5축 가공의 특이영역에서 공구궤적 오차

소범식(Bumsik So),정융호(Yoongho Jung),윤재득(Jaedeuk Yun) (사)한국CDE학회 2009 한국CDE학회 논문집 Vol.14 No.1

This paper proposes an analytical method of evaluating the maximum error by modeling the exact tool path for the tool traverse singular region in five-axis machining. It is known that the NC data from the inverse kinematics transformation of 5-axis machining can generate singular positions where incoherent movements of the rotary axes can appear. These lead to unexpected errors and abrupt operations, resulting in scoring on the machined surface. To resolve this problem, previous methods have calculated several tool positions during a singular operation, using inverse kinematics equations to predict tool trajectory and approximate the maximum error. This type of numerical approach, configuring the tool trajectory, requires much computation time to obtain a sufficient number of tool positions in a region. We have derived an analytical equation for the tool trajectory in a singular area by modeling the tool operation into a linear and a nonlinear part that is a general form of the tool trajectory in the singular area and that is suitable for all types of five-axis machine tools. In addition, we have evaluated the maximum tool-path error exactly, using our analytical model. Our algorithm can be used to modify NC data, making the operation smoother and bringing any errors to within tolerance.

가정용 냉장고의 얼음 완전 취출 메커니즘의 설계

우민수(Minsu Woo),정융호(Yoongho Jung) 한국산학기술학회 2020 한국산학기술학회논문지 Vol.21 No.3

얼음을 제공하는 기능이 구비된 냉장고는 대부분 냉장고 내부의 얼음 저장소에 미리 얼음을 채워 두고 사용자가 필요할 때 많은 양의 얼음을 취출할 수 있도록 하고 있다. 그러나 냉장고의 얼음 저장소에 얼음이 채워진 상태로 냉장고가 장기간 사용되지 않거나 정상적인 동작 중에도 시간이 경과하면 얼음이 서로 엉기는 현상이 발생한다. 이렇게 엉긴 얼음 덩어리를 분리시키는 메커니즘이 구비되어 있으나 얼음 엉김 현상이 심할 경우 얼음이 완전히 취출되지 못하는 문제가 있다. 본 연구에서는 이러한 문제를 해결하기 위해 얼음이 엉기는 과정과 얼음의 분리력에 관한 기존의 연구를 조사하였고, 인위적으로 얼음을 엉기게 하여 다양한 조건에서 얼음의 취출 정도를 실험하였다. 이 과정에서 얼음의 취출을 방해하는 기존 얼음 저장소 형상의 문제점에 착안하여 이를 개선하기 위한 형상과, 완전 취출을 위해 얼음 분쇄 메커니즘의 작동 반경을 넓히는 새로운 메커니즘을 제안하였다. 제안된 메커니즘의 시제품을 제작하고 실제 냉장고에 적용하여 얼음이 완전 취출됨을 검증하였다. 그 결과 기존 얼음 저장소의 형상과 분쇄 메커니즘에서 얼음 취출률이 65%정도이었으나, 제안된 형상과 메커니즘에서는 완전히 추출되었다. A refrigerator equipped with an ice dispenser has ice cubes in its ice bucket to discharge the required amount of ice. On the other hand, the ice cubes in the bucket may clump together if the refrigerator is filled with ice and is not used for a long time or during normal operation. Although a mechanism for separating the ice mass is provided, the ice mass cannot be removed completely if the ice blocking is severe. To solve this problem, after investigating the existing research on the process of ice entanglement and the separation force, this study tested ice extraction under a range of conditions of artificially entangled ices. In this process, new mechanisms are proposed to resolve the problem of existing ice storage features that prevent the extraction of ice and to expand the working radius of the icebreaking mechanism for full extraction. The prototype of the proposed mechanism was also fabricated in an actual refrigerator. As a result, the proposed shape and mechanism could extract the ice cubes in the bucket completely, while the existing ice dispenser could extract only 65%.

기하학적인 방법을 이용한 3 Rotary 형식 5축 가공기의 후처리 방법

윤재득(Jaedeuk Yun),정융호(Yoongho Jung),박도현(Dohyun Park) (사)한국CDE학회 2009 한국CDE학회 논문집 Vol.14 No.5

This paper presents a post-processing algorithm for 5-axis machines with three rotary axes (3R-2L type). 5-axis machining needs the postprocessor for converting cutter location (CL) data to machine control (NC) data. The existing methods for post-processing use inverse kinematics equations from forward kinematics. However in case of 5-axis machines with three rotary axes, the inverse kinematics equations are not induced directly since the forward kinematics equations are non-linear. In order to get the joint values from the forward kinematics equations, previous algorithms use numerical method for the post-processing, which needs searching algorithms with computation time and may result in fail. This paper proposes a geometric method for the post-processing of 3 rotary type 5-axis machines. Our algorithm has three advantages: first, it does not need establishing forward kinematics equations. Second, it is reliable method that eliminates any numerical methods for the inverse kinematics, resulting in the exact solution. Finally, the proposed algorithm can also be applied to 2R-3L type of 5-axis machines.

