• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.361-364
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• 1997

The re-enty guidance design involves trajectory optimization, generation of a reference drag acceleration profile with the satisfaction of trajectory constraints. This reference drag acceleration profile can be considered as the reference trajectory. This paper proposes the atmospheric re-entry system which is composed of longitudinal, later and range control. This paper shows the a performance of a re-entry guidance and control system using feedback linearization control and predictive control.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.6
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• pp.111-118
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• 2000

The design of reference trajectory with respect to drag acceleration is necessary to decelerate from hypersonic speed safely after atmosphere re-entry of space vehicle. The re-entry guidance design involves trajectory optimization, generation of a reference drag acceleration profile with the satisfaction of 6 trajectory constraints during the re-entry flight. This reference drag acceleration profile can be considered as the reference trajectory. The cost function is composed of the accumulated total heating on vehicle due to the reduction of weight. And a regularization is needed to prevent optimal drag profile from varying too fast and achieve realized trajectory. This paper shows the relations between velocity, drag acceleration and altitude in drag acceleration profile, and how to determine the reference trajectory.

• Journal of Mechanical Science and Technology
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• v.20 no.10
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• pp.1557-1566
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• 2006

We present a procedure for the application of global orthogonal polynomial into an atmospheric re-entry maneuvering problem. This trajectory optimization is imbedded in a family of canonically parameterized optimal control problem. The optimal control problem is transcribed to nonlinear programming via global orthogonal polynomial and is solved a sparse nonlinear optimization algorithm. We analyze the optimal trajectories with respect to the performance of re-entry maneuver.

• Journal of Power System Engineering
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• v.7 no.4
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• pp.67-73
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• 2003

The entry guidance design involves trajectory optimization and generation of a drag acceleration profile as the satisfaction of trajectory conditions during the entry flight. The reference trajectory is parameterized and optimized as piecewise linear functions of the velocity. A regularization technique is employed to achieve desired properties of the optimal drag profile. The regularized problem has smoothness properties and the minimization of performance index then prevents the drag acceleration from varying too fast, thus eliminating discontinuities. This paper shows the trajectory control using the simple control law as well as the information of reference drag acceleration.

• Journal of Mechanical Science and Technology
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• v.16 no.6
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• pp.745-756
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• 2002

The re-entry problem consists of guidance design and trajectory control. This paper summarizes the detailed relationships between the velocity, drag acceleration and altitude in determining reference trajectories. The computational issues are also addressed, and the performance of the proposed simple nonlinear control of a bank angle for the longitudinal/ lateral trajectory is demonstrated. In particular, the fixed bank angle methods that can reduce the drag acceleration errors at low-speeds are proposed. The importance of bank reversals with respect to the azimuth errors Is also elucidated.

• Journal of Mechanical Science and Technology
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• v.18 no.9
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• pp.1519-1528
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• 2004

Atmospheric Re-Entry guidance is divided as longitudinal and lateral. This paper proposes a longitudinal reference trajectory and control law using the inverse dynamics method with pseudospectral Legendre method. Application of this method into Re-Entry problem forces a power of calculation time-reduction due to unnecessary of integration or any iteration as well as sufficient accuracy convergence. The used guidance scheme is time-to-go.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.2
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• pp.150-159
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• 2010

The approach and landing phase of a re-entry vehicle is composed of Steep Glideslope phase, Circular Flare phase, Flare Maneuver phase. The trajectory planning algorithm with geometric parameters is studied in this paper for on-board trajectory planning. This algorithm generate reference trajectory rapidly considering safe landing of re-entry vehicle. In this paper, the Mamdani Fuzzy PD type controller for longitudinal and lateral control is designed which has robustness of nonlinear system. In addition, the simulation is performed including initial downrange and crossrange errors, and the results shows that the proposed fuzzy logic controller has good performance.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.450-465
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• 2021

In this study, an attempt has been made to investigate the water-entry characteristics of the high-speed parallel projectile numerically. The shear stress transport k-𝜔 turbulence model and the Zwart-Gerber-Belamri cavitation model based on the Reynolds-Averaged Navier-Stokes method were used. The grid independent inspection and grid convergence index is carried out and verified. The influences of the parallel water-entry on flow filed characteristics, trajectory stability and drag reduction performance for different values of initial water-entry speed (𝜈₀ = 280 m/s, 340 m/s, 400 m/s) and clearance between the parallel projectiles (L_p = 0.5D, 1.0D, 2.0D, 3.0D) are presented and analyzed in detail. Under the condition of the parallel water-entry, it can be found that due to the intense interference between the parallel projectiles, the distribution of cavity is non-uniform and part of the projectile is exposed to water, resulting in the destruction of the cavity structure and the decline of trajectory stability. In addition, the parallel projectile suffers more severe lateral force that separates the two projectiles. The drag reduction performance is impacted and the velocity attenuation is accelerated as the clearance between the parallel projectiles reduces.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.307-310
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• 1996

In this paper, we deal with some numerical analyses of a re-entry vehicle in a 2-dimensional plane as an optimal control problem. To reduce the dynamic load, the heat load and the oscillation in the trajectory, we researched the trajectories in which the load factor or the rate of flight path angle was minimized during re-entry. In addition to that, taking advantage of the monotonous subarc method and the folded time-axis method, we tried to find the heat-less and load-less trajectory with combinations of some sectional functionals so that we can achieve more comfortability.

• Journal of Satellite, Information and Communications
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• v.8 no.4
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• pp.142-149
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• 2013

As we, human expand its everyday life boundary to the geosynchronous orbit, we have experienced frequent chance of the atmospheric re-entry and surface impact of space objects(satellite and space debris). Recently a satellite re-entry monitoring room in Korea has been operated to predict the time and the location of the re-entry of space objects. However, we do not have a domestic version of a numerical re-entry model for normal operation using TLE (Two line Element) information from the United States Strategic Command yet. The space information from the several space operation centers has been used to analyse the re-entry situations. In this paper, the re-entry time is calculated with TLE based on the several atmosphere models, the result is comprehensively analyzed, a new re-entry case model fitted from the result of the predicted satellite re-entry times by a new Rubber Sheet Shift Method used by the domestic satellite re-entry room is suggested.