• 한국정밀공학회지
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• 제24권7호
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• pp.60-68
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• 2007

This paper presents an efficient 5-axis roughing method for centrifugal impeller. The efficient roughing is minimization of cutting time through minimizing tool tilting and rotating motions. To minimized cutting time, machining area is divided into sub-cutting regions using control points on hub curves and shroud curves of blade used to design and analyze centrifugal impeller. For sub-cutting regions, diameters of cutting tools are determined as big as possible. Then, tool paths are generated with the tilting axis and rotating axis of 5-axis machine limited and fixed, which can give more efficient machining speed and machining stability than the conventional methods. Experimental results show that the proposed method is more efficient than the conventional methods to mill with the only one cutting tool without dividing area and the previous methods to mill with simultaneous 5-axis processing with dividing area.

• 대한기계학회논문집A
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• 제27권11호
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• pp.1917-1924
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• 2003

This paper proposes a roughing path generation method fer machining impeller with 5-axis machining center. Traditional researches are focus on finishing for machining impeller. To achieve efficient machining, roughing method must be studied. The proposed method consists two steps : One is to select optimal tool size and tool attitude by dividing cutting area into two regions to reduce cutting time. The regions are automatically divided by character point on the geometry of impeller blade. After dividing, the tool of the optimal size is selected for each divided region. The other is avoidance of tool interference. Tool interference in cutting areas is avoided by checking the distance between tool axis vector and ruling line on blade surface or approximated plan between ruling line. Using this method, the cutting time is reduced efficiently.

• 대한기계학회논문집B
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• 제23권10호
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• pp.1310-1319
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• 1999

High-pressure swirl injectors have usually been employed in Gasoline direct injection engines due to their spray characteristics and the feasibility of their control. Thus the microscopic characteristics of high-pressure swirl spray were investigated by PDA. The correlation between axial and radial velocities and the correlation between droplet size and axial velocity were examined with different axial and radial positions. Two dimensional droplet velocity and its number distribution with size-classified droplets were illustrated. The mean droplet velocity and its SMD were also analyzed at the center of spray, the position having maximum mean axial velocity, and the spray periphery using time dividing method. Finally, the structure of high-pressure swirl spray was presented with the size distribution and velocity profile of droplets.

• 한국분무공학회지
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• 제7권1호
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• pp.14-20
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• 2002

It is well known that the flow and spray characteristics is critical factor on the performance and emission of a direct injection diesel engine. So this study aims to investigate the interaction of flow and spray characteristics. At first, in cylinder flow distributions in swirl adaptor for 4-valve cylinder head of DI Diesel engine were investigated under steady conditions for different SCV angles mounted on the cylinder head with steady rig test and 2-D LDV. And the in-cylinder flow was quantified in terms of mean flow coefficient and swirl ratio/tumble ratio. It was found that the swirl ratio is controlled between 2.3 and 3.8. Then spray characteristics of the intermittent injection were investigated. PDA system was utilized for measurement of a droplet size and velocity. The analyses of the PDA results are carried out with Time Dividing Method. It was found that there is a correlation between the swirl flow and SMD. The droplet size and the velocity were nearly constant value with each SCV angle. And the swirl ratio is higher, SMD smaller. The swirl ratio was helpful factor to the atomization of droplet.

• 한국CDE학회논문집
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• 제5권4호
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• pp.327-335
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• 2000

The spent fuel rod extracting machine is automatically operated in high radioactive environment, so high reliability of operation is required. In this paper, to enhance the reliability of this machine by providing a close monitoring capability. a real time graphic simulation method is suggested. This method utilizes conventional IGRIP (Interactive Graphics Robot Instruction Program) 3D graphic simulation tool to visualize and simulate the 3D graphic model of this machine. Also, the dedicated protocol is defined for transmission of the operational data of the machine. The real time graphic simulation is realized by developing the socket module between a graphic workstation and a machine control computer through the TCP/IP network and by dividing the 3D graphic simulation GSL(Graphic Simulation Language) program as a small sized sub routine. The suggested method is implemented while automatically operating the rod extracting machine. The result of implementation shows that the real time 3D graphic simulation is well synchronized with the actual machine according to the operational data.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 학술대회 논문집 정보 및 제어부문
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• pp.306-308
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• 2005

The vehicle detection method using pulse radar has the advantage of maintenance in comparison with loop detection method. We have the information about the vehicle being and position by dividing the signals into sectors in accordance with SSC method, and by applying the discriminant function based on stochastical data. We also reduce the signal processing time.

