• Journal of Astronomy and Space Sciences
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• 제29권4호
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• pp.413-422
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• 2012

In recent years, a number of missions have been planned and conducted worldwide on the planets such as Mars, which involves the unmanned robotic exploration with the use of rover. The rover is an important system for unmanned planetary exploration, performing the locomotion and sample collection and analysis at the exploration target of the planetary surface designated by the operator. This study investigates the development of mobility system for the rover ground model necessary to the planetary surface exploration for the benefit of future planetary exploration mission in Korea. First, the requirements for the rover mobility system are summarized and a new mechanism is proposed for a stable performance on rough terrain which consists of the passive suspension system with 8 wheeled double 4-bar linkage (DFBL), followed by the performance evaluation for the mechanism of the mobility system based on the shape design and simulation. The proposed mobility system DFBL was compared with the Rocker-Bogie suspension system of US space agency National Aeronautics and Space Administration and 8 wheeled mobility system CRAB8 developed in Switzerland, using the simulation to demonstrate the superiority with respect to the stability of locomotion. On the basis of the simulation results, a general system configuration was proposed and designed for the rover manufacture.

• 지구물리와물리탐사
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• 제12권4호
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• pp.355-360
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• 2009

USN (Ubiquitous Sensor Network, 유비쿼터스 무선네트워크) 융합기술을 기반으로 하는 자원탐사 축소모형 시스템을 구축하였다. 실제 환경의 재현을 위해, 비금속 모형판 아래 금속판을 설치하고, 모형판 위에서 이동로봇에 설치된 고정밀 3축 자기센서를 이용하여 실제 자장값을 계측한다. 측정된 자장값은 무선네트워크를 이용하여 이동로봇이 중앙 컴퓨터로 전송한다. 이러한 하드웨어 기반의 테스트 시스템은 현장 상황을 물리적으로 유사하게 재현함으로써, 시뮬레이션의 신뢰도가 높고, USN기반 자원탐사시스템 설계지침을 다각도로 검토할 수 있다. 본 연구에서는 금속물체 탐지시스템을 재현하기 위해, 평판 위에서 이동로봇을 사용하여, 평판 아래에 설치된 금속판의 위치를 탐지하는 실험을 성공적으로 실시하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.89-90
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• 2008

We present an implementation and it's real-sea test of an underwater acoustic communication system, which allows the system to reduce complexity and increase robustness in time variant underwater environments. For easy adaptation to complicated and time-varying environments of the ocean, all-digital transmitter and receiver systems were implemented. For frame synchronization the CAZAC sequence was used, and QPSK modulation/demodulation method with carrier frequency of 25kHz and a bandwidth of 5kHz were applied to generate 10kbps transmission rate including overhead. To improve transmission quality, we used several techniques and algorithms such as adaptive beamforming, adaptive equalizer, and convolution coding/Viterbi decoding. For the verification of the system performance, measurement of BER has been done in a very shallow water with depth of 20m at JangMok, Geoje. During the experiment, image data were successfully transmitted up to about 9.6km.

• 지구물리와물리탐사
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• 제19권4호
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• pp.236-248
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• 2016

이 해설에서는 물리탐사 및 지구물리 분야 실무자들의 측지 좌표계와 지도 투영에 관한 이해를 높이기 위해 이를 구성하는 요소들의 개념을 상세히 설명하였다. 지구 타원체, 지오이드, 지심 위도, 측지 위도, 경도, 항정선, 대원 등의 기본 개념을 자세히 설명하였다. 또한 현재 대표적으로 널리 사용되고 있는 지심 직각 좌표계, 경위도 좌표계에 대한 설명과 함께 좌표계 간의 좌표 변환에 대해서도 자세히 설명하였다. 이와 더불어 지역 측지 데이텀 변환 및 직각 좌표 투영에 대한 설명을 추가하고 우리나라 측지 좌표계에 대하여 요약하여 물리탐사 실무에서 좌표 체계를 더 잘 이해하고 사용할 수 있도록 하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.109-114
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• 2008

This paper presents the development status of a subscale precooled turbojet engine "S-engine" for the hypersonic cruiser and space place. S-engine employs the precooled-cycle using liquid hydrogen as fuel and coolant. It has $23cm{\times}23cm$ of rectangular cross section, 2.6 m of the overall length and about 100 kg of the target weight employing composite materials for a variable-geometry rectangular air-intake and nozzle. The design thrust and specific impulse at sea-level-static(SLS) are 1.2 kN and 2,000 sec respectively. After the system design and component tests, a prototype engine made of metal was manufactured and provided for the system firing test using gaseous hydrogen in March 2007. The core engine performance could be verified in this test. The second firing test using liquid hydrogen was conducted in October 2007. The engine, fuel supplying system and control system for the next flight test were used in this test. We verified the engine start-up sequence, compressor-turbine matching and performance of system and components. A flight test of S-engine is to be conducted by the Balloon-based Operation Vehicle(BOV) at Taiki town in Hokkaido in October 2008. The vehicle is about 5 m in length, 0.55 m in diameter and 500 kg in weight. The vehicle is dropped from an altitude of 40 km by a high-altitude observation balloon. After 40 second free-fall, the vehicle pulls up and S-engine operates for 60 seconds up to Mach 2. High altitude tests of the engine components corresponding to the BOV flight condition are also conducted.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1999년도 Proceedings of International Symposium on Remote Sensing
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• pp.158-164
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• 1999

