• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 심포지엄 논문집 정보 및 제어부문
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• pp.92-94
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• 2004

We become an industry information society which is advanced to the altitude with the today. The information to be loading various goods each other together at a circumstance environment is increasing extremely. The restriction recognizes the data of many Quantity and it follows because the human deals the task to classify. The development of a mathematical formulation for solving a problem like this is often very difficult. But Artificial intelligent systems such as neural networks have been successfully applied to solving complex problems in the area of pattern recognition and classification. So, in this paper a neural network approach is used to recognize and classification problem was broken into two steps. The first step consist of using a neural network to recognize the existence of purpose pattern. The second step consist of a neural network to classify the kind of the first step pattern. The neural network leaning algorithm is to use error back-propagation algorithm and to find the weight and the bias of optimum. Finally two step simulation are presented showing the efficacy of using neural networks for purpose recognition and classification.

• Journal of Astronomy and Space Sciences
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• 제37권4호
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• pp.229-236
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• 2020

There has been increasing necessity of more precise prediction and measurements of aviation radiation in Korea. For our air crew and passengers' radiation safety, we develop our own radiation prediction model of KREAM. In this paper, we validate the KREAM model based on comparison with Liulin observations. During early three months of this year, we perform total 25 experiments to measure aviation radiation exposure using Liulin-6K in commercial flights. We found that KREAM's result is very well consistent with Liulin observation in general. NAIRAS shows mostly higher results than Liulin observation, while CARI-6M shows generally lower results than the observations. The percent error of KREAM compared with Liulin observation is 10.95%. In contrast, the error for NAIRAS is 43.38% and 22.03% for CARI-6M. We found that the increase of the altitude might cause sudden increase in radiation exposure, especially for the polar route. As more comprehensive and complete analysis is required to validate KREAM's reliability to use for the public service, we plan to expand these radiation measurements with Liulin and Tissue Equivalent Proportional Counter (TEPC) in the near future.

• 전기학회논문지
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• 제67권7호
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• pp.871-877
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• 2018

In this paper, we propose a triple nested PID control scheme for stable hovering of a quadrotor and propose a complementary filter based sensor fusion technique to improve the performance of attitude, altitude and velocity measurement. The triple nested controller has a structure in which a double nested attitude controller that has the angular velocity PD controller in inner loop and the angular PI controller in outer loop, is nested in a velocity control loop to enable stable hovering even in the case of disturbance. We also propose a sensor fusion technique by applying a complementary filter in order to reduce the noise and drift error included in the acceleration and gyro sensor and to measure the velocity by fusing image, gyro, and acceleration sensor. In order to verity the performance, we applied the proposed control and measurement scheme to hovering control of quadrotor.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.891-896
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• 2007

This paper contained the flight test calibration for the airspeed indicator and the altimeter of the light airplane ChangGong-91, which is the first type certified aircraft from Korean Ministry of Construction and Transportation, as a part of the flight test validation. The flight test for airspeed position error calibration was performed using tower fly by method in order to calibrate swivel head testboom which is attached to the right wing tip of the airplane, and using system to system method for airspeed indicator. The altimeter calibration was calculated using flight test data for airspeed calibration. The flight test was conducted at the basis of the 'Korean Airworthiness Standard' regulation of Korean Ministry of Construction and Transportation.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.64.1-64
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• 2001

Errors in inertial navigation system(INS) can be divided into two major groups which are system related errors and modeling errors due to approximation and linearization. Measurement noise, calibration, and alignment errors make up the first group, whereas the uncertainties in the gravity vector fall in the second category and are important error source for high quality INS, especially during high altitude and and/or long time missions, when the gravity errors tent to build up. The quality of a medium to high accuracy INS depends on the knowledge of the local gravity field. In this paper, the feasibility of improving airborns INS by use of more accurate gravity model is studied. To make consistent comparisons, WGS-84 parameters are used and ...

