• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.10
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• pp.765-772
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• 2020

A lot of studies to overcome the limitation of flight time have been studied, since the requirement of complicated mission achievement of aircraft including Unmanned Aerial Vehicles(UAVs) has been increased. The fuel limitation could bring about not enough flight time to accomplish missions. For this reason, the rendezvous maneuver is required to accomplish aerial refueling missions. The rendezvous guidance law based on variable pursuit guidance is designed using Lyapunov stability theory in this study. Numerical simulation is performed to demonstrate the performance of the proposed rendezvous guidance.

• Journal of the Korea Society for Simulation
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• v.16 no.3
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• pp.65-74
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• 2007

A tactic manager which can change the behavior of a simulation model according to the tactic definition file has been studied and implemented. Based on the DEVS(discrete event system specification) formalism, we generated a simulation model which is equipped with the inter ace to the tactic manager. To demonstrate the effectiveness of the tactic manager, a target motion analysis simulation of the warfare between a submarine and a surface ship is simulated.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.1
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• pp.49-56
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• 2016

Flapper Valve of Korean Utility Helicopter(KUH-1) is an essential equipment in Environmental Control System(ECS) for pilot to perform flight mission. It provides pilots and crews with heating, ventilating and air conditioning. It has function of maintaining room temperature to sustain operational capability for pilot and crew. This paper summarizes pilot comments in flight test which are classified by cause of occurrence and the troubleshooting process about each comment. It also describes design improvements which was derived from troubleshooting and suggests verification results of flight test at low temperature.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.6
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• pp.496-503
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• 2003

SFC system has come to be used as drive large synchronous machine in many industry applications. Many papers have been presented on the control algorithm of SFC system, not the acceleration and start-up but the rated speed operation with line connection and the braking operation with regeneration which is used in the industry. This paper presents the whole section control algorithm for a large synchronous machine using SFC system. The results of experiment show that the proposed algorithm is proper and effective.

• IEMEK Journal of Embedded Systems and Applications
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• v.2 no.2
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• pp.128-136
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• 2007

무선 기술이 가지는 장점인 설치의 편리성, 기동성으로 인하여, ZigBee를 이용한 홈 네트워크 서비스 활용성에 대한 기술개발이 활발히 진행되고 있다. 이러한 유비쿼터스 홈 서비스의 활용성에도 불구하고 ZigBee 기반 홈 기기나 센서 정보의 도청, 비정상적인 패킷의 유통, 메시지 재사용등의 데이터 위/변조 문제와 네트워크 전체를 마비시킬 수 있는 서비스 거부 공격등에 쉽게 노출되어 있다. 본 논문에서는 이에 대한 효과적인 대응과 관리 처리를 위하여, 유비쿼터스 홈 네트워크에서의 ZigBee 기술을 사용할 시에 발생할 수 있는 보안 문제점을 해결하기 위한 ZigBee 기반 End-to-End 보안 기술을 개발하였다. 본 기술 개발의 특징은 ZigBee Device, 코디네이터/게이트웨이 영역은 ZigBee 표준 스펙을 구현하였으며, 응용어플리케이션/서버 영역은 표준 스펙이 정의 되어 있지 않으나, 이 부분을 유비쿼터스 홈 네트워크 서비스 관점에서 설계 및 구현하였다. ZigBee 디바이스가 가지는 하드웨어 자원의 빈약성을 고려하여 최대한 보안 기능을 리소스가 풍부한 응용어플리케이션/서버의 자원 활용에 촛점을 맞췄다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.2
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• pp.173-180
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• 2014

In this paper, the instrument flight certification process and flight test results of Korean Utility Helicopter (KUH) are presented. For the instrument flight certification, the suitability of installed equipments and instruments have been reviewed and verified by ground and flight tests. Next, static and dynamic stability test are conducted in accordance with FAR-29 Appendix B. The static stability is determined by the change of speed and attitude according to control inputs. The dynamic stability is evaluated by how quickly the response of the helicopter due to long and short period control inputs are decreased. The pilot workload evaluation are also carried out by simulated IMC flight tests. This paper presents the workload assessment results when some failures are occurred at cockpit instruments, engine or flight control systems as well as the normal situation. After the simulated IMC flight test is completed, actual instrument flight test are conducted in a real IMC environment according to the air traffic controls.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.3
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• pp.21-29
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• 2011

