According to the regulation announced by Bureau of Standard, Metrology & Inspection (BSMI) of Ministry of Economic Affairs (MOEA), lamp fixtures must follow safety and electromagnetic compatibility (EMC) standards. However, the self-ballasted fluorescent lamps in the fixture should only be approved by the safety test but not regulated by EMC standard. Obviously, fixtures without light bulbs do not generate any electromagnetic noise. Electromagnetic interference (EMI) comes from the fluorescent light bulb embedded with an electronic ballast which included an inverter with high-frequency switching. A variety of tests demonstrate evidently that a fixture with different self-ballasted compact fluorescent lamps may possibly violate the EMC standard, revealing the absurdity of the regulation. In fact, self-ballasted fluorescent lamps use mostly self-excited electronic ballasts. The operating frequencies for this kind of electronic ballasts can not be precisely controlled due to the influence of many factors. They are not operated at a specified frequency but in a frequency range. This means that the generated EMI spectrum is hardly predicted, especially when a fixture is fitted by light bulbs from several manufacturers. This research inducts the worst cases from numerous measurements on a fixture with 1 piece to 8 pieces of light bulbs, and then attempts to design an EMI filter for all cases. As a result, a lamp fixture with the filter at the line input terminal can suppress the EMI. As long as the consumer buys the lamp fixture which are installed with the EMI filter together with any bulb in use, EMI noise can comply with standard limits.

Brake squeal is a common noise problem encountered in the automotive industry. Higherfriction coefficients and weight reduction recently led to higher vibration levels in the audiblefrequency range. This quality issue becomes economic due to penalties imposed to the brakesupplier although no robust design method exists. The industrial practice thus relies on costlyprototyping and adjustment phases. The evolution of computational power allows computationof large mechanical assemblies, but non-linear time simulations generally remain out of reach.In this context, the thesis objective is to provide numerical tools for squeal resolution at earlydesign stages.Parameterized reduction methods are developed, using system real modes as Rayleigh-Ritzvectors, and allow very compact reduced models with exact real modes. The proposed ComponentMode Tuning method uses the components free/free modes as explicit degrees of freedom.This allows very quick sensitivity computation and reanalyzes of an assembly as function oflocal component-wise parameters. Non-linear time simulations are made possible through twoingredients. A modified non-linear implicit Newmark scheme and a fixed Jacobian are adaptedfor contact vibrations. The brake is reduced keeping a superelement with exact real modes anda local non-linear finite element model in the vicinity of the pad/disc interaction.A set of design tools is illustrated for a full industrial brake model. First, instant stabilitycomputations and complex mode trajectories are studied. Modal interactions and non-linearphenomena inside the limit cycles are thus well understood. Time/frequency correlations areperformed using transient modal identification and space-time decomposition. A time domainmodal damping model is also shown to be very useful. The modification of a critical componentfor squeal resolution is finally tested and validated.

No description available.

