• 한국CDE학회논문집
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• 제6권4호
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• pp.222-228
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• 2001

In the milling operation, the burr can be generated on the intersection of cutting tool and workpiece. Due to burr formation, we expect lower efficiency in the operation and the cost increase. In order to understand the burr formation mechanism in the milling operation on the arbitrary feature, we developed an algorithm to analyse and predict the exit burr formation mechanism. Firstly, the recognition of arbitrary shaped workpiece was done through the CAD data. This data includes point information on the vertices of the workpiece. Secondly, tile CAM data regarding tool geometry, tool path, cutting speed, and material data are retrieved to simulate the actual cutting process. Thirdly, we predict the exit burr formation on the edge of workpiece based on the geometric analysis. Lastly, an algorithm implemented in the Windows environment to visualize the burr formation simulation. With this information, we can predict which portion of workpiece would have the exit burr in advance so that we call manage to find a way to minimize the edit burr formation in the actual cutting.

• Journal of Mechanical Science and Technology
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• 제19권2호
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• pp.549-557
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• 2005

The requirements of multi-resolution models of feature-based solids, which represent an object at many levels of feature detail, are increasing for engineering purposes, such as analysis, network-based collaborative design, virtual prototyping and manufacturing. To provide multi-resolution models for various applications, it is essential to generate adequate solid models at varying levels of detail (LOD) after feature rearrangement, based on the LOD criteria. However, the non-commutative property of the union and subtraction Boolean operations is a severe obstacle to arbitrary feature rearrangement. To solve this problem we propose history-based Boolean operations that satisfy the commutative law between union and subtraction operations by considering the history of the Boolean operations. Because these operations guarantee the same resulting shape as the original and reasonable shapes at the intermediate LODs for an arbitrary rearrangement of its features, various LOD criteria can be applied for multi-resolution modeling in different applications.

• 한국CDE학회논문집
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• 제10권6호
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• pp.432-443
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• 2005

Recent three-dimensional feature-based CAD systems based on solid or non-manifold modelling functionality have been widely used for product design in manufacturing companies. When product models associated with features are used in various downstream applications such as analysis, however, simplified and abstracted models at various levels of detail (LODs) are frequently more desirable and useful than the full detailed model. To provide multi-resolution models, the features need to be rearranged according to a criterion that measures the significance of the feature. However, if the features are rearranged, the resulting shape is possibly different from the original because union and subtraction Boolean operations are not commutative. To solve this problem, in this paper, the new concept of the effective zone of a feature is defined and identified using Boolean algebra. By introducing the effective zone, an arbitrary rearrangement of features becomes possible and arbitrary LOD criteria may be selected to suit various applications. Besides, because the effective zone of a feature is independent of the data structure of the model, the multi-resolution modelling algorithm based on the effective zone can be implemented on any 3D CAD system based on conventional solid representations as well as non-manifold topological (NMT) representations.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.1263-1266
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• 1998

In this paper, we propose an optimal feature extraction method for normally distributed multiclass data. We search the whole feature space to find a set of features that give the smallest classification error for the Gaussian ML classifier. Initially, we start with an arbitrary feature vector. Assuming that the feature vector is used for classification, we compute the classification error. Then we move the feature vector slightly and compute the classification error with this vector. Finally we update the feature vector such that the classification error decreases most rapidly. This procedure is done by taking gradient. Alternatively, the initial vector can be those found by conventional feature extraction algorithms. We propose two search methods, sequential search and global search. Experiment results show that the proposed method compares favorably with the conventional feature extraction methods.

• 한국산학기술학회논문지
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• 제15권9호
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• pp.5750-5757
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• 2014

본 논문은 의도하지 않게 카메라에 입력되는 회전, 병진 움직임뿐만 아니라 확대 축소에 의한 움직임을 SIFT 기법을 이용하여 추정하고 제거하는 영상 안정화 기법을 제시한다. 또한 영상 분할 및 통합 방법을 이용하여 움직이는 물체가 영상에 입력되었을 경우에도 이러한 외란을 제거하고 영상 안정화를 수행하도록 한다. 제시된 방법은 다른 방법과 결과를 비교하는 실험을 수행하여 성능이 우수함을 검증한다.

