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Lima, Pedro Henrique Ramos de. "Análise modal experimental de placa flexível acoplada à cavidade acústica por vibrometro laser." reponame:Repositório Institucional da UnB, 2017. http://repositorio.unb.br/handle/10482/31273.
Повний текст джерелаАнотація:
Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2017.Submitted by Raquel Almeida (raquel.df13@gmail.com) on 2017-12-12T16:45:17Z No. of bitstreams: 1 2017_PedroHenriqueRamosdeLima.pdf: 6352915 bytes, checksum: e0a6f8814ff8e9ecaa5dfa01464ee065 (MD5)
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O estudo da vibroacústica, uma área de interação fluido-estrutura, é extremamente importante em diversos ramos da engenharia, como civil, mecânica, aeronáutica, naval, nuclear e bioengenharia. Uma fonte de ruído em cavidades ocorre pela interação entre a estrutura flexível e a cavidade fluida ocasionando ondas acústica e vibratórias estruturais acopladas. Para investigar esses fenômenos utilizou-se modelo experimental simplificado que consiste em uma cavidade rígida de madeira acoplada à uma placa flexível de alumínio estudada por técnicas experimental, analítica e numérica. Contudo, a identificação experimental da dinâmica da placa flexível acoplada a cavidade acústica não tinha sido realizada. O presente trabalho realiza a identificação modal de uma placa flexível de alumínio, acoplada a uma cavidade acústica rígida com o intuito de entender o comportamento do sistema acoplado, validar e comparar os resultados obtidos pelos métodos numéricos e experimentais. Uma fonte sonora calibrada é utilizada para excitar o sistema acoplado placa mais cavidade acústica. E um vibrometro laser para efetuar a medição dinâmica da placa. Por fim, este trabalho compara e valida os resultados experimentais com relação aos resultados anteriores numéricos, analíticos e experimentais para cavidades vibroacústicas além de considerar resultados da literatura.
The study of vibroacoustics (a area of fluid-structure interaction) has importance in many branches of engineering, such as civil, mechanical, aeronautical, naval, bioengineering and nuclear. A source of cavity noise occurs through the interaction between the flexible structure and the fluid cavity causing acoustic waves and coupled structural vibrations. To investigate these phenomena was used a simplified experimental model consisting of a rigid wooden cavity coupled to a flexible aluminum plate studied by experimental, analytical and numerical techniques. However, the experimental identification of the dynamics of the flexible plate coupled to acoustic cavity had not been performed. The present work presents the modal identification of a flexible aluminum plate coupled to a rigid acoustic cavity in order to understand the behavior of the coupled system, validate and compare the results obtained by numerical and experimental methods. A calibrated sound source is used to excite the system coupled plate plus acoustic cavity. A laser vibrometer is used to perform the dynamic measurement of the plate. Finally, this work compares and validates the experimental results in relation to previous numerical, analytical and experimental results for vibroacoustic cavities in addition to considering results from the literature.
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Eriksson, Anna. "Mating disruption in Scaphoideus titanus Ball (Hemiptera: Cicadellidae) by vibrational signals." Doctoral thesis, country:IT, 2013. http://hdl.handle.net/10449/23857.
Повний текст джерелаАнотація:
Conventional pesticides have detrimental effects on the global health and a development of environmentally friendly alternatives to control agricultural pests is essential. Mating disruption is an example of such method, since it exploits the natural airborne pheromone plumes that females emit to attract males. When a synthetic pheromone is applied to a field, males are disorientated and mating is prevented in the treated area. However, not all insect species communicate with olfactory signals. It has been estimated that 150 000 species use vibrations to achieve mating and among them there are several pests and important vectors of plant diseases. To control such species, growers may need to apply large amounts of pesticides, which is both environmentally and economically costly.
The main goal of the present thesis was therefore to develop a vibrational mating disruption strategy. For this, the leafhopper Scaphoideus titanus was chosen as model species, since it uses vibrations both for mating and rivalry, along with being an economically important vector of the severe phytoplasma grapevine disease Flavescence doreé. Besides experiments concerning the proper mating disruption, laboratorial studies were made on signal transmission through grapevine tissues and on the ability of males and females to emit and receive substrate-borne signals. For the first time, it was shown that substrate-borne vibrational signals can allow communication between individuals despite lack of substrate continuity. This is an important contribution for an improved knowledge of the subject, but also to consider for control of insects that are distributed on closely adjacent plants like grapevine. Moreover, it was shown that males
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are able to make directional decisions towards females and that there is an increased level of female signal intensity that triggers the male to initiate courtship. Pair formation in S. titanus starts with identification and proceeds with a location (search) stage before the final courtship. In the identification duets, male pulses were delayed after female reply, while they were fully synchronized during location and courtship duets. It is possible that mating disruption with vibrations is more successfully applied during the identification stage when external interferences could result in loss of important information that is needed to correctly identify the mating partner.
Finally, during the mating disruption experiments, a pre-recorded natural rivalry signal of S. titanus was used for disruption when transmitted via grapevine wires to plants, where it masked the communication between males and females. In both semi-field and field experiments, the number of mated females was significantly reduced in presence of disruptive signal while females were mated in the silent control plants. These results suggest that vibrational mating disruption may have an important impact on future integrated pest managements of agricultural productions. Moreover, it is possible that the method can be applied to control different vibrational communicating pests. Vibrating plants in greenhouses may be easier than in an open field due to the protected environment and presence of energetic source. Yet, although the results from this thesis have shown that the principle of the method is promising, a future goal will first be to optimize the energetic and economic expenses of the system.
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Acharya, Dabit. "COMPARATIVE EXPERIMENTAL STUDIES FOR GLOBAL DAMAGE DETECTION IN PLATES USING THE SCANNING LASER VIBROMETER TECHNIQUES." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1155079600.
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Rajm, Martin. "Laserový vibrometr s 2D rozmítáním." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2012. http://www.nusl.cz/ntk/nusl-219813.
Повний текст джерелаАнотація:
This thesis deals in the theoretical part with the non-contact vibration measurement by single point Laser Doppler vibrometer and it concretes constructions used in practice. It deals also with the possibilities of the laser beam scanning to measure the vibrations in the plane and there are also listed suitable-commercial systems for this solution. Mentioned sweep is immediately necessary for 2D scanning vibrometer construction. In the practical part, the single-point laser vibrometer OFV-5000 was expanded by scanning galvo system, supplemented by a measuring cards for signal acquisition from the vibrometer and suitable control hardware was chosen for mentioned laser. For the resulting hardware assembly was designed and implemented in LabVIEW measurement software, to control the 2D scanning system, to set the position of the laser beam and to process and to visualize of measured vibration signals in the plane. The functionality of the developed measuring system was checked by performed measurement and visualization of the velocity vibration of restraint girder, excited by shaker.
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Iverson, Thomas Z. "Signature Stability in Laser Doppler Vibrometry." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1497386740815576.
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Olsson, Erik. "Sound source localization from laser vibrometry recordings." Doctoral thesis, Luleå : Division of experimental mechanics, Luleå University of Technology, 2007. http://epubl.ltu.se/1402-1544/2007/23/.
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Tirabassi, Mario. "Uncertainty due to misalignment in Laser Vibrometry." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8579.
