• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.36 no.7
• /
• pp.666-673
• /
• 2008

To construct the accurate radio satellite navigation system, the efficient communication each satellite with the ground station is very important. Throughout the communication, the orbit of each satellite can be corrected, and those information will be used to analyze the satellite satus by the operator. Since there are limited resources of ground station, the schedule of antenna's azimuth and elevation angle should be optimized. On the other hand, the satellite in the medium earth orbit does not pass the same point of the earth surface due to the rotation of the earth. Therefore, the antenna pass schedule must be updated at the proper moment. In this study, Q learning approach which is a form of model-free reinforcement learning and genetic algorithm are considered to find the optimal antenna schedule. To verify the optimality of the solution, numerical simulations are conducted.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.44 no.7
• /
• pp.611-619
• /
• 2016

This paper proposes a collision prevention system for an agricultural unmanned helicopter. The collision prevention system consists of an obstacle detection system, a mapping algorithm, and a collision avoidance algorithm. The obstacle detection system based on a LiDAR sensor is implemented in the unmanned helicopter and acquires distance information of obstacles in real-time. Then, an obstacle mapping is carried out by combining the distance to the obstacles with attitude/location data of the unmanned helicopter. In order to prevent a collision, alert is activated to an operator based on the map when the vehicle approaches to the obstacles. Moreover, the developed collision prevention system is verified through flight test simulating a flight pattern aerial spraying.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.24 no.1
• /
• pp.52-57
• /
• 2014

This paper presents an implementation of a smooth path planning method considering physical limits on a real time operating system for a two-wheel mobile robot. A Bezier curve is utilized to make a smooth path considering a robot's position and direction angle through the defined path. A convolution operator is used to generate the center velocity trajectory to travel the distance of the planned path while satisfying the physical limits. The joint space velocity is computed to drive the two-wheel mobile robot from the center velocity. Trajectory planning, velocity command according to the planned trajectory, and monitoring of encoder data are implemented with a multi-tasking system. And the synchronization of tasks is performed with a real-time mechanism of Event Flag. A real time system with multi-tasks is implemented and the result is compared with a non-real-time system in terms of path tracking to the designed path. The result shows the usefulness of a real-time multi-tasking system to the control system which requires real-time features.

• The Korean Journal of Air & Space Law and Policy
• /
• v.21 no.2
• /
• pp.9-53
• /
• 2006

오늘날 항공기사고는 우리나라뿐만 아니라 세계도처에서 때때로 발생되고 있다. 특히 외국항공기의 돌연한 추락 또는 물건의 낙하로 인해 지상에 있는 제3자에게 손해를 입히는 경우가 간혹 발생되고 있다. 이와 같은 사건에 있어 가해자(항공기운항자)는 피해자(지상 제3자)에 대하여 불법행위책임을 부담하게 되는데 이 사건해결을 위하여 1952년 및 1978년의 개정로마조약 등이 있음으로 본 논문에서는 이들 조약의 성립경위 및 주요내용과 개정이유 등을 설명하였다. 현재 국제민간항공기관(ICAO)에서는 2001년도 미국의 9,11테러사건 이후 이와 같은 사건의 법적조치와 대응을 위하여 1952년 개정로마조약의 현대화에 관한 새로운 조약초안이 발표되었다. 본 논문에서는 이 새로운 조약초안의 현대화를 위한 ICAO의 활동과 이 조약 초안에 대한 주된 내용과 필자의 논평(견해)을 밝히었다. 한편 본 논문에서는 항공운송인의 책임에 관계된 국제조약과 세계 각국(미국, 영국, 독일, 프랑스, 러시아, 오스트레일리아, 중국 등)의 입법례 등을 참작한 후 우리나라의 현실에 적합한 항공운송법 시안에 관한 국내입법의 추진방향과 항공운송약관의 효력문제, 동법시안을 제정하여야만 되는 이유, 입법경위, 입법방안, "항공운송법 시안"의 주요항목 등 작성하여 제시하였다.

• The Journal of the Korea Contents Association
• /
• v.21 no.7
• /
• pp.157-163
• /
• 2021

A single write operation in a file system can modify multiple data, but these changes in the file system are not atomically written to disk. Thus, for the consistency of the file system, conventional journaling guarantees crash consistency instead of sacrificing the system performance. It is known that using non-volatile memory as a journal space can alleviate performance degradation due to low latency and byte-level accessibility of non-volatile memory. However, none of the journaling techniques considering non-volatile memory provide scalability. In this paper, journal space on non-volatile memory is divided into multiple regions for scalable journaling, thus dispersing concentrated operations in one region. Second, the journal area-specific operator structure is used to accelerate data write operations to storage devices. We apply the proposed technique to JFS to evaluate it on multi-core servers equipped with high-performance storage devices. The evaluation results show that the proposed technique performs better than the existing technique of the NVM-based journaling file system.

