• 한국생산제조학회지
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• 제22권5호
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• pp.852-858
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• 2013

In numerical control (NC) machining, a machining error in equipment generally occurs for a variety of reasons. If there is a change in direction in the NC code, the characteristics of the automatic acceleration or deceleration function cause an overlap of each axis of the acceleration and deceleration zones, which in turn causes a shift in the actual processing path. Many studies have been conducted for error calibration of the edge as caused by automatic acceleration or deceleration in NC machining. This paper describes a geometric interpretation of the shape and processing characteristics of the operating NC device. The paper then describes a way to determine a feedrate that achieves the desired tolerance by using linear and parabolic profiles. Experiments were conducted by the validate equations using a three-axis NC machine. The results show that the machining errors were smaller than the machine resolution. The results also clearly demonstrate that the NC machine with the developed system can successfully predict machining errors induced with a change in direction.

• 한국측량학회지
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• 제19권3호
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• pp.283-290
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• 2001

저가의 CCTV유형 CCD카메라를 기반으로 하는 수치 근거리사진측량 시스템의 산업정밀측정의 수행능력을 평가하기 위하여 CCD카메라, 프레임그래버, 수치영상 측정 및 자체검정 광속조정 기법을 통합한 수치근거리 사진측량시스템이 구축되었다. 이 시스템의 적용실험을 위하여 정육면체 형상의 인공어초를 대상물로하여 다중지점 수렴 네트워크상에서 수치영상을 획득하였다. 자체검정 광속조정기법에 의해 CCD 카메라의 기하학적 검정과 동시에 대상물 전면에 대한 사진삼각측량을 수행하였다. 또한 이미 높은 정확도 잠재성이 입증된 고해상도 스틸비디오 카메라(Kodak DCS)를 유사한 네트워크 조건에서 이용하여 처리함으로써 서로 다른 유형의 카메라를 기반으로 하는 두 시스템의 사진삼각측량 결과의 정확도를 비교하였다.

• Smart Structures and Systems
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• 제25권5호
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• pp.531-541
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• 2020

This paper demonstrates the possibility of evaluating the safety of a building right after an earthquake using consumer-grade surveillance cameras installed in the building. Two cameras are used in each story to extract the time history of interstory drift during the earthquake based on camera calibration, stereo triangulation, and image template matching techniques. The interstory drift of several markers on the rigid floor are used to estimate the motion of the geometric center using the least square approach, then the horizontal interstory drift of any location on the floor can be estimated. A shaking table collapse test of a steel building was conducted to verify the proposed approach. The results indicate that the accuracy of the interstory drift measured by the cameras is high enough to estimate the damage state of the building based on the fragility curve of the interstory drift ratio. On the other hand, the interstory drift measured by an accelerometer tends to underestimate the damage state when residual interstory drift occurs because the low frequency content of the displacement signal is eliminated when high-pass filtering is employed for baseline correction.

• Architectural research
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• 제13권3호
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• pp.19-29
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• 2011

Visibility of a space have been defined in several different ways: such as the axial line covering a convex space, a convex space defining the fattest shape in a space and an Isovist field formed by a field of vision at a given vantage point. Isovist fields are referred to as a descriptive medium to describe a movement by reviewing and analyzing geometric properties in them. Many descriptive methods for analysis of three-dimensional isovist are applied to analyzing the morphological properties in a 3D space more realistically. Although these models are regarded as a more advanced method for describing spatial properties, they have pros and cons such as complex mathematical calculations and somewhat arbitrary calibration in addition to huge consumption of memory space. These difficulties lead to the development of a three-dimensional visual accessibility model that explores the implication of building shape on the calculation of isovist fields drawn on a 2D plane. We propose a conceptual framework of how to measure the isovist field not as a 3D volume but as a combination of 2D plane on the ground with the 3D building shape of it's facade.

• 제어로봇시스템학회논문지
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• 제20권1호
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• pp.78-86
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• 2014

This paper proposes a method of tracking an object for a person-following mobile robot by combining a monocular camera and a laser scanner, where each sensor can supplement the weaknesses of the other sensor. For human-robot interaction, a mobile robot needs to maintain a distance between a moving person and itself. Maintaining distance consists of two parts: object tracking and person-following. Object tracking consists of particle filtering and online learning using shape features which are extracted from an image. A monocular camera easily fails to track a person due to a narrow field-of-view and influence of illumination changes, and has therefore been used together with a laser scanner. After constructing the geometric relation between the differently oriented sensors, the proposed method demonstrates its robustness in tracking and following a person with a success rate of 94.7% in indoor environments with varying lighting conditions and even when a moving object is located between the robot and the person.

