• 한국지능시스템학회논문지
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• 제21권3호
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• pp.323-328
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• 2011

실제 시스템 적용에 있어서, 수중비행체(Underwater Flight Vehicle : UFV)의 자율제어(autonomous control)를 위한 3-D 장애물회피(obstacle avoidance) 시스템은 다음과 같은 문제점들을 가지고 있다. 즉, 소나(sonar)는 지역적 탐색영역 내에서 장애물의 거리(range)/방위(bearing) 정보를 제공하며, 자율수중운동체(Autonomous Underwater Vehicle : AUV) 관점에서 에너지 소비 및 음향학적 소음이 적은 시스템을 필요로 하며, 최대 피치 및 심도와 같은 UFV 운용 제약조건을 가진다. 나아가, 구조와 파라메터의 관점에 있어서 용이한 설계 절차를 요구한다. 이 문제를 해결하기 위해서 진화 전략(Evolution Strategy : ES) 및 퍼지논리 제어기(Fuzzy Logic Controller : FLC)를 이용하는 지능형 3-D 장애물회피 알고리즘이 제안되었다. 제안된 알고리즘의 성능을 검증하기 위해 UFV의 3-D 장애물회피가 수행되었다. 시뮬레이션 결과는 제안된 알고리즘이 실제 시스템에 존재하는 문제점들을 효과적으로 해결하고 있음을 보여준다.

• 자동차안전학회지
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• 제14권2호
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• pp.39-44
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• 2022

This paper presents LiDAR static obstacle map based vehicle position correction algorithm for urban autonomous driving. Real Time Kinematic (RTK) GPS is commonly used in highway automated vehicle systems. For urban automated vehicle systems, RTK GPS have some trouble in shaded area. Therefore, this paper represents a method to estimate the position of the host vehicle using AVM camera, front camera, LiDAR and low-cost GPS based on Extended Kalman Filter (EKF). Static obstacle map (STOM) is constructed only with static object based on Bayesian rule. To run the algorithm, HD map and Static obstacle reference map (STORM) must be prepared in advance. STORM is constructed by accumulating and voxelizing the static obstacle map (STOM). The algorithm consists of three main process. The first process is to acquire sensor data from low-cost GPS, AVM camera, front camera, and LiDAR. Second, low-cost GPS data is used to define initial point. Third, AVM camera, front camera, LiDAR point cloud matching to HD map and STORM is conducted using Normal Distribution Transformation (NDT) method. Third, position of the host vehicle position is corrected based on the Extended Kalman Filter (EKF).The proposed algorithm is implemented in the Linux Robot Operating System (ROS) environment and showed better performance than only lane-detection algorithm. It is expected to be more robust and accurate than raw lidar point cloud matching algorithm in autonomous driving.

• 대한교통학회지
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• 제20권5호
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• pp.55-66
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• 2002

비행장 주위 상공에는 저고도로 이착륙하는 항공기의 안전운항을 위하여 장애물제한표면을 설정하여 이 표면 위로 건축물이 돌출하는 것을 제한하고 있으며, 장애물 표시를 의무화하고 있다. 그러나 이 구역 내에 제거가 불가능한 영구적 장애물이 있을 때는 그 장애물의 존재를 인정하고, 그 장애물 정상으로부터 일정한 간격의 안전고도를 유지하여 비행안전을 도모하면서도 장애물제한표면은 동시에 적용한다는 문제점이 있다. 따라서 영구적 장애물이 있는 경우에는 영구적 장애물보다 낮은 장애물은 장애물제한표면을 돌출했을지라도 비행안전에는 영향이 적다 라는 근거아래 차폐이론을 국제민간항공기구에서 권고 사항으로 채택하였으며, 미국을 비롯한 5개 국가에서 기존 장애물의 영향이 미치는 음영면 이하의 장애물에 대해서는 차폐이론을 적용하여 건축규제를 완화하거나 장애물표시등의 의무를 면제할 수 있도록 하고 있다. 본 연구에서는 차폐이론의 적용이 항공기의 운항 안전에 영향을 줄 수 있다는 가정 아래 문헌과 사례 연구를 통하여 그 영향을 검토하였다. 그 결과 장애물제한구역과 계기접근구역이 중복되는 구역에서는 신규 장애물의 설치가 비행안전과 운항에 영향을 줄 수도 있었다. 이런 영향을 제거하기 위해서는 각각의 비행장의 장애물제한표면 내에 해당 비행장에서 이용하고 있는 계기접근절차의 최종접근구역과 실패접근구역의 경계선을 도시하여 이 구역내에서는 차폐기준을 적용을 제한하는 것이 바람직하다.

