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1
Walker, Ryan. "Localising imbalance faults in rotating machinery." Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/8606.
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This thesis presents a novel method of locating imbalance faults in rotating machinery through the study of bearing nonlinearities. Localisation in this work is presented as determining which discs/segments of a complex machine are affected with an imbalance fault. The novel method enables accurate localisation to be achieved using a single accelerometer, and is valid for both sub and super-critical machine operations in the presence of misalignment and rub faults. The development of the novel system for imbalance localisation has been driven by the desire for improved maintenance procedures, along with the increased requirement for Integrated Vehicle Health Management (IVHM) systems for rotating machinery in industry. Imbalance faults are of particular interest to aircraft engine manufacturers such as Rolls Royce plc, where such faults still result in undesired downtime of machinery. Existing methods of imbalance localisation have yet to see widespread implementation in IVHM and Engine Health Monitoring (EHM) systems, providing the motivation for undertaking this project. The imbalance localisation system described has been developed primarily for a lab-based Machine Fault Simulator (MFS), with validation and verification performed on two additional test rigs. Physics based simulations have been used in order to develop and validate the system. An Artificial Neural Network (ANN) has been applied for the purposes of reasoning, using nonlinear features in the frequency domain originating from bearing nonlinearities. The system has been widely tested in a range of situations, including in the presence of misalignment and rub faults and on a full scale aircraft engine model. The novel system for imbalance localisation has been used as the basis for a methodology aimed at localising common faults in future IVHM systems, with the aim of communicating the results and findings of this research for the benefit of future research. The works contained herein therefore contribute to scientific knowledge in the field of IVHM for rotating machinery.
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Gubran, Ahmed. "Vibration diagnosis of blades of rotating machines." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/vibration-diagnosis-of-blades-of-rotating-machines(40f1d466-b393-42f6-a65a-e16801f06920).html.
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Rotating blades are considered to be the one of the most common cause of failures in rotating machinery. Blade failure modes normally occur as a result of cracks due to unexpected operating conditions, which are normally caused by accidents of foreign objects damage, high cycle fatigue, blade rubbing, blade root looseness, and degradation from erosion and corrosion. Thus, detection of blade faults has an important role in reducing blade related failures and allowing repairs to be scheduled for the machinery. This in turn will lead to reduction in maintenance costs and thus raise productivity and safety aspects of operation. To maintain vital components of rotating machines, such as blades, shafts, bearings and gear boxes, at optimal levels, detection of failures in such components is important, because this will prevent any serious damage that could affect performance. This research study involves laboratory tests on a small rig with a bladed disc rotor that applied vibration measurements and analysis for blade fault detection. Three measurements: shaft torsional vibration, on-bearing vibration (OBV) and on-casing vibration (OCV), are used. A small test rig of a single stage bladed disc holding 8-blades was designed and manufactured, to carry out this research study to assess the usefulness and capability of each vibration technique in detection of incipient defects within machine blades. A series of tests was conducted on a test rig for three different cases of blade health conditions: (a) healthy blade(s) with mistuned effects, (b) blade root looseness and (c) cracks in a blade on two different blade sizes (long and short blades) in order to discover changes in blades' dynamic behaviour during the machine running-up operation. The data were collected using the three measurements during machine run-up and then recorded. The measured vibration data were analysed by computing the blades' resonance at different engine orders (EOs) related to the blade(s) resonance frequencies and their higher harmonics, to understand the blade(s) dynamics behaviour for the cases of healthy and faulty blade(s). Data have been further processed using a polar plot presentation method which provides clear results that can be used for monitoring blade integrity. To validate the obtained experimental results, a simplified mathematical model was also developed. Finally, a comparative study between three methods was undertaken to understand the relative advantages and limitations in the blade heath monitoring.
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Elnady, Maged Elsaid. "On-shaft vibration measurement using a MEMS accelerometer for faults diagnosis in rotating machines." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/onshaft-vibration-measurement-using-a-mems-accelerometer-for-faults-diagnosis-in-rotating-machines(cf9b9848-972d-49ff-a6b0-97bef1ad0e93).html.
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The healthy condition of a rotating machine leads to safe and cheap operation of almost all industrial facilities and mechanical systems. To achieve such a goal, vibration-based condition monitoring has proved to be a well-accepted technique that detects incipient fault symptoms. The conventional way of On-Bearing Vibration Measurement (OBVM) captures symptoms of different faults, however, it requires a relatively expensive setup, an additional space for the auxiliary devices and cabling in addition to an experienced analyst. On-Shaft Vibration Measurement (OSVM) is an emerging method proposed to offer more reliable Faults Diagnosis (FD) tools with less number of sensors, minimal processing time and lower system and maintenance costs. The advancement in sensor and wireless communications technologies enables attaching a MEMS accelerometer with a miniaturised wireless data acquisition unit directly to the rotor without altering the machine dynamics. In this study, OSVM is analysed during constant speed and run-up operations of a test rig. The observations showed response modulation, hence, a Finite Element (FE) analysis has been carried out to help interpret the experimental observations. The FE analysis confirmed that the modulation is due to the rotary motion of the on-shaft sensor. A demodulation method has been developed to solve this problem. The FD capability of OSVM has been compared to that of OBVM using conventional analysis where the former provided more efficient diagnosis with less number of sensors. To incorporate more features, a method has been developed to diagnose faults based on Principal Component Analysis and Nearest Neighbour classifier. Furthermore, the method is enhanced using Linear Discriminant Analysis to do the diagnosis without the need for a classifier. Another faults diagnosis method has been developed that ensures the generalisation of extracted faults features from OSVM data of a specific machine to similar machines mounted on different foundations.
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Nembhard, Adrian. "On-bearing vibration response integration for condition monitoring of rotating machinery." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/onbearing-vibration-response-integration-for-condition-monitoring-of-rotating-machinery(f713f156-11f3-4e10-846e-0b9b709f0ff9).html.
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Vibration-based fault diagnosis (FD) with a simple spectrum can be complex, especially when considering FD of rotating machinery with multiple bearings like a multi-stage turbine. Various studies have sought to better interpret fault spectra, but the process remains equivocal. Consequently, it has been accepted that the simple spectra requires support from additional techniques, such as orbit analysis. But even orbit analysis can be inconclusive. Though promising, attempts at developing viable methods that rival the failure coverage of spectrum analysis without gaining computational complexity remain protracted. Interestingly, few researchers have developed FD methods for transient machine operation, however, these have proven to be involved. Current practices limit vibration data to a single machine, which usually requires a large unique data history. However, if sharing of data between similar machines with different foundations was possible, the need for unique histories would be mitigated. From readily available works, this has not been encountered. Therefore, a simple but robust vibration-based approach is warranted. In light of this, a novel on-bearing vibration response integration approach for condition monitoring of shaft-related faults irrespective of speed and foundation type is proposed in the present study. Vibration data are acquired at different speeds for: a baseline, unbalance, bow, crack, looseness, misalignment, and rub conditions on three laboratory rigs with dynamically different foundations, namely: rigid, flexible support 1 (FS1) and flexible support 2 (FS2). Testing is done on the rigid rig set up first, then FS1, and afterwards FS2. Common vibration features are computed from the measured data to be input to the proposed approach for further processing. First, the proposed approach is developed through its application to a machine at a steady speed in a novel Single-speed FD technique which exploits a single vibration sensor per bearing and fusion of features from different bearings for FD. Initially, vibration features are supplemented with bearing temperature readings with improved classification compared to vibration features alone. However, it is observed that temperature readings are insensitive to faults on the FS1 and FS2 rigs, when compared to vibration features, which are standardised for consistent classification on the different rigs tested. Thus, temperature is not included as a final feature. The observed fault classifications on the different rigs at different speeds with the standardised vibration features are encouraging. Thereafter, a novel Unified Multi-speed FD technique that is based on the initial proposed approach and which works by fusion of vibration features from different bearings at different speeds in a single analysis step for FD is proposed. Experiments on the different rigs repeatedly show the novel Multi-speed technique to be suitable for transient machine operation. Then, a novel generic Multi-foundation Technique (also based on the proposed approach) that allows sharing of vibration data of a wide range of fault conditions between two similarly configured machines with similar speed operation but different foundations is implemented to further mitigate data requirements in the FD process. Observations made with the rigs during steady and transient speed tests show this technique is applicable in situations where data history is available on one machine but lacking on the other. Comparison of experimental results with results obtained from theoretical simulations indicates the approach is consistent. Thus, the proposed approach has the potential for practical considerations.