Повний текст джерелаАнотація:
Laser Doppler Vibrometry (LDV) is a well established technique used for non intrusive velocity measurements in fluid flows and on solid surfaces. Unlike traditional contacting vibration transducers, laser vibrometers require no physical contact with the test object. The ability to combine advanced mirror systems together with the laser source allows automated scanning LDV (SLDV) measurements, where a high number of measurement points can be measured consecutively. Non-contact vibration measurements with very high spatial resolution are possible with such a scanning system and can lead to a significantly more detailed analysis from vibration tests. One of the main limitations of Laser Vibrometry is the difficulty to realize a perfect alignment between the investigated target and the laser beam. Frequently, for engineering applications, it is desirable to investigate different points on a target using the LDV system and, in this case, accurate knowledge of the measuring point position is required. Misalignments associated with the laser beam or the optics used to deflect the beam introduce deviation from the desired position and uncertainties in the measured velocity. All optical configurations are sensitive to misalignments, especially scanning systems able to move the laser beam around static or rotating targets. This thesis describes advances in the application and interpretation of such measurements using Laser Vibrometry and concentrates on the analysis of the uncertainties due to the inevitable misalignments between the laser beam and the investigated target in vibration measurements on rotating components. The work is divided into three main sections. The first part proposes a novel method to model any kind of LDV optical arrangement suitable for vibration measurements. This model has been developed with scanning LDV systems in mind but it can be used for any optical configuration. The method is based on a vector approach and integrates directly with the Velocity Sensitivity Model to determine the velocity measured by a single incident beam. The resulting mathematical models describe completely the beam path, the scan pattern and the measured velocity in the presence/absence of target vibrations and misalignments without any kind of approximation. The mathematical expressions derived are complex but easily implemented in software such as Matlab. The models are an important tool for LDV because they help the user to have a better understanding of measured data and to make the best alignment possible. The second part of the thesis concentrates on the modelling of different optical systems using the new method. Different systems from the simplest to the most complex have been analysed using the method. For some arrangements, mathematical models have been formulated for the first time such as for the newly proposed single and dual wedge SLDV systems and for the recently introduced Dove prism SLDV system. These systems are compared to the dual mirror SLDV system. In particular, for the single and the dual wedge SLDV systems, experimental tests have been performed to validate theoretical predictions. The results confirm the validity of the models and show the potential of these systems. Established systems such as the dual mirror and the self-tracking SLDV systems, for which generally less comprehensive models can be found in literature, have been re-analysed with the new method and theoretical predictions have been compared to the data from literature in order to confirm the validity of the new models and also to investigate for the first time some details that have previously been neglected. The models enable identification of the main characteristics of any arrangement, in particular the sensitivity to typical misalignments and target vibration components. For tracking applications on rotating targets, the presence of misalignments causes measured velocities at DC and the first target rotation harmonic whose values depend on how the misalignments combine. The analysis of misalignment effects enables identification of the optical device(s) with the most critical alignment and supplies an initial estimation of the level of uncertainty affecting typical, practical applications. Investigation shows as the self-tracking scanning systems are much sensitive to misalignments and target vibrations than the other scanning systems. The third part of the thesis concentrates on effects on radial and pitch/yaw vibration measurements on rotating targets of both misalignments and surface roughness of the test rotor. It is known that radial and pitch/yaw vibrations taken directly from a rotor using LDV are affected by a cross-sensitivity to the orthogonal vibration component. Resolution of the individual radial or pitch and yaw components is possible via a particular arrangement of the laser beams and using a dedicated resolution algorithm. Error sources such as instrument misalignments, rotation speed measurement error and introduce uncertainties in the resolution algorithm output. Research has quantified these uncertainties when radial vibrations with different or equal amplitude are applied to the target. Particular attention has been given to the effects that surface roughness has on the cross-sensitivity encountered in these measurements. From the tests, it is possible to identify three different ranges of surface roughness. For very smooth circular rotors, the cross-sensitivities are negligible and measurements can be made directly on the rotor without the need for a resolution algorithm. For very rough surfaces including surfaces coated in retro-reflective tape, the measurements have to be resolved to remove the cross-sensitivity. For surface roughnesses between the very smooth and the very rough, reliable measurements cannot be made because levels of the cross-sensitivity cannot be predicted making correct resolution impossible. The significant developments in the use of Laser Vibrometry for different optical configurations and quantification of the uncertainties expected for typical applications on rotating components realised during this research project make this work a practical and important tool for the user.
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Chan, Alfred. "Vocal fold vibration measurements using laser Doppler vibrometry." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=106574.
Повний текст джерелаАнотація:
The objective of this study was to measure the velocity of the superior surface of human vocal folds during phonation using laser Doppler vibrometry (LDV). A custom-made endoscopic laser beam deflection unit was designed and fabricated. An in vivo clinical experimental procedure was developed and performed at the Montreal General Hospital Voice Laboratory in order to simultaneously collect velocity data from the LDV and video from endoscopy. The velocity along the direction of the laser beam, ie. the inferior-superior direction, was captured and found to be synchronous with electroglottograph (EGG) and sound level meter data. Recorded phonation onset/offset times were found to be commensurate with reported data obtained using EGG and high-speed imaging. The vibration energy of the vocal folds was determined to be significant up to a frequency of 3 kHz. The velocity amplitude was found to be approximately 45 mm/s and was consistent between subjects. A sparse map of the vocal fold surface velocity was obtained, which showed that the velocity amplitude did not change significantly with location. Different characteristic vibration waveforms were identified and attributed to the presence of a mucosal wave over the vocal fold surface. Laser Doppler vibrometry offers potential as a diagnostic tool for the early detection of vocal disorders. It may provide online biofeedback for voice professionals, and help them to tune their laryngeal tension to obtain the desired voice output.La présente étude avait pour but de mesurer directement la vitesse des cordes vocales de la voix humaine en utilisant la vibrométrie laser (VL). Une buse endoscopique pour la re-direction du faisceau laser a été conçue et construite. Un protocole expérimental de mesures en clinique a été développé et mis en oeuvre afin d'obtenir des signaux de vitesse simultanément avec des images vidéoendoscopiques. Les mesures furent prises au laboratoire de la voix de l'Hôpital Général de Montréal. La vitesse mesurée est dans l'axe du faisceau laser, soit dans la direction inférieure-supérieure. Des signaux synchrones provenant d'un électroglottogramme (EGG) et d'un microphone furent recueillis pour fins de comparaisons et de vérifications. Les signaux provenant du VL sont parfaitement corrélés et consistants avec les signaux du EGG et microphone ainsi que les informations provenant du vidéo. L'énergie vibratoire semble être présente dans un bande de fréquence allant jusqu'à 3 kHz. La vitesse est de 45 mm/s dans les trois cas étudiés, pour toute fréquence, amplitude et position. Différents modes vibratoires avec des formes d'ondes distinctes furent identifiés, probablement dus à la propagation d'ondes sur la surface supérieure des cordes vocales. Les résultats suggèrent que l'utilisation du VL pourrait mener à des applications intéressantes pour la détection de problèmes tels que des lésions. La VL pourrait aussi sans doute fournir une rétroaction à des professionnels de la voix qui leur permettrait d'ajuster la tension et la position de leur cordes vocales afin d'obtenir le timbre ou l'intonation désirée.
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Martin, Peter. "Uncertainty due to speckle noise in laser vibrometry." Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/7139.