• 대한기계학회논문집A
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• 제21권12호
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• pp.2146-2155
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• 1997

This paper presents the Wire Parallel Mechanism for robot pose measurement which can be used to robot calibration. It is constructed with six parallel links using wire. The position and orientation of the end effector of a robot are calculated from the wire length that measured by the encoder. The unique solution is obtained from a Newton-Raphson method and geometric configuration of the mechanism, also the method to estimate a measuring space is presented. Through the simulations, it is verified that the proposed mechanism can measure a robot pose, and has a large measuring space. In conclusion, it can be used effectively in a robot pose measurement with little cost and effort.

• 대한기계학회논문집B
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• 제21권12호
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• pp.1608-1614
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• 1997

The fluidic flow meter detects the gas flow rate based on the principle of fluidic oscillation instead of the conventional displacement method. It has many merits: wide rangeability, no moving mechanical parts and calibration insensitive to physical properties of fluids. The width of nozzle, size of oscillation chamber, size of target, width of outlet are tested to obtain the effects of jet oscillation on the fluidic flow meter. As the width of nozzle is too wide compared with the size of target, jet oscillation is unstable. The oscillation frequency decreases as the distance between the nozzle and target increases and also as the distance between target and outlet contraction increases. Two different vortexes exist in the front and the rear regions of the target, and they affect the oscillation frequency. The outlet contraction is very important, because the feedback flow is generated by the blocking of the flow. As the width of outlet increases, the jet oscillation frequency decreases. The linearity of this tested flow meter is quite good.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2006년도 가을 학술발표논문집 Vol.33 No.2 (B)
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• pp.116-120
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• 2006

최근 유비쿼터스 환경에서 프로젝터를 기반으로 사용자가 원하는 위치에 영상을 제공하는 유비쿼터스 디스플레이 연구가 진행 중이다. 프로젝터는 투사방향에 따라 영상의 왜곡이 발생함으로써, 프로젝터 기반의 유비쿼터스 디스플레이는 왜곡된 영상을 보정하는 것이 매우 중요하다. 영상 보정을 위한 기존 연구는 특정마커를 설치하거나 특정 패턴의 영상을 투사하는 등의 선행 작업을 통해 기하보정을 수행한다. 이 방법들은 투사방향이 변화될 때마다 선행 작업을 요구하므로 실시간 기하보정을 수행할 수 없다는 단점이 있다. 본 논문은 특정마커나 카메라와 같은 별도의 장치 없이도 투사되는 방향에 따라 영상의 왜곡 정도를 예측하여 실시간으로 보정된 영상을 제공하는 기하보정 시스템을 제안한다. 제안된 시스템은 특정 보정장치를 사용하지 않고 보정함으로써, 약 27fps의 빠른 처리속도를 가진다. 또한 상용 리모컨을 사용하여 프로젝터의 투사방향을 쉽게 제어하는 편리한 인터페이스를 제공한다.

• 한국지능시스템학회논문지
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• 제21권4호
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• pp.442-448
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• 2011

이동 로봇의 위치인식 기술을 위하여 SLAM(Simultaneous Localization and Mapping)에 관한 많은 연구가 진행되고 있다. 본 논문에서는 시야각이 넓은 어안렌즈를 장착한 단일 카메라를 사용하여 천장의 특징점을 이용한 자기위치 인식에 관한 방안을 제시한다. 여기서는 어안렌즈 기반의 비전 시스템이 가지는 왜곡 영상의 보정, SIFT(Scale Invariant Feature Transform) 기반의 강인한 특징점을 추출하여 이전 영상과 이동한 영상과의 정합을 통해 최적화된 영역 함수를 도출하는 과정, 그리고 기하학적 적합모델 설계 등을 제시한다. 제안한 방법을 실험실 환경 및 복도 환경에 적용하여 그 유용성을 확인한다.

• 한국생산제조학회지
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• 제25권6호
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• pp.410-420
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• 2016

The geometric dimension and shape of microchannels that are formed during surface texturing are widely studied for applications in flow control, and drag and friction reduction. In this research, a new method for controlling the deformation of U channels during micro-rolling-based surface texturing was developed. Since the width of the U channels is almost constant, controlling the depth is essential. A calibration procedure of initial rolling gap, and proportional-integral PI controllers and a linear interpolation have been applied simultaneously to control the depth. The PI controllers drive the position of the pre-U grooved roll as well as the rolling gap. The relationship between the channel depth and rolling gap is linearized to create a feedback signal in the depth control system. The depth of micro channels is studied on A2021 aluminum lamina surfaces. Overall, the experimental results demonstrated the feasibility of the method for controlling the depth of microchannels.