• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.321-326
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• 2007

The joined-wing is a new concept of the airplane wing. The fore-wing and the aft-wing arc joined together in the joined-wing. The range and loiter are longer than those of a conventional wing. The joined-wing can lead to increased aerodynamic performances and reduction of the structural weight. The structural behavior of the joined-wing has a high geometric nonlinearity according to the external loads. The gust loads are the most critical loading conditions in the structural design of the joined-wing. The nonlinear behavior should be considered in the optimization of the joined-wing. It is well known that conventional nonlinear response optimization is extremely expensive: therefore, the conventional method is almost impossible to use in large scale structures such as the joined-wing. In this research, geometric nonlinear response structural optimization is carried out using equivalent loads. Equivalent loads are the load sets which generate the same response field in linear analysis as that from nonlinear analysis. In the equivalent loads method, the external loads are transformed to the equivalent loads (EL) for linear static analysis, and linear response optimization is carried out based on the EL.

• 대한기계학회논문집A
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• 제30권5호
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• pp.585-594
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• 2006

The joined-wing is a new concept of the airplane wing. The fore-wing and the aft-wing are joined together in a joined-wing. The range and loiter are longer than those of a conventional wing. The joined-wing can lead to increased aerodynamic performance and reduction of the structural weight. In this research, dynamic response optimization of a joined-wing is carried out by using equivalent static loads. Equivalent static loads are made to generate the same displacement field as the one from dynamic loads at each time step of dynamic analysis. The gust loads are considered as critical loading conditions and they dynamically act on the structure of the aircraft. It is difficult to identify the exact gust load profile. Therefore, the dynamic loads are assumed to be (1-cosine) function. Static response optimization is performed for the two cases. One uses the same design variable definition as dynamic response optimization. The other uses the thicknesses of all elements as design variables. The results are compared.

• International Journal of Aerospace System Engineering
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• 제10권1호
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• pp.1-13
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• 2023

The present study was attempted to investigate flow interference effects and the aerodynamic characteristics of the front and rear wings of a joined-wing aircraft by changing the configuration variables. The study was performed using a computational fluid dynamics(CFD) tool to demonstrate forward flight and analyze aerodynamic characteristics. A total of 9 configurations were analyzed with variations on the position, height, dihedral angle, incidence angle, twist angle, sweepback angle, and wing area ratio of the front and rear wings while the fuselage was fixed. The quantities of aerodynamic coefficients were confirmed in accordance with joined-wing configurations. The closer the front and rear wings were located, the greater the flow interference effects tended. Interestingly, the rear wing did not any configuration change, the lift coefficient of the rear wing was decreased when adjusted to increase the incidence angle of the front wing. The phenomenon was appeared due to an effective angle of attack alteration of the rear wing resulting from the flow interference by the front wing configurations.

• Advances in aircraft and spacecraft science
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• 제6권2호
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• pp.117-144
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• 2019

High Altitude and Long Endurance (HALE) aircraft are capable of providing intelligence, surveillance and reconnaissance (ISR) capabilities over vast geographic areas when equipped with advanced sensor packages. As their use becomes more widespread, the demand for additional range, endurance and payload capability will increase and designers are exploring non-conventional configurations to meet the increasing demands. One such configuration is the joined-wing concept. A joined-wing aircraft is one that typically connects a front and aft wings in a diamond shaped planform. One such example is the Boeing SensorCraft configuration. While the joined-wing configuration offers potential benefits regarding aerodynamic efficiency, structural weight, and sensing capabilities, structural design requires careful consideration of elastic buckling resulting from the aft wing supporting, in compression, part of the forward wing structural loading. It has been shown already that this is a nonlinear phenomenon, involving geometric nonlinearities and follower forces that tend to flatten the entire configuration, leading to structural overload due to the loss of the aft wing's ability to support the forward wing load. Severe gusts are likely to be the critical design condition, with flight control system interaction in the form of Gust Load Alleviation (GLA) playing a key role in minimizing the structural loads. The University of Victoria Center for Aerospace Research (UVic-CfAR) has built a 3-meter span scaled and flexible wing UAV based on the Boeing SensorCraft design. The goal is to validate the nonlinear structural behavior in flight. The main objective of this research work is to perform Ground Vibration Tests (GVT) to characterize the dynamic properties of the scaled flight vehicle. Results from the experimental tests are used to characterize the modal dynamics of the aircraft, and to validate the numerical models. The GVT results are an important step towards a safe flight test program.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.216.2-216.2
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• 2005

• Advances in aircraft and spacecraft science
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• 제2권2호
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• pp.125-168
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• 2015

