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1
Lim, Chin Lee. „Non-linear performance in flexible rotor system“. Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423004.
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2
Viana, Serra Villa Cristiano Thouverez Fabrice. „Dynamique non linéaire des rotors Applications numériques et expérimentales à un rotor flexible /“. [S.l.] : [s.n.], 2005. http://bibli.ec-lyon.fr/exl-doc/cvilla.pdf.
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3
Viana, Serra Villa Cristiano. „Dynamique non linéaire des rotors : Applications numériques et expérimentales à un rotor flexible“. Ecully, Ecole centrale de Lyon, 2005. http://bibli.ec-lyon.fr/exl-doc/cvilla.pdf.
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Cette thèse s'intéresse au comportement dynamique des machines tournantes comportant des organes tels que des roulements dont le fonctionnement est décrit par des lois non linéaires. Le premier objectif de ces travaux de recherche est de mettre en oeuvre des méthodes d'analyse non linéaire afin de résoudre les équations du mouvement de tels systèmes tournants. Le second objectif consiste à effectuer des études expérimentales sur un rotor flexible et d'effectuer des corrélations avec les modèles numériques associés. La modélisation des parties linéaires du système tournante est faite par la méthode des éléments finis. Concernant les roulements, nous présentons trois modèles permettant de prendre en compte leurs non-linéarités intrinsèques telles que le jeu radial et le contact de Hertz. Nous nous intéressons alors plus particulièrement à une modélisation où la cinématique des éléments roulants est considérée. Le type de solution non-linéaire recherchée est le régime permanentThis thesis deals with the dynamic behavior of rotating machinery containing the parts whose behavior is described by non linear laws. The first goal of this research is to implement methods of non linear analysis in order to solve the equations of motion of the system. Secondly, experimental studies are made with a test rig and the results are used to update a numeric model. The rotor is represented by a finite element model. To model the bearings, three models with different levels of complexity are presented, and a model where the kinematics of the rolling elements is adopted. The type of motion of interest is the steady state vibration, and to obtain this kind of solution it is advisable to use a frequential method like the Harmonic Balance Method Alternating Frequency Time (HBM AFT). This method can be implemented with an exact condensation strategy to reduce the computational time. The HBM AFT method is validated by comparing with a direct integration of a non linear Jeffcott rotor
4
Viitala, R. (Risto). „Dynamic radial bearing force measurement of flexible rotor“. Master's thesis, University of Oulu, 2018. http://urn.fi/URN:NBN:fi:oulu-201809062733.
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Dynamic characteristics of a paper machine roll have been widely investigated for decades. Vibration of the rolls decrease the paper quality and excites the structures of the paper machine. Therefore, vibration must be avoided and kept at its minimum. Vibration of a rotor develops periodic radial bearing forces, which are connected to the amplitude and the frequency of the vibration. Vibration based forces are unnecessary dynamic forces, which increase the bearing load in addition to unavoidable rotor mass and the external loads of the process. This experimental study presents the amplitudes of the dynamic bearing force caused by a vibrating rotor and enables further measurements and research about the correlation between the radial bearing force and e.g. acceleration data. During the research knowledge about the dynamic behavior of the rotor and developed forces can be increased. The improved knowledge leads to a lower bearing force level, which decreases the oversizing of the structures, enables the design of lighter and more cost-effective structures, extends the lifespan of the machine and improves the quality of the end product. The dynamic radial bearing force amplitudes of a paper machine roll are merely available through simulation models, since physical force sensors are not mounted on the paper machines. Typically, the monitoring of a paper machine is focused on the vibrations of the paper machine rolls, since it is more relevant for to the quality of the paper than the amplitudes of force. Vibration troubleshooting and monitoring tasks have typically been realized through the easy-installed accelerometer measurements. The force measurement of the paper machine roll can produce similar information about the behavior of the rotor and its vibrations as acceleration measurement in addition to the radial force amplitudes. However, utilization of force measurements in vibration monitoring was not found based on a literature survey. The radial bearing force measurement was accomplished by building a test rig and a measurement device for an industrial-size paper machine roll. The radial bearing forces were measured as close as possible to the action point of the load to produce reliable results. The results present the force measurement data, which were acquired with the calibrated and verified measurement device implemented during this study. The measured results revealed the forces affecting on both ends of the test roll. The data was analyzed with Fast Fourier Transform (FFT) to present the forces in the frequency domain and to investigate their harmonic components. The measured forces, which were divided into harmonic components, could be discovered and destabilizing excitations could be defined more efficiently. Based on the present study high harmonic components could be distinguished with the force measurement. The results were compared with two reference measurements, which utilize acceleration and position sensors. The results cannot be generalized, since the measuring results consider only the roll of this research. The roll, the bearings, the bearing support and the foundation form the rotating system, which is always individual. Parameters and excitations affecting to the behavior of the roll are different in every roll. However, the similar behavior can be assumed to be on other flexible rotors as well and those can be measured with similar methods as the present study. In further research additional knowledge about the behavior of the roll and correlations between force, position and acceleration can be achieved for both the scientific and practical engineering purposes with the dynamic bearing force measurement and a simultaneous acceleration or position measurementPaperikoneen telan värähtelyominaisuuksia on tutkittu laajasti jo vuosikymmeniä. Värähtely heikentää paperin laatua ja aiheuttaa herätettä paperikoneen rakenteisiin. Tästä johtuen värähtely yritetään pitää minimaalisena. Roottorin värähtely aiheuttaa jaksollisia laakerivoimia, jotka ovat yhteydessä värähtelyyn. Värähtelyn aiheuttamat voimat ovat ei-toivottuja dynaamisia voimia, jotka lisäävät laakerivoimia välttämättömän roottorimassan ja muiden prosessista aiheutuvien rasitusten lisäksi. Tämä kokeellinen tutkimus keskittyy värähtelevän roottorin aiheuttamiin dynaamisiin voimiin ja mahdollistaa myöhemmän mittaamisen ja korrelaatioiden tutkimisen laakerivoimien ja esimerkiksi kiihtyvyysmittauksen välillä. Tietoa roottorin dynaamisesta käyttäytymisestä ja syntyvistä voimista voidaan parantaa tällä tutkimuksella. Paperikoneen telan dynaamisten ominaisuuksien parempi tunteminen vähentää rakenteiden ylimitoitusta, mikä mahdollistaa rakenteiden suunnittelun kevyemmäksi ja halvemmaksi, lisää koneen käyttöikää ja parantaa lopputuotteen laatua. Telan värähtelyn aiheuttamia dynaamisia laakerinvoimia on saatavilla vain simuloimalla, mikä tarkoittaa, että fyysisiä voima-antureita ei ole asennettuina paperikoneissa. Yleensä paperikoneen anturointi keskittyy paperikoneen telojen värähtelyyn, sillä se on isompi tekijä paperin laaduntarkkailussa kuin voimamittaus. Värähtelymittaukseen perustuvaa vianetsintää ja prosessivalvontaa on tehty tyypillisesti helposti kiinnitettävillä kiihtyvyysantureilla. Voimamittaus pystyy tuottamaan saman informaation roottorin käyttäytymisestä ja sen värähtelystä kuin kiihtyvyysmittaus laakerivoimien lisäksi. Kuitenkaan, voimamittausta ei käytetä värähtelymittauksiin kirjallisuusselvityksen mukaan. Laakerivoimamittaus suoritetaan rakentamalla koepenkki sekä mittalaite teollisuudessa käytettävälle paperikoneen telalle. Laakerivoimat pyritään mittaamaan mahdollisimman läheltä voimanvaikutuspistettä, että saavutettaisiin mahdollisimman luotettava tulos. Mittatulokset saatiin kalibroidulla ja verifioidulla mittalaitteella, joka oli rakennettu tämän työn aikana. Mittaustulokset paljastivat telan laakereihin syntyvät voimat kummassakin päässä telaa. Tulokset analysoitiin käyttäen nopeaa Fourierin muunnosta (FFT), jotta voimat saatiin taajuustasoon harmonisten komponenttien tutkimiseksi. Mitatut voimat ja niiden amplitudit, jotka olivat esitettyinä harmonisina komponentteina, voitiin löytää ja telan värähtelyä aiheuttavat herätteet voitiin rajata tehokkaammin. Tämän tutkimuksen perusteella voitiin huomata, että korkeat harmoniset taajuudet voitiin havaita voimamittauksella. Tuloksia verrattiin kahteen referenssimittaukseen, jotka oli toteutettu kiihtyvyys- ja paikka-antureilla. Tuloksia ei voitu yleistää, sillä mittaustulokset koskevat vain tämän tutkimuksen telaa. Tela, laakerit, laakerin tuenta ja perusta muodostivat pyörivän systeemin, mikä on aina yksilöllinen. Parametrit ja herätteet, jotka vaikuttavat telan käyttäytymiseen muuttuvat joka telassa. Kuitenkin samanlaista käyttäytymistä voidaan olettaa olevan myös toisissa joustavissa roottoreissa ja ne voidaan mitata samalla tavalla kuin tässä tutkimuksessa. Myöhemmässä tutkimuksessa voidaan saavuttaa lisäarvoa ja korrelaatioita laakerivoiman, siirtymämittauksen ja kiihtyvyysmittauksen välillä tieteellisiin ja käytännön tarkoituksiin dynaamisella laakerivoimamittauksella
5
Baseer, M. A. „Control of vibration in a flexible rotor-bearing system“. Thesis, University of Bath, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254323.