Повний текст джерелаАнотація:
This thesis presents fundamental research in the field of laser vibrometry for the application to vibration measurements. A key concern for laser vibrometry is the effect of laser speckle which appears when a coherent laser beam scatters from an optically rough surface. The laser vibrometer is sensitive to changes in laser speckle which result from surface motions not in the direction of the incident beam. This adds speckle noise to the vibrometer output which can be indistinguishable from the genuine surface vibrations. This has been termed ‘pseudo-vibration' and requires careful data interpretation by the vibration engineer. This research has discovered that measurements from smooth surfaces, even when no identifiable speckle pattern is generated, can produce noise and therefore reference to speckle noise, in such circumstances, is inappropriate. This thesis has, therefore, adopted the more general term of pseudo-vibration to include noise generated from any surface roughness or treatment, i.e. including but not limited to speckle noise. This thesis develops and implements novel experimental methods to quantify pseudovibration sensitivities (transverse, tilt and rotation sensitivity) with attention focussed on commercially available laser vibrometers and consideration is given to a range of surface roughnesses and treatments. It investigates, experimentally, the fundamental behaviour of speckles and attempts to formulate, for the first time, a relationship between changes in intensity to pseudo-vibration sensitivity levels. The thesis also develops and implements models for computational simulation of pseudo-vibrations using the fundamental behaviour of speckles. The combination of experimentation and simulation improves current understanding of the pseudo-vibration mechanisms and provides the vibration engineer with a valuable resource to improve data interpretation. Two experimental methods of quantifying pseudo-vibration sensitivity are developed and successfully applied in the evaluation of transverse, tilt and rotation sensitivity for two models of commercial laser vibrometer. These evaluations cover both single beam (translational vibration measurement) and parallel beam (for angular vibration measurement) modes. The first method presented requires correction of the vibrometer measurement with an independent measurement of genuine velocity to produce an iii apparent velocity dominated by the required noise components. The second method requires a differential measurement using two vibrometers to cancel common components such as genuine velocity, leaving only uncorrelated noise from each measurement in the resulting apparent velocity. In each case, a third measurement is required of the surface motion component causing pseudo-vibration and this is used to normalise the apparent velocity. Pseudo-vibration sensitivity is then presented as a map showing the spectral shape of the noise, as a mean and standard deviation of harmonic peaks in the map and as a total rms level across a defined bandwidth. The simulations employ a novel and effective approach to modelling speckle evolution. Transverse and tilt sensitivity are predicted for the first time and are verified by the experimental study. They provide the vibration engineer with the potential to estimate pseudo-vibrations using a simple piece of software. The laser beam spot diameter has a large influence on the pseudo-vibration sensitivity. Transverse sensitivity has been quantified as around 0.03% and 0.01% (per order) of the transverse velocity of the surface for beam spot diameters of 100 μm and 600 μm respectively. Larger beam spots have been shown to significantly reduce transverse sensitivity and measurements from smoother surfaces have also shown a reduced level of transverse sensitivity. Tilt sensitivity has been quantified at about 0.1 μms-1/degs-1 and 0.3 μms-1/degs-1 (per order) of angular velocity of the surface for beam spot diameters of 100 μm and 600 μm respectively. Smaller beam spot diameters significantly reduce tilt sensitivity. The surface roughness or treatment has been shown to have little effect on the level of tilt sensitivity. Rotation sensitivity has been quantified at approximately 0.6 μms- 1/rads-1 and 1.9μms-1/rads-1 (per order) of rotation velocity of the rotor for 90 μm and 520 μm. Smaller beam spot diameters have shown a significant reduction in rotation sensitivity and measurements on smoother surfaces have shown a reduced rotation sensitivity. Focussing the laser beam approximately on the rotation axis has also shown a significant reduction in rotation sensitivity. Parallel beam rotation sensitivity has been quantified at 0.016 degs-1/rads-1 and it is demonstrated that this can adequately be estimated using the single beam rotation sensitivity.
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Jackson, Stephen. "Proposed pixel for custom laser Doppler vibrometry camera." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12975/.
Повний текст джерелаАнотація:
Non-destructive testing is an important field of research in many areas of industry and science. This field covers methods that test some property of an object while not impacting its future usefulness. This project is specifically interested in a method of NDE called Laser Doppler Vibrometry (LDV), which uses light to probe the motion of an object's surface. This thesis presents research into the possibility of developing a full-field LDV camera capable of measuring the vibration at a number of points across an object simultaneously. The approach chosen was to develop a single processing element which contained a light detector as well as the processing required to produce an output signal proportional to the vibration of the surface imaged by the element. This processing element, or pixel, could then be used to produce a full-field LDV camera capable of imaging an object's surface to provide vibration amplitude and frequency for a number of points across the whole surface simultaneously Some early work was carried out measuring the vibration of a piezoelectric target with a CMOS camera and the results were compared with theory. The method of processing chosen is called zero-crossing demodulation and a circuit was designed and simulated using this method. This circuit was then laid-out and a CMOS chip was fabricated with the pixel on it. The circuit was designed such that the different parts of it could be tested separately using electrical signals, and a number of electrical tests were performed to check how well the operation of the fabricated pixel compared with simulation. Using a laser interferometer the pixel was finally tested with real vibrating objects and compared with a commercial LDV.
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Abel, Jeffry J. "Three-dimensional velocity extraction using laser Doppler vibrometry." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-12042009-020059/.
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Olsson, Andreas. "Target recognition by vibrometry with a coherent laser radar." Thesis, Linköping University, Department of Electrical Engineering, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1730.
Повний текст джерелаАнотація:
Laser vibration sensing can be used to classify military targets by its unique vibration signature. A coherent laser radar receives the target´s rapidly oscillating surface vibrations and by using proper demodulation and Doppler technique, stationary, radially moving and even accelerating targets can be taken care of.
A frequency demodulation method developed at the former FOA, is for the first time validated against real data with turbulence, scattering, rain etc. The issue is to find a robust and reliable system for target recognition and its performance is therefore compared with some frequency distribution methods. The time frequency distributions have got a crucial drawback, they are affected by interference between the frequency and amplitude modulated multicomponent signals. The system requirements are believed to be fulfilled by combining the FOA method with the new statistical method proposed here, the combination being suggested as aimpoint for future investigations.
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Olsson, Erik. "Digital holographic reconstructions of ultrasound from laser vibrometry recordings /." Luleå, 2004. http://epubl.luth.se/1402-1757/2004/024.
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Halkon, Benjamin John. "Laser Doppler vibrometry for vibration measurements on rotating structures." Thesis, Loughborough University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414974.
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Martins, Rafael Gomes. "Automatic orientation system for a laser vibrometer." Master's thesis, Universidade de Aveiro, 2018. http://hdl.handle.net/10773/23640.
Повний текст джерелаАнотація:
Mestrado em Engenharia MecânicaThe study of material properties, is in many times done by observation of the material behavior under some vibrations. This vibrations can be measure with a laser vibrometer which has a laser beam that measures using the doppler e ect. This device is available at University of Aveiro, but it is a single point vibrometer, which means that the beam direction is the same as the vibrometer, meaning that, to measure another point it is necessary to move the device. To avoid such issue, it was incorporates, on a system on which a device that de ects the laser beam into desirable locations was added. The process of choosing the points is made using a Kinect which acts as a 3D scanner. To de ect the laser beam of the vibrometer, a galvanometer was used which control is made by an Arduino. The Arduino communicates with MATLAB via Serial communication. Several numerical strategies to de ne automatically a measuring mesh are tested in order to identify their limitations and advantages.
O estudo das propriedades dos materiais é muitas vezes realizado a partir da observação do seu comportamento sobre determinados estímulos, tal como vibrações. Estas vibrações podem ser medidas com recurso a um vibrómetro laser sendo que este dispositivo emite um feixe laser e efetua as medições com recurso ao efeito de doppler. Tal dispositivo está disponível na Universidade de Aveiro, sendo este um vibrómetro de ponto único, o que significa que a direção do feixe laser é a direção do vibrómetro, sendo que para obter uma medição noutro ponto é necessário mover o dispositivo. De modo a ultrapassar essa limitação, foi criado um dispositivo onde é incorporado o vibrómetro laser de modo a direcionar o feixe laser para posições pré-definidas. A escolha dos pontos para medição é feita com recurso, a uma câmera Kinect que atua como um scanner 3D. Para deflectir o feixe laser proveniente do vibrómetro foi usado um galvanómetro de espelhos cujo controlo é feito a partir de um Arduino Uno que comunica com o software em MATLAB através de comunicação serie. São analisadas diversas metodologias de definição automática de malha de pontos.
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Cronin, Christopher Joseph. "Digital frequency demodulation for a laser vibrometer." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-11102009-020344/.
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Vybíral, Ondřej. "Analýza slabých stránek laserového 2D vibrometru a jeho vylepšení." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442462.
Повний текст джерелаАнотація:
The master's thesis follows the work of Ing. Tomek, who briefly describes and analyzes the weaknesses of this original solution. Based on the analysis, fixes for vulnerabilities and proposals for new functionalities are proposed. It also describes their implementation and correction of other shortcomings found, including implementation into the original program. The result is better user friendliness of the program and its better functionality. Verification of the functionality of the new improvements is tested using a control measurement of a harmonically excited beam. The last chapter contains suggestions and recommendations for further software development.