• 대한전자공학회논문지
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• 제24권1호
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• pp.20-27
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• 1987

The hierarchical approach method is proposed to sperate each different time scale sub-systems from linear time invariant multi-parameter singular perturbation systems. By means of this proposal, the original multi-parameter singular perturbation systems is completely separated into independent subsystems with each different time scale. It is also investigated that the controllability of the system is invariant. And this paper applies singular perturbation methods to the minimum control effort problem for linear time invariant systems with constrained controls. Also near-optimum control theory, which is based on dividing the total time interval with the time scales respectively, is proposed. As a result, the time scale separation method is show to be particularly useful in a near optimum design which can be otained through a decentralized control structure.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.705-711
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• 2000

This paper presents a fast 3D mesh generation method using a surface based method with a stitching algorithm. This method uses the surface based method since the volume based method that uses 3D Delaunay triangulation can hardly deal with a large scale of scanned points. To reduce the processing time, this method also uses a stitching algorithm: after dividing the whole point data into several sections and performing mesh generation on individual sections, the meshes from several sections are stitched into one mesh. Stitching method prevents the surface based method from increasing the processing time exponentially as the number of the points increases. This method works well with different types of scanned points: a scattered type points from a conventional 3D scanner and a cross-sectional type from CT or MRI.

• 제어로봇시스템학회논문지
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• 제15권5호
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• pp.505-510
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• 2009

In recent years the space where a robot works has been expanding to the human space unlike traditional industrial robots that work only at fixed positions apart from humans. A human in the recent situation may be the owner of a robot or the target in a robotic application. This paper deals with the latter case; when a robot vision system is employed to monitor humans for a surveillance application, each person in a scene needs to be identified. Humans, however, often move together, and occlusions between them occur frequently. Although this problem has not been seriously tackled in relevant literature, it brings difficulty into later image analysis steps such as tracking and scene understanding. In this paper, a probabilistic neural network is employed to learn the patterns of the best dividing position along the top pixels of an image region of partly occlude people. As this method uses only shape information from an image, it is simple and can be implemented in real time.

• 정보처리학회논문지D
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• 제8D권6호
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• pp.813-822
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• 2001

본 논문에서는 시간지원 데이터를 과거 세그먼트, 현재 세그먼트, 그리고 미래 세그먼트로 분리한 저장 구조를 기반으로 하는 네 가지 데이터 이동 방법을 제안하였다. 제안한 데이터 이동 방법은 시간단위에 의한 이동 방법, LST-GET(Least valid Start Time-Greatest valid End Time)에 의한 이동 방법, AST-AET(Average valid Start Time-Average valid End Time)에 의한 이동 방법, 그리고 Min-Overlap에 의한 이동 방법이 있다. 각각의 이동 방법에서는 세그먼트의 경계값, 각 세그먼트에 저장되는 개체 버전 등을 정의하였다. 제안한 이동 방법에 대해서 사용자 질의에 대한 평균 응답 시간을 측정하였다. 실험결과, LLT(Long Lived Tuples)가 없는 경우에는 LST-GET에 의한 이동 방법, 그리고 AST-AET에 의한 이동 방법이 시간단위에 의한 이동 방법보다 성능이 우수하였다. LLT가 있는 경우에는 LST-GET에 의한 이동 방법의 성능이 저하되었다. AST-AET에 의한 이동 방법은 시간단위에 의한 이동 방법과 LST-GET에 의한 이동 방법보다 질의에 대한 성능이 우수하였다. Min-Overlap에 의한 이동 방법은 질의에 대한 평균 응답 시간에서 AST-AET에 의한 이동 방법과 비슷한 결과를 보였고, 공간 이용율 측면에서는 AST-AET에 의한 이동 방법보다 효율적이었다.