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진재현(Jaehyun Jin),이훈구(Hungu Lee),탁민제(Min-Jea Tahk) 한국항공우주학회 2007 韓國航空宇宙學會誌 Vol.35 No.6
본 논문에서는 반작용 휠을 사용하는 위성체의 내고장 제어 문제를 다루고 있다. 고장은 구동기(반작용 휠)에만 발생한다고 가정하였으며, 고장에 대해서도 자세에어 성능을 유지할 수 있는 제어알고리듬을 제안한다. 자세제어 루프는 각속도 제어 루프를 포함하고 있으며, 각속도 제어 루프에 시간지연제어 기법을 적용하여 고장에 대응할 수 있도록 한다. 제안한 제어기의 안정성 조건을 제시하며, 시뮬레이션을 통해 다양한 형태의 고장에 대해 안정된 자세 추종 성능을 검증한다. This paper considers a fault tolerant control problem for a spacecraft using reaction wheels. Faults are assumed to be inherent to only actuators(reaction wheels) and a control algorithm to accommodate actuators′ faults is proposed. An attitude control loop includes an angular velocity control loop. The time delay control method is used to make a spacecraft follow the command angular velocity and to accommodate actuators′ faults. A stability condition for the proposed algorithm is derived and the performance is demonstrated by computer simulations.
진재현(Jaehyun Jin),김동국(Dongguk Kim) 제어로봇시스템학회 2014 제어·로봇·시스템학회 논문지 Vol.20 No.5
This article focuses on a hemispherical resonator gyro driven by the Coriolis effect. A hemispherical shell, called a resonator, is maintained in the resonance state by amplitude control and phase locking control. Parametric excitation has been used to control the amplitude. For rate measurement mode or FTR mode, nodal points have been kept to an amplitude of zero. Angular rate measurement has been demonstrated by rotating a resonator. Frequency mismatch between two stiffness principal axes is a major cause of low performance: vibrating pattern drift and reduced control effectiveness. This mismatch has been reduced significantly by the addition of small mass. A negative spring effect, which lowers resonance frequencies, has been verified experimentally.
2개의 가변속 제어모멘트자이로를 이용한 인공위성의 자세제어
진재현(Jaehyun Jin) 제어로봇시스템학회 2015 제어·로봇·시스템학회 논문지 Vol.21 No.11
For the attitude control of spacecraft, two variable-speed control moment gyros are proposed as main actuators in the article. Since a variable-speed control moment gyro (VSCMG) makes two control torques (gyroscopic torque and reaction torque), two VSCMGs are sufficient for controlling 3-axes attitude. Additionally, there are no singular conditions for two non-parallel VSCMGs. Since gyroscopic torque is usually much greater than reaction torque, the control performances of approximately 3 axes may not be the same. However, several missions can be accomplished by controlling two axes. For such missions, a selective axes control method is proposed. The method selects two axes for a certain task and controls the attitude of the selected axes. For the remaining axis, angular speed is controlled for stabilization. A hardware-in-the-loop simulation has been used to test VSCMG modules and to verify the proposed method. Two VSCMGs can be alternative actuators for small satellites.
다중모델 칼만 필터를 이용한 무추력 비행체의 대기속도 추정
진재현(Jaehyun Jin),박정우(Jungwoo Park),김부민(Bumin Kim),김병수(Byoung Soo Kim),이은용(Eun Yong Lee) 제어로봇시스템학회 2009 제어·로봇·시스템학회 논문지 Vol.15 No.8
The article discusses an issue of estimating the airspeed of an autonomous flying vehicle. Airspeed is the difference between ground speed and wind speed. It is desirable to know any two among the three speeds fur navigation, guidance and control of an autonomous vehicle. For example, ground speed and position are used to guide a vehicle to a target point and wind speed and airspeed are used to maximize flight performance such as a gliding range. However, the target vehicle has not an airspeed sensor but a ground speed sensor (OPS/INS). So airspeed or wind speed has to be estimated. Here, airspeed is to be estimated. A vehicle’s dynamics and its dynamic parameters are used to estimate airspeed with attitude and angular speed measurements. Kalman filter is used for the estimation. There are also two major sources arousing a robust estimation problem; wind speed and altitude. Wind speed and direction depend on weather conditions. Altitude changes as a vehicle glides down to the ground. For one reference altitude, multiple model Kalman filters are pre-designed based on several reference airspeeds. We call this group of filters as a cluster. Filters of a cluster are activated simultaneously and probabilities are calculated for each filter. The probability indicates how much a filter matches with measurements. The final airspeed estimate is calculated by summing all estimates multiplied by probabilities. As a vehicle glides down to the ground, other clusters that have been designed based on other reference altitudes are activated. Some numerical simulations verify that the proposed method is effective to estimate airspeed.
