• 대한기계학회논문집A
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• 제28권10호
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• pp.1612-1620
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• 2004

This study presents methods to estimate elastic-plastic crack opening displacement (COD) fur circumferential through-wall cracked pipes for the Leak-Before-Break (LBB) analysis of pressurized piping. Proposed methods are based not only on the GE/EPRI approach but also on the reference stress approach. For each approach, two different estimation schemes are given, one for the case when full stress-strain data are available and the other fur the case when only yield and ultimate tensile strengths are available. For the GE/EPRI approach a robust way of determining the Ramberg-Osgood (R-O) parameters is proposed, not only fur the case when detailed information on full stress-strain data is available but also for the case when only yield and ultimate tensile strengths are available. The COD estimates according to the GE/EPRI approach, using the R-O parameters determined from the proposed R-O fitting procedures, generally compare well with the published pipe test data. For the reference stress approach, the COD estimates according to the method based on both full stress-strain data and limited tensile properties are in good agreement with pipe test data. In conclusion, experimental validation given in the present study provides sufficient confidence in the use of the proposed method to practical LBB analyses even though when information on material's tensile properties is limited.

• 한국전산구조공학회논문집
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• 제20권5호
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• pp.623-628
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• 2007

마찰형 감쇠를 갖는 구조물은 구조물의 고유주기, 하중의 특성, 그리고 외부하중에 대한 마찰력의 상대적인 크기에 따라 강한 비선형성을 나타내므로, 구조물의 최대응답을 예측하기 매우 어렵다. 기존의 연구에서는 비선형 시스템을 등가의 선형 시스템으로 치환하거나, 구조물의 비선형 시간이력해석을 통한 응답스펙트럼 분석에 의한 간단한 확률해석에 의해 수행되었다. 지진 하중은 불확실성과 불규칙성을 갖고 있기 때문에 확률적으로 정의된다면, 지진하중을 받는 마찰형 감쇠를 갖는 구조물의 응답 역시 확률분포를 나타낼 것이다. 본 논문에서는 Kanai-Tajimi 필터를 이용해 생성된 인공지진하중에 대해 마찰형 감쇠를 갖는 구조물의 비선형 시간이력 해석이 수행되었다. 그리고 정규분포 확률밀도 함수에 선형 회귀분석을 통해 얻어진 구조물의 주기와 마찰력의 크기에 의한 변수를 업데이트 시킨 마찰형 감쇠를 갖는 구조물의 변위 응답 확률밀도함수식이 제시된다.

• 전자공학회논문지SC
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• 제42권5호
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• pp.1-12
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• 2005

이동로봇과 작업로봇의 직결연결 형태인 이동매니퓰레이터는 원자로 내부와 같은 위험한 작업환경에서 다양한 일한 처리하기위해 유용한 시스템이라 할 수 있다. 하부의 이동로봇은 non-holonomic 시스템이고 상부의 작업로봇의 결합으로 인하여 기구학적 잉여자유도를 갖고 있다. 그러나 주행 중 작업공간 확보로 인하여 고정식 매니퓰레이터보다 더 효율적인 작업이 가능 하다고 할 수 있다. 본 논문에서는 영상정보에 의한 물체인식 및 최적주행을 수행하기 위하여 이동로봇에 장착된 능동카메라에 인식된 영상과 실제 물체간의 기하학적 관계를 이용하여 직교좌표상의 물체의 위치를 추정할 수 있도록 하였다. 두 번째로 시스템의 위치변위 및 영상정보를 이용하여 물체위치를 추정하고 동차행렬을 이용하여 이동매니퓰레이터의 현 위치와 물체간의 최적경로를 결정하는 방법을 제시하였다. 제시한 방법을 시뮬레이션과 이동매니퓰레이터를 이용한 실험데이터분석을 통하여 유효성을 제시하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1225-1230
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• 2003

In this study, Real-time estimation and compensation procedure are developed for the laser interferometer. This system is designed with homodyne quadrature-phase detection method using the Laser interferometer. The errors in this system are due to noise, disturbance and undefined model dynamics. DSP(Digital Signal Processor) is applied for real time compensation of these errors. This estimator and compensation is verified with measurement test.

