• Journal of Korea Multimedia Society
• /
• v.16 no.6
• /
• pp.689-699
• /
• 2013

There are four methods such as 1:1, 1:N, N:1, and N:N in the tele-operating system for control the remote side robot. The operator must know the information of surroundings of the robot, collision possibility of the mobil equipment, and force feedback of the manipulator. The time delay problem occurs in the tele-operating and it causes vibration and expressive power of the manipulator owing to bidirectional force feedback. N:N control technique having been developed lately has a switching algorithm for the operator to select the target robot or it's partial equipment. When multi-operators work together to accomplish a task with multi-robots, the switching facility must be offered. And the automatic tuning skill to generalize the operator's tendency is needed also. We describes the methodologies and skills for developing a haptic-based tele-operating environments to makes it possible to control the remote multi-robots with multi-operators in this paper.

• Journal of Satellite, Information and Communications
• /
• v.12 no.1
• /
• pp.76-80
• /
• 2017

With the fast growing popularity of small UAVs (Unmanned Aerial Vehicles), recent UAV systems have been designed and utilized for the various field with their own specific purposes. UAVs are opening up many new opportunities in the fields of electronics, sensors, camera, and software for pilots. Increase in awareness and mission capabilities of UAVs are driving innovations and new applications driven with the help of low cost and its capability in undertaking high threat task. In particular, small unmanned aerial vehicles should fly in environments with high probability of unexpected sudden change or obstacle appearance in low altitude situations. In this paper, current researches regarding techniques of autonomous flight of smal UAV systems are introduced and we propose a draft idea for planning paths for small unmanned aerial vehicles in adversarial environments to arrive at the given target safely with low cost sensors.

• Journal of KIISE:Information Networking
• /
• v.37 no.2
• /
• pp.142-149
• /
• 2010

In this paper, we propose to modify the IEEE 802.16 MAC protocol in order to allow the coexistence of IEEE 802.11 and IEEE 802.16 wireless networks in shared bands. Our suggested protocol enables 802.16 WMAN to control WLAN devices for the coexistence. That is, in the downlink subframes(BS to SS), SS(Subscriber Station) prohibits WLAN to transmit by using CTS(Clear to Send) in order to protect it's burst. In the uplink subframes(SS to BS), on the other hand, BS(Base Station) sends CTS to block WLAN's communications. Our proposals enables the coexistence between WLAN and WMAN, and simulation results show that our protocols enhance the throughput of the entire system.

• Journal of Satellite, Information and Communications
• /
• v.10 no.1
• /
• pp.83-87
• /
• 2015

LED navigation light installed on the ship performs a important role to ensure safety and prevent collisions with other ships. LED navigation light is mainly used in the night and within the limited visibility by smoke, rainfall. In particular, LED navigation light installed with a clear understanding. LED navigation light is consist of LED module, a control board, a converter, a Fresnel lens, such as enclosure. Russian Society of LED navigation light (RMRS) of the ship to be delivered by drying at Daewoo Shipbuilding & Marine Engineering requires guaranteed reliable products at below $-52^{\circ}C$. conventional LED navigation light has to ensure quality at $-25{\sim}40^{\circ}C$. So, LED navigation light should ensure a problems of random failure or long time operation. In this paper, we present the current status and future plans of reliability so far.

• Journal of KIISE
• /
• v.42 no.4
• /
• pp.530-540
• /
• 2015

Industrial WSNs need great performance and reliable communication. In industrial WSNs, cluster structure reduces the cost to form a network, and the reservation-based MAC is a more powerful and reliable protocol than the contention-based MAC. Depth-based TDMA assigns time slots to each sensor node in a cluster-based network and it works in a distributed manner. DB-TDMA is a type of depth-based TDMA and guarantees scalability and energy efficiency. However, it cannot allocate time slots in parallel and cannot perfectly avoid a collision because each node does not know the total network information. In this paper, we suggest an improved distributed algorithm to reduce the end-to-end delay of DB-TDMA, and the proposed algorithm is compared with DRAND and DB-TDMA.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.9 no.2
• /
• pp.388-394
• /
• 2008

In this paper, MAC(Medium Access Control) algorithm for the IEEE 802.11 DCF(Distributed Coordination Function) improving the performance is proposed and analyzed by simulation. The MAC of IEEE 802.11 WLAN to control data transmission uses two control methods called DCF and PCF(Point Coordination function). The DCF controls the transmission based on CSMA/CA(Carrier Sense Multiple Access With Collision Avoidance). The DCF shows excellent performance relatively in situation that competition station is less but has a problem that performance is fallen from throughput and delay viewpoint in situation that competition station is increased. This paper proposes an enhanced DCF algorithm that increases the CW to maximal CW after collision and decreases the CW smoothly after successful transmission in order to reduce the collision probability by utilizing the current status information of WLAN. To prove efficiency of proposed algorithm, a lots of simulations are conducted and analyzed.