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Obaid, Ramzy R. "Detection of rotating mechanical asymmetries in small induction machines." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/13527.
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D'Elia, Gianluca <1980>. "Fault detection in rotating machines by vibration signal processing techniques." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/952/.
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Machines with moving parts give rise to vibrations and consequently noise. The setting up and
the status of each machine yield to a peculiar vibration signature. Therefore, a change in the
vibration signature, due to a change in the machine state, can be used to detect incipient
defects before they become critical. This is the goal of condition monitoring, in which the
informations obtained from a machine signature are used in order to detect faults at an early
stage. There are a large number of signal processing techniques that can be used in order to
extract interesting information from a measured vibration signal.
This study seeks to detect rotating machine defects using a range of techniques including
synchronous time averaging, Hilbert transform-based demodulation, continuous wavelet
transform, Wigner-Ville distribution and spectral correlation density function. The detection
and the diagnostic capability of these techniques are discussed and compared on the basis of
experimental results concerning gear tooth faults, i.e. fatigue crack at the tooth root and tooth
spalls of different sizes, as well as assembly faults in diesel engine. Moreover, the sensitivity
to fault severity is assessed by the application of these signal processing techniques to gear
tooth faults of different sizes.
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Johnson, David Ewen. "Use of noise for the detection of gear faults in rotating machinery." Thesis, University of the West of England, Bristol, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358312.
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Carlson, David K. "Artificicial [i.e. Artificial] neural networks and their applications in diagnostics of incipient faults in rotating machinery." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/28000.
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Wang, Xian Bo. "A novel fault detection and diagnosis framework for rotating machinery using advanced signal processing techniques and ensemble extreme learning machines." Thesis, University of Macau, 2018. http://umaclib3.umac.mo/record=b3951596.
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Martínek, Marek. "Tvorba SW pro generování signálu simulující závady rotačních systémů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-442837.
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This diploma thesis deals with the design and creation of an algorithm for generating simulated signal data from a vibration diagnostics device. The first part is focused on theoretical acquaintance with vibration diagnostics and characteristics of individual defects of rotary machines. The next part deals with the possibilities of mathematical and kinematic simulations using a computer software. The main part of this work is dedicated to design and creation of software for generating simulated signal data. In the last part, the principle of simulation of specific defects of rotary machines is clearly demonstrated.
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Ainapure, Abhijeet Narhar. "Application and Performance Enhancement of Intelligent Cross-Domain Fault Diagnosis in Rotating Machinery." University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1623164772153736.
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Malik, Naveed ur Rehman. "Modelling, Analysis, and Control Aspects of a Rotating Power Electronic Brushless Doubly-Fed Induction Generator." Doctoral thesis, KTH, Elektrisk energiomvandling, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-174349.
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This thesis deals with the modeling, analysis and control of a novel brushlessgenerator for wind power application. The generator is named as rotatingpower electronic brushless doubly-fed induction machine/generator (RPEBDFIM/G). A great advantage of the RPE-BDFIG is that the slip power recoveryis realized in a brushless manner. This is achieved by introducing an additionalmachine termed as exciter together with the rotating power electronicconverters, which are mounted on the shaft of a DFIG. It is shown that theexciter recovers the slip power in a mechanical manner, and delivers it backto the grid. As a result, slip rings and carbon brushes can be eliminated,increasing the robustness of the system, and reducing the maintenance costsand down-time of the turbine. To begin with, the dynamic model of the RPE-BDFIG is developed andanalyzed. Using the dynamic model, the working principle of the generatoris understood and its operation explained. The analysis is carried out atspeeds, ±20% around the synchronous speed of the generator. Moreover, thedynamics of the generator due to external load-torque disturbances are investigated.Additionally, the steady-state model is also derived and analyzed forthe machine, when operating in motor mode. As a next step, the closed-loop control of the generator is considered indetail. The power and speed control of the two machines of the generator andthe dc-link voltage control is designed using internal model control (IMC)principles. It is found that it is possible to maintain the stability of thegenerator against load-torque disturbances from the turbine and the exciter,at the same time maintain a constant dc-link voltage of the rotor converter.The closed-loop control is also implemented and the operation of the generatorwith the control theory is confirmed through experiments.In the third part of the thesis, the impact of grid faults on the behaviourof the generator is investigated. The operation of the generator and its responseis studied during symmetrical and unsymmetrical faults. An approachto successful ride through of the symmetrical faults is presented, using passiveresistive network (PRN). Moreover, in order to limit the electrical and mechanicaloscillations in the generator during unsymmetrical faults, the dualvector control (DVC) is implemented. It is found that DVC to a certain extentcan be used to safeguard the converter against large oscillations in rotorcurrents. Finally, for completeness of the thesis, a preliminary physical design ofthe rotating power electronic converter has been done in a finite elementsoftware called ANSYS. The thermal footprint and the cooling capability,with estimates of the heatsink and fan sizes, are presented. Besides, another variant of a rotating electronic induction machine whichis based on the Lindmark concept and operating in a single-fed mode is also investigated. It’s steady-state model is developed and verified through experiments.QC 20151006
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Menexiadis, Dimitri. "Conception d'un système expert d'aide au diagnostic pour les machines tournantes." Valenciennes, 1988. https://ged.uphf.fr/nuxeo/site/esupversions/04ba5d72-dc25-461d-8efd-ab79aeeefb8f.
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Kass, Souhayb. "Diagnostic vibratoire autonome des roulements." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI103.
