• 로봇학회논문지
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• 제14권3호
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• pp.186-190
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• 2019

When problems occurred in the unstable and/or extreme terrain environment, formal field-driving robots were unable to provide any other options such as the transformation of the wheel and body structure, and so on. For such reason, this paper proposed a novel type of integrated wheel mechanism that can be operated as a conventional driving wheel mode and hybrid wheel-leg mode in order to be negotiated in an unstable terrain environment. The mechanical effect of the proposed variable wheel mechanism was analyzed considering the geometric constraint and power requirement of the actuator for the transformation. In addition, we designed and manufactured the prototype of field-driving robot, which reliably control the variable wheel shape. Finally, the effectiveness of the variable wheel mechanism was verified by preliminary experimental approach.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권11호
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• pp.4463-4482
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• 2020

Mesh model generated from 3D reconstruction usually comes with lots of noise, which challenges the performance and robustness of mesh simplification approaches. To overcome this problem, we present a novel method for mesh simplification which could preserve structure and improve the accuracy. Our algorithm considers both the planar structures and linear features. In the preprocessing step, it automatically detects a set of planar structures through an iterative diffusion approach based on Region Seed Growing algorithm; then robust linear features of the mesh model are extracted by exploiting image information and planar structures jointly; finally we simplify the mesh model with plane constraint QEM and linear feature preserving strategies. The proposed method can overcome the known problem that current simplification methods usually degrade the structural characteristics, especially when the decimation is extreme. Our experimental results demonstrate that the proposed method, compared to other simplification algorithms, can effectively improve the quality of mesh and yield an increased robustness on noisy input mesh.

• International Journal of Control, Automation, and Systems
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• 제4권2호
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• pp.204-216
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• 2006

Latest advances in hardware technology and state of the art of mobile robot and artificial intelligence research can be employed to develop autonomous and distributed monitoring systems. And mobile service robot requires the perception of its present position to coexist with humans and support humans effectively in populated environments. To realize these abilities, robot needs to keep track of relevant changes in the environment. This paper proposes a localization of mobile robot using the images by distributed intelligent networked devices (DINDs) in intelligent space (ISpace) is used in order to achieve these goals. This scheme combines data from the observed position using dead-reckoning sensors and the estimated position using images of moving object, such as those of a walking human, used to determine the moving location of a mobile robot. The moving object is assumed to be a point-object and projected onto an image plane to form a geometrical constraint equation that provides position data of the object based on the kinematics of the intelligent space. Using the a priori known path of a moving object and a perspective camera model, the geometric constraint equations that represent the relation between image frame coordinates of a moving object and the estimated position of the robot are derived. The proposed method utilizes the error between the observed and estimated image coordinates to localize the mobile robot, and the Kalman filtering scheme is used to estimate the location of moving robot. The proposed approach is applied for a mobile robot in ISpace to show the reduction of uncertainty in the determining of the location of the mobile robot. Its performance is verified by computer simulation and experiment.

• 문화기술의 융합
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• 제6권4호
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• pp.767-776
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• 2020

GcGAN은 기하학적 일관성을 유지하며 영상 간 스타일을 변환하는 딥러닝 모델이다. 그러나 GcGAN은 회전이나 반전(flip) 등의 한정적인 기하 변환으로 영상의 형태를 보존하기 때문에 영상의 세밀한 형태 정보를 제대로 유지하지 못하는 단점을 가지고 있다. 그래서 본 연구에서는 이런 단점을 개선한 새로운 영상 간 변환 기법인 MSGcGAN(Multi-Scale GcGAN)을 제안한다. MSGcGAN은 GcGAN을 확장한 모델로서, 다중 스케일의 영상을 동시에 학습하여 스케일 불변 특징을 추출함으로써, 영상의 의미적 왜곡을 줄이고 세밀한 정보를 유지하는 방향으로 영상 간 스타일 변환을 수행한다. 실험 결과에 의하면 MSGcGAN은 GcGAN보다 정량적 정성적 측면에서 모두 우수하였고, 영상의 전체적인 형태 정보를 잘 유지하면서 스타일을 자연스럽게 변환함을 확인할 수 있었다.

• 한국구조물진단유지관리공학회 논문집
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• 제10권5호
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• pp.203-211
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• 2006

본 연구에서는 고등해석과 유전자 알고리즘을 이용한 강뼈대 구조물의 직접설계시스템의 최적화를 수행하였다. 본 연구에서 사용한 고등해석은 기하학적 비선형과 재료적 비선형을 동시에 고려한다. 직접설계 시스템의 최적화를 위해 유전자 알고리즘을 사용하였다. 목적함수로 구조물의 중량을 사용하였으며, 제약조건식은 구조시스템의 하중-저항능력, 처짐, 층간 수평변위 및 연성요구 조건을 고려하였다. 제안된 방법에 의해 나타난 결과를 다른 방법에 의한 것들과 비교해서 그 효율성을 증명하였다.

