• 한국항공운항학회지
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• 제19권3호
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• pp.10-15
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• 2011

위성용 분리장치는 작동 전까지는 높은 체결력으로 위성의 부속물들을 안정된 체결 상태로 유지해야 한다. 작동 후에는 위성시스템에 손상이 없이 위성본체로부터 분리되어 태양전지판과 안테나와 같은 부속장치의 전개를 성공적으로 수행하여야 한다. 따라서 본 논문에서는 분리충격이 작고 취급이 용이하며 재장착이 가능한 형상기억합금구동기와 태엽스프링을 이용한 소형위성용 비폭발식 분리장치를 제안하였다. 성능을 검증하기 위하여 분리시간, 분리가 가능한 사전하중, 분리장치 작동 시 충격량 측정 실험을 수행하였다.

• International Journal of Aeronautical and Space Sciences
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• 제11권2호
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• pp.87-97
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• 2010

A fault tolerant satellite attitude control scheme with a modified iterative learning law is proposed for dealing with actuator faults. The actuator fault is modeled to reflect the degradation of actuation effectiveness, and the solar array-induced disturbance is considered as an external disturbance. To estimate the magnitudes of the actuator fault and the external disturbance, a modified iterative learning law using only the information associated with the state error is applied. Stability analysis is performed to obtain the gain matrices of the modified iterative learning law using the Lyapunov theorem. The proposed fault tolerant control scheme is applied to the rest-to-rest maneuver of a large satellite system, and numerical simulations are performed to verify the performance of the proposed scheme.

• 한국항행학회논문지
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• 제16권5호
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• pp.731-737
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• 2012

새로운 개념의 인공위성 자세제어 작동기에 대한 타당성 연구를 수행하였다. 구체구동기는 단일장치로써 위성의 3축 자세제어가 가능한 구동기이며, 구체 플라이휠과 자기부상 및 회전구동을 위한 전자석으로 구성된다. 구체구동기에 대한 수학적 모델링 및 설계를 통하여 시제품을 제작하였으며, 자기부상이 적용된 조건에서 1축에 대한 구동성능 시험을 수행하였다. 구동성능은 최대속도 7,200rpm 그리고 최대토크 0.7Nm로 측정되었으며, 속도-토크 특성곡선을 이용한 개루프 속도제어를 통하여 우수한 가속 및 감속 속도제어 결과를 확인하였다. 본 구체구동기는 속도 및 토크 제어를 위한 추가적인 연구를 통하여 성능이 개선될 예정이다.

• 한국전산유체공학회지
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• 제10권2호
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• pp.48-53
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• 2005

This work discusses the numerical analysis, the design and experimental test of the SMA actuator along with its capabilities and limitations. Convective heating and cooling using water actuate the SMA(Shape memory alloy) element of the actuator. The fuel such as propane, having a high energy density, is used as the energy source for the SMA actuator in order to increase power and energy density of the system, and thus in order to obviate the need for electrical power supplies such as batteries. The system is composed of a pump, valves, bellows, a heater(burner), control unit and a displacement amplification device. The experimental test of the SMA actuator system results in 150 MPa stress(force : 1560 N) with $3\%$ strain and 0.5 Hz. actuation frequency. The actuation frequency is compared with the prediction obtained from numerical analysis. For the designed SMA actuator system, the results of numerical analysis were utilized in determining design parameters and operating conditions.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.183-187
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• 2012

In the present study, a feasibility study on an innovative satellite attitude control actuator is performed. The actuator is specially designed to generate the reaction torque in an arbitrary axis, so that a satellite attitude can be controlled by using itself. It consists of a spherical flywheel and electromagnets for levitation and rotation control of the ball. As the earlier study, a rotating performance test on the spherical actuator is conducted in a single rotating axis and vertical levitation condition. From the test results, it can be confirmed that the maximum speed and torque of the innovative device are 7,200rpm and 0.7Nm, respectively. Using torque-voltage characteristics of the spherical motor, an open-loop control (V/f constant control) is performed, and the test results show excellent control performance in acceleration and deceleration phases.

