• Nuclear Engineering and Technology
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• 제56권4호
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• pp.1153-1164
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• 2024

In recent years, unmanned ground vehicles (UGVs) have been used to search for lost or stolen radioactive sources to avoid radiation exposure for operators. To achieve autonomous localization of radioactive sources, the UGVs must have the ability to automatically determine the next radiation measurement location instead of following a predefined path. Also, the radiation field of radioactive sources has to be reconstructed or inverted utilizing discrete measurements to obtain the radiation intensity distribution in the area of interest. In this study, we propose an effective source localization framework and method, in which UGVs are able to autonomously explore in the radiation area to determine the location of radioactive sources through an iterative process: path planning, radiation field reconstruction and estimation of source location. In the search process, the next radiation measurement point of the UGVs is fully predicted by the design path planning algorithm. After obtaining the measurement points and their radiation measurements, the radiation field of radioactive sources is reconstructed by the Gaussian process regression (GPR) model based on machine learning method. Based on the reconstructed radiation field, the locations of radioactive sources can be determined by the peak analysis method. The proposed method is verified through extensive simulation experiments, and the real source localization experiment on a Cs-137 point source shows that the proposed method can accurately locate the radioactive source with an error of approximately 0.30 m. The experimental results reveal the important practicality of our proposed method for source autonomous localization tasks.

• 한국도서관정보학회지
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• 제31권1호
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• pp.87-114
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• 2000

The purpose of this study is offering appropriate system and training program to helf the system designer and the trainer in addition to analyze information use behavior about the web search tools and evaluate the estimated system by user groups. The results of the study are as follows $\circledS1$ It is desirable to consider age than other demographic variables in the case of web search tool. $\circledS2$ It is desirable to design Directory Search Tool in the case of web search tool which serves the student user group. $\circledS3$ An Intelligent Search Tool is more appropriate for the students who are using keyword search tool than any other tools. $\circledS4$ A discussion about standard classification of the web information should be accomplished soon because users feel confused in using web search tools due t o absence of standard mode of classification about classified item. $\circledS5$ Librarians need the cognition about data on internet s a source of information and need positive service and user training program about these information because student users hardly get help from librarians or library orientation for learning method to use web search tool. $\circledS6$ Internet use experience and years of computer use had effect on their use ability when using web search tool, whereas computer use experience, library use experience and Online Public Access Catalogs (OPAC) use experience had no effect on it. Especially, OPAC use experience had no effect on use ability of web search tool of student user group because student user groups had no information about internet and web search tool and they did not recognized the difference about search method between web search tool and OPAC. $\circledS7$In the case of web search tool, it si important to index the increasing web resource automatically by a searching robot. But in the case of student users, web search tool is much more needed to index by index expert due to the absence of ability about selecting and combining keyword.

• 로봇학회논문지
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• 제3권3호
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• pp.186-193
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• 2008

We propose a novel real-time obstacle avoidance method for rescue robots. This method, named the ELA(Emergency Level Around), permits the detection of unknown obstacles and avoids collisions while simultaneously steering the mobile robot toward safe position. In the ELA, we consider two sensor modules, PSD(Position Sensitive Detector) infrared sensors taking charge of obstacle detection in short distance and LMS(Laser Measurement System) in long distance respectively. Hence if a robot recognizes an obstacle ahead by PSD infrared sensors first, and judges impossibility to overcome the obstacle based on driving mode decision process, the order of priority is transferred to LMS which collects data of radial distance centered on the robot to avoid the confronted obstacle. After gathering radial information, the ELA algorithm estimates emergency level around a robot and generates a polar histogram based on the emergency level to judge where the optimal free space is. Finally, steering angle is determined to guarantee rotation to randomly direction as well as robot width for safe avoidance. Simulation results from wandering in closed local area which includes various obstacles and different conditions demonstrate the power of the ELA.

• 한국해양공학회지
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• 제33권6호
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• pp.620-626
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• 2019

With the development of robot technology, the expectation of autonomous mission operations has increased, and the research on robot control architectures and mission planners has continued. A scalable and robust control architecture is required for unmanned surface vehicles (USVs) to perform a variety of tasks, such as surveillance, reconnaissance, and search and rescue operations, in unstructured and time-varying maritime environments. In this paper, we propose a robot control architecture along with a new utility function that can be extended to various applications for USVs. Also, an additional structure is proposed to reflect the operator's command and improve the performance of the autonomous mission. The proposed architecture was developed using a robot operating system (ROS), and the performance and feasibility of the architecture were verified through simulations.

• 한국지능시스템학회논문지
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• 제8권4호
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• pp.27-35
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• 1998

자율 주행 로봇이 주어진 환경에 대한 정보를 이용하여 장애물을 회피하며 안전하고 효율적으로 목표지점까지 주행하기 위해서는 최적의 이동 경로가 생성되어야 한다. 본 논문에서는 유전 알고리즘을 이용하여 고정 및 움직이는 장애물이 존재하는 작업환경 내에서 전역경로 계획, 지역경로 계획을 결정하는 방법을 제안한다. 이동 로봇은 유전 알고리즘을 이용하여 먼저 최적의 전역 경로를 탐색하고 미지의 장애물을 발견하면 이와 충돌을 회피하기 위해 새로운 지역 경로를 탐색한다. 또한 움직이는 장애물이 작업공한내 존재하면 이동 로봇은 이를 피하기 위해 최적의 경로를 탐색한다. 본 논문에서는 제안한 유전 알고리즘은 기존의 알고리즘에 비해 국부적 최소 값에 빠지지 않고 경로 탐색능력이 효율적임을 확인하였다.