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Sharma, Vinod K. "Laser doppler vibrometer for efficient structural health monitoring." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26708.
Повний текст джерелаАнотація:
Thesis (Ph.D)--Aerospace Engineering, Georgia Institute of Technology, 2009.Committee Chair: Hanagud, Sathya; Committee Member: Apetre, Nicole; Committee Member: Engelstad, Steve; Committee Member: Glass, Brian; Committee Member: Kardomateas, George; Committee Member: Ruzzene, Massimo. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Tatar, Kourosh. "Machine tool vibrations and violin sound fields studied using laser vibrometry /." Luleå : Luleå University of Technology, 2006. http://epubl.ltu.se/1402-1757/2006/27/index.html.
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Jones, Janeen Ayana. "Modal analysis on a stiffened panel : an application of laser vibrometry." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/16397.
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Rye, Ryan Patrick. "Investigation of disc brake squeal via sound intensity and laser vibrometry." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/19045.
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Emge, Timothy James II. "Remote nondestructive evaluation of composite-steel interface by acoustic laser vibrometry." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/74902.
Повний текст джерелаАнотація:
Thesis (Nav. E. )--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 70-73).
Composite materials are increasingly being used in both civil and ship structures. In particular, fiber reinforced polymer (FRP) composites are being utilized. FRP materials are most often employed to reinforce aging or damaged portions of civil structures. On naval vessels, FRP materials are incorporated to reduce weight, particularly up high, and to reduce radar cross section, thereby increasing stealth capability. In both cases of FRP use, it is usually in conjunction with some other material, oftentimes steel. It is beneficial when using FRP and steel to adhesively bond them together. When these materials are joined adhesively, the most common failure mode is debonding or delamination at the interface of the adhesive with the steel and composite materials. These defects are often difficult to discern without the aid of some form of nondestructive testing (NDT). Acoustic laser vibrometry is a relatively new method of NDT that shows a lot of promise in analysis of this interface. In this approach, an airborne acoustic wave is utilized to excite the location of the damage underneath the FRP sheets/plates and the target vibration is measured using a laser vibrometer. To study the acoustic laser method, a defect specimen was created from a plate of AL6XN stainless steel and a plate of glass FRP adhesively bonded on their faces with a purposely placed elliptical debonding defect. A number of parameters of the acoustic laser vibrometry system were varied and trends were found. Additionally, grid data was collected from the defect specimen and a defect mapping was created. Theoretical and finite element models were produced and compared to measured results. The close correlation of the results from these three methods validated them all.
by Timothy James Emge, II.
S.M.
Nav.E.
23
Serafini, Stefano. "Quality control agent: self-adaptive laser vibrometry for on line diagnostics." Doctoral thesis, Università Politecnica delle Marche, 2013. http://hdl.handle.net/11566/242695.
Повний текст джерелаАнотація:
In questa tesi verrà descritto come sia possibile aumentare la performance di sistemi di
misura basati sulla vibrometria laser, realizzando dei comportamenti auto-adattativi con lo
scopo di ridurre l’incertezza di misura.
I test sulle vibrazioni sono delle procedure ben note e largamente utilizzate per verificare la
conformità a specifiche di qualità dei prodotti che contengono parti in movimento. Questi
test posti alla fine di una linea di produzione forniscono delle informazioni utili per
descrivere la qualità di un prodotto prima del suo stoccaggio e vendita. Nell’industria
moderna la flessibilità e l’adattabilità sono dei fattori chiave per migliorare l’efficienza del
processo produttivo. Sia il controllo del processo industriale che il controllo qualità
dipendono dalla disponibilità di informazioni affidabili ottenute attraverso i test effettuati
sui prodotti finiti. Grazie alle elevate prestazioni di misura alle sue caratteristiche, la
vibrometria laser Doppler può giocare un ruolo fondamentale permettendo di realizzare
sistemi di misura flessibili che posso contenere algoritmi modulari e che possono attuare (i
sistemi soggetto) procedure auto-adattative.
Questo sistema è stato ottenuto aggiungendo al vibrometro laser a scansione una
telecamera. In questo modo il dispositivo è in grado di vedere e spostare il punto di misura
in posizioni differenti.
In questo sistema sono stati implementati diversi comportamenti auto-adattativi; spostando
il fascio laser è possibile effettuare il riposizionamento del punto di misura sulla lavatrice,
in modo da compensare gli eventuali posizionamenti errati che si hanno sulla linea di
produzione quando la lavatrice in esame viene posizionata sotto il sistema di misura
durante i controlli qualità. Dopo la compensazione di eventuali macro spostamenti della
lavatrice, viene eseguito una fase di ricerca automatica del massimo segnale doppler.
Questa ricerca viene condotta attraverso dei microspostamenti del fascio laser del
vibrometro sulla superficie della vasca della lavatrice attorno al punto di misura
prestabilito. L’obiettivo di questa fase è quello di minimizzare l’incertezza di misura
andando a cercare la regione della superficie che massimizza il segnale Doppler.
Un altro comportamento auto-adattativo consiste nella riconfigurabilità del sistema, cioè la
possibilità di utilizzare differenti algoritmi diagnostici in base alla necessità di effettuare o
meno un’analisi approfondita dell’elettrodomestico. Gli algoritmi scelti si riferiscono ai
diversi scenari produttivi che possono presentarsi all’interno dello stabilimento durante il
funzionamento della linea di produzione. Questo approccio modulare permette di
considerare la realtà della linea produttiva in tutte la sua complessità, permettendo di
svolgere un’analisi diagnostica che tiene in considerazione anche la qualità con cui si sono
svolte le operazioni di assemblaggio della lavatrice che affronta il controllo qualità.
Per poter utilizzare al meglio i comportamenti auto-adattativi, in questa tesi è stata
effettuata una ricerca delle cause di incertezza nella diagnostica industriale, viene mostrato
infatti come il valore RMS del segnale Doppler (signal quality-SQ) è fortemente correlato
all’incertezza di misura. Infatti, maggiore è il decadimento del SQ e tanto più la velocità di
vibrazione risulta essere affetta da incertezza. Gli esperimenti effettuati ci permettono di
dire che durante la vibrazione il valore del SQ è legato alla morfologia della superficie di
misura, e per intervalli di tempo sufficientemente brevi (10-15 secondi), il valore del SQ
dipende solo dalla posizione X-Y del raggio laser sulla superficie di misura. Questi fatti
permettono di utilizzare il valore del SQ(X.Y) come una funzione costo, e la diminuzione
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dell’incertezza di misura è un problema correlato all’ottimizzazione del valore del SQ
durante la misura di vibrazione. Per la strategia di ottimizzazione è stato utilizzato
l’algoritmo di down-hill (Nelder-Mead) e nella tesi vengono discussi i risultati ottenuti sul
SQ dall’applicazione dell’algoritmo.
Con le caratteristiche introdotte, il sistema di misura si trasforma in un Quality Control
Agent (QCA) che diventa parte di un sistema multi-agente (MAS) che ha il compito di
supervisionare l’operato della linea di produzione. In questa tesi vengono mostrati lo
scambio dei dati tra il sistema di misura e gli agenti dando vita ad un sistema produttivo
decentralizzato con caratteristiche di flessibilità e di auto-adattamento.
