• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.202-210
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• 2019

The obstacles modeling is a fundamental and significant issue for path planning and automatic navigation of Unmanned Surface Vehicle (USV). In this study, we propose a novel obstacles modeling method based on high resolution satellite images. It involves two main steps: extraction of obstacle features and construction of convex hulls. To extract the obstacle features, a series of operations such as sea-land segmentation, obstacles details enhancement, and morphological transformations are applied. Furthermore, an efficient algorithm is proposed to mask the obstacles into convex hulls, which mainly includes the cluster analysis of obstacles area and the determination rules of edge points. Experimental results demonstrate that the models achieved by the proposed method and the manual have high similarity. As an application, the model is used to find the optimal path for USV. The study shows that the obstacles modeling method is feasible, and it can be applied to USV path planning.

• 초등상담연구
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• 제9권1호
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• pp.75-94
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• 2010

본 연구의 목적은 초등학교 4학년 학생들을 대상으로 수업행동의 개선을 위하여 수업행동을 수업 방해 행동과 수업 참여 행동으로 구분하고, 자기점검기법이 대상 아동들의 수업 방해 행동과 수업 참여행동에 어떠한 영향을 미치는지를 알아보고자 하는 데 있다. 이러한 연구목적을 달성하기 위해 설정한 연구문제는 첫째, 자기점검기법이 아동의 수업 방해 행동에 어떠한 영향을 미치는가. 둘째, 자기점검기법이 아동의 수업 참여 행동에 어떠한 영향을 미치는가를 밝히는 것이다. 연구 문제에 따른 연구 가설은 1. 자기점검기법은 아동의 수업방해행동을 감소시킬 것이다. 2. 자기점검 기법은 아동의 수업참여행동을 증가시킬 것이다로 세웠다. 연구 대상은 전라북도 J시에 소재하는 A초등학교 4학년 $\circledcirc$반 일반 학급 아동 12명으로 이는 기초선 기간의 행동측정 결과 수업 방해 행동 비율이 높은 8명과 수업 참여 행동 비율이 낮은 8명을 선정하였고, 양 쪽 그룹 모두에 속하는 아동이 4명이다. 이들의 사전 행동 관찰을 거쳐 개별적으로 수업 방해 행동 및 수업 참여 행동의 목표 행동을 설정하도록 하고, 기초선 1 기간 동안 각 행동의 빈도를 연구자가 두 명의 관찰자와 함께 측정하였다. 이후 중재 1 기간 동안 자기점검기법이 적용되었고, 아동 행동변화의 효과가 자기점검기법임을 밝히기 위하여 기초선 2 기간을 가졌다. 이후 중재 2 기간 동안 다시 자기점검기법이 실시되었으며, 10일 후 유지정도를 측정하기 위하여 사후 점검을 실시하였다. 개별 아동의 행동 발생 빈도를 변화 그래프를 이용하여 나타냈으며, 양적 결과의 제한점을 보완하기 위해 대상 아동들의 사후 소감문을 분석하였고, 연구자의 관찰내용을 제시하였다. 이 연구를 통해 얻어진 결과를 요약하면 첫째, 자기점검기법은 아동의 수업 방해 행동의 감소와 변화된 행동의 유지에 긍정적 효과를 미치는 것으로 나타났다. 둘째, 자기점검기법은 아동의 수업 참여 행동의 증가와 변화된 행동의 유지에 긍정적 효과를 미치는 것으로 나타났다.

• 로봇학회논문지
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• 제16권2호
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• pp.112-121
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• 2021

Unlike a typical small-sized robot navigating in a free space, an autonomous vehicle has to travel in a designated road which has lanes to follow and traffic rules to obey. High-Definition (HD) maps, which include road markings, traffic signs, and traffic lights with high location accuracy, can help an autonomous vehicle avoid the need to detect such challenging road surroundings. With space constraints and a pre-built HD map, a new type of path planning algorithm can be conceived as a substitute for conventional grid-based path planning algorithms, which require substantial planning time to cover large-scale free space. In this paper, we propose an obstacle-avoiding, cost-based planning algorithm in a continuous space that aims to pursue a globally-planned path with the help of HD map information. Experimentally, the proposed algorithm is shown to outperform other state-of-the-art path planning algorithms in terms of computation complexity in a typical urban road setting, thereby achieving real-time performance and safe avoidance of obstacles.

• 대한전기학회논문지:시스템및제어부문D
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• 제51권12호
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• pp.583-595
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• 2002

Homing operation can be defined as a series of actions which are necessary for a mobile robot to move from the current position with any arbitrary orientation to a desired position with a specified orientation, while avoiding possible obstacles. In this paper, a homing and obstacle avoidance algorithm for nonholonomic mobile robots is proposed. The proposed algorithm consists of a local goal generator, a discrete state controller, and local path tracking controller based on Aicardi's path following algorithm. In the discrete state controller, 4 states are defined according to the environmental conditions and 4 desired high-level command for the states are given as follows: avoid, wander, home and homing zones. The proposed local goal generator is designed to generate the desired local path by using weighted distance transforms which are newly made to satisfy the nonholonomic constraints of mobile robots. Here, subgoals are also found as vertices of the desired local path. To demonstrate result effectiveness and applicability of the proposed algorithm, computer simulations are illustrated and experimental results for a real mobile robot system are also provided.