• 한국통신학회논문지
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• 제21권11호
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• pp.2776-2788
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• 1996

A new feature-based motion parameter estimation for arbitrary-shaped regions is proposed. Existing motion parameter estimation algorithms such as gradient-based algorithm require iterations that are very sensitive to initial values and which often converge to a local minimum. In this paper, the motion parameters of an object are obtained by solving a set of linear equations derived by the motion of salient feature points of the object. In order to estimate the displacement of the feature points, a new process called the "bi-directional correspondence scheme" is proposed to ensure the robjstness of correspondence. The proposed correspondence scheme iteratively selects the feature points and their corresponding points until unique one-to-one correspondence is established. Furthermore, initially obtained motion paramerters are refined using an iterative method to give a better performance. The proposed algorithm can be used for motion estimationin object-based image coder, and the experimental resuls show that the proposed method outperforms existing schemes schemes in estimating motion parameters of objects in image sequences.sequences.

• Journal of Mechanical Science and Technology
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• 제15권8호
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• pp.1079-1089
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• 2001

This paper proposes J and CTOD estimation schemes applied to fracture toughness testing, covering typical homogeneous and bi-material specimens. Recommendations are based on the plastic limit analysis (either slip line field or finite element limit analyses), assuming the rigid plastic material behavior. The main outcome of the present study is that the J and CTOD estimation schemes (both codified and non-codified), recommended for homogeneous specimens, can be equally used for bi-material specimens with interface cracks. The effect of yield strength mismatch in bi-material specimens on the J-integral CTOD is discussed.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2007년도 하계종합학술대회 논문집
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• pp.327-328
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• 2007

A contour shape matching based pixel motion estimation is proposed. The pixel motion information is very useful to compensate the motion artifact generated at the specific gray level contours in the moving image for subfield gray-scale display devices. In this motion estimation method, the gray level boundary contours are extracted from the input image. Then using contour shape matching, the most similar contour in next frame is found, and the contour is divided into segment unit. The pixel motion vector is estimated from the displacement of the each segment in the contour by segment matching. From this method, more precise motion vector can be estimated and this method is more robust to image motion with rotation or from illumination variations.

• Smart Structures and Systems
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• 제10권1호
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• pp.15-31
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• 2012

This study proposes an active control method to suppress beam-rotating machinery system vibrations. The present control method is a combination of the fuzzy input estimation method (FIEM) and linear quadratic Gaussian problem (LQG) algorithms. The FIEM can estimate the unknown input and optimal states by measuring the dynamic displacement, the optimal estimated states into the feedback control; thereby obtaining the optimal control force for a random linear system. Active vibration control of a beam-rotating machinery system is performed to verify the feasibility and effectiveness of the proposed algorithm. The simulation results demonstrate that the proposed method can suppress vibrations in a beam-machine system more efficiently than the conventional LQG method.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.494-504
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• 2008

Successful design, construction and maintenance of NATM tunnel demands prediction, control, stability estimation and monitoring of surface settlement, gradient and ground displacement with high accuracy. Back analysis using measured data and forward analysis have been and are indispensable tools to achieve this goal. Sakurai provided the hazard warning levels for assessing the stability of tunnels using the relation of critical strain and apparent Young's modulus. This paper performed the estimation of tunnel stability on construction. Firstly, the apparent Young's modulus concept and back analysis method is introduced for the assessment of tunnel safety during excavation a brief framework. Secondly, this paper deals with case study using "Apparent Young's modulus" and "Back analysis" for the purpose of estimating the stability of NATM tunnel in Korea. Finally, a general method that can be estimated the tunnel stability discussed by a flow chart.

• 전기학회논문지
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• 제57권12호
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• pp.2291-2299
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• 2008

Hall effect force sensors have been used to measure clamping force in conventional Electric Parking Brake(EPB) systems. Estimation of clamping force without the sensors has drawn attentions due to mounting space limitations and cost issues. Removing the sensor requires the estimation of the initial contact point where the clamping force is effectively applied to the brake pads. In this paper, we propose how to estimate the initial contact point finding the relation between the angular velocity of an actuator and the initial contact point. For force estimation a look-up table is used as a function of the displacement of parking cable from the initial contact point. The proposed method is validated by experiments. From the experimental results we observe that the proposed method satisfies the specifications. The designed method is also able to estimate clamping force although parking cables are loosened and brake pads are worn out. Applying the proposed method enables manufacturing of low cost EPB systems.