In modo da poter fornire delle informazioni affidabili agli altri agenti dell’infrastruttura, il
QCA associato al sistema di misura deve avere lapossibilità di capire il grado di confidenza
con cui i risultati della diagnosi vengono calcolati. Per questo motivo è stato concepito e
implementato un modello che permette di stimare il livello di confidenza delle informazioni
diagnostiche estratte dalle caratteristiche del segnale acquisito durante i test. In questo
modo, il QCA può fornire sia il valore globale della diagnosi che stimare il livello di
confidenza con cui la diagnosi è stata effettuata. Le informazioni provenienti dal QCA
vengo elaborate ed utilizzate dall’IMA (indipendent meta agent) per effettuare un controllo
di processo in modo da migliorare l’esecuzione della produzione.Vibration testing is a well established procedure for assessing the conformity to specifications of a variety of products, which contain moving parts. Typically at the end of an assembly line, a vibration test provides useful information for 100% quality control of products before packaging. In the appliance manufacturing sector vibration testing for online quality control is increasingly important. Laser Doppler Vibrometry (LDV) has been already used to perform such tests on-line and it has become an established measurement technique. In modern manufacturing industry flexibility and adaptability are key factors for the improvement of efficiency of production processes; both process control and product quality control depend on the availability of reliable information, and therefore on the quality of the data measured. For its non-contact nature and for its metrologic performance, laser vibrometry plays a more and more important and crucial role. This technique allows to realize flexible measurement systems that can implement adaptive and modular algorithms, comprising a large number of ready to use tools. In this thesis we will describe how it is possible to improve the performance of such systems by implementing self-adaptation and reconfigurability behaviors of the laser vibrometer aimed to reduce measurement uncertainty. Such behaviors are achieved by adding scanning mirrors and a dedicated camera, thus realizing a scanning LDV, which can displace the measurement beam at different locations. Self-adaptation (local adaptation) consists in the following behaviors: the system aims at the desired target point over the washing machine (WM) by displacing the laser beam so to compensate effects of WM mis-positioning due to production line inaccuracies. After this preliminary phase, the automatic search for sufficiently large Doppler signal starts. The system searches for an optimal optical signal by slightly displacing the laser beam in the surrounding of the desired target point thus optimizing measurement uncertainty. The system can support also reconfigurability (global adaptation), which consists in the possibility to plug-in/plug-out different post-processing algorithms for a deeper analysis of vibrations. For different production scenarios different diagnostic algorithms are chosen. This modular approach allows to consider the scenario of the production line and the quality of the operations carried out on the production line before the end product is made. In order to successfully use the self adaptation behavior to increase measurement accuracy, for this thesis a deep research of the causes correlated to uncertainty in industrial diagnostic has been made. It this work it is shown how the RMS amplitude of the Doppler signal (signal quality - SQ) is strictly correlated to measurement uncertainty, when SQ decreases then uncertainty affects the vibration velocity signal. Experimental data allow to say that SQ value is correlated to the morphology of the target surface and for a short period of time (10-15 s), so during the vibration the SQ value depends only on X-Y position of the laser beam on the target surface. These facts allow to use the SQ function as a cost function and the decrease the measurement uncertainty is a problem correlated to the optimization of the SQ value during the vibration measurements. The optimization strategy for the measurement enhancement achieved by the down-hill algorithm (Nelder-Mead algorithm) and its effect on signal quality (SQ) improvement are discussed. ii With these features, this system is designed as a Quality Control Agent (QCA) and it is part of a Multi Agent System (MAS) that supervises all the production line. This thesis also shows the data exchange between the measurement system and other agents in order to realize a decentralized manufacturing system. In fact, in a distributed system, the estimation of the confidence level of the information provided by other agents plays an important role. The QCA associated to the measurement system has to be able to understand the confidence level of the diagnostic results provided. To understand the confidence level of the diagnostic information extracted from a feature, an uncertainty estimate model applied to a vibration signal acquired from a washing machine has been conceived and implemented. In this way, the QCA can provide the overall diagnosis for the WM and estimate the uncertainty level with which the diagnosis has been performed. These information are used by the independent meta agent (IMA) to perform a trend analysis and elaborate suggestions and warnings to improve the process and product execution.
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Ševčík, Michal. "Nanometrologická vibrometrie." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-220217.
Повний текст джерелаАнотація:
This thesis deals with the precise measurement of distances in nanometer range at ultrasonic frequencies for the purposes of vibrometry. The paper is primary focused on~nanometric displacement measurement methods. First the thesis deals with the physical phenomena based on light in the theoretical section. This includes interference of light, index of refraction, polarization, interferometry and more. Understanding of these physical laws is crucial for design and assembling of the interferometer. Subjects of interferometric method for precise and fast measurement of the nanometric displacement and vibration are discussed. Interferometer components such as lasers, photodetectors and optical elements are described are described in the final part of this section. Practical section of thesis can be divided into two parts. The design and assembling issues are discussed in the first section. Many problems which I had to solve are described. Control software and implementation of the signal processing is the subject of the second part. I met with particular problems such as phase unwrapping. I solved this problem of discontinuous phase field with user written algorithm. Finally the graphical user interface was created. Using assembled interferometer and written software application I measured vibration of Langevin transducer on ultrasonic frequencies.
25
Zima, Andrew David Jr. "Misalignment Effects of the Self-Tracking Laser Doppler Vibrometer." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/32471.
Повний текст джерелаАнотація:
There are many limitations to the current methods used to measure vibration on rotating structures. These limitations include physical flow blockages, relating the measurement spot to the structure rotation, data processing issues, and having to physically alter the engine. This work further describes aspects of a self-tracking laser vibrometry system that can be used to measure the vibrations of rotating structures. This method, if setup correctly, has the capability to overcome many of the limitations listed above. A study of all misalignment effects is presented in this thesis. The study consists of a parametric sensitivity analysis of misalignment variables, a parametric Monte Carlo analysis of misalignment variables, and a full interaction Monte Carlo analysis of misalignment variables. In addition, the results of the misalignment variable analyses were used to develop a self-tracker test rig for obtaining fan vibration from a Pratt and Whitney JT15D turbofan engine. A prototype this test rig was designed, built, and tested on the turbofan. It was found that in order to achieve acceptable amounts of position and velocity error using the self-tracker LDV system, very strict alignment of the optical equipment is necessary. Additionally, the alignment criteria can likely be achieved with the use of digitally controlled high precision linear motion equipment.Master of Science
26
Salman, Muhammad. "Continuous scanning laser doppler vibrometry for synchronized array measurements: applications to non-contact sensing of human body vibrations." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45792.
Повний текст джерелаАнотація:
Laser Doppler Vibrometry (LDV) is a non-contact technique for sensing surface vibrations. Traditionally, LDV uses one or more fixed beams to measure the vibrational velocity of specific points and orientations. In order to measure an angular velocity at least two laser beams are required. Instead, this research proposes to develop a Continuous Scanning Laser Doppler Vibrometer (CSLDV) technique, based on a single laser beam continuously sweeping the area of interest using a scanning mirror. Linear scans allow the measurement of normal and angular velocity while circular scans allow the measurement of normal velocity and two angular velocities. The first part of the study analyzes the performance of rigid body models of both the short line and circular scans (< 1 cm) for measuring low broadband frequency vibrations of gel samples. This thesis focused on low frequency broadband vibration since natural human body vibrations (such as tremor or breathing) are typically below a few hundred hertz. Results for normal and angular velocity measurements are validated against conventional method of using two fixed LDVs. The second part of this research investigates the CSLDV technique for longer scans (< 5 cm). These long scans will be used to act as an array of virtual transducers at multiple points along the scanning path of the single laser beam; thus yielding similar information obtained using an array of several real fixed LDVs. A practical challenge encountered when using CSLDV is speckle noise, that is generated when a coherent light source is reflected back from an optically rough surface. The effect of speckle noise will be quantified by varying different parameters such as scan lengths, scanning frequency, target to sensor distance and the amplitude of excitation. These parameters will be optimized in order to reduce the error of vibration measurements obtained from the CSLDV. Such systems will be used to monitor multiple degrees of freedom of human skeletal muscle vibrations for elastography purposes. The forced vibration of human muscles will be analyzed using these CSLDV techniques.
Overall contributions of this work include: (1) Validation of rigid body models of both short line and circular scans CSLDV for broadband low frequency linear and angular velocity measurements; (2) application to sensing natural human body vibrations (e.g., hand tremors); (3) replacement of an array of vibration sensors by a single long line scan CSLDV. (4) development of a dynamic elastography technique for skeletal muscles using CSLDV.