Le crissement de frein est une nuisance sonore classique dans l’automobile. L’augmentationdes coefficients de friction et la réduction de la masse mènent aujourd’hui à de hauts niveauxvibratoires dans les fréquences auditives, et ces problèmes de qualité se traduisent par des pénalités économiques aux équipementiers, bien qu’il n’existe pas de méthode robuste de conception.La pratique industrielle repose donc sur de coûteuses phases de prototypage et d’ajustement.L’évolution de la puissance de calcul permet le calcul de grands assemblages mécaniques mais lesétudes vibratoires non-linéaires restent généralement hors de portée. Dans ce contexte, l’objectifde la thèse est de fournir, dès les phases de conception, des outils de conception numérique d’aideà la résolution du crissement.Une méthode de réduction paramétrée utilisant comme base de Rayleigh-Ritz les modes réelsdu système assemblé permet la génération de modèles réduits très compacts, avec modes réelsexacts. La méthode proposée d’ajustement des modes de composants utilise les modes libresde composants comme degrés de liberté explicites. L’étude des sensibilités et la réanalyse d’unassemblage en fonction de modifications à l’échelle d’un composant deviennent possibles. Lesétudes temporelles non-linéaires sont rendues possibles par deux développements. Un schémade Newmark non-linéaire modifié et un Jacobien fixe adapté aux vibrations de contact sontintroduits. Le frein est réduit en un superélément avec modes réels exacts et une zone nonréduite au niveau du contact.Un ensemble d’outils de conception est illustré sur un modèle industriel de frein. La stabilitéinstantanée et les trajectoires de modes complexes sont étudiées. Les interactions modales et lesphénomènes non-linéaires au sein des cycles limites sont alors mieux compris. Des corrélationstemps/fréquence sont obtenues par l’identification modale instantanée et une décompositionespace-temps. La grande utilité d’un modèle temporel d’amortissement modal est illustrée.Enfin, la modification d’un composant critique au crissement est testée et validée. / Brake squeal is a common noise problem encountered in the automotive industry. Higherfriction coefficients and weight reduction recently led to higher vibration levels in the audiblefrequency range. This quality issue becomes economic due to penalties imposed to the brakesupplier although no robust design method exists. The industrial practice thus relies on costlyprototyping and adjustment phases. The evolution of computational power allows computationof large mechanical assemblies, but non-linear time simulations generally remain out of reach.In this context, the thesis objective is to provide numerical tools for squeal resolution at earlydesign stages.Parameterized reduction methods are developed, using system real modes as Rayleigh-Ritzvectors, and allow very compact reduced models with exact real modes. The proposed ComponentMode Tuning method uses the components free/free modes as explicit degrees of freedom.This allows very quick sensitivity computation and reanalyzes of an assembly as function oflocal component-wise parameters. Non-linear time simulations are made possible through twoingredients. A modified non-linear implicit Newmark scheme and a fixed Jacobian are adaptedfor contact vibrations. The brake is reduced keeping a superelement with exact real modes anda local non-linear finite element model in the vicinity of the pad/disc interaction.A set of design tools is illustrated for a full industrial brake model. First, instant stabilitycomputations and complex mode trajectories are studied. Modal interactions and non-linearphenomena inside the limit cycles are thus well understood. Time/frequency correlations areperformed using transient modal identification and space-time decomposition. A time domainmodal damping model is also shown to be very useful. The modification of a critical componentfor squeal resolution is finally tested and validated.

Vibrações mecânicas oferecem grande limitação para a produtividade, qualidade ou mesmo viabilidade das operações de usinagem, especialmente quando se trata das autoexcitadas (chatter). Neste trabalho, foram desenvolvidas estratégias que tem como objetivo diminuir a intensidade de vibrações em processos de torneamento por meio do acoplamento de material piezelétrico ao suporte de ferramenta em conjunto com uso de shunts resistivo, indutivo e resistivo-indutivo em série ou em paralelo, criando assim estruturas eletromecânicas passivamente amortecidas. Para tanto, foram construídos modelos eletromecânicos de parâmetros distribuídos para mostrar a capacidade que tais estruturas eletromecânicas possuem em oferecer um maior amortecimento quando comparadas com estruturas mecânicas convencionais. Com os modelos construídos, foi possível verificar a influência causada pela espessura da camada de material piezelétrico bem como a influência dos shunts no comportamento da estrutura, sendo constatado que camadas mais espessas aumentam a capacidade de amortecimento da estrutura e que os shunts resistivo-indutivo, tanto em série quanto em paralelo, funcionam como um amortecedor dinâmico de vibrações amortecido e oferecem o melhor desempenho. A seguir, construiu-se o diagrama de lóbulos de estabilidade para comparar as estruturas com e sem shunts e observou-se que as estruturas com shunts resistivo-indutivo possuem um melhor desempenho. Também foram executados testes de impacto (tap tests) para a verificação experimental do comportamento da estrutura quando conectadas aos shunts e os resultados mostraram que há um maior amortecimento. Considerando os resultados obtidos, acredita-se que seja possível melhorar o desempenho de processos de torneamento usando material piezelétrico. / Mechanical vibrations offer great limitation for the productivity, quality or even feasibility of the machining operations when chatter is present. In this work it was developed strategies aiming to diminish the intensity of the vibration in turning processes. By coupling a piezoelectric material with a turning tool and by using different associations of resistive and inductive shunt (series or parallel) it was created electromechanical structures passively damped. Electromechanical models of distributed parameters were developed in order to show the capacity that these structures has to offer a greater dumping when compared with conventional mechanical structures. By using these constructed models it was possible to verify the influence of the thickness of the piezoelectric material as well as the influence of shunts in the behavior of structure. It was observed that thicker layers increase the damping capacity of the structure that resistive-inductive shunt (series or parallel) works as a damped dynamic vibration absorber which offer better performance. Latter was developed a stability lobes diagram in order to compare the structures with and without shunts and it was observed that structures connected to resistiveinductive shunt has a better performance. Tap tests were performed for the purpose of study the experimental behavior of the structure connected to shunt and results showed that there is a better damping in this situation. Considering the results obtained, is fair to believe that is possible to improve turning process by using piezoelectric materials.