• 전자공학회논문지
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• 제52권5호
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• pp.127-135
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• 2015

본 논문에서는 사용자의 입력을 포함한 반자동 카메라 교정 방법을 제안한다. 제안된 방법은 사용자가 정의한 기준선을 소실점 추정을 위한 정보로 사용하는 동시에, 추정 과정에서 발생하는 아웃라이어 제거를 위한 추가 제약 조건으로 사용한다. 제안된 카메라 교정 방법은 대수적, 기하학적 방법을 모두 사용하여 기존 방법으로는 불가능한 조건에서 교정이 가능하도록 성능을 확장하였다. 교정 실험 결과를 통해 제안하는 방법이 기존 자동 교정보다 교정 정확도가 높은 것을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권6호
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• pp.2689-2708
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• 2016

Multi-camera systems which integrate two or more low-cost digital cameras are adopted to reach higher ground coverage and improve the base-height ratio in low altitude remote sensing. To guarantee accurate multi-camera integration, the geometric relationship among cameras must be determined through platform calibration techniques. This paper proposed a combined two-step platform calibration method. In the first step, the static platform calibration was conducted based on the stable relative orientation constraint and convergent conditions among cameras in static environments. In the second step, a dynamic platform self-calibration approach was proposed based on not only tie points but also straight lines in order to correct the small change of the relative relationship among cameras during dynamic flight. Experiments based on the proposed two-step platform calibration method were carried out with terrestrial and aerial images from a multi-camera system combined with four consumer-grade digital cameras onboard an unmanned aerial vehicle. The experimental results have shown that the proposed platform calibration approach is able to compensate the varied relative relationship during flight, acquiring the mosaicing accuracy of virtual images smaller than 0.5pixel. The proposed approach can be extended for calibrating other low-cost multi-camera system without rigorously mechanical structure.

• 동력기계공학회지
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• 제11권2호
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• pp.51-57
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• 2007

As a shot sleeve in die casting plays a critical role in delivering molten metal to a die cavity, any disruption to its function in the injection stage results in deterioration of the quality of final castings. To guarantee a smooth operation of a shot sleeve, its structural stability should be maintained. Despite the simple geometry, design of shot sleeve is based on individual engineer's experience and no agreement on the design is present. In this study, we newly propose a systematic methodology to determine a minimum wall thickness of a shot sleeve to prevent yielding or plastic deformation. Analytical calculations incorporating numerical analysis produce a rational design rule for minimum thickness of a shot sleeve subject to metal intensification pressure and geometric die constraint. To validate the proposed design guideline, authors present real data on a collection of actual shot sleeves. Upon checking their conformity to the new design rule, we discovered a strong correlation between the design of wall thickness and premature failures.

• Structural Engineering and Mechanics
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• 제49권1호
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• pp.65-80
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• 2014

This paper reports on the development of a minimum cost design model and its application for obtaining economic designs for reinforced High Strength Concrete (HSC) T-sections in bending under ultimate limit state conditions. Cost objective functions, behavior constraint including material nonlinearities of steel and HSC, conditions on strain compatibility in steel and concrete and geometric design variable constraints are derived and implemented within the Conjugate Gradient optimization algorithm. Particular attention is paid to problem formulation, solution behavior and economic considerations. A typical example problem is considered to illustrate the applicability of the minimum cost design model and solution methodology. Results are confronted to design solutions derived from conventional design office methods to evaluate the performance of the cost model and its sensitivity to a wide range of unit cost ratios of construction materials and various classes of HSC described in Eurocode2. It is shown, among others that optimal solutions achieved using the present approach can lead to substantial savings in the amount of construction materials to be used. In addition, the proposed approach is practically simple, reliable and computationally effective compared to standard design procedures used in current engineering practice.

• 한국공간구조학회논문집
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• 제5권4호
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• pp.53-59
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• 2005

이 논문은 경계조건에 따른 판구조물의 최적두께분포 변화에 대한 연구결과를 기술하였다. 본 연구에서는 최소화하고자하는 변형에너지를 목적함수로 하고 구조물의 초기 부피 값을 제약조건으로 사용하였다. 판구조물의 두께분포를 표현하기 위하여 쿤이 개발한 조각 면을 이용하였다. 판의 변형에너지를 정확히 계산하기 위하여 퇴화 쉘 요소를 도입하였으며 반복계산을 통하여 최적의 두께분포를 검색하기 위하여 최적화검색기 DOT를 도입하였다. 마지막으로 경계조건에 따른 판의 최적두께 분포에 대한 정량적인 수치해석결과를 제공하기 위하여 정사각형 판을 최적화에 채용하고 그 결과를 자세히 기술하였다.