27
Harvey, David. "Automatically phase-locked fibre optic electronic speckle pattern interferometry using laser vibrometry." Thesis, Heriot-Watt University, 1996. http://hdl.handle.net/10399/715.
Повний текст джерела
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Pavloň, Martin. "Analýza dynamických parametrů laserových vibrometrů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-316221.
Повний текст джерелаАнотація:
This diploma thesis deals with the theoretical description of interference methods used to measure vibrations, examines main parasitic effects and analyses its contribution to achievable the resolution. In the practical part, it uses several measurements to verify the effects of the level of reflected beam, stand-off distance and speckle noise. It also proposes a practical experiment for measuring dynamic parameters and signal-noise ratio. Results show that, the noise is exponentially dependent on the level of the reflected beam. The visible maximum of the vibrometer proved to be critical in terms of time stability of the measured signal level in two of the three measurements. Results of the dynamic measurement show that, the measured deviations were not degraded or significantly disturbed by the noise signal. From the measurement of the speckle noise, it emerged that the lowest level of noise is achieved with smooth and highly reflective materials.
29
Martarelli, Milena. "Exploiting the laser scanning facility for vibration measurements." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248035.
Повний текст джерела
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Donovan, Joseph Brian. "Three-dimensional vibrometry via three positions of a one-dimensional laser doppler velocimeter." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-08142009-040347/.
Повний текст джерела
31
Strean, R. Flynt. "Characterization of laser noise in free-free beam structures using a Scanning Laser Doppler Vibrometer." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-02132009-171026/.
Повний текст джерела
32
Chen, Justin Gejune. "Detection of defects in FRP-reinforced concrete with the acoustic-laser vibrometry method." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79423.
Повний текст джерелаАнотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 165-168).
Fiber-reinforced polymer (FRP) strengthening and retrofitting of concrete structural elements has become increasingly popular for civil infrastructure systems. When defects occur in FRP-reinforced concrete elements at the FRP-concrete interface, such as voids or delamination, FRP obscures the defect such that visual detection may not be possible. Most currently available non-destructive testing (NDT) methods rely on physical contact; an NDT method that is capable of remotely assessing damage would be greatly advantageous. A novel approach called the acoustic-laser vibrometry method which is capable of remote assessment of damage in FRP-reinforced concrete, is investigated in this thesis. It exploits the fact that areas where the FRP has debonded from concrete will vibrate excessively compared to intact material. In order to investigate this method, a laboratory system consisting of a commercial laser vibrometer system and conventional loudspeaker was used to perform tests with fabricated FRP-reinforced concrete specimens. The measurement results in the form of resonant frequencies were compared to those determined from theoretical and finite element defect models. With a series of measurements the vibrational mode shapes of defects and extent of the damage were imaged. The feasibility of the method was determined through a series of parametric studies, including sound pressure level (SPL), defect size, laser signal level, and angle of incidence. A preliminary Receiver Operating Characteristic (ROC) curve was determined for the method, and future work involving the acoustic-laser vibrometry method is proposed.
by Justin Gejune Chen.
S.M.
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Blotter, Jonathan D. "Structural energy and power flow using a scanning laser Doppler vibrometer." Diss., This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-06062008-151157/.
Повний текст джерела
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Lomenzo, Richard Allan Jr. "Static Misalignment Effects is a Self-Tracking Laser Vibrometry System for Rotating Bladed Disks." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/29398.
Повний текст джерелаАнотація:
The application of laser Doppler vibrometry to high speed rotating structures has been hampered by technical limitations. Whereas full-field three-dimensional velocity measurements can be made on stationary structures, the capability on rotating structures is limited to low speed, one-dimensional, steady state operation. This work describes the implementation of a self-tracking laser vibrometry system which overcomes many of the limitations of current techniques for vibration measurements on rotating structures. A model of the self-tracker is developed and used to predict the effects of static misalignments on the position and velocity errors. These predictions are supported by experimental results and simplified models of the self-tracker.
NOTE: (02/2011) An updated copy of this ETD was added after there were patron reports of problems with the file.Ph. D.
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Schmidtchen, Silja [Verfasser]. "Aufbau eines Laser-Vibrometer-Messsystems zur Hochtemperatur-Charakterisierung von Sensorkomponenten / Silja Schmidtchen." Clausthal-Zellerfeld : Universitätsbibliothek Clausthal, 2014. http://d-nb.info/104959147X/34.
Повний текст джерела
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Gürtler, Johannes, Felix Greiffenhagen, Jakob Woisetschläger, Daniel Haufe, and Jürgen Czarske. "Non-invasive seedingless measurements of the flame transfer function using high-speed camerabased laser vibrometry." SPIE, 2017. https://tud.qucosa.de/id/qucosa%3A34893.
Повний текст джерелаАнотація:
The characterization of modern jet engines or stationary gas turbines running with lean combustion by means of swirl-stabilized ames necessitates seedingless optical field measurements of the ame transfer function, i.e. the ratio of the uctuating heat release rate inside the ame volume, the instationary ow velocity at the combustor outlet and the time average of both quantities. For this reason, a high-speed camera-based laser interferometric vibrometer is proposed for spatio-temporally resolved measurements of the ame transfer function inside a swirl-stabilized technically premixed ame. Each pixel provides line-of-sight measurements of the heat release rate due to the linear coupling to uctuations of the refractive index along the laser beam, which are based on density uctuations inside the ame volume. Additionally, field measurements of the instationary ow velocity are possible due to correlation of simultaneously measured pixel signals and the known distance between the measurement positions. Thus, the new system enables the spatially resolved detection of the ame transfer function and instationary ow behavior with a single measurement for the first time. The presented setup offers single pixel resolution with measurement rates up to 40 kHz at an maximum image resolution of 256 px x 128 px. Based on a comparison with reference measurements using a standard pointwise laser interferometric vibrometer, the new system is validated and a discussion of the measurement uncertainty is presented. Finally, the measurement of refractive index uctuations inside a ame volume is demonstrated.
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Casaccia, Sara. "Measurement of physiological parameters in the human body by non-contact technique: Laser Doppler Vibrometry." Doctoral thesis, Università Politecnica delle Marche, 2015. http://hdl.handle.net/11566/243056.
Повний текст джерелаАнотація:
La misura senza contatto di segnali fisiologici e vitali ѐ uno dei fattori di maggior rilievo per la strumentazione biomedicale di nuova generazione. I metodi di misura con contatto di parametri fisiologici presentano dei limiti come l’invasività con la pelle, l’impossibilità di poter applicare gli elettrodi in particolari regioni corporee o in parti del corpo ristrette ed ѐ necessaria la collaborazione del soggetto. Per queste ragioni la Vibrometria Laser Doppler (LDV) ѐ stata introdotta per acquisire segnali associati all’attività biologica del corpo umano, per eliminare il contatto con la pelle e per rendere le prove più semplici.
Questa tesi di dottorato si focalizza sull’utilizzo dell’LDV per la misura dell’attività cardiovascolare e muscolare in quanto sono parametri che permettono una valutazione dello stato di salute ed emozionale del soggetto sotto esame. Infatti, nella pratica clinica e giornaliera ѐ fondamentale la valutazione dei segnali vitali ed emozionali e la tecnologia LDV ha la capacità di misurare i movimenti vibrazionali della superficie corporea senza contatto, con una elevata sensibilità di acquisizione e ad una distanza notevole.
Questo lavoro ha lo scopo di esplorare e dimostrare le capacità della Vibrometria Laser Doppler nel misurare la frequenza cardiaca con una incertezza di ± 9 ms rispetto alla tecnica convenzionale (elettrocardiografia) ed altri parametri cardiovascolari puntando il fascio laser sulla carotide.
Infine, LDV viene usato anche per la misura delle proprietà di contrazione muscolare dei grandi e piccoli muscoli (muscoli facciali) con una accuratezza elevata sempre in confronto alla tecnica considerata gold standard (elettromiografia di superficie).
