Passive morphing of flying wing aircraft: Z-shaped configuration

High Altitude, Long Endurance (HALE) aircraft can achieve sustained, uninterrupted flight time if they use solar power. Wing morphing of solar powered HALE aircraft can significantly increase solar energy absorbency. An example of the kind of morphing considered in this paper requires the wings to fold so as to orient a solar panel to be hit more directly by the sun's rays at specific times of the day. An example of the kind of morphing considered in this paper requires the wings to fold so as to orient a solar panel that increases the absorption of solar energy by decreasing the angle of incidence of the solar radiation at specific times of the day. In this paper solar powered HALE flying wing aircraft are modeled with three beams with lockable hinge connections. Such aircraft are shown to be capable of morphing passively, following the sun by means of aerodynamic forces and engine thrusts. The analysis underlying NATASHA (Nonlinear Aeroelastic Trim And Stability of HALE Aircraft), a computer program that is based on geometrically exact, fully intrinsic beam equations and a finite-state induced flow model, was extended to include the ability to simulate morphing of the aircraft into a “Z” configuration. Because of the “long endurance” feature of HALE aircraft, such morphing needs to be done without relying on actuators and at as near zero energy cost as possible. The emphasis of this study is to substantially demonstrate the processes required to passively morph a flying wing into a Z-shaped configuration and back again.     

民机中央翼舱段适坠性仿真

建立了带中央翼的民机舱段的有限元模型,应用MSC.Dytran分析软件对民机中央翼舱段模型进行坠撞仿真,得到加速度响应和客舱舱体结构变形结果.结果表明,带中央翼舱段发生坠撞后,乘客的生存空间基本没有变化,撞击能量主要靠舱段下部的龙骨梁、框及蒙皮和中央翼壁板的破坏来吸收,地板导轨的峰值加速度比不带中央翼的典型舱段的峰值加速度要大许多.     

基于救援效率的

面临重大灾害事件,通航救援具有快速、高效、受地理空间限制少的优势,是保护生命财产安全、减少社会危害和经济损失的有效手段.针对国内现有的通航救援调度模型未考虑"多对多"的配送模式,构建了以最大化救援效率、最小化总飞行里程为目标的多出救点、多受灾点航空器调度模型,提出一种遗传-模拟退火混合算法对模型进行求解.最后,通过实例测试以及与其他算法的比较,验证了所提方法的有效性,为通航应急救援提供合理、可行的调度方案.     

Analytical and Experimental Analysis of Wing Rock

The paper deals with the study of an analytical model of wingrock, based on parameter identification of experimental data. Theexperiments were performed in the Aeronautical Laboratory of Politecnicodi Torino, in the D3M Low Speed Wind Tunnel, on a80° delta wing. Free-to-roll tests have been used todetermine build-up and limit cycle characteristics of wing rock. Flowvisualization techniques were also utilized in order to track vortexpositions. The characteristics of the limit cycle (oscillation amplitudeand frequency) were compared in detail with reference results obtainedin other laboratories. An analytical nonlinear model was derived.Parameters were identified by means of the least-squares approximationof experimental data with coherent initial conditions. The consistencyof time histories, reproduced by numerical integration, was alsoanalyzed. This formulation correctly predicts stable limit cycles for awide range of airspeeds, angles of attack and release roll angles.     

定常吹气对倾转旋翼机向下载荷的影响

为进一步提高倾转旋翼机悬停状态下的有效载重,开展了定常吹气流动控制对向下载荷的影响研究。首先应用延迟脱体涡模拟(DDES)方法对翼型-90°迎角下非定常大范围分离流动结构进行了数值分析;然后分别开展了前缘吹气、后缘吹气降载措施研究,揭示了吹气降载的机理,并对不同吹气口位置和吹气动量系数的影响进行了定量分析,最后开展了前、后缘同时吹气作用下降载数值模拟研究。计算结果表明:前缘最佳吹气位置在翼型的前缘点,而后缘吹气最佳位置位于襟翼弦长的15%处;前缘吹气的降载效果要优于后缘吹气,而且吹气动量系数对向下载荷的影响较小;相对于初始未施加流动控制构型,阻力系数减小量可达到32.72%。     

飞行弹射救生中的上肢受力及甩打运动研究

本研究了在弹射救生中,飞行员未脱手时上肢的受力状况,以及脱手以后上肢的自由甩打运动。建立了上肢三刚体七自由度的模型,用虚位移原理建立了脱手前上肢约束力的方程,用Ｋａｎｅ方法建立了脱手后上肢自由甩打运动的动力学方程,研究了各种弹射状态下上肢的受力情况及上肢的运动规律。     

基于SOM算法和免疫神经网络的飞机燃油系统故障诊断

针对传统的飞机燃油系统故障诊断方法如硬件冗余方法和系统模型检测方法存在的飞机重量限制和难以建立精确数学模型的问题,设计了一种基于SOM算法和BP神经网络的故障诊断模型;首先,建立了系统故障诊断模型并对诊断原理进行了描述,然后,对故障征兆数据进行预处理,即先采用SOM算法进行连续属性离散化处理,再通过粗糙集互信息方法进行属性降维,以减少数据量和提高诊断效率;最后,建立了基于BP神经网络的故障诊断模型,为了进一步提高故障诊断精度,在采用免疫优化算法对BP神经网络故障诊断模型中的各参数即权值和阈值等进行优化的基础上,进一步采用BP反向传播算法进行参数调整,从而得到最终的故障诊断模型。通过飞机燃油系统故障诊断实例仿真实验证明了文中方法能较为精确地实现故障诊断,且与其它方法相比,具有较高的诊断精度和诊断效率,具有较大的优越性。     

