Letteratura scientifica selezionata sul tema "Passive vibration filtering"
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Articoli di riviste sul tema "Passive vibration filtering"
1
Mir, Fariha, Debdyuti Mandal e Sourav Banerjee. "Metamaterials for Acoustic Noise Filtering and Energy Harvesting". Sensors 23, n. 9 (23 aprile 2023): 4227. http://dx.doi.org/10.3390/s23094227.
Testo completoAbstract (sommario):
Artificial methods for noise filtering are required for the twenty-first century’s Factory vision 4.0. From various perspectives of physics, noise filtering capabilities could be addressed in multiple ways. In this article, the physics of noise control is first dissected into active and passive control mechanisms and then further different physics are categorized to visualize their respective physics, mechanism, and target of their respective applications. Beyond traditional passive approaches, the comparatively modern concept for sound isolation and acoustic noise filtering is based on artificial metamaterials. These new materials demonstrate unique interaction with acoustic wave propagation exploiting different physics, which is emphasized in this article. A few multi-functional metamaterials were reported to harvest energy while filtering the ambient noise simultaneously. It was found to be extremely useful for next-generation noise applications where simultaneously, green energy could be generated from the energy which is otherwise lost. In this article, both these concepts are brought under one umbrella to evaluate the applicability of the respective methods. An attempt has been made to create groundbreaking transformative and collaborative possibilities. Controlling of acoustic sources and active damping mechanisms are reported under an active mechanism. Whereas Helmholtz resonator, sound absorbing, spring-mass damping, and vibration absorbing approaches together with metamaterial approaches are reported under a passive mechanism. The possible application of metamaterials with ventilation while performing noise filtering is reported to be implemented for future Smart Cities.
2
Asiri, S., A. Baz e D. Pines. "Periodic Struts for Gearbox Support System". Journal of Vibration and Control 11, n. 6 (giugno 2005): 709–21. http://dx.doi.org/10.1177/1077546305052784.
Testo completoAbstract (sommario):
Passive periodic structures exhibit unique dynamic characteristics that make them act as mechanical filters for wave propagation. As a result, waves can propagate along the periodic structures only within specific frequency bands called “pass bands” and wave propagation is completely blocked within other frequency bands called “stop bands”. In this paper, the emphasis is placed on developing a new class of these periodic structures called passive periodic struts, which can be used to support gearbox systems on the airframes of helicopters. When designed properly, the passive periodic strut can stop the propagation of vibration from the gearbox to the airframe within critical frequency bands, consequently minimizing the effects of transmission of undesirable vibration and sound radiation to the helicopter cabin. The theory governing the operation of this class of passive periodic struts is introduced and their filtering characteristics are demonstrated experimentally as a function of their design parameters. The presented concept of the passive periodic strut can be easily used in many applications to control the wave propagation and the force transmission in both the spectral and spatial domains in an attempt to stop/confine the propagation of undesirable disturbances.
3
Guan, Haofei, e K. C. Wong. "Spring-Damped Underactuated Swashplateless Rotor on a Bicopter Unmanned Aerial Vehicle". Machines 12, n. 5 (28 aprile 2024): 296. http://dx.doi.org/10.3390/machines12050296.
Testo completoAbstract (sommario):
The stabilisation capabilities of unmanned aerial vehicles (UAVs) with bicopter underactuated swashplateless rotors are highly sensitive to motor-induced vibration. Due to the requirement of the active control of underactuated swashplateless rotors, conventional designs are limited in reducing vibration through control optimisation. A solution with customized passive spring-damping structures on a unique underactuated swashplateless rotor of a tiltrotor bicopter platform is presented. The implementation of this structure effectively reduces the self-coherent vibration in flights. As a result, a higher level of control authority has been achieved without setting excessive low-pass filtering for vibration. Experimentally obtained inertial measurement unit (IMU) data, rotor speed, rotor tilt angle, and the cyclic stator response are presented for comparison with Simulink model predictions.
