共查询到20条相似文献,搜索用时 701 毫秒
1.
针对不同类型导航传感器的采样率不同步,提出了一种基于状态方程多尺度变换的组合导航系统信息异步融合算法。首先,建立组合导航系统基于最高采样率下的状态方程;然后,将状态方程分解到不同的尺度上,进而建立基于不同尺度上的多个状态方程及其对应的量测方程;最后,建立基于不同尺度上的全局最优信息融合算法。仿真结果验证了该算法能有较好的实时性和融合精度。 相似文献
2.
3.
王富朝 《航空标准化与质量》1999,(5)
概述了西飞公司在飞机工艺装备研制中应用CAD/CAM/CAT技术所配置的软硬件环境,以及工装设计数据传递流程的情况。介绍了公司在工装设计、制造、安装、检测方面实施CAD/CAM/CAT技术后所取得的技术、经济成果,同时还介绍了有关工装方面的技术贮备及软件开发的情况。 相似文献
4.
Sharawi M.S. Akos D.M. Aloi D.N. 《IEEE transactions on aerospace and electronic systems》2007,43(1):227-238
The carrier-to-noise density ratio (C/N0) is considered an important parameter describing the GPS receiver performance. This paper compares the performance of two popular coarse-acquisition (C/A) C/N0 algorithms appearing in literature: the variance summing method (VSM) (Psiaki et al., 2003, Psiaki, 2001), and the power ratio method (PRM) (Van Dierendonck, 1996, Sayre, 2003), in terms of their estimates in 1) additive white Gaussian noise (AWGN), 2) narrowband continuous wave interference (CWI), 3) their response to quantization and saturation effects, and their 4) dynamic range. The algorithms were implemented as a part of a software receiver. Two LI GPS data sets are examined; one was obtained from a GPS raw data collection setup, while the other was obtained from a GPS signal simulator. The collected set was stored with almost constant C/N0 level while the simulated one contained variable C/N0 levels. The effect of adding AWGN on the C/N0 estimate was directly proportional with the noise power. The C/N0 estimates suffered more when the CWI frequency was closer to the IF of the receiver. The PRM suffered from saturation at higher C/N0 levels. The VSM showed good tracking at high C/N0 levels and better immunity to limited quantization levels, while its C/N0 estimate suffered from rapid fluctuations in power levels when sudden power steps occurred 相似文献
5.
6.
7.
利用高压差示扫描量热法(DSC)研究了含不同燃速调节剂(亚铬酸铜、草酸铵、碳纤维)的RDX/AP/HTPB推进剂热分解性能,研究发现,调速剂对推进剂燃速的影响与其对推进剂主要组分(RDX、AP和HTPB)峰温、推进剂初始放热量的影响密切相关,燃烧催化剂亚铬酸铜和碳纤维使RDX,AP的分解峰温降低,使推进剂的初始分解阶段放热量增大,分解放热峰增多,故导致推进剂燃速增加,而草酸铵使RDX的分解峰温升高,使推进剂的初始分解阶段放热量降低,所以导致推进剂燃速降低。 相似文献
8.
《Aerospace Science and Technology》1999,3(2):107-110
The Giotto Radio-Science Experiment (GRE) was designed to measure the reaction of the spacecraft to its close encounters with the comets P/Halley and P/Grigg-Skjellerup. Radio frequency and signal level data of the downlink carrier signals at X- and S-band, recorded at many ground-based tracking stations, were used for the previous analysis. These signals were transmitted in “one-way” mode (Giotto - Earth) during a few hours about closest approach and in “two-way” mode (Earth - Giotto - Earth) during the adjacent pre-encounter and post-encounter tracking intervals. Unexpectedly large differences for the comet-induced Doppler shift residual of the Giotto signal were implied by the one-way versus the two-way data, a discrepancy which was attributed to instabilities of the on-board oscillator during the encounter. The analysis to date assumed that the two-way Doppler shift residual is exactly twice the one-way residual. As shown in this note, this is not generally the case. The spacecraft's change in velocity, which is measured in a rotating (non-inertial) system, must first be determined in the non-rotating frame by applying the appropriate coordinate transformation. The GRE results should be reinvestigated to account for this previously unrecognized effect. 相似文献
9.
R. Karrer P. Bochsler C. Giammanco F. M. Ipavich J. A. Paquette P. Wurz 《Space Science Reviews》2007,130(1-4):317-321
Using the Mass Time-of-Flight Spectrometer (MTOF)—part of the Charge, Elements, Isotope Analysis System (CELIAS)—onboard the
Solar Heliospheric Observatory (SOHO) spacecraft, we derive the nickel isotopic composition for the isotopes with mass 58,
60 and 62 in the solar wind. In addition we measure the elemental abundance ratio of nickel to iron. We use data accumulated
during ten years of SOHO operation to get sufficiently high counting statistics and compare periods of different solar wind
velocities. We compare our values with the meteoritic ratios, which are believed to be a reliable reference for the solar
system and also for the solar outer convective zone, since neither element is volatile and no isotopic fractionation is expected
in meteorites. Meteoritic isotopic abundances agree with the terrestrial values and can thus be considered to be a reliable
reference for the solar isotopic composition. The measurements show that the solar wind elemental Ni/Fe-ratio and the isotopic
composition of solar wind nickel are consistent with the meteoritic values. This supports the concept that low-FIP elements
are fed without relative fractionation into the solar wind. Our result also confirms the absence of substantial isotopic fractionation
processes for medium and heavy ions acting in the solar wind. 相似文献
10.
