• International Journal of Aeronautical and Space Sciences
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• 제9권1호
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• pp.121-128
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• 2008

This paper describes the modeling and autopilot design procedure of a Blended Wing-Body(BWB) UAV. The BWB UAV is a tailless design that integrates the wing and the fuselage. This configuration shows some aerodynamic advantages of lower wetted area to volume ratio and lower interference drag as compared to conventional type UAV. Also, BWB UAV may be increase payload capacity and flight range. However, despite of these benefits, this type of UAV presents several problems related to flying qualities, stability, and control. In this paper, the detailed modeling procedure of BWB UAV and stability analysis results using the linearized model at trim condition are represented. Finally, we designed the autopilot of BWB UAV based on a simple control allocation scheme and evaluated its performance through nonlinear simulation.

• 한국항공우주학회지
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• 제46권2호
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• pp.141-149
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• 2018

본 논문에서는 전익형 무인항공기의 복합손상을 고려한 신경망 적응제어기 연구 결과를 기술하였다. 여기서 복합손상이란 무인항공기의 주익과 수직미익의 동시 손상을 의미한다. 시뮬레이션을 통하여 종/횡축 불안정성과 비행역학 특성을 확인하였다. 이를 바탕으로 두 가지 형태의 역변환 제어기 기반 적응형 신경망 제어기를 설계하였다. 또한 두 가지 역변환 제어기 구조에 따라 무인항공기의 복합 손상 시 제어 성능 분석을 수행하였다. 역변환 제어기 구조에 따라서 일반 상황과 손상 상황에서 성능 차이를 확인하였다. 최종적으로 무인기에 발생된 복합손상으로 인한 항공기의 불안정성은 적용된 제어기를 통하여 극복할 수 있음을 확인하였다.

• International Journal of Aeronautical and Space Sciences
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• 제9권2호
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• pp.114-120
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• 2008

In the vision-based recovery phase, a terminal guidance for the blended-wing UAV requires visual information of high accuracy. This paper presents the light source target design and detection algorithm for vision-based UAV recovery. We propose a recovery target design with red and green LEDs. This frame provides the relative position between the target and the UAV. The target detection algorithm includes HSV-based segmentation, morphology, and blob processing. These techniques are employed to give efficient detection results in day and night net recovery operations. The performance of the proposed target design and detection algorithm are evaluated through ground-based experiments.

• International Journal of Aeronautical and Space Sciences
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• 제18권2호
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• pp.290-299
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• 2017

Reconfigurable flight control using various kinds of adaptive control methods has been studied since the 1970s to enhance the survivability of aircraft in case of severe in-flight failure. Early studies were mainly focused on the failure of actuators. Recently, studies of reconfigurable flight controls that can accommodate complex damage (partial wing and tail loss) in conventional aircraft were reported. However, the partial wing loss effects on the aerodynamics of conventional type aircraft are quite different to those of BWB(blended wing body) aircraft. In this paper, a reconfigurable flight control algorithm was designed using a direct model reference adaptive method to overcome the instability caused by a complex damage of a BWB aircraft. A model reference adaptive control was incorporated into the inner loop rate control system enhancing the performance of the baseline control to cope with abrupt loss of stability. Gains of the model reference adaptive control were polled out using the Liapunov's stability theorem. Outer loop attitude autopilot was designed to manage roll and pitch of the BWB UAV as well. A 6-DOF dynamic model was built-up, where the normal flight can be made to switch to the damaged state abruptly reflecting the possible real flight situation. 22% of right wing loss as well as 25% loss for both vertical tail and rudder control surface were considered in this study. Static aerodynamic coefficients were obtained via wind tunnel test. Numerical simulations were conducted to demonstrate the performance of the reconfigurable flight control system.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.579-582
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• 2008

PEM Fuel cell system was designed and constructed to use as a power source of unmanned aerial vehicles(UAV) in the present study. Sodium borohydride was selected as a hydrogen source and was decomposed by catalytic hydrolysis reaction. Fuel cell system consists of a fuel cell stack, a hydrogen generation system(HGS), and power management system(PMS). HGS was composed of a catalytic reactor, micropump, fuel cartridge, and separator. Hybrid power system between lithium-polymer battery and fuel cell was developed. The fuel cell system was integrated and packaged into a blended wing-body UAV. Energy density of the total system was 1,000 $W{\cdot}hr/kg$ and high endurance more than 5 hours was accomplished in the ground tests.