4
Baz, A. "Active Control of Periodic Structures". Journal of Vibration and Acoustics 123, n. 4 (1 giugno 2001): 472–79. http://dx.doi.org/10.1115/1.1399052.
Testo completoAbstract (sommario):
Conventional passive periodic structures exhibit unique dynamic characteristics that make them act as mechanical filters for wave propagation. As a result, waves can propagate along the periodic structures only within specific frequency bands called the “Pass Bands” and wave propagation is completely blocked within other frequency bands called the “Stop Bands.” In this paper, the emphasis is placed on providing the passive structures with active control capabilities in order to tune the spectral width and location of the pass and stop bands in response to the structural vibration. Apart from their unique filtering characteristics, the ability of periodic structures to transmit waves, from one location to another, within the pass bands can be greatly reduced when the ideal periodicity is disrupted resulting in the well-known phenomenon of “Localization.” In the case of passive structures, the aperiodicity (or the disorder) can result from unintentional material, geometric and manufacturing variability. However, in the case of active periodic structures the aperiodicity is intentionally introduced by proper tuning of the controllers of the individual substructure or cell. The theory governing the operation of this class of Active Periodic structures is introduced and numerical examples are presented to illustrate their tunable filtering and localization characteristics. The examples considered include periodic/aperiodic spring-mass systems controlled by piezoelectric actuators. The presented results emphasize the unique potential of the active periodic structures in controlling the wave propagation both in the spectral and spatial domains in an attempt to stop/confine the propagation of undesirable disturbances.
5
Alajlouni, Sa’ed, e Pablo Tarazaga. "A passive energy-based method for footstep impact localization, using an underfloor accelerometer sensor network with Kalman filtering". Journal of Vibration and Control 26, n. 11-12 (21 gennaio 2020): 941–51. http://dx.doi.org/10.1177/1077546319890520.
Testo completoAbstract (sommario):
An underfloor accelerometer sensor network can be used to track occupants in an indoor environment using measurements of floor vibration induced by occupant footsteps. To achieve occupant tracking, each footstep impact location must first be estimated. This paper proposes a new energy-based algorithm for footstep impact localization. Compared to existing energy-based algorithms, the new algorithm achieves higher localization accuracy and removes a previously required calibration step (removal of the need to estimate floor-dependent parameters). Furthermore, the algorithm uses a much smaller data sampling rate compared to time of flight/arrival localization methods, which greatly reduces data and data-processing time. The new algorithm is a two-step location estimator: the first step is a coarse location estimate, with the second step as a fine location search through a nonlinear minimization problem. The performance of the proposed algorithm is evaluated using a single occupant walking experiment on an instrumented floor inside an operational smart building. This paper also demonstrates that higher localization accuracy is obtained using an additional Kalman filtering scheme.
6
Li, Jianying, Yunchang Xiao, Minsheng Yang, Jianqi Li e Jingying Wan. "The Research on Harmonic Transfer Characteristics of Integrated Multi-Winding Inductive Filtering Converter Transformer and Its Filter System". Electronics 11, n. 13 (3 luglio 2022): 2088. http://dx.doi.org/10.3390/electronics11132088.
Testo completoAbstract (sommario):
A novel integrated multi-winding inductive filter converter and its filter system used in HVDC conversion station are proposed. Specifically, the schemes include two paralleled-connected delta filter windings with zero impedance, and the 11th and 13th tuned filtering branches are installed at the taps. On this basis, the 5th and 7th harmonic filters are eliminated and the 5th, 7th, 11th, and 13th harmonics of the valve-side are suppressed. Moreover, the cost of the filter is reduced, and the negative impact on the converter transformer body caused by the transfer of harmonic current is avoided, such as vibration, noise, and harmonic loss. In this paper, first, the mathematical models of integrated multi-winding inductive filter converter and its filter system are established. Accordingly, the current relationships between the primary winding side and two secondary winding sides are derived. Then, the transfer path of each characteristic harmonic current in the new system is analyzed and discussed. Moreover, a simulation model is established to study the operation characteristics of the system. Finally, through the designed experimental prototype, a new DC transferring system platform is constructed to testify the operation characteristics of an integrated multi-winding inductive filter converter and its filter system. The experimental results show that the total harmonic distortion rate of the grid-winding current can be reduced to 4.68% only by installing the 11th and 13th tuned filters, so the effect of active filtering is approximated realized by the passive filtering method.