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.419-424
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• 1991

In this paper, a fuel minimizing closed loop explicit inertial guidance algorithm for the orbit injection of a rocket is developed. In this formulation, the fuel burning rate and magnitude of thrust are assumed constant, and the motion of a rocket is assumed to be subject to the average inverse-square gravity, but with negligible atmospheric effects. The optimum thrust angle for obtaining the given velocity vector in the shortest time with minimizing fuel consumption is first determined, and then the additive thrust angle for targeting the final position vectors is determined by using Pontryagin's Maximum Principle. To establish the real time processing, many algorithms of the onboard guidance software are simplified. Simulations for the explicit guidance algorithm, for the 2nd-stage flight of the N-1 rocket, are carried out. The results show that the guidance algorithm works well in the presence of the maximum .+-.10 % initial velocity and altitude error. The effects of the guidance cycle time is also examined.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.386-388
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• 2007

In many applications of UAVs flying in low altitude, the steady supply of accurate height measurements is very important for the UAVs to complete their mission successfully. In order to do this, a barometer or GPS height measurements are widely used. However, because these two sensors have their limitations in the application environment, a method for fusing these two measurements to produce reference heights are required. In this paper, a reference height generation filter is designed for UAV(Unmanned Air Vehicle) applications. The barometer errors originated by the change of the atmospheric environment are modeled using random walk models, and then the errors are identified and compensated through the ZSB(zero-scan-back) filter algorithm using the GPS height measurements. The performance of the proposed filter is demonstrated by realistic simulations.

• 한국항공우주학회지
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• 제33권2호
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• pp.75-83
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• 2005

NASA와 독일 DLR의 Gravity Recovery and Climate Experiment (GRACE)는 편대비행을 하는 두 개의 저궤도 위성을 이용하여 지구중력장을 측정하는 연구이다. 주요 관측 장비는 위성 사이의 거리를 측정하기 위한 초단파 거리측정기와 비중력 가속도를 측정하기 위한 정전기 방식의 3축 가속도계이다. 기본설계 및 허용오차 분석 등에 활용하기 위하여 정밀한 관측기 시뮬레이션 모델을 개발하였는데, 본 논문에서는 이러한 모델링 기법과 이를 적용한 궤도 및 중력장 추정기법에 관해 살펴보았다.

• 환경영향평가
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• 제18권1호
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• pp.31-39
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• 2009

A lot of data which are used in environment analysis of air pollution have characteristics that are distributed continuously in space. In this point, the collected data value such as precipitation, temperature, altitude, pollution density, PM10 have spatial aspect. When geostatistical data analysis are needed, acquisition of the value in every point is the best way, however, it is impossible because of the costs and time. Therefore, it is necessary to estimate the unknown values at unsampled locations based on observations. In this study, spatial interpolation method such as local trend surface model, IDW(inverse distance weighted), RBF(radial basis function), Kriging were applied to PM10 annual average concentration of Seoul in 2005 and the accuracy was evaluated. For evaluation of interpolation accuracy, range of estimated value, RMSE, average error were analyzed with observation data. The Kriging and RBF methods had the higher accuracy than others.

• 한국통신학회논문지
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• 제22권7호
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• pp.1448-1458
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• 1997

In this paper the reverse link of the GLOBALSTAR-the representative CDMA LEO satellite system and LEO mobile satellite channel are developed by the SPW software simulation tool. And the performance of the system is evaluated. GLOBALSTAR is designed to give cellular-type service to hand-held user terminals through a constellation of 48 LEO satellites in circular orbites with 1414 Km altitude. Since LEO mobile satellite system communicates with mobile unit, it is suffered from severe multipath fading and shadowing. The fast mobility of LEO satellites makes the channel condition time vering. So, the LEO mobile satellite channel is different from land mobile channels. In this unique LEO satellite channel, it is shown that the performance of the GLOBALSTAR reverse link is varied according to the elevational angle, but this variation is overcome by satellite path diversity.