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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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International Journal of Aeronautical and Space Sciences
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Journal DOI :
The Korean Society for Aeronautical & Space Sciences
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Volume & Issues
Volume 4, Issue 2 - Nov 2003
Volume 4, Issue 1 - May 2003
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Reconfigurable Flight Control System Design Using Sliding Mode Based Model Following Control Scheme
Cho, Dong-Hyun ; Kim, Ki-Seok ; Kim, You-Dan ;
International Journal of Aeronautical and Space Sciences, volume 4, issue 1, 2003, Pages 1~8
DOI : 10.5139/IJASS.2003.4.1.001
In this paper, a reconfigurable flight control system is designed by applying the sliding mode control scheme. The sliding mode control method is a nonlinear control method which has been widely used because of its merits such as robustness and flexibility. In the sliding mode controller design, the signum function is usually included, but it causes the undesirable chattering problem. The chattering phenomenon can be avoided by using the saturation function instead of signum function. However, the boundary layer of the sliding surface should be carefully treated because of the use of the saturation function. In contrast to the conventional approaches, the thickness of the boundary layer of our approach does not need to be small. The reachability to the boundary layer is guaranteed by the sliding mode controller. The fault detection and isolation process is operated based on a sliding mode observer. To evaluate the reconfiguration performance, a numerical simulation using six degree-of-freedom aircraft dynamics is performed.
A Study on Assessment of Composite Couplings for Helicopter Rotor Blades with Multi-cell Sections
Jung, Sung-Nam ; Park, Il-Ju ; Shi, Eui-Sup ; Chopra, Inderjit ;
International Journal of Aeronautical and Space Sciences, volume 4, issue 1, 2003, Pages 9~18
DOI : 10.5139/IJASS.2003.4.1.009
In this work, a closed-form analysis is performed for the structural response of coupled composite blades with multi-cell sections. The analytical model includes the effects of shell wall thickness, transverse shear, torsion warping and constrained warping. The mixed beam approach based on Reissner's semi-complementary energy functional is used to derive the beam force-displacement relations. The theory is validated against experimental test data and other analytical results for coupled composite beams and blades with single-cell box-sections and two-cell airfoils. Correlation of the present method with experimental results and detailed finite element results is found to be very good.
Wind Tunnel Test of the Straight and Forward Swept Canards
Chung, Jin-Deog ; Sung, Bong-Zoo ; Lee, Jang-Yeon ; Kim, Eung-Tai ;
International Journal of Aeronautical and Space Sciences, volume 4, issue 1, 2003, Pages 19~25
DOI : 10.5139/IJASS.2003.4.1.019
A low speed wind tunnel test for the canard airplane model was conducted in KARI LSWT. To measure the required level of accuracy, the image system was applied for all elevator deflection and different canard incidence conditions. By doing so, the difference in aerodynamic characteristics between the forward swept and straight canards can be precisely evaluated, and the pros and cons of both canards arrangements can be discussed. Compared with both canard configurations at the same incidence angle setting, the straight canard has benefits in lift and drag, and the slope of pitching moment increases more moderately than the forward swept canard. The listed data and discussion would be useful to whom wants to design a canard airplane.
Recess Effects on Spray Characteristics of Swirl Coaxial Injectors
Seol, J.H. ; Han, P.G. ; Jeong, W.H. ; Yoon, Y. ;
International Journal of Aeronautical and Space Sciences, volume 4, issue 1, 2003, Pages 26~33
DOI : 10.5139/IJASS.2003.4.1.026
Recess is a geometrical configuration shape that the exit surface of an inner injector is located at a certain length inward from that of an outer injector. It is known to have the characteristics that it can augment mixing efficiency and flame stabilization through internal mixing of propellant in it. So, various experiments, such as backlit stroboscopic photography, phase Doppler particle analyzer(PDPA) and mechanical patternator, were performed at several recess lengths to grasp its effect on the spray characteristics of spray angle, breakup length, atomization and' mixing. Recess length was normalized to dimensionless recess number and two principal mechanisms of impingement and swirl recovery were introduced to explain its influence on the spray characteristics. The effect of recess on SMD doesn't appear significantly near the recess number where mixing efficiency attains to the maximum, whereas mass distribution and mixing efficiency are changed considerably. Thus, it can be inferred that a certain optimum recess number exists, where mixing efficiency becomes the maximum.