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Jafari, Hamid, e Ramin Sedaghati. "Analysis of an Adaptive Periodic Low-Frequency Wave Filter Featuring Magnetorheological Elastomers". Polymers 15, n. 3 (31 gennaio 2023): 735. http://dx.doi.org/10.3390/polym15030735.
Testo completoAbstract (sommario):
This study aims to enhance and tune wave-propagation properties (Bandgaps) of periodic structures featuring magnetorheological elastomers (MREs). For this purpose, first, a basic model of periodic structures (square unit cell with cross-shaped arms), which does not possess noise filtering properties in the conventional configuration, is considered. A passive attenuation zone is then proposed by adding a cylindrical core mass to the center of the conventional geometry and changing arm angles, which permitted new bandgap areas. It was shown that better wave-filtering performance may be achieved by introducing a large radius of the cylindrical core as well as low negative cross-arm angles. The modified configuration of the unit cell was subsequently utilized as the basic model for the development of magnetoactive metamaterial using a MRE capable of varying the bandgaps areas upon application of an external magnetic field. The finite element model of the proposed MRE-based periodic unit cell was developed, and the Bloch theorem was employed to systematically investigate the ability of the proposed adaptive periotic structure to attenuate low-frequency noise and vibration. Results show that the proposed MRE-based periodic wave filter can provide wide bandgap areas which can be adaptively changed and tuned using the applied magnetic field. The findings in this study can provide an essential guide for the development of novel adaptive periodic structures to filter low-frequency noises in the wide frequency band.
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Kulskyi, Oleksander L., S. V. Lysochenko, Volodymyr Vasylovych Ilchenko, Vasyl S. Mostovyi, Mykola M. Nikiforov, Anatolii Tymofiiovych Orlov e Volodymyr A. Zelinskyi. "Piezoelectric Sensor of Mechanical Vibrations". Microsystems, Electronics and Acoustics 27, n. 2 (29 agosto 2022): 265031–1. http://dx.doi.org/10.20535/2523-4455.mea.265031.
Testo completoAbstract (sommario):
Creation of high-sensitive sensor of mechanical vibrations, capable of non-distorted transformation of the vibrations source energy into electric signal within a wide dynamic range, is necessary for determination of characteristics of the source as well as for obtaining the information on parameters of medium in which the vibrations propagate. Fast and successful usage of obtained data can be achieved with employment of programming algorithms of identification of type of a source of vibrations and finding their fundamental Eigen frequencies and quality factors of the structures at these frequencies. Calculations of the schematic-and-technical decisions, selection of elements, making of mock-ups, and working-out of variants of the sensor. Mathematical modeling, analysis and identification of dynamical parameters of the structures in which there are used the fundamental eigenfrequencies and the structures’ quality factors at these frequencies. The Fourier and wavelet analyses of the spectra. Algorythms of digital filtering (moving average of measured data). Sensors of mechanical vibrations and a system for collection, analysis, and digital processing of the output data arrays are created. New effective method for analysis of conditions of natural and artificial objects is suggested. Algorythm for identification of type of mechanical vibrations source is developed. Transducers of mechanical vibrations are developed using film-based piezoelectric sensors of new generation. System for storing and processing of the sensors’ output data arrays is developed and a technique for transferring and saving the information is formulated. Structural parameters such as fundamental eigenfrequencies and the structures’ quality factors at corresponding frequencies are applied for identification of conditions of natural and engineering objects. Methodology for expertise of both the natural-based (wind) and the test-pulses-assisted dynamical loading is developed. Sets of single-type sub-models suitable for modeling, by their superposition, of the whole process are considered, and optimal sets of the model’s free parameters are determined. Degree of the model’s closeness to data obtained within a selected metrics serves as a criterion of optimality. Algorithm for identification of type of a mechanical vibrations’ source is developed basing on the signals representation as wavelets. The sensor-measured total signal includes wavelets from multiple sources and, because of this, the task of separation of the aggregated signal into constituents is accomplished. To achieve this, regularities within the signal should be found which might be interpreted as wavelet. Enumeration of the wavelets is determined with excess; the algorithm employs rules in accordance with which the enumeration and wavelets parameters are selected with more accuracy, and connection of wavelets with certain vibration sources is specified. Performance of the proposed sensor is fully confirmed by experimental data. Successful tests targeted at determination of technical characteristics of the sensor of mechanical vibrations are conducted within a passive survey system of stationary security installation. Seismograms of an approaching pedestrian are obtained for the distance of 30 m. Characteristics of the piezoelectric sensor of mechanical vibrations make it possible a plenty of applications of technical decisions, laid into its basis, in various spheres of science and technology.
