• 한국광학회지
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• 제14권3호
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• pp.260-265
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• 2003

미세하게 진동하는 물체의 변위를 비접촉식으로 측정할 수 있는 광학계를 설계하고 제작하였다. 도플러효과에 의한 방법과는 달리, 하나의 볼록렌즈를 이용하여 물체 표면에 비스듬하게 입사하여 물체 표면에서 반사되는 광점의 위치 변화를 PSD(position-sensitive detector)로 검출하였다. 이러한 방법으로 전체적인 장비의 크기를 작게 하였고 빠른 응답 속도를 구현하였다. 본 장비는 $\pm$1.0 $\mu\textrm{m}$의 분해능을 나타내었으며, 스피커의 진동 실험 및 CD-ROM안에서 회전하는 C교의 진동을 측정하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.320-325
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• 2009

In this study, a method to estimate the suspension bridge deflection is developed using mode decomposition technique. In order to examine the suspension bridge stability against these dynamic loadings, the prediction of displacement response is very important to evaluate bridge stability. However, it is recognized that any measurement of movement for suspension bridges may be difficult for the absence of proper methods to measure the displacement response on site. This study aims at suggesting a method to estimate the displacement response from the measured strain signals in an indirect way to predict the displacement response, not a direct way to measure the displacement response. Additionally, by applying the FBG sensors with multi-point measurements not influenced by electric noise, it can be expected that the technique would be applicable to infrastructures.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.61-67
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• 1997

The electronic speckle pattern interferometer (ESPI) has been applied to many technical problems such as deformation and displacement measurement, strain visualization and surface roughness monitoring. In this study, we used an ESPI system based on the dual beam speckle interferometer method in order to measure in-plane displacement and vibration mode using the ESIP technique. This research was carried out for the purpose of applying the vibration analysis method employing Electro-Optic holographic interference technique to the vibration analysis of uniform rectangular cantilevers plate(SS400,STS304) with cantilevers span to breadth ratio of 150 by 75. And thickness of 1mm and 0.8mm respectively. We improved the ESPI technique in order to obtain the distribution of displacement component resolved in one direction through a CCD camera combined with an image processing system. To certify and to assess the accuracy in measuring by this ESPI, the results obtained with the speckle method and vibration mode analysis are to be compared with those results by Warbuton's Theoretical expression and vibration made in FEM analysis.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.381-386
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• 2002

This paper presents a piezoelectric shunt methodology to reduce unwanted vibration of optical disk drive(O.D.D.). After briefly investigating a second-order mechanical vibration absorber model, the O.D.D. structure is incorporated with the piezoelectric shunt circuit. In order to evaluate feasibility of multi-mode passive damping of the structure, admittance measurement of piezoceramic is undertaken. The parameters are optimally tuned by admittance measurement results on the basis of the circuit model and displacement transmissibility is evaluated. To verify validity of admittance measurement result, experiment is performed and vibration reduction is achieved at two different modes.

• 한국소음진동공학회논문집
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• 제12권1호
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• pp.65-72
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• 2002

Generally, there are laser operating equipments( aligner, stepper) and electronic microscope( SEM, TEM) as a high precision manufacturing and inspection equipment in semiconductor production companies, precision examination and measuring laboratories. Mostly, these equipments are characterized by projection and target part. The relative displacements between projection and target part are dominant roles in vibrational problem in these precision equipments. These relative displacements are determined by the position of incoming vibration and the difference of vibration response in projection and target part. In this study, the allowable vibrational limits are suggested and the vibrational reduction plans are proposed by measurement and analysis of vibration phenomenon in the Clean Room in PDP(plasma display panel) production building. The vibration performance is evaluated by comparison relative displacements between projection and target part before/after the vibration isolation plan.

• 한국소음진동공학회논문집
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• 제20권11호
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• pp.1033-1037
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• 2010

Accelerometer and laser vibrometers are widely used to measure vibration of structures like a building or piping. Recently, the research measuring vibration by using camera image is introduced. This method can measure multi-points simultaneously. Also, it is possible to measure in the long distance. When we measure the vibration using a camera, the parameter analysis is needed. Therefore, this paper took the experiment for the camera lens selection. An error by the camera images characteristic was theoretically analyzed and we verified through an experiment. And the accuracy of the method measuring the vibration displacement by using the camera images was analyzed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1738-1740
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• 1996

Laser Doppler Vibrometer using heterodyne method with a 632.8 nm He-Ne laser, has been developed for the measurement of small displacement and velocity. The measurement uses heterodyne method can be made insensitive to undesired vibration effect acting the system and can yield the sign of Doppler shift at the expense of increased complexity. A Bragg cell gives a frequency shift of 40MHz for heterodyne method. Frequency Modulated output is detected by spectrum analyzer.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.303-305
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• 2014

This paper is concerned with the vibration measurement of cable by image processing technique. The measurement system consists of a CCD camera and zoom lens. The image data can be transferred to PC via USB or IEEE1394 port. In this study, a Matlab program was made to process the acquired image data. After acquiring an image data for each frame, this data is binarized for tracing cable vibrations. Then the area occupied by the cable is marked by 1 and the background is covered by 0. In this way, we can calculate the displacement of the cable. Experimental results show that the tracing of cable displacements is possible and natural frequencies and mode shapes can be computed. The accuracy of the image processing system for vibration measurement depends on the maximum frame rate of the CCD camera. The use of a high-speed camera enables us to compute more higher modes. The laboratory experiments guarantee the vibration measurement of real transmission lines.

• 한국소음진동공학회논문집
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• 제19권9호
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• pp.943-949
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• 2009

Many studies for measuring vibration using image signal are suggested. These methods can measure vibration of multi-points simultaneously. However, it has the disadvantage that is very sensitive to an environment. If the measured environment is not good, image signals can be measured including much background noise. So, it is difficult to obtain accurate vibration from the measured image signals. Another problem is that camera imaging has a resolution limit. Because the resolution of the camera image is relatively much lower than that of a data acquisition system, accurate measuring vibration cannot be performed. In this paper, we proposed the enhanced technique for measuring vibration using camera signal. The key word of this paper is a curve fitting. The curve fitting can exactly detect the measurement line of interested object. So, we can measure the vibration in noisy environment. Also, it can overcome the resolution limit.

• Smart Structures and Systems
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• 제12권3_4호
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• pp.363-379
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• 2013

Dynamic displacement of structures is an important index for in-service structural condition and behavior assessment, but accurate measurement of structural displacement for large-scale civil structures such as long-span bridges still remains as a challenging task. In this paper, a vision-based dynamic displacement measurement system with the use of digital image processing technology is developed, which is featured by its distinctive characteristics in non-contact, long-distance, and high-precision structural displacement measurement. The hardware of this system is mainly composed of a high-resolution industrial CCD (charge-coupled-device) digital camera and an extended-range zoom lens. Through continuously tracing and identifying a target on the structure, the structural displacement is derived through cross-correlation analysis between the predefined pattern and the captured digital images with the aid of a pattern matching algorithm. To validate the developed system, MTS tests of sinusoidal motions under different vibration frequencies and amplitudes and shaking table tests with different excitations (the El-Centro earthquake wave and a sinusoidal motion) are carried out. Additionally, in-situ verification experiments are performed to measure the mid-span vertical displacement of the suspension Tsing Ma Bridge in the operational condition and the cable-stayed Stonecutters Bridge during loading tests. The obtained results show that the developed system exhibits an excellent capability in real-time measurement of structural displacement and can serve as a good complement to the traditional sensors.