• 대한조선학회논문집
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• 제57권3호
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• pp.175-181
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• 2020

For the success of a structural integrity management, it is essential to acquire structural response data at some critical locations with limited number of sensors. In this study, the structural response of numerical model was estimated by data fusion approach based on the Kalman filter known as stochastic recursive filter. Firstly, transient direct analysis was conducted to calculate the acceleration and strain of the numerical standing beam model, then the noise signals were mixed to generate the numerical measurement signals. The acceleration measurement signal was provided to the Kalman filter as an information on the external load, and the displacement measurement, which was transformed from the strain measurement by using strain-displacement conversion relationship, was provided into the Kalman filter as an observation information. Finally, the Kalman filter estimated the displacement by combining both displacements calculated from each numerically measured signal, then the estimated results were compared with the results of the transient direct analysis.

• Smart Structures and Systems
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• 제13권6호
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• pp.927-942
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• 2014

Structural displacement is an important indicator for assessing structural safety. For structural displacement monitoring, vision-based displacement measurement systems have been widely developed; however, most systems estimate only 1 or 2-DOF translational displacement. To monitor the 6-DOF structural displacement with high accuracy, a vision-based displacement measurement system with a uniquely designed marker is proposed in this paper. The system is composed of a uniquely designed marker and a camera with a zooming capability, and relative translational and rotational displacement between the marker and the camera is estimated by finding a homography transformation. The novel marker is designed to make the system robust to measurement noise based on a sensitivity analysis of the conventional marker and it has been verified through Monte Carlo simulation results. The performance of the displacement estimation has been verified through two kinds of experimental tests; using a shaking table and a motorized stage. The results show that the system estimates the structural 6-DOF displacement, especially the translational displacement in Z-axis, with high accuracy in real time and is robust to measurement noise.

• 지질공학
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• 제17권2호
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• pp.217-224
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• 2007

터널이 굴착되면 응력이 재분배되는 과정동안 변위가 발생한다. 터널의 변위는 굴착 전 선행변위, 굴착 후 미측정 변위, 계측변위로 구분할 수 있다. 일반적으로 굴착 전 선행변위와 굴착 후 미측정 변위의 현장 측정은 어렵기 때문에 터널 굴착에 따른 전변위의 크기와 변화 양상을 산정하기 위한 연구가 많이 수행되어왔다. 본 연구에서는 퇴적암을 기반으로 하는 터널의 지반등급별 전변위를 산정하고 이들의 특성을 파악하기 위하여 역해석 기법을 사용하였다. 계측변위와 3차원 수치해석에 의해 계산된 변위의 오차를 최소한으로 줄여 지반등급별 물성치를 추정하였으며, 굴착에 따른 전변위 분포 양상을 산정하였다. 최종적으로 logistic 모형을 따르는 지반등급별 굴착에 따른 변위의 비선형 회귀식을 산정하였다.

• International Journal of Automotive Technology
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• 제7권3호
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• pp.337-343
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• 2006

Numerical calculations are made in order to find a possible correlation between the J-integral and the crack mouth opening displacement(CMOD) in dynamic nonlinear fracture experiments of 3-point bend(3PB) specimens. Both elastic-plastic and elastic-viscoplastic materials are considered at different impact velocities. The J-integral may be estimated from the crack mouth opening displacement which can be measured directly from photographs taken during dynamic experiments.

• 지질공학
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• 제17권2호
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• pp.197-204
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• 2007

터널은 굴착에 의해 지반의 변형을 일으키며, 지보를 설치하고 시간이 지남에 따라 점차 안정화된다. 터널 굴착이 지반 거동에 미치는 영향은 계측지점과 막장간의 거리가 증가함에 따라 감소한다. 터널의 변위가 수렴하여 안정화되는 시점을 예측할 수 있다면, 안정화 이후 이루어지는 여러 공정들을 앞당김으로써 시간적, 경제적 손실을 줄일 수 있다. 따라서 본 연구에서는 변위 수렴 시점을 예측하기 위하여 관리도 기법을 적용하였다. 퇴적암을 기반으로 하는 터널에 대한 관리도 판정 결과, 막장에서부터의 거리가 최대 100 m 이내에서 변위가 수렴하였다.

