• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2622-2624
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• 2005

화력발전소 보일러의 급수량은 유출되는 증기량에 맞추어 자동 조절된다. 유출 증기량이 변하는 상황에서도 이에 상응하는 급수량은 실시간으로 조절되어야 한다. 증기량과 급수량에 차이가 있으면 보일러의 보유 수량과 드럼의 수위가 변하게 되므로, '드림수위를 일정하게 유지하는 것'이 급수량제어의 목표라고 할 수 있다. 본 논문은 실제 운용되고 있는 설비를 대상으로 고찰한 내용이며, 급수펌프 구동력으로는 중기터빈을 사용한다. 증기터빈과 급수펌프는 같은 축으로 연결되어있으며, 급수량 조절은 급수펌프의 회전속도를 제어함으로써 이루어진다. 터빈에 사응되는 증기는, 고압과 저압 2종류이며, 저압 증기가 부족한 경우에 고압증기를 사용하는 구성으로 되어있다. 증기 밸브의 유량 특성에는 비선형성을 많이 포함하고 있었다. 이 외에도 급수펌프가 갖는 비선형성을 분석하였으며, 이 특성들을 모두 종합한 '증기터빈 속도제어기 튜닝 곡선'을 제시하였다

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.42.2-42.2
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• 2018

고전적인 소행성과 혜성의 경계는 무너지고 있다. 처음 발견했을 때는 소행성으로 분류됐던 천체도, 예기치 않은 활동성이 나타나면 혜성의 일원이 된다. 소행성은 충돌이나 회전가속에 의해 갑자기 활동성을 나타내기도 하지만, 강한 태양복사를 견디지 못하고 오랜 시간 간직해온 휘발성 물질을 우주 공간으로 흩뿌리기도 한다. 한국천문연구원 딥사우스 (DEEP-South) 팀은, 이렇게 태양 근방에서 혜성으로 탈바꿈할 것으로 예상되는 소행성으로 2000 XO8을 지목하고, 근일점을 막 지난 2017년 10월 말부터 KMTNet 망원경으로 약 한 달간 지속 관측을 하였다. 이 기간 동안 2000 XO8은 활동성이 급격히 증가하여 선명한 꼬리를 나타냈고, 이내 검출 한계 이하로 활동성이 줄어드는 것까지 확인하였다. 이번에 혜성으로 밝혀진 2000 XO8은 한국인 또는 한국 기관에서 새로 발견 및 동정한 것으로 알려진 혜성 중에 그 주기가 8.8년으로 가장 짧다. 이는 궤도장반경이 목성보다 안쪽에 위치한다는 점에서 이례적인 일이다. 우리는 궤도 실험을 통해 2000 XO8이 현 궤도에 자리 잡은 지 오래 되지 않았으며, 또 다른 주기 혜성 265P/LINEAR에서 쪼개져 나온 조각일 가능성을 제시하고자 한다.

• Proceedings of the Korea Society for Simulation Conference
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• 2003.06a
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• pp.49-54
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• 2003

일반 항공기의 유형을 고정익기과 회전익기로 구별할 수 있다면, MAV (Micro Air Vehicle)의 경우는 곤충이나 조류들의 날개 짓 (flapping) 비행형태인 ornithopter 형이 추가된다. 1993년 미국 RAND사에 의하여 MAV에 대한 타당성 검토(1)가 시작된 이례로 실로 다양한 실험적 형태의 MAV들이 속속 소개되고 있는 실정이다. MAV는 초소형 무인항공기로 길이는 성인의 손바닥 크기인 2.5 inch 정도이고, 개발비용과 기간이 유인항공기에 비해서는 비교할 수 없을 정도로 적게 소요되며. 동체길이가 2~5m인 일반 무인항공기에 비해서도 상대적으로 유리하다는 장점, 그리고 새로운 소형화 기술들을 평가할 수 있는 매우 훌륭한 시험장치가 될 수 있다는 이유로 항공우주기술 분야는 물론 MEMS나 나노기술 분야에서도 상당한 관심을 갖고 있는 실정이다. MAV의 비행 시뮬레이션 또는 시뮬레이터에 대한 현재까지의 국내외 연구개발 노력(2,3)은 MAV의 기체나 부품기술개발 노력에 비하여 상대적으로 뒤쳐져 있는데, 본 논문은 그 기술적 문제가 무엇인지를 분석하고, MAV비행 시뮬레이터 환경을 통해 수행될 수 있는 효과적인 연구개발 분야는 무엇인지를 조명하고자 한다. 또한, MAV비행 시뮬레이터의 성능 요구사항 도출을 통하여 개념설계를 제시하고, 세종대학교와 (주)모델심이 공동 개발중인 "RC Virtual Flight" 비행 시뮬레이터에 MAV가 어떻게 접목되고 있는지를 소개한다.있는지를 소개한다.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.6
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• pp.91-102
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• 2017

The early basic studies on RDE has been surveyed in the previous paper. Recently active researches are carrying on for the application to the power plant and aerospace propulsion systems. Collaboration researches are going on for the application of RDE for the gas turbine, liquid rocket and combined cycle engines in many countries. Following the previous Part 1 paper, present paper is intended to provide the comprehensive survey of recent worldwide efforts on the realistic application of RDE.

