• 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.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1239-1244
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• 2004

Precise positioning is an important problem facing motion control systems which usually use electric motor. A motor possesses a nonlinear property which degrades the positioning accuracy. Therefore, a compensator which linearizes the relationship between the angular velocity and input signal of the motor is required to enable precise positioning. In this paper, the design of a Model Reference Adaptive Control System (MRACS) for realizing the precise positioning for a system using a motor including the nonlinear property is described. The designed MRACS is applied to the attitude control problem on a satellite using a DC servomotor to drive its reaction wheel. Experimental results demonstrate the validity of a proposed control method for a positioning control system with an electric motor.

• Korean Journal of Computational Design and Engineering
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• v.20 no.3
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• pp.230-237
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• 2015

Soil deformation on the off-load ground is significantly affected by soil conditions, such as soil type, water content, and etc. Thus, the soil characteristics should be estimated for predicting vehicle movements on the off-load conditions. The plate-sinkage test, a widely-used experimental test for predicting the wheel-soil interaction, provides the soil characteristic parameters from the relationship between soil stress and plate sinkage. In this study, soil stress under the plate-sinkage situation is calculated by the DEM (Discrete Element Method) model. We developed a virtual soil bin with DEM to obtain the vertical reaction forces under the plate pressing the soil surface. Also parametric studies to investigate effects of DEM model parameters, such as, particle density, Young's modulus, dynamic friction, rolling friction, and adhesion, on the characteristic soil parameters were performed.

• Journal of KSNVE
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• v.7 no.3
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• pp.387-392
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• 1997

This paper concerns a SCARA robot with the flexible forearm linked to the rigid upper arm. The equations of motion are derived by the Lagrangian mechanics. For controller design, the perturbation approach is taken to separate the original equations of motion into linear equations describing small perturbed motions and nonlinear equations describing purely rigid motion of the robot. To effect the desired payload motion, open loop control inputs are determined based on the inverse dynamics of the latter. In order to reduce the positional error during maneuver, an active vibration suppression is done. To this end, a feedback control is designed for robustness against disturbance on the basis of the linear equations and the LQR theory modified to have a prescribed degree of stability. The proposed control scheme shows satisfactory performances in experiments as well as in numerical simulations.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.7
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• pp.695-700
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• 2014

In this paper, we utilize the CMG's momentum bias to control the roll/pitch attitude of the Quad-rotor. While the previous control approaches have used the thrust control approach, we design and add a new momentum controller (using CMG) in order to improve the transient response over the existing methods. The focal point of this paper is the design of a controller for a Quad-rotor's attitude using CMG. This leads to other tasks such as an identification of the model's parameters and mathematical nonlinear modeling. Then, the previous thrust controller is designed based on the linearized model. Finally, the overall system with our designed controller is implemented and tested in real time to show that the Quad-rotor is kept in a good balanced position faster than the traditional thrust-only control approach.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.749-752
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• 1996

A computer program was developed for the static analusis of a bridge expansion joint mechanism, which is called lazy-tong joint. I t was modelled as a plane truss and statically determinate structure under the assumption of small expansion in bridge girder. The applied load was assumed as a maxium wheel load exerted by a 40th tandem axied tractor-semitrailer truck. By using the developed computer program, reaction forces, axial and bending stresses, deflections, and critical buckling load, etc. of each structural member were analyzed. And they showed good agreement with those analyzed by the comercial F.E.M S/W, ANSYS.

• Journal of Mechanical Science and Technology
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• v.17 no.12
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• pp.1912-1921
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• 2003

This paper presents a global mode modeling of space structures and a control scheme from the practical point of view. Since the size of the satellite has become bigger and the accuracy of attitude control more strictly required, it is necessary to consider the structural flexibility of the spacecraft. Although it is well known that the finite element (FE) model can accurately model the flexibility of the satellite, there are associated problems : FE model has the system matrix with high order and does not provide any physical insights, and is available only after all structural features have been decided. Therefore, it is almost impossible to design attitude and orbit controller using FE model unless the structural features are in place. In order to deal with this problem, the control design scheme with the global mode (GM) model is suggested. This paper describes a flexible structure modeling and three-axis controller design process and demonstrates the adequate performance of the design with respect to the maneuverability by applying it to a large flexible spacecraft model.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.30-30
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• 2000

In the three axis control of satellite by using reaction wheel and gyro, a Gyro carries out measuring of the attitude angie and the attitude angular velocity. The Gyro is operated by the electronic part and the mechanic actuator. The digital part of the electronic part is consisted of the FPGA (Field Programmable Gate Array), which is one of the methods for designing VLSI (Very Large Scale Integrated Circuit), and the mechanic actuator processes the input/output data by the dynamic model. In the research of the mixed mode of Gyro, the simulation is accomplished by SABER of the mixed mode simulator and the results for the practical implementation of the satellite ACS (Attitude Control System) interfaced with the data processing are proposed.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.342-342
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• 2000

We present 3-axis stabilized spacecraft attitude determination algorithm using the magnetometer. The magnetometer has been used as a reliable, light-weight and inexpensive sensor in attitude determination and reaction wheel momentum dumping system. Recent studies have attempted to use the magnetometer when other attitude sensor, such as star tracker, fails. The differences between the measured and computed the Earth's magnetic field components are spacecraft attitude errors. In this paper, we propose extended Kalman filter(EKF) to determine spacecraft attitude with the magnetometer data and gyro-measured body rates. We develop and simulate this algorithm using MATLAB/SIMULINK. This algorithm can be used as a backup attitude determination system.

• Journal of Astronomy and Space Sciences
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• v.17 no.2
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• pp.309-316
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• 2000

KOMPSAT-2 will carry MSC(Multi-Spectral Camera) which provides 1m resolution panchromatic and 4m resolution multi-spectral images at the altitude of 685km sun-synchronous mission orbit. The mission operation of KOMSPAT-2 is to provide the earth observation using MSC with nadir pointing. KOMPSAT-2 will also have the capability of roll/pitch tilt maneuver using reaction wheel of satellite as required. In order to protect MSC from thermal distortion as well as direct sunlight, MSC shall be operated within the constraint of sun incidence angle. It is expected that the sunlight will not violate the constraint of sun incidence angle for normal mission operations without roll/pitch maneuver. However, during roll/pitch tilt operations, optical module of MSC may be damaged by the sunlight. This study analyzed sun incidence angle of payload using KOMPSAT-2 AOCS (Attitude and Orbit Control Subsystem) Design and Performance Analysis Soft ware for KOMPSAT-2 normal mission operations.