• 한국경영과학회:학술대회논문집
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• 한국경영과학회/대한산업공학회 2003년도 춘계공동학술대회
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• pp.208-216
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• 2003

ISO 14649 (data model for STEP-NC) is a new interface scheme or language for CAD-CAM-CNC chain under established by ISO TC184 SCI. Up to this point, the new language is mainly made for milling and turning, and other processes such as EDM will be completed in the future. Upon completion, it will be used as the international standard language for e-manufacturing paradigm by replacing the old machine-level language, so called M&G code used since 1950's. With the rich information contents included in the new language, various intelligent functions can be made by the CNC as the CNC knows what-to-make and how-to-make. In particular, On-Machine Inspection required for quality assurance in the machine level, can be done based on the information of feature­based tolerance graph. Previously, On-Machine inspection has been investigated mainly for milling operation, and only a few researches were made for turning operation without addressing the data model. In this thesis, we present a feature-based on-machine inspection process by the 4 Tasks: 1) proposing a new schema for STEP-NC data model, 2) converting the conventional tolerance scheme into that of STEP-NC, 3) modifying the tolerance graph such that the tolerance can be effectively measured by the touch probe on the machine, and 4) generating collision-free tool path for actual measurement. Task 1 is required for the incorporation of the presented method in the ISO 14649, whose current version does not much include the detailed schema for tolerance. Based on the presented schema, the tolerance represented in the conventional drafting can be changed to that of STEP-NC (Task 2). A special emphasis was given to Task 3 to make the represented tolerance accurately measurable by the touch probe on the machine even if the part setup is changed. Finally, Task 4 is converting the result of Task into the motion of touch probe. The developed schema and algorithms were illustrated by several examples including that of ISO 14649 Part 12.

• 대한기계학회논문집A
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• 제41권2호
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• pp.95-101
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• 2017

본 연구에서는 철도차량의 사고의 유형 중 가장 많이 발생되는 지그재깅 현상에 대해 이론 모델을 정립하여 선두차량의 지그재깅 거동에 대한 운동방정식을 도출하였다. 운동방정식을 풀기 위하여 미분방정식 수치해석법 중 가장 대표적인 Runge-Kutta 4차식을 사용하였고, 휠-레일 인터페이스에 의한 휠의 횡 변위는 운동에너지를 이용하여 추정하였다. 그리고 이론식을 검증하기 위하여 재그재깅 현상에서 가장 변위가 큰 연결기 위치에서의 횡 변위에 대해 시뮬레이션과 이론식을 비교한 결과 비 탈선 충돌조건에서 최대 편차율은 0.8 [%] ~ 4.7 [%] 발생하고, 탈선 충돌조건에서는 탈선이 일어나는 시점에서 차량의 횡 변위를 비교한 결과 최대 편차율이 0.6 [%] ~ 5.1 [%]로 잘 일치하는 것을 확인하였다. 이론식을 사용하여 사고나 현상을 시뮬레이션으로 재현할 때 필요한, 전체적인 거동에 부합하는 차량 간 연결의 초기 off-set량을 예측할 수 있다.

• 한국소음진동공학회논문집
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• 제15권3호
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• pp.251-258
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• 2005

The free vibration of a spinning flexible disk-spindle system supported by hydro dynamic bearings (HDB) in an HDD is analyzed by FEM. The spinning flexible disk is described using Kirchhoff plate theory and von Karman non-linear strain, and its rigid body motion is also considered. It is discretized by annular sector element. The rotating spindle which includes the clamp, hub, permanent magnet and yoke, is modeled by Timoshenko beam including the gyroscopic effect. The flexible supporting structure with a complex shape which includes stator core, housing, base plate, sleeve and thrust pad is modeled by using a 4-node tetrahedron element with rotational degrees of freedom to satisfy the geometric compatibility. The dynamic coefficients of HDB are calculated from the HDB analysis program, which solves the perturbed Reynolds equation using FEM. Introducing the virtual nodes and the rigid link constraints defined in the center of HDB, beam elements of the shaft are connected to the solid elements of the sleeve and thrust pad through the spring and damper element. The global matrix equation obtained by assembling the finite element equations of each substructure is transformed to the state-space matrix-vector equation, and the associated eigen value problem is solved by using the restarted Arnoldi iteration method. The validity of this research is verified by comparing the numerical results of the natural frequencies with the experimental ones. Also the effect of supporting structures to the natural modes of the total HDD system is rigorously analyzed.

