• Title/Summary/Keyword: vibration signatures

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Current and Vibration Characteristics Analysis of Induction Motors for Vertical Pumps in Power Plant (발전소 대형 입형펌프 전동기의 전류/진동신호 특성 분석)

  • Bae, Yong-Chae;Lee, Hyun;Kim, Yeon-Whan
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.16 no.4 s.109
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    • pp.404-413
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    • 2006
  • Induction motors are the workhorse of our industry because of their versatility and robustness. The diagnosis of mechanical load and power transmission system failures is usually carried out through mechanical signals such as vibration signatures, acoustic emissions, motor speed envelope. The motor faults including mechanical rotor imbalances, broken rotor bar, bearing failure and eccentricities problems are reflected in electric, electromagnetic and mechanical quantities. The recent research has been directed toward electrical monitoring of the motor with emphasis on inspecting the stator current of the motor, The stator current spectrum has been widely used for fault detection in induction motor systems. The motor current signature analysis is the useful technique to assess machine electrical condition. This paper describes the motor condition detected by the current signatures Paralleled with vibration signatures analysis of induction motors with the roller bearing and the journal bearing type for large vertical pumps in power plant as examples to discuss for motor fault detection and diagnosis.

A review on recent development of vibration-based structural robust damage detection

  • Li, Y.Y.;Chen, Y.
    • Structural Engineering and Mechanics
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    • v.45 no.2
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    • pp.159-168
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    • 2013
  • The effect of structural uncertainties or measurement errors on damage detection results makes the robustness become one of the most important features during identification. Due to the wide use of vibration signatures on damage detection, the development of vibration-based techniques has attracted a great interest. In this work, a review on vibration-based robust detection techniques is presented, in which the robustness is considerably improved through modeling error compensation, environmental variation reduction, denoising, or proper sensing system design. It is hoped that this study can give help on structural health monitoring or damage mitigation control.

A Study on the Monitoring System of the Grinding Troubles Utilizing Neural Networks(l) (신경회로망을 이용한 연삭가공의 트러블 인식에 관한 연구(I))

  • Ha, M.K.;Kwak, J.S.;Song, J.B.;Kim, G.H.;Kim, H.S.
    • Journal of the Korean Society for Precision Engineering
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    • v.13 no.9
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    • pp.149-155
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    • 1996
  • Recent researches in the trouble monitoring system of grinding process have emphasized the use of deep knowledge. Such works include the monitoring and diagnostic systems for cylindrical grinding using sensors on chatter vibration and grinding burn during the process. But, since grinding operations are especially related with a lalrge amount of ambique parameters, it is effectively difficult to detect the grinding troubles occuring during the grinding process. In this paper, monitoring system for grinding utilizes the neural networks based on grinding power signatures. The monitoring system of grinding operations, which makes use of PDP neural networks, is presented. Then, the implementation results by computer simulations and experimental data with respect to chatter vibration and grinding burn are compared.

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Experimental modal analysis of railway concrete sleepers with cracks

  • Real, J.I.;Sanchez, M.E.;Real, T.;Sanchez, F.J.;Zamorano, C.
    • Structural Engineering and Mechanics
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    • v.44 no.1
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    • pp.51-60
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    • 2012
  • Concrete sleepers are essential components of the conventional railway. As support elements, sleepers are always subjective to a variety of time-dependent loads attributable to the train operations, either wheel or rail abnormalities. It has been observed that the sleepers may deteriorate due to these loads, inducing the formation of hairline cracks. There are two areas along the sleepers that are more prone to crack: the central and the rail seat sections. Several non-destructive methods have been developed to identify failures in structures. Health monitoring techniques are based on vibration responses measurements, which help engineers to identify the vibration-based damage or remotely monitor the sleeper health. In the present paper, the dynamic effects of the cracks in the vibration signatures of the railway pre-stressed concrete sleepers are investigated. The experimental modal analysis has been used to evaluate the modal bending changes in the vibration characteristics of the sleepers, differentiating between the central and the rail seat locations of the cracks. Modal parameters changes of the 'healthy' and cracked sleepers have been highlighted in terms of natural frequencies and modal damping. The paper concludes with a discussion of the most suitable failure indicator and it defines the vibration signatures of intact, central cracked and rail seat cracked sleepers.

