• Title/Summary/Keyword: 도플러 스캐닝

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The Relative Position Estimate of the Moving Distributed Sources Using the Doppler Scanning Technique (도플러 스캐닝 기법을 이용한 이동하는 다중 음원의 상대 위치 추적 기법)

  • 노용주;윤종락;전재진
    • The Journal of the Acoustical Society of Korea
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    • v.21 no.5
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    • pp.446-454
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    • 2002
  • This paper presents the Doppler Scanning technique which enables us to detect the relative positions of moving distributed sources using Doppler frequency shift estimate when the moving source consists of distributed sources with different signature frequencies. Doppler frequency shifts of characteristic frequencies of machinery noise sources such as ship's generator and propeller, with tine along CPA (Closest Point of Approach of moving source) are unique, and can be functioned with respect to each source position. Therefore, this technique can be applied to estimate the relative geometrical positions between machinery noise sources. The Extended Kalman Filter (EKF) which has a high frequency resolution with high time resolution, is adopted for improving accuracy of Doppler frequency shift estimate geometric resolution of machinery positions since machinery noise sources show in general low frequency band characteristics with limited spacial distance. The performance of the technique is examined by the numerical simulations and is verified by the experiment using loudspeaker sources on the roof of the car.

A Continuous Scanning Laser Doppler Vibrometer for Mode Shape Analysis (모드형상분석을 위한 연속 스캐닝 레이저 도플러 진동측정기)

  • 라종필;최지은;박기환;경용수;왕세명;김경석
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.05a
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    • pp.274-280
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    • 2002
  • This paper addresses the vibration mode shape measurement technique utilizing a Continuous Scanning Laser Doppler Vibrometer (CSLDV). The continuous scanning capability is added to the conventional discrete Laser Doppler Vibrometer by reflecting the laser beams on the surface of the object using two oscillating mirrors. The bow scanning resulted from the proposed scanning method is eliminated by feedback control. The velocity output signal from the CSLDV is modulated to give the spatial velocity distribution in terms of coefficients which are obtained from the Fast Fourier Transformation of the time dependent velocity signal. Using the Chebyshev series form, the analysis of the vibration mode shape techniques for straight Bine scanning and 2 dimensional scanning are presented and discussed. The performance of the proposed SLDV is presented using the experimental results of the vibration mode shape of a plate

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A Continuous Scanning Laser Doppler Vibrometer for Mode Shape Analysis (모드형상분석을 위한 연속 스캐닝 레이저 도플러 진동측정기)

  • Park, Kyi-Hwan;Choi, Ji-Eun;La, Jong-Pil;Wang, Sem-Yung;Kyoung, Yong-Soo;Kim, Koung-Suk
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.5
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    • pp.734-741
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    • 2003
  • This paper addresses the vibration mode shape Measurement technique utilizing a Continuous Scanning Laser Doppler Vibrometer (CSLDV). The continuous scanning capability is added to the conventional discrete Laser Doppler Vibrometer by reflecting the laser beams on the surface of the object using two oscillating mirrors. The bow scanning resulted from the proposed scanning method is eliminated by feedback control. The velocity output signal from the CSLDV is modulated to give the spatial velocity distribution in terms of coefficients which are obtained from the Fast Fourier Transformation of the time dependent velocity signal. Using the Chebyshev series from, the analysis of the vibration mode shape techniques for straight line scanning and 2 dimensional scanning are presented and discussed. The performance of the proposed SLDV is presented using the experimental results of the vibration mode shape of a cantilever and plate

Measurement of Mode Shape By Using A Scanning Laser Doppler Vibrometer (스캐닝 레이저 도플러 진동계를 이용한 모드 해석)

  • Gang, Min-Sik
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.10 s.181
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    • pp.2560-2567
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    • 2000
  • When spatially dense velocity distribution is measured by a scanning laser Doppler vibrometer, the Fourier transform method provides the real and imaginary parts of the mode shapes in the form of a polynomial. However the Fourier transform method is often impractical because the independent decomposition property of cosine and sine components into real and imaginary parts, respectively, does not hold due to the leakage problem which commonly occurs in the Fourier transform of harmonic signals. To deal with this problem, a Hilbert transform method is newly proposed in this article. The proposed method is free from the leakage problem and relatively robust to the scanning error. A simulation example is provided to verify the effectiveness of this method.

