基于TTE的改进加权轮询调度算法

在时间触发以太网(TTE)中,TT消息优先级最高,RC消息只能在TT消息调度的离散时间片内传输,因此,TT消息离线调度表的设计会对RC消息调度产生一定影响。针对这一问题,提出了基于最优时间片的改进加权轮询(MWRR)调度算法。首先,通过TT消息约束条件限制获得TT消息离线调度表,进而得到保证RC消息较大资源利用率的时间片信息;其次,在离散时间片对不同类型RC消息进行调度,并运用网络演算方法对其最坏端到端延迟进行分析;最后,通过实验仿真证实了本文算法不仅具有较低的复杂度和较好的公平性,保证了实际应用中算法的可行性,而且在时延性方面均优于先到先得(FIFO)、优先级(PQ)和加权轮询(WRR)调度算法。     

缝式机匣处理及其轴向偏转角对跨声速轴流压气机稳定性的改善

以NASA Rotor 67为研究对象,采用非定常数值模拟方法,开展缝式机匣处理及其轴向偏转角对跨声速轴流压气机稳定性改善的研究,并且揭示缝轴向偏转角的变化对其扩稳能力和扩稳机理的影响。结果表明,不同轴向偏转角的缝均提高了压气机的稳定裕度,但是均降低了压气机的峰值效率。反叶片角向缝获得的稳定裕度改进量和峰值效率改进量分别约为24.22%和-1.19%。随着缝的轴向偏转角由负向正变化,缝的扩稳能力逐渐减弱,缝带来的峰值效率损失亦逐渐减少。流场分析表明,实壁机匣时,压气机的失速类型为叶顶堵塞形式的突尖型失速。通过感受叶片通道和叶顶吸/压力面的压差,反叶片角向缝对泄漏流进行抽吸和射流作用,一方面消除了泄漏流及其泄漏涡扩散带来的负面影响,另一方面激励了泄漏流,提高了泄漏流的速度,降低了泄漏流的总压损失,增强了叶片的做功能力。随着缝的轴向偏转角由负向正变化,由于缝能够利用的叶顶载荷从两个减成一个,缝的抽吸和射流作用均减弱,泄漏流的速度降低,泄漏流的总压损失提高,叶片的做功能力减弱,这就导致缝的扩稳能力减弱。     

永磁驱动重构型车载充电机三相DC/DC变流器的研究

提出了一种新型永磁驱动重构型车载充电机三相DC/DC变流器集成系统。该集成系统将永磁驱动的电机绕组和DC/AC逆变器重构成车载充电机实现电动汽车驱动-充电的集成,具有空间利用率高、充电快速和可靠性高等特点。分析了集成系统的结构和工作原理,推导了充电系统的三相DC/DC变换器数学模型。在此基础上,利用MATLAB/Simulink仿真软件搭建了驱动-充电集成系统仿真模型,对同步脉宽调制(PWM)控制和交错PWM控制策略进行仿真研究,分析对比了交流侧电压电流、直流侧电机绕组电感电流和直流侧电压波形。仿真结果表明,与交错PWM控制策略相比,同步PWM控制策略下该新型结构充电系统具有更好的运行性能。     

面向风险均衡的AFDX虚拟链路路径寻优算法

为确保综合模块化航空电子系统的安全性需求能够在全双工交换式以太网中得到一致性保证,提出了一种面向风险均衡的路径规化（RBPP）算法,以满足各航电功能间的安全隔离要求,同时分散风险,避免局部物理链路的风险集中,提高系统安全性。以民机失效状态类别划分为基础,建立了航电功能、分区、端系统、虚拟链路（VL）风险模型;RBPP以均衡各物理链路风险为目标,同时综合考虑网络实时性、链路负载能力等因素,采用粒子群算法进行优化目标求解。利用仿真优化方法对RBPP算法进行了实现,在典型工业航空电子全双工交换式以太网（AFDX）网络架构及A380AFDX网络架构下进行仿真分析,结果显示多播VL的简化处理的会使网络风险增加;在1 000条VL配置下与负载均衡（LB）算法和最短路径（SP）算法进行了分析对比,结果显示RBPP算法在满足各航电功能间的隔离需求的同时,链路风险均衡能力在两种网络拓扑下分别比负载均衡算法提高了10.7%和23.4%,比最短路径算法分别提高了35.4%和47.9%。     

模型切换MRAS技术在感应电机速度辨识中的应用研究

通过分析现有基于模型参考自适应系统(MRAS)估算电机转速的原理和不足,提出一种基于滞环切换的MRAS方案辨识电机转速。理论和试验结果表明该方案具有良好的静、动态性能和较好的鲁棒性。     