Hybrid vibration-impedance monitoring in prestressed concrete structure with local strand breakage

  • Dang, Ngoc-Loi;Pham, Quang-Quang;Kim, Jeong-Tae
    • Smart Structures and Systems
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    • v.30 no.5
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    • pp.463-477
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    • 2022
  • In this paper, a hybrid vibration-impedance-based damage monitoring approach is experimentally evaluated for prestressed concrete (PSC) structures with local strand breakage. Firstly, the hybrid monitoring scheme is designed to alert damage occurrence from changes in vibration characteristics and to localize strand breakage from changes in impedance signatures. Secondly, a full-scale PSC anchorage is experimented to measure global vibration responses and local impedance responses under a sequence of simulated strand-breakage events. Finally, the measured data are analyzed using the hybrid monitoring framework. The change of structural condition (i.e., damage extent) induced by the local strand breakage is estimated by changes in a few natural frequencies obtained from a few accelerometers in the structure. The damaged strand is locally identified by tomography analysis of impedance features measured via an array of PZT (lead-zirconate-titanate) sensors mounted on the anchorage. Experimental results demonstrate that the strand breakage in the PSC structure can be accurately assessed by using the combined vibration and impedance features.

Hybrid Damage Monitoring Technique for Plate Girder Bridges using Acceleration-Impedance Signatures (판형교의 가속도-임피던스 신호를 이용한 하이브리드 손상 모니터링 기법)

  • Hong, Dong-Soo;Cho, Hyun-Man;Na, Won-Bae;Kim, Jeong-Tae;Park, Gyu-Hae
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2008.04a
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    • pp.197-202
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    • 2008
  • In this paper, a hybrid vibration-impedance approaches is newly proposed to detect the occurrence of damage, the location of damage, and extent of damage in steel plate-girder bridges. The hybrid scheme mainly consists of three sequential phases: 1) to alarm the occurrence of damage, 2) to classify the alarmed damage, and 3) to estimate the classified damage in detail. Damage types of interest include flexural stiffness-loss in girder and bolts-loose in supports. In the first phase, the global occurrence of damage is alarmed by monitoring changes in acceleration features. In the second phase, the alarmed damage is classified into subsystems by recognizing patterns of impedance features. In the final phase, the location and the extent of damage are estimated by using modal strain energy-based damage index method and root mean square deviation method. The feasibility of the proposed system is evaluated on a laboratory-scaled steel plate-girder bridge model for which hybrid vibration-impedance signatures were measured for several damage scenarios.

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Impedance-based Long-term Structural Health Monitoring for Tidal Current Power Plant Structure in Noisy Environments (잡음 환경 하에서의 전기-역학적 임피던스 기반 조류발전 구조물의 장기 건전성 모니터링)

  • Min, Ji-Young;Shim, Hyo-Jin;Yun, Chung-Bang;Yi, Jin-Hak
    • Journal of Ocean Engineering and Technology
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    • v.25 no.4
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    • pp.59-65
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    • 2011
  • In structural health monitoring (SHM) using electro-mechanical impedance signatures, it is a critical issue for extremely large structures to extract the best damage diagnosis results, while minimizing unknown environmental effects, including temperature, humidity, and acoustic vibration. If the impedance signatures fluctuate because of these factors, these fluctuations should be eliminated because they might hide the characteristics of the host structural damages. This paper presents a long-term SHM technique under an unknown noisy environment for tidal current power plant structures. The obtained impedance signatures contained significant variations during the measurements, especially in the audio frequency range. To eliminate these variations, a continuous principal component analysis was applied, and the results were compared with the conventional approach using the RMSD (Root Mean Square Deviation) and CC (Cross-correlation Coefficient) damage indices. Finally, it was found that this approach could be effectively used for long-term SHM in noisy environments.