확장형 미지입력 관측기를 이용한 위성 반작용 휠의 고장 검출
진재현(Jaehyun Jin),용기력(Ki-Ryeok Yong) 제어로봇시스템학회 2011 제어·로봇·시스템학회 논문지 Vol.17 No.11
This article deals with the problem of fault detection of a spacecraft’s actuators. The authors introduce an extended unknown input observer for nonlinear systems. This is an extended form of unknown input observers which are used for linear systems. Since faults are not available, those are considered as unknown inputs. Unknown input observers can estimate states without full information of inputs if some conditions are satisfied. The authors suggest a continuous-time extended UIO (eUIO) and prove the convergence of state estimation errors. Since the dynamic equation of a spacecraft is nonlinear, an extended UIO can be applied. Three eUIOs are designed to monitor three reaction wheels. The moving averages of each eUIO’s residuals are selected for decision logic. The proposed method is verified by numerical simulations.
1축 가변속 CMG를 장착한 부족구동 위성의 자세제어 특성 분석
진재현(Jaehyun Jin) 한국항공우주학회 2010 韓國航空宇宙學會誌 Vol.38 No.5
본 논문에서는 한 개의 1축 가변속 CMG를 장착한 부족구동 위성의 자세제어 문제를 다루고 있다. 이러한 부족구동 위성의 경우, 전체 모멘텀이 영(zero)이 아니면 자세를 임의로 취할 수 없다. 위성을 안정화 시키려면 가변속 CMG가 위성의 모멘텀 방향으로 정렬해야 하기 때문이다. 4가지의 다른 장착형상을 고려하였으며, 각각에 대해 제어가능 모멘텀 영역을 분석하였다. 또한 각 형상에 대해 백스테핑 기법을 이용하여 안정한 자세제어 법칙을 제시하고 자세제어 특성을 비교하였다. This paper deals with the attitude control of an underactuated spacecraft that has one single-gimbal variable-speed CMG. An underactuated spacecraft may not converge to arbitrary attitudes if its total angular momentum is not zero. To stabilize a spacecraft, the CMG has to align with the angular momentum in the inertial frame. Four different install configurations for the CMG have been considered and controllable angular momentums have been analyzed. Also, based on the backstepping method, stabilizing control laws have been presented and their properties have been compared.
진재현(Jaehyun Jin),최홍택(Hong-taek Choi),윤형주(Hyungjoo Yoon),김동국(Dongguk Kim),Sergii Sarapulov 제어로봇시스템학회 2013 제어·로봇·시스템학회 논문지 Vol.19 No.10
This article focuses on a hemispherical resonator gyro driven by the Coriolis effect. The operational principle of resonator gyros and mathematical models are introduced. These models are useful to explain the behavior of a resonator and to design controllers. Several control tests of a resonator have been done. A resonator has been excited by electromagnets controlled by a computer. Its amplitude has been adjusted by a PI control. The transient response is matched with a simulation result based on a mathematical model. A vibrating pattern may drift due to non-uniform factors of a resonator. The drift of the vibrating pattern is controlled and aligned to a reference direction by a PI control. These results are very useful to understand the behavior of resonator gyros and to design advanced control algorithm for better performance.