• Publications of The Korean Astronomical Society
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• v.21 no.2
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• pp.75-79
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• 2006

An alt-azimuth type mount system, developed at the Space Science and Technology Laboratory, Kyung Hee University, has been found to experience some difficulties in monitoring of the artificial space objects. Since the telescope installed on the alt-azimuth mount does not rotate on the same axis as the earth does, this mount system needs an instrument rotator to correct the field rotation. Although there are some commercial instrument rotators already in the market, those are not suitable for our system due to their low interchangeability. In this study, we have designed a new high speed instrument rotator and calculated the deformation of new designed system using structural analyses.

• Journal of Astronomy and Space Sciences
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• v.21 no.2
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• pp.141-152
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• 2004

Optics fabrication process for precision space optical parts includes bound abrasive grinding, loose abrasive lapping and polishing. The traditional bound abrasive grinding with bronze bond cupped diamond wheel leaves the machine marks of about $20{mu}m$ rms in height and the subsurface damage of about 1 ${mu}m$ rms in height to be removed by subsequent loose abrasive lapping. We explored an efficient quantitative control of precision CNC grinding. The machining parameters such as grain size, work-piece rotation speed and feed rate were altered while grinding the work-piece surfaces of 20-100 mm in diameter. The input grinding variables and the resulting surface quality data were used to build grinding prediction models using empirical and multi-variable regression analysis. The effectiveness of such grinding prediction models was then examined by running a series of precision CNC grinding operation with a set of controlled input variables and predicted output surface quality indicators. The experiment achieved the predictability down to ${pm}20$ nm in height and the surface roughness down to 36 nm in height. This study contributed to improvement of the process efficiency reaching directly the polishing and figuring process without the need for the loose abrasive lapping stage.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.8
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• pp.597-609
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• 2020

These days, the coaxial rotor system is used for various purposes like UAVs, Mars exploration helicopters, and the next-generation high-speed rotorcraft. A number of research projects on aerodynamic performance of rotor systems, including the coaxial configuration have been made previously. On the contrary, research on rotor blade deformation has been mainly carried out regarding the single rotor system, where such effort has not been enough on the coaxial system. Nonetheless, in case of the coaxial system, blade deformation analysis is much more important because of the complex air flow around the rotors, and that the distance between the two rotors is a key factor affects aerodynamic performance of the entire system. For these reasons, an experimental study on rotor blade deformation of the coaxial system was conducted using the Stereo Pattern Recognition(SPR) technique, one of the state-of-the-art of photogrammetry method. In this research, a small-scale coaxial rotor test stand designed by Korea Aerospace Research Institute(KARI) was used. With the same test stand, performance of the coaxial configuration had been studied before the experimental study on blade deformation, in order to find the relation between performance and blade deformation of the rotor system. Results of the performance test and the deformation study are presented in this article.

• Journal of Aerospace System Engineering
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• v.11 no.6
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• pp.10-16
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• 2017

In order to improve the safety of the multi-copter, Korea Aerospace Research Institute (KARI) performed a wind-tunnel test using an octocopter with the maximum takeoff weight (MTOW) of 28 kg. The wind-tunnel test was performed with three different RPM ranges, 3,500, 4,500 and 5,500 rpm, and three different wind speeds, 3.5, 5 and 7 m/sec. The tested range of the angle of attacks was $-40^{\circ}$ to $20^{\circ}degree$ and ${\pm}90^{\circ}degree$. Vortex ring state (VRS) of the tested multi-copter was located around the vertical descending speed of 6 m/sec and the decrement of thrust was about 13 % at the time of testing. Compared with the single propeller wind-tunnel test result, the propeller efficiency of the octocopter dropped to 10 to 15% depending on the propeller RPM. It is hypothesized that the obtained aerodynamic characteristics by the wind-tunnel test will be used to improve the performance and wind resistance of the multi-copter.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.2
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• pp.127-135
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• 2022

Compared to the continuous increase of domestic nano-satellite development cases, the initial communication success rate is relatively low. In a situation where communication cases of LEO satellites using commercial satellite communication networks are increasing recently. In this situation, the SNIPE project developed by the KASI(Korea Astronomy and Space Science Institute), KARI(Korea Aerospace Research Institute), and Yonsei University apply an Iridium module for communication test to the SNIPE nano-satellites. Therefore, in this paper, the visibility analysis of the iridium module on the SNIPE satellite was analyzed under considering the orbital and communication environment of the iridium satellite constellation and the attitude control mode. In the case of LEO satellites, the communication possibility was limited due to the relatively small iridium communication coverage for high altitude and the high doppler shift considered in the iridium communication network. For this reason, in this paper, it could be simulated that there was a more performance difference according to the difference in relative RAAN(Right Ascension of Ascending Node) angle with the Iridium constellation. Finally, by checking the visibility of communication module under the tumbling situation that occurred during the initial deployment of the nano-satellite, the possibility of using the iridium communication technology was analyzed.

• Journal of Aerospace System Engineering
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• v.16 no.1
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• pp.49-55
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• 2022

The role of drones has been expanded to various fields such as agriculture, construction, and logistics. In particular, agriculture drones are emerging as an effective alternative to solve the problem of labor shortage and reduce the input cost. In this study therefore, we proposed the fruit recognition algorithm and harvesting mechanism for fruit harvesting drone system that can safely harvest fruits at high positions. In the fruit recognition algorithm, we employ "You-Only-Look-Once" which is a deep learning-based object detection algorithm and verify its feasibility by establishing a virtual simulation environment. In addition, we propose the fruit harvesting mechanism which can be operated by a single driving motor. The rotational motion of the motor is converted into a linear motion by the scotch yoke, and the opened gripper moves forward, grips a fruit and rotates it for harvesting. The feasibility of the proposed mechanism is verified by performing Multi-body dynamics analysis.