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211.
利用碳纤维三向编织物(triaxial woven fabric,TWF)作为增强材料,与柔性基体材料硅橡胶复合,制成兼具一定柔性和刚性的复合材料壳膜结构,用于卫星天线反射器,是一种新型的高精度可展开天线实现方案。采用复合材料细观方法,对碳纤维增强硅橡胶TWF复合材料进行了力学性能的研究。首先由纤维和基体的材料特性得到均质纤维束的材料特性;接下来考虑纤维束交织情况(起伏波动)建立由纤维束组成的单胞实体有限元模型;然后对单胞实体有限元模型进行均匀化分析,施加周期性边界条件,最终得到等效的均质材料特性;为满足天线反射器高性能需求,分析了碳纤维种类、纤维体积分数对单胞等效性能的影响规律。对该材料力学性能的研究,可以为其未来应用于大型高精度可展开天线反射器提供一定的理论依据。 相似文献
212.
Roberto Furfaro Riccardo Barocco Richard Linares Francesco Topputo Vishnu Reddy Jules Simo Lucille Le Corre 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(1):617-638
Close proximity operations around small bodies are extremely challenging due to their uncertain dynamical environment. Autonomous guidance and navigation around small bodies require fast and accurate modeling of the gravitational field for potential on-board computation. In this paper, we investigate a model-based, data-driven approach to compute and predict the gravitational acceleration around irregular small bodies. More specifically, we employ Extreme Learning Machine (ELM) theories to design, train and validate Single-Layer Feedforward Networks (SLFN) capable of learning the relationship between the spacecraft position and the gravitational acceleration. ELM-base neural networks are trained without iterative tuning therefore dramatically reducing the training time. Analysis of performance in constant density models for asteroid 25143 Itokawa and comet 67/P Churyumov-Gerasimenko show that ELM-based SLFN are able learn the desired functional relationship both globally and in selected localized areas near the surface. The latter results in a robust neural algorithm for on-board, real-time calculation of the gravity field needed for guidance and control in close-proximity operations near the asteroid surface. 相似文献
213.
针对航空燃气轮机流量系数插值建模过程中,获取样本数据时的实验成本较高以及插值模型精度偏低这 2个问题,根据样本点在设计空间中的分布与模型精度的关系,在 Kriging插值模型的基础上,采用把垂距作为设计变量取值标准的取样算法。首先,将样本点与相邻 2点之间连线的垂距与垂距阈值进行比较,筛选出符合条件的数据点,形成候选点集;其次,选用高斯函数判定基础点集和候选点集的相关性;最后,使用该算法筛选后的样本点构建 Kriging插值模型。实验结果表明,该方法使用的样本点为原来数量的 70%左右,并且预测精度得到了提高,该方法是有效可行的。 相似文献
214.
Navigation and positioning is an important and challenging problem in many control engineering applications. It provides feedback information to design controllers for systems. In this paper, a bibliographical review on factor graph based navigation and positioning is presented. More specifically, the sensor modeling, the factor graph optimization methods, and the topology factor based cooperative localization are reviewed. The navigation and positioning methods via factor graph are considered a... 相似文献
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张斧 《中国空间科学技术》1989,9(1):1-5
本文阐述了一种可行的面阵CCD 成象光谱仪的设计。它具有光谱范围宽(0.4μm~1.1μm)、高光谱分辨率(9.2nm)、密集的光谱波段数(76)、较大的地物扫描视场角(30°)等一系列引人注目的优点。 相似文献
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Modeling and control for cooperative transport of a slung fluid container using quadrotors 总被引:3,自引:3,他引:0
In this paper, dynamic modeling and control problem for transfer of a sloshing liquid container suspended through rigid massless links from a team of quadrotors are investigated. By the proposed solution, pose of the slung container and fluid sloshing modes are stabilized appropriately. Dynamics of the container-liquid-quadrotors system is modeled by Euler-Lagrange method. Fluid slosh dynamics is included using multi-mass-spring model. According to derived model, a proper control law is designed for a system with three or more quadrotors. Implementing the proposed control law, quadrotors can control pose of the container, directions of the links and liquid sloshing modes simultaneously. Stability of closed loop system of tracking errors and sloshing modes are demonstrated using a theory of singularly perturbed systems and Lyapunov stability theorem. Also, the capability of the proposed feedback control laws in solving a formerly organized transport problem of a liquid filled container has been demonstrated in simulations. Moreover, priority of the proposed control scheme to an existing slung load controller in the literature is demonstrated. 相似文献