• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.197-200
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• 2001

본 논문에서는 특정한 형태의 제약 즉, 매니퓰레이터의 자유도와 주어진 제약조건의 차원의 차이가 1이며, 매니퓰레이터의 동역학을 작업영역에서의 축차모델로 나타내었을 때, 변환행렬이 단위행렬로 나타나는 제약을 가지는 불확실한 로봇 매니퓰레이터의 위치/힘 추종을 위한 적응제어기를 제안한다. 제안된 제어기는 비선형 좌표변환을 통하여 얻어진 로봇의 축차모델(reduced-order model)을 이용하여 위치제어와 힘제어의 문제를 분리한다. 특히, 비선형 동적 필터를 이용하여 위치의 측정만을 필요로 하며, 적응제어 기법을 통하여 전역 점근적인 안정성을 보장한다.

• The Transactions of the Korea Information Processing Society
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• v.2 no.3
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• pp.390-396
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• 1995

One of the advantages of computer graphics is that it enables to view an object on different viewpoints and different angles. Therefore, a computer graphics system should be able to rotate an arbitrary object by an arbitrary angle about an arbitrary axis. This is usually done by rotating vertices that represent an object and connecting them. Hence an image may have many vertices, it is important to be able to rotate each of them quickly. Therefore, this paper is interested in a rotation matrix computation method that consists of the smallest number of computational steps. This pater proposes an algorithm that computes rotation matrix to rotate a 3 dimensional image about an arbitrary axis quickly.

• Journal of the Korean Society of Radiology
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• v.13 no.5
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• pp.801-809
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• 2019

Existing Gamma Knife Radiosurgery(GKRS) for large lesions is often conducted in stages with volume or dose partitions. Often in case of volume division the target used to be divided into sub-volumes which are irradiated under the determined prescription dose in multi-sessions separated by a day or two, 3~6 months. For the entire course of treatment, treatment informations of the previous stages needs to be reflected to subsequent sessions on the newly mounted stereotactic frame through coordinate transformation between sessions. However, it is practically difficult to implement the previous dose distributions with existing Gamma Knife system except in the same stereotactic space. The treatment area is expanding because it is possible to perform the multistage treatment using the latest Gamma Knife Platform(GKP). The purpose of this study is to introduce the image-coregistration based on the stereotactic spaces and the strategy of multistage GKRS such as the determination of prescription dose at each stage using new GKP. Usually in image-coregistration either surgically-embedded fiducials or internal anatomical landmarks are used to determine the transformation relationship. Author compared the accuracy of coordinate transformation between multi-sessions using four or six anatomical landmarks as an example using internal anatomical landmarks. Transformation matrix between two stereotactic spaces was determined using PseudoInverse or Singular Value Decomposition to minimize the discrepancy between measured and calculated coordinates. To evaluate the transformation accuracy, the difference between measured and transformed coordinates, i.e., ${\Delta}r$, was calculated using 10 landmarks. Four or six points among 10 landmarks were used to determine the coordinate transformation, and the rest were used to evaluate the approaching method. Each of the values of ${\Delta}r$ in two approaching methods ranged from 0.6 mm to 2.4 mm, from 0.17 mm to 0.57 mm. In addition, a method of determining the prescription dose to give the same effect as the treatment of the total lesion once in case of lesion splitting was suggested. The strategy of multistage treatment in the same stereotactic space is to design the treatment for the whole lesion first, and the whole treatment design shots are divided into shots of each stage treatment to construct shots of each stage and determine the appropriate prescription dose at each stage. In conclusion, author confirmed the accuracy of prescribing dose determination as a multistage treatment strategy and found that using as many internal landmarks as possible than using small landmarks to determine coordinate transformation between multi-sessions yielded better results. In the future, the proposed multistage treatment strategy will be a great contributor to the frameless fractionated treatment of several Gamma Knife Centers.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.5
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• pp.1640-1648
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• 1991

본 연구에서는 이러한 편사 함수 최소화의 방법을 적용함에 있어 보다 안정된 수렴성과 계산 시간을 단축시키기 위하여 근접 위치 방법(near position method)을 개 발하여 적용하였다. 근접 위치 방법이란 이론적 해석법으로 풀기가 불가능한 기구학 을 갖는 6관절 로봇을 반복적 해석법을 사용한다는 것을 전제로 하여, 초기 위치를 목 표 위치에 가능한 근접하게 잡아서 반복 계산을 수행하는 방법으로써 로봇의 기구학적 자세에 따른 수렴의 불안정성을 방지하고, 계산 시간을 단축하는데 그 목적이 있다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.221-226
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• 1995