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Le monde de l’industrie et des transports dispose de machines et d’installations de plus en plus performantes et complexes. Ils ne peuvent être exempts de perturbations et de défaillances, influant sur la qualité du produit, pouvant provoquer l’arrêt immédiat d’une machine et porter atteinte au bon fonctionnement d’un système de production entier. Le diagnostic de ces machines, s’appuie essentiellement sur la surveillance de symptômes liés à différentes conditions de dégradation. Ces symptômes peuvent être tirés de diverses sources d’information, parmi lesquelles l’analyse vibratoire et acoustique occupe une place prépondérante. Aujourd'hui, de nombreuses techniques efficaces sont bien établies, ancrées sur des outils puissants offerts notamment par la théorie des processus cyclostationnaires. La complexité de ces outils exige un expert pour les utiliser et les interpréter. La présence continue d’un expert est difficilement réalisable et couteuse. Des indicateurs d’état de machines tournantes existent dans la littérature mais ils sont conçus sous l'hypothèse de conditions de fonctionnement parfaites. Ces travaux restent limités, dispersés et généralement non soutenus par des cadres théoriques. Le principal objectif de cette thèse est de réduire le recours à l'intervention humaine en proposant des stratégies pour concevoir deux indicateurs optimaux qui résument l'information de diagnostic en une valeur scalaire. Ces stratégies sont élaborées en distinguant deux familles dans le diagnostic : le cas où les informations sur les défauts sont connues et celle où elles sont inconnues. Ces indicateurs sont destinés à être utilisés dans le cadre d'un processus de diagnostic autonome, sans nécessiter d’intervention humaine, à l’aide des tests d’hypothèses statistiques. La capacité de ces indicateurs est validée sur des données réelles et comparée avec d’autres indicateurs de la littérature en termes de performance de détectionThe industrial and transportation sectors require more and more efficient and complex machines and installations increasing the risk of failure and disruption. This can lead to the immediate shutdown of a machine and disrupts the proper functioning of the entire production system. The diagnosis of industrial machines is essentially based on the monitoring of symptoms related to different degradation conditions. These symptoms can be derived from various sources of information, including vibration and acoustic signals. Nowadays, many effective techniques are well established, based on powerful tools offered by the theory of cyclostationary processes. The complexity of these tools requires an expert to use them and to interpret the results based on his/her experience. The continuous presence of the expert is expensive and difficult to achieve in practice. Condition indicators for rotating machines exist in the literature but they are conceived under the assumption of perfect operating conditions. They are limited, dispersed and generally not supported by theoretical frameworks. The main objective of this thesis is to reduce the use of human intervention by proposing strategies to design two optimal indicators that summarize diagnostic information into a scalar value. A distinction is made between two families in diagnosis: the case where prior information on the faults is known and the case where it is unknown. These indicators are designed to be used in an autonomous process without requiring human intervention, using statistical hypothesis tests. The capacity of these indicators is validated on real data and compared with other indicators from the literature in terms of detection performance
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Edwards, S. "Fault diagnosis of rotating machinery." Thesis, Swansea University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636771.
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In this thesis, topics of importance to the fault diagnosis of rotating machinery in the power generation industry have been addressed, including a review of the relevant literature and an overview of the associated rotordynamics modelling and analysis techniques. For faults involving rotor-stator interaction it has been shown that the inclusion of torsion in mathematical models used for rotor-stator contract analyses can have a significant influence on the dynamic behaviour of the system. A 3 degrees-of-freedom model based on the Jeffcott rotor was developed and, for physically realistic systems, it was shown that very different results were obtained when including torsion, compared to when torsion was neglected, as has generally been the case in the past. An identification method for estimating both the excitation and flexible support parameters of a rotor-bearings-foundations system has been presented. Excitation due to both mass unbalance and a bent rotor were included in the analysis, which has been verified both in simulation and experimentally. The method has great practical potential, since it allows balancing to be performed using data obtained from just a single run-up or run-down, which has obvious benefits for field balancing. Using this single-shot balancing technique in experiment, vibration levels were successfully reduced by as much as 92% of their original levels. A bent rotor has been accurately identified in both simulation and experiment. It was also shown that including bend identification in those cases where only unbalance forcing was present in no way detracted from the accuracy of the estimated unbalance or foundation parameters. The identification of the flexible foundation parameters was generally successful, with measured and estimated parameters matching very closely in most cases. The identification method was tested for a wide range of conditions and proved suitably robust to changes in the system configuration, noisy data and modelling error.
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Silva, Bruna Tavares Vieira da. "Bancada para análise de vibração: análise de falhas em máquinas rotativas." Universidade de Taubaté, 2012. http://www.bdtd.unitau.br/tedesimplificado/tde_busca/arquivo.php?codArquivo=572.
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Elevados níveis de vibração podem levar um equipamento à fadiga, e consequente quebra, podendo causar perdas de produção, problemas de fornecimento de material ou de serviço.
Este trabalho desenvolveu um sistema para acionamento, aquisição e análise de uma bancada de ensaio de vibração em máquinas rotativas. O sistema proposto é composto por uma bancada com um motor fixo a uma plataforma, cujo eixo está acoplado a um rotor que pode sofrer desbalanceamento, através de inserção de massas. A rotação do eixo do motor é mensurada por um sensor indutivo, a vibração no mancal é monitorada por um acelerômetro. Para controle de acionamento e aquisição de dados foi utilizado o software LabVIEW. Esta bancada foi desenvolvida com a finalidade de estudar o comportamento dinâmico do rotor que está apoiado em mancais de rolamento. A estrutura montada permite simulação de falhas. Neste trabalho foi proposto o desbalanceamento de massa em um único plano, que é classificado como desbalanceamento estático. Este tipo de simulação foi escolhido também, visto que o rotor só possui um plano para desbalanceamento. Foram
realizados experimentos que possibilitaram a detecção das falhas através do nível de vibração medido pelo acelerômetro e através da frequência do sinal de vibração foi comprovado que a amplitude significativa do espectro ocorre na frequência de
rotação do equipamento, quando se trata de desbalanceamento. A bancada foi desenvolvida para ser utilizada no Laboratório de Vibrações Mecânicas da Universidade de Taubaté, porém as técnicas desenvolvidas podem ter aplicabilidade no ramo industrial, principalmente em manutenção preditiva.High levels of vibration equipment can lead to fatigue and consequent breakage, may cause production losses, problems of supply of equipment or service. This study developed a system for triggering, acquisition and analysis of a bench test vibration in rotating machines. The proposed system consists of a bench with a motor fixed to a platform whose shaft is coupled to a rotor imbalance can suffer through insertion of mass. The rotation of the motor shaft is measured by an inductive sensor, vibration in the bearing is monitored by an accelerometer. To drive control and data acquisition software was used LabVIEW. This bench was developed in order to study the dynamic behavior of the rotor that is supported by ball bearings. The assembled structure allows fault simulation. This work proposes the unbalance mass in a single plane, which is classified as static unbalance. Such simulation was also chosen since the rotor has only one plan for unbalance. Experiments were performed which allowed the detection of faults through the vibration level measured by the accelerometer and by the frequency of the vibration signal has been proven that the amplitude of the spectrum of significant vibration occurs in the rotation frequency of the machine when it comes to unbalance. The bench has been developed for use in Mechanical Vibration Laboratory at the University of Taubate, but the techniques developed may have applicability in the industrial sector, especially in predictive maintenance.
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Ferrando, Chacon Juan Luis. "Fault detection in rotating machinery using acoustic emission." Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/11510.
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Rotating machinery is a critical asset of industrial plants worldwide. Bearings and gearboxes are two of the most common components found in rotating machinery of industrial plants. The malfunction of bearings and gearboxes lead the machine to fail and often these failures occur catastrophically leading to personnel injuries. Therefore it is of high importance to identify the deterioration at an early stage. Among the techniques applied to detect damage in rotating machinery, acoustic emission has been a prevalent field of research for its potential to detect defects at an earlier stage than other more established techniques such as vibration analysis and oil analysis. However, to reliably detect the fault at an early stage de-noising techniques often must be applied to reduce the AE noise generated by neighbouring components and normal component operation. For this purpose a novel signal processing algorithm has been developed combining Wavelet Packets as a pre-processor, Hilbert Transform, Autocorrelation function and Fast Fourier transform. The combination of these techniques allows identification of g repetitive patterns in the AE signal that are attributable to bearing and gear damage. The enhancement for early stage defect detection in bearings and gears provided by this method is beneficial in planning maintenance in advance, reducing machinery down-time and consequently reducing the costs associated with bearing breakdown. The effectiveness of the proposed method has been investigated experimentally using seeded and naturally developed defects in gears and bearings. In addition, research into the optimal Wavelet Packet node that offers the best de-noising results has been performed showing that the 250-750 kHz band gives the best SNR results. The detection of shaft angular misalignment using Acoustic Emission has been investigated and compared with acceleration spectra. The results obtained show enhancements of AE in detection shaft angular misalignment over vibration analysis in SNR and stability with varying operational conditions.