This paper investigated and evaluated the NASA's Shuttle Imaging Radar-C (SIR-C) multiple frequency SAR data for differential backscattering effects of microwave from the surface geological materials overlying the skarn type mineralization. Although an integrated approach in mineral exploration is more cost effective and is well in use, there are still many technical and scientific issues to be further investigated and researched. In this study we have reprocessed several sets of previously surveyed exploration data and experimented with fuzzy logic digital fusion of the preprocessed data with respect to chosen exploration targets. Among the numerous fuzzy logic operators, which are currently available for a data driven integrated exploration strategy, we used varying combinations of fuzzy MIN, fuzzy MAX, and fuzzy SUM operators along with Gamma operator for fusion of exploration data, including the contact metamorphic zone information. The final exploration target tested was a skarn type W-Mo-F mineralization in the study area. The fuzzy logic derived mineral potential anomaly almost exactly matched the differential backscattering anomalies on the C-band and L-band SIR_C data when overlaid on each other. Although this high degree of correlation between these two data sets is remarkable, the differential backscattering anomaly over the skarn type W-Mo-F mineralization in the study area requires further investigation.

• Journal of Computing Science and Engineering
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• 제2권4호
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• pp.321-338
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• 2008

This paper presents a Modified Multiple Depth First Search algorithm for the exploration of the indoor environments occupied with obstacles in random distribution. The proposed algorithm was designed and implemented to employ one or a team of Khepera II mini robots for the exploration process. In case of multi-robots, the BlueCore2 External Bluetooth module was used to establish wireless networks with one master robot and one up to three slaves. Messages are sent and received via the module's Universal Asynchronous Receiver/Transmitter (UART) interface. Real exploration experiments were performed using locally developed teleworkbench with various autonomy features. In addition, computer simulation tool was also developed to simulate the exploration experiments with one master robot and one up to ten slaves. Computer simulations were in good agreement with the real experiments for the considered cases of one to one up to three networks. Results of the MMDFS for single robot exhibited 46% reduction in the needed number of steps for exploring environments with obstacles in comparison with other algorithms, namely the Ants algorithm and the original MDFS algorithm. This reduction reaches 71% whenever exploring open areas. Finally, results performed using multi-robots exhibited more reduction in the needed number of exploration steps.

• 항공우주시스템공학회지
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• 제9권4호
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• pp.16-22
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• 2015

Korea Aerospace Research Institute(here after KARI) has a plan to launch experimental lunar orbiter in 2018, and lunar orbiter and lander in 2020. There are several ways to go to the moon. Which one is direct transfer trajectory and another one is phasing loop transfer trajectory and the other one is WSB trajectory. Regardless of the transfer trajectories, LOI maneuver is the most important maneuver of all mission sequences because if this burn is failed, it is too difficult to get into the lunar orbit in the future. This paper describes first LOI target value of foreign lunar orbiters and analyzes orbital variations of experimental lunar orbiter according to various target values. By analyzing the variation of orbiter parameter after first LOI, proper orbital period for LOI target value are recommended to meet the inclination, apoapsis and periapsis altitude constraints.

• 한국해양공학회지
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• 제19권6호통권67호
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• pp.78-85
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• 2005

Initial alignment and localization are important topics in inertial navigation systems, since misalignment and initial position error wholly propagate into the navigation systems and deteriorate the performance of the systems. This paper presents the error convergence characteristics of the hybrid navigation system for underwater vehicles initial position, which is based on an inertial measurement unit (IMU) accompanying a range sensor. This paper demonstrates the improvement on the navigational performance oj the hybrid system with the range information, especially focused on the convergence of the estimation of underwater vehicles initial position error. Simulations are performed with experimental data obtained from a rotating ann test with a fish model. The convergence speed and condition of the initial error removal for random initial position errors are examined with Monte Carlo simulation. In addition, numerical simulation is conducted with an AUV model in lawn-mowing survey mode to illustrate the error convergence of the hybrid navigation System for initial position error.

• Spatial Information Research
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• 제21권3호
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• pp.21-30
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• 2013

최근 전 세계적인 육상자원의 고갈로 인하여 해저광물자원에 대한 관심이 증가하고 있다. 우리나라도 한반도 주변 해역의 해저광물자원을 확보하기 위한 탐사와 연구가 진행되고 있다. 탐사의 결과로 매년 해저자원 탐사자료가 생성되고 있으며, 데이터베이스와 2차원 GIS 기반 시스템을 구축하여 데이터를 관리하고 있다. 하지만 해저자원 탐사자료는 해저면 하부를 탐사하기 때문에 해저자원 탐사자료의 고차원적 분석을 위해서는 수심과 해저 지형의 시각적 확인이 중요하다. 따라서 본 연구에서는 GIS를 이용하여 한반도 주변에 대한 해저 지형 데이터를 구축하고 이를 3차원화하여 해저자원 탐사자료와 연계하는 3차원 GIS 기반의 표출 시스템 개발에 대한 연구를 진행하였다. 이를 위하여 한반도 주변 해역에 대한 수심 데이터를 획득하였고, 수심 데이터를 래스터 파일 형태로 보관하였다. 또한, 래스터 파일을 사용이 용이하도록 처리한 후 오라클에 구축하였다. 데이터베이스를 기반으로 ESRI사의 ArcScene을 이용하여 구축한 해저 지형 데이터의 3차원화와 해저자원 탐사자료 중첩 기능의 설계를 진행한 후, ArcObjects를 이용하여 시스템으로 구현하였다. 이러한 3차원 GIS를 이용한 해저자원 탐사자료의 활용은 해저 지형을 이용하여 탐사자료의 위치와 변화를 시각적으로 확인함으로써 탐사지역과 탐사자료에 대한 고차원적인 해석이 가능할 것으로 판단된다.