• 한국정밀공학회지
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• 제21권8호
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• pp.73-82
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• 2004

In this paper, implementation of obstacle avoidance of a nonholonomic mobile robot in unstructured environment is introduced. To avoid obstacles, first, a reference collision-free path for the MR is generated off-line using HJB-based optimal path planning method. A controller is designed using integrator backstepping method for tracking the generated reference path. To implement the designed controller, a control system are needed and composed of camera system and PIC-based controller. The workspace is observed by a ceiling-mounted USB camera as part of an un-calibrated camera system. Thus the positional information of the MR is updated frequently and the MR can get the useful inputs for its tracking controller. The whole control system is realized by integrating a computer with PIC-based microprocessor using wireless communication: the image processing control module and path planning module serve as high level computer control while the device control serves as low level PIC microprocessor control. The simulation and experimental results show the effectiveness of the designed control system.

• 한국정밀공학회지
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• 제30권4호
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• pp.383-389
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• 2013

Demand for high-rising building has arisen. However, its maintenance is usually executed by labour. It could have a severe problem. We proposed a gondola robot to solve it. In this paper, we designed a height estimation sensor for this gondola. It is consist of pan-tilt unit, ARS sensor, and laser sensor. The pan-tilt unit keeps the laser sensor to indicate the gravity direction by referencing the ARS. The laser sensor's range is vertical distance from gondola to ground. However, if there is an obstacle under the gondola, the distance includes its height. To filter it out, we apply a Kalman filter for the height estimation. If the estimated height is changed extremely, the filter decides that there is an obstacle. Then, it remembers the height of obstacle. Other extreme changes of height estimations are reflected. The experimental results using the proposed sensor system show detail flow of the height estimation.

• 한국환경과학회지
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• 제18권10호
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• pp.1115-1121
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• 2009

The purpose of this study is to estimate the impact of rainfall measurement according to the installation conditions of rain gauges: windbreak, grass mat, installation elevation or obstacle. Rain gauges were installed by the standards of Korea Meteorological Administration(KMA), and the rainfall measurement was conducted daily unit during two years(2007~2008). In conclusion, observed error of rain gauge did not affect whether windbreak was installed or not. If there is the obstacle around rain gauge, average error rate was increased about 3.3%: (2007year-2.49%, 2008year-4.10%). If rain gauge is located in a high place, average error rate was increased about 4.89%. Additionally, the observed error of rain gauge according to the wind speed has a positive correlation with obstacle and installation elevation and has a negative correlation with windbreak and has no affection with grass mat.

• 제어로봇시스템학회논문지
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• 제18권3호
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• pp.193-200
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• 2012

Mobility is one of the most important issues for search and rescue robots. To increase mobility for small size robot we have focused on the mechanism and algorithm inspired from centipede. In spite of small size, using many legs and flexible long body, centipede can overcome high obstacles and move in rough terrains stably. This research focused on those points and imitated their legs and body that are good for obstacle negotiation. Based on similarity of a centipede's legs and tracks, serially connected tracks are used for climbing obstacles higher than the robot's height. And a centipede perceives environments using antennae on its head instead of eyes. Inspired from that, 3 IR sensors are attached on the front, top and bottom of the first module to imitate the antenna. Using the information gotten from the sensors, the robot decides next behavior automatically. In experiments, the robot can climb up to 45 cm height vertical wall and it is 600 % of the robot's height and 58 % of the robot's length.

• 가정과삶의질연구
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• 제20권6호
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• pp.129-140
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• 2002

The purpose of this study was to collect baseline data for women＇s needs for social education, in order to eventually contribute to improving the quality of women's social education. In the needs survey, information on the motive to participate in social education programs, obstacles to participation, and program preferences was collected. The data were then analyzed by women＇s socio-demographic characteristics. Survey participants were married women between the ages of twenty to fifty, who were sampled from Seoul, six metropolitan areas, and nine provinces. For the final analysis, 1,026 survey forms were used. The motive for participating in women＇s social education programs was examined by each category. Overall, the participants showed the highest level in educational achievement motif. The motivations for lifestyle change, self-realization, and social accomplishment were also high and at a similar level. As for obstacles to participation, social obstacle received the highest rate, followed by family obstacle and personal reasons. As for the type of social education programs, home management programs were the most preferred, followed by psychological education, family education, leisure activity programs, physical education, and social education programs.

• 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.