• Title/Summary/Keyword: star sensor

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A Weather Monitoring System for Local Area Using an Energy-balanced Hybrid WSN Protocol (에너지 균등 하이브리드 WSN 프로토콜 기반 국지 기상 관측 시스템)

  • Lee, Hyung-Bong;Chung, Tae-Yun
    • IEMEK Journal of Embedded Systems and Applications
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    • v.9 no.4
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    • pp.193-203
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    • 2014
  • This paper implements a weather monitoring system based on wireless sensor network. The wireless sensor network protocol proposed in this paper adopts a TDMA styled MAC. The protocol is designed to balance the energy consumption among sensor nodes. Other purposes of the protocol are to avoid the hidden terminal problem in 2-hop star topology, and to allow a CSMA styled communication in a given time slot to support emergent messages. Also, this paper develops the hardware of sensor node, gateway and electric generator based on solar and windy energy. The test results on the implemented system show that the time slot of each node is shifted in circular manner to balance the waiting time for transmission, and the reliability of wireless communication is over 99%.

Implementation of the Alert System for Safety of Workers (근로자의 안전을 위한 경보시스템 구현)

  • Kim, In-Min;Ko, Bong-Jin
    • Journal of Advanced Navigation Technology
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    • v.15 no.6
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    • pp.1138-1142
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    • 2011
  • This paper proposes the Alert System, the purpose of which is to detect an accident and to take care of it quickly in a working place. In the previous studies, a wireless network system was suggested using 'Star Topology'. However, this study constructs the wireless network system of Peer-to-Peer Topology, which allows to build more efficient network for communication. Also, with this system it is possible to check other the worker's situation through double sensing with Temperature/Gas sensor and Inclination sensor. In order to take action quickly, the Alert System is using a monitoring program which visualizes a worker's situation and the area where an accident occurs.

ISRMC-MAC: Implementable Single-Radio, Multi-Channel MAC Protocol for WBANs

  • Cho, Kunryun;Jeon, Seokhee;Cho, Jinsung;Lee, Ben
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.10 no.3
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    • pp.1052-1070
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    • 2016
  • Wireless Body Area Networks (WBANs) have received a lot of attention as a promising technology for medical and healthcare applications. A WBAN should guarantee energy efficiency, data reliability, and low data latency because it uses tiny sensors that have limited energy and deals with medical data that needs to be timely and correctly transferred. To satisfy this requirement, many multi-radio multi-channel MAC protocols have been proposed, but these cannot be implemented on current off-the-shelf sensor nodes because they do not support multi-radio transceivers. Thus, recently single-radio multi-channel MAC protocols have been proposed; however, these methods are energy inefficient due to data duplication. This paper proposes a TDMA-based single-radio, multi-channel MAC protocol that uses the Unbalanced Star+Mesh topology to satisfy the requirements of WBANs. Our analytical analysis together experiments using real sensor nodes show that the proposed protocol outperforms existing methods in terms of energy efficiency, reliability, and low data latency.

An Investigation in the Thermal Effect on a Low Earth Orbit Satellite under Yaw Motion for the Visibility of a Star Sensor (저궤도 위성에서 별센서의 가시성을 위한 Yaw Motion에 따른 열적 영향 고찰)

  • Kim, Hui-Kyung;Lee, Jang-Joon;Hyun, Bum-Seok
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.37 no.7
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    • pp.709-716
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    • 2009
  • Thermal condition according to the operation attitude of a satellite in orbit would be essential to be known because the orbit attitude is a dominant factor to affect satellite thermal design. In this paper, the change in space thermal environment and the thermal effect in thermal design are studied for a low earth orbit satellite according to the yaw motion. The present satellite retains sun-pointing attitude during daylight due to the fixed type solar arrays. And it also moves along the orbit with constant yaw motion in a longitudinal axis so that a star tracker which is a star sensor for satellite's attitude control always looks into the deep space. This attitude is considered in its better visibility to the stars for a successful mission operation. Also, it is required to access the corresponding thermal effects due to the yaw motion. Therefore, we try to verify these by the thermal analysis for the satellite thermal model with the yaw motion.

Performance Prediction of a Laser-guide Star Adaptive Optics System for a 1.6 m Telescope

  • Lee, Jun Ho;Lee, Sang Eun;Kong, Young Jun
    • Current Optics and Photonics
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    • v.2 no.3
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    • pp.269-279
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    • 2018
  • We are currently investigating the feasibility of a 1.6 m telescope with a laser-guide star adaptive optics (AO) system. The telescope, if successfully commissioned, would be the first dedicated adaptive optics observatory in South Korea. The 1.6 m telescope is an f/13.6 Cassegrain telescope with a focal length of 21.7 m. This paper first reviews atmospheric seeing conditions measured over a year in 2014~2015 at the Bohyun Observatory, South Korea, which corresponds to an area from 11.6 to 21.6 cm within 95% probability with regard to the Fried parameter of 880 nm at a telescope pupil plane. We then derive principal seeing conditions such as the Fried parameter and Greenwood frequency for eight astronomical spectral bands (V/R/I/J/H/K/L/M centered at 0.55, 0.64, 0.79, 1.22, 1.65, 2.20, 3.55, and $4.77{\mu}m$). Then we propose an AO system with a laser guide star for the 1.6 m telescope based on the seeing conditions. The proposed AO system consists of a fast tip/tilt secondary mirror, a $17{\times}17$ deformable mirror, a $16{\times}16$ Shack-Hartmann sensor, and a sodium laser guide star (589.2 nm). The high order AO system is close-looped with 2 KHz sampling frequency while the tip/tilt mirror is independently close-looped with 63 Hz sampling frequency. The AO system has three operational concepts: 1) bright target observation with its own wavefront sensing, 2) less bright star observation with wavefront sensing from another bright natural guide star (NGS), and 3) faint target observation with tip/tilt sensing from a bright natural guide star and wavefront sensing from a laser guide star. We name these three concepts 'None', 'NGS only', and 'LGS + NGS', respectively. Following a thorough investigation into the error sources of the AO system, we predict the root mean square (RMS) wavefront error of the system and its corresponding Strehl ratio over nine analysis cases over the worst ($2{\sigma}$) seeing conditions. From the analysis, we expect Strehl ratio >0.3 in most seeing conditions with guide stars.