• Structural Engineering and Mechanics
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• 제74권5호
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• pp.679-698
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• 2020

In this paper, the meshless local Petrov-Galerkin (MLPG) method is developed for dynamic analysis of non-symmetric nanocomposite cylindrical shell equations of elastic wave motion with nonlinear grading patterns under shock loading. The mechanical properties of the nanocomposite cylinder are obtained based on a micro-mechanical model. In this study, four kinds of grading patterns are assumed for carbon nanotube mechanical properties. The displacements can be approximated using shape function so, the multiquadrics (MQ) Radial Basis Functions (RBF) are used as the shape function. In order to discretize the derived equations in time domains, the Newmark time approximation scheme with suitable time step is used. To demonstrate the accuracy of the present method for dynamic analysis, at the first a problem verifies with analytical solution and then the present method compares with the finite element method (FEM), finally, the present method verifies by using the element free Galerkin (EFG) method. The comparison shows the high capacity and accuracy of the present method in the dynamic analysis of cylindrical shells. The capability of the present method to dynamic analysis of non-symmetric nanocomposite cylindrical shell is demonstrated by dynamic analysis of the cylinder with different kinds of grading patterns and angle of nanocomposite reinforcements. The present method shows high accuracy, efficiency and capability to dynamic analysis of non-symmetric nanocomposite cylindrical shell, which it furnishes a ground for a more flexible design.

• Steel and Composite Structures
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• 제36권3호
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• pp.355-367
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• 2020

The current work, present dynamic analysis of the FG-sandwich plate seated on elastic foundation with various kinds of support using refined shear deformation theory. The present analytical model is simplified which the unknowns number are reduced. The zero-shear stresses at the free surfaces of the FG-sandwich plate are ensured without introducing any correction factors. The four equations of motion are determined via Hamilton's principle and solved by Galerkin's approach for FG-sandwich plate with three kinds of the support. The proposed analytical model is verified by comparing the results with those obtained by other theories existing in the literature. The parametric studies are presented to detect the various parameters influencing the fundamental frequencies of the symmetric and non-symmetric FG-sandwich plate with various boundary conditions.

• 제어로봇시스템학회논문지
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• 제10권10호
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• pp.855-868
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• 2004

There are several types of singularities in controlling robotic manipulators: kinematic singularity, algorithmic singularity, semi-kinematic singularity, semi-algorithmic singularity, and representation singularity. The kinematic and algorithmic singularities have been investigated intensively because they are not predictable or difficult to avoid. The problem with these singularities is an unnecessary performance reduction in non-singular region and the difficulty in performance tuning. Tn this paper, we propose a method of avoiding kinematic and algorithmic singularities by applying a task reconstruction approach while maximizing the task performance by calculating singularity measures. The proposed method is implemented by removing the component approaching the singularity calculated by using singularity measure in real time. The outstanding feature of the proposed task reconstruction method (TR-method) is that it is based on a local task reconstruction as opposed to the local joint reconstruction of many other approaches. And, this method has dynamic task priority assignment feature which ensures the system stability under singular regions owing to the change of task priority. The TR-method enables us to increase the task controller gain to improve the task performance whereas this increase can destabilize the system for the conventional algorithms in real experiments. In addition, the physical meaning of tuning parameters is very straightforward. Hence, we can maximize task performance even near the singular region while simultaneously obtaining the singularity-free motion. The advantage of the proposed method is experimentally tested by using the 7-dof spatial manipulator, and the result shows that the new method improves the performance several times over the existing algorithms.