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Yoon, Sang-Hee, e Ki Lyug Kim. "Passive low pass filtering effect of mechanical vibrations by a granular bed composed of microglass beads". Applied Physics Letters 89, n. 2 (10 luglio 2006): 021906. http://dx.doi.org/10.1063/1.2220012.
Testo completo
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Jang, Hoon-Seok, Mannan Saeed Muhammad, Guhnoo Yun e Dong Hwan Kim. "Sampling Based on Kalman Filter for Shape from Focus in the Presence of Noise". Applied Sciences 9, n. 16 (9 agosto 2019): 3276. http://dx.doi.org/10.3390/app9163276.
Testo completoAbstract (sommario):
Recovering three-dimensional (3D) shape of an object from two-dimensional (2D) information is one of the major domains of computer vision applications. Shape from Focus (SFF) is a passive optical technique that reconstructs 3D shape of an object using 2D images with different focus settings. When a 2D image sequence is obtained with constant step size in SFF, mechanical vibrations, referred as jitter noise, occur in each step. Since the jitter noise changes the focus values of 2D images, it causes erroneous recovery of 3D shape. In this paper, a new filtering method for estimating optimal image positions is proposed. First, jitter noise is modeled as Gaussian or speckle function, secondly, the focus curves acquired by one of the focus measure operators are modeled as a quadratic function for application of the filter. Finally, Kalman filter as the proposed method is designed and applied for removing jitter noise. The proposed method is experimented by using image sequences of synthetic and real objects. The performance is evaluated through various metrics to show the effectiveness of the proposed method in terms of reconstruction accuracy and computational complexity. Root Mean Square Error (RMSE), correlation, Peak Signal-to-Noise Ratio (PSNR), and computational time of the proposed method are improved on average by about 48%, 11%, 15%, and 5691%, respectively, compared with conventional filtering methods.
Tesi sul tema "Passive vibration filtering"
1
Avetisov, Stepan. "Herschel-Quincke filters for passive vibration mitigation". Electronic Thesis or Diss., Le Mans, 2024. https://cyberdoc-int.univ-lemans.fr/Theses/2024/2024LEMA1018.pdf.
