飞行器智能设计愿景与关键问题

未来飞行器正朝着多元化、无人化和智能化的方向发展，高超声速、超隐身和变体等新型飞行器不断涌现。而传统飞行器解耦分拆的设计方法越来越难以满足未来飞行器综合性能全面提升的要求，只有通过整体化设计才能充分发掘飞行器的潜能。通过分析传统飞行器设计中存在的问题，提出满足全生命周期要求的飞行器智能设计体系理念，利用知识库的构建将智能赋予飞行器平台系统设计、制造生产和运维这3个阶段，并通过数字孪生技术进行飞行器全生命周期的仿真、分析和预测，以对飞行器设计、运行等数据进行更新，使该体系形成闭环。就飞行器智能设计体系中需要的关键技术及涉及的科学问题等进行了讨论，并给出了未来发展方向以供参考。     

基于知识图谱和自动机器学习的软件缺陷预测

不稳定和召回率低效的软件缺陷预测模型难以在行业领域应用，为解决稳定和高效各项性能评价指标的软件缺陷预测模型在工程实践应用的问题，提出了一种基于知识图谱和自动化机器学习的软件缺陷预测方法AutoKGGAS，首先获取软件缺陷预测模型数据，对知识建模、知识获取、知识融合、知识储存与知识计算等知识图谱构建技术研究，实现知识图谱推荐优质软件缺陷预测模型作为自动化搜索的热启动输入条件，根据不同的软件缺陷预测评价指标，优化不同最佳的模型结构.其次实证研究采用NASA开源数据集实验对象和六种性能评价指标，实验结果表明， AutoKGGAS自动化软件缺陷预测模型在不同数据集不同评价指标方面，性能优于知识图谱推荐的传统经典软件缺陷预测模型.自动化软件缺陷预测模型为航天软件缺陷预测辅助代码审查测试提供了原型，在工程实践应用方面具有重要的意义.     

一种基于元路径拥塞模式挖掘的移动对象位置预测方法

路网上移动对象位置预测是许多位置相关服务的基础。目前移动对象位置预测方法没有充分考虑到轨迹数据中所蕴含的道路拥塞信息,而路网上的道路拥塞状态对移动对象的位置更新会产生巨大影响。提出基于元路径拥塞模式挖掘的方法(Meta-congestion-pattern mining,MCPM)。在离线挖掘阶段,从历史轨迹的频繁路径(元路径)的紧集中挖掘当地的拥塞模式,并对运动模式进行建模,其中采用基于k均值的聚类算法解决数据稀疏性问题。在线预测阶段根据挖掘的拥塞模式和运动模式依概率进行预测。最后通过理论分析和实验验证得出了算法的有效性,与相同条件下的精度预测(WhereNext,WN)方法相比,平均预测准确性提高了近20%,预测时间平均缩短了近50%。     

Atmospheric reentry hemisphere prediction for prograde orbits using logical disjunction

A unique logic-based algorithm for atmospheric reentry hemisphere prediction is presented for spacecraft in low-eccentricity, prograde low Earth orbits at altitudes of 300 km and lower. Using two-line element (TLE) data for initial orbit conditions, coupled with coarse estimates for spacecraft aerodynamic characteristics, the algorithm relies on logical disjunction operations based on a dual analysis of histogram and two-weighted Gaussian probability density function (PDF) fits of predicted reentry latitude data. The algorithm requires the execution of a series of parametric simulations to determine the reentry hemisphere for variations in spacecraft aerodynamic coefficients and drag reference area. When implemented, the algorithm yields accurate hemisphere predictions on average 15 days from reentry as demonstrated by historical reentry cases from 1979 to 2018. All reentry cases were selected to demonstrate the algorithm’s ability to deliver accurate reentry hemisphere predictions for spacecraft with varying physical size and mass, and reentering during different periods of solar cycle activity.     

基于图像识别的机械振动信号特征提取与寿命预测方法研究

滚动轴承作为许多机械设备的关键组件,被广泛应用于机械制造、航空航天等领域,其健康状态直接影响了相应设备的剩余寿命,因此在设备故障预测与健康管理(Prognostics and Health Management, PHM)领域,滚动轴承寿命预测具有很高的研究价值。目前基于数据驱动的轴承寿命预测方法主要利用特征提取并构造健康因子(Health Indicator, HI),然而在这一过程中特征的选择与融合依然依赖于专家先验知识,并且健康因子也很难从复杂的时序数据中进行提取。因此,提出了一种新型的数据驱动寿命预测算法,在特征提取方面,通过连续小波变换(Continuous Wavelet Transform,CWT)将传感器振动信号转换为时频谱图,再通过深度残差网络(Deep residual network, ResNet)结合时空卷积网络(Temporal Convolutional Network, TCN)将时频谱图中的时域频域特征构造成为健康因子,最后完成剩余寿命预测。本研究在PRONOSTIA数据集上与现有的数据驱动算法进行了对比,证明了该算法可以更准确地完成剩余寿命预测。     

A progressive approach to predict shot peening process parameters for forming integral panel of Al7050-T7451