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Clements, Shaun. „On line vibration of a flexible rotor/bearing system“. Thesis, University of Strathclyde, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302866.
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Landry, Céderick. „Dynamique de rotor d’une turbine renversée à moyeu flexible“. Mémoire, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/10597.
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Le mémoire de maîtrise présente la dynamique de rotor d’une microturbine à gaz à configuration renversée permettant l’intégration de pales en céramique. Cette configuration permet d’utiliser des pales de turbine complètement en céramique car elles sont retenues en compression de l’extérieur par un anneau en composite qui est en rotation. Par contre, la configuration renversée nécessite une nouvelle conception de moyeu de turbine. En effet, l’anneau en composite est loin de l'axe de rotation. Par conséquent, il se dilate beaucoup dus aux efforts centrifuges ce qui entraîne un grand déplacement des pales. L’idée est donc de faire un moyeu flexible qui vient suivre le déplacement des pales pour appliquer une pression en dessous de ceux-ci, afin de les tenir en place par friction.
La dynamique de rotor avec moyeu flexible est très peu documentée dans la littérature. Le projet de recherche consiste en la compréhension de la dynamique d’un moyeu flexible pour cibler les paramètres intervenant dans la vibration d’une turbine renversée. La recherche se fera via la conception d’un prototype permettant d’étudier l’effet de la flexibilité pour un concept donné. L’analyse de dynamique de rotor avec moyeu flexible est faite avec un modèle par éléments finis linéaire. Malgré le fait que des non-linéarités peuvent provenir des roulements à billes supportés par des films amortisseurs, un type de roulements couramment utilisé pour supporter des turbocompresseurs, il est démontré qu’un modèle linéarisé capte plutôt bien les tendances mesurées. Le but de ce projet est de déceler les paramètres problématiques d’un moyeu flexible et de découvrir les paramètres permettant une bonne dynamique.
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Lv, Peng. „Performance aérodynamique et structurelle du rotor flexible pour micro-drones“. Thesis, Toulouse, ISAE, 2014. http://www.theses.fr/2014ESAE0058/document.
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Les essais en environnement libre et en soufflerie ont été effectués pour étudier la performance propulsive et la déformation de pales de référence et de pales souples. La poussée et le couple ont été évalués par deux méthodes: une mesure directe par balance et une estimation indirecte par bilan de quantité de mouvement, les deux méthodes ayant leurs avantages et limitations respectifs. La méthode indirecte s’est construite sur l’acquisition de champs de vitesse obtenus par PIV et s’appuie sur une estimation de la pression par mise en œuvre de l’équation de Poisson. En vol stationnaire, les pales flexibles ne peuvent pas aider à l’amélioration du rendement en mode rotor (FM), à chargement faible, puisque la distribution de vrillage est sans doute assez éloignée de l’optimal de vol stationnaire. En vol avancé, le rendement propulsif des pales flexibles est la plupart du temps plus élevé que l’hélice rigide de référence en raison de la torsion bénéfique généré en rotation. Dans le cas des pales flexibles, la vitesse axiale se trouve être inférieure au cas rigide, à même station aval; ceci correspondant à la la déformation de vrillage négatif. Pour les deux pales, la différence de poussée entre celle déduite du champ PIV test 2et celle obtenue avec la balance est plus grande que la différence entre les valeurs déduites du champ PIV test 1 et de la mesure directe. La technique de mesure laser pour les déplacements(LDS) a été utilisée pour mesurer la déformation stationnaire des pales lors de leur rotation. Par analyse du nuage de points mesurés par la LDS, la flexion et la torsion de la lame en rotation ont été identifiées à l’aide des régressions multiplesThe wind tunnel tests were conducted to explore the performance difference caused by the potential twist deformation between baseline blades and flexible blades. The balance was built in SaBre wind tunnel for measuring the thrust and torque of blades. The BEMT predictions of blades with varied twist were also performed in hover and forward flight, respectively. In hover,flexible blades cannot help in improving the FM at light disk loading since the twist generated on flexible blades is probably beyond the ideal hover twist. In forward flight, the propulsive efficiency η of flexible blades is mostly higher than baseline blades due to the beneficial twist generated in rotation. A Particle Image Velocimetry (PIV) approach of loads determination was developed based on control volume method to obtain thrust and torque of small-scale proprotor,especially for off-optimum conditions. The pressure Poisson equation was implemented for the pressure estimation based on the PIV velocity data. The axial velocity of flexible blades is found to be lower than baseline blades on the same station at downstream. This corresponds to the lower inflow ratio distribution along flexible blade, which results from the negative twist deformation. For both baseline blades and flexible blades, the thrust differences between PIV test 2 and balance are larger when compared to the differences between PIV test 1 based on nearfield and balance. The Laser Displacement Sensor (LDS) technique was employed for measuring the stationary deformation of rotating flexible blades. By obtaining the LDS point cloud, the bending and torsion of the rotating blade were identified using the multiple regressions
9
Tasaltin, R. „Active vibration control strategies for a flexible rotor-bearing system“. Thesis, University of Bath, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303551.
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Perdikologos, Nikolaos Carleton University Dissertation Engineering Mechanical. „Dynamic analysis of flexible disc-rotor systems using component modes“. Ottawa, 1985.
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11
Preciado, Delgado E. „Mixed modal balancing of flexible rotors without trial runs“. Thesis, Cranfield University, 1998. http://dspace.lib.cranfield.ac.uk/handle/1826/10638.
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The subject of this thesis is about the balancing of large flexible rotors which exhibit
mixed modal characteristics. The objective of the research was to develop a balancing
procedure to determine correction masses without trial runs. This required the
determination of(a) the modal vibration vectors for each resonance, (b) the modal
damping ratios,(c) the mode shapes and(d) the equivalent mass of the rotor for each
mode. It was made clear from the beginning that trial runs are unavoidable either, when
the mode shapes cannot be determined using an analytical or numerical method, or when
there is dual vibration at normal operating speed, produced by the influence of higher
unbalanced modes, is too high to allow continuous operation of the machine. Therefore,
the scope of the project was limited to the possible determination of correction masses
without trial runs for the vibration modes included within the normal operating range.
Some studies about the minimisation or complete elimination of trial runs have been
published by several authors, but a literature search revealed no reports of systematic
application of these procedures to field balancing of large turbo generators. This
suggested that some practical difficulties had still to be overcome, opening the possibility
for further research on this area.
Analysis of the rotor response demonstrated the necessity of considering the angular
position of the transducers when registering the rotor vibration. It was shown that
measuring in a direction other than those of the principal axes of stiffness introduces
errors when determining the magnitude and phase of the correction masses. That is to
say, failing to consider the effects of the transducer angular position eliminates the
possibility of balancing the rotor without trial runs. This is the first time that this problem
has been recognised.
The procedure developed was verified using an experimental rotor rig. The successful
application of the procedure to the balancing of this rotor demonstrates that balancing
withouttrialrunsisnotonlyatheoreticalbutalsoapracticalpossibility. The dynamic
characteristics of the rotor rig, however, were some what limited and did not cover all the
possibilities considered during the project. Therefore, a more complete numerical
example was also successfully solved using the computer model of a rotor with
characteristics similar to those of a real turbine, and whose unbalanced distribution was
not initially known by this author.
12
Kalita, Karuna. „Integrating rotordynamic and electromagnetic dynamic models for flexible-rotor electrical machines“. Thesis, University of Nottingham, 2007. http://eprints.nottingham.ac.uk/13895/.
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The magnetic field within electrical machines causes an interaction between the electrical and mechanical dynamics of the system. In the simplest cases, when the rotor mean position is central in the stator, the interaction manifests itself mainly as a negative stiffness between the rotor and the stator. When the rotor mean position is offset relative to the stator, then components of force arise whose frequency in the stationary frame is twice the electrical frequency of the supply. For induction machines in particular, both the electrical system and the mechanical system may be quite complex dynamically in the sense that over the range of frequencies of interest, it is necessary to consider a number of degrees of freedom in both the electrical part of the model and the mechanical part. This work sets out a structured and formal approach to the preparation of such models. Each different combination of voltage and slip is examined separately. In each case, the first step is to compute the steady-state reference solution for machine currents as a function of time. Then, the electro-magnetic behaviour of the electrical machine is linearised around that reference solution. The result is a linear time-dependent model for the electromagnetic behaviour which is then easily coupled with a linear model for the mechanical dynamics. The mechanical dynamics are usually stationary. Floquet methods can then be applied to determine whether the system is stable and the response of the system to mechanical or electrical perturbations can be computed quickly. The analysis method is applied to a particular three-phase induction machine which has parallel paths integrated into its winding structure in the sense that each of the phases is split into a "Wheatstone-bridge" arrangement following. Currents passing diametrically through a phase in the vertical direction account for the main torque-producing components of stator field. Currents passing diametrically through the phase in the horizontal direction account for transverse forces. The parallel paths can be switched to open-circuit or closed-circuit without affecting the torque-producing function of the machine and all of the stator conductors contribute to torque-production.For a number of combinations of voltage and slip, the machine is stable irrespective of whether the parallel paths are open-circuit or not but the effective damping of the machine for synchronous vibration is shown to be much higher with the parallel paths in closed-circuit.