• Transactions on Control, Automation and Systems Engineering
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• 제4권2호
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• pp.169-175
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• 2002

A sliding mode control of spacecraft attitude tracking with actuator, especially reaction wheel, is presented. The sliding mode controller is derived based on quaternion parameterization for the kinematic equations of motion. The reaction wheel dynamic equations represented by wheel input voltage are presented. The input voltage to wheel is calculated from the sliding mode controller and reaction wheel dynamics. The global asymptotic stability is shown using a Lyapunov analysis. In addition the robustness analysis is performed for nonlinear system with parameter variations and disturbances. It is shown that the controller ensures control objectives for the spacecraft with reaction wheels.

• 한국항공우주학회지
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• 제37권5호
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• pp.457-463
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• 2009

본 논문에서는 위성 본체에 장착된 태양 전지 패널을 위성으로부터 분리하기 위한 새로운 개념의 비폭발식 분리 메커니즘을 제안하였으며, 구동기로서 형상기억합금을 이용한 스프링 형상의 구동기를 채택하였다. 먼저 제안된 분리 메커니즘을 구동하기 위해서 필요한 구동력을 측정하였으며, 구동하기에 적절한 구동기를 제작하기 위하여 이론적 계산을 통하여 스프링 형상의 형상기억합금 구동기를 설계/제작 하였다. 최종적으로 분리 메커니즘과 형상기억합금 구동기를 통합하고 분리 장치의 반응속도시험, 사전 하중(Preload) 시험, 충격시험을 통하여 검증하였다. 상기한 소형위성용 비폭발식 저충격 분리장치 개발을 통하여 그동안 사용되었던 선진국의 폭발식 분리장치를 대체할 수 있는 위성 부품의 국산화에 계기를 마련하고자 한다.

• 우주기술과 응용
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• 제3권4호
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• pp.322-332
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• 2023

Satellite attitude-control actuators are equipped with a reaction wheel for three-axis attitude control. The reaction wheel rotates a motor inside the actuator to generate torque in the vector direction. When using the reaction wheel, there are restrictions on the torque values generated as the motor rotates. The torque value of the reaction wheels mounted on small satellites is approximately 10 mNm, and high values are not used. Therefore, three-axis attitude control of a small satellite is possible using a reaction wheel, but this method is not suitable for missions that require rapid attitude control at a specific time. As a technology to overcome the small torque value of the reaction wheel, the control moment gyro (CMG) is currently in wide use as a rapid attitude-control actuator in space satellites. The CMG has an internal gimbal mounted at a right angle to the rotation motor and generates a large torque value. In general, when the gimbal operates, a torque value approximately 100 times greater is generated, making it suitable for rapid posture maneuvering. Currently, we are developing a technology for mounting a controlled moment gyro on a small satellite, and here we share the development status of an 800 mNm CMG.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1641-1644
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• 2005

Magnetic actuation utilizes the mechanic torque that is the result of interaction of the current in a coil with an external magnetic field. A main obstacle is, however, that torques can only be produced perpendicular to the magnetic field. In addition, there is uncertainty in the Earth magnetic field models due to the complicated dynamic nature of the field. Also, the magnetic hardware and the spacecraft can interact, causing both to behave in undesirable ways. This actuation principle has been a topic of research since earliest satellites were launched. Earlier magnetic control has been applied for nutation damping for gravity gradient stabilized satellites, and for velocity decrease for satellites without appendages. The three axes of a micro-satellite can be stabilized by using an electromagnetic actuator which is rigidly mounted on the structure of the satellite. The actuator consists of three mutually-orthogonal air-cored coils on the skin of the satellite. The coils are excited so that the orbital frame magnetic field and body frame magnetic field coincides i.e. to make the Euler angles to zero. This can be done using a Neural Network controller trained by PD controller data and driven by the difference between the orbital and body frame magnetic fields.

• 한국항공우주학회지
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• 제37권4호
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• pp.399-405
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• 2009

위성 카메라를 위한 초점면부 영상 안정화 장치는 영상이 맺히는 초점면부의 운동외란을 제거함으로써 위성 카메라의 영상 품질을 향상 시킬 수 있는 효율적인 방법 중 하나이다. 본 연구의 목적은 초점면부 안정화 기법을 소개하고 초점면부 영상 안정화 장치 액츄에이터의 응답 및 추력에 대한 최적의 구동 조건을 결정하는 것이다. 이를 위해 다양한 구동 조건에 따른 영상화 안정화 장치의 마찰 구동형 압전 액츄에이터의 응답성과 추력을 실험적으로 조사하였다. 실험결과로부터 마그네슘 슬라이더에 대한 최적의 구동 주파수는 70 kHz, 듀티비는 27% 였다.