Performance Evaluation of a Crank-driven Compressor and Linear Compressor for a Household Refrigerator

Minchan Park(박민찬),Yoongho Jung(정융호),Jaeyeol Lee(이재열),Jaekeun Lee(이재근),Youngchull Ahn(안영철) 한국동력기계공학회 2017 동력시스템공학회지 Vol.21 No.5

주응력의 방향을 이용한 필라멘트 와인딩 복합재의 섬유 궤적 생성

윤재득(Jaedeuk Yun),정융호(Yoongho Jung),푸쟌훼이(Jianhui Fu) (사)한국CDE학회 2014 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2014 No.2

필라멘트 와인딩은 유리나 탄소 섬유를 맨드릴에 감아서 성형하는 공법으로 고압 밀폐 용기나 각종 파이프 등을 제작할 때 사용된다. 필라멘트 와인딩 궤적을 생성할 때는 반드시 구조물에 가해지는 하중의 방향을 고려해서 감겨지는 섬유의 방향을 결정해야 강도 높은 복합재 구조물을 제작 할 수 있다. 본 논문에서는 벡터장에 접하는 곡선을 의미하는 스트림라인을 사용하여 섬유 궤적을 생성하는 방법을 제시하고자 한다. 제안한 방법을 사용하면 구조해석을 통해 생성된 주응력 방향과 정확히 일치하는 섬유의 궤적을 생성할 수가 있다. 또한, 와인딩을 수행할 때 미끄러짐과 같은 현상이 발생하지 않는 섬유 궤적을 생성하는 방법을 제시하였다. 본 연구에서 제안한 방법을 사용하여 동일한 맨드릴 형상에 대해 다양한 하중조건에서 섬유 궤적을 생성하였으며, 그 결과 각각의 하중 조건에 대하여 최적의 섬유 궤적을 생성하였다. 제안한 방법은 삼각면으로 근사화한 모델인 STL 모델을 사용하여 섬유 궤적을 생성하기 때문에 복잡한 형상에도 적용이 가능하다.

5축 밀링가공기의 직교 특성을 이용한 역기구학 방정식의 유도

소범식(Bumsik So),정융호(Yoongho Jung) (사)한국CDE학회 2008 한국CDE학회 논문집 Vol.13 No.2

직교 투영과 굽힘 투영의 혼합 알고리즘

김태경(Taegyeong Kim),정융호(Yoongho Jung),배원중(Wonjung Bae) (사)한국CDE학회 2011 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2011 No.1

In this paper, a new method was suggested that 2D letters 2D pictures were reflected in 3D curved surface. The method suggests that a square circumscribed with shape of diagram is designed in 3D curved surface using bending projective method and distance reduced to the normal direction of projected direction of reflected circumscribed quadriateral is measured to calculate reduction ratio for size of square before reflection. Reduction ratio calculated in data of shapes reflected on surface is respectively divided to create new reflected shapes that compensate shapes reduced during reflection process. Suggested method shows the least distorted shape compared to the existing reflection methods when reflecting 2D diagram shapes in 3D curved surface.

윤곽 가공을 위한 삼각 스플라인을 이용한 오프셋 곡선의 생성

고구용(Jiulong Gu),윤재득(Jaedeuk Yun),정융호(Yoongho Jung) (사)한국CDE학회 2010 한국CDE학회 논문집 Vol.15 No.4

This paper presents algorithms for computing offsets of freeform curves. The approach first divides the original curve into several segments at the inflexion points. Based on the obtained new control polygon and its offsets, quadratic trigonometric splines are constructed to approximate the offset curves. Finally, the shape parameter value of trigonometric spline is determined to satisfy the required tolerance. The degree of the output curve is two, independent of the original curve’s degree. Because of the great controllability, the proposed method can generate a completely overestimating offset curve by adjusting the value of the shape parameter, which guarantees no overcutting in NC machining. Furthermore, it also produces the lowest number of control points compared with other works.

[기술논문] 토션바 트렁크의 팝업량 산포 분석을 위한 해석모델

손성민(Sungmin Son),윤재득(Jaedeuk Yun),정융호(Yoongho Jung),임향수(Hyangsoo Yim),장국진(Kookjin Jang) 한국자동차공학회 2014 한국 자동차공학회논문집 Vol.22 No.2

A four-link mechanism consisting of torsion bars is used for opening the trunk lid in most midsize sedans. When the weight of the lid is in equilibrium with the spring force exerted by torsion bars, the lid stops opening at a pop-up height. However, the actual pop-up height has large deviations from the specified height even with the same parts in the same car model, which leads to quality issues. Automotive manufacturers have experienced this deviation problem despite much effort to resolve it. In this research, we developed a multi-body dynamics model for the analysis of pop-up deviation of a trunk lid with torsion bars, which can simulate the actual pop-up motion of the trunk lid by considering kinematic constraints of the motion and friction forces in joints. We could also determine the most important factor that governs the pop-up height by sensitivity analysis of all parts. The developed system can be used for the analysis of other trunk lid systems to control the tolerance of parts.

분해모델과 구멍 메움 알고리즘을 이용한 냉장고 내부 용적의 자동 계산

박래성(Raesung Park),Jianhui Fu,정융호(Yoongho Jung),박민근(Mingeun Park) (사)한국CDE학회 2017 한국CDE학회 논문집 Vol.22 No.1

Internal capacity of a refrigerator is an important indicator for design and purchasing criteria. The components facing the internal space may have holes or gaps between parts. In traditional way, design engineers manually remodeled the parts to fill the holes and the gaps for enclosed boundary of the internal space. Then they calculated internal volume by subtracting the assembly of parts from its enclosing volume. However, filling holes and gaps is not an automated process requiring a plenty of labor and time. In this research, we have developed a voxel-based method to estimate the internal volume of a refrigerator automatically. It starts transforming all components facing the interior space into voxels and fills all holes and gaps automatically by the developed hole-filling algorithm to form a completely closed boundary of the assembly. Then, it identifies the boundary voxels that are facing to the internal voxels with any part of the component. After getting the intersection points between the boundary voxels and the surfaces of components, it generates the boundary surface of triangular facets with the intersection points. Finally, it estimates the internal volume by adding volume of each tetrahedron composed of a triangle of boundary surface and an arbitrary point.