Virtual Flutter Plight Test of a Full Configuration Aircraft with Pylon/External Stores
Kim, Dong-Hyun ; Kwon, Hyuk-Jun ; Lee, In ; Paek, Seung-Kil ;
International Journal of Aeronautical and Space Sciences, volume 4, issue 1, 2003, Pages 34~44
DOI : 10.5139/IJASS.2003.4.1.034
An advanced aeroelastic analysis using a computational structural dynamics (CSD), finite element method (FEM) and computational fluid dynamics (CFD) is presented in this Paper. A general aeroelastic analysis system is originally developed and applied to realistic design problems in the transonic flow region, where strong shock wave interactions exist. The present computational approach is based on the modal-based coupled nonlinear analysis with the matched-point concept and adopts the high-speed parallel processing technique on the low-cost network based PC-clustered machines. It can give very accurate and useful engineering data on the structural dynamic design of advanced flight vehicles. For the nonlinear unsteady aerodynamics in high transonic flow region, Euler equations using the unstructured grid system have been applied to easily consider complex configurations. It is typically shown that the advanced numerical approach can give very realistic and practical results for design engineers and safe flight tests. One can find that the present study conducts a virtual flutter flight test which are usually very dangerous in reality.
Parallel 3-D Aerodynamic Shape Optimization on Unstructured Meshes
Lee, Sang-Wook ; Kwon, Oh-Joon ;
International Journal of Aeronautical and Space Sciences, volume 4, issue 1, 2003, Pages 45~52
DOI : 10.5139/IJASS.2003.4.1.045
A three-dimensional aerodynamic shape optimization technique in inviscid compressible flows is developed by using a parallel continuous adjoint formulation on unstructured meshes. A new surface mesh modification method is proposed to overcome difficulties related to patch-level remeshing for unstructured meshes, and the effect of design sections on aerodynamic shape optimization is examined. Applications are made to three-dimensional wave drag minimization problems including an ONERA M6 wing and the EGLIN wing-pylon-store configuration. The results show that the present method is robust and highly efficient for the shape optimization of aerodynamic configurations, independent of the number of design variables used.
Nonlinear Aeroelastic Instability of a Supersonic Missile Wing. with Pitch Axis Freeplay
Kim, Dong-Hyun ; Lee, In ; Paek, Seung-Kil ;
International Journal of Aeronautical and Space Sciences, volume 4, issue 1, 2003, Pages 53~62
DOI : 10.5139/IJASS.2003.4.1.053
In this study, nonlinear aeroelastic characteristics of an supersonic missile wing with strong shock interferences are investigated. The missile wing model has a freeplay structural nonlinearity at its pitch axis. To practically consider the effects of freeplay structural nonlinearity, the fictitious mass method is applied to structural vibration analysis based on finite element method. Nonlinear aerodynamic flows with unsteady shock waves are also considered in supersonic flow regions. To solve the nonlinear aeroelastic governing equations including the freeplay effect, a modal-based coupled time-marching technique based on the fictitious mass method is used in the time-domain. Various aeroelastic computations have been performed for the nonlinear wing structure model. Linear and nonlinear aeroelastic analyses have been conducted and compared with each other in supersonic flow regions. Typical nonlinear limit cycle oscillations and phase plots are presented to show the complex vibration phenomena with simultaneous fluid-structure nonlinearities.