• 한국운동역학회지
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• 제21권4호
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• pp.459-466
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• 2011

The purpose of this study was to analyze of obstacle gait using spatio-temporal and foot pressure variables in children with autism. Fifteen children with autism and fifteen age-matched controls participated in the study. Spatio-temporal and foot pressure variables was investigated using GAITRite pressure sensor system. Each footprint was divided into 12 equal trapezoids and after that the hindfoot, midfoot and forefoot analysis was developed. Independent t-test was applied to compare the gait variables between the groups. The results showed that the autism group were significantly decreased in velocity, cadence, cycle and swing time compared to the control group. The autism group were significantly increased in step width and toe out angle compared to the control group. The autism group were significantly increased at midfoot and forefoot of lateral part of footprint and forefoot of medial part of footprint in the peak time compared to the control group. The autism group were significantly increased at midfoot and hindfoot in $P^*t$, at midfoot in active area, and at hindfoot in peak pressure compared to the control group. In conclusion, the children with autism showed abnormal obstacle gait characteristics due to muscle hypotonia, muscle rigidity, akinesia, bradykinesia and postural control impairments.

• 한국항행학회논문지
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• 제10권2호
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• pp.145-151
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• 2006

본 논문에서는 동적인 환경에서 돌발 장애물을 회피하는 방법으로 Nearness Diagram, Limit-Cycle 및 벡터장법을 혼합한 새로운 항법을 제안한다. Limit-Cycle 항법은 정면장애물을 회피 하는데 사용되고, 벡터장법은 측면장애물을 회피 하는데 이용된다. 그리고 Nearness Diagram 항법은 로봇의 근접지역장애물을 회피하는데 사용된다. 제안된 항법은 시뮬레이션을 통해 그 성능을 증명하였다.

• 제어로봇시스템학회논문지
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• 제20권10호
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• pp.1067-1072
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• 2014

The ability to overcome obstacles is necessary for field robots for various applications including the ability to climb stairs. While much research has been performed focusing on overcoming obstacles, the resulting robots do not have sufficient ability to overcome obstacles such as stairs. In this research, the purpose is to overcome relatively large obstacles by flipping locomotion through the modification of the stair climbing robotic platform of the previous research. We propose two scenarios to overcome large obstacles: a rear wheel driving system and an elevation system using a ball screw. The research is performed based on static analyses on obstacle-climbing. As the simulation results indicate, we determined the optimal posture of the robot for climbing obstacles for rear wheel driving. Also, an elevation system is analyzed for obstacle climbing. Between the two scenarios an elevation system is determined to reduce the operating torque of the actuator, and the prototype was recently assembled. The climbing ability of the robotic platform is verified. We expect the application area for this robotic platform will be in accident areas of nuclear power plants.

• 해양환경안전학회지
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• 제14권4호
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• pp.333-338
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• 2008

해안 지역은 해수의 운동에너지의 대부분은 해안에서 소산되며 이 과정에서 해안의 토사 등이 유실된다. 수면에 돌출된 방파제에 비해 수중구조물은 해수의 유통을 가능하게 하고 해안선을 따라 해수순환을 가능케 한다. 이 연구에서는 해안 침식을 방지 기능을 갖는 수중구조물을 하부틈새를 갖는 수중장애물로 형상화 하고 후방의 흐름특성을 규명하였다. 실험은 Re =$1.2{\times}10^4$ 조건에서 2프레임 입자영상유속계를 이용하여 속도장을 계측하여 고찰하였다. 측정된 시간평균 속도분포를 분석한 결과 유선의 곡률 효과가 현저히 나타났으며 전단층 주위 유체의 유입 등의 영향으로 박리 전단층 내에서 커다란 와구조가 연속적으로 발생하였다. 또한 하부틈새의 크기가 증가할수록 재순환 영역의 중심이 후류로 이동하고 재순환영역의 강도도 약해지는 결과를 보였다.

