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基于神经网络的航天器GPS/INS组合定姿系统 总被引:1,自引:0,他引:1
基于GPS和惯性技术的组合导航系统是近年来导航系统的研究热点和主要发展方向.目前基于卡尔曼滤波方法的算法在稳定性、计算量、算法鲁棒性以及系统可观测性等方面仍然存在问题.基于神经网络技术研究了一种新的GPS/INS组合定姿自适应卡尔曼滤波方法,理论分析表明,该方法不但对姿态信息具有较好的估计性能,而且对系统模型的精确性、噪声特性具备良好的鲁棒性.最后,利用模拟数据对所研究算法进行了分析计算,与传统的卡尔曼滤波方法进行了比较、分析,结果表明所设计组合算法在精度、稳定性以及鲁棒性等方面较传统卡尔曼方法具有良好的特性. 相似文献
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XU Yong-chaoa * YUAN Shi-jiana CHEN Yua ZHOU Li-xinb KANG Da-changa aSchool of Materials Science Engineering Harbin Institute of Technology Harbin China bInstitute of Metal Research Chinese Academy of Sciences Shenyang China 《中国航空学报》2006,19(Z1)
The dome hydro-forming was studied theoretically and experimentally. The theoretical analysis shows that the process of dome hydro-forming can be divided into two stages, i.e., firstly forming a hemi-sphere and secondly forming a hemi-toroidal. Theoretically, being larger than those in the outer area of a hemi-toroidal shell, the radial tensile stresses take place in the inner area where fracture is more likely to occur in the forming process. The required hydraulic pressure to form the dome should be determined by the deformation in the outer area, hitting about 12 MPa in theory. The experimental results show that the dome could be produced in one operation by hydro-forming which needs a hydraulic pressure of about 9 MPa. The experimental results prove to agree well with the theoretical analysis. In order to avoid wrinkling and fracture, the closing force acted on the die should be adjusted properly in accordance with the hydraulic pressure. 相似文献
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Guo Jian-shan Shang She-ping Shi Jiankui Zhang Manlian Luo Xigui Zheng Hong 《Space Science Reviews》2003,107(1-2):229-250
Observation, specification and prediction of ionospheric weather are the key scientific pursuits of space physicists, which
largely based on an optimal assimilation system. The optimal assimilation system, or commonly called data assimilation system,
consists of dynamic process, observation system and optimal estimation procedure. We attempt to give a complete framework
in this paper under which the data assimilation procedure carries through. We discuss some crucial issues of data assimilation
as follows: modeling a dynamic system for ionospheric weather; state estimation for static or steady system in sense of optimization
and likelihood; state and its uncertainty estimation for dynamic process. Meanwhile we also discuss briefly the observability
of an observation system; system parameter identification. Some data assimilation procedures existed at present are reviewed
in the framework of this paper. As an example, a second order dynamic system is discussed in more detail to illustrate the
specific optimal assimilation procedure, ranging from modeling the system, state and its uncertainty calculation, to the quantitatively
integration of dynamic law, measurement to significantly reduce the estimation error. The analysis shows that the optimal
assimilation model, with mathematical core of optimal estimation, differs from the theoretical, empirical and semi-empirical
models in assimilating measured data, being constrained by physical law and being optimized respectively. The data assimilation
technique, due to its optimization and integration feature, could obtain better accurate results than those obtained by dynamic
process, measurement or their statistical analysis alone. The model based on optimal assimilation meets well with the criterion
of the model or algorithm assessment by ‘space weather metrics’. More attention for optimal assimilation procedure creation
should be paid to transition matrix finding, which is usually not easy for practical space weather system. High performance
computing hardware and software studies should be promoted further so as to meet the requirement of large storage and extensive
computation in the optimal estimation. The discussion in this paper is appropriate for the static or steady state or transition
process of dynamic system. Many phenomena in space environment are unstable and chaos. So space environment study should include
and integrate these two branches of learning.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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李崇俊%郑金煌%苏红%邓红兵 《宇航材料工艺》2004,34(1):33-37
研究了二维C/C(2D -C/C)复合材料在高温下层剪强度、弯曲强度和模量、热导率和线膨胀系数的变化规律。结果表明 ,所制得的 2D -C/C复合材料的层剪强度随温度的升高变化不大、弯曲强度随测试温度的升高而增加 ;2 0 0 0℃的层剪强度、弯曲强度分别达到 1 4 .8MPa和 2 2 7.4MPa ,较室温分别提高了9.6 %和 6 0 %。弯曲模量在 1 0 0 0℃时增加到 39.4GPa ,在 2 0 0 0℃则下降 ,低于室温数值。 2D -C/C复合材料的热导率、线膨胀系数在z向和x -y向都具有明显的各向异性。未石墨化 2D -C/C复合材料 2 0 0℃的z向热导率是 4 .4 1W / (m·K) ,且随温度的升高而增加 ;而石墨化 2D -C/C复合材料 2 0 0℃的z向、x -y向热导率分别是 1 8.0 2W / (m·K)和 73.2 9W / (m·K) ,随温度的升高而下降。 2D -C/C复合材料在z向的线膨胀系数较大 ,80 0℃以内在 8× 1 0 - 6 /K~ 1 0× 1 0 - 6 /K之间 ;而在x -y向线膨胀系数在 80 0℃以内都很小 ,基本上接近于零 相似文献
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