• 한국멀티미디어학회논문지
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• 제5권3호
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• pp.255-262
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• 2002

윤곽선 시퀀스는 임의 형상을 간단하면서도 정확하게 표현할 수 있는 좋은 표현법이 될 수 있다. 그러나, 형상을 구성하는 화소로부터 쉽게 구할 수 있는 면적, 무게중심, 오리엔테이션 방향, 투영 히스토그램 등과 같은 형상 특징들을 윤곽선 시퀀스로부터 직접 구하기는 어렵기 때문에, 윤곽선 시퀀스를 임의 형상에 대한 표현법으로 잘 사용하지 못하였다. 본 논문에서는 형상 내부의 연속된 화소들로 구성된 수직(또는 수평)의 라인 세그먼트를 의미하는 크로스 섹션 개념을 이용하여, 윤곽선 시퀀스로부터 형상 특징들을 쉽게 구할 수 있음을 보인다. 윤곽선 시퀀스를 한번 순차적으로 탐색함으로써 크로스 섹션을 효율적으로 구할 수 있는 방법을 제안한다. 또한, 이진 영상으로부터 여러 형상의 윤곽선 시퀀스를 자동으로 추출할 수 있는 효율적인 방법도 함께 제안한다. 제안된 방법들은 형상 내부에 홀(hole)이 있는 경우에도 적용할 수 있다. 결과적으로, 윤곽선 시퀀스가 임의 형상 영역에 대한 매우 효과적인 표현이 될 수 있음을 밝힌다.

• 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.

• 한국멀티미디어학회논문지
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• 제9권3호
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• pp.287-295
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• 2006

본 논문은 임의의 영역 안에 존재하는 텍스처를 검색하기 위한 wavelet과 Gabor기반 텍스처 표현 기법을 제안하고 이들의 검색성능을 평가한다. 지금까지 Gator 평면에서의 평균과 표준편차 특징 기술자가 직사각형안의 텍스처를 표현하기에 가장 적합한 것으로 알려져 있다. 하지만 임의의 영역 안의 물체를 표현하는 기술이 실제 검색이나 여러 다른 텍스처 표현 응용 예에 더욱 필요한 실정이다. 본 연구에서는 wavelet과 Gabor 필터에 기반한 특징 추출법을 제안하고 이들을 실제 텍스처 데이터 베이스에 적용해 본 결과, wavelet기반 특징 기술자가 Gator기반 기술자에 비하여 더욱 효과적임을 발견하였다. 특히 wavelet평면에서 표준편차와 엔트로피 특징을 사용함으로써 가장 좋은 검색 성능을 냄을 알 수 있었다. 또한, 본 논문에서는 다양한 실제 텍스처 영상을 가지고 wavelet과 Gator에 기반한 다양한 특징벡터에 따른 검객 성능을 평가하였다.

• Journal of Biosystems Engineering
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• 제23권4호
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• pp.381-390
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• 1998

An algorithm to extract the 3-D geometric information of a static object was developed using a set of 2-D computer vision system and a laser structured lighting device. As a structured light pattern, multi-parallel lines were used in the study. The proposed algorithm was composed of three stages. The camera calibration, which determined a coordinate transformation between the image plane and the real 3-D world, was performed using known 6 pairs of points at the first stage. Then, utilizing the shifting phenomena of the projected laser beam on an object, the height of the object was computed at the second stage. Finally, using the height information of the 2-D image point, the corresponding 3-D information was computed using results of the camera calibration. For arbitrary geometric objects, the maximum error of the extracted 3-D feature using the proposed algorithm was less than 1~2mm. The results showed that the proposed algorithm was accurate for 3-D geometric feature detection of an object.

• International Journal of CAD/CAM
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• 제6권1호
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• pp.89-97
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• 2006

This paper presents a novel approach for non-iterative surface smoothing with feature preservation on arbitrary meshes. Laplacian operator is performed in a global way over the mesh. The surface smoothing is formulated as a quadratic optimization problem, which is easily solved by a sparse linear system. The cost function to be optimized penalizes deviations from the global Laplacian operator while maintaining the overall shape of the original mesh. The features of the original mesh can be preserved by adding feature constraints and barycenter constraints in the system. Our approach is simple and fast, and does not cause surface shrinkage and distortion. Many experimental results are presented to show the applicability and flexibility of the approach.