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Ghauri, Muhammad Khalid Khan. „Transient response of a flexible rotor system with asymmetry and contact“. Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335215.
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Abulrub, Abdul-Hadi G. „Modelling and control of contact in magnetic bearing/flexible rotor systems“. Thesis, University of Bath, 2006. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437436.
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Mykhaylyshyn, Volodymyr. „Application of Active Magnetic Force Actuator for Control of Flexible Rotor System Vibrations“. Cleveland State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=csu1322845232.
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Das, Manabendra. „Aeroelastic Analysis of Rotor Blades Using Three Dimensional Flexible Multibody Dynamic Analysis“. Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/195601.
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This study presents an approach based on the floating frame of reference method to model complex three-dimensional bodies in a multibody system. Unlike most of the formulations based on the floating frame of reference method, which assume small or moderate deformations, the present formulation allows large elastic deformations within each frame by using the co-rotational form of the updated Lagrangian description of motion. The implicit integration scheme is based on the Generalized-alpha method, and kinematic joints are invoked in the formulation through the coordinate partitioning method. The resulting numerical scheme permits the usage of relatively large time steps even though the flexible bodies may experience large elastic deformations. A triangular element, based on the first order shear deformable theory, has been developed specifically for folded plate and shell structures. The plate element does not suffer from either shear or aspect-ratio locking under transverse and membrane bending, respectively. A stiffened plate element has been developed that combines a shear deformable plate with a Timoshenko beam. A solid element, that utilized the isoparametric formulation along with incompatible modes, and one-dimensional elements are also included in the element library. The tools developed in the present work are then utilized for detailed rotorcraft applications. As opposed to the conventional approach of using beam elements to represent the rotor blade, the current approach focuses on detailed modeling of the blade using plate and solid elements. A quasi-steady model based on lifting line theory is utilized to compute the aerodynamic loads on the rotor blade in order to demonstrate the capabilities of the proposed tool to model rotorcraft aeroelasticity.
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Atepor, Lawrence. „Vibration analysis and intelligent control of flexible rotor systems using smart materials“. Thesis, University of Glasgow, 2009. http://theses.gla.ac.uk/593/.
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Flexible rotor-bearing system stability is a very important subject impacting the design, control, maintenance and operating safety. As the rotor bearing-system dynamic nonlinearities are significantly more prominent at higher rotating speeds, the demand for better performance through higher speeds has rendered the use of linear approaches for analysis both inadequate and ineffective. To address this need, it becomes important that nonlinear rotor-dynamic responses indicative of the causes of nonlinearity, along with the bifurcated dynamic states of instabilities, be fully studied. The objectives of this research are to study rotor-dynamic instabilities induced by mass unbalance and to use smart materials to stabilise the performance of the flexible rotor-system. A comprehensive mathematical model incorporating translational and rotational inertia, bending stiffness and gyroscopic moment is developed. The dynamic end conditions of the rotor comprising of the active bearing-induced axial force is modelled, the equations of motion are derived using Lagrange equations and the Rayleigh-Ritz method is used to study the basic phenomena on simple systems. In this thesis the axial force terms included in the equations of motion provide a means for axially directed harmonic force to be introduced into the system. The Method of Multiple Scales is applied to study the nonlinear equations obtained and their stabilities. The Dynamics 2 software is used to numerically explore the inception and progression of bifurcations suggestive of the changing rotor-dynamic state and impending instability. In the context of active control of flexible rotors, smart materials particularly SMAs and piezoelectric stack actuators are introduced. The application of shape memory alloy (SMA) elements integrated within glass epoxy composite plates and shells has resulted in the design of a novel smart bearing based on the principle of antagonistic action in this thesis. Previous work has shown that a single SMA/composite active bearing can be very effective in both altering the natural frequency of the fundamental whirl mode as well as the modal amplitude. The drawback with that design has been the disparity in the time constant between the relatively fast heating phase and the much slower cooling phase which is reliant on forced air, or some other form of cooling. This thesis presents a modified design which removes the aforementioned existing shortcomings. This form of design means that the cooling phase of one half, still using forced air, is significantly assisted by switching the other half into its heating phase, and vice versa, thereby equalising the time constants, and giving a faster push-pull load on the centrally located bearing; a loading which is termed ‘antagonistic’ in this present dissertation. The piezoelectric stack actuator provides an account of an investigation into possible dynamic interactions between two nonlinear systems, each possessing nonlinear characteristics in the frequency domain. Parametric excitations are deliberately introduced into a second flexible rotor system by means of a piezoelectric exciter to moderate the response of the pre-existing mass-unbalance vibration inherent to the rotor. The intended application area for this SMA/composite and piezoelectric technologies are in industrial rotor systems, in particular very high-speed plant, such as small light pumps, motor generators, and engines for aerospace and automotive application.
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Marais, Charl Henri. „High speed flexible rotor active magnetic bearing control / by Charl Henri Marais“. Thesis, North-West University, 2006. http://hdl.handle.net/10394/1084.
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The School of Electrical, Electronic and Computer Engineering at the North-West University is in the
process of establishing a knowledge base on Active Magnetic Bearings (AMBs). In support of this
initiative this project is aimed at characterising an in-house developed double radial heteropolar AMB
system.
Before characterising the AMB system the acoustic noise problem of the system had to be addressed and
reduced to an acceptable level. To reduce the acoustic noise of the system a noise analysis was done to
determine the source of the noise. The analysis revealed radiated noise from the electromagnets and
power amplifiers (PA) and conducted noise on the signals to and from the controller. The conducted noise
is reduced by using anti-aliasing (AAF) and anti-imaging filters (AIF) before and after the controller. The
effect of the radiated noise is reduced by synchronising the sampling of the sensor signals with the
switching of the PAS.
The characterisation of the AMB system starts with a Mass-Spring-Damper (MSD) simulation which is
a linear representation of the AMB system. This simulation is used to understand the basic principles of a
second order system and to compare its response to the nonlinear AMB simulation. The following step in
characterising the AMB system is to determine the effect of filters on the nonlinear AMB simulation and
to determine the simulation characteristics. These characteristics are compared to the MSD simulation
and the actual AMB system. The characteristics compared between the MSD and AMB simulations are
the static, second order and dynamic stiffness.
The actual AMB system was characterised before and after the AAF and AIF were implemented. This
provided the opportunity to determine the effects of the filters on the actual system and not just from
simulations. The characteristics measured on the actual AMB system include the static stiffness, dynamic
stiffness, rotor dynamics and system sensitivity. The stiffness characteristics of the actual AMB system
showed good correlation with the linear and nonlinear simulations. The measured results showed a
decrease in static stiffness and an increase in system sensitivity because of the AAF, AIF and controller
pole. It also showed that the effects of the filters can be reduced by moving the controller pole to a higher
frequency.
The characterisation of the double radial heteropolar AMB system provides a fundamental understanding
of the AMB performance aiding the AMB design process.Thesis (M. Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2006.
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Zutavern, Zachary Scott. „Identification of rotordynamic forces in a flexible rotor system using magnetic bearings“. [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1827.
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20
Krček, Aleš. „Simulace rozběhu Lavalova rotoru uloženého v nelineárních vazbách“. Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443768.
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The presented diploma thesis deals with simulation of Laval rotor supported by nonlinear bearings. The first part of thesis deals with research, which is focused on description of Laval rotor and motion equations for case of rigid and flexible rotor, also on description and modeling of hydrodynamic and magnetic bearing, which is considered in thesis. The second part of thesis deals with simulation of rotor for different approaches to modeling hydrodynamic and magnetic bearings. Using simulations performer in time domain, the dynamic behavior of Laval rotor is evaluated and compared. Simulations are performer in MATLAB.
21
Wang, Xiaoqiang. „The Influence of a Skewed Disk on a Flexible Rotating Shaft“. Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/31099.
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This thesis describes the experimental test results and computer simulation investigations which were conducted to verify the existing theory of skewed disk forced response predictions. The experimental tests were conducted on a horizontal flexible shaft rotor system supported in two hydrodynamic journal bearings. The computer simulations were conducted with a program that uses a matrix transfer method to get the desired solution. The agreement between experiment and simulation is very good for most skewed disk response characteristics. The influence of measurement errors and operation condition uncertainties are discussed.In the first part of this study, the dynamic behavior of experimental investigations focused on two different skewed disk designs which were mounted at midspan, 1/3 span and 2/3 span of the shaft. The two skewed disks were designed to allow a fine angle adjustment of the desired skew angle. The two designs are (a) the angle tiltable disk and (b) the couple unbalanced mass disk. The experimental results are shown to be close to the theoretical predictions of other authors.In the second part of this study, an existing computer program was used to simulate the experimental test rotor. The results give excellent qualitative agreement although there are some differences in quantitative analysis comparisons. The forced response characteristics of the computer simulation match the experimental results. It has been shown that by using the approximate linear skewed disk model, it is possible to get similar results to the experimental tests for similar disk skew conditions.Master of Science
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Balantrapu, Achuta Kishore Rama Krishna. „Identification of force coefficients in flexible rotor-bearing systems - enhancements and further validations“. Texas A&M University, 2004. http://hdl.handle.net/1969.1/2549.