This paper presents a method that estimates distance and velocity of an object with reliability regardless of maneuver status of the target in stereo vision system. A stereo vision system can calculate a distance with disparity from left and right images. However, the distance estimation error may occur due to quantization error of image pixel. A sub-pixel interpolation method minimizes the quantization error and estimates accurate disparity with real value. Extended Kalman filter (EKF) was used to minimize the error covariance and estimate the object's velocity. However, divergence problem occurs due to model uncertainty when a target maneuvers highly, which makes the estimation error increase. In this paper, we propose a virtual model extended Kalman filter (VMEKF) method that minimizes the processing time and provides reliable estimation ability regardless of maneuver status. Computer simulations and experimental results in real road environments demonstrate that the proposed method gives a reliable estimation performance and reduces processing time under various maneuver status while comparing other estimation filters.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.12
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• pp.986-993
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• 2018

Lateral thrust jet has better maneuverability performance than the control surface like the conventional fin for attitude control or orbital transition of guided weapons. However, in the supersonic region, a jet interaction flow occurs due to the lateral thrust jet during flight, and a complicated flow structure is exhibited by the interaction of the shock wave, boundary layer flow, and the vortex flow. Especially, hit-to-kill interceptors require precise control and maneuvering, so it is necessary to analyze the effect of jet interaction flow. Conventional jet interaction analyses were performed under low altitude conditions, but there are not many cases in the case of medium altitude condition, which has different flow characteristics. In this study, jet interaction flow analysis is performed on the lateral jet controlled interceptor operating at medium altitude. Based on the results, the structural characteristics of the flow field and the changes of aerodynamic coefficient are analyzed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.11
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• pp.934-943
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• 2018

In these days, demand for agile spacecraft is gradually increasing, due to the fact that agile spacecraft can improve mission capability. In this paper, an attitude control logic based on reaction wheels that can enhance agility of spacecraft is proposed. Three methods are suggested, and all three or part of them can be integrated to the existing attitude control system. First, a feedforward/feedback controller is introduced, and its pros and cons are provided, compared to the conventional feedback controller. Second, an attitude command generation method that fully utilizes torque/momentum capacities of reaction wheels is proposed. Third, a torque (current) control mode for internal wheel control is introduced. Numerical results verify that the settling time can be significantly reduced by employing the feedforward/feedback control method, especially for large angle maneuver.

• Journal of the Korean association of regional geographers
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• v.3 no.1
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• pp.35-50
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• 1997

The purpose of this research seeks to analyze the spatial variations in the sex age structure which have been shown to exist within the study atrea, the Kyonggi province in Korea. In this study it is desired to use the Age Structure Index developed by Coulson in order to describe thi sex age structure of each of 186 tracts that comprise the tracted portion of the Kyonggi province. The mechanics of computing the Age Structure Index are found in the equation describing a linear least squares trend line: y=a+bx. For each census tract, the percentage of the population in each age group(y) was plotted against the middle age of each age group(x). The a is a constant representing the value of y, when x equals zero. The b is the regression coefficient and is a measure of the angle of the slope of the least squares trend line. Thus the value of b is the Age Structure Index for each census tract. The major results of this investigation can be summarized as follows: The spatial distributions of sex age structures in the Kyonggi province are far from random. They have exhibited great regularity with the yonger sex age structures near Seoul and a sharp decline to the older sex age structures out in all derections towards rural region. The results of this investigation should have important general significance for the study of the Kyonggi province Age Structure Index is a flexible, operational definition shich allows sex age structure to be measured, mapped, and incorporated in a wide variety of methods of statistical analysis. Futurer, it has been demonstrated that sex age structure varies spatially within Seoul metropolitan finge and that this variation is relagfed to many other attributes of the population. Especially, Age Structure Index is strongly related to the variables-rate of population growth rate. density, rate of numbers of manufacturing, land price. At the same time, considerably more research is needed before a genmeral body of knowlege concerning sex age structure can be developed.