Testo completoAbstract (sommario):
Les vibrations et les bruits de structure sont généralement des phénomènes indésirables pour des raisons de fiabilité et de confort. De nombreuses approches du contrôle des vibrations ont été étudiées au fil des ans, en utilisant diverses conceptions géométriques, des matériaux d'amortissement ou des stratégies de contrôle actif. En outre, l'allègement des structures mécaniques est un défi majeur en termes de consommation d'énergie, en particulier pour les applications de transport.Dans ces contextes combinés, l'objectif de cette thèse est de développer de nouveaux concepts de contrôle des vibrations en adaptant le principe des filtres de Herschel-Quincke (HQ), traditionnellement appliqué aux ondes acoustiques planes dans les tubes, au domaine des ondes élastiques dans les poutres et les plaques. En acoustique, les filtres HQ exploitent le principe de la différence de marche entre deux tubes parallèles de longueurs variables créés à partir d'un tube primaire, ce qui entraîne une interférence destructive et donc une transmission nulle à certaines fréquences.L'attrait des filtres HQ réside dans leur capacité à fournir de multiples pics de perte de transmission, ce qui constitue une alternative viable aux approches traditionnelles basées sur la résonance. Cette étude étend ce principe aux ondes de flexion en divisant une poutre mince en deux segments de longueur égale mais d'épaisseur différente. La différence de rigidité de flexion qui en résulte induit la différence de phase requise, ce qui conduit au filtrage des ondes. Cette approche fait des filtres HQ une solution prometteuse pour les applications de contrôle des vibrations et du bruit sans augmenter la masse de la structure considérée. Premièrement, le principe HQ pour la dynamique structurelle est analysé théoriquement à travers des modèles basés sur les ondes considérant les ondes longitudinales ou torsionnelles non dispersives et les ondes de flexion dans les poutres. Une étude expérimentale démontre également l'intérêt pratique de cette technique de filtrage. Ensuite, le principe est étendu aux structures de plaques, ce qui conduit à des filtres annulaires qui peuvent entourer une source de vibration et ainsi l'isoler du reste de la plaque. Enfin, des conceptions plus sophistiquées basées sur des arrangements sériels, parallèles ou périodiques de dispositifs structurels HQ sont proposées et analysées afin d'évaluer comment elles peuvent optimiser les performances de filtrage des vibrationsVibration and structure borne noise are generally undesirable phenomena for both the reliability and comfort issues. Many approaches to vibration control have been studied over the years, using various geometrical designs, damping materials, or active control strategies. In addition, lightening mechanical structures is a major challenge in terms of energy consumption, particularly for transport applications. In these combined contexts, the aim of this thesis is to develop new vibration control concepts by adapting the principle of Herschel-Quincke (HQ) filters, traditionally applied to plane acoustic waves in tubes, to the realm of elastic waves in beams and plates. In acoustics, HQ filters exploit the principle of a phase shift between two parallel tubes of varying lengths created from a primary tube, resulting in destructive interference and hence zero transmission at certain frequencies. The attractiveness of HQ filters lies in their capacity to provide multiple transmission loss peaks, presenting a viable alternative to traditional resonance-based approaches. This study extends this principle to bending waves by partitioning a thin beam into two segments of equal length but different thicknesses. The resulting disparity in bending stiffness induces the requisite phase difference, leading to wave filtering. This approach positions HQ filters as a promising solution for vibration and noise control applications without increasing the mass of the considered structure. First, the HQ principle for structural dynamics is theoretically analysed through wave based models considering non dispersive longitudinal or torsional waves and bending waves in beams. An experimental study also demonstrates the practical interest of this filtering technique. Then, the principle is extended to plates structures, leading to annular filters that may surround a vibration source and so isolate it from the rest of the plate. Third, some more sophisticated designs based on serial, parallel or periodic arrangements of structural HQ devices are proposed and analyzed to assess how they can optimize vibration filtering performance
Atti di convegni sul tema "Passive vibration filtering"
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Toso, M., A. Baz e D. Pines. "Active Vibration Control of Periodic Rotating Shafts". In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-61514.
