A unified approach to two types of evolutionary random response problems in engineering

Summary Response of structures to earthquake excitations and response of vehicles to road undulations are two typical evolutionary random problems in engineering. Both kinds of the evolutionary random excitations can be regarded as evolved from stationary random excitations, though through two utterly different ways. The former one may be obtained by filtering a stationary random process through a linear time-dependent system, while the latter one may result from nonlinear transformations of the argument of a stationary random process. However, the response problems due to both types of excitations have much in common. By introducing the concept of “evolutionary frequency response”, the expressions of the response evolutionary spectra for both problems can be obtained in a unified, concise way, similar to the input/output PSD relationship in a stationary random problem. For both the evolutionary random problems, the solution procedures are all the same, but the expressions for evolutionary frequency responses are different from each other. Moreover, the evolutionary frequency responses may be interpreted as transient responses of the system subject to certain deterministic evolutionary harmonic excitations. In this sense, an evolutionary random response problem can be reduced to a deterministic response problem. Based on the complex modal analysis, a unified approach to these two response problems is derived here. The method can be applied to any linear time-invariant systems, whether they are symmetrical or not, and whether they are classically damped or not. And the method might be hopefully applied to nonlinear systems, if the statistical linearization technique is accompanied. To the knowledge of the authors, this unified approach to two types of evolutionary random response problems is the first time reported in literature. Received 28 May 1996; accepted for publication 8 January 1997     

语音控制的四旋翼飞行器设计与实现

基于语音识别技术,设计了一套语音远程控制四旋翼飞行器的系统。使用LD3320语音处理芯片和STM32微处理器实现语音识别功能,采用NRF24L01将识别结果传输到飞行器。选用STM32作为四旋翼飞行器的主控芯片,采用六轴运动组件MPU6050、三轴数字罗盘HMC5583L等传感器对飞行器的姿态进行实时测量,再利用数字滤波器对姿态信息进行处理,然后采用四元数进行姿态解算,最后运用双闭环PID控制算法实现姿态控制的要求。测试结果表明,通过语音可以控制四旋翼的正常飞行及姿态变化,系统稳定可靠。     

大型民机试飞测试发展与挑战

飞行试验是对飞机的性能进行验证和确认的关键阶段,试飞测试是保障该阶段工作的重要内容;国内目前对于军机已拥有了成熟的测试技术、测试方法和可靠的测试设备,而对于民用飞机特别是大型民机的试飞测试目前还处在起步阶段;随着国家大飞机研制专项的不断推近,大型客机试飞测试需求逐步明确;从大型民机试飞测试需求和测试工作特点出发,对机载测试技术变革、遥测和数据处理技术等键技术在国外的最新发展和国内大型飞机的现状进行对比分析,可以看出我国民机试飞测试在网络化机载测试系统应用、遥测传输链路带宽、大数据快速处理等方面存在较大的挑战;在此基础上对应对挑战的发展策略和后续攻关的方向进行研究,可以为我国大型飞机特别是民机试飞测试技术的发展提供参考。      

Location and shape measurement using a portable fringe projection system

In this paper we present a portable fringe projection system developed for the measurement of the three-dimensional shape and position of complex aircraft parts. We describe the prototype instrument and processing algorithms designed, implemented, and tested during this study, and we discuss several applications throughout the lifecycle of the aircraft.     

飞机加强蒙皮在12.7 mm弹丸撞击下的变形与破坏

为了研究飞机蒙皮在12.7 mm标准机枪弹丸射击下的损伤,对3 mm厚LY-12 CZ材料的单蒙皮及其加筋板进行了模拟弹击试验。通过试验研究,建立了一个由高速气炮、弹体与弹托分离机构、连续位移激光测速装置和弹丸回收装置组成的系统并被有效地用于弹丸正撞击试验。通过对四边固支的3 mm厚蒙皮用12.7 mm直径弹丸进行速度约60~300 m/s的正撞击试验,结果表明,靶板从微小损伤到完全击穿;弹击造成的变形区有效直径随弹丸速度的增大呈幂指数趋势下降;弹击引起的变形深度随弹丸撞击速度的增加呈直线下降;靶板上的应变随弹丸速度的增加逐渐降低。弹丸剩余速度随弹丸撞击速度的增加呈直线上升。最后利用DYNA3D程序对单蒙皮及其加筋板进行了弹击数值模拟,模拟结果与弹击试验结果较吻合。     

