Real-time onboard wind and windshear determination,part 2: Detection

This paper is concerned with windshear detection in connection with real-time wind identification (Ref. 1). It presents a comparative evaluation of two techniques, one based on the shear/downdraft factor and one based on the wind difference index. The comparison is done with reference to a particular microburst, that which caused the 1985 crash of Flight Delta 191 at Dallas-Fort Worth International Airport.The shear/downdraft factor has the merit of combining the effects of the shear and the downdraft into a single entity. However, its effectiveness is hampered by the fact that, in a real situation, the windshear is accompanied by free-stream turbulence, which tends to blur the resulting signal. In turn, this results in undesirable nuisance warnings if the magnitude of the shear factor due to free-stream turbulence is temporarily larger than that due to true windshear. Therefore, proper filtering is necessary prior to using the shear/downdraft factor in detection and guidance. One effective way for achieving this goal is to average the shear/downdraft factor over a specified time interval . The effect of on the average shear/downdraft factor is studied.     

Real-time onboard wind and windshear determination,part 1: Identification

Standard wind identification techniques employed in the analysis of aircraft accidents are post-facto techniques; they are processed after the event has taken place and are based on the complete time histories of the DFDR/ATCR data along the entire trajectory. By contrast, real-time wind identification techniques are processed while the event is taking place; they are based solely on the knowledge of the preceding time histories of the DFDR/ATCR data.In this paper, a real-time wind identification technique is developed. First, a 3D-kinematic approach is employed in connection with the DFDR/ATCR data covering the time interval preceding the present time instant. The aircraft position, inertial velocity, and accelerometer bias are determined by matching the flight trajectory computed from the DFDR data with the flight trajectory available from the ATCR data. This leads to a least-square problem, which is solved analytically every seconds, with / small.With the inertial velocity and accelerometer bias known, an extrapolation process takes place so as to predict the inertial velocity profile over the subsequent -subinterval. At the end of this subinterval, the extrapolated inertial velocity and the newly identified inertial velocity are statistically reconciled and smoothed. Then, the process of identification, extrapolation, reconciliation, and smoothing is repeated. Subsequently, the wind is computed as the difference between the inertial velocity and the airspeed, which is available from the DFDR data. With the wind identified, windshear detection can take place (Ref. 1).As an example, the real-time wind identification technique is applied to Flight Delta 191, which crashed at Dallas-Fort Worth International Airport on August 2, 1985. The numerical results show that the wind obtained via real-time identification is qualitatively and quantitatively close to the wind obtained via standard identification. This being the case, it is felt that real-time wind identification can be useful in windhsear detection and guidance, above all if the shear/downdraft factor signal is replaced by the wind difference signal (Ref. 1).This paper and its companion (Ref. 1) are based on Refs. 2–4.This research was supported by the Aviation Research and Education Foundation and by Texas Advanced Technology Program, Grant No. TATP-003604020.     

光电着降导引系统的跟踪和参数测量

分析和研究了CCD摄影测量算法的精确定位技术,建立了4个信标点空间位置坐标的数学模型,并推导出计算公式,该算法的特点是计算精度高,可实时计算空间目标的坐标位置,从而对空间目标精确定位,在航天、航空技术上有重要的用途.设计了一台直升机着降与回收的光电导引系统,利用2台红外CCD对在直升机两侧机身被半导体激光器照明的4个信标成像,通过对图像的处理和目标识别,提取出信标的位置和恣态信息.使用双摄影测量法模型实时计算出直升机相对于着降点的坐标.使用高性能的DSP系统,实时检测和跟踪双通道图像信号并显示出实验结果.模拟实验结果表明,在8～13m距离内,光电引导系统的距离测量精度达到±5cm,而角度测量精度达到±3°.     

某型机进近段高精度相对姿态实时测量技术

某型机在飞行训练过程中,进近段的二维相对姿态数据对于该型机安全着陆有着至关重要的作用。基于无线网络电台的双向数据传输系统能够实时获取进近段飞机相对理想着陆点的水平、垂直相对位置数据。通过上行链路上传着陆点的姿态数据,下行链路实时下传动动差分后的差分数据,最后在中心控制站进行二次数据处理。该技术获得的进近段二维相对姿态精度达到厘米级,满足飞行训练的需求。同时结合飞机显控数据以及视景图,以多角化动态关联的方式将实时获取的姿态数据等呈现给指挥员,更好地辅助指挥员进行着陆指挥工作。     

无人机着舰引导信息处理方法研究

针对远距理想着舰轨迹摆动幅度较大使得无人机难以跟踪的问题,提出了曲线拟合的方法,针对着舰雷达近距引导失效或引导精度不高的问题提出了近距多天线测距定位法,最后提出了远近距切换的方法。对保障无人机安全着舰、提高无人机重复作战能力提供了前瞻性的理论依据。     

一种基于mMIMO技术的应用落地实践

为应对移动通信业务量的迅猛增长,以及对信息传输的速率、时延、可靠性等各方面都提出了更高的要求,大规模多进多出(Massive MIMO,m MIMO)因其空间资源挖掘的独特优势而获得青睐与重视,可实现系统频谱和能量效率的极大化,已成为5G的关键技术之一。文章介绍了m MIMO的关键技术原理,提出了针对不同TR数的设备进行差异性部署的方法,同时介绍了m MIMO最关键的波束赋形技术的优化思路和详细案例,为后续打造低成本优质5G精品网络具有重要意义。     

惯性／DGPS精密进场着陆引导系统

为确保飞机精确直线飞越预定点上空并具备精密进场着陆引导能力 ,研制了机载惯性 /DGPS精密进场着陆引导系统。该系统通过综合技术将惯性导航系统与差分 GPS有效组合 ,不仅定位精度高、工作可靠 ,而且输出信息实时、连续 ;通过着陆引导轨迹及引导画面的精心设计 ,为飞行员提供图形化的、精确安全的进场着陆引导信息 ,引导飞机至决断高处 ,从而解决了飞机全天候尤其是在复杂气象条件的进场着陆引导问题。本文介绍了该系统的方案、组成、系统特点、技术难点以及试飞结果。试飞中飞行员反映该系统精度高 ,引导画面图形直观 ,操作简便 ,能满足复杂气象条件下的进场着陆引导要求     

Critical shimmy speed of nonswiveling landing-gear wheels subject to lateral loading

The paper presents a nonlinear model describing vibration of the landing gear relative to the fuselage. The model is intended to analyze the dynamic stability of nonswiveling main-gear wheels. The model is used to show that the lateral component of the fuselage speed has a significant effect on the critical shimmy speed __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 9, pp. 134–142, September 2006.     

A landing theorem for periodic dynamic rays for transcendental entire maps with bounded post-singular set

In this article, we present a landing theorem for periodic dynamic rays for transcendental entire maps which have bounded post-singular sets, by using standard hyperbolic geometry results.     

四十二年来登陆浙江的台风及其对杭州的影响

本文利用1949-1990年共四十二年有关历史台风资料，详细分析研究了登陆浙江台风的气候特征及其对杭州的影响，发现近十年来，尤其是八十年代中后期以来，登陆浙江的台风有增多的趋势.因此，台风对杭州的影响也呈上升趋势.从而加剧了杭州的台风灾害.作者提出了杭州抗台减灾的对策.