In this paper, a progressive approach to predict the multiple shot peening process parameters for complex integral panel is proposed. Firstly, the invariable parameters in the forming process including shot size, mass flow, peening distance and peening angle are determined according to the empirical and machine type. Then, the optimal value of air pressure for the whole shot peening is selected by the experimental data. Finally, the feeding speed for every shot peening path is predicted by regression equation. The integral panel part with thickness from 2 mm to 5 mm and curvature radius from 3200 mm to 16000 mm is taken as a research object, and four experiments are conducted. In order to design specimens for acquiring the forming data, one experiment is conducted to compare the curvature radius of the plate and stringer-structural specimens, which were peened along the middle of the two stringers. The most striking finding of this experiment is that the outer shape error range is below 3.9%, so the plate specimens can be used in predicting feeding speed of the integral panel. The second experiment is performed and results show that when the coverage reaches the limit of 80%, the minimum feeding speed is 50 mm/s. By this feeding speed, the forming curvature radius of the specimens with different thickness from the third experiment is measured and compared with the research object, and the optimal air pressure is 0.15 MPa. Then, the plate specimens with thickness from 2 mm to 5 mm are peened in the fourth experiment, and the measured curvature radius data are used to calculate the feeding speed of different shot peening path by regressive analysis method. The algorithm is validated by forming a test part and the average deviation is 0.496 mm. It is shown that the approach can realize the forming of the integral panel precisely.     

飞机封闭腔室减重降噪优化方法

噪声水平是现代飞机封闭腔室设计的重要指标,设计中单纯地对壁板进行加肋处理虽能显著降低噪声但会大大增加结构质量,为此对由封闭腔室构成的结构-声耦合系统进行了减重降噪优化研究。基于结构-声耦合有限元模型,利用有限元软件ACTRAN计算了频谱加载时舱内的声压响应。通过试验对简化处理及数值计算进行了验证,并修正了相关模型参数。为了降低结构质量,以加强肋为边界对舱门壁板进行了分区,通过对各个区域壁板厚度及肋条截面积的优化设计,使系统动刚度分配更趋合理,降低了声辐射能量以及结构-声腔的耦合性,从而实现了在满足噪声约束条件下减轻结构质量的目标。本文的工作对实际工程中由加肋壁板所构成的类似结构的减重降噪设计有着较好的工程指导价值。     

Orbit determination and prediction of GEO satellite of BeiDou during repositioning maneuver

In order to establish a continuous GEO satellite orbit during repositioning maneuvers, a suitable maneuver force model has been established associated with an optimal orbit determination method and strategy. A continuous increasing acceleration is established by constructing a constant force that is equivalent to the pulse force, with the mass of the satellite decreasing throughout maneuver. This acceleration can be added to other accelerations, such as solar radiation, to obtain the continuous acceleration of the satellite. The orbit determination method and strategy are illuminated, with subsequent assessment of the orbit being determined and predicted accordingly. The orbit of the GEO satellite during repositioning maneuver can be determined and predicted by using C-Band pseudo-range observations of the BeiDou GEO satellite with COSPAR ID 2010-001A in 2011 and 2012. The results indicate that observations before maneuver do affect orbit determination and prediction, and should therefore be selected appropriately. A more precise orbit and prediction can be obtained compared to common short arc methods when observations starting 1 day prior the maneuver and 2 h after the maneuver are adopted in POD (Precise Orbit Determination). The achieved URE (User Range Error) under non-consideration of satellite clock errors is better than 2 m within the first 2 h after maneuver, and less than 3 m for further 2 h of orbit prediction.     

低排放燃烧室NO_x排放试验及预测方法研究

为了研究中心分级贫油低排放燃烧室的排放特性和排放预测方法,针对一个低排放头部方案,在单头部燃烧室试验件上,在不同的温度、压力、油气比、供油模式和分级比条件下,测量其排放性能。以Lefebvre排放经验预测公式为基础,采用经验分析方法拟合排放试验数据,归纳出适用于本头部方案的排放预测公式。表征预测好坏的判定系数R2在小工况下和大工况下分别为0.95和0.93,表明预测结果与试验结果符合度较好。小工况和大工况排放特性不同,对仅预燃级喷油的小工况工作模式,NO_x排放主要受化学恰当燃烧温度和预燃级局部当量比的影响;对预燃级和主燃级同时喷油的大工况工作模式,NO_x排放主要受燃烧区温度和主燃级燃油比例的影响。     

基于流管试验的管道声传播预测

通过平板声衬流管试验，测试了管道内无流动和有流动下不同入射声波频率的管道壁面复声压，并基于试验模型与数据分别开展了二维和三维管道声传播预测，将试验测量结果与预测结果进行了对比。结果表明:二维和三维的预测结果非常吻合，尤其是在无流动条件下；在不同流动条件和不同频率下，声传播预测给出了与试验数据较为吻合的结果，壁面声压级的趋势与试验结果一致，基本验证了管道声传播预测模型的准确性；对比不同流动条件和频率点，有流动下预测的壁面声压级的误差比无流动更大，低频下预测的壁面声压级的误差比高频更大。