• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.10
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• pp.853-861
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• 2012

This paper considers one of the explicit guidance algorithms, which has been proposed by Jaggers, to determine the closed-loop guidance algorithm for upper stages of a 3-staged space launch vehicle. Its commanded thrust vector is closer to the optimal solution when compared with that obtained by using the well-known Powered Explicit Guidance (PEG), which has been developed through the Space Shuttle program. Its performance is evaluated here by applying for guidance of the launcher during the second and third stages. Furthermore, to generate more precise guidance commands, it is attempted not to use the approximate formulas for the derivation of the original guidance law, and it is shown that performance is improved in comparison with the original.

• Aerospace Engineering and Technology
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• v.10 no.1
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• pp.89-97
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• 2011

This paper considers improved IGM (Iterative Guidance Mode), one of the explicit guidance algorithms, to determine the guidance algorithm for upper stages of a space launch vehicle. IGM, which has been employed successfully for the Saturn to put its payload into the parking orbit and lunar transfer orbit, is applied here for guidance of the launcher during the second and third stages. The orbit injection accuracy is evaluated through the 3-DOF computer simulations and an accurate prediction method, which can eliminate the prediction error of the downrange position at the orbit injection, is also proposed here.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.10
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• pp.709-716
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• 2022

In this paper the Gamma guidance law, which was used for IUS (Inertial Upper Stage), is applied for solid-motor guidance of a upper stage of a satellite launch vehicle. The RCS (Reaction Control System), which activates after burnout of the upper stage, is employed for the convergence of the guidance algorithm and compensation of velocity errors induced by the solid motor. The algorithm is also simplified by replacing the time-consuming numerical integration process to predict final vehicle states with Keplerian trajectories. The performance of the algorithm is evaluated by conducting 3-DOF computer simulations for off-nominal flight conditions. The numerical results show that Gamma guidance can reduce the orbit injection accuracy in comparison with that obtained by applying open-loop commands.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.9
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• pp.874-883
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• 2008

This study considers powered explicit guidance, one of the closed-loop guidance laws for satellite launch vehicles. The guidance algorithm employed here does not include the iterative procedure of the original algorithm. Also, the single-target algorithm to treat the general time-varying thrust profiles is described. The computer simulations for the 6-DOF launch vehicle model are performed to investigate the orbit injection accuracy of the guidance algorithm in the nominal/off-nominal flight conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.12
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• pp.981-988
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• 2021

This paper presents a decentralized guidance algorithm for swarm flight of fixed-wing UAVs (Unmanned Aerial Vehicles). Considering swarm flight missions, we assume four representative swarm tasks: gathering, loitering, waypoint/path following, and individual task. Those tasks require several distinct maneuvers such as path following, flocking, and collision avoidance. In order to deal with the required maneuvers, this paper proposes an integrated guidance algorithm based on vector field, augmented Cucker-Smale model, and potential field methods. Integrated guidance command is synthesized with heuristic weights designed for each guidance method. The proposed algorithm is verified through flight tests using up to 19 small fixed-wing UAVs.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.69-72
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• 2000

본 논문에서는 부밴드에서의 수렴 성능 향상을 위하여 새로운 블록 LMS 알고리듬과 부밴드 각 적응필터에 가변 적응이득을 사용하는 가변 적응이득 블록 LMS 알고리듬을 제안한다. 이들 알고리듬들을 유도하기 위해 새로운 비용함수를 제안하며, 유도된 비용함수는 적응 필터 계수에 대해 2차 형식인 특징을 가진다. 제안한 알고리듬의 수렴 성능을 평가하기 위하여 부밴드 LMS 알고리듬과 가변 적응이득 알고리듬을 컴퓨터 모의 실험을 통해 비교함으로서 성능의 우수성을 입증하였다.

• Aerospace Engineering and Technology
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• v.11 no.1
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• pp.169-177
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• 2012

This paper considers the explicit guidance algorithm to determine the closed-loop guidance law applicable to upper stages of a given space launch vehicle. It has the advantage of very simple forms derived from the flat earth assumption, which is appropriate for its on-board application. However the simple time-to-go prediction equation produces the degraded guidance performance of the launcher because of its inaccuracy. To overcome the problem, the elaborate prediction equations, which have been employed in Saturn and H-II, are attempted here. Finally, the simulation results show that the simple guidance approach requires the more accurate time-to-go prediction and gravity integrals for its broad application.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.3
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• pp.221-228
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• 2014

In this paper, the operational concept and the navigation algorithms for the gliding guided artillery munition are studied. The gliding guided artillery munition has wings for gliding; therefore spin of the munition should be eliminated. The previous navigation algorithms assumed a spinning munition with constant angular velocity; hence, they cannot be applied for the gliding munition. Moreover, lateral stability becomes worse due to decrease of angular momentum. Therefore, side force should be controlled to improve the stability, and the munition should maneuver, then the previous navigation algorithms for typical fixed-wing aircraft cannot be applied. In this paper, we apply the previous navigation algorithms for the spinning munition. Spin is eliminated and wings are deployed based on the estimation results, and the advanced navigation algorithm for the non-spinning munition is introduced.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.579-589
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• 2002

In this paper, a Wittrick-Williams algorithm is developed for the spectral element model of an elastic-piezoelectric two-layer active beam. This algorithm may help calculate all the required natural frequencies, which lie below any chosen frequency, without the possibility of missing any due to close grouping or due to the abrupt sign changes of the determinant of spectral element matrix via infinity instead of via zero. A uniform active beam and a partially patched active beam are considered as the illustrative examples to confirm the present algorithm.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.6
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• pp.72-80
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• 2004

In this paper, the design procedure of a guidance algorithm in the boosting phase of missiles with free-flight after thrust cut-off is introduced. The purpose of the guidance is to achieve a required velocity vector at the thrust cut-off. Trajectory optimizations for four cost functions are performed to investigate implementable trajectories in the pitch plane. It is observed from the optimization results that high angle of attack maneuver in the beginning of the flight are required to satisfy the constraints. The proposed guidance algorithm consists of the pitch program to produce open-loop pitch attitude command and the yaw attitude command generator to nullify the velocity to go. The pitch program utilizes the pitch attitude histories obtained from the trajectory optimization.