• Aerospace Engineering and Technology
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• v.13 no.2
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• pp.18-28
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• 2014

We assume that two control moment gyros are installed for space qualification in a satellite with four reaction wheels, and study the high agile maneuver method. Using high torque control moment gyros, we reduce the satellite's attitude error. After that, we activate reaction wheels to control remaining attitude error. This proposed method can avoid singularity problem of control moment gyros, and do not require gimbals' angle to calculate torque command. Through numerical simulations, we show that our method's agile performance is similar to previous method and reduce the reaction wheels' required momentum.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.10
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• pp.821-828
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• 2021

Quadrotors relatively smaller and lighter than other aircraft have a disadvantage of being sensitive to the external disturbances. In order to solve this disadvantage, many studies have been conducted by various control techniques robust to disturbances. In this paper, CMGs (Control Moment Gyros) introducing relatively large control torque with an identical amount of electric powers are applied to cancel the external disturbances. Two CMGs are considered to control the attitude of quadrotors so that a multi-copter installed with two CMGs and four rotors are introduced for this work. Finally, to verify the control performance of the proposed system by the CMGs, a numerical simulation conducted in the given harsh environment.

• International Journal of Aeronautical and Space Sciences
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• v.7 no.2
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• pp.14-25
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• 2006

This paper is focused on designing an implementable control law to perform spacecraft various missions using momentum exchange devices such as reaction wheels(RWs) and control moment gyros(CMGs). A compact equation of motion of a spacecraft installed with various momentum exchange devices is derived in this paper. A hybrid control law is proposed for precision attitude control of agile spacecraft. The control law proposed in this paper allocates control torque to the CMGs and the RWs adequately to satisfy the precision attitude control and large angle maneuver simultaneously. The saturation problem of reaction wheels and the singularity problem of control moment gyros are considered. The problems are successfully resolved by using the proposed hybrid closed loop control law. Finally, the proposed hybrid control law is demonstrated by numerical simulations.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.11
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• pp.1027-1033
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• 2015

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.

• 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.

• 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.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.180-185
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• 2009

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. In this research, mechanical system of the CMG is designed and the main components of CMG are producted.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.2
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• pp.107-119
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• 2013

We study three axis attitude control method including two axis high agile maneuver using four reaction wheels and two control moment gyros. We investigate singularity conditions due to two control moment gyros and propose singularity escape method. Based on this, we propose actuator control algorithm for high agile maneuver. Also, we propose actuator momentum management method which preserves momentum of reaction wheels and control moment gyroscopes before and after satellite attitude control. Through numerical simulation, we show that our method achieves three axis attitude control including two axis high agile maneuver and preserves actuators' momentum.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.1
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• pp.48-56
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• 2008

Nowadays, CMG(Control Moment Gyros) becomes one of the essential actuators for satellite attitude control. The method to define the key requirements of CMG is suggested to avoid CMG's singularity problem for the limited envelope of angular momentum of 2H. Furthermore, the analysis and simulation are carried out to provide a necessary guideline when three CMGs are used for spacecraft control purpose. An improved configuration of redundant four CMG cluster, slightly different from the conventional configuration, is proposed not only to avoid the CMG singularity problem, but to improve agility about roll or pitch-axis.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.10
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• pp.935-945
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• 2011

We study X-axis or Y-axis high agile attitude control method, using four reaction wheels and two control moment gyros. Since normal satellites use same actuators, researchers design an attitude controller first, and then allocate torque commands to each actuator. However, our satellite uses both control moment gyros and reaction wheels, whose torque output differences are very large. Therefore, we cannot apply normal attitude controller design procedure. In this paper, we solve this problem by combining actuator torque command and attitude controller. Through numerical simulations, we show that our method enables satellite high agility.