KOMPSAT-2 Geometric Cal/Val Overview and Preliminary Result Analysis (다목적실용위성2호 기하검보정 및 초기결과 분석)

  • Seo, Doo-Chun;Lee, Dong-Han;Song, Jeong-Heon;Park, Su-Young;Lim, Hyo-Suk
    • Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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    • 2007.04a
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    • pp.145-148
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    • 2007
  • The Korea Multi-Purpose Satellite-2 (KOMPSAT-2) was launched in July 2006 and The main mission of the KOMPSAT-2 is a high resolution imaging for the cartography of Korea peninsula by utilizing Multi Spectral Camera (MSC) images. The camera resolutions are 1 m in panchromatic scene and 4 m in multi-spectral imaging. KOMPSAT-2 measure the position, velocity and attitude data of satellite using by star sensor, gyro sensor, and GPS sensor. This paper provides an initial geometric accuracy assessment of the KOMPSAT-2 high resolution image, both geometric Cal/Val overview.

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Compensation of SDINS Navigation Errors Using Line-Of-Sight Vector (시선벡터를 이용한 관성항법장치의 보정기법)

  • Lim, You-Chol;Yim, Jong-Bin;Lyou, Joon
    • Proceedings of the IEEK Conference
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    • 2003.07c
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    • pp.2521-2524
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    • 2003
  • Since inertial sensor errors which increase with time are caused by initial orientation error and sensor errors (accelerometer bias and gyro drift bias), the accuracy of these devices, while still improving, is not adequate for many of today's high-precision, long-duration sea, aircraft, and long-range missile missions. This paper presents a navigation error compensation scheme for Strap-Down Inertial Navigation System (SDINS) using Line-Of-Sight(LOS) vector from star sensor. To be specific, SDINS error model and measurement equation are derived, and Kalman filter is implemented. Simulation results show the bounded-ness of position and attitude errors.

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Correlation analysis between rotation parameters and attitude parameters in simulated satellite image

  • Yun, Young-Bo;Park, Jeong-Ho;Yoon, Geun-Won;Park, Jong-Hyun
    • Proceedings of the KSRS Conference
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    • 2002.10a
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    • pp.553-558
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    • 2002
  • Physical sensor model in pushbroom satellite images can be made from sensor modeling by rotation parameters and attitude parameters on the satellite track. These parameters are determined by the information obtained from GPS, INS, or star tracker. Provided from satellite image, an auxiliary data error is connected directly with an error of rotation parameters and attitude parameters. This paper analyzed how obtaining satellite images influenced errors of rotation parameters and attitude parameters. furthermore, for detailed analysis, this paper generated simulated satellite image, which was changed variously by rotation parameters and attitude parameters of satellite sensor model. Simulated satellite image is generated by using high-resolution digital aerial image and DEM (Digital Elevation Model) data. Moreover, this paper determined correlation of rotation parameter and attitude parameters through error analysis of simulated satellite image that was generated by various rotation parameters and attitude parameters.

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Recognition of 3-Dimensional Environment for a Mobile Robot Using Structured Light (Structured Light을 이용한 이동 로보트의 3차원 환경인식)

  • Lee, Seok-Jun;Chung, Myung-Jin
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.26 no.7
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    • pp.30-41
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    • 1989
  • In this paper, a robust and simple structured light sensory system has been studied to endow mobile robots with the ability of navigating in real world. A mobile robot with this sensor can be applied in two ways: first, real time navigation in 3-dimensional world, second, modeling and recognition of environment. Range data obtained with this sensor are fairy accurate, and the data aquisition speed is satisfactory. Experiments in diverse situation show effectiveness of the structured light sensor for the mobile robot.

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Path Planning for an Intelligent Robot Using Flow Networks (플로우 네트워크를 이용한 지능형 로봇의 경로계획)

  • Kim, Gook-Hwan;Kim, Hyung;Kim, Byoung-Soo;Lee, Soon-Geul
    • The Journal of Korea Robotics Society
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    • v.6 no.3
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    • pp.255-262
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    • 2011
  • Many intelligent robots have to be given environmental information to perform tasks. In this paper an intelligent robot, that is, a cleaning robot used a sensor fusing method of two sensors: LRF and StarGazer, and then was able to obtain the information. Throughout wall following using laser displacement sensor, LRF, the working area is built during the robot turn one cycle around the area. After the process of wall following, a path planning which is able to execute the work effectively is established using flow network algorithm. This paper describes an algorithm for minimal turning complete coverage path planning for intelligent robots. This algorithm divides the whole working area by cellular decomposition, and then provides the path planning among the cells employing flow networks. It also provides specific path planning inside each cell guaranteeing the minimal turning of the robots. The proposed algorithm is applied to two different working areas, and verified that it is an optimal path planning method.