Testo completoAbstract (sommario):
The propagation of transverse waves in periodic rotating shafts is controlled actively by using piezoelectric inserts which are placed periodically along these shafts. The control strategies aim at tuning the unique filtering characteristis of the periodic shafts in such manner that prevent the propagation of the waves within specific frequency bands called “stop bands.” The spectral characteristics of these “stop bands” are controlled in response to the shaft vibration. A finite element model is developed for this class of actively controlled periodic shafts which is then used to generate the “transfer matrix” for the unit cell of these shafts. The eigenvalues of the resulting transfer matrix are utilized to predict the characteristics of the stop and the pass bands of the rotating shaft as function of the shaft geometry, rotation speed, and control gains of the active inserts. The obtained characteristics are validated experimentally using shafts driven via gearbox assembly which subject the shafts to broadband excitations. The obtained results are also compared with the characteristics of passive shafts with stepped periodic geometries. Such a comparison aims at demonstrating the effectiveness of the active periodic shafts in redistributing the energy spectrum by confining the propagation to specific frequency bands. Particular emphasis is placed on studying the effect of the active control strategies on the vibration damping characteristics of the shafts. The proposed class of active periodic shafts can be useful in numerous critical applications such as the drive shafts of helicopters where transmitted vibrations can have detrimental effect on the performance of the tail rotor. Other applications are only limited by our imagination.
2
Leifer, Jack, e Stephen J. Weisenburger. "Materials and Techniques for Reduction of Vibration Transmission in String Trimmers". In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-88064.
Testo completoAbstract (sommario):
It has been well documented that over long periods of time, people who regularly operate hand tools powered by small internal-combustion engines can become affected by a debilitating set of clinically irreversible effects, collectively referred to as hand-arm vibration syndrome (HAVS). Although HAVS cannot be cured, the onset of the disorder can be delayed or, in fact, prevented, by restricting the duration of the exposure and/or the magnitude of the vibration transmitted from the tool to an operator’s hands and arms (per OSHA and similar standards). Measurements have confirmed that vibration components along all three tool coordinate directions (axial, radial and circumferential) are significant, but vary in amplitude and frequency content as a function of location. The challenge is to find passive approaches capable of filtering out the most harmful low frequency components simultaneously along all three directions that do not impede the use of the string trimmer. Preliminary results show that adding lightweight, low density (lodengraf) particles to the string trimmer along its shaft reduces the amplitude of the measured radial and axial acceleration components at the grip and the loop handle. However, when the perlite particles are added only to the loop handle, there is an increase in measured circumferential acceleration component at the grip, likely due to the additional weight asymmetry introduced.
3
Cao, Mincan, e Lei Zuo. "Energy Harvesting From Building Seismic Isolation With Multi-Mode Resonant Shunt Circuits". In ASME 2014 Dynamic Systems and Control Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/dscc2014-6071.
Testo completoAbstract (sommario):
A novel electromagnetic transducer shunt circuit is proposed in this paper for dual-functional energy harvesting and vibration control of building seismic isolation. In recent decades, base isolation systems are widely used in low and middle rise buildings. Even though base isolation can filter out high frequency excitation from earthquake, it still necessary to consider higher order modes’ vibration in host structure. The new design extends the multi-mode shunt circuit technology in piezoelectric area in order to achieve good vibration suppression into the seismic isolation of multi degree of freedoms (MDOF) of host structure of buildings, and use multi-mode circuit to achieve both energy harvesting and seismic vibration control. A numerical study of simplified two degree of freedom base isolation is presented in this paper. This passive system is also examined by giving recorded earthquake excitation. The stimulation results show that this new design could take advantage both of low-pass filtering capacity of base isolation system and resonant vibration reduction of electromagnetic shunt circuit. It is also observed that parameters selected for vibration reduction of building can effectively achieve large-scale energy harvesting at same time.
4
Baz, A. "Active Control of Periodic Structures". In ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-1734.