터빈 익렬, 펌프 익차, 원형 냉각탑, 치차 등과 같이 동일한 형상이 원주 방향으로 반복되어 있는 순환 대칭 구조물의 진동특성을 유한 요소법을 사용하여 해석하는 경우에 전체구조를 모델링하는 대신에 구조물을 동일한 형상의 부분구조로 분할하여 부분구조 한개만을 모델링하고 분할된 경계에서 적절한 경계조건을 부과하여 진동해석을 수행함으로서 컴퓨터 기억용량을 절감시키고 계산시간을 단축할 수 있는 방법이 널리 사용되고 있다. Orris and Petyt[1]는 부분구조의 양쪽 분할 경계면, 즉 연결 경계상에 있는 절점변위의 상관관계를 복소파동전파식을 이용해서 구하여 부분구조의 감소된 복소강성행렬 및 질량행렬을 만들고 실수부와 허수부를 분리하여 유한요소해석을 수행하는 방법을 제안하였다. 유한요소 프로그램 ANSYS[2]에서는 이와 같은 방법을 사용하고 있다. Thomas[3]는 순회 정규모드를 이용하였고, 참고문헌[4]에서는 순회행렬을 이용하였다. 또한 유한요소 프로그램 MSC/NASTRAN[5]에서는 푸리에 급수를 이용하고 유한요소 절점의 위치 및 변위를 원통 좌표계를 표현하여 순환대칭구조물의 유한요소해석을 수행할 수 있도록 되어있다. 본 논문에서는 순환 대칭구조물의 형상의 주기성과 순환성을 고려하여 이산퓨리에 변환을 이용함으로써 순환대칭구조물의 유한요소진동해석을 체계적으로 저용량의 컴퓨터에서 신속하고 정확하게 수행할 수 있는 방법을 제안하고자 한다.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1782-1783
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• 2011

실내공간상에서 3차원 실시간 위치를 결정하는 다양한 측지기법들이 존재하지만 $100{\mu}m$ 이하 계측기 수준의 정밀도를 측정하는 방법은 여전히 Laser Theodolite 신호를 사용할 수밖에 없다. Rotary-Laser Automatic Theodolite(R-LAT)는 Fan Laser Beam을 주사하면서 회전시킨 후 주어진 공간의 수직과 수평을 계측하는 Laser Transmitter의 한 종류이다. 본 논문에서는 R-LAT에서 발생되는 Fan Laser Beam 신호를 취득할 수 있는 센서와 증폭회로의 개발을 통하여 3차원 공간좌표에 대한 회전변환행렬로 이루어진 알고리즘을 제안하고 실험을 통하여 기존 Laser Tracker에서 구해지는 공간좌표와 상호 비교하였다.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.12
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• pp.133-142
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• 1999

We introduce the algorithms of 2-D and 3-D position estimation using 2-D vision sensors. The sensors used in this research issue red laser slit light to the body. So, it is very convenient to obtain the coordinates of corner point or edge in sensor coordinate. Since the measured points are normally not fixed in the body coordinate, the additional conditions, that corner lines or edges are straight and fixed in the body coordinate, are used to find out the position and orientation of the body. In the case of 2-D motional body, we can find the solution analytically. But in the case of 3-D motional body, linearization technique and least mean squares method are used because of hard nonlinearity.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.6
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• pp.36-44
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• 2003

In this paper, an analytic solution method is proposed to overcome the numerical problems when the slewing dynamics of hybrid coordinate systems is investigated via time finite element analysis. It is shown that the dynamics of the hybrid coordinate systems is governed by the coupled dual differential equations for both slewing and structural modes. Structural modes are transformed into the time-based modal coordinates and analytic spatial propagation equations are derived for each space-dependent time mode. Slew angle history is obtained analytically by appropriate applications of the boundary conditions and structural propagation is re-calculated using the slew angle. Numerical examples are demonstrated to validate the proposed analytic method in comparison to the existing state transition matrix method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.5385-5391
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• 2013

As on-line purchases is activated, customers' demand increases for the realistic and accurate digital information of a product design. In this paper, we propose a practical method that can generate a realistic 3D model of a real product using a 3D geometry obtained by a 3D scanner and its photographic images. In order to register images to the 3D geometry, the camera focal length, the CCD scanning aspect ratio and the transformation matrix between the camera coordinate and the 3D object coordinate must be determined. To perform this 2D-3D registration with consideration of computational complexity, a three-step method is applied, which consists of camera calibration, determination of a temporary optimum translation vector (TOTV) and nonlinear optimization for three rotational angles. A case study for a metallic coated industrial part, of which the colour appearance is hardly obtained by a 3D colour scanner has performed to demonstrate the effectiveness of the proposed method.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.1
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• pp.693-700
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• 2009

For real-time precise GPS data processing such as a long baseline network RTK (Real-Time Kinematic) survey, PPP (Precise Point Positioning) and monitoring of ionospheric/tropospheric delays, it is necessary to guarantee accuracy comparable to IGS (International GNSS Service) precise orbit with no latency. As a preliminary study for determining near real-time satellite orbits, the general procedures of satellite orbit determination, especially the dynamic approach, were studied. In addition, the transformation between terrestrial and inertial reference frames was tested to integrate acceleration. The IAU 1976/1980 precession/nutation model showed a consistency of 0.05 mas with IAU 2000A model. Since the IAU 2000A model has a large number of nutation components, it took more time to compute the transformation matrix. The classical method with IAU 2000A model was two times faster than the NRO (non-rotating origin) approach, while there is no practical difference between two transformation matrices.