• 한국전산구조공학회논문집
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• 제18권4호통권70호
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• pp.361-372
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• 2005

본 저자의 이전연구(김문영 등, 2004)에서는 2차원 차량 모형과 전단변형 및 회전관성 효과가 고려된 현수교요소와의 상호작용을 고려한 2차원 수직응답에 대한 동적해석을 수행하였다. 본 연구에서는 전단변형 효과와 편심차량의 효과를 알아보는데 목적을 두었다. 이를 위하여 전단변형 및 회전관성 효과가 고려된 3차원 현수교의 수직, 비틂에 대한 고유진동수와 모드형상, 그리고 교량-차량 에너지로부터 라그랑지안식을 이용하여 상호작용을 고려할 수 있는 3차원 운동방정식을 유도한다. 이후 모드중칩법을 이용하여 유도된 운동방정식을 Newmark method를 사용하여 동적해석을 수행한다. 마지막으로 본 연구에서 제시한 이론을 따라 수치해석예제를 수행하여 차량의 동적거동을 분석한다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권5호
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• pp.487-495
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• 2016

In the offshore project such as semi-submersible FPU and FPSO, the free fall type life boat called TEMPSC (Totally Enclosed Motor Propelled Survival Craft) has been installed for the use of an emergency evacuation of POB (People on Board) from the topside platform. For the design of life boat arrangement for semi-submersible FPU in the initial design stage, the drop height and launch angle are required fulfill with the limitation of classification society rule and Company requirement, including type of approval as applicable when intact and damage condition of the platform. In this paper, we have been performed the numerical studies to find proper arrangement for the life boats consider drop height in various environmental conditions such as wave, wind and current. In the calculations, the contributions from static and low frequency (LF) motions are considered from the hydrodynamic and mooring analysis as well as damage angle from the intact and damage stability analysis. Also, Air-gap calculation at the life boat positions has been carried out to check the effect on the life boat arrangement. The air-gap assessment is based on the extreme air-gap method includes the effect of 1st order wave frequency (WF) motions, 2nd order low frequency roll/pitch motion, static trim/heel and set down.

• 재활복지공학회논문지
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• 제9권1호
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• pp.67-72
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• 2015

팔의 사용이 자유롭지 못한 장애인들을 위하여 발의 움직임 검출을 통하여 로봇 팔을 제어할 수 있는 시스템을 구현하였다. 발의 움직임에 대한 영상을 얻기 위하여 양쪽 발 앞에 두 대의 카메라를 설치하였으며, 획득된 영상에 대해 LabView 기반 Vision Assistant를 이용하여 다중 관심영역을 설정한 후, 좌/우영역내에서 검출된 좌/우, 상/하 엣지를 기반으로 발의 움직임을 검출하였다. 좌/우 두발의 영상으로부터 좌/우 엣지와 상/하 엣지 검출 수에 따라 6관절 로봇 팔을 제어할 수 있는 제어용 데이터를 시리얼 통신을 통해 전송한 후 로봇 팔을 발로 상/하, 좌/우 제어할 수 있는 시스템을 구현하였다. 실험 결과 0.5초 이내의 반응속도와 88% 이상의 동작 인식률을 얻을 수 있었다.

• Archives of Reconstructive Microsurgery
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• 제1권1호
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• pp.31-38
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• 1992

The management of giant cell tumor involving juxta-articular portion has always been a difficult problem. In certain some giant cell tumors with bony destruction, a wide segmental resection may be needed for preventing to recur. But a main problem is preserving of bony continuity in bony defect as well as preservation of joint function. The traditional bone grafts have high incidence in recurrence rate, delayed union, bony resorption, stress fracture despite long immobilization and stiffness of adjuscent joint. We have attemped to overcome these problems by using a microvascular technique to transfer the fibula with peroneal vascular pedicle as a living bone graft. From Apr. 1984 to Nov. 1990, we performed the reconstruction of wide bone defect after segmental resection of giant cell tumor in 4 cases, using Vascularized Fibular Graft, which occur at the distal radius in 3 cases and at the proximal tibia in 1 case. An average follow-up was 2 years 8 months, average bone defect after wide segmental resection of lesion was 11.4cm. These all cases revealed good bony union in average 6.5months, and we got the wide range of motion of adjacent joint without recurrence and serious complications.