• Journal of KIISE:Computing Practices and Letters
• /
• v.9 no.6
• /
• pp.674-682
• /
• 2003

Ship autonomous navigation is designated as what computerizes mental faculties possessed of navigation experts, which are building navigation plans, grasping the situation, forecasting the fluctuation, and coping with the situation. An autonomous navigation system, which consists of several subsystems such as navigation system, a collision avoidance system, several data fusion systems, and a motion control system, is based on an intelligent control architecture for the sake of integrating the systems. The motion control system, which is one of the most essential system in autonomous navigation system, controls its propulsion and steering gears to move the ship satisfying its hydrodynamic characteristics. This paper is the study on the ship movement control system and its implementation which are totally developed and run on virtual-world system. Receiving the high-level control values such as a waypoint presented from the collision avoidance system, the motion control system generates them to low-level control values for propulsion and steering devices. In the paper, we develop a ship motion controller using Oldenburger's theory based on mathematical fundamentals, and simulate it with various scenarios in order to verify its performance.

• The Bulletin of The Korean Astronomical Society
• /
• v.36 no.2
• /
• pp.130.1-130.1
• /
• 2011

인류의 우주공간에 대한 영향력이 확대됨에 따라, 우주공간에서의 인위적인 활동에 영향을 미칠 수 있는 모든 종류의 상황들에 대한 이해가 최근 전 세계적으로 매우 중요한 이슈로 부상하고 있다. 이를 Space Situational Awareness (SSA)라고 하는데, 특히 근지구공간에서의 인위적, 자연적 우주물체는, 우주발사체의 지속적인 증가와 이리듐-코스모스 위성의 상호 충돌 및 중국 폐기위성 파괴 등과 같은 사건으로 기하급수적으로 증가된 우주물체의 개체수로 인해 대한민국 국적의 모든 위성에도 실제적인 위협 요인으로 대두되고 있다. 이에 기초 기술연구회와 한국천문연구원은 이러한 위협을 국가적으로 해결해야할 과제(National Agenda Project) 중의 하나로 정의하고, 이를 해결하기 위해 우주물체 전자광학 감시체계 기술개발(OWL; Optical Wide-field patroL) 사업을 시작하였다. 이 사업의 목표는 자국위성에 대한 궤도력을 독자적으로 유지할 수 있는 시스템을 개발하는 것이며, 이를 위하여 2011년부터 6년 동안 총 5개소의 해외 관측소에 50cm급 광시야 망원경을 각각 설치하여 자국위성을 자동으로 상시관측하고, 관측된 자료를 이용한 궤도계산을 통하여 독자적으로 궤도력을 유지할 계획이다. 또한, 우주잔해물 감시는 하나의 국가에서 단독으로 할 수 없기 때문에 2m급 우주물체 감시망원경을 개발하여 국제공동으로 진행할 계획이다. 사업 첫해인 2011년 4월 시스템 요구사항 분석을 완료하였고 10월말 시스템 기본설계를 완료할 예정이다. 최종 완성될 소구경 광시야 망원경과 우주물체 감시망원경의 주요 임무는 우주물체 관측이지만, 향후 광시야를 이용한 다양한 탐사천문학에도 기여할 수 있을 것으로 기대한다. 한편, 자국위성에 대한 충돌 위험도 분석 및 회피기동에 관한 연구는 한국항공우주연구원이 이 사업의 협동연구로 참여하고 있다.

• The Journal of Society for e-Business Studies
• /
• v.15 no.4
• /
• pp.49-58
• /
• 2010

The wireless sensor network technology becomes one of core technologies to make it possible to implement various e-business applications. Energy efficiency is an important issue in wireless sensor networks. IEEE 802.15.4, a representative international standard for wireless sensor networks, provides the beacon enabled mode for energy-efficient communication. However, the beacons may conflict each other when the network is of multi-hop topology such as mesh or cluster-tree topology with beacon-enabled mode. The beacon conflict causes the failure of synchronization between sensor nodes, and affects other nodes in the network in that unsynchronized nodes cannot participate in communication. In this paper, we suggest an energy-efficient beacon scheduling for the wireless sensor networks. Nodes can save their energy duringperiod and prevent beacon conflict using beacon scheduling. We implement the scheduling using QualNet, and evaluate the performance under mesh topology networks. It turns out that the proposed scheduling may improve the energy efficiency in the networks.

• Journal of Advanced Marine Engineering and Technology
• /
• v.40 no.9
• /
• pp.830-835
• /
• 2016

With the relaxation of regulations on unmanned aerial vehicles (UAVs) in the USA, the development of related industries is expected. Hence, it is anticipated that the number the UAVs will reach approximately 600,000 in the USA in 2017. However, automated flights of commercial UAVs are restricted owing to concerns about accidents. To deal with the possibility of collisions, several studies on collision prevention and the routing of UAVs have been conducted. However, these studies do not deal with various situations dynamically or provide efficient solutions. Therefore, we propose a centralized routing method for the UAV that uses vehicular networks. In the proposed scheme, vehicular networks regard UAVs as data packets to be routed. Accordingly, the proposed method reduces UAV processing power required for route searches. In addition, the routing efficiency for UAV flight paths can be improved since congestion can be minimized by using a vehicular network.