• Advances in aircraft and spacecraft science
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• 제6권4호
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• pp.283-296
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• 2019

The influence of different planform parameters on the aerodynamic performance of large-scale subsonic and transonic Blended Wing Body (BWB) aircraft have gained comprehensive research in the recent years, however, it is not the case for small-size low subsonic speed Unmanned Aerial Vehicles (UAVs). The present work numerically investigates aerodynamics governing four different trailing edge geometries characterizing BWB configurations in standard flight conditions at angles of attack from $-4^{\circ}$ to $22^{\circ}$ to provide generic information that can be essential for making well-informed decisions during BWB UAV conceptual design phase. Simulation results are discussed and comparatively analyzed with useful implications for formulation of proper mission profile specific to every BWB configuration.

• 항공우주시스템공학회지
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• 제17권5호
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• pp.34-41
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• 2023

본 논문은 최근 각광받고 있는 소형 무인항공기에 결빙효과와 윙락 불확실성을 적용하고 여러 제어기법을 활용하여 자세 제어 시뮬레이션 수행하였으며 그 결과를 다룬다. 먼저 선정 기체인 BWB 형태의 소형 무인 항공기인 Skywalker X8 기체의 기본 형상과 결빙효과가 적용된 형상에 대하여 선형화를 수행하였다. 이후 MATLAB SimulinkⓇ를 활용하여 외란 관측기 기반 PID 제어, 모델 참조 적응 제어, 모델 예측 제어기법을 사용하여 기본 형상과 결빙효과가 적용된 형상에 대하여 roll 및 pitch 자세 제어 시뮬레이션을 수행한다. 또한, 기존 연구에서 진행되지 않았던 윙락 불확실성을 결빙이 적용된 형상에 동시 적용하여 시뮬레이션을 수행하였으며 각 제어기법의 성능을 비교 분석하였다.

• 한국항공우주학회지
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• 제47권6호
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• pp.422-428
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• 2019

수직미익이 없는 전익기 형상은 낮은 레이더반사면적(RCS) 특성으로 인해 최근 UCAV를 위한 대표적인 형상으로 대두되고 있다. 무미익 전익기 형상은 방향축 관점에서 보면 정적으로 불안정하면서도 이를 효과적으로 제어하기 위한 수직 조종면이 없다는 두 가지 난제를 모두 갖고 있다. 이같은 형상을 제어하기 위해서는 추력 벡터링을 적용하거나 날개의 항력차이를 이용하는 드래그 러더(Drag Rudder) 형태의 에일러론 또는 스포일러 등을 적용할 수 있다. 본 논문에서는 전익기 형상의 횡방향축 공력특성 및 드래그 러더 중 스포일러 형태의 조종면에 대한 공력특성을 설명한다. 또한, PI 구조의 제어설계 기법을 사용하여 전익기의 횡방향축 운동을 효과적으로 제어할 수 있음을 제시하고, 비행시험을 통하여 설계된 제어기로 안정적인 비행이 가능함을 보였다.

• 한국전산유체공학회지
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• 제21권2호
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• pp.70-80
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• 2016

The comparison of two commercial codes(FLUENT and STAR-CCM+) and an open-source code(OpenFOAM) are carried out for the aerodynamic analysis of flight vehicles at low speeds. Tailless blended-wing-body UCAV, main wing and propeller of HALE UAV(EAV-3) are chosen as geometries for the investigation. Using the same mesh, incompressible flow simulations are carried out and the results from three different codes are compared. In the linear region, the maximum difference of lift and drag coefficients of UCAV are found to be less than 2% and 5 counts, respectively and shows good agreement with wind tunnel test data. In a stall region, however, the reliability of RANS simulation is found to become poor and the uncertainty according to code also increases. The effect of turbulence models and meshes generated from different tools are also examined. The transition model yields better results in terms of drag which are much closer to the test data. The pitching moment is confirmed to be sensitive to the existence and the location of transition. For the case of EAV-3 wing, the difference of results with ${\kappa}-{\omega}$ SST model is increased when Reynolds number becomes low. The results for the propeller show good agreement within 1% difference of thrust. The reliability and uncertainty of three codes is found to be reasonable for the purpose of engineering use. However, the physical validity and reliability of results seem to be carefully examined when ${\kappa}-{\omega}$ SST model is used for aerodynamic simulation at low speeds or low Reynolds number conditions.