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Rotor-bearing system characteristics, such as natural frequencies, mode shapes, stiffness and damping coefficients, are essential to diagnose and correct vibration problems during system operation. Of the above characteristics, accurate identification of bearing force parameters, i.e. stiffness and damping coefficients, is one of the most difficult to achieve. Field identification by imbalance response measurements is a simple and often reliable way to determine synchronous speed force coefficients.
An enhanced method to estimate bearing support force coefficients in flexible rotor-bearing systems is detailed. The estimation is carried out from measurements obtained near bearing locations from two linearly independent imbalance tests. An earlier approach assumed rotordynamic measurements at the bearing locations, which is very difficult to realize in practice. The enhanced method relaxes this constraint and develops the procedure to estimate bearing coefficients from measurements near the bearing locations.
An application of the method is presented for a test rotor mounted on two-lobe hydrodynamic bearings. Imbalance response measurements for various imbalance magnitudes are obtained near bearing locations and also at rotor mid-span. At shaft speeds around the bending critical speed, the displacements at the rotor mid-span are an order of magnitude larger than the shaft displacements at the bearing locations. The enhanced identification procedure renders satisfactory force coefficients in the rotational speed range between 1,000 rpm and 4,000 rpm. The amount of imbalance mass needed to conduct the tests and to obtain reliable shaft displacement measurements influences slightly the magnitude of the identified force coefficients. The effect of increasing the number of rotor sub-elements in the finite-element modeling of the shaft is noted. Sensitivity of the method and derived parameters to noise in the measurements is also quantified.
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Johnson, Bruce Graham. „Active control of a flexible, two-mass rotor : the use of complex notation“. Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/14915.
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Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1987.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.
Bibliography: leaves 528-536.
by Bruce Graham Johnson.
Sc.D.
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Ranft, Eugén Otto. „The development of a flexible rotor active magnetic bearing system / by Eugén O. Ranft“. Thesis, North-West University, 2005. http://hdl.handle.net/10394/892.
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The School of Electrical and Electronic Engineering at the North-West University is in the
process of developing an Active Magnetic Bearing (AMB) research laboratory. The aim is to
establish a knowledge base on AMBs in support of industries that make use of this
environmentally friendly technology. AMB technology is seen as one of the technology drivers
for the Pebble Bed Modular Reactor (PBMR) currently in development in South Africa and is
predicted to become largely conventional in this application.
In the process of developing an AMB laboratory some basic models are constructed to establish
infrastructure for research investigations. The aim of this project is to develop a flexible rotor
double radial AMB system. The system comprises a laminated heteropolar magnetic actuator,
eddy-current position sensors, switch-mode power amplifiers and a digital controller. Emphasis
is placed on stable suspension of a flexible rotor through the first three critical frequencies. This
project also caters for future work on high speed losses in AM6 systems.
A design process comprising aspects of modelling and analysis is developed, implemented and
verified for a flexible rotor AMB system. The design commences with a system specification
followed by an iterative process comprising electromagnetic design, detailed system modelling
and rotordynamic analysis, and is concluded with design implementation and verification.
The system design includes two interchangeable rotors; a flexible rotor for rotordynamic
analyses and a rigid rotor for high speed loss analyses. The flexible rotor system is specified to
experience the first three critical frequencies up to an operating speed of 10,000 rpm. The rigid
rotor maximum operating speed is specified as 30,000 rpm. Rotor stability at critical frequencies
places specific constraints on the equivalent stiffness and damping parameters of the AMB.
An iterative design process is then initiated by an analytical electromagnetic design of the radial
AMBs conducted in MathCAD® The magnetic actuator utilizes a 0.6 mm air gap and has a
maximum load capacity of 500 N. A force slew rate specification of 5x10~N /s is obtained from
the system's equivalent stiffness (500 N/mm) and damping (2.5 N.s/mm) parameters resulting in
a 3 kVA power amplifier requirement. These parameters are used in the detailed MATLAB®
modelling of the system. Stiffness and damping parameters as well as system dynamic
response are verified and used to design a flexible rotor. The magnetic bearing locations,
displacement sensor locations and rotordynamic response are verified using finite element
methods. The design of the rotor stands central to the iterative design process since it impacts
on the forces experienced by the AMBs as well as the critical frequencies of the AMB system.
The most important outcome of the iterative design process is a dimensioned electromagnetic
configuration and two rotor designs. The flexible rotor spans 500 mm and weighs 7.72 kg
whereas the rigid rotor has the same length and weighs 12.5 kg. A centre mass on the flexible
rotor lowers the first three critical frequencies to below the maximum operating speed.
A 3 kVA (300 V, 10 A) switch-mode, current controlled power amplifier (PA) is developed in-house
as part of the outcome of the study. The topology used is a two-quadrant controlled
H-bridge, switched at 100 kHz and controlled in current-mode. The design is thoroughly verified
through a process of prototyping and includes aspects of electromagnetic compatibility and
protection in terms of over-current and temperature. The PA exhibits a 6 kHz bandwidth and
linear characteristics and plays a critical role in the AMB system performance.
The AMB controller is realised with a dSPACE® real-time development tool (DS1104), located
inside a personal computer (PC). The rotational speed is monitored with an optical speed
sensor while the shaft is propelled via an air turbine unit.
Once constructed the actual AMB stiffness and damping parameters as well as its dynamic
response are obtained. Discrepancies between the analytically predicted, simulated and
experimentally obtained results are addressed and clarified. The sensitivity of the system to
parameter changes is obtained as a measure of marginal stability. The rotordynamic response
is characterised by measuring the rotor displacement at pre-defined locations as the rotor
traverses the critical frequencies. These results show good correlation with the predicted
rotordynamics.
This study emphasises the importance of extensive modelling and analyses in the design of
AMB systems to guarantee the required performance of the end product in terms of its dynamic
performance and stability. The most important outcome of this project is a working high speed
AMB model complete with integrated control. The system is versatile and allows for a variety of
investigations including advanced control investigations and high speed magnetic bearing loss
analyses. This project uniquely contributes to the research currently underway in the field of
AMBs in the School of Electrical and Electronic Engineering.Thesis (M. Ing. (Electrical and Electronic Engineering))--North-West University, Potchefstroom Campus, 2005.
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Chu, Fulei. „The vibration control of a flexible rotor by means of a squeeze-film damper“. Thesis, University of Southampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386603.
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Cheung, J. O. „Transient response to flexible rotor-bearing systems subjected to combined unbalance and ground excitations“. Thesis, Cranfield University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233345.
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Mu, Cheng. „Robust active vibration control of flexible rotor-bearing systems under steady and transient conditions“. Thesis, University of Bath, 1994. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387119.
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Junker, Stefan. „Technologien und Systemlösungen für die flexibel automatisierte Bestückung permanent erregter Läufer mit oberflächenmontierten Dauermagneten /“. Bamberg : Meisenbach, 2007. http://deposit.d-nb.de/cgi-bin/dokserv?id=2998555&prov=M&dok_var=1&dok_ext=htm.
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Al-Rady, Mohammad. „Experimental investigation of the effect of annular flow on the lateralvibration of a flexible rotor“. Thesis, Heriot-Watt University, 1992. http://hdl.handle.net/10399/1499.
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Mendoza, Hector. „Evaluation of the Effectiveness of an Active Magnetic Damper (AMD) in Damping Subsynchronous Vibrations in a Flexible Rotor“. Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/33887.
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Subsynchronous vibrations such as those caused by rotor instability represent one of the most harrowing scenarios of rotor vibration. They are related to a great diversity of destabilizing forces and some of them are not well understood yet. Therefore, special attention must be paid to this type of vibration. Active Magnetic Bearings (AMBs) monitor the position of the shaft and change the dynamics of the system accordingly to keep the rotor in a desired position, offering the possibility of being used as dampers for vibration control.
In the present work, a single-disk and a three-disk rotor were built to evaluate the effectiveness of an Active Magnetic Damper (AMD) in damping subsynchronous vibrations. An AMD was used to inject a signal simulating a subsynchronous vibration in the rotor, as another AMD was used to perform active control. Two locations of the AMD were considered for each rotor. For the single-disk rotor, experimental data was taken with the AMD located at three-quarters of the rotor-span and with the AMD located at midspan. For the three-disk rotor, experimental data was taken with the AMD located at a quarter-span and with the AMD at two-thirds of the rotor span.
An undamped critical speed and a forced response analysis were performed on the rotors in order to predict the dynamic characteristics of the rotors with and without the AMD.
It was demonstrated that an AMD is effective in damping subsynchronous vibrations. The addition of an AMD introduces damping and stiffness to the rotor-bearing system resulting in a change in the synchronous response and a consequent increase of the amplitude of vibrations at synchronous frequencies. This effect must be carefully considered when designing a system with an AMD.Master of Science
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Угнічев, Артем Сергійович, Артем Сергеевич Угничев, Artem Serhiiovych Uhnichev, Віталій Іович Симоновський, Виталий Иович Симоновский und Vitalii Iovych Symonovskyi. „Оптимизация процесса балансировки гибкого ротора с помощью симплекс-метода“. Thesis, Издательство СумГУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/8044.