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Halligan, Gary. "Fault detection and prediction with application to rotating machinery." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2009. http://scholarsmine.mst.edu/thesis/pdf/Halligan_09007dcc80708356.pdf.
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Thesis (M.S.)--Missouri University of Science and Technology, 2009.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed November 25, 2009) Includes bibliographical references.
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Ipurale, Andrew. "Condition monitoring and fault detection of inverter-fed rotating machinery." Master's thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/25278.
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Condition monitoring of rotating machinery is crucial in industry. It can prevent long term outages that can prove costly, prevent injury to machine operators, and lower product quality. Induction motors, often described as the workhorse of industry, are popular in industry because of their robustness, efficiency and the need for low maintenance. They are, however, prone to faults when used improperly or under strenuous conditions. Gearboxes are also an important component in industry, used to transmit motion and force by means of successively engaging teeth. They too are prone to damage and can disrupt industrial processes if failure is unplanned for. Reciprocating compressors are widely used in the petroleum and the petrochemical industry. Their complex structure, and operation under poor conditions makes them prone to faults, making condition monitoring necessary to prevent accidents, and for maintenance decision-making and cost minimization. Various techniques have been extensively investigated and found to be reliable tools for the identification of faults in these machines. This thesis, however, sets out to establish a single non-invasive tool that can be used to identify the faults on all these machines. Literature on condition monitoring of induction motors, gearboxes, and reciprocating compressors is extensively reviewed. The time, frequency, and time-frequency domain techniques that are used in this thesis are also discussed. Statistical indicators were used in the time domain, the Fourier Transform in the frequency domain, and Wavelet Transforms in the time-frequency domain. Vibration and current, which are two of the most popular parameters for fault detection, were considered. The test rig equipment that is used to carry to the experiments, which comprised a modified Machine Fault Simulator -Magnum (MFS-MG), is presented and discussed. The fault detection strategies rely on the presence of a fault signature. The test rig that was used allows for the simulation of individual or multiple concurrent faults to the test machinery. The experiments were carried out under steady-state and transient conditions with the faults in the machines isolated, and then with multiple faults implemented concurrently. The results of the fault detection strategies are analysed, and conclusions are drawn based on the performances of these tools in the detection of the faults in the machinery.
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Lee, Sun Ung. "Dynamics of high-speed rotating machines." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326078.
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Houlston, Paul Robert. "Active vibration control of rotating machines." Thesis, University of Nottingham, 2007. http://eprints.nottingham.ac.uk/10275/.
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Second order matrix equations arise in the description of real dynamical systems. Traditional modal control approaches utilise the eigenvectors of the undamped system to diagonalise the system matrices. Any remaining off-diagonal terms in the modal damping matrix are discarded. A regrettable automatic consequence of this action is the destruction of any notion of the skew-symmetry in the damping. The methods presented in this thesis use the `Lancaster Augmented Matrices' (LAMs) allowing state space representations of the second order systems. `Structure preserving transformations' (SPTs) are used to manipulate the system matrices whilst preserving the structure within the LAMs. Utilisation of the SPTs permits the diagonalisation of the system mass, damping and stiffness matrices for non-classically damped systems. Thus a modal control method is presented in this thesis which exploits this diagonalisation. The method introduces independent modal control in which a separate modal controller is designed in modal space for each individual mode or pair of modes. The modal displacements and velocities for the diagonalised systems are extracted from the physical quantities using first order SPT-based filters. Similarly the first order filters are used to translate the modal force into the physical domain. Derivation of the SPT-filters is presented together with a method by which one exploits the non-uniqueness of the diagonalising filters such that initially unstable filters are stabilised. In the context of active control of rotating machines, standard optimal controller methods enable a trade-off to be made between (weighted) mean-square vibrations and (weighted) mean-square control forces, or in the case of a machines controlled using magnetic bearings the currents injected into the magnetic bearings. One shortcoming of such controllers for magnetic bearings is that no concern is devoted to the voltages required. In practice, the voltage available imposes a strict limitation on the maximum possible rate of change of control force (force slew rate). This thesis presents a method which removes the aforementioned existing shortcomings of traditional optimal control. Case studies of realistic rotor systems are presented to illustrate the modal control and control force rate penalisation methods. The system damping matrices of the case studies contain skew-symmetric components due to gyroscopic forces typical of rotating machines. The SPT-based modal control method is used to decouple the non-classically damped equations of motion into n single degree of freedom systems. Optimal modal controllers are designed independently in the modal space such that the modal state, modal forces and modal force rates are weighted as required. The SPT-based modal control method is shown to yield superior results to the conventional notion of independent modal space control according to reasonable assessment.
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Mahdi, Hassan Hamoodi. "Vibrational modal analysis of rotating machines." Thesis, University of Hertfordshire, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303391.
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Cheang, Tak Son. "Inter-turn faults of three-phase induction machines." Thesis, University of Macau, 1997. http://umaclib3.umac.mo/record=b1445597.
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Lowes, Suzanne. "A comparative study between condition monitoring techniques for rotating machinery." Thesis, University of Birmingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325615.
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Firla, Marcin. "Automatic signal processing for wind turbine condition monitoring. Time-frequency cropping, kinematic association, and all-sideband demodulation." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAT006/document.
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Cette thèse propose trois méthodes de traitement du signal orientées vers la surveillance d’état et le diagnostic. Les techniques proposées sont surtout adaptées pour la surveillance d’état, effectuée à la base de vibrations, des machines tournantes qui fonctionnent dans des conditions d’opération non-stationnaires comme par exemple les éoliennes mais elles ne sont pas limitées à un tel usage. Toutes les méthodes proposées sont des algorithmes automatiques et gérés par les données.La première technique proposée permet de sélectionner la partie la plus stationnaire d’un signal en cadrant la représentation temps-fréquence d’un signal.La deuxième méthode est un algorithme pour l’association des dispositions spectrales, des séries harmoniques et des séries à bandes latérales avec des fréquences caractéristiques provennant du cinématique d'un système analysé. Cette méthode propose une approche unique dédiée à l’élément roulant du roulement qui permet de surmonter les difficultés causées par le phénomène de glissement.La troisième technique est un algorithme de démodulation de bande latérale entière. Elle fonctionne à la base d’un filtre multiple et propose des indicateurs de santé pour faciliter une évaluation d'état du système sous l’analyse.Dans cette thèse, les méthodes proposées sont validées sur les signaux simulés et réels. Les résultats présentés montrent une bonne performance de toutes les méthodesThis thesis proposes a three signal-processing methods oriented towards the condition monitoring and diagnosis. In particular the proposed techniques are suited for vibration-based condition monitoring of rotating machinery which works under highly non-stationary operational condition as wind turbines, but it is not limited to such a usage. All the proposed methods are automatic and data-driven algorithms.The first proposed technique enables a selection of the most stationary part of signal by cropping time-frequency representation of the signal.The second method is an algorithm for association of spectral patterns, harmonics and sidebands series, with characteristic frequencies arising from kinematic of a system under inspection. This method features in a unique approach dedicated for rolling-element bearing which enables to overcome difficulties caused by a slippage phenomenon.The third technique is an all-sideband demodulation algorithm. It features in a multi-rate filter and proposes health indicators to facilitate an evaluation of the condition of the investigated system.In this thesis the proposed methods are validated on both, simulated and real-world signals. The presented results show good performance of all the methods
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Emmanouilidis, Christos. "Evolutionary multi-objective feature selection and its application to industrial machinery fault diagnosis." Thesis, University of Sunderland, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391024.