Vibrações mecânicas oferecem grande limitação para a produtividade, qualidade ou mesmo viabilidade das operações de usinagem, especialmente quando se trata das autoexcitadas (chatter). Neste trabalho, foram desenvolvidas estratégias que tem como objetivo diminuir a intensidade de vibrações em processos de torneamento por meio do acoplamento de material piezelétrico ao suporte de ferramenta em conjunto com uso de shunts resistivo, indutivo e resistivo-indutivo em série ou em paralelo, criando assim estruturas eletromecânicas passivamente amortecidas. Para tanto, foram construídos modelos eletromecânicos de parâmetros distribuídos para mostrar a capacidade que tais estruturas eletromecânicas possuem em oferecer um maior amortecimento quando comparadas com estruturas mecânicas convencionais. Com os modelos construídos, foi possível verificar a influência causada pela espessura da camada de material piezelétrico bem como a influência dos shunts no comportamento da estrutura, sendo constatado que camadas mais espessas aumentam a capacidade de amortecimento da estrutura e que os shunts resistivo-indutivo, tanto em série quanto em paralelo, funcionam como um amortecedor dinâmico de vibrações amortecido e oferecem o melhor desempenho. A seguir, construiu-se o diagrama de lóbulos de estabilidade para comparar as estruturas com e sem shunts e observou-se que as estruturas com shunts resistivo-indutivo possuem um melhor desempenho. Também foram executados testes de impacto (tap tests) para a verificação experimental do comportamento da estrutura quando conectadas aos shunts e os resultados mostraram que há um maior amortecimento. Considerando os resultados obtidos, acredita-se que seja possível melhorar o desempenho de processos de torneamento usando material piezelétrico. / Mechanical vibrations offer great limitation for the productivity, quality or even feasibility of the machining operations when chatter is present. In this work it was developed strategies aiming to diminish the intensity of the vibration in turning processes. By coupling a piezoelectric material with a turning tool and by using different associations of resistive and inductive shunt (series or parallel) it was created electromechanical structures passively damped. Electromechanical models of distributed parameters were developed in order to show the capacity that these structures has to offer a greater dumping when compared with conventional mechanical structures. By using these constructed models it was possible to verify the influence of the thickness of the piezoelectric material as well as the influence of shunts in the behavior of structure. It was observed that thicker layers increase the damping capacity of the structure that resistive-inductive shunt (series or parallel) works as a damped dynamic vibration absorber which offer better performance. Latter was developed a stability lobes diagram in order to compare the structures with and without shunts and it was observed that structures connected to resistiveinductive shunt has a better performance. Tap tests were performed for the purpose of study the experimental behavior of the structure connected to shunt and results showed that there is a better damping in this situation. Considering the results obtained, is fair to believe that is possible to improve turning process by using piezoelectric materials.