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Guilbert, Bérengère. „Hybrid modular models for the dynamic study of high-speed thin -rimmed/-webbed gears“. Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI127/document.
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Ces travaux de thèse ont été réalisés grâce à une collaboration entre Safran Helicopter Engines (anciennement Turbomeca) et le Laboratoire de Mécanique des Contacts et des Structures (LaMCoS) de l’INSA de Lyon (UMR CNRS 5259). Les boîtes de transmission par engrenages des moteurs d’hélicoptères convoient la puissance mécanique du turbomoteur aux accessoires (pompes, démarreur) et au rotor. Leur conception dépend des nécessités des équipements embarqués, en particulier l’allègement pour réduire la consommation en carburant. Les engrenages haute vitesse de la transmission sont allégés grâce à des enlèvements de matière dans les corps sous la denture, les voiles-minces. Un modèle dynamique d’engrenages a été développé pendant ce projet de recherche. Son approche modulaire permet l’inclusion conjointe des sollicitations dues aux vibrations de l’engrenage et de la nouvelle flexibilité des voiles-minces. Il dérive d’un modèle à paramètres concentrés, comprenant des arbres en poutre, des paliers et carters sous forme de raideurs additionnelles et un élément d’engrenage rigide inclus par son nœud central. Hypothèse est faite que tous les contacts sont situés sur les lignes de contact du plan d’action. Ces lignes sont discrétisées selon des tranches-minces dans les dents et la déviation normale des cellules est recalculée à chaque pas de temps selon la déflexion de la denture. Le nouveau modèle remplace l’engrenage rigide par une modélisation EF du pignon et/ou de la roue condensée sur les nœuds de jante. Une interface lie les raideurs du plan d’action discrétisé aux éléments finis du corps d’engrenage. L’élément prend donc en compte à la fois les sollicitations de l’engrenage et le comportement statique et modal des corps flexibles en dynamique. Des comparaisons sont faites avec des données numériques et expérimentales. Elles attestent de la capacité du nouveau modèle à prédire le comportement dynamique des engrenages flexibles à hauts régimes de rotation. Ces résultats intègrent entre autres des données locales et globales en dynamique. Finalement, le modèle est utilisé sur les deux cas académiques validés pour visualiser les effets des corps flexibles plus en détails. Un premier focus sera fait sur la déflexion statique due aux charges d’engrènement et sur l’optimisation sur le fonctionnement dynamique possible. Puis, les impacts des sollicitations de l’engrènement sur le voile en rotation seront étudiés. Enfin, le pignon et la roue seront affinés, afin de visualiser l’optimisation massique possible et son impact sur la dynamique de l’engrenageThe research work presented in this manuscript was conducted in the Contact and Structural Mechanics Laboratory (LaMCoS) at INSA Lyon, in partnership with Safran Helicopter Engines (formerly-Turbomeca). In helicopters, the power from the turboshaft is transmitted to the rotor and the various accessories (pumps, starters etc…) via transmission gearboxes. In the context of high-speed, light-weight aeronautical applications, mechanical parts such as gears have to meet somehow contradictory design requirements in terms of reliability and mass reduction thus justifying precise dynamic simulations. The present work focuses on the definition of modular gear dynamic models, capable of integrating both the local phenomena associated with the instant contact conditions between the tooth flanks and the more global aspects related to shafts, bearings and particularly the contributions of light thin-rimmed /-webbed gear bodies. The proposed models rely on combinations of condensed sub-structures, lumped parameter and beam elements to simulate a pinion-gear pair, shafts, bearings and housing. Mesh elasticity is time-varying, possibly non-linear and is accounted for by Winkler foundations derived from a classic thin-slice model. The contact lines in the base plane are therefore discretised into elemental segments which are all attributed a mesh stiffness function and a normal deviation which are updated depending on the pinion and gear angular positions. The main originality in this PhD consists in inserting condensed finite elements models to simulate flexible gear bodies while keeping the simple and faster rigid-body approach for solid gears. To this end, a specific interface has been developed to connect the discretised tooth contact lines to the continuous finite element gear body models and avoid numerical spikes in the tooth load distributions for example. A number of comparisons with numerical and experimental results show that the proposed modelling is sound and can capture most of the quasi-static and dynamic behaviour of single stage reduction units with thin-webbed gears and/or pinions. The model is then applied to the analysis of academic and industrial gears with the objective of analysing the contributions of thin, flexible bodies. Results are presented which highlight the role of centrifugal effects and tooth shape modifications at high speeds. Finally, the possibility to further improve gear web design with regard to mass reduction is investigated and commented upon
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Simões, Ricardo Corrêa. „Controle Modal Ótimo de um Rotor Flexível Utilizando Atuadores Piezelétricos do Tipo Pilha“. Universidade Federal de Uberlândia, 2006. https://repositorio.ufu.br/handle/123456789/14671.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorThis work deals with active vibration control of flexible rotors. Vibratory control behavior of a horizontal rotor containing two disks and suported by bearings on its extremities was studies numericaly and experimentaly. Numerical simulations was perfomaded using Finite Element Method (FEM). The target control was to atenuate the vibration of first 4 bending modes by using of a Linear Quadratic Regualdor. A modal method was required to reduce the model size and make the model controllable. A state observer estimated the modal state coordenates necessary to model method. The control forces were applied over the structure by piezeletric stack actuators. These actuators were orthogonally arranged in control plane locatted in one of bearings bearings of the rotor. The experimental identification of stiffness of active bearings compoments and MEF model ajust was carrifully conducted. The sucsses of metholody was intrically related to this work part, that has allowed the accured calculation of the contol force. Experiments were carried out in a rotor test rig. Optimal modal Controller performance has been tested to various operation conditions and differents excitation forces, like rotor at rest, steady state rotation and transiente rotation. Numerical and experimental results attest the sucsses of control strategy and shows the potentiality of stack piezelectric actuators in the active vibration control to rotordynamics field.
Este trabalho trata do controle ativo de vibração de rotores flexíveis. Um rotor horizontal de dois discos apoiado em dois mancais em suas extremidades foi estudo no que tange o aspecto de controle, tanto no âmbito numérico como experimental. As simulações numéricas foram feitas empregando-se o Método dos Elementos Finitos (MEF). Um controlador ótimo do tipo Regulador Quadrático Linear foi utilizado para atenuar as vibrações dos 4 primeiros modos de flexão do rotor. Empregou-se um método modal para reduzir o tamanho modelo e torná-lo então controlável. O uso de tal método gerou a necessidade de se estimar os estados modais através de um observador de estados. O tipo de atuador escolhido para aplicar a força de controle sobre a estrutura foi um atuador piezelétrico do tipo pilha (piezeletric stack actuator). Os atuadores foram dispostos ortogonalmente num plano de controle localizado num dos mancais do rotor. A determinação experimental da rigidez dos elementos que componham o mancal ativo, onde se localizava os atuadores, e o ajuste destes valores no MEF foi etapa conduzida cuidadosa. O sucesso da metodologia de controle se atribui em grande parte a esta etapa que permitiu um cálculo preciso da força de controle. As simulações foram feitas numa bancada experimental devidamente instrumentada para os testes. A performance do controlador modal ótimo foi testada para diversas condições de funcionamento do rotor em questão e diferentes fontes excitação. A saber: Rotor em repouso, rotor em regime de rotação permanente, rotor em regime de rotação transiente. Os resultados obtidos, tanto numéricos como experimentais, mostram o sucesso da metodologia empregada e as potencialidades do uso do tipo de atuador aqui empregado para o campo do controle ativo de vibração de rotores.
Doutor em Engenharia Mecânica
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Tremel, Jan [Verfasser], Jörg [Akademischer Betreuer] Franke, Jörg [Gutachter] Franke und Technische Universität Hamburg-Harburg Thorsten [Gutachter] Schüppstuhl. „Flexible Systems for Permanent Magnet Assembly and Magnetic Rotor Measurement / Jan Tremel ; Gutachter: Jörg Franke; Thorsten Schüppstuhl, Technische Universität Hamburg-Harburg ; Betreuer: Jörg Franke“. Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2016. http://d-nb.info/1176190903/34.
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Kiesel, Theo [Verfasser], Steffen [Akademischer Betreuer] Marburg, Steffen [Gutachter] Marburg und Rosa Sergio [Gutachter] de. „Flexible Multi-Body Simulation of a Complex Rotor System Using 3D Solid Finite Elements / Theo Kiesel ; Gutachter: Steffen Marburg, Sergio de Rosa ; Betreuer: Steffen Marburg“. München : Universitätsbibliothek der TU München, 2017. http://d-nb.info/1149252324/34.
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Burbano, Christian Eligio Rodríguez. „Diagnóstico de falhas em máquinas rotativas“. Universidade Federal de Uberlândia, 2005. https://repositorio.ufu.br/handle/123456789/14818.
