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Attitude Maneuver Control of Flexible Spacecraft by Observer-based Tracking Control
Hyochoong Bang,Choong-Seok Oh 대한기계학회 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.1
A constraint equation-based control law design for large angle attitude maneuvers of flexible spacecraft is addressed in this paper. The tip displacement of the flexible spacecraft model is prescribed in the form of a constraint equation. The controller design is attempted in the way that the constraint equation is satisfied throughout the maneuver. The constraint equation leads to a two-point boundary value problem which needs backward and forward solution techniques to satisfy terminal constraints. An observer-based tracking control law takes the constraint equation as the input to the dynamic observer. The observer state is used in conjunction with the state feedback control law to have the actual system follow the observer dynamics. The observer-based tracking control law eventually turns into a stabilized system with inherent nature of robustness and disturbance rejection in LQR type control laws.<br/>
Robust Time-Optimal Control for Flexible Structure Vibration Control by Augmented Dynamics
Hyochoong Bang,Hyun Jae Lee,Youn-Ju Eun 한국항공우주학회 2004 International Journal of Aeronautical and Space Sc Vol.5 No.1
Robust optimal control problem for flexible spacecraft/structures using on-off type discrete actuators has been a subject of intensive research. Optimization by switching time parameterization can be used to minimize the maneuver time subject to equality boundary constraints. Sensitivity of the switching times with respect to modal parameters could be a critical factor degrading the performance of the time optimal solutions. A new approach for the robustness enhancement of switching times with respect to modal parameter uncertainty is introduced. A new concept so-called augmented dynamic model is added to account for the modal uncertainty. The proposed approach turns out to be similar to some previous methods, but it essentially provides some new results.
Nonlinear Trajectory Tracking using Vectorial Backstepping Approach
Hyochoong Bang,Sangjong Lee,Haechang Lee 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10
This paper discussed a nonlinear trajectory tracking problem for stratospheric airship platform and a novel approach of the nonlinear control scheme is applied. Target airship model is the 200m stratospheric airship platform capable of flying upto 20 km altitude. Full 6-DOF nonlinear dynamics of unmanned airship are defined according to the target airship’ configuration including the moving windfield. Based on this airship model, a backstepping design formulation for the trajectory tracking control is described. The tracking control strategy of vectorial backstepping is applied to derive the tracking control law and global asymptotically stability is proved by Lyapunov stability analysis. Finally, numerical simulations have been carried out to assess the performance of the proposed tracking controller.
Nonlinear Attitude Control for a Rigid Spacecraft by Feedback Linearization
Hyochoong Bang,Jung-Shin Lee,Youn-Ju Eun 대한기계학회 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.2
Attitude control law design for spacecraft large angle maneuvers is investigated in this paper. The feedback linearization technique is applied to the design of a nonlinear tracking control law. The output function to be tracked is the quaternion attitude parameter. The designed control law turns out to be a combination of attitude and attitude rate tracking commands. The attitude-only output function, therefore, leads to a stable closed-loop system following the given reference trajectory. The principal advantage of the proposed method is that it is relatively easy to produce reference trajectories and associated controller.<br/>
2축 김벌의 가변속도 CMG를 이용한 인공위성 자세제어
방효충(Hyochoong Bang),박영웅(Youngwoong Park) 한국항공우주학회 2004 韓國航空宇宙學會誌 Vol.32 No.5
CMG(Control Momentum Gyro)는 일반적으로 동체에 부착된 반작용휠에 비해 큰 토크의 크기를 발생시켜 인공위성의 자세제어에 이용되는 장치이다. CMG는 휠의 각운동량벡터의 방향을 위성체의 동체축에 대하여 연속적으로 변화시킴으로써 자이로스코픽 토크를 발생하게 된다. 가변속도 CMG는 휠의 속도도 함께 변화시킴으로써 보다 다양한 제어 명령을 생성할수 있게 되고 또한 특이(Singularity) 조건을 피하는데 장점을 지니고 있다. 본 연구에서는 2축의 김발에 장착된 가변속도 CMG를 이용한 위성체의 자세 동역학 방적식을 유도하기로 한다. 이러한 운동방정식은 기존의 1축 김벌 시스템의 경우를 확장한 것이다. 또한 유도된 운동방정식을 활용하여 피드백 자세기동 제어 법칙을 제안하기로 한다. CMG(Control Momentum Gyro) is a control device being used for spacecraft attitude control constructing relatively large amount of torque compared to conventional body-fixed reaction wheels. The CMG produces gyroscopic control torque by continuously varying the angular momentum vector direction with respect to the spacecraft body. The VSCMG(Variable Speed Control Momentum Gyro) has favorable advantages with variable speed to lead to better control authority as well as singularity avoidance capability. Attitude dynamics with a VSCMG mounted on a two-axis gimbal system are derived in this study. The dynamic equation may be considered as an extension of the single-axis counterpart. Also, a feedback control law design is addressed in conjunction with the dynamic equations of motion.
Modified Rodrigues Parameter 기반의 인공위성 관성모멘트 추정 연구
방효충(Hyochoong Bang) 한국항공우주학회 2010 韓國航空宇宙學會誌 Vol.38 No.3
본 연구에서는 인공위성의 관성 모멘트 추정을 위해 MRP(Modified Rodrigues Parameter) 자세 변수기반의 추정기를 설계하였다. MRP는 인공위성 자세 결정시 쿼터니언(Quaternion) 파라미터의 구속 조건으로부터 발생하는 필터의 오차 공분산 행렬의 특이 (Singularity) 현상을 피할 수 있는 장점이 있다. 한편 MRP의 경우 자세각 변위가 클 경우에 역시 특이현상이 발생할 수 있어 이를 피하기 위해 적절한 자세각 범위에서 인위적 인 기준 운동을 생성하여 필터 설계에 적용하였다. 쿼터니언 파라미터의 단점을 극복하여 보다 안정된 오차 공분산 갱신 결과의 필터의 개선된 성능을 예상할 수 있다. This study addresses spacecraft moment of inertial estimation approach using Modified Rodrigues Parameters(MRP). The MRP offer advantage by avoiding singularity in Kalman Filter design for attitude determination caused by the norm constraint of quaternion parameters. Meanwhile, MRP may suffer singularity for large angular displacement, so that we designed appropriate reference attitude motion for accurate estimation. The proposed approach is expected to provide stable error covariance update with accurate spacecraft mass property estimation results.