An approach with ¡§consecutive orthogonal arrays (COA)¡¨ is proposed for solving the problems in designing power electronic circuits. This approach is conceptually based on the orthogonal array method, which has been successfully implemented in quality engineering. The circuit parameters to be determined are assigned as the controlled variables of the orthogonal arrays. Incorporating with the inferential rules, the average effects of each control variable levels are used as the indices to determine the control variable levels of the subsequent orthogonal array. By manipulating on COA, circuit parameters with the desired circuit performances can be found from an effectively reduced number of numerical calculations or experimental tests. In this dissertation, the method with COA is implemented on solving four problems often encountered in the design of power electronic circuits. The first problem one has to deal with is to find a combination with the best performance from a great number of analyzed results. The illustrative example is the design of LC passive filters. Using COA method, the desired component values of the filter can be effectively and efficiently found with far fewer calculations. The second design problem arises from the non-linearity of circuit. An experienced engineer may be able to figure out circuit parameters with satisfactory performance based on their pre-knowledge on the circuit. Nevertheless, they are always questioned whether a better choice can be made. The typical case is the self-excited resonant electronic ballast with the non-linear characteristics of the saturated transformer and the power transistor storage-time. In this case, the average effects of COA obtained from experimental tests are used as the observational indexes to search a combination of circuit parameters for the desired lamp power. The third problem is that circuit functions are mutually exclusive. The designers are greatly perplexed to decide the circuit parameters, with which all functions should be met at the same time. The method with COA is applied to design a filter circuit to achieve the goals of low EMI noise and high power factor simultaneously. Finally, one has to cope with the effects of the uncontrolled variables, such as: ambient temperature, divergence among different manufacturers, and used hours. By applying COA with inferential rules, electronic ballasts can be robustly designed to operate fluorescent lamps at satisfied performance under the influence of these uncontrolled variables.

No description available.

The diploma thesis deals with the determination of the self-excited and forced pulsation of the real fluid in the cylindrical area and in the annulus. It also focuses on a case of resonance that has an unfavorable effect on the hydraulic circuit. The result of the thesis is the analytical relations for determination of self-excited and forced shapes of flow and pressure in the closed cylindrical area, for two selected variants of kinematic excitation. In the first variant, excitation is performed in the form of a sinus function. The second variant is expressed as a sawtooth function. A pulsation of the fluid caused by the movement of the body is described for the annulus. Further, in this area, the shapes of fluid pulsation are solved without external excitation.

The thesis deals with building and utilization of mechatronic models which are based on modeling of system of rigid and flexible bodies. Such models are then used for analysis of behavior of complex systems, for instance machine tools. The work is concentrated on analysis of self-excitation of a machine tool. The appearance of the self-excitation during the machining may be influenced by several methods described in the work. The evaluation of the appearance of the self-excitation is analyzed via so called lobe diagram. It is necessary to know transfer function describing the impact of acting forces on the deformation of the system (machine tool in this case) for compilation of the lobe diagram. The whole structure of the model shows compliant behavior which dramatically influences the transfer function thus the approach to the modeling of mechanical parts as flexible bodies is proposed. There are created models of modally reduced flexible bodies based on modified CAD models which have same modal properties as non-reduced FEM models up to the maximal excitation frequency. The reduced models have significantly lower number of degrees of freedom and it is possible to work with them in multi-body simulation tools and at the same time they contain the information about the deformations. The work utilizes Graig-Bamton method which is implemented to the ANSYS. The whole model is consequently built and analyzed in ADAMS. It is possible to export the linearized model of the system in form of state matrices which are used for writing of the transfer function. The conditions of stability of the machining process are then evaluated via the lobe diagram. The proposed thesis presents the modeling of mechatronic systems with stiff and rigid bodies. The approach may be used for analysis of machining tools as well as for development of advanced mechatronic systems with active damping, etc.