基于光纤双环网的高精度时频同步技术研究

本文介绍了一种基于光纤双环网的时频同步技术设计方法,针对时频设备协同使用时如何获得高精度同步指标这一问题提出了一种设计思路。以系统时间源使用北斗/GPS/GLONASS,本系统同步精度优于5E-13,频率稳定度优于5E-13@1d;以UTC(BIRMM)输出的TOD+1PPS做系统时间源,本系统同步精度优于4E-13,频率稳定度优于6E-14@1d。本方案提出的方法原理简单,系统可根据使用情况进行裁剪,相比卫星双向等手段成本低廉,适合在时频同步领域推广。     

发动机喷管喉衬烧蚀及热结构工程计算

给出了一种理论模型和基本计算方法。采用有限元法对某固体火箭发动机喉衬结构的烧蚀量、瞬态温度场和应力场进行了理论计算,计算结果与实测值比较一致,喉部直径实测值与计算值相对误差约为2％。     

基于FPGA的永磁同步电机电流环带宽拓展的比较研究

分析了电流环的数学模型,导出了电流环闭环传递函数,得出带宽的大小与系统延时的大小成反比。传统基于数字信号处理器的PMSM电流环的延时比较大,转速变化越大,带宽的影响越明显,而采用现场可编程门阵列FPGA控制的PMSM,可以将电流环的延时缩小一倍,进而改善速度环的响应能力并试验验证理论分析。     

A transient bulk flow model with circular whirl motion for rotordynamic coefficients of annular seals

Bulk flow model with perturbation simplification has been used to calculate rotordynamic coefficients in annular seals which have significant influences on the dynamic behavior of rotors in turbomachinery. In this work, a transient bulk flow model with arbitrary rotor motion is developed, and the boundary conditions and friction factor in the model are calibrated with steady Computational Fluid Dynamics (CFD) analysis. The numerical solution scheme is developed based on the finite element method to obtain the transient reaction force in the seal clearance. With a periodic circular rotor orbit, the transient forces at multiple whirling frequencies are used to evaluate the rotordynamic coefficients. The leakage flowrate of CFD analysis has good agreement with experimental results and the calibrated parameters in bulk flow model are dependent on operating conditions. Although CFD calibration improves the accuracy of the perturbed bulk flow model, the direct damping is overestimated and the cross-coupled damping is underestimated. Compared with the perturbed model, the predictions of the transient bulk flow model are more agreeable with the experiment.     

煤基合成油燃烧性能试验研究

为了考查煤基合成油的燃烧性能,在航空发动机主燃烧室试验台上采用同一个全环燃烧室试验件,对燃用RP3航空煤油和煤基合成油进行燃烧室性能对比试验。试验结果表明:燃用RP3航空煤油和煤基合成油时所测区间火焰筒的壁温分布无较大区别;在同一试验状态下,燃用RP3航空煤油和煤基合成油的燃烧室出口平均温度和燃烧效率无较大区别,燃烧室出口温度分布热点位置相同,热区分布一致,OTDF相差不大;燃用RP3航空煤油和煤基合成油在相同的主燃烧室起动状态下均可正常起动。     

Recent Progress of Fengyun Meteorology Satellites

After nearly 50 years of development, Fengyun (FY) satellite ushered in its best moment. China has become one of the three countries or units in the world (China, USA, and EU) that maintain both polar orbit and geostationary orbit satellites operationally. Up to now, there are 17 Fengyun (FY) satellites that have been launched successfully since 1988. There are two FY polar orbital satellites and four FY geostationary orbit satellites operate in the space to provide a huge amount of the earth observation data to the user communities. The FY satellite data has been applied not only in the meteorological but also in agriculture, hydraulic engineering, environmental, education, scientific research and other fields. More recently, three meteorological satellites have been launched within the past two years. They are FY-4A on 11 December 2016, FY-3D on 15 November 2017 and FY-2H on 5 June 2018. This paper introduces the current status of FY meteorological satellites and data service. The updates of the latest three satellites have been addressed. The characteristics of their payloads on-boarding have been specified in details and the benefit fields have been anticipated separately.      

非定制超声波清洗机清洗效率提升方法

为提高非定制超声波清洗机金属零件清洗效率,在不对清洗机本身进行改造的前提下,根据超声波清洗的原理,以清洗介质、清洗温度、清洗时间及工作液面等工艺要素为分析对象,摸索有效的工艺方法和参数.同时,研究声场分布和声强衰减的基本规律,获得有利于声波传播的零件摆放方法,提高清洗效率.本文的研究为提升金属零件的超声波清洗效率提供了...     

基于域对抗门控网络的变工况刀具磨损精确预测方法

刀具磨损的精确预测对保证零件加工质量、提高生产效率和降低制造成本具有重要作用。在实际加工过程中,切削参数、刀具几何参数、刀具材料等工况复杂多变,工况信息和刀具磨损量对监测信号的耦合作用为刀具磨损的精确预测带来了很大挑战。针对以上问题,提出了一种基于域对抗门控网络（DAGNN）的变工况刀具磨损精确预测方法。引入工况分类网络并利用无磨损量标签样本,通过域对抗和门控过滤机制自适应地从不同工况的原始监测信号中提取表征刀具磨损且对工况变化不敏感的关键信号特征。对信号特征提取网络和刀具磨损预测网络进行迭代优化,从而实现变工况刀具磨损的精确预测。实验结果表明：相比已有的方法,本文方法能够利用少量带磨损量标签的目标工况样本实现刀具材料和刀具直径变化情况下的刀具磨损量精确预测,预测精度大幅提高。     

ADS-B统计数据的位置导航不确定类别质量分析

为实现广播式自动相关监视(ADS-B)航迹与雷达航迹的高质量融合,必须对ADS-B航迹和雷达航迹数据质量进行分析。在分析实际ADS-B航迹数据的基础上,提出以航路为参考基准验证ADS-B航迹数据精度及完好性的方法。根据ADS-B报文中的位置导航不确定类别(NUCp)值,统计航迹点与航路中心线的水平偏差并将其作为位置实际误差,运用分位数-分位数图法对位置实际误差进行正态分布检验,得出置信水平为99%的实际误差置信区间,即在不同NUCp值下可信赖的位置误差范围。实验结果表明,在采用加权平均法进行航迹融合时,与传统权重分配相比,对于NUCp值为5或6的ADS-B航迹数据可增大权重,而对于NUCp值为7的数据则应减小权重。