民用飞机健康状态评估方法 

飞机健康状态评估技术能够为飞机的健康状态提供量化评价的方法和手段,通过给出量化的飞机健康指数值,可以为后续的飞机维修提决策提供必要的技术基础;在分析了健康状态评估的技术现状的基础上,对飞机整机级的健康状态评估方法进行了研究,提出了健康状态评估技术方案,并对波音AHM系统健康指数模型进行了研究;提出的民用飞机健康状态评估方法,实现了从传统的对故障的状态识别转移至对性能退化程度的检测和量化描述,其应用可以为航空公司安排飞机运营提供参考,并为合理安排计划维修提供决策支持。     

Wind identification along a flight trajectory,part 1: 3D-kinematic approach

This paper deals with the identification of the wind profile along a flight trajectory by means of a three-dimensional kinematic approach. The approach is then applied to a recent aircraft accident, that of Flight Delta 191, which took place at Dallas-Fort Worth International Airport on August 2, 1985.In the 3D-kinematic approach, the wind velocity components are computed as the difference between the inertial velocity components and the airspeed components. The airspeed profile is obtained from flight measurements. The inertial velocity profile is obtained by integration of the measured inertial acceleration. The accelerometer biases and the impact values of the inertial velocity components are determined by matching the computed flight trajectory with the measured flight trajectory, available from the digital flight data recorder (DFDR) and air traffic control radar (ATCR). This leads to a least-square problem, which is solved analytically.Key to the precision of the identified wind profile is the correct identification of the accelerometer biases and the impact velocity components. In turn, this depends on the proper selection of the integration time. Because the measured data are noise-corrupted, unstable identification occurs if the integration time is too short. On the other hand, stable identification takes place if the integration time is properly chosen.Application of the method developed to the case of Flight Delta 191 shows that the identification problem has a stable solution if the integration time is larger than 180 sec. Numerical computation shows that, for Flight Delta 191, the maximum wind velocity difference determined with the 3D-kinematic approach was W _x =124 fps in the longitudinal direction, W _y =66 fps in the lateral direction, and W _h =71 fps in the vertical direction.Notations a _b measured acceleration, ft/sec² - a _bx ,a _by ,a _bz measured acceleration components, body axes system, ft/sec² - b accelerometer bias, ft/sec² - b _x ,b _y ,b _z accelerometer bias components, body axes system, ft/sec² - g acceleration of gravity, ft/sec² - h altitude above sea level, positive upward, ft - m mass, lb sec²/ft - p air pressure, lb/ft² - R gas constant for air, ft²/sec² °R - S reference wing area, ft² - t running time, sec - T air temperature, °R - V _a airspeed, ft/sec - V _ax ,V _ay ,V _az airspeed components, Earth axes system, ft/sec - V _e inertial velocity, ft/sec - V _ex ,V _ey ,V _ez inertial velocity components, Earth axes system, ft/sec - V _ia indicated airspeed, ft/sec - W mg=weight, lb - W wind velocity, ft/sec - W _x ,W _y ,W _z wind velocity components, Earth axes system, ft/sec - x, y, z Cartesian coordinates, Earth axes system, ft - x longitudinal coordinate, positive northward, Earth axes system, ft - y lateral coordinate, positive eastward, Earth axes system, ft - z vertical coordinate, positive downward, Earth axes system, ft - angle of attack, rad - path inclination, rad - pitch angle, rad - bank angle, rad - air density, lb sec²/ft⁴ - sideslip angle, rad - integration time, sec - roll angle, rad This research was supported by Air Line Pilots Association (ALPA), United States Aviation Underwriters (USAU), and Texas Advanced Technology Program, Grant No. TATP-003604020. This paper is based on Ref. 1.     

Spectroscopic Detection of Sulfur Oxides in the Aircraft Wake

The absorption/emission spectral regions of SO, SO₂, SO₃, S₂O and HSO are analyzed for the range from UV (λ ≥ 0.2 μm) to IR (λ < 30 μm) and are compared with the atmospheric transmission spectrum. It is shown that many vibrational bands of the compounds considered fall into atmospheric transmission windows. For the vibrational bands of SO, SO₂, SO₃, S₂O, and HSO molecules there are some gases which hinder the absorption diagnostics of the indicated compounds. These interfering gases are natural components of atmospheric air as well as specific gases of aircraft engine exhaust. It is found that the least influence of the interference takes place in the 2400–2700 cm⁻¹ IR region. The spectroscopic techniques used for the detection of aircraft engine exhaust compounds are briefly reviewed, with much consideration given to SO₂. The IR absorption spectra of SO₂ and other gases are calculated for the conditions of the aircraft engine nozzle exit. Narrow spectral intervals suitable for SO₂ detection in a hot flow are determined. An analysis is made for the detection capabilities of CO₂ lasers (including isotope CO₂ lasers) and CO lasers (both fundamental band and first-overtone ones) as applied to SO₂ detection in aircraft engine exhaust. Published in English as Preprint No. 5 of the P. N. Lebedev Physical Institute, Moscow (2004).