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The dynamic behavior of a cracked shaft was studied both in run-up and run-down transient motion. A mathematical model of the shaft was developed , and experimental tests were performed in order to validate the model. A experimental testing rig was conducted, containing an horizontal flexible rotor with a rigid disc in the mid point between the bearings.
Experimental and theo retical responses were compared for both cracked and uncracked shafts. All tests were done for several acceleration rates and unbalance conditions.
For the theoretical study of dynamic response of the cracked shaft, the stiffness matrix for a cracked element was deduced, using the modified crack Model of Mayes. The rotor
model was obtained by using the finite elements method. The equations of motion were integrated in the time domain by using Newmark method to obtain the transient response.
Comparing theoretical and experimental results validated the model. For this purpose, the modified Mayes model was used to represent the dynamic response of the crached shaft.
Further simulations were conducted to study the influence of acceleration rates, unbalance amplitude /orientation and crack severity on the response of a cracked shaft, running on transient mo tion.Neste trabalho apresenta -se um estudo do comportamento dinâmico de um rotor com trinca no regime transiente, tanto na parada como na partida. Foi desenvolvido um modelo matemático -computacional de um rotor com trinca e foram também realizados testes experimentais com vistas à validação do modelo. Para o estudo experimental, foi construida uma bancada constituida por um rotor flexível horizontal com um disco rígido montado na posição média do comprimento. A resposta experimental do rotor foi comparada para os casos com e sem trinca. Para tanto, foram usados dois eixos, um com trinca e, o outro, sem trinca. Os testes experimentais foram feitos para diferentes taxas de aceleração e condições de desbalanceamento. Para o estudo teórico da resposta dinâmica do rotor com trinca, foi determinada a matriz de flexibilidade para um elemento com falha, uma vez aplicado o modelo de trinca de Mayes modificado. O modelo do rotor foi obtido através do método dos elementos finitos, e para o cálculo da resposta dinâmica no regime transiente foi utilizado o método de integração numérica de Newmark. O modelo foi validado mediante a comparação dos resultados teóricos com os experimentais, tendo sido mostrado que o Modelo de Mayes modificado representa adequadamente o comportamento dinâmico de um rotor com trinca. Foram feitas simulações para estudar a influência das taxas de aceleração, da intensidade do desbalanceamento presente no sistema e da severidade da trinca sobre o comportamento do rotor com trinca no regime transiente.
Mestre em Engenharia Mecânica
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Redmond, Irvin. „Vibration reduction of flexible rotors“. Thesis, University of Strathclyde, 1985. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21476.
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A novel method of flexible-rotor vibration control, using an active contactless angular electromagnetic actuator is presented. A theoretical comparison of radial and angular damping is performed. Three different performance indices are defined and used to determine controller optimum damping/location data for different shaft systems. The controller settings are determined for two main cases: i) such that only one damping value is allowed throughout the entire shaft speed range (passive or fixed-gain active control), ii) the damping value is controlled as a function of rotor speed (adaptive control). The parameter optimisation, made possible by the creation of a simple but efficient numerical technique employed in conjunction with the transfer matrix method, is restricted to considering a speed range covering the first three rigid-bearing critical speeds for a uniform shaft supported by a variety of bearings. However, the approach is sufficiently general to allow the study of any required speed range. It is shown that for both the radial and angular dampers when mounted at the bearings, there is a definite support stiffness value above which the angular damper is the more efficient, but below which the opposite is true. When the conditions for 'fixed-points' are satisfied, then a simple on-off control strategy can be used effectively employing either type of controller. Angular damping is shown also to be an effective means of suppressing 'oil-whirl' type instability. The theoretical work is supported by experimental investigations on a laboratory rig which is representative of a general flexible rotor system. An electromagnetic controller is mounted at one bearing and the reduction of shaft unbalance response and bearing forces recorded for various conditions. Significant reductions in system synchronous response are observed at running speeds close to the first critical speed when electromagnetic stiffness and/or damping is employed. When electromagnetic damping is introduced, non-synchronous vibration components, resulting from shaft asymmetries, are also eliminated. The combined theoretical and experimental studies show angular control to be a viable alternative means of reducing flexible rotor vibrations.
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Defoy, Benjamin. „Investigation on the control of supercritical centrifugal compressors supported by active magnetic bearings : Toward a new control strategy?“ Thesis, Lyon, INSA, 2012. http://www.theses.fr/2012ISAL0140/document.
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Le comportement dynamique des turbomachines industrielles doit respecter des critères émis par les normes internationales et les utilisateurs. Les rotors flexibles sont sensibles à la distribution de balourd, et sont soumis aux excitations aérodynamiques de leur environnement. Usuellement, les contrôleurs utilisés peinent à délivrer le niveau d’exigence demandé, par conséquent les propriétés mécaniques des paliers magnétiques sont fortement dépendantes de celles des rotors. L’objectif de ce mémoire est d’analyser le comportement dynamique des compresseurs centrifuges afin de proposer une stratégie de contrôle innovante. D’abord, chaque palier est considéré comme une entité a part entière en couplant ses deux axes d’action. Le comportement dynamique du rotor est exprimé dans le repère polaire. Par ailleurs, la logique floue, qui utilise un modèle de pensée proche du raisonnement humain, applique des actions correctives en fonction du comportement dynamique global du rotor. Ainsi, l’utilisation couplée de ces deux approches créé une synergie permettant d’agir sur le système de manière ciblée. Le contrôleur dissipe l’énergie cinétique du rotor lors du franchissement de vitesses critiques afin d’atténuer la réponse au balourd, ou augmente la raideur du palier lors de vibrations transitoires ou asynchrones afin de réduire la trajectoire du rotor. Le faible amortissement structurel du rotor le rend sensible au phénomène de « spillover » (l’énergie de contrôle affecte les modes de fréquence élevée). Or, la logique floue ne peut pas gérer ce phénomène. Ainsi, un contrôleur PID sous-jacent est utilisé pour maîtriser la stabilité des modes hautes fréquences. Au final, le contrôleur flou polaire permet d’obtenir des marges de performances entre les capacités de cet asservissement et le cahier des charges. Ces marges sont utilisées pour trois objectifs : le respect des spécifications, l’amélioration du comportement subsynchrone, et enfin la simplification et la standardisation du contrôleur sous-jacent nommé ici SPID. Ce contrôleur est tel que ses caractéristiques, dans la plage de fréquence utile, sont indépendantes du rotor pour une application donnée. Enfin, la stratégie développée est évaluée avec des simulations numériques et des essais expérimentaux. D’abord, le modèle numérique est validé, puis le contrôleur est appliqué à un banc d’essais académique. Le comportement est stable et robuste. Il présente des performances supérieures au PID augmenté fourni avec le banc, que ce soit pour la réponse au balourd, ou pour la réponse à des excitations subsynchrones. Finalement, la démarche est appliquée à un compresseur industriel. Les simulations montrent que le comportement est proche de celui exigé pour des machines sur paliers classiques. L’optimisation de l’approche et l’automatisation de la conception pourraient conduire à la standardisation des paliers magnétiques actifsThe dynamic behaviour of large turbomachinery should satisfy stringent requirements dictated by international standards and final users. Their flexible rotor is sensitive to the unbalance distribution and subjected to particular excitations coming from the industrial process. Usually, the performance margins between the requirements and the classical controller capabilities are small. Consequently, the magnetic bearing characteristics depend on the rotor geometry. Designing such controllers is difficult and time consuming. The objective of this thesis is to investigate the dynamic behaviour of supercritical centrifugal compressors in order to propose a new control strategy. First, each bearing is considered as one entity by coupling its two axes of action. The introduction of polar quantities permits a better observation of the rotor dynamic behaviour. In addition, by using logic close to human being reasoning, the fuzzy logic modulates the action forces as a function of the global dynamic behaviour. The coupling of the two approaches is an efficient way to apply targeted corrective actions. This controller attenuates the unbalance vibration when crossing critical speeds by applying damping forces, or increases the stiffness during transient or asynchronous excitations in order to limit the maximum displacement reached. As their structural damping is low, flexible rotors are very sensitive to spillover effect, which cannot be managed by fuzzy controllers. Consequently, an underlying PID is necessary. This hand-synthesized controller has high frequency characteristics tuned in order to ensure stability and robustness for each rotor. Compared to a classical approach, the polar fuzzy controller enables to increase the performance margins. These margins are used to fulfil three objectives: the achievement of standards requirements, the improvement of the subsynchronous behaviour, and the simplification and the standardization of the PID controller that we called SPID. This SPID is designed for a given application, such that the bearing characteristics on the operating frequency range are always the same. The control strategy is assessed numerically and experimentally. First, the numerical model is validated with experimental tests. Then, the controller developed is applied to an academic test rig. The controller is stable and robust. It exhibits performance superior to the augmented PID supplied with the test rig for both unbalance response and response to subsynchronous excitations. Finally, the control of an industrial compressor is assessed numerically. The results obtained are close to the standards requirements used for classical bearings. The optimization of the approach and the utilization of an automatic tuning algorithm for high frequency characteristics could lead to the standardization of Active Magnetic Bearings
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Duran-Venegas, Eduardo. „Modélisation et optimisation d'un rotor à pales flexibles“. Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0195.
