different modes with the structural properties of various vibrating bodies. The results of the sediment concentration experiment specifically indicated a corresponding trend between calibration concentration and resonance frequency, thereby establishing a relationship between SSC and resonance frequency.
46
Wu, Tong-Ching, e 吳東憬. "Vibration Analysis of Cone-type Shell Structure". Thesis, 2000. http://ndltd.ncl.edu.tw/handle/12763223632869555808.
Abstract (sommario):
碩士國立交通大學
機械工程系
88
In this thesis, vibration characteristics of the conical shell structures are studied, especially the characteristics of concentric modes with circumferential wave numbers equaling to one. For given edge loads, modal characteristics and responses in frequency range from 1k Hz to 10k Hz are determined for different shell structures. The changes of the modal frequencies and mode shapes are presented with different conical angles, profiles, boundary conditions, and material constants. In analyzing thicker conical shells, shear along the thickness direction is considered based on the first-order shear deformation. The finite element analysis of the shell structures is achieved using the commercial code MSC NASTRAN. Experiments have been performed to verify the accuracy of the theoretical predictions. The effects of material properties on the behaviors of the shell structures have also been studied. It has been found composite conical shells have different behaviors from the isotropic ones. Both theoretical and experimental results on isotropic and composite conical shells are given for comparison.
47
陳家誠. "Vibration Measurement and Suppression for Scanner Structure". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/09873025694305635913.
Abstract (sommario):
碩士國立成功大學
航空太空工程學系
87
The subject of this thesis is to study the noise stimulated by the structure when the scanner is under operation，and adopting rubber cushion to eliminate the amount of noise. We use six models with different structural conditions to test，and do the experiments to analysis the vibrations resulted from the structure and the air in the scanner respectively，in order to find the source of noise from vibration. We use Structural Dynamics Modification (SDM) to predict the influence of structure vibration by adding rubber with different materials.
48
YEN-CHIN, CHIANG, e 江彥瑾. "Using Optic Fiber Sensor in Structure Vibration Control". Thesis, 1994. http://ndltd.ncl.edu.tw/handle/32884822327786971669.
Abstract (sommario):
碩士國立臺灣大學
應用力學研究所
82
We present experimental methods for practical implementati -onof few-mode cycle-core sensora. Techniques for desenstizing the lead-in and lead-out fibers are descussed and resuults of a vibration sensors embedded in a graphite-epoxy composite are pr- sented. A scheme using a single mide fiber as the lead-out fiber is successfully impemented. Detection techniques for few- mode fibersensors are reviewed and a novel fringe-counting method to unambiguously detect the amplitude and direction of dynamic str- ain is reported for the first time.
49
Yu-ShengLu e 呂毓笙. "Vibration Control of Compliant Structure Using Acceleration Feedback". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/95769534796384877843.
Abstract (sommario):
碩士國立成功大學
機械工程學系
102
Automatic optical inspection (AOI) systems adapted on a movable gantry have been widely used in modern large area inspection tasks. The performance of motion control directly affects the accuracy and perhaps the yield of the entire process. To maximize process yield, the gantry should maneuver as fast as possible in order to maximize the throughput. However, this action will generate significant motion-induced vibration that excites the flexible modes of the systems, which may increase the settling time and reduce the inspection efficiency. As a result, a trade-off exists between the speed of movement and the achieved settling time. An alternative approach is to mount AOIs on a controllable stage and to eliminate the relative vibration between the AOI and the corresponding object to be inspected. By this approach, the effective bandwidth can be improved. However, to realize this concept, conventional position sensors cannot be used due to lacks of an absolute reference. An alternative solution is to use accelerometer for providing relative displacement by integrating the measurable accelerations. This solution brings potentially two problems: first, the possible drifting of low frequency signals and second, a re-design of feedback control scheme. By experiments, we successfully develop the anti-drift integrator, which combines two second-order Sallen-Keys high-pass filters and original model of hardware integrator for enhancing the drifting rejection. Otherwise, three controllers of acceleration feedback was designed to enhance the vibration of double clam beam test platform, Nevertheless, through detail step and sinusoidal tests simulation and experimental correlations and interactions, these three controllers have been successfully implemented.In the study, we have realized the integration of acceleration feedback controller and the model of anti-drift integrator for suppressing low frequency drifting by combining of the models of the hardware integrator and two Sallen-Key high-pass filters.. Second, by both simulation and experimental investigation, the acceleration feedback controllers have gotten less effect than the displacement feedback controllers. Although this study was motivated by the needs of AOI vibration control, it is not limited in this application only. The methodology proposed can be used in other applications related to precision positioning control using inertial sensor, such as active vibration control in precision semiconductor processing equipment.
50
Kang, Po Shyang, e 康博翔. "The hybrid control for vibration of equipment-structure". Thesis, 1994. http://ndltd.ncl.edu.tw/handle/48461673694967982313.
Abstract (sommario):
碩士國立中央大學
土木工程研究所
82
The dynamic response behavior of equipment-structures controlled by a hybrid control system is studied in this research.The hybrid control system used in this studied is constituted by the passive resilient-friction base isolators (RFBI) and the active actuator.Dynamic responses of equipment- structure installed on the floor are analyzed by using the floor response spectrum approach.For passive control system, the stiffness and friction coefficients of RFBI system dominate the controlled effectiveness of the base isolators.To reduce the relative displacement of isolators, the active actuator is used for which the control force is determined by using the classical optimal closed-loop control law. In order to gain the desired objective, the active actuator is designed to contribute damping force only. Thus, the performance weighting matrix, Q, of active actuator has been derived in this report to obtain the desired system damping ratio when the hybrid control system is used.The performance of the hybrid control system is presented in the form of response spectra.Parameters studied in this report are friction coefficient of RFBI system and coefficients of the performance weighting matrix, Q. Numerical results have shown that, although, the RFBI system can reduce the dynamic responses of equipment-structure very effectively.The hybrid control system can provide much better results than the RFBI system alone.