发电电动机转子不同磁极引线的应力分布与疲劳特性对比研究

磁极极间连接线是发电电动机转子的关键部件,合理的引线方式可有效避免大型发电电动机运行过程中由于工况频繁切换引起的磁极连接线熔断等故障。针对该问题,采用有限元法对3种典型磁极引线连接方式进行了分析,详细计算额定转速为300 r/min和500 r/min的2台电机的3种磁极连接结构的应力和疲劳情况。结合疲劳分析结果,指出适用于高转速发电-电动机磁极连接线典型结构,并给出发电-电动机磁极连接线设计方面的建议。研究成果可为抽水蓄能电站发电电动机极间连接线选型及运行维护提供支持。     

精密机电设备寿命评估方法

寿命评估技术既是确保设备安全、可靠运行的核心和关键,也是设备定寿、延寿的重要依据。从工程的视角,根据精密机电设备的工作状态,将精密机电设备分为新研设备、工作态设备、贮存态设备3类,分析这3种状态机电设备的特点及可以获取的信息资源,进而对新研设备、工作态设备、贮存态设备的寿命评估方法进行了系统研究和评述,对存在的问题及未来发展趋势进行了分析和展望。鉴于难以对复杂精密机电设备的机理进行建模,数据驱动的寿命估计已成为当前研究的主流,本文在3种状态机电设备分类的框架下,重点分析了数据驱动寿命估计的研究动态。     

The Rotation and Interior Structure Experiment on the InSight Mission to Mars

The Rotation and Interior Structure Experiment (RISE) on-board the InSight mission will use the lander’s X-band (8 GHz) radio system in combination with tracking stations of the NASA Deep Space Network (DSN) to determine the rotation of Mars. RISE will measure the nutation of the Martian spin axis, detecting for the first time the effect of the liquid core of Mars and providing in turn new constraints on the core radius and density. RISE will also measure changes in the rotation rate of Mars on seasonal time-scales thereby constraining the atmospheric angular momentum budget. Finally, RISE will provide a superb tie between the cartographic and inertial reference frames. This paper describes the RISE scientific objectives and measurements, and provides the expected results of the experiment.     

Presolar Isotopic Signatures in Meteorites and Comets: New Insights from the Rosetta Mission to Comet 67P/Churyumov–Gerasimenko

Comets are considered the most primitive planetary bodies in our Solar System, i.e., they should have best preserved the solid components of the matter from which our Solar System formed. ESA’s recent Rosetta mission to Jupiter family comet 67P/Churyumov–Gerasimenko (67P/CG) has provided a wealth of isotope data which expanded the existing data sets on isotopic compositions of comets considerably. In this paper we review our current knowledge on the isotopic compositions of H, C, N, O, Si, S, Ar, and Xe in primitive Solar System materials studied in terrestrial laboratories and how the Rosetta data acquired with the ROSINA (Rosetta Orbiter Sensor for Ion and Neutral Analysis) and COSIMA (COmetary Secondary Ion Mass Analyzer) mass spectrometer fit into this picture. The H, Si, S, and Xe isotope data of comet 67P/CG suggest that this comet might be particularly primitive and might have preserved large amounts of unprocessed presolar matter. We address the question whether the refractory Si component of 67P/CG contains a presolar isotopic fingerprint from a nearby Type II supernova (SN) and discuss to which extent C and O isotope anomalies originating from presolar grains should be observable in dust from 67P/CG. Finally, we explore whether the isotopic fingerprint of a potential late SN contribution to the formation site of 67P/CG in the solar nebula can be seen in the volatile component of 67P/CG.     

Dust Evolution in Protoplanetary Discs and the Formation of Planetesimals

After 25 years of laboratory research on protoplanetary dust agglomeration, a consistent picture of the various processes that involve colliding dust aggregates has emerged. Besides sticking, bouncing and fragmentation, other effects, like, e.g., erosion or mass transfer, have now been extensively studied. Coagulation simulations consistently show that \(\upmu\mbox{m}\)-sized dust grains can grow to mm- to cm-sized aggregates before they encounter the bouncing barrier, whereas sub-\(\upmu\mbox{m}\)-sized water-ice particles can directly grow to planetesimal sizes. For siliceous materials, other processes have to be responsible for turning the dust aggregates into planetesimals. In this article, these processes are discussed, the physical properties of the emerging dusty or icy planetesimals are presented and compared to empirical evidence from within and without the Solar System. In conclusion, the formation of planetesimals by a gravitational collapse of dust “pebbles” seems the most likely.