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Storozhev, Dmitry Leonidovich. "Smart Rotating Machines for Structural Health Monitoring." Cleveland State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=csu1262724991.
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Mustafa, Mohammed Obaid. "Faults detection and diagnosis for three phase induction machines." Licentiate thesis, Luleå tekniska universitet, Signaler och system, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26592.
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Three phase induction motors have been intensively utilized in industrial applications, mainly due to their efficiency and reliability. These motors have good properties such as: increased stability and robustness, durability, large power to weight ratio, low production costs and controllability easiness. The most common faults that could happen in the rotor and the stator are: a) short circuit in stator winding, b) broken rotor bars, c) bearing failures, and d) dynamic or static air gap irregularities. These types of faults, are necessary to be identified and categorized, as soon as possible as they can end up in serious damages if not detected in due time.The aim of this licentiate thesis is to present a model based fault detection and diagnosis schemes for three phase induction motors relying on the Set Membership Identification (SMI) approach. In the proposed scheme proper uncertainty bounds and boundary violation rules have been established for detecting and categorizing the fault occurrences. The novel presented diagnostic and fault detection methods are able to detect and classify two types of induction motor faults: a) broken rotor bars, and b) short circuit in stator winding. As it will be analytically presented in the thesis, during the initialization of the algorithm, the parameters of the healthy induction motor are being identified by the utilization of the Recursive Least Squares, extended by the Set Membership concepts, where corresponding uncertainty bounds are also being recursively being calculated based on the assumed noise levels. In the sequel the proposed bound violation conditions for the fault detection and fault diagnosis are being online evaluated, on the converged identified motor parameters, within a sliding time window.The simulation results have been presented motor performance in healthy and faulty cases such as stator currents, rotor currents, torque, and angular speed of the motor. The efficiency of the proposed scheme has been extended evaluated with simulation studies for the cases of: a) one broken bar fault, b) 2\% short circuit fault, c) multiple number of broken bars.Godkänd; 2012; 20121104 (mohoba); LICENTIATSEMINARIUM Ämne: Reglerteknik/Automatic Control Examinator: Professor Thomas Gustafsson, Institutionen för system- och rymdteknik, Luleå tekniska universitet Diskutant: Post-Dr. Researcher George Georgoulas, Dept. of Informatics and Communications Technology, TEI of Epirus, Greece Tid: Tisdag den 4 december 2012 kl 10.15 Plats: A109, Luleå tekniska universitet
Feldetektering i elektriska maskiner
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Stavrou, Andreas. "Analysis and simulation of faults in squirrel cage motors." Thesis, University of Aberdeen, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390266.
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Condition based maintenance of electrical machines offers significant advantages for industry. A large part of the research effort in this area is directed towards the evaluation of fault conditions. This thesis is concerned with analysing and modelling faults in induction motors. A method for evaluating the performance of induction machines with static and dynamic eccentricity is developed, using harmonic analysis of the air gap permeance. Models able to simulate eccentricity are presented. The slip ring model equations are obtained and then used to obtain the commutator models transformed to a single reference frame. A variety of effects accompanying these fault conditions are analysed, for example variation of the eccentricity level due to unbalanced magnetic pull and the possibilities of additional vibration harmonics examined. Damping of eccentricity fields due to current redistribution, saturation and slotting are discussed. Some general steady state calculations are also presented which show that the performance of the machine need not be changed over the operating range, due to such a fault. The characteristics of combined static and dynamic eccentricity are examined and it is shown that the combined asymmetry generates additional harmonic components which are not related to those which occur when the two asymmetries take place in isolation. The development of a simulation model of machines with broken rotor bars, based on the variation in rotor parameters is presented. Experimental investigations focus mainly on observable differences in the torque transient characteristics, due to such a condition. The possibilities for using current monitoring to identify inter-turn short circuits are investigated.
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Lee, Sang-Kwon. "Adaptive signal processing and higher order time frequency analysis for acoustic and vibration signatures in condition monitoring." Thesis, University of Southampton, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242731.
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Husain, Tausif. "Rotating Reference Frame Control of Switched Reluctance Machines." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1375286539.
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Kitsos, Christos. "Predicting malfunction in quasi steady state rotating machines." Thesis, University of Leicester, 2007. http://hdl.handle.net/2381/30244.
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Dry vacuum pumps appeared in the mid-1980s in order to address problems caused by conventional fluid-sealed pumps. However, their working environment is often harsh, sometimes resulting in catastrophic faults. Continuously monitoring the state of the system and scheduling maintenance as appropriate is thus desirable.;Sliding mode techniques have been widely used in condition monitoring and fault detection schemes in recent years. Their main advantage is a fundamental robustness against certain kinds of parameter variations. They also enable faults and/or values of un-measurable system parameters to be reconstructed.;The principal aim of this thesis is to apply sliding mode techniques in order to reduce the occurrence of unplanned pump stoppages, by monitoring appropriate subsystems and parameters, for the onset of cooling system failure, bearing failure and exhaust blockage. This is achieved using the concept of the equivalent injection signal that is necessary to maintain a sliding motion. Experimental test results acquired from the dry vacuum pump test-bed illustrate the usefulness of the approach for condition monitoring. Further, the method is cost effective since it requires only low cost temperature transducers and an exhaust pressure sensor that is already part of the typical sensor package for some pump processes.;The thesis concludes with ideas and recommendations regarding possible future work, including the application of fault classification techniques and the development of processes for generating an efficient and implementable code, suitable for the vacuum pumps' embedded control systems.
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Maynard, Matthew. "Permanent magnet machines in magnetic bearings." Thesis, University of Sussex, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288787.
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In rotating machinery there exist mechanical and electrical losses. With the advent of more efficient power-electronic devices, the shift has been towards reducing mechanical losses. There are solutions that exist, such as air bearings and oil-mist bearings that go some way to reducing these losses. In order to produce an even more efficient machine, windage losses must be reduced. This can be achieved by placing the machine in a vacuum. It becomes clear, therefore, that the bearing system can only be of the magnetic type. An area of research interest that has developed as a result of higher-efficiency machines is that of flywheel-energy storage systems. The most effective machine for flywheel energy storage is the permanent-magnet machine. This does not require external excitation for motoring or generating and is easier to operate as a generator than an induction machine. In this work a permanent-magnet synchronous machine is designed and constructed, with the aid of finite-element analysis. The rotor is a novel design which uses six magnets in a two-pole configuration. This gives a rotor which is mechanically and magnetically good, yet it does not require the use of a can. The testing of this machine shows a good correlation between predicted and measured results. When a permanent-magnerto tor is placed in bearingst hat allow it to move radially, there exists an unbalanced magnetic pull between rotor and stator. These forces are predicted using a finite-element method and then measured. These results are then used as a basis . for the design of an active magneticb earing The magneticb earingw as found to be able to 0 C7 cope with these forces. The magnetic bearing itself was used as a novel way of measuring the unbalanced magnetic forces, which required no contact between the rotor and the transducer.
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Paya, Basir Abdul. "Vibration condition monitoring and fault diagnostics of rotating machinery using artificial neural networks." Thesis, Brunel University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390220.
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Ogidi, Oladapo Omotade. "Modelling and detection of faults in axial-flux permanent magnet machines." Doctoral thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/20831.
