主-从多飞行器三维分布式协同制导方法

针对三维空间下的多飞行器协同打击问题,基于主飞行器和从飞行器架构提出了两种分布式协同制导方法,实现了所有飞行器最终对目标的同时命中。方法1在定义协调变量的基础上,通过对所选协调变量的一致性协同控制使从飞行器状态同步于主飞行器状态。方法2提出了分布式观测器对主飞行器的状态进行准确估计,各从飞行器通过跟踪观测的主飞行器状态信息实现命中时间的一致。理论分析表明,两种方法都可保证多飞行器同时命中目标。仿真结果验证了所提方法的正确性和有效性。     

带多充液圆柱贮箱航天器刚-液耦合动力学研究

文中以在低重环境下带多充液圆柱贮箱刚性航天器中刚-液耦合方程的建立和求解为主要研究目的。推导航天器中充液圆柱贮箱内任意点的牵连运动方程,根据壁面边界条件给出了贮箱内液体牵连晃动势的表达式;利用第二类边界条件下的傅立叶-贝塞尔级数展开法对低重力环境下的弯曲自由液面处的复杂动力学边界条件进行处理,建立以液体相对晃动势的模态坐标和晃动波高的模态坐标为状态向量的液体耦合晃动力学方程,通过积分分别得到了耦合晃动力和耦合晃动力矩的解析式;运用准坐标系下的拉格朗日方程建立以航天器主刚体姿态坐标和轨道坐标为状态向量的刚体耦合运动动力学方程,进一步联立上述耦合方程得到航天器整体系统的刚-液耦合动力学状态方程;最后,编制出适用于带多充液圆柱贮箱航天器内刚-液耦合动力学计算的模块化计算程序,通过计算实例验证所编程序的准确性的同时,研究了携带多充液箱航天器系统贮箱布局、外激励方式对航天器刚-液耦合系统动力学特性的影响。     

光学遥感卫星微振动抑制方法及关键技术

针对光学遥感卫星面临的微振动对成像质量影响的问题,对微振动抑制设计方法和关键技术进行了论述。首先对动量轮、控制力矩陀螺、扫摆机构等主要扰动源的机理和特征进行分析,然后从传递路径设计、微振动源抑制、降低有效载荷敏感性三个方面介绍了微振动抑制方法,最后结合遥感卫星的研制过程给出了微振动抑制设计的实例。     

An overview of infrared thermography techniques used in large wind tunnels

Infrared thermography (IRT) is used at Onera in large facilities for boundary layer visualization and for heat flux assessment. Modern IR cameras and insulating paints enable efficient visualization of the laminar/turbulent transition region. This technique is now applied in large transonic test facilities. Heat flux assessment is one of the main purposes of hypersonic tests. It is done mainly with IRT and dedicated softwares, while sensors as thermocouples are used to check the reliability of IRT. A 1D data reduction method has been developed to provide the heat flux through temperature measurements. It takes into account thickness and curvature effects. The method has been recently improved to be used with steel models covered with an insulating paint, which provides a high emissivity. The temperature film is converted into a heat flux film, which is be used to extract the useful information. This requires image processing tools that relate every pixel to a point on the model. A new application of IRT is going on in the Onera's high enthalpy hypersonic wind tunnel F4. The camera is used in single-line scan mode because of the short duration of the run. The main difficulty comes from the flow, which is not transparent. The first trial to cope with this kind of optical pollution is encouraging.     

Hysteresis processes in the regular reflection↔Mach reflection transition in steady flows

Ernst Mach recorded experimentally, in the late 1870s, two different shock-wave reflection configurations and laid the foundations for one of the most exciting and active research field in an area that is generally known as Shock Wave Reflection Phenomena. The first wave reflection, a two-shock wave configuration, is known nowadays as regular reflection, RR, and the second wave reflection, a three-shock wave configuration, was named after Ernst Mach and is called nowadays Mach reflection, MR.A monograph entitled Shock Wave Reflection Phenomena, which was published by Ben-Dor in 1990, summarized the state-of-the-art of the reflection phenomena of shock waves in steady, pseudo-steady and unsteady flows.Intensive analytical, experimental and numerical investigations in the last decade, which were led mainly by Ben-Dor's research group and his collaboration with Chpoun's, Zeitoun's and Ivanov's research groups, shattered the state-of-the-knowledge, as it was presented in Ben-Dor (Shock Wave Reflection Phenomena, Springer, New York, 1991), for the case of steady flows. Skews's and Hornung's research groups joined in later and also contributed to the establishment of the new state-of-the-knowledge of the reflection of shock waves in steady flows.The new state-of-the-knowledge will be presented in this review. Specifically, the hysteresis phenomenon in the RR↔MR transition process, which until the early 1990s was believed not to exist, will be presented and described in detail, in a variety of experimental set-ups and geometries.Analytical, experimental and numerical investigations of the various hysteresis processes will be presented.     

Modern helicopter rotor aerodynamics

The helicopter rotor wake is among the most complex fluid dynamic structures being three dimensional and in many cases unsteady. The wake begins at the blade(s) where the flow can be transonic near the blade tip and undergo compressible dynamic stall. Farther down in the wake, the flow is essentially incompressible. Moreover, the rotor blades undergo complex unsteady motions because of the necessity to balance moments; they are elastic as well. In this paper, the fundamental aeromechanics of the wake and the flow on the blade is discussed and the primary methods of analysis, computation, and experiment employed to uncover the physics of the rotor wake are described.     

Simulation methodology for high velocity impact in composite aircraft structures

The paper summarises the IMT Project HICAS on ‘High Velocity Impact of Composite Aircraft Structures’ which was concerned with developing a design methodology and FE simulation tools for predicting the high velocity impact response of composite aircraft structures. Achievements include measurement of high rate mechanical properties of three aircraft composite systems, development of new failure models for composites under high rate loads, implementation of models into commercial FE codes and code validation by simulation of impact in test structures.     

Scenarios of air transport reflecting capacity constraints at German airports

Forecasts of air traffic growth and their interpretation in terms of the requirement for future airport and air traffic system capacity have an important part to play in guiding decisions about transport system design. The complex issues involved are illustrated in this paper, which analyses possible growth scenarios for the particular case of Germany.     

Realization of an optimized wing camber by using formvariable flap structures

According to market research predictions, a large growth in the number of passengers as well as airfreight volume can be expected for the civil transport aircraft industry. This will lead to an increased competition between aircraft manufacturers. To stay competitive it will be essential to improve the efficiency of new generation of aircraft. Transonic wings of civil aircraft with their fixed geometry offer an especially large potential for improvement. Such fixed geometry wings are optimized for only one design point, characterized by the following parameters: altitude, mach number and aircraft weight. Since these vary permanently during the mission of the aircraft the wing geometry is rarely optimal. As aerodynamic investigations have shown, one possibility to compensate for this major disadvantage lies in the chordwise and spanwise differential variation of the wing camber for mission duration. This paper describes the design of a flexible flap system for an adaptive wing to be used in civil transport aircraft that allows both a chordwise as well as a spanwise differential camber variation during flight. Since both lower and upper skins are flexed by active ribs, the camber variation is achieved with a smooth contour and without any additional gaps. This approach for varying the wing's camber is designed to be used for replacement and enhancement of a given flap system. In addition, the kinematics of the rib structure allows for adaptation of the profile contour to different types of aerodynamic and geometric requirements.