11.
基于Pro/Engineer的Pro/toolkit二次开发技术研究 总被引:7,自引:1,他引:7
着重讲述了利用Pro/toolkit开发包,在针对Pro/Engineer2001进行二次开发CAD/CAPP系统过程中,所涉及到的一些关键的开发技术,解决了针对SQLServer2000数据库的访问问题。 相似文献
12.
13.
An accurate value of the D/H ratio in the local interstellar medium (LISM) and a better understanding of the D/H variations
with position in the Galactic disk and halo are vitally important questions as they provide information on the primordial
D/H ratio in the Galaxy at the time of the protosolar nebula, and the amount of astration and mixing in the Galaxy over time.
Recent measurements have been obtained with UV spectrographs on FUSE, HST, and IMAPS using hot white dwarfs, OB stars, and
late-type stars as background light sources against which to measure absorption by D and H in the interstellar medium along
the lines of sight. Recent analyses of FUSE observations of seven white dwarfs and subdwarfs provide a weighted mean value
of D/H = (1.52±0.08) × 10−5 (15.2 ± 0.8 ppm), consistent with the value of (1.50 ± 0.10) × 10−5 (15.0 ± 1.0 ppm) obtained from analysis of lines of sight toward nearby late-type stars. Both numbers refer to the ISM within
about 100 pc of the Sun, which samples warm clouds located within the Local Bubble. Outside of the Local Bubble at distances
of 200 to 500 pc, analyses of far-UV spectra obtained with the IMAPS instrument indicate a much wider range of D/H ratios
between 0.8 to 2.2 ppm. This portion of the Galactic disk provides information on inhomogeneous astration in the Galaxy.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
14.
Palhares R.M. Peres P.L.D. 《IEEE transactions on aerospace and electronic systems》2001,37(1):292-296
The problem of full-order robust filtering design for discrete-time uncertain linear systems is addressed. The uncertain parameters are assumed to belong to convex bounded domains (polytope type uncertainty). The main purpose is to design a stable linear filter such that the filtering error output signal remains bounded. For that, the parameterization of all linear filters assuring quadratic stability with an H∞ attenuation constraint to the filtering error system is provided in terms of linear matrix inequalities (LMIs). Then, through the definition of an auxiliary cost, an upper bound to the filtering error variance is minimized, providing a mixed H2/H ∞ guaranteed cost filtering design. Standard optimization procedures with global convergence assured can be used to solve the problem, as illustrated by an example 相似文献
15.
在合金的基础上进一步引入纳米陶瓷颗粒,从而制备出颗粒增强金属基复合材料,是提高金属材料综合性能的重要手段。本文从原位自生TiB_2/Al基复合材料的制备方法、不同加工工艺下复合材料的微观组织、复合材料的力学性能三个方面总结了其研究现状,同时展望了原位自生TiB_2/Al基复合材料的发展方向。通过原位自生方法制备出的TiB_2颗粒增强铝基复合材料具有颗粒尺寸小、与基体界面结合良好等优点。通过合金化设计、热加工塑性变形、快速凝固工艺可进一步改善纳米陶瓷颗粒的分散性。相对于外加法制备的金属基复合材料,原位自生TiB_2/Al基复合材料具有更加优异的力学性能,如弹性模量、强度、抗疲劳性能、抗蠕变性能等。 相似文献
16.
徐德明 《航空标准化与质量》1999,(5)
总结了CAD/CAM/C AT技术在S92
飞机工艺装备上应用的优点在设计方面减少了中间设计环节,提高了工装的协调准确度,并缩短了设计周期;在制造方面提高了加工质量,缩短了加工周期;在检测方面提高了检测精度和检测效率。 相似文献
17.
CIMS环境下的模具CAD/CAPP/CAM技术 总被引:1,自引:0,他引:1
在CIMS环境下的模具CAD/CAPP/CAM技术将零件设计,模具设计,模具制造有机地集成起来,实现信息的集成与共享,缩短产品的开发和生产准备时间,提高产品的质量。 相似文献
18.
We present the regression models for determining the total excess air ratio αΣ and gas temperature T
g
* upstream of the high-pressure turbine formed on the basis of the engine parameter values that are regularly measured. The
sensitivity of the regression models presented to the sensor and instrumentation precision is studied. The errors of measuring
and calculating αΣ and T
g
* in different altitude-speed engine operation conditions are shown. 相似文献
19.
20.
继美国空军和海军先后开展其无人作战飞机项目后,美陆军现在也开始了真无人战斗旋翼机项目。与前两个军种的项目相比,美陆军的项目思想上显得更为激进,自然也面临着许多的技术难点 相似文献