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The development of various topologies and configurations of axial-flux permanent magnet machine has spurred its use for electromechanical energy conversion in several applications. As it becomes increasingly deployed, effective condition monitoring built on reliable and accurate fault detection techniques is needed to ensure its engineering integrity. Unlike induction machine which has been rigorously investigated for faults, axial-flux permanent magnet machine has not. Thus in this thesis, axial-flux permanent magnet machine is investigated under faulty conditions. Common faults associated with it namely; static eccentricity and interturn short circuit are modelled, and detection techniques are established. The modelling forms a basis for; developing a platform for precise fault replication on a developed experimental test-rig, predicting and analysing fault signatures using both finite element analysis and experimental analysis. In the detection, the motor current signature analysis, vibration analysis and electrical impedance spectroscopy are applied. Attention is paid to fault-feature extraction and fault discrimination. Using both frequency and time-frequency techniques, features are tracked in the line current under steady-state and transient conditions respectively. Results obtained provide rich information on the pattern of fault harmonics. Parametric spectral estimation is also explored as an alternative to the Fourier transform in the steady-state analysis of faulty conditions. It is found to be as effective as the Fourier transform and more amenable to short signal-measurement duration. Vibration analysis is applied in the detection of eccentricities; its efficacy in fault detection is hinged on proper determination of vibratory frequencies and quantification of corresponding tones. This is achieved using analytical formulations and signal processing techniques. Furthermore, the developed fault model is used to assess the influence of cogging torque minimization techniques and rotor topologies in axial-flux permanent magnet machine on current signal in the presence of static eccentricity. The double-sided topology is found to be tolerant to the presence of static eccentricity unlike the single-sided topology due to the opposing effect of the resulting asymmetrical properties of the airgap. The cogging torque minimization techniques do not impair on the established fault detection technique in the single-sided topology. By applying electrical broadband impedance spectroscopy, interturn faults are diagnosed; a high frequency winding model is developed to analyse the impedance-frequency response obtained.
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Alkhfaji, Saad Sami. "Vibration control of rotating machines using actuated bearing seatings." Thesis, University of Nottingham, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.581985.
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This thesis addresses the problem of controlling the vibration of rotating machines using active bearing seatings. Contributions have been in seven areas: test rig development, rotating machinery modelling, developing appropriate control laws, updating method for piezoelectric actuators, determining specifications for the actuators from FE models, modal correlation methods (with and without frequency weighting) and modal expansion. A rotating machine test rig has been designed and constructed. In this rig, an active bearing seating has been designed to accommodate two actuators, located orthogonally and exerting control forces at each of two bearings. The rig is a versatile unit- the first one of its kind in the UK having a rotor whose bearings are supported on active seatings. Determining the requirements for force, stroke and bandwidth of the actuators for bearing seatings begins with an accurate numerical model of the system. A displacement-based FE model incorporating the active bearing seating has been developed and applied for predicting the dynamic behaviour of a rotating machine. Both steady-state responses and transient responses (run-up / run-down) are considered. The model has been validated experimentally by performing an experimental modal analysis of the test rig. A third area is in the development of suitable control laws. The same numerical model developed for assessing the actuator specifications has been employed to develop the control strategy. A control algorithm has been developed for vibration suppression. In this, the core ideas of classical optimal control are adopted (namely trading-off control effort against tracking performance). The "Simplex" (Nelder- Mead) method has been applied. The optimisation study is carried out for collocated actuation and sensing and for the general case, non-collocated control. Synchronous vibration is minimized in a root mean squares sense. Numerical simulations have shown that the proposed optimal closed-loop control strategy is very effective in reducing the amplitude of the forced vibration under different operating conditions. This controller is easy to implement in practical applications. A complete experimental and computational characterisation has been carried out on the piezoelectric actuators. An experimental arrangement has been established to measure two frequency- response functions. From these the complete dynamic properties of the piezoelectric stack actuators can be determined. Based on the measurements and the basic equations of the actuator, a computational model written in MA TLAB has been developed by which the parameters can be extracted. The experiment is simple to do with standard vibration-laboratory equipment and is very effective in characterising the actuator. The tests have been performed on four nominally-identical actuators and different parameters are obtained in each case. Obtaining accurate values for these parameters is an essential step towards having a reliable model for the complete closed-loop system. A set of novel modal correlation measures for generally-damped systems has been developed. In each case, a dimensionless (n x n) modal-matching array is produced whose entries indicate which pairs of modes from the first system best correlate with any particular pair of modes from the second system. This modal-matching array exhibits 2nd -order behaviour with respect to any scalar measure of that discrepancy. The work was motivated originally by the application of developing Campbell diagrams for rotating machines as continuous curves - rather than simply plotting large set of discrete points. There are several possible motivations for the proposed procedures. The most important is probably the model updating application where a vital first step is to ensure that modes have been correctly paired. The methods have been illustrated in two examples and comparisons with the established Modal Assurance Criterion methods show the new method in a good light. Two frequency dependent operations for generally-damped systems are presented in this thesis. The first operation involves developing a new frequency dependent modal expansion while the second operation generalises a previously-proposed modal correlation approach for these systems such that particular frequencies are targeted. The two suggested methods are illustrated using numerical examples.
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Yeh, Ting-Jen. "Modeling, analysis and control of magnetically levitated rotating machines." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/11214.
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Yao, Yanmei. "Study of Induction Machines with Rotating Power Electronic Converter." Doctoral thesis, KTH, Elkraftteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-196054.
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This thesis investigates a novel induction machine topology that uses a rotating power electronic converter. Steady-state and dynamic performance of the topology is studied to understand its operational principle. Furthermore the potential of improving its efficiency and power factor is investigated. The topology is referred to as wound rotor induction machine with rotating power electronic converter (WRIM-RPEC). The WRIM-RPEC topology offers the possibility to magnetize the induction machine from the rotor side by introducing a reactive voltage in the rotor. Thus, the power factor of the machine can be improved. Constant speed variable load operation can be achieved by setting the frequency of the introduced voltage. Two options of rotor winding and converter configuration in the WRIM-RPEC system are investigated. The wound rotor windings can either be open-ended and fed by a three-phase back-to-back converter or Y-connected and fed by a single three-phase converter. The dc-link in both converter configurations contains only a floating capacitor. These two configurations give different dc-link voltages at the same torque and speed. Two analytical steady-state models of the topology are developed in this thesis. The first model can be used to analyze the operating condition of the motor at specific speed and torque. Particularly, the operating range of speed and torque of the topology is investigated. The second model is used to analyze variable power factor operation, including unity power factor operation. Analytical calculations and measurements are carried out on a 4-pole, 1.8kW induction machine and the results are compared. A dynamic mathematic model is then developed for the WRIM-RPEC system for the back-to-back converter configuration. The mathematic model is then applied in Matlab/Simulink to study the dynamic performance of the system including starting, loading and phase-shifting. The simulation results are compared with measurements on the 4-pole, 1.8kW induction machine. Moreover, the simulation model using the existing Simulink blocks are studied to compare with the results obtained from the mathematic model. Furthermore, the dynamic performance of the WRIM-RPEC system with the single converter configuration is investigated. In addition, harmonic spectra analysis is conducted for the stator and rotor currents. In the last part of the thesis, efficiency improvement is investigated on the 4-pole induction machine when it is assumed to drive a pump load. It is shown that the efficiency can be further improved by decreasing the rotor resistance. Due to space constraints it is however difficult to decrease the rotor resistance in a 4-pole induction machine. An investigation is thus carried out on a standard 12-pole, 17.5kW squirrel-cage induction machine with inherent low power factor. The cage rotor is redesigned to a wound rotor to enable the connection of converter to the rotor windings. An analytical model is developed to design the wound rotor induction machine. The machine performance from calculations is then compared with FEM simulations with good agreement. The analytical model is further used to design several WRIMs with different dimensions and rotor slot numbers. Power factor and efficiency improvement is then explored for these WRIMs. A promising efficiency increase of 6.8% is shown to be achievable.QC 20161111
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Tallam, Rangarajan M. "Current-based sensorless detection of stator winding turn faults in induction machines." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/13429.
