• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.2
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• pp.114-121
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• 2019

Tailless aircraft have advantages of low visibility compared to conventional aircraft, but drawback of poor stability as well which makes designing controller difficult. The controller design is more difficult, especially when the center of gravity moves due to store release or fuel consumption during flight. In this paper, an L1 adaptive controller is proposed as a way to overcome these problems. The reliability and performance of the controllers were verified by non-linear simulations. RPV Flying Quality Design criteria were used for design criteria. Using the simulation, it is shown that the adaptive controller maintains stability of the unmanned aircraft for sudden large change in the inertial properties. It is also shown that the calculation burden can be reduced when it is used with the gain scheduling method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.7
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• pp.552-561
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• 2016

In this experimental study, the dynamic stability derivatives of a tailless lambda-shape UAV are estimated from time history data of aerodynamic moments measured from the internal balance while the test model is forced to oscillate at given frequencies and amplitudes. A 3-axis forced oscillation apparatus is designed to induce decoupled roll, yaw, pitch oscillations respectively. The results show that the roll damping derivatives remain stable at the entire range of angle of attack tested, whereas the pitch damping derivatives become unstable beyond $15^{\circ}$ angle of attack. The amplitude and frequency have little impact on roll damping derivatives while the smaller amplitude and frequency of oscillation improves the pitch stability. The yaw damping derivative values are fairly small as expected for a tailless configuration. The results indicate that the proposed methodology and test apparatus area valid for estimating the dynamic stability derivatives of a tailless UAV.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.554-559
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• 2016

본 논문은 EDISON CFD를 사용하여 스포일러가 장착된 무미익 BWB UCAV에 대하여 이차원 유동해석을 수행하였다. 무미익 형상은 일반적인 항공기보다 롤과 요 방향의 안정성과 조성성에 있어 불리한 특징을 갖는데 특히 이 착륙 시 고 받음각의 영역에서 발생하는 Pitch-up 현상이 항공기 안정성에 문제를 야기한다. 수직 미익 부재와 pitch-up 현상으로 인한 BWB형상의 UCAV가 지니는 단점을 보완하기 위해서 스포일러가 장착된 형상이 적용되기도 한다 본 연구에서는 윗면과 아랫면에 스포일러가 장착된 경우에 대해 전산유동해석을 수행하였다. 해석결과 윗면의 스포일러는 양력의 감소와 항력의 증가를 야기했으며, 아랫면의 스포일러는 양력과 항력을 모두 증가시켰다. 피칭모멘트의 경우 아랫면의 스포일러가 저받음각에서 안정성을 증가시켰다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.6
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• pp.422-428
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• 2019

A tailless or Blended-Wing-Body(BWB) shaped configuration is highlighted for UCAV with low RCS characteristics. The BWB configuration is characterized by its directional static instability and low controllability. To control the directional movement of the BWB configured vehicle, directional thrust vectoring equipment or drag rudder typed control surfaces which utilize the drag differences of the wing can be considered. This paper deals with a BWB shaped configuration using a spoiler and describes the lateral-directional aerodynamic characteristics of the vehicle. In addition, it is shwon that the lateral-directional motion can be controlled effectively by using the classical PI control structure. This control law is verified by flight test and showed adequate for the tailless BWB shaped UAV.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.3
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• pp.232-242
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• 2015

For stealth performance consideration, many UAV designs are adopting tailless lambda-shaped configurations which are likely to have unsteady dynamic characteristics. In order to control such UAVs through automatic flight control system, more accurate estimation of dynamic stability derivatives becomes essential. In this paper, dynamic stability derivatives of a tailless lambda-shaped UAV are estimated through numerically simulated forced oscillation method incorporating dynamic mesh technique. First, the methodology is validated by benchmarking the CFD results against previously published experimental results of the Standard Dynamics Model(SDM). The dependency of initial angle of attack, oscillation frequency and oscillation magnitude on the dynamic stability derivatives of a tailless UAV configuration is then studied. The results show reasonable agreements with experimental reference data and prove the validity and efficiency of the concept of using CFD to estimate the dynamic derivatives.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.1
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• pp.1-9
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• 2018

Lambda wing type Unmanned Combat Aerial Vehicle(UCAV) which adopts Blended Wing Body(BWB) has relatively less drag and more stealth performance than conventional aircraft. However, Pitching moment is rapidly increased at a specific angle of attack affected by leading edge vortex due to leading edge sweep angle. Wind tunnel testing and numerical analysis were carried out with UCAV 1303 configuration on condition of 50 m/s of flow velocity, $-4^{\circ}{\sim}28^{\circ}$ of the range of angle-of-attack. The effect of wing twist for longitudinal stability at the various angles of attack was verified in this study. When negative twist is applied on the wing, Pitch-break was onset at higher angle of attack due to delayed flow separation on outboard of the wing. On the other hand, pitch-break was onset at lower angle of attack and lift-to-drag ratio was increased when positive twist is applied on the wing.