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Historiquement, les rotors ont été développés pour la propulsion et la génération d’énergie. Pendant des années, grands efforts de recherche ont été fournis pour les éoliennes et les hélicoptères. Or, des nouvelles applications comme les drones nécessitent une recherche plus approfondie. La flexibilité du rotor et les conditions de fonctionnement particulières constituent un défi pour l'optimisation de leur design. Dans cette thèse, on propose un modèle fluide-structure qui prend en compte la flexibilité des pales dans des conditions de fonctionnement non-conventionnelles. Le modèle est suffisamment simple et robuste pour la réalisation d'études paramétriques extensives. Il comprend des modèles pour le sillage et la structure flexible du rotor. Deux modèles du sillage sont considérés: un modèle classique de Joukowski et un modèle généralisé. Dans le modèle classique, deux vortex sont émis par pale, l’un sur la pointe et l’autre sur l’axe. Dans le modèle généralisé, le tourbillon axial est décalé par rapport au centre. Une analyse de stabilité est réalisée pour les solutions dérivées avec le modèle classique. La nature convective/absolue de l’instabilité est étudiée pour différentes conditions de fonctionnement. Les solutions stationnaires du sillage sont utilisées pour calculer le champ de vitesse induit dans le plan rotor. Ainsi, à partir de la loi de Kutta-Joukowski et de la théorie des éléments de pale (BET), on peux déterminer les charges aérodynamiques exercés sur les pales. Le couplage du rotor avec son sillage est alors implémenté pour une configuration rigide. Finalement, la flexibilité de la pale est prise en compte à l’aide d’un modèle de poutre élastiqueRotors have been historically developed for harvesting and propulsion. For wind turbines and helicopters, decades of research have been done to optimize their design. For recent applications, such as drones, no such a research effort has been made. The high flexibility of the rotor and the different operational conditions still constitute challenging issues for their design. In this work, a coupled fluid-structure model is proposed, taking into account the flexibility of the blades in non-conventional operational conditions.The model is sufficiently simple and robust to permit extensive parameter studies. It includes a model for the wake, a model for the flexible rotor structure and the coupling. Two different wake models are considered: a classical Joukowski model, where two vortices are emitted per blade, one at the tip and one at the axis, and a generalized Joukowski model where the axial vortex is replaced by a hub vortex emitted away from the center. A stability analysis of the solutions derived with the classical Joukowski model is performed. The convective/absolute nature of the instability is analysed for various operational conditions.Stationary wake solutions are used to calculate the flow in the rotor plane. Kutta-Joukowski law and Blade Element Theory are applied to obtain the aerodynamic loads exerted on the blades. The full coupling of the rotor with its wake is first implemented for a rigid configuration. Coupled solutions are obtained for different rotors and compared to experimental and numerical data published in the literature. Finally, blade flexibility is considered using a rod model for the blade
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TOBON, BERNAL ROSENDO. „Equilibrage modal de rotors flexibles“. Paris, ENSAM, 1989. http://www.theses.fr/1989ENAM0014.
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Les rotors des machines tournantes presentent d'inevitables petits defauts d'excentricite dus aux imperfections de fabrication et a celles qui se produisent en cours d'exploitation. Ces defauts se traduisent par des forces tournantes qui peuvent causer des vibrations importantes, notamment aux vitesses critiques. L'equilibrage consiste a disposer sur certains plans du rotor des masses correctives, telles que les amplitudes de vibration de flexion soient reduites. Dans l'industrie, on utilise la methode des coefficients d'influence. Les coefficients d'influence se determinent experimentalement; lorsque (n) balourds correcteurs sont utilises, (n+1) arrets sont necessaires. Pour un groupe-turbo-alternateur de grande puissance le cout afferent a ces arrets est important. L'objectif est donc de definir une methode qui permet de ramener le nombre d'arrets de (n+1) a 2. Les phases principales de l'etude sont les suivants: 1) identification des valeurs et des vecteurs propres en deca de la vitesse maximale; 2) calcul des vecteurs propres a partir d'un modele obtenu par discretisation en elements finis; 3) ajustement des vecteurs propres calcules et determination de la fonction de transfert; 4) evaluation de la matrice des coefficients d'influence pour les vitesses d'equilibrage choisis. L'etude est effectuee en utilisant une machine tournante dont le rotor est flexible et guide par 6 paliers; la longueur de son rotor est egale a 1681 mm; 5 vitesses critiques se manifestent en deca de la vitesse maximale qui est de 420 tr/min. La methode converge pour le calcul des coefficients d'influence associes aux deux premieres vitesses critiques et pour certains capteurs. Des problemes specifiques sont etudies: 1) influence des defauts de forme et triboelectrique des pistes de mesurage; 2) influence des fleches initiales; 3) repetabilite et linearite des comportements
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Jayasuriya, Arachige Tilak A. „Dynamics of unbalanced rotors on rigid and flexible bearings“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0016/MQ48062.pdf.
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Lee, An Sung. „An experimental investigation of a noncontacting flexibly mounted rotor mechanical face seal“. Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/16019.
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Lusty, Christopher. „Rotor vibration reduction and control via flexibly-mounted internal-stator magnetic bearings“. Thesis, University of Bath, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.707570.
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Consideration has been given to the question of reducing and controlling vibration occurring in active rotor systems. The subject is of importance due to the widespread use of rotors within many engineering applications, coupled with the fact that one of the most problematic issues faced by designers of rotor systems is that of vibration. Furthermore, it is identified that improvements in the ability to handle vibration in high speed rotor systems will open up new opportunities for novel machine design and associated new capabilities. An overview of the history of rotor dynamics as a field is provided, highlighting both fundamental early work on the topic, as well as a range of research done with specific application to rotor vibration control. A novel design of an active rotor-vibration-reduction system is then proposed, consisting of a hollow rotor coupled to a exible internal secondary shaft via magnetic bearings. The unique features and benefits of this design are outlined, together with some numerical modelling of the vibration behaviour of such a system. The project required the design and fabrication of a bespoke test rig, and details of this process and the resulting rig are discussed. Special attention is given to the design of the magnetic bearings of the system, which employ a soft magnetic composite material and a novel, internalstator, homopolar geometry. The test rig was run, and two different control strategies for the magnetic bearings were explored for the purposes of achieving vibration reduction - one a traditional PID method, and the other a model-based H-infinity technique. A range of results describing the behaviour of the system under each of these control systems - as well as in the uncontrolled state - is presented. It is seen that the H-infinity controller can deliver substantial vibration reduction performance, and thereby the capability of the novel system topology for its designed purpose is proved.
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Karajani, Pirro. „Équilibrage modal de rotors flexibles : application à une machine“. Compiègne, 1995. http://www.theses.fr/1995COMPD795.
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Le rotor d'une machine tournante est affecté par des balourds inconnus qui engendrent des forces tournantes responsables de vibrations. La relation entre les balourds et les vibrations s'exprime par les coefficients d'influence. Leur détermination s'effectue par une procédure expérimentale sous réserve d'un comportement suffisamment linéaire et répétable. L'étude montre que ces coefficients peuvent être déterminés à l'aide d'un modèle du rotor, soit directement par les réponses aux balourds de ce modèle, soit à partir de ses caractéristiques modales (pulsations propres, modes propres à droite et à gauche). La qualité des résultats est observée par la comparaison de l'équilibrage d'un rotor obtenu, soit par voie entièrement expérimentale, soit par utilisation des résultats issus de la modélisation. Ce modèle ne peut être exploité que si son recalage est réalisé avec une précision suffisante. La méthode de recalage retenue s'appuie sur les matrices de sensibilité qui relient les caractéristiques modales du rotor et de son modèle à des grandeurs choisies : ce sont ici les matrices impédances identifiant les liaisons du rotor au sol qui sont ajustées après un premier recalage du modèle sur les pulsations et modes propres du rotor en état libre-libre. Si les écarts entre coefficients d'influence du rotor et du modèle ne sont pas nuls après recalage, des corrections complémentaires peuvent être apportées en tenant compte des caractéristiques modales expérimentales et en admettant l'identité des balourds modaux calcules et expérimentaux. La démarche mise en œuvre sur un rotor simple montre la faisabilité de la méthode.
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Hanish, Giuma Ramadan. „Investigation of the influence coefficient method for balancing of flexible rotors systems“. Thesis, Northumbria University, 2005. http://nrl.northumbria.ac.uk/74/.