Development of An Automated Scanning Laser Doppler Vibrometer for Measurements of In-Plane Structural Vibration (평면 구조 진동 측정을 위한 자동화된 스캐닝 레이저 도플러 진동측정기의 개발 및 연구)

  • Kil, Hyun-Gwon
    • Journal of KSNVE
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    • v.7 no.2
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    • pp.231-238
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    • 1997
  • An automated scanning laser Doppler vibrometer (LDV) has been designed, and built to measure in-plane vibration fields over structures. Use of optical fibers allows the compact design of a laser probe head which can be scanned over the vibrating structures. An algorithm for automated self-alignment of the laser probe is developed. The system is completely automated for scanning over the structures, focusing two laser beams at each data point until the detected vibration signal is stable, and for recording and transferring the data to a system computer. The automated system allows one to get extensive data of the vibration field over the structures. The system is tested by scanning a piezoelectric cylindrical shell and a plate excited by a continuous signal and by a pulse signal, respectively. Results show that the automated scanning LDV system can be a useful tool to measure the in-plane vibration field and to detect the elastic waves propagating on the vibrating structures.

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Mode Shape Reconstruction of an impulse excited structure using HHT and CSLDV (HHT와 연속스캐닝 진동계를 이용한 임펄스가진된 구조물의 모드 형상 복원)

  • Kyong, Yong-Soo;Kim, Dae-Sung;Dayou, Jedol;Park, Kyi-Hwan;Wang, Se-Myung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.04a
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    • pp.484-490
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    • 2008
  • For CSLDV, the Chebyshev demodulation (or polynomial) technique and Hilbert transform approach have been used for mode shape reconstruction with harmonic excitation. In this paper, the Hilbert-Huang transform approach was applied as an alternative to impact excitation cases in terms of a numerical approach. The vibration of the tested structure is modeled using impulse response functions. In order to verify this technique, a simply supported beam was chosen as the test rig. With additional innovative steps which are the ideal-band pass filter and the nodal point determination, Hilbert-Huang transformation can be used for a good mode shape reconstruction even in the impact excitation case.

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Modal Identification of a randomly excited 1-D structure using Scanned data (스캐닝 데이터를 이용한 랜덤 가진된 일차원 구조물의 모달 분석)

  • 경용수;왕세명;김상명;박기환
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.05a
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    • pp.241-246
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    • 2002
  • Usually vibration properties are obtained from frequency response functions or impulse response functions of a system. Since the contact type sensors can affect the characteristics of vibrating systems, the non-contact type sensors such as laser Doppler vibrometer (LDV) are being widely used. Currently researches are being carried out in terms of modal analysis using a scanning vibrometer. For the continuous scan; the Chebyshev demodulation (or polynomial) is apparently suggested to extract the mode shapes. With single frequency sinusoidal excitation, this approach is well fitted. In this research, the Chebyshev demodulation technique has been applied to the impact excitation case. The vibration of the tested structure is modeled using impulse response functions. The technique is also adopted to the random excitation case. In order to verify the technique, a simply supported beam was chosen as the test rig. The calculation modules are developed by using MATLAB$\^$(R)/ in WindowsNT$\^$(R)/ environment.

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Investigation about unexpected effects of Chebyshev and Hilbert approach on using CSLDV (연속 스캐닝 진동계를 위한 체비세프와 힐버트 방식의 비교)

  • 왕세명;경용수;박기환;라종필;김경석;강기수;김창식
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.05a
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    • pp.414-419
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    • 2003
  • There are some methods fur extracting mode shapes from a continuously scanned data such as a modulation, Chebyshev polynomial, and Hilbert approach. In this paper, Chebyshev and Hilbert approaches were investigated through the numerical experiment first. As some experimental parameters were altered with small quantities, data were checked and plotted. From those results, the effects of unexpected parameters will be configured. And then, it will be actually helpful to select the proper method for specific testing environments.

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