한국산학기술학회논문지 (Journal of the Korea Academia-Industrial cooperation Society)

  • 제19권11호
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  • Pages.594-603
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  • 2018
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  • 1975-4701(pISSN)
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  • 2288-4688(eISSN)
한국산학기술학회 (The Korea Academia-Industrial cooperation Society)
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최소화된 계측 및 신호 처리 시스템을 이용한 상시진동 케이블의 효율적인 장력 추정에 관한 연구

A Study on the Efficient Tension Estimation of Cables under Ambient Vibration using Minimized Measurement and Signal Processing System

  • Lee, Hyeong-Jin (Department of Civil Engineering, Changwon National University)
  • 투고 : 2018.08.22
  • 심사 : 2018.11.02
  • 발행 : 2018.11.30
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⟨ 이전 논문 다음 논문 ⟩

초록

최근 계측 기술의 발달에 따라 종래의 복잡하고 시간 소모적인 현장 계측분석 작업을 단순하고 편리하게 만드는 작업이 가능해지고 있다. 이런 배경에서 이 논문에서는 최소화된 계측 및 신호처리를 통해 상시진동 케이블의 장력을 추정하는 문제에 대해 연구하였다. 최소화 계측 방법으로는 저가 영상장비로 촬영된 동영상만을 이용하는 영상 변위 계측을 구상하였다. 또한 이로 인한 유효 주파수 대역 부족 문제의 해결을 위해 미러 주파수를 이용한 고유진동수 추정 방법을 제시하였다. 더불어 현장 사용 성능과 관련한 상시진동 문제를 처리하기 위해 신호처리 및 고유진동수 추정법으로 FDD 방법이 채택되었다. 제안된 최소화 계측 시스템과 미러 주파수 개념의 특성 및 FDD 방법의 적용성을 보기 위하여 사장교 모형을 이용한 실험적 연구가 수행되었다. 실험 결과는 상시진동을 위한 FDD 방법이 최소화 시스템을 이용한 고유 진동수 판별에서도 효과적으로 잘 작동됨을 보여 주었다. 또한 미러 주파수 개념은 저속촬영에 따라 왜곡된 신호에서도 고주파수 영역에 있는 고유진동수 추정이 가능함을 보여 최소화 시스템의 한계돌파에 효과적임을 보여 주었다. 결론적으로 실험결과는 제안된 최소화 계측 및 신호처리 시스템이 상시진동 케이블 장력 추정에 효과적인 방법이 될 수 있음을 보여주었다.

Recently, according to the development of measurement techniques, it has become possible to take complicated and time-consuming field measurements in a simple and convenient manner. In this background, this study estimated the tension of cables under ambient vibration using minimized measurement and signal processing. The VBDM using video-only by low-cost equipment was used as a minimized measurement. An estimation of the natural frequency using the mirror frequency concept was also proposed to solve the shortage of frequency band in this case. Furthermore, the FDD method was adopted for a natural frequency estimation in the ambient vibration related to field application. Experimental studies using a cable-stayed bridge model were carried out to examine the properties of the mirror frequency and the applicability of FDD with the proposed minimized system. The results showed that FDD for ambient vibration also works properly in an estimation of the natural frequency using the minimized system. In addition, the mirror frequency concept can allow a high natural frequency estimation even in a distorted signal by low-speed recording, which can overcome the limit of the minimized system. Overall, the proposed minimized system can be effective for the tension estimations of a cable under ambient vibration.

키워드

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Fig. 1. Procedure of tension estimation using vision-based displacement measurement

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Fig. 2. Setup of vision-based displacement measurement

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Fig. 3. Frequency function due to aliasing effect (a) Exact frequency function and mirror image (b) Actually estimated frequency function

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Fig. 4. Basic concept of system identification method

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Fig. 5. Grouping of time history for average

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Fig. 6. Experimental setup (a) Model of cable-stayed bridge (b) Applied load (c) Target and cam-corder

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Fig. 7. Measured time history, frequency and PSD functions (129cm 9kg, 60FPS) (a) Measured time history (b) Frequency function in DFA (No window) (c) PSD function in FDD (Hanning window)

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Fig. 8. Measured time history, frequency and PSD functions (84cm 3kg, 60FPS) (a) Measured time history (b) Frequency function in DFA (No window) (c) PSD function in FDD (Hanning window)

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Fig. 9. Exact and estimated natural frequencies (a) 1.29 m (b) 1.03 m (c) 0.84 m

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Fig. 10. Exact and estimated cable tensions (a) 1.29 m (b) 1.03 m (c) 0.84 m

Table 1. Specification of cases

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