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Several sophisticated procedures for balancing flexible rotors have been developed during the past two decades. For a variety of reasons, none of these methods has gained general acceptance by practicing balancing engineers. Some of these balancing techniques require a great deal of expertise from the operator. This thesis is dedicated to the research of flexible rotor balancing techniques, and aims to apply some advanced techniques to the field of high-speed rotor balancing. Significant progress in balancing methods for flexible rotors can be achieved by the improvement and optimization of existing balancing techniques. Experimental tests were conducted to demonstrate the ability of the influence coefficient method to achieve precise balance of flexible rotors. Various practical aspects of flexible- rotor balancing were investigated. Tests were made on a laboratory quality test rig having a 3.6 m long rotor representing a High Pressure Turbine (H.P.T) (10.1 kg)(43.767 cm), a Low Pressure Turbine (L.P.T) (43.922 kg) (113.698 cm) and a Generator Rotor (G. Rotor) (71.611kg) (146.413 cm) and covering a speed range up to 6000 rpm. A specific data acquisition system has been developed for use in a high-speed rotor balance facility. Special measurement requirements for this facility include order-tracked vibration measurements and phase angle data. The data acquisition system utilizes dual high-speed computer systems to share the tasks of measurement data processing, and results display. A study of balancing errors is systematically discussed in detail from the view point of increasing the balancing precision. The methods for controlling and reducing these errors are also discussed. Both the qualitative and quantitative analyses of balancing errors are performed as the guide to reduce the error and improve the balancing quality. The thesis also presents the theoretical background and the techniques necessary to the procedure to balance the flexible rotor. A trim balancing method was developed to expand the implementation of flexible rotor balancing. A computer program has been written which generates influence coefficient from measured motions and goes on to predict the correction mass. The vibration has been measured at several locations and speeds and the results have been used to (a) ensure that the vibration levels were not excessive as the rotor speed increased and (b) to calculate the balance correction weights using the traditional influence coefficient method and a least squares influence coefficient method. The procedure developed was verified using an experimental rotor rig. The successful application of the procedure to the balancing of this rotor demonstrates that balancing using Singular Value Decomposition, QR Factorization, and QR Factorization combined with SVD and new trim balancing method is not only a theoretical but also a practical possibility. The Moore-Penrose generalized inverse has been employed to solve the problem. The dynamic characteristics of the rotor rig, however, were somewhat limited and did not cover all the possibilities considered during the project. Therefore, a more complete numerical example was also successfully solved using the computer model of a rotor with characteristics similar to those of a real turbine by using a finite element software package called ANSYS.
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Wileman, James Michael. „The rotordynamic coefficients of mechanical face seals having two flexibly-mounted rotors“. Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/17241.
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Malhis, Mohamed Der Hagopian Johan. „Contrôle actif modal flou des rotors flexibles par plan d'action piézoélectrique“. Villeurbanne : Doc'INSA, 2004. http://docinsa.insa-lyon.fr/these/pont.php?id=malhis.
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Malhis, Mohamed. „Contrôle actif modal flou des rotors flexibles par plan d'action piézoélectrique“. Lyon, INSA, 2002. http://theses.insa-lyon.fr/publication/2002ISAL0098/these.pdf.
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Les travaux de ce mémoire contribuent à l'étude du contrôle actif des rotors flexibles en transitoire de vitesse. Ils proposent un Contrôle Modal Flou (C. M. F. ) dont la commande est basée sur le retour d'état modal de la structure et appliquée par un plan d'action piézoélectrique. Dans un premier temps, il s'agit de valider le C. M. F. Via une application à une structure représentant un rotor à l'arrêt. La structure choisie est une poutre dont le comportement dynamique est contrôlé par un plan d'action constitué de deux vérins piézoélectriques orthogonaux. Des contrôleurs optimaux de type Linéaire Quadratique Gaussien (L. Q. G. ) sont mis en place et pris pour référence pour valider la stratégie utilisant des C. M. F. L'application est réalisée en deux étapes. La première concerne le contrôle de la poutre dans une de ses directions transversales. Les résultats des simulations et des expérimentations sont en bon accord et montrent que le contrôle proposé est efficace et robuste. La seconde concerne l'extension de la méthode aux deux directions transverses. La faisabilité du contrôle d'une poutre flexible par un plan d'actionneurs piézoélectriques a donc été montrée. Dans un second temps, l'application du C. M. F. Au contrôle du comportement dynamique d'un rotor flexible en régime transitoire a été réalisée par l'intermédiaire d'un palier actif piézoélectrique. Cette stratégie est utilisée pour maîtriser les premiers modes du système. La robustesse du contrôle proposé permet de s'affranchir des non-linéarités du comportement dynamique du rotor. En particulier celles dues à l'évolution de la base modale en fonction de la vitesse de rotation et celles liées aux incertitudes du modèle sont absorbées. Le résultat des simulations montrent que ce contrôle est efficace : la réjection des perturbations est rapide et l'amortissement observé sur la réponse au balourd au passage des vitesses critiques est importantThis memory contributes to the study of the active control of the transient behaviour of flexible rotors. They propose a Fuzzy Modal Control (F. M. C) based on the feed-back of modal state of the structure and applied by an active plan composed of two piezoelectric pushers. First, the concept F. M. C. Is validated via an application a beam whose dynamic behaviour controlled by an action plan composed of two piezoelectric pushers. Optimal controllers of Linear Quadratic Gaussian type (L. Q. G. ) are set up and are taken for reference to validate the strategy using of controllers F. M. C. The application is carried out in two phases. The first relates to the control of the beam in one of its transverse directions is realised. The results of simulations and the experiments are in agreement and have a good effectiveness of the proposed controllers. The second relates to the extension of the method in two transverse directions. The feasibility of the control of a flexible beam according to two directions by a plan of piezoelectric actuators was shown. Secondly, we are interested more particularly in the application of the F. M. C. To control the transient dynamic behaviour of a flexible rotor subjected to external disturbances. The control force is applied in an action plan by means of an active bearing equipped with two piezoelectric pushers. The F. M. C. Is used to control the first modes of the system. The results of simulations show that this control is effective, the rejection of the disturbances is fast and the damping observed on the response to the unbalance with the passage of the critical speeds is significant. The robustness of control proposed absorbs the non linearity of the dynamic behaviour of the rotor in particular those which are due to evolution of its modal base according to its speed of rotation and those related to uncertainties in the model of the rotor/actuators
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Dufour, Régis. „Influence d'un couple axial sur le comportement dynamique des rotors flexibles“. Lyon 1, 1985. http://www.theses.fr/1985LYO19011.
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Dans le domaine de la conception de machines tournantes, l'étude de leur comportement vibratoire tient une place importante. A certianes vitesses de rotation, qualifiées alors de critiques, le système résonne et admet des vibrations de flexion de fortes amplitudes. Ces vitesses critiques peuvent évoluer en fonction des sollicitations extérieures, dont la plus évidente pour un rotor est le couple de torsion indiut par l'opposition du couple moteur et du couple résistant. D'après la bibliographie existante, l'influence d'un couple axial de torsion sur le comportement dynamique en flexion est de deux ordres : si le couple est constant, elle appartient à la famille des effets secondaires de la poutre en flexion ; si le couple est alternatif, l'arbre est le siège de zones d'instabilité de fréquences différentes de celles du couple d'excitation, et vibre avec de grandes amplitudes transversales. Pour étudier ces deux effets, on élabore un dispositif expérimental, non tournant, et on aborde plusieurs méthodes de résolution. L'apport de ce travail paraît le suivant : une méthode approchée qui facilite la compréhension des phénomènes, une analyse des modes par la méthode des éléments finis pour un couple constant, une recherche expérimentale mettant en évidence l'influence du couple constant et permettant l'observation de différents types d'instabilité lorsque le couple admet une composante aleternative
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Thomazi, Cleber Caetano. „Contribuição ao controle passivo de rotores flexíveis suportados por mancais de filme fluido através de elastômeros“. Universidade Federal de Uberlândia, 2013. https://repositorio.ufu.br/handle/123456789/14735.
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Fundação de Amparo a Pesquisa do Estado de Minas GeraisDynamic analyses of a flexible rotor supported by fluid film radial bearings on elastomeric suspension are performed using the Finite Element Method. The response to the unbalance and the stability behavior are obtained for different types of damping devices configuration and viscoelastic materials. The stiffness and damping coefficients of the hydrodynamic bearings are evaluated through the Short Bearing Theory. The properties of the elastomers, as a function of the frequency at a given temperature, are obtained from tests conducted in the Laboratory of Mechanical Systems of the School of Mechanical Engineering in the Federal University of Uberlândia. Dissipative elastomeric devices have strong influence on the dynamic behavior of the rotor. It is observed that with the suitable choice of the damper, the amplitude of the unbalance response may be reduced. The threshold speed of stability is increased with the use of elastomeric dampers for the most analyzed cases.
Análises dinâmicas de um rotor flexível apoiado por mancais radiais de filme fluido montados em uma suspensão elastomérica são realizadas utilizando o Método dos Elementos Finitos. A resposta ao desbalanceamento e o comportamento da estabilidade são obtidos para várias configurações de dispositivos amortecedores e para diferentes materiais viscoelásticos. Os coeficientes de rigidez e de amortecimento dos mancais hidrodinâmicos são obtidos através da Teoria de Mancais Curtos. As propriedades dos materiais viscoelásticos, determinadas em função da frequência a uma dada temperatura, são obtidas através de ensaios conduzidos no Laboratório de Sistemas Mecânicos da Faculadade de Engenharia Mecânica da Universidade Federal de Uberlândia. Os dispositivos dissipativos elastoméricos possuem forte influência no comportamento dinâmico do rotor. Observa-se que, com a escolha adequada da configuração do amortecedor, a amplitude da resposta ao desbalanceamento pode ser reduzida. A velocidade limite de estabilidade é aumentada com o emprego dos amortecedores elastoméricos para a maioria dos casos analisados.
Doutor em Engenharia Mecânica