• 한국항공운항학회지
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• 제30권3호
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• pp.28-37
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• 2022

Obstacle Limitation Surface (OLS) is conceptual surface establishing the airspace around aerodromes to be maintained from obstacles to ensure safe aircraft operations. Despite advances in the technologies for aircraft, navigation systems and the development of new flight procedures, the criteria defining OLS have not been amended since its initial establishment, resulting in the overestimation of areas for height restriction. As there were requests to examine OLS at the 12th Air Navigation Conference and the 38th ICAO Assembly, the research on the OLS revision began in earnest and ICAO has proposed Obstacle Free Surface (OFS) and Obstacle Evaluation Surface (OES) as an alternative of the existing OLS. OFS is surfaces where obstacles shall not be permitted, and OES is ones where obstacles be evaluated with an aeronautical study and could be permitted under some conditions. The purpose of this study is to preemptively assess the efficiency and safety of OFS and OES by applying them to the second runway (15L/33R) of Incheon International Airport. The results show that OFS and OES are capable of serving the instrument flight procedure safely with a smaller obstacle clearance area compared to the existing OLS.

• 한국조경학회지
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• 제26권1호
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• pp.96-112
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• 1998

This study aims to evaluate the potential of pro-environmental application(PEP) in streams conceptualized ecological conservation and recreational use to be in harmony with. The main content of research are to clarify the PEP, to establish the evaluation model, and to evaluate 3 streams(Dongchon, Seokhyunchon, Okchon) in Sunchon city. Researchers introduced 12 evaluation items(water quality, water quantity, vegetation-water area, vegetation conservation, streamscape, neighborhood landscape, stream width, optimum area, nearby landuse, facility in stream, distance from user, obstacle to acces) by 5 scales to evaluate the characteristics of natural and artificial factors in stream area and nearby area. Also to decide the weight of items, researchers surveyed the opinion of 22 landscape architects experienced stream-plan through delphi method. Lastly the pro-environmental potential on streams were calculated by the ecological potential and recreational potential indices to be standardized and indicidual sections in streams were divided 5 grades on the basis of PEP. The result of this study are as follows; 1) The evaluation model of PEP was constructed by 4 steps, such as the decision of weight, the measurement of scale, the calculation of potential indices, the gradation of individual sections in streams. 2) The ecological potential were highly influenced by natural factor such as water quality, vegetation conservation, vegetation-water area, but on the other hand the recreational potential were influenced by optimum area, distance from user, water quantity, obstacle to access. 3) The factors such as vegetation conservation, optimum area, nearby landuse, distance from user were function as discernment factors to evaluate relatively ecological and recreational potential. and water quality, water quantity, vegetation -water area, neighborhood landscape were acted as important items to decide PEP.

• 한국안전학회지
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• 제27권6호
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• pp.70-77
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• 2012

Experimental investigations were performed to examine the characteristics of propagating flame fronts around multiple bars within a rectangular chamber. The explosion chamber is 400 mm in height, $700{\times}700mm^2$ in cross-section and has a large top-venting area, $A_v$, of $700{\times}210mm^2$. This results in a value of 0.44 for $A_v/V^{2/3}$ and a L/D value of 0.57. The multiple obstacles of length 700 mm with a blockage ratio of 30 % were placed within the chamber. Temporally resolved flame front images were recorded by a high speed video camera to investigate the interaction between the propagating flame and the obstacles. Results showed that the flame propagation speeds before the flame impinges onto the obstacle almost equal to the laminar burning velocity. As the propagating flame impinged on the obstacle, the central region of flame began to become concave, this resulted in the flame deceleration in the region. As the flame interacted with the modified flow filed generated behind the central obstacle, the probability density functions(PDFs) of the local flame displacement speed were extensively distributed toward higher speeds.