La tecnica LDV, senza contatto, può dunque sostituire le tecnologie convenzionali, più invasive che richiedono l’applicazione di sensori sulla pelle del paziente e in questo modo si possono ottenere misurazioni di parametri cardiovascolari e muscolari completamente senza contatto andando a migliorare la qualità delle prove come interrogatori, controlli di sicurezza, controlli clinici e programmi di riabilitazione.The measurements of physiological and vital signals without contact is a relevant research issue in modern biomedical instrumentation. Contact methods presently used to measure physiological parameters sometimes can be inconvenient or inadequate for patient comfort or to detect signals from particular body regions and the presence of cables is a limit for the patient mobility. For these reasons, the Laser Doppler Vibrometry (LDV) technique was introduced to acquire signals associated with biological activity in the human body, to avoid the contact with the skin and to make the tests easiest. This dissertation is focused on the novel use of LDV to measure cardiovascular and muscular activity to evaluate health and emotional state of participants. In fact, in daily and clinical practice is fundamental the assessment of vital and emotional signals and the LDV technique has the capability to measure the vibrational movements of the skin surface without contact, with a high sensitivity of acquisition and at a distance of several meters. In this work, the possibility to use LDV to measure the heart rate, with a deviation of ± 9 ms from the conventional gold standard method (electrocardiography) and other cardiovascular parameters assessed from the carotid artery are measured with LDV, will be explored and demonstrated. Finally, LDV is used to measure muscle contraction properties from the big and small muscles (facial muscles) with a high accuracy in confront of the gold standard method (surface electromyography). Using the non-contact LDV technique might provide surrogate measures for those obtained using conventional, more obtrusive assessment methods that require attached sensors and so, measurements of cardiovascular and muscular parameters without contact can improve tests as investigations, safety controls, clinical controls, rehabilitation programs.
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Siethoff, Eric Ten. "A Formulation for Updating Finite Element Models Through Consistent Use of Laser Vibrometer Data." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36704.
Повний текст джерелаАнотація:
This thesis suggests a formulation for updating physically meaningful parameters in analytical finite element(FE) models using scanning laser Doppler vibrometer(SLDV) dynamic response data. The update formulation is demonstrated in several computer simulations.
The formulation is the result of incorporating an analytical FE model into an experimental model. The experimental model efficiently utilizes SLDV data to fully exploit the instrument's capability to automatically make measurements at many locations. The data in the experimental model is posed in a manner consistent with an analytical FE model's representation for harmonic response, simplifying comparison between the two. The experimental model, which uses finite element shape functions as a basis for a least squares fit to the data, can be solved to give a velocity field based only on that data. The function resulting from inserting the analytical model into the experimental model is an expression of the prediction error of the FE model as compared to the test data. This function is minimized using a quasi-Newton optimization routine, reducing the error and resulting in an updated model.
Computer simulations of the update algorithm indicate that:
1. Analytically supplied derivatives and variable scaling are required by the optimization routine to consistently converge,
2. The percentage error of updated parameters falls within two standard deviations of the data's percentage error,
3. Error in the position of the laser results in the update algorithm's failure, and,
4. Error in the parameters not included in the update will appear as error in the updated parameters' solution.Master of Science
39
Jin, Si. "Structural damage detection using higher-order finite elements and a scanning laser vibrometer /." free to MU campus, to others for purchase, 2000. http://wwwlib.umi.com/cr/mo/fullcit?p9974641.
Повний текст джерела
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Miles, Toby J. "New development in experimental analysis of torsional vibration for rotating shaft systems." Thesis, Loughborough University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389773.
Повний текст джерела
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Avosani, Sabina. "Behaviour, ecology, and vibrational manipulation of insect vectors: the case of the meadow spittlebug Philaenus spumarius, with notes on a psyllid pest." Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/319182.
Повний текст джерелаАнотація:
Insects can cause economic and environmental damages by transmitting bacterial pathogens to plants, making the use of control and prevention measures imperative. On the other hand, methods aimed at preventing crop pests’ outbreaks, such as tilling and insecticide applications, pose a threat to human and ecosystems health. Innovative and more sustainable control methods are therefore urgently needed to address farmers’ needs and preserve ecosystem services provided by biodiversity. Biotremology is an emerging science that studies the substrate-borne vibrational signals emitted by insects to communicate and interact with their others in the environment. As many insect pests rely on these signals to communicate, their behaviour can be manipulated by transmitting vibrations to the substrate where they thrive. Vibrational signals can, for instance, interfere with target’s behaviours such as mating, feeding, and residence time on the plant, and can therefore support integrated pest management strategies alternative to insecticides. In this work, I investigated the mating behaviour and vibrational communication of two insect vectors having an important economic impact: Philaenus spumarius (Hemiptera: Aphrophoridae) and Bactericera cockerelli (Hemiptera: Triozidae). I also provided novel insights regarding the vibrational manipulation of their behaviour. I characterised the sexual behaviour and associated vibrational signals of the meadow spittlebug P. spumarius, and I described other intraspecific interactions. I evaluated the correlation between the female signalling activity and development of the reproductive organs, suggesting that a vibrational mating disruption could be effective only if applied from the onset of egg maturation, which triggers the female proceptivity (from August onwards). Besides gathering behavioural data, I used occupancy models to estimate P. spumarius presence and detection probability in Trentino (Northern Italy), a rarely deployed approach to study insect distribution. Site covariates impacted P. spumarius detectability, suggesting that spittlebug presence can be overlooked if detection is not considered. As plant composition influences the presence and abundance of the spittlebug, I studied the association between P. spumarius and its host plants. Such information can support monitoring programs and control strategies aimed at reducing P. spumarius population in crops of interest by shaping the plant composition of the ground cover. After investigating the behaviours and the ecology of the spittlebug, I attempted to disrupt its feeding activity using vibrations, opening the gates for future research. In this regard, I combined for the first time biotremology with the Electrical Penetration Graph (EPG) technique. The tomato potato psyllid B. cockerelli is an important threat to New Zealand crops. Besides the characterisation of the pair formation process and associated vibrational signals, I used vibrations to disrupt mate finding by transmitting vibrations to the host plant. Given that the stimulus attracted male psyllids at small scale, this strategy is a feasible approach that could be implemented for use in fields and greenhouses. In this way, an innovative trapping and mating disruption device could join the farmers’ toolbox for monitoring and controlling B. cockerelli. In conclusion, I provided new information regarding the ethology of two insect vectors and suggested that there is room for applied biotremology to support sustainable management strategies.
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Avosani, Sabina. "Behaviour, ecology, and vibrational manipulation of insect vectors: the case of the meadow spittlebug Philaenus spumarius, with notes on a psyllid pest." Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/319182.
Повний текст джерелаАнотація:
Insects can cause economic and environmental damages by transmitting bacterial pathogens to plants, making the use of control and prevention measures imperative. On the other hand, methods aimed at preventing crop pests’ outbreaks, such as tilling and insecticide applications, pose a threat to human and ecosystems health. Innovative and more sustainable control methods are therefore urgently needed to address farmers’ needs and preserve ecosystem services provided by biodiversity. Biotremology is an emerging science that studies the substrate-borne vibrational signals emitted by insects to communicate and interact with their others in the environment. As many insect pests rely on these signals to communicate, their behaviour can be manipulated by transmitting vibrations to the substrate where they thrive. Vibrational signals can, for instance, interfere with target’s behaviours such as mating, feeding, and residence time on the plant, and can therefore support integrated pest management strategies alternative to insecticides.
In this work, I investigated the mating behaviour and vibrational communication of two insect vectors having an important economic impact: Philaenus spumarius (Hemiptera: Aphrophoridae) and Bactericera cockerelli (Hemiptera: Triozidae). I also provided novel insights regarding the vibrational manipulation of their behaviour.