• Korean Journal of Computational Design and Engineering
• /
• v.1 no.1
• /
• pp.1-19
• /
• 1996

Non-manifold topological representations can provide a single unified representation for mixed dimensional models or cellular models and thus have a great potential to be applied in many application areas. Various boundary representations for non-manifold topology have been proposed in recent years. These representations are mainly interested in describing the sufficient adjacency relationships and too redundant as a result. A model stored in these representations occupies too much storage space and is hard to be manipulated. In this paper, we proposed a compact hierarchical non-manifold boundary representation that is extended from the half-edge data structure for solid models by introducing the partial topological entities to represent some non-manifold conditions around a vertex, edge or face. This representation allows to reduce the redundancy of the existing schemes while full topological adjacencies are still derived without the loss of efficiency. To verify the statement above, the storage size requirement of the representation is compared with other existing representations and present some main procedures for querying and traversing the representation. We have also implemented a set of the generalized Euler operators that satisfy the Euler-Poincare formula for non-manifold geometric models.

• 제어로봇시스템학회:학술대회논문집
• /
• 2003.10a
• /
• pp.2676-2681
• /
• 2003

The Haptic Exploration Laboratory at The Johns Hopkins University is currently exploring many problems related to haptics (force and tactile information) in human-machine systems. We divide our work into two main areas: virtual environments and robot-assisted manipulation systems. Our interest in virtual environments focuses on reality-based modeling, in which measurements of the static and dynamic properties of actual objects are taken in order to produce realistic virtual environments. Thus, we must develop methods for acquiring data from real objects and populating pre-defined models. We also seek to create systems that can provide active manipulation assistance to the operator through haptic, visual, and audio cues. These systems may be teleoperated systems, which allow human users to operate in environments that would normally be inaccessible due to hazards, distance, or scale. Alternatively, cooperative manipulation systems allow a user and a robot to share a tool, allowing the user to guide or override the robot directly if necessary. Haptics in human-machine systems can have many applications, such as undersea and space operations, training for pilots and surgeons, and manufacturing. We focus much of our work on medical applications.

• 제어로봇시스템학회:학술대회논문집
• /
• 2003.10a
• /
• pp.622-627
• /
• 2003

The existing remote control system have some inherent disadvantage of direct control in the limit range. In some special cases, for example, a power apparatus, an unmanned factory, a nuclear factory, a security management system, the tele-operation is needed to control remote robot without limit space. This field is based on the Internet communication. Because the Internet is constructed all over the world. And it is possible that we control remote mobile robot in the long distance. In this paper, we developed a remote control system. This system is divided into two primary parts. These are local site and remote site. There are the moving robot and web server in the remote site and there is the robot control device in local site. The moving robot is moved by two stepper motors and the robot control device consists of SA-1100 micro controller and embedded Linux. And this controller is an embedded system. Public personal computer which is connected the Internet is used for the web server. The web server provides the mobile robot control interface program to the remote controller and captures the image for feedback information. In the whole system, a robot control device is connected with moving robot and web server through the Internet. So the operator can control the moving robot in the distance through the Internet.

• Journal of The Korean Association of Information Education
• /
• v.4 no.2
• /
• pp.179-186
• /
• 2001

The purpose of this study is to design and implement a courseware that makes possible interaction between man and computer in the internet. For this, We select the contents of learning and designe a courseware with text, graphic data. HTML, Java script and Java applet. Some advantages of the courseware are as follows. Interactions between man and computer are possible by giving diverse feedback to input-response in the web. And it is possible to access the courseware regardless of time and space when the network environment of user's computer is suitably equipped. Finally, on operator's part, the revision of the courseware becomes easier and on client's part, the system resources are less required.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.11 no.6
• /
• pp.470-476
• /
• 2001

This paper presents a new algorithm of path planning and obstacle avoidance for autonomous mobile robots with vision system that is working in unknown environments. Distance variation technique is used in path planning to approach the target and avoid obstacles in work space as well . In this approach, the Sobel operator is employed to detect edges of obstacles and the distances between the mobile robot and the obstacles are measured. Fuzzy rules are used for trajectory planning and obstacle avoidance to improve the autonomy of mobile robots. It is shown by computer simulation that the proposed algorithm is superior to the vector field approach which sometimes traps the mobile robot into some local obstacles. An autonomous mobile robot with single vision is developed for experiments. We also show that the developed mobile robot with the proposed algorithm is navigating very well in complex unknown environments.