Testo completoAbstract (sommario):
Abstract Conventional passive periodic structures exhibit unique dynamic characteristics that make them act as mechanical filters for wave propagation. As a result, waves can propagate along the periodic structures only within specific frequency bands called the “Pass Bands” and wave propagation is completely blocked within other frequency bands called the “Stop Bands”. In this paper, the emphasis is placed on providing the passive structures with active control capabilities in order to tune the spectral width and location of the pass and stop bands in response to the structural vibration. Apart from their unique filtering characteristics, the ability of periodic structures to transmit waves, from one location to another, within the pass bands can be greatly reduced when the ideal periodicity is disrupted resulting in the well-known phenomenon of “Localization”. In the case of passive structures, the aperiodicity (or the disorder) can result from unintentional material, geometric and manufacturing variability. However, in the case of active periodic structures the aperiodicity is intentionally introduced by proper tuning of the controllers of the individual substructure or cell. The theory governing the operation of this class of Active Periodic structures is introduced and numerical examples are presented to illustrate their tunable filtering and localization characteristics. The examples considered include periodic/aperiodic spring-mass systems controlled by piezoelectric actuators. The presented results emphasize the unique potential of the active periodic structures in controlling the wave propagation both in the spectral and spatial domains in an attempt to stop/confine the propagation of undesirable disturbances.
5
Goyder, Hugh. "Measuring Damping in Linear and Nonlinear Systems". In ASME 2023 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/pvp2023-106667.
Testo completoAbstract (sommario):
Abstract It is shown how measurements of the decaying response of a vibrating system, following an initial disturbance, can be analysed to extract natural frequency and damping properties. Typically, such data contains a superposition of many vibration modes. By using filtering, it is demonstrated how individual modes can be extracted. The filtering must be done in a special way that involves reversing the data in time and passing it through a narrow band filter and truncating the data. Reversing the data prevents the filter characteristics contaminating the filter output. If the data is from a linear system then the natural frequency and damping are preserved by this process. If the data is nonlinear then the instantaneous frequency and damping are also preserved but are modified in a way that can be reversed. It is shown how all the effects of the filtering can be eliminated so that the decaying response of each mode is obtained. This approach provides a useful extension to experimental modal analysis that is applicable to nonlinear systems.
6
Loiko, Yu, V. Ahufinger, R. Corbalan, G. Birkl e J. Mompart. "Filtering of matter wave vibrational states via spatial adiabatic passage". In 12th European Quantum Electronics Conference CLEO EUROPE/EQEC. IEEE, 2011. http://dx.doi.org/10.1109/cleoe.2011.5943429.
Testo completo
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Hajjaj, Amal Z., e Nizar Jaber. "Geometry Optimization for Resonator Nonlinearities and Modes Controlling". In ASME 2021 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/detc2021-68529.
Testo completoAbstract (sommario):
Abstract In this paper, we utilize a passive technique based on geometry optimization to control the nonlinearities and the dynamical response of MEMS resonators. To achieve this, we propose a new hybrid shape combining a straight and initially curved microbeam. The Galerkin method is employed to solve the beam equation and study the effect of the different design parameters on the ratios of the frequencies and the nonlinearities of the structure. We show by adequately selecting the parameters of the structure; we can realize systems with strong quadratic or cubic nonlinearities or even zero nonlinearity. Also, we investigate the resonator shape effect on breaking the symmetry and explore different linear coupling phenomena: crossing, veering, and mode hybridization. We demonstrate the possibility of controlling the frequencies of the different modes of vibrations to achieve commensurate ratios necessary for activating internal resonance. The ability to activate the nonlinearities and tuning the frequencies is essential for wide range of applications in signal filtering, sensing, timing, and mass and gas sensing. The proposed method is simple in principle, easy to fabricate, and offers a wide range of controllability on the sensor nonlinearities and response. In addition, the passive techniques does not need additional circuits, to control the frequencies, which help reducing the device size, cost, and power consumption.
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Alaie, Seyedhamidreza, Arash K. Mousavi, Mehmet Su e Zayd C. Leseman. "Finite Element Analysis of a Phononic Crystal at Gigahertz Frequencies". In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-39005.