I characterised the sexual behaviour and associated vibrational signals of the meadow spittlebug P. spumarius, and I described other intraspecific interactions. I evaluated the correlation between the female signalling activity and development of the reproductive organs, suggesting that a vibrational mating disruption could be effective only if applied from the onset of egg maturation, which triggers the female proceptivity (from August onwards). Besides gathering behavioural data, I used occupancy models to estimate P. spumarius presence and detection probability in Trentino (Northern Italy), a rarely deployed approach to study insect distribution. Site covariates impacted P. spumarius detectability, suggesting that spittlebug presence can be overlooked if detection is not considered. As plant composition influences the presence and abundance of the spittlebug, I studied the association between P. spumarius and its host plants. Such information can support monitoring programs and control strategies aimed at reducing P. spumarius population in crops of interest by shaping the plant composition of the ground cover. After investigating the behaviours and the ecology of the spittlebug, I attempted to disrupt its feeding activity using vibrations, opening the gates for future research. In this regard, I combined for the first time biotremology with the Electrical Penetration Graph (EPG) technique.
The tomato potato psyllid B. cockerelli is an important threat to New Zealand crops. Besides the characterisation of the pair formation process and associated vibrational signals, I used vibrations to disrupt mate finding by transmitting vibrations to the host plant. Given that the stimulus attracted male psyllids at small scale, this strategy is a feasible approach that could be implemented for use in fields and greenhouses. In this way, an innovative trapping and mating disruption device could join the farmers’ toolbox for monitoring and controlling B. cockerelli.
In conclusion, I provided new information regarding the ethology of two insect vectors and suggested that there is room for applied biotremology to support sustainable management strategies.
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Willis, Richard Lance. "Non-invasive characterization of microvoided polymers under controlled static pressure and temperature using laser doppler vibrometry." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/17248.
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Carns, Jennifer. "Semiconductor Optical Amplifier as a Phase Modulator for Short-Pulse Synthetic Aperture Ladar and Vibrometry." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1335278035.
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Lin, Ye Hone. "Evaluation of vibration responses of ceramic candle filters using an accelerometer and a laser vibrometer." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1369.
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Dupuis, Joseph. "Ground vibration testing of airplane pylon-store dynamics using laser Doppler vibrometer and accelerometer techniques." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0000677.
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CASACANDITELLA, LUIGI. "Development of a measurement procedure for the assessment of carotid blood pressure by means of Laser Doppler Vibrometry." Doctoral thesis, Università Politecnica delle Marche, 2017. http://hdl.handle.net/11566/245446.
Повний текст джерелаАнотація:
L'ipertensione è uno dei principali fattori di rischio per numerose patologie, quali infarto del miocardio, insufficienza cardiaca e renale, ictus, e rappresenta la principale causa di morte al Mondo.
Risulta, pertanto, fondamentale il monitoraggio della pressione arteriosa nell'ambito della prevenzione dell'insorgere di gravi patologie.
Lo scopo del presente lavoro è di validare una procedura di misura per la determinazione della pressione arteriosa carotidea mediante la tecnica della vibrometria Laser Doppler (LDV).
Essa è una tecnica di misura senza contatto ad elevata sensibilità, in grado di rilevare le vibrazioni della pelle legate all'attività cardiovascolare.
Nel presente lavoro, il segnale LDV è stato acquisito su 28 soggetti sani ed è stato calibrato per mezzo di un opportuno modello matematico esponenziale per ottenere la forma d'onda di pressione carotidea a partire dallo spostamento del vaso sanguigno.
I risultati ottenuti sono stati confrontati con due tecniche di riferimento, la sfigmomanometria e la tonometria arteriosa.
La pressione sistolica ottenuta dal segnale LDV calibrato ha mostrato una deviazione percentuale inferiore del 4% e del 8 % rispetto a quella ottenuta tramite cuffia sfigmomanometrica e tonometria rispettivamente. L'integrazione del segnale e l'applicazione di un modello di calibrazione sono state considerate quali significative fonti di incertezza, e si è stimata un'incertezza complessiva di circa il 15 % nella misura della pressione sistolica.
Dal segnale LDV sono stati determinati altri significativi parametri emodinamici quali il tempo di eiezione del ventricolo sinistro e la rigidità arteriosa.
In conclusione, la tecnica di misura proposta mostra buona correlazione con i metodi di misura di riferimento, benchè vadano prese in considerazione alcune criticità quali l'individuazione del punto di misura, la presenza di artefatti da movimento e di fenomeni di riflessione non legati all'impulso pressorio oggetto di studio.High blood pressure is a great risk factor for several physiological diseases, i.e. myocardial infarction, heart failure, stroke, renal failure. Therefore, blood pressure measurement is a fundamental aspect of health monitoring. The aim of the present work is to validate a measurement procedure for the assessment of carotid blood pressure by means of Laser Doppler Vibrometry (LDV). LDV is a non-contact technique able to detect the skin vibrations due to the cardiovascular activity. In this study, LDV signal was acquired from 28 healthy participants and it was calibrated by means of an exponential mathematical model in order to obtain the carotid pressure waveform from the displacement of the vessel. The results have been compared with two standard techniques for the assessment of blood pressure, sphygmomanometric method and arterial applanation tonometry. The systolic peak of the calibrated waveform from LDV showed an average percentage deviation inferior to 10 % from the one assessed by means of reference techniques. The accuracy of the present measurement technique is discussed, considering the signal integration and the application of the calibration model as significant contributions to the total amount of uncertainty. An average percentage uncertainty of around 15 % has been obtained in the measure of carotid systolic pressure. Moreover, other hemodynamic significant parameters, such as arterial stiffness and Left Ventricular Ejection Time, have been derived from LDV data, showing good correlation with the measures of the reference methods. In conclusion, the proposed measurement technique, for the assessment of carotid blood pressure, shows good agreement with the reference techniques. Overall, some critical issues must be considered, such as the correct localization of the measurement point, the presence of movement artifacts and reflection phenomena not related to the pressure pulse in the investigated vessel.
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Dussarrat, Olivier Jerome. "An investigation of an amplitude-locked loop in the demodulation circuitry of a laser vibrometer system." Thesis, University of the West of Scotland, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.446038.
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Zeng, Xiandi. "The estimation and statistical inferences of the position and orientation of a scanning laser Doppler vibrometer." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-10302008-063011/.
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Li, Jingxuan. "Development of novel diagnostic techniques to measure heat release rate perturbations in flames." Phd thesis, Ecole Centrale Paris, 2012. http://tel.archives-ouvertes.fr/tel-00997413.
Повний текст джерелаАнотація:
Heat release rate disturbances are the sources of additional thermal stresses, direct and indirect combustion noise and undesirable vibrations. In extreme cases, these perturbations may even cause destructive combustion instabilities. These quantities are difficult to measure in practical burners. The objective of this work is to develop two alternative diagnostics to measure heat release rate fluctuations in unsteady flames. These techniques are validated in generic configurations for perfectly premixed laminar flames. The first method is an acoustic technique, which is based on the measurement of the travel time of ultrasonic waves through the flames. Fluctuations of the sound propagation time transmission through unsteady flames are used to estimate perturbations in the burned gases width along the acoustic path. This information is then used to reconstruct heat release rate fluctuations. This technique is validated in the cases of unstable laminar premixed flames driven by buoyancy forces and for flames submitted to harmonic flow velocity modulations. Analytical expressions are derived linking fluctuations in heat release rate and disturbances of the sound travel time. Measurements made with this acoustic technique are compared with optical detections based on the flame chemiluminescence and with predictions from an analytical model. Good agreements are obtained between these different methods validating the proposed technique. The second method envisaged is an optical technique based on a Laser Interferometric Vibrometer used to measure integrated density perturbations along the optical path of a laser beam. It is shown that density disturbances along this path result mainly from heat release rate fluctuations when the flames are confined. A link is established to reconstruct heat release rate disturbances from the signal of the interferometer. The technique is validated in the case of pulsated laminar premixed flames. Measurements are compared to line-of-sight integrated chemiluminescence emission measurements. A good agreement is obtained for harmonic flow modulations at different forcing frequencies and perturbation levels for flames operating at different flow conditions. This work validates the principle of this alternative technique for detecting heat release rate perturbations.