• 한국산학기술학회논문지
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• 제10권2호
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• pp.237-242
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• 2009

이동로봇은 고정된 로봇에 비해 작업영역을 확장할 수 있다는 장점이 있다. 하지만 이러한 장점은 센서들을 사용하여 자신의 위치를 추정하거나 로봇이 원하는 목적지를 파악함으로써 얻어질 수 있다. 본 논문은 전방향 위치추정 시스템을 이용한 이동로봇의 주행방법에 대하여 설명하고 있다. 이 시스템은 간단한 위치검출 장치를 이용하여 간소화된 위치 데이터를 프로세서에 제공한다. 즉, 사용자가 로봇의 도착점을 지시하면 이 시스템이 위치 방향을 실시간으로 비교 분석하여 오차를 보정한다. 이를 위하여 원뿔형 거울과 단일 카메라를 사용하였다. 이 결과, 사용자가 로봇을 움직이기 위해 가리킨 타겟을 찾아내는 영상처리 시간을 줄일 수 있었다.

• 대한전기학회논문지:시스템및제어부문D
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• 제51권5호
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• pp.182-189
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• 2002

This paper presents a framework of hybrid dynamic control systems for the motion control of wheeled mobile robot systems with nonholonomic constraints. The hybrid control system has the 3-layered hierarchical structure: digital automata for the higher process, mobile robot system for the lower process, and the interface as the interaction process between the continuous dynamics and the discrete dynamics. In the hybrid control architecture of mobile robot, the continuous dynamics of mobile robots are modeled by the switched systems. The abstract model and digital automata for the motion control are developed. In high level, the discrete states are defined by using the sensor-based search windows and the reference motions of a mobile robot in low level are specified in the abstracted motions. The mobile robots can perform both the motion planning and autonomous maneuvering with obstacle avoidance in indoor navigation problem. Simulation and experimental results show that hybrid system approach is an effective method for the autonomous maneuvering in indoor environments

• 한국전자통신학회논문지
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• 제9권8호
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• pp.907-914
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• 2014

본 논문에서는 실내 환경에서 작업하는 로봇의 무 충돌 경로계획을 위하여 휴리스틱 작업 경로계획 방법을 제안한다. 이 방법은 모양공간을 격자로 분할하여 작은 크기의 격자를 여러개 합한 큰 격자로 장애물 모양공간을 재구성 하여 시작점의 노드와 목표점의 노드간의 연결을 노드와 노드사이의 거리와 장애물의 확률적 분포 같은 지역적인 정보를 이용하여 통로를 만들고 그 공간에서 작은 격자의 모양공간에서 그래프 연결을 찾는 방법으로 경로 및 작업을 계획하는 방법이다. 이 방법은 전체 모양공간에 대한 그래프를 기억시킬 필요가 없어 모양공간 내에서 노드나 격자의 증가에 따른 기억용량의 증가가 크지 않으며 전체 그래프에 대한 탐색을 하지 않으므로 계산량이 많지 않다. 제안한 알고리즘의 평가를 위하여 이동 로봇이 격자화된 실내지형에 대하여 최단거리의 경로계획을 성공적으로 수행하였음을 확인하였다.

• Journal of Electrical Engineering and Technology
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• 제10권6호
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• pp.2368-2375
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• 2015

To accommodate various navigational commands, a humanoid should be able to change its walking motion in real time. Using the modifiable walking pattern generation (MWPG) algorithm, a humanoid can handle dynamic walking commands by changing its walking period, step length, and direction independently. If the humanoid is given a command to perform an infeasible movement, the algorithm substitutes the infeasible command with a feasible one using binary search. The feasible navigational command is subsequently translated into the desired center-of-mass (CM) state. Every sample time CM reference is generated using a zero-moment-point (ZMP) variation scheme. Based on this algorithm, various complex walking patterns can be generated, including backward and sideways walking, without detailed consideration of the feasibility of the navigational commands. In a previous study, the effectiveness of the MWPG algorithm was verified by dynamic simulation. This paper presents experimental results obtained using the small-sized humanoid robot platform DARwIn-OP.

• 한국감성과학회:학술대회논문집
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• 한국감성과학회 2000년도 춘계 학술대회 및 국제 감성공학 심포지움 논문집 Proceeding of the 2000 Spring Conference of KOSES and International Sensibility Ergonomics Symposium
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• pp.301-305
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• 2000

The present study is part of the Special Research Project for the Construction of a Kansei Sensory Evaluation Model that is currently underway at the University of Tsukuba. In this study, a robot was operated by remote control at an actual art museum as part of a preliminary experiment. The results obtained therefrom were used to consider how people might view exhibits. In a previous study, a standard lens and s wide-angle lens were used to analyze differences in sensory-based movements, while VRML was used to analyze differences in these movements between a virtual and an actual museum. In the present study, the time delay in remote operation, which is currently unavoidable, placed some restrictions on the degree of freedom with which exhibits could be viewed, but it was apparent that sensory evaluation could be possible depending on the search behavior and viewing time. Furthermore specific viewing behaviors using the robot were observed, suggesting that new Kansei sensory perceptions were derived from these behaviors.