Dynamic aeroelastic behavior of structurally nonlinear Joined Wings is presented. Three configurations, two characterized by a different location of the joint and one presenting a direct connection between the two wings (SensorCraft-like layout) are investigated. The snap-divergence is studied from a dynamic perspective in order to assess the real response of the configuration. The investigations also focus on the flutter occurrence (critical state) and postcritical phenomena. Limit Cycle Oscillations (LCOs) are observed, possibly followed by a loss of periodicity of the solution as speed is further increased. In some cases, it is also possible to ascertain the presence of period doubling (flip-) bifurcations. Differences between flutter (Hopf's bifurcation) speed evaluated with linear and nonlinear analyses are discussed in depth in order to understand if a linear (and thus computationally less intense) representation provides an acceptable estimate of the instability properties. Both frequency- and time-domain approaches are compared. Moreover, aerodynamic solvers based on the potential flow are critically examined. In particular, it is assessed in what measure more sophisticated aerodynamic and interface models impact the aeroelastic predictions. When the use of the tools gives different results, a physical interpretation of the leading mechanism generating the mismatch is provided. In particular, for PrandtlPlane-like configurations the aeroelastic response is very sensitive to the wake's shape. As a consequence, it is suggested that a more sophisticate modeling of the wake positively impacts the reliability of aerodynamic and aeroelastic analysis. For SensorCraft-like configurations some LCOs are characterized by a non-synchronous motion of the inner and outer portion of the lower wing: the wing's tip exhibits a small oscillation during the descending or ascending phase, whereas the mid-span station describes a sinusoidal-like trajectory in the time-domain.

• 한국항공우주학회지
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• 제30권2호
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• pp.108-114
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• 2002

본 연구에서는 KSR-Ⅲ 로켓의 날개-동체 조인트에 대한 비선형 유한요소해석을 수행하므로 적절한 설계 개선을 제시하였으며, 최종 설계의 검증을 위해 수행된 구조 시험 결과와 비교하여 해석의 타당성을 평가하였다. 날개-동체 조인트는 동체 프레임 상에 존재하는 체결 홈에 날개의 체결부가 끼워짐으로 연결되는 방식으로 설계되었다. 이 방식은 연결 구조물간의 하중 전달을 주로 구조물간의 접촉면을 통해 이루어지게 하며, 체결 볼트를 통해서는 구조물을 고정하되 전달 하중은 최소화하기 위한 것이다. 조인트 구조의 정확한 해석을 위해 연결 구조물간의 접촉 및 체결 볼트를 통한 하중 전달을 묘사할 수 있는 세심한 구조 모델링을 적용하였다. 해석 결과에 의해 제시된 설계 개선은 구조시험을 통해 안전성이 검증되었으며, 해석 및 시험 결과가 잘 일치하였다.

• 한국컴퓨터정보학회논문지
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• 제24권12호
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• pp.25-33
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• 2019

본 논문은 목표한 방향으로 자유롭게 기동할 수 있는 새 크기의 물리기반 날갯짓 비행로봇 시뮬레이션을 위한 동역학적 신경망 컨트롤러를 생성하는 통합적인 진화연산 방법을 제시한다. 제안된 진화로봇 시스템은 날갯짓 비행의 추가적인 민첩성과 안정성을 위하여 Morphological Computation 개념을 응용한 간단한 날개 순응성 모델과 그와 통합된 Mechanosensory 정보를 활용한다. 역학적으로 불안정한 날갯짓 기동의 안정성 개선을 위해 로봇의 날개는 회전스프링으로 팔의 골격에 연결된 여러개의 패널들로 모델링되어, 새의 깃털에서 영감을 받은 단순한 형태의 날개 유연성을 시뮬레이션 하도록 설계되었다. 신경망 컨트롤러 역시 생물학적으로 의미있는 좌우대칭적 연결구조를 가짐과 동시에 최대의 진화연산 탐색 가능성을 위해 두 개의 fully-connected 신경망 모듈로 이루어지며, 이를 위한 센서정보로서 항법센서와 더불어 각 날개패널의 움직임 보들이 입력되어진다. 이러한 설계는 각 패널센서로 하여금 잠재적으로 신경망의 날갯짓 패턴 생성에 관여하게 함과 동시에, 날개에 가해지는 힘의 감지와 패널의 굽어짐으로 인한 날개 순응성으로부터 얻을 수 있는 비행의 민첩성과 안정성 향상을 동시에 유도할 수 있다. 본 시스템으로 진화된 날갯짓 로봇은 실시간으로 주어지는 목표방향으로의 효과적인 기동과 함께, 외부의 공기역학적 섭동에 대하여도 더욱 안정적인 비행을 유지함을 보여준다.