• Aerospace Engineering and Technology
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• v.11 no.2
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• pp.195-207
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• 2012

This paper deals with attitude controller design and integrated performance tests on the nitrogen gas reaction control system of KSLV-I. Some major factors which are necessarily required in designing a stabilizing controller of reaction control system are investigated, and the corresponding equations are given. Experimental configurations and test conditions for system level integrated performance tests of the KSLV-I nitrogen gas reaction control system are summarized. It is shown that, based on the experimental data, operational performances of nitrogen gas reaction control system can be analyzed in terms of gas consumption, thrusting force, time delay, and specific impulse. It is also shown that a conformance of the controller to flight can be evaluated. Finally the onboard controller of KSLV-I reaction control system is shown to perform normally with enough stability margin via the first flight test result.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.357-358
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• 2008

본 논문은 GPS를 이용한 무인 비행체의 자율비행에 관한 연구를 다루었다. 비행체의 종류는 크게 고정익기와 회전익기로 나뉘는데 본 연구에서는 회전익기의 형태를 가진 Quarter Vehicle을 사용하였다. Quarter Vehicle은 4개의 프로펠러에 의한 양력과 회전 반발력으로 비행을 한다. 이때의 양력은 수평면에 대해 수직으로 추력을 발생시키므로 다른 비행체보다 불안정하며 이를 안정하게 제어하기 위해 관성 센서를 적용하여 균형을 유지한다. 본 연구에서는 UAV의 자세와 균형을 안정적으로 유지하기 위해 관성센서를 적용하였으며 GPS를 활용하여 독립적인 자율비행이 가능하도록 하였다. 정확한 위치정보를 제공하는 GPS는 3개 이상의 위성으로부터 시간 및 위치 정보를 받아 좌표를 계산하고 비행체의 위치, 속도 및 방향을 결정하여 자율 비행이 가능하도록 한다. 또한 초형 지자기센서를 비행체에 적용하여 GPS의 방향 정보를 보완하도록 하였다. 본 논문에서는 무인 비행체의 자율비행의 기초가 되는 위치좌표 계산을 위한 GPS의 적용 방법과 비행경로계획 알고리즘을 제시 한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.4
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• pp.251-257
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• 2022

We formulated the convex optimization based minimum energy soft landing problem for reusable launch vehicles, and obtained the minimum time trajectory via the bisection search. In order to implement the the optimal guidance command and complete the flight control architectures on the soft landing stage, we designed the classical attitude control loops, and formulated and solved the optimal actuator allocation problem. The obtained soft landing guidance performance was analyzed via nonlinear 6-DOF simulation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.2
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• pp.133-140
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• 2015

In this paper, a roll angle estimation method of a rolling airframe using a low grade GPS and a roll rate gyro is proposed. The strength of the received signal of the GPS antenna attached on the rolling airframe is maximized when the GPS satellite is placed on the plane determined by the x-axis of the rolling airframe and the GPS antenna axis. Under the assumption that the x-axis of the rolling airframe is coincident with its velocity vector, the roll angle of the rolling airframe is calculated from the relative position vector of the satellite to the GPS when the GPS signal strength becomes maximum. The Kalman filter combined with a roll rate gyro is introduced to increase the determination accuracy of the roll angle. The performance of the proposed method is verified via 6-DOF simulations.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.3
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• pp.46-56
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• 2002

In this paper, the feasibility of the attitude control of a spacecraft using pulsed plasma thrusters(PPTs) is studied. The PPT consumes less propellant mass requied for the orbit management or attitude control owing to its high specific impulse characteristics, compared with traditional gas propulsion system. The PPT is expected to be highly adequete for the missions requiring long-duration operations because it has relatively long operation time and easy implementation. The feasibility of the PPT for attitude control of a small satellite system is addressed through realistic missions. The classical PD controller and a fuzzy logic controller are tested, and fuel saving fuzzy logic controller is then proposed for more flexible mission performance.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.6
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• pp.62-72
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• 2012

Divert and attitude control system(DACS) plays an important role for orbit transfer and attitude control, and therefore becomes important subject for recent space vehicle and Precision Guided Missile(PGM) development. To develop DACS system, main research areas include shape combination of pintle and nozzle to maximize thrust change, and reduction of aerodynamic pintle load to minimizle pintle driving force, and development of multi-axis control algorithm. In this paper, introduction, classification, and overseas/domestic research and development program, and prospects of DACS are reviewed and summarized.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.1
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• pp.1-8
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• 2013

A liquid-monopropellant hydrazine thruster has several outstanding advantages such as relatively-simple structure, long/stable propellant storability, clean exhaust products, and so on. Therefore hydrazine thruster has such a wide application as orbit and attitude control system (ACS) for space vehicles. A hydrazine thruster with the medium-level thrust to be used in the ACS of space launch vehicles (SLV) has been developed, and its ground firing test result is presented in terms of thrust, impulse bit, temperature, and chamber pressure. It is verified through the performance test that the response and repeatability of thrust are very excellent, and the thrust efficiencies compared to its ideal requirement are larger than 93%.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.7
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• pp.529-536
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• 2020

Reaction Control System of the third stage of the Korean Space Launch Vehicle II conducts roll control and 3 axis control throughout third stage engine start, satellite separation, and collision and contamination avoidance maneuver. Reaction control system consumes its propellant in each thruster operation. Hence, loading of proper amount of the propellant is important for mission success. It is needed to have a rough estimation method of propellant consumption during the flight. In this paper, we developed a energy equation using pressure and temperature data which are acquired in the on-board reaction control system. We constructed a test system which is similar with the on-board reaction control system to verify the energy equation. Test results using deionized water were compared with estimated propellant consumption. We also conducted an error analysis of the energy equation. We also presented the propellant consumption result of a system level operation test.

• 한국항공운항학회:학술대회논문집
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• 2015.11a
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• pp.50-54
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• 2015

구형무인비행체는 다중 모터를 이용한 무인항공기에 비행 소형화, 경량화, 경제화 등의 장점을 가지고 있다. 본 논문에서는 구형무인비행체의 경로 추종을 위한 제어기 설계 및 성능에 대한 내용을 다루고 있다. 먼저 구형무인비행체의 운동방정식이 제어기 설계를 위해 유도되었고, 유도된 운동방정식을 이용해 경로 추종 제어기를 설계하였다. 구형무인비행체의 자세제어는 무게중심을 변화하는 방법을 사용하였다. 요구 경로를 설정하여 설계된 제어기의 경로 추종 성능을 MATLAB 시뮬레이션을 통해 확인하였다. 시뮬레이션 결과, 제시된 제어기가 설정된 경로를 추종하고 있음을 확인하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.3
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• pp.311-318
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• 2004

It is required to design the RF link with sufficiently stable signal margin to minimize bit errors and improve the quality of received data in the telemetry system modulated digitally like PCM/FM. In case of the vehicle flying at a high speed, the variation of the gain pattern between transmitting and receiving antenna and the fee space loss due to flight distance cause the fluctuation of link. In this paper, KSR(Korea Sounding Rocket)- III, the first domestic liquid rocket which was successfully launched in Nov. 2002 is introduced. The SNR(signal-to-noise ratio) variation of the telemetry signal which was measured at S-band ground station, the one which was simulated considering the flight trajectory, and the attitude variation such as roll, pitch and yaw are compared, analyzed, and agree very well. In addition, two virtual flying situations are simulated and evaluated-only one antenna is equipped in one case, and rocket is roll-free in the other.