• Journal of Aerospace System Engineering
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• v.12 no.1
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• pp.17-26
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• 2018

The interaction model between variable-speed control moment gyros and a satellite has been studied based on the multi-body dynamics. Using the interaction model, we could obtain data for the design of VCMG motors and the strength design of structure. The interaction effects of flexible modules such as solar panels were included. Flexible modes are excited by the satellite's maneuver, and these modes cause perturbations in the satellite attitude. We developed a simulation program by Modelica and verified the proposed model.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.11
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• pp.861-871
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• 2020

Raising the speed of the momentum wheel in the CMG increases the unintended force and torque caused by mass imbalance. This unintended force and torque should be minimized to get the better quality of satellite SAR image because they lead to the vibration of the output image. This paper shows the works on compensating the static imbalance and couple mass imbalance in the CMG wheel. First, the force and torque at the center of mass generated by the mass imbalance were predicted through M&S analysis. Second, the force and torque were estimated similarly through the M&S analysis when the measurement point was moved from the rotation center. Third, the measurement configuration for the force and torque by the mass imbalance was described. Fourth, the change of the force and torque by adding the specified mass to the momentum wheel was observed after comparing the measurements with the results of the M&S. And finally, the effect of the compensation was analyzed by comparing the force and torque before and after the correction while 24Nm class CMG was running in the standby mode.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.7
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• pp.640-646
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• 2007

Actuator-induced disturbance is one of the crucial factors of spacecraft attitude pointing and stability in fine attitude control problems. The control moment gyros (CMGs) are known as very attractive actuators from the point of high power and low weight. In order to develop a CMG as an actuator for fine controls, CMG-induced disturbances should be analyzed. Therefore, this paper aims to develop an analytic model and predict the effect of disturbances of CMGs by assuming static and dynamic imbalances. The proposed model is induced by the Lagrangian method on the basis of the small signal assumption.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.2
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• pp.172-178
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• 2015

The control moment gyroscope(CMG) which is well known as an effective high-torque-generating device is applicable to space vehicles, airplanes, ships, automobiles, robotics, etc. for attitude stabilization and maneuver. This paper deals with the overall details of 100Nm-class CMG development for various industrial applications, and provides the activities and results associated with the CMG system-level requirement analysis, the motor subsystem design/manufacturing/integration, the construction of ground support equipment, and the performance test and evaluation. The performance test reveals that the CMG generates the torque output more than 120Nm in as-designed operation of spin motor and gimbal motor.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.6
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• pp.413-422
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• 2022

In this paper, the fault analysis of the momentum wheel, which is a high-speed rotary machinery of 'Control Moment Gyro' for medium and large satellite, was described. For fault diagnosis, envelope spectrum analysis was performed using Hilbert transformation method and signal demodulation method to find the impact signals periodically generated from amplitude modulated signals. Through this, the fault of the momentum wheel was diagnosed by analyzing whether there was a harmonic component of the rotational frequency and a bearing fault frequency in a specific frequency band with a high peak.

• Journal of Aerospace System Engineering
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• v.13 no.2
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• pp.26-33
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• 2019

Control moment gyro (CMG) employed as satellite actuators, generates a large torque through the steering of its gimbals. Although each gimbal holds a high-speed rotating wheel, the wheel imbalances induces disturbance and degrades the satellite control quality. Therefore, the disturbances ought to be detected and identified as a precaution against actuator faults. Among the method used in detecting disturbances is the state observers. In this paper, we apply a continuous second order sliding mode observer to detect single disturbances/faults in CMGs. Verification of the algorithm is also done on the hardware satellite simulator where four CMGs are installed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.2
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• pp.129-138
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• 2021

Due to the active progress in space programs for various types of ground and space missions, the high agile spacecraft maneuverability is also required. To meet the requirement of the given space missions, the Control Moment Gyros (CMG) for the alternatives of the classical reaction wheels can release the attitude maneuverability restrictions. In addition, the angular rates of the spacecraft is constrained due to the limited actuator characteristics. In this paper, a sliding mode control technique for the attitude control of the spacecraft equipped with the pyramid type of CSCMG(Constant Speed CMG) is designed, and the stability of the control system is guaranteed by using the Lyapunov stability theory. Finally, the control law proposed is analyized by numertical simulations.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.111-111
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• 2004

회전축계는 발전기의 터빈이나 가스터빈 그리고 항공기의 회전익, 선박, 자동차등 산업전반에 널리 사용되어지고 있다. 이러한 회전축계의 안정성 확보와 성능향상을 위해서는 정확한 동적 모델링이 필요하며 지금까지 많은 연구가 되어 왔다. 일반적으로 회전축계의 동특성 이론 모델은 회전관성, 자이로모멘트, 전단변형을 포함하는 티모센코 축 요소를 널리 사용하고 있으며, 많은 연구를 통해 그 유용성이 입증되어 왔다.(중략)

• Journal of the Korean Institute of Intelligent Systems
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• v.27 no.2
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• pp.89-98
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• 2017

The control moment gyroscope(CMG) can be used for essential balancing control of a one-wheeled mobile robot. A single-gimbal CMG has a simple structure and can supply strong restoring torque against external disturbances. However, the CMG generates unwanted directional torque also besides the restoring torque; the unwanted directional torque causes instability in the one-wheeled robot control system that has high rotational degrees of freedom. This study proposes a control system for a one-wheeled mobile robot by using a CMG scissored pair to eliminate the unwanted directional torque. The well-known LQR control algorithm is designed for robustness against modeling error in the dynamic motion equations of a one-wheeled robot. Computer simulations for 3D nonlinear dynamic equations are carried out to verify the proposed control system with the CMG scissored pair and the LQR control algorithms.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.11
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• pp.952-960
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• 2018

Recently, lots of remote sensing satellite require agility to collect more images within the limited time frame. To satisfy this kind of mission requirement, high torque actuator such as CMG is an essential element. In this study, 5Nm class small CMG developed by KARI is introduced to implement for an agile small satellite design. One of the singularity escape CMG steering law, Designated Direction Escape (DDE) method, which is a sort of modified version of Singular Direction Avoidance (SDA) method is summarized for its application on the numerical simulation of agile attitude control system design result. The performance of DDE method is demonstrated properly by escaping well known elliptic internal singularity successfully. 5Nm class small CMG cluster in a pyramid type as well as a roof type configuration is utilized to perform the numerical simulation and to demonstrate its agility design result for a small satellite. Simulation result shows the properness of 5Nm small CMG to a small agile satellite system. Also, the simulation result provides some valuable information that is important to CMG hardware design and manufacturing.