WIGNER-VILLE INTERPRETATION OF MUSICAL SOUND AND TRANSIENT VIBRATION SIGNALS

  • Kim, Yang-Hann;Park, Yon-Kyu
    • Proceedings of the Acoustical Society of Korea Conference
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    • 1994.06a
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    • pp.752-757
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    • 1994
  • Very often, one would like to have visual image of mechanical or acoustical events such as musical sound and transient vibrations. Conventional methods to visualize the signal, such as power spectrum, do not normally allow to cultivate the signal of interests due to their inherent limitation on transient signals. Other than the conventional method, one could use an instantaneous frequency which can reveal the variation of frequency in terms of time. Nevertheless it is quite sensitive to noise and can not resolve the frequency components of signals; normally produces additional components other than those of the signals. In this paper, we introduce the Wigner-Ville spectrum to see the transient characteristics of signal, especially musical sound and transient mechanical vibration signatures. For musical sound, several popular western classic music have been selected for the analysis. For the transient mechanical signature, the signals obtained from the car door experiment and the beam experiment are interpreted in terms of Wigner-Ville spectrum. Results demonstrate the visual expressions of transient signals; musical sound and vibrations.

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Hybrid Damage Monitoring Scheme of PSC Girder Bridges using Acceleration and Impedance Signature (가속도 및 임피던스 신호를 이용한 PSC 거더교의 하이브리드 손상 모니터링 체계)

  • Kim, Jeong-Tae;Park, Jae-Hyung;Hong, Dong-Soo;Na, Won-Bae
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.1A
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    • pp.135-146
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    • 2008
  • In this paper, a hybrid damage monitoring scheme for prestressed concrete (PSC) girder bridges by using sequential acceleration and impedance signatures is newly proposed. Damage types of interest include prestress-loss in tendon and flexural stiffness-loss in a concrete girder. The hybrid scheme mainly consists of three sequential phases: damage alarming, damage classification, and damage estimation. In the first phase, the global occurrence of damage is alarmed by monitoring changes in acceleration features. In the second phase, the type of damage is classified into either prestress-loss or flexural stiffness-loss by recognizing patterns of impedance features. In the third phase, the location and the extent of damage are estimated by using two different ways: a mode shape-based damage detection to detect flexural stiffness-loss and a natural frequency-based prestress prediction to identify prestress-loss. The feasibility of the proposed scheme is evaluated on a laboratory-scaled PSC girder model for which hybrid vibration-impedance signatures were measured for several damage scenarios of prestress-loss and flexural stiffness-loss.

FxLMS Algorithm for Active Vibration Control of Structure By Using Inertial Damper with Displacement Constraint (관성형 능동 댐퍼를 이용한 구조물 진동 제어에서 댐퍼 질량의 변위 제한을 고려한 FxLMS 알고리즘)

  • Kang, Min Sig
    • Journal of the Korea Institute of Military Science and Technology
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    • v.24 no.5
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    • pp.545-557
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    • 2021
  • Engine is the main source of vibration that generates unwanted noise and vibration of vehicle chassis. Especially, in submarine applications, radiation of noise signatures can be detected at some distance away from the submarine using a sonar array. Thus quiet operation is crucial for submarine's survivability. This study addresses reduction of the force transmissibility originating from engines and transmitted to hull through engine mounts. An inertial damper, as an actuator of hybrid mount system, is addressed to reduce even further the level of vibration. Narrow band FxLMS algorithms are broadly used to cancel the vibration of engine mount because of its excellent performance of canceling narrow band noise. However, in real active dampers, the maximum displacement of damper mass is kinematically restricted. When the control input signal from the FxLMS algorithm exceeds this limitation, the damper mass will collide with the mechanical stops and results in many problems. Originated from these, a modified narrow band FxLMS algorithm based on the equalizer technique with the maximum allowable displacement of active damper mass is proposed in this study. Some simulation results showed that the propose algorithm is effective to suppress vibration of engine mount while ensuring given displacement constraint.