• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.793-798
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• 1993

In this study the attitude control of the KOREASAT is investigated. The KOREASAT is a geostationary satellite and its 3 attitude angles, namely, roll, pitch and yaw angles, are stabilized by using the 3-axis stabilization technique. In the pitch control loop, the pitch attitude angle received from the earth sensor is processed in the attitude processing electronics by using PI type control logic, and the control command is sent to the momentum wheel assembly to generate the control torque by varying the wheel rate. The roll/yaw attitude control is performed by activating a magnetic torquer or by firing appropriate thrusters. The magnetic torquer interacts with the earth magnetic field to produce the control torque, and the thrusters are used to control the larger roll attitude errors. In this study dynamic modelling of the satellite is performed. And the earth sensor, the momentum wheel, and the magnetic torquer are mathematically modelled. The 3-axis attitude control logic is implemented to make the closed-loop system and simulations are carried out to verify the implemented control laws.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.26 no.3
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• pp.48-54
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• 2018

This paper deals with a development of a quad-rotor for a hovering attitude control. First, a rotational dynamics are derived to design an attitude controller. The attitude controller is based on PI (Proportional-Integral) controller. For a stable attitude control, an anti-windup method applies to the PI attitude controller. Additionally, a complementary filter is used to obtain more reliable attitude. Gain values of the attitude controllers based on the anti-windup method are obtained through tests. Finally, the quad-rotor with the anti-windup based PI attitude controller is developed and a hovering attitude control flight tests are performed. As a result, the developed quad-rotor is capable of stable hovering.

• Journal of Astronomy and Space Sciences
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• v.30 no.1
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• pp.1-10
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• 2013

An integrated orbit and attitude control algorithm for satellite formation flying was developed, and an integrated orbit and attitude software-in-the-loop (SIL) simulator was also developed to test and verify the integrated control algorithm. The integrated algorithm includes state-dependent Riccati equation (SDRE) control algorithm and PD feedback control algorithm as orbit and attitude controller respectively and configures the two algorithms with an integrating effect. The integrated SIL simulator largely comprises an orbit SIL simulator for orbit determination and control, and attitude SIL simulator for attitude determination and control. The two SIL simulators were designed considering the performance and characteristics of related hardware-in-the-loop (HIL) simulators and were combined into the integrated SIL simulator. To verify the developed integrated SIL simulator with the integrated control algorithm, an orbit simulation and integrated orbit and attitude simulation were performed for a formation reconfiguration scenario using the orbit SIL simulator and the integrated SIL simulator, respectively. Then, the two simulation results were compared and analyzed with each other. As a result, the user satellite in both simulations achieved successful formation reconfiguration, and the results of the integrated simulation were closer to those of actual satellite than the orbit simulation. The integrated orbit and attitude control algorithm verified in this study enables us to perform more realistic orbit control for satellite formation flying. In addition, the integrated orbit and attitude SIL simulator is able to provide the environment of easy test and verification not only for the existing diverse orbit or attitude control algorithms but also for integrated orbit and attitude control algorithms.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1747-1753
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• 2004

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.

• Journal of Mechanical Science and Technology
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• v.18 no.2
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• pp.203-210
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• 2004

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.

• Journal of Astronomy and Space Sciences
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• v.13 no.2
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• pp.67-81
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• 1996

The attitude dynamics of KITSAT-1 are modeled including the gravity gradient stabilization method. We define the operation scenario during the initial attitude stabilization period by means of a magnetorquering control algorithm. The required constraints for the gravity gradient boom deployment are also examined. Attitude dynamics model and control laws are verified by analyzing in-orbit attitude sensor telemetry data.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.799-804
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• 1993

In this paper, the scheme of combining the orbit correction and attitude control of a 3-axis stabilized satellite is suggested. Being coupled and complimentary, it is preferable to achieve the required orbit correction and the desired attitude control simultaneously. A solution of the probes simultaneous control of orbit correction and attitude of a satellite, is obtained by solving the two point boundary value problem numerically. The first-order gradient algorithm is used to solve the numerical problem. The simulation results show that the East-West station keeping process with the combined system of an orbit correction and an attitude control is satisfactory.

• International Journal of Aeronautical and Space Sciences
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• v.11 no.4
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• pp.303-312
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• 2010

This paper introduces the upper stage attitude control system of KSLV-I, which is the first space launch vehicle in Korea. The KSLV-I upper stage attitude control system consists of two electro-hydraulic actuators and a reaction control system using cold nitrogen gas. A proportional, derivative, and integral controller is designed for the electro-hydraulic thrust vectoring system, and Schmidt trigger ON/OFF controllers are designed for the reaction control system. Each attitude controller is designed to have enough stability margins. The stability and performance of KSLV-I upper stage attitude control system is verified via hardware in the loop tests. Hardware in the loop tests are accomplished for perturbed flight conditions as well as nominal flight condition. The test results show that the attitude control loop of KSLV-I upper stage is very stable and the attitude controllers perform well for all flight conditions. Attitude controllers designed in this paper have been successfully applied to the first flight of KSLV-I on August 25, 2009. The flight test results show that all attitude controllers of the KSLV-I upper stage performed well and satisfied the accuracy specifications even during abnormal flight conditions.

• 제어로봇시스템학회:학술대회논문집
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• 1995.10a
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• pp.368-371
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• 1995

This paper describes dynamic analysis and attitude control of a large spacecraft with flexible appendages in gravitational field. The effect of attitude control and vibration control of flexible appendages in gravitational field has been clarified. We demonstrate some simulations in gravitational field for some cases, and suggest the effects of gravitational torque, parameters of flexible appendages, attitude control and vibration control of flexible appendages.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.561-565
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• 2008

Generally, reaction wheels or thrusters are used for attitude control of a satellite. There is a potential method for the attitude control utilizing the plasma flow on the Low Earth Orbit. In the present study, experiments which simulate attitude control of a Low Earth Orbit Satellite using the ionosphere were conducted. In this experiment, a plasma flow was generated by a steady-state Hall type accelerator. However it is known that the Hall type accelerator, which is used as plasma source, produces a torque around its axis called "swirl torque". This torque would affect the attitude control in the above-mentioned experiments. First of all, we conducted the measurement of the swirl torque. Secondly, experiments using a satellite model with negative electrodes were conducted. The negative electrodes generated torque around the axis, and controlled the attitude of the satellite model by changing the applied voltage.