• Smart Structures and Systems
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• 제15권3호
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• pp.881-896
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• 2015

The authors' research group has developed a noncontact type of sensors which directly measure the inter-story drift displacements of a building during a seismic event. Soon after that event, such seismically-induced drift displacement data would provide structural engineers with useful information to judge how the stories have been damaged. This paper presents a scheme of estimating the story cumulative plastic deformation ratios based on such measured drift displacement information toward the building safety monitoring. The presented scheme requires the data of story drift displacements and the ground motion acceleration. The involved calculations are rather simple without any detailed information on structural elements required: the story hysteresis loops are first estimated and then the cumulative plastic deformation ratio of each story is evaluated from the estimated hysteresis. The effectiveness of the scheme is demonstrated by utilizing the data of full-scale building model experiment performed at E-defense and conducting numerical simulations.

• 한국멀티미디어학회논문지
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• 제11권4호
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• pp.454-461
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• 2008

본 논문에서는 이동변위를 기반으로 하는 휴대기기의 새로운 입력 방법을 제안한다. 이를 위하여 휴대기기에 장착되어 있는 카메라를 이용하여 영상을 연속적으로 획득하고, 획득된 영상간의 변위를 실시간으로 계산함으로써 휴대기기의 이동 변위를 추정하였다. 제안하는 알고리즘은 획득된 영상간의 변위를 실시간으로 계산하기 위하여 계산량이 적은 SUSAN 코너 검출기를 사용하여 두 영상에서 특징점 들을 추출하였다. 다음으로 추출된 특징점 사이의 매칭작업을 수행하기 위하여 투 패스 알고리즘을 적용한 보로노이 평면을 생성하고, 두 영상의 거리 값인 SAD (Sum of absolute difference)를 계산함으로써 두 영상간의 변위를 계산하였다. 실험결과에서는 총 1500장의 영상을 이용하여 변위 추정알고리즘의 성능을 평가하였다. 그 결과 최대 90% 이상 매칭 성공률을 보였으며, 연산 속도는 5 ms 이내였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.109-117
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• 2008

In this study, a method predicting the displacement responseof structures from the measured dynamic strain signal is proposed by using a mode decomposition technique. Dynamic loadings including wind and seismic loadings could be exerted to the bridge. In order to examine the bridge stability against these dynamic loadings, the prediction of displacement response is very important to evaluate bridge stability. Because it may be not easy for the displacement response to be acquired directly on site, an indirect method to predict the displacement response is needed. Thus, as an alternative for predicting the displacement response indirectly, the conversion of the measured strain signal into the displacement response is suggested, while the measured strain signal can be obtained using fiber optic Bragg-grating (FBG) sensors. To overcome such a problem, a mode decomposition technique was used in this study. The measured strain signal is decomposed into each modal component by using the empirical mode decomposition(EMD) as one of mode decomposition techniques. Then, the decomposed strain signals on each modal component are transformed into the modal displacement components. And the corresponding mode shapes can be also estimated by using the proper orthogonal decomposition(POD) from the measured strain signal. Thus, total displacement response could be predicted from combining the modal displacement components.

• Smart Structures and Systems
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• 제17권4호
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• pp.647-667
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• 2016

In this paper, dynamic displacement is estimated with high accuracy by blending high-sampling rate acceleration data with low-sampling rate displacement measurement using a two-stage Kalman estimator. In Stage 1, the two-stage Kalman estimator first approximates dynamic displacement. Then, the estimator in Stage 2 estimates a bias with high accuracy and refines the displacement estimate from Stage 1. In the previous Kalman filter based displacement techniques, the estimation accuracy can deteriorate due to (1) the discontinuities produced when the estimate is adjusted by displacement measurement and (2) slow convergence at the beginning of estimation. To resolve these drawbacks, the previous techniques adopt smoothing techniques, which involve additional future measurements in the estimation. However, the smoothing techniques require more computational time and resources and hamper real-time estimation. The proposed technique addresses the drawbacks of the previous techniques without smoothing. The performance of the proposed technique is verified under various dynamic loading, sampling rate and noise level conditions via a series of numerical simulations and experiments. Its performance is also compared with those of the existing Kalman filter based techniques.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.25-30
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• 2004

The magnitude of constraint effect $A_{2}$ values were experimentally estimated using displacement according to measuring positions on the non-linear elastic plastic fracture toughness estimate. For 25.4 mm thickness SS400 steel CT specimen, constraint effect $A_{2}$ values we re dependent on specimen configuration and on measured displacement near crack front. Commonly, Estimating constraint effect $A_{2}$ measuring position for displacement should be existed inside plastic region. Therefore, the ${\delta}_{5}$ method was not reliable for evaluation of constraint effect $A_{2}$ values because measuring position for displacement is in elastic region at crack growth initiation in this paper.