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Abboud, Dany. "Vibration-based condition monitoring of rotating machines in nonstationary regime." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0106/document.
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Dans les dernières décennies, la surveillance vibratoire des machines tournantes a acquis un intérêt particulier fournissant une aide efficace pour la maintenance dans l'industrie. Aujourd'hui, de nombreuses techniques efficaces sont bien établies, ancrées sur des outils puissants offerts notamment par la théorie des processus cyclostationnaires. Cependant, toutes ces techniques reposent sur l'hypothèse d’un régime de fonctionnement (c.à.d. vitesse et/ou charge) constant ou éventuellement fluctuant d’une façon stationnaire. Malheureusement, la plupart des machines surveillées dans l'industrie opèrent sous des régimes non stationnaires afin de remplir les tâches pour lesquelles elles ont été conçues. Dans ce cas, ces techniques ne parviennent pas à analyser les signaux vibratoires produits. Ce problème a occupé la communauté scientifique dans la dernière décennie et des techniques sophistiquées de traitement du signal ont été conçues pour faire face à la variabilité du régime. Mais ces tentatives restent limitées, dispersées et généralement peu soutenues par un cadre théorique. Le principal objectif de cette thèse est de combler partiellement cette lacune sur la base d'une formalisation théorique du sujet et d’un développement systématique de nouveaux outils de traitement du signal. Dans ce travail, la non-stationnarité du régime est limitée à celle de la vitesse— c.à.d. vitesse variable et charge constante— supposée connue a priori. Afin d'atteindre cet objectif, la méthodologie adoptée consiste à étendre le cadre cyclostationnaire avec ses outils dédiés. Nous avons élaboré cette stratégie en distinguant deux types de signatures. Le premier type comprend des signaux déterministes connus comme cyclostationnaires au premier ordre. La solution proposée consiste à généraliser la classe cyclostationnaire au premier ordre à la classe cyclo-non-stationnaire au premier ordre qui comprend des signaux déterministes en vitesse variable. Le second type comprend des signaux aléatoires périodiquement corrélés connus comme cyclostationnaires au deuxième ordre. Trois visions différentes mais complémentaires ont été proposées pour traiter les variations induites par la non-stationnarité de la vitesse de fonctionnement. La première adopte une approche cyclostationnaire angle\temps, la seconde une solution basée sur l'enveloppe et la troisième une approche cyclo-non-stationnaire (au second ordre). De nombreux outils ont été conçus dont les performances ont été testées avec succès sur des signaux vibratoires réels et simulésIn the last decades, vibration-based condition monitoring of rotating machine has gained special interest providing an efficient aid for maintenance in the industry. Nowadays, many efficient techniques are well-established, rooted on powerful tools offered in particular by the theory of cyclostationary processes. However, all these techniques rely on the assump-tion of constant— or possibly fluctuating but stationary— operating regime (i.e. speed and/or load). Unfortunately, most monitored machines used in the industry operate under nonstationary regimes in order to fulfill the task for which they have been designed. In this case, these techniques fail in analyzing the produced vibration signals. This issue, therefore, has occupied the scientific committee in the last decade and some sophisticated signal processing techniques have been conceived to deal with regime variability. But these works remain limited, dispersed and generally not supported by theoretical frameworks. The principal goal of this thesis is to partially fill in this gap on the basis of a theoretical formalization of the subject and a systematic development of new dedicated signal processing tools. In this work, the nonstationarity of the regime is confined to that of the speed— i.e. variable speed and constant load, assumed to be known a priori. In order to reach this goal, the adopted methodology consists in extending the cyclostationary framework together with its dedicated tools. We have elaborated this strategy by distinguishing two types of signatures. The first type includes deterministic waveforms known as first-order cyclostationary. The proposed solution consists in generalizing the first-order cyclostationary class to the more general first-order cyclo-non-stationary class which enfolds speed-varying deterministic signals. The second type includes random periodically-correlated waveforms known as second-order cyclostationary. Three different but complementary visions have been proposed to deal with the changes induced by the nonstationarity of the operating speed. The first one adopts an angle\time cyclostationary approach, the second one adopts an envelope-based solution and the third one adopts a (second-order) cyclo-non-stationary approach. Many tools have been conceived whose performances have been successfully tested on simulated and real vibration signals
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Chauvicourt, Fabien. "Vibro-acoustics of rotating electric machines: Prediction, Validation and Solution." Doctoral thesis, Universite Libre de Bruxelles, 2018. https://dipot.ulb.ac.be/dspace/bitstream/2013/271049/4/thesis.pdf.
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The increase of greenhouse gas emission is commonly accepted to largely contribute to global warming, in part due to the massive use of non-renewable fossil energy sources. It is a reason why recently, beside other industrial sectors, electric mobility has been considered as the next generation for transportation systems. But the electrification of a vehicle introduces new challenges in its design since it involves different domains of expertise than the ones from Internal Combustion Engine (ICE) vehicles. In particular, Noise, Vibration and Harshness (NVH) comfort is significantly affected by powertrain changes, i.e. from ICE to electric machine. High and unpleasant acoustic noise from resonances may occur but can be addressed numerically to support decision making processes early enough in the design stages. The accurate prediction of its radiated acoustic noise then requires a thorough multi-physical understanding, from the system-level (electric machine) to the component-level (stator and rotor cores).First from a system-level point of view, two multi-physical modeling frameworks that use different model simplifications were implemented. By comparing simulated results to experimental measurements at each physical step of the modeling flow (electromagnetic, vibration, acoustic), it was shown that both models are accurate enough for pre-designing phases. It was also shown that considering only the stator core to contribute to the vibro-acoustic behavior of electric machines is a valid assumption.Second from a component-level point of view, the rotor and the stator core were investigated. The rotor influence on the complete machine structural dynamics was assessed. Beside the validated effects of different rotor topologies on the radiated noise, an analytical model was successfully developed to explain the occurrence of a particular vibration mode; whose explanation was still not offered in literature. In parallel, the stator core was studied, essentially because it is composed of hundreds of thin laminations stacked together which introduce difficulties in understanding its structural behavior. The effects of the laminations on the structural behavior of the stator core were studied numerically and experimentally as well. Two modeling guidelines were thus provided depending on the mode shape of interest and the computational resources available. The experimental studies comforted these two modeling approaches, and also permitted to highlight the importance of looking at the damping properties. Therefore it was shown that different lamination stacking techniques could affect significantly this damping.Finally the influence of the stacking technique (gluing, welding) on the structural behavior of the laminated compound motivated the implementation of an alternative solution to the mitigation of resonance phenomenon responsible for large acoustic noise. By using a skewed distribution of welding or glue lines, the technique aims at forcing laminations to vibrate with different phases which generates friction between them. The induced damping increases and then depends on the introduced asymmetry and on the mode shape considered. This innovative technique was validated experimentally and showed up to 7 times higher structural damping and 10 dB reduction in structural transfer function amplitudes.Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
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Blaschke, Peter Gerhard. "Vibro-acoustic design tool for noise optimization of rotating machines." Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/7355.
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Jiffri, Shakir. "Advanced passive and active methods for vibration control in rotating machines." Thesis, University of Nottingham, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.582112.