Testo completoAbstract (sommario):
In this paper, the vibrational behavior of a phononic crystal is studied at gigahertz frequencies. The phononic crystal is comprised of a silicon slab with tungsten inclusions filtering out waves within the frequency range of 0.7 GHz to 1.1 GHz. Two-dimensional harmonic finite element analysis (FEA) is employed to model the transmission of stresswaves launched from a transmitter and passing through the crystal. The numerical results are compared with another prevalent numerical method, finite difference time domain (FDTD), as well as with experimental results. Comparisons made between the numerical approaches and experimental approach, show that the harmonic finite element analysis agrees well with experiment and potentially can explain the experimental results more precisely than FDTD. This more favorable comparison is attributed to a resonance that occurs between the transmitter and the phononic crystal.
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Riva, Emanuele, Gabriele Cazzulani, Edoardo Belloni e Francesco Braghin. "An Optimal Method for Periodic Structures Design". In ASME 2017 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/smasis2017-3837.
Testo completoAbstract (sommario):
Periodic structures provide filtering behavior for vibrations, as a result of the repetition in space of unit blocks, or unit cells. In general, they are characterized by an internal mechanical impedance mismatch, so that waves are reflected and transmitted every time a discontinuity is present. The global behavior given by waves superposition is their cancellation, only for specific frequency ranges, generally called stop-bands or band-gaps. The variation of non-dimensional parameters shows how these attenuation regions move in the frequency domain: the correspondent diagrams are the main tools for the design problem and are known as band-maps. The selection of the geometrical, physical and elastic properties of the unit cell is therefore dependent on the designer experience and nothing can be said about the optimality of the proposed solution. Numerical methods are used for the selection of the best cell geometry, in order to get optimal attenuation. Generally, this is a time consuming approach. In this paper, an new method is presented, based on how the waves are reflected and transmitted at cells interface. Both beam and rod case studies are investigated. The algorithm allows matching between band-gap central frequency and the desired value, while the designed attenuation is optimal there, under certain physical and geometrical constraints. Moreover, the design of the bandgap location has been decoupled from the design of the magnitude of attenuation. This approach is purely analytic, therefore the computational efforts required are minimum. In order to validate the analytical model, a passive periodic beam has been manufactured. Its real frequency response is therefore compared to the expected one.
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Tibbals, Thomas F., Theodore A. Bapty e Ben A. Abbott. "CADDMAS: A Real-Time Parallel System for Dynamic Data Analysis". In ASME 1994 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1994. http://dx.doi.org/10.1115/94-gt-194.
Testo completoAbstract (sommario):
Arnold Engineering Development Center (AEDC) has designed and built a high-speed data acquisition and processing system for real-time online dynamic data monitoring and analysis. The Computer Assisted Dynamic Data Monitoring and Analysis System (CADDMAS) provides 24 channels at high frequency and another 24 channels at low frequency for online real-time aeromechanical, vibration, and performance analysis of advanced turbo-engines and other systems. The system is primarily built around two different parallel processors and several PCs to demonstrate hardware independence and architecture scalability. These processors provide the computational power to display online and in real-time what can take from days to weeks using existing offline techniques. The CADDMAS provides online test direction and immediate hardcopy plots for critical parameters, all the while providing continuous health monitoring through parameter limit checking. Special in-house developed Front End Processors (FEP) sample the dynamic signals, perform anti-aliasing, signal transfer function correction, and bandlimit filtering to improve the accuracy of the time domain signal. A second in-house developed Numeric Processing Element (NPE) performs the FFT, threshold monitoring, and packetizes the data for rapid asynchronous access by the parallel network. Finally, the data are then formatted for display, hardcopy plotting, and cross-channel processing within the parallel network utilizing off-the-shelf hardware. The parallel network is a heterogeneous message-passing parallel pipeline configuration which permits easy scaling of the system. Advanced parallel processing scheduler/controller software has been adapted specifically for CADDMAS to allow quasi-dynamic instantiation of a variety of simultaneous data processing tasks concurrent with display and alarm monitoring functions without gapping the data. Although many applications of CADDMAS exist, this paper describes the features of CADDMAS, the development approach, and the application of CADDMAS for turbine engine aeromechanical testing.