Resolving applied-mechanics problems in creating Antonov transport aircraft

Some problems of flight mechanics encountered in creating transport aircraft designed by O. K. Antonov are described. To solve these problems, the Antonov ASTC used equations that describe the motion of aircraft under diverse conditions, including during cargo airdrop, under servotab control, and with multileg landing gears. The results of the theoretical and experimental studies as well as the practical work carried out to make aircraft structures of polymer composite materials are presented. Approaches to and a sequence of resolving problems of designing low-, medium-, and high-loaded structures are outlined. Photos of the most typical composite components and structures are shown Dedicated to the 100th birthday of O. K. Antonov and to the 60th anniversary of the O. K. Antonov Aeronautical Scientific and Technical Complex __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 10, pp. 3–12, October 2006.     

再入飞行器的制导工具误差分段补偿技术研究

针对再入飞行器的惯性仪表误差模型在地面测试环境下和真实飞行环境下不一致的特点，提出了按照过载变化的大小对其误差模型进行分段辨识和分段补偿的方法，以补偿飞行器高速再入过程中的制导工具误差。最后通过计算机仿真试验验证了此方法的正确性，为实际应用提供了理论依据。     

Electric Charging of Soot Particles in Aircraft Engine Exhaust Plumes

A physico-mathematical model is developed and the variation of the charge on soot particles interacting with positive and negative ions in the exhaust of modern subsonic aircraft is simulated numerically. The calculations are based the gas dynamic system of equations for an axisymmetric turbulent isobaric jet. The system is supplemented with the thermodynamic relations, kinetic equations, and equations for the turbulent viscosity. Ion and neutral and charged soot particle concentration distributions over the exhaust jet on the ground and under cruising flight conditions are obtained.     

Dynamics of aerospace vehicles at very high altitudes

Some basic questions of the flight mechanics of aerospace vehicles at very high altitudes are investigated and in some cases reviewed. In particular those of the spacecraft trajectories are considered along which the aerodynamic actions take place in a range of the Knudsen number between transition and free molecular flow. A recent physico-mathematical model is adopted in the evaluation of the aerodynamic and heat transfer coefficients. The stability characteristics are discussed of two reference vehicle configurations for which the time histories are also calculated relative to significant equilibrium conditions. In the final section of the paper the initial step of an aeroassisted orbit transfer is considered in order to evaluate the constraints due to the aerodynamic heating on this manoeuvre.Si studiano alcune questioni fondamentali della meccanica del volo di veicoli aerospaziali a quote molto elevate. Si considerano, in particolare, quei tratti delle traiettorie lungo i quali le azioni aerodinamiche si esplicano in un campo di numeri di Knudsen tra la transizione ed i flussi di molecole libere. Si adotta un recente modello fisico-matematico per calcolare i coefficienti aerodinamici e di scambio termico. Dopo aver discusso le caratteristiche di stabilit`a per due configurazioni di velivoli di riferimento, se ne calcolano le leggi orarie a partire da condizioni di equilibrio significative. Il lavoro termina con lo studio di un traferimento orbitale aeroassistito al fine di valutare i limiti a questa manovra dovuti al riscaldamento aerodinamico.     

飞机壁板结构的动特性分析与计算

本文以“修正的变分方法”为基础推导了一种新的飞机壁板结构动力分析方法.该法不需要将结构理想化或离散化而直接对复杂的飞机壁板结构进行特征分析或响应分析,方法的实质是将一个复杂结构划分为一个参考结构和一些附加结构,而把这些附加结构视为作用在该参考结构上的广义力,这些广义力由系统能量的变分求得.同时,本文还将有限条法与各向异性壳法相结合,发展了新的有限条分析方法.文中通过固有频率的计算,对这种方法的计算精度和应用场合等问题进行了讨论.