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Effective control of vibration in rotating machinery is a major concern in many industries and research institutions. With the ever-increasing drive for higher operating speeds, the need for developing vibration mitigation methods that cater for the arduous operating conditions that consequently arise is paramount. Phenomena that may have been insignificant in relatively low-speed rotating machines begin to gain importance with increasing speed, an example of which is the gyroscopic effect. This thesis is aimed at enriching the knowledge base on rotordynamic vibration control. Independent Modal Control (IMC) is addressed, within the context of rotating machinery. A study is performed on various actuation technologies that may be used to implement active vibration control. The well-known problem of balancing rotating machinery is also considered. The first-order modal filters based on Structure Preserving Transformations (SPTs) are capable of decoupling a rotor dynamic system into individual modes of vibration, such that IMC may be performed. Unlike traditional control schemes, the method based on first-order modal filters does not require the imposition of highly restrictive conditions on the system (classical damping). As a result, gyroscopic effects - which are substantial in high-speed rotating machinery - and non-classical damping may be fully accounted for in the modal domain. The main problem pertaining to this method arises from the fact that the response of the controlled system is linked with the stability of the modal filters. As such, if the filters are unstable, the controlled response is eventually overcome by noise. This thesis explores the spectral properties of the modal filter with a view to understanding the factors that affect its stability; some interesting findings on the filter eigenvalues are presented. Furthermore, the question as to whether filter stability is an essential requirement is addressed. The relationship between the rotordynamic system and the modal filter is also investigated. An illustration of the techniques developed in relation to IMC using first-order modal filters is presented in the form of a FE simulation on a realistic aero-engine model. The implementation of active vibration control in a dynamic system is realised through the application of control forces by actuators. In the case of rotating machines, these would normally be located at the bearings. Actuation may be achieved from a variety of technologies such as electromagnetic, piezoelectric, magnetostrictive, ultrasonic etc. This thesis conducts a study on some popular actuation technologies, with the aim of finding an effective alternative to the ubiquitous squeeze film damper. The merits and drawbacks of the various technologies are compared. Also, some novel design concepts are proposed, and (in some cases) their viability demonstrated through calculations. It is well-known that rotor unbalance is usually the main source of vibration in rotating machines. Thus, improvements in procedures for balancing such machines are continuously being sought. With increasing in-service operating speeds and ever more stringent standards, traditional balancing methods progressively become inadequate. One of the reasons for this is the inability of balancing tests to capture the contribution of patterns of unbalance that excite higher modes of vibration, as the tests speeds are usually lower than in-service speeds. This thesis proposes a robust balancing approach that utilises additional information on rotor unbalance, in the form of a covariance matrix, to improve the balancing procedure. The method is illustrated in a FE model of a rotating machine, and is shown to be superior to the traditional method.
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Neill, Gary David. "PC based diagnostic system for the condition monitoring of rotating machines." Thesis, Heriot-Watt University, 1998. http://hdl.handle.net/10399/1266.
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Zhu, Hui. "Partial discharge propagation, measurement, and calibration in high power rotating machines." Thesis, Glasgow Caledonian University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261609.
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Hargreaves, Philip Alexander. "Advanced performance prediction tools for the analysis of rotating electrical machines." Thesis, University of Newcastle upon Tyne, 2015. http://hdl.handle.net/10443/2853.
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This thesis seeks to advance the design tools for electrical generators. It aims to undertake an electrical generator’s design, using the Finite Element method within a defined time frame. The thesis looks at the history of generator design systems and outlines the parameters a designer must predict. These parameters are then duly calculated using various finite element methods. The thesis introduces a Pseudo Rotating Superposition system, which allows large quantities of data to be found from single static finite element simulations. Initially the system is used to predict machine saturation curves, and it is later expanded to predict the transient performance of generators. The full load performance of generators is found using a novel multivariable clustered optimisation routine. An extension using a rotating finite element solver, with pseudo rotating superposition, is then demonstrated. This creates a method which allows voltage harmonics to be quickly, accurately and validly predicted. Finally a study of iron loss is undertaken and using the above method it is shown that iron loss can be validly calculated using the quicker Radial/Tangential reference frame, rather than a slower Major/Minor frame. A collection of 48 manufactured machines are used throughout as a test group for the created methods. Results from design calculations are compared to both factory test results and to the predictions from an existing customised in house design software tool. The methods within this thesis are shown to be over 35% more accurate in the majority of cases. The whole suite of methods created can automatically calculate results for any given machine in less than 1 hour. The computer macros described in this thesis and the comparison with existing design methods and test were all made by the Author.
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le, Roux Wiehan. "On-line detection of rotor faults in permanent magnet machines using only terminal quantities." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/16665.
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Wood, Graeme Brendon. "The quantification of airflows generated by rotating rollers in wool carding machines." Thesis, University of Canterbury. Department of Mechanical Engineering, 2001. http://hdl.handle.net/10092/2281.
Full textAbstract:
The properties of fibres make them easily manipulated by aerodynamic forces. The carding
machine, used in cotton and wool processing, is an example of equipment that creates
aerodynamic forces due to fast rotating cylinders with rough surfaces. These forces are
generally seen as an undesirable side effect in fibre processing machinery, exacerbated with
modern equipment using faster rotating components.
This work attempts to quantify these aerodynamic forces on carding machines used in the
wool industry. A combination of boundary layer theory, experiments using hot wire
anemometry and flow visualisation, and Computational Fluid Dynamics (CFD) software
(Fluent) was used to build up an understanding of aerodynamics in the example of wool
carding machines. The theoretical and experimental work progressed along the following
topics to determine each effect on carding machine aerodynamics: rough surfaces,
centrifugal forces, three-dimensional edge effects, and interactions between rotating
cylinders. Examples from each section were modelled using CFD, which was found to
accurately simulate theoretical and experimental results in most cases. It could also
accurately predict the complex two-dimensional airflow patterns occurring in carding
machines. The CFD simulations underestimated the degree of turbulence generated by
interactions between rotating cylinders. Three-dimensional effects were overestimated, due
in part to attempting to apply the results of an oversimplified model to a full-scale carding
machine.
In undertaking this work, it was found the universal velocity distribution equations
describing flow over flat plates (for both smooth and rough surfaces) could also be used for
flow induced by rotating cylinders by compensating for curvature effects.
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Van, der Merwe Nicolaas Theodor. "The application of signal processing and artificial intelligence techniques in the condition monitoring of rotating machinery / Nicolaas Theodor van der Merwe." Thesis, North-West University, 2003. http://hdl.handle.net/10394/68.
Full textAbstract:
Condition monitoring of critical machinery has many economic benefits. The primary
objective is to detect faults, for example on rolling element bearings, at an early stage to
take corrective action prior to the catastrophic failure of a component. In this context, it is
important to be able to discriminate between stable and deteriorating fault conditions. A
number of conventional vibration analysis techniques exist by which certain faults in
rotating machinery may be identified. However, under circumstances involving multiple
fault conditions conventional condition monitoring techniques may fail, e.g. by indicating
deteriorating fault conditions for stable fault situations or vice versa. Condition monitoring
of rotating machinery that may have multiple, possibly simultaneous, fault conditions is
investigated in this thesis. Different combinations of interacting fault conditions are
studied both through experimental methods and simulated models. Novel signal
processing techniques (such as cepstral analysis and equidistant Fourier transforms) and
pattern recognition techniques (based on the nearest neighbour algorithm) are applied to
vibration problems of this nature. A set of signal processing and pattern recognition
techniques is developed for the detection of small incipient mechanical faults in the
presence of noise and dynamic load (imbalance). In the case investigated the dynamic
loading consisted of varying degrees of imbalance. It is demonstrated that the proposed
techniques may be applied successfully to the detection of multiple fault conditions.Thesis (Ph.D. (Electronical Engineering))--North-West University, Potchefstroom Campus, 2004.
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Cash, M. Alex. "Detection of turn faults arising from insulation failure in the stator windings of AC machines." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/15460.
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