Visualization and Flowfield Measurements of the Vortical Flow over a Double-Delta Wing
Sohn, Myong-Hwan ; Jang, Young-IL ;
International Journal of Aeronautical and Space Sciences, volume 4, issue 1, 2003, Pages 63~74
DOI : 10.5139/IJASS.2003.4.1.063
The vortical flow of a 65-deg flat plate delta wing with a leading edge extension(LEX) was examined through off-surface visualization, 5-hole probe and hot-film measurements. The off-surface flow visualization technique used micro water droplets generated by a home-style ultrasonic humidifier and a laser beam sheet. The angles of attack ranged from 10 to 30 degrees, and the sideslip angles ranged from 0 to -15 degrees. The Reynolds number was
for the flow visualization, and
for the 5-hole probe and hot-film measurements. The comparison of the visualization photos and the flow field measurement showed that the two results were in a good agreement for the relative position and the structure of the wing and LEX vortices, even though the flow Reynolds numbers of the two results were much different. The wing vortex and the LEX vortex coil each other while maintaining a comparable strength and identity at zero sideslip. Neither a looping of the wing vortex around the strake vortex, nor the lopsided coiling of the stronger strake and the weaker wing vortices was observed. At non-zero sideslip, the downward movement of the LEX vortex when going downstream was enhanced on the windward side, and the downward and inboard movement of the LEX vortex when going downstream was suppressed on the leeward side. The counterclockwise coiling of the wing and LEX vortices was decreased significantly on the leeward side.
Ground Experiment of Spacecraft Attitude Control Using Hardware Testbed
Oh, Choong-Suk ; Bang, Hyo-Choong ;
International Journal of Aeronautical and Space Sciences, volume 4, issue 1, 2003, Pages 75~87
DOI : 10.5139/IJASS.2003.4.1.075
The primary objective of this study is to demonstrate ground-based experiment for the attitude control of spacecraft. A two-axis rotational simulator with a flexible ann is constructed with on-off air thrusters as actuators. The simulator is also equipped with payload pointing capability by simultaneous thruster and DC servo motor actuation. The azimuth angle is controlled by on-off thruster command while the payload elevation angle is controlled by a servo-motor. A thruster modulation technique PWM(Pulse Width Modulation) employing a time-optimal switching function plus integral error control is proposed. An optical camera is used for the purpose of pointing as well as on-board rate sensor calibration. Attitude control performance based upon the new closed-loop control law is demonstrated by ground experiment. The modified switching function turns out to be effective with improved pointing performance under external disturbance. The rate sensor calibration technique by Kalman Filter algorithm led to reduction of attitude error caused by the bias in the rate sensor output.
Parametric Study for the Low BVI Noise Rotor Blade Design
Hwang, Chang-Jeon ; Joo, Gene ;
International Journal of Aeronautical and Space Sciences, volume 4, issue 1, 2003, Pages 88~98
DOI : 10.5139/IJASS.2003.4.1.088
Compared to the noise limits (CAN7) specified in ICAO Annex 16 for civil helicopters, the Lynx helicopter equipped with BERP blades has only 0.2 EPNdB margin in the approach case although it has more than 4 EPNdB margin in fly-over and take-off conditions. The objectives of the study described in this paper were to devise a low noise main rotor blade for the Lynx using UEAF combined with the high resolution airload model ACROT. A design requirement is that the new blade, KBERP (Korean BERP) blade should achieve a significant reduction in noise during approach(at least 6EPNdB margin) without any noise penalty in fly-over and take-off conditions and minimal performance penalty. It was decided to investigate a tip modification to the BERP blade, employing the twin vortex concept to reduce the BVI noise and to retain the excellent high speed performance characteristics of BERP. Through the parametric study, the KBERP blade with optimized twin vortices has at least a 9 EPNdB noise margin in approach flight condition with only a small penalty in fly-over and take-off conditions. The KBERP tip is thus a very cost effective wav to reduce BVI noise during approach.
Three-axis Attitude Control for Flexible Spacecraft by Lyapunov Approach under Gravity Potential
Bang, Hyo-Choong ; Lee, Kwang-Hyun ; Lim, Hyung-Chul ;
International Journal of Aeronautical and Space Sciences, volume 4, issue 1, 2003, Pages 99~109
DOI : 10.5139/IJASS.2003.4.1.099
Attitude control law synthesis for the three-axis attitude maneuver of a flexible spacecraft model is presented in this study. The basic idea is motivated by previous works for the extension into a more general case. The new case includes gravitational gradient torque which has significant effect on a wide range of low earth orbit missions. As the first step, the fully nonlinear dynamic equations of motion are derived including gravitational gradient. The control law design based upon the Lyapunov approach is attempted. The Lyapunov function consists of a weighted combination of system kinetic and potential energy. Then, a set of stabilizing control law is derived from the basic Lyapunov stability theory. The new control law is therefore in a general form partially validating the previous work in some sense.