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基于单级倒立摆这一非线性系统的T-S模糊模型,提出了一种采用模糊模型相除补偿技术和LMI技术相结合的模糊控制器设计方法,并在MATLAB/Simulink上进行了仿真试验。仿真结果表明,该方法与基于LMI的PDC方法相比,具有调节时间短,保守性更小的特点,规则越多,优势越明显,非常适用于复杂非线性系统的控制。 相似文献
294.
时间统一系统是航天测控体系的重要组成部分。网络时间协议NTP是Internet通用的时间统一方式。本文在分析了NTP工作原理、算法、精度的基础上,建立了在航天测控计算机系统上的NTP应用模型,分析了应用中的关键技术。该模型已成功应用于不同的测控计算机业务子网上。最后借鉴NTP校时策略对现行校时算法提出了改进建议。 相似文献
295.
星载FPGA内时序电路设计与时钟控制技术分析 总被引:1,自引:0,他引:1
在分析星载FPGA内时序电路特性以及FPGA可编程资源特性的基础上,指出了FPGA内同步时序电路出现时钟偏斜现象的机理。针对时钟偏斜,提出了星载FPGA内时序电路的设计准则。基于设计准则,提出了并行移位寄存器的一种异步化设计方法,阐述了在FPGA源代码中设置设计约束,或在逻辑综合与布局布线过程中联合设置设计约束,将主要同步时序电路时钟信号布置在全局时钟网络上的方法。工程实践表明:上述方法很好地解决了星载FPGA内同步时序电路时钟偏斜问题,可确保星载FPGA工作的稳定性与可靠性。 相似文献
296.
Mohamed Khalil Ben-Larbi Kattia Flores Pozo Mirue Choi Tom Haylok Benjamin Grzesik Andreas Haas Dominik Krupke Harald Konstanski Volker Schaus Sándor P. Fekete Christian Schurig Enrico Stoll 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(11):3620-3637
Recent developments have seen a trend towards larger constellations of spacecraft, with some proposals featuring constellations of more than 10.000 satellites. While similar concepts for large constellations already existed in the past, traditional satellite deployments hardly ever feature groups of more than 100 satellites. This trend towards considerably larger satellite numbers originates from non-traditional design and operations of spacecraft by non-traditional space companies. The evolution in the space sector, precipitated by new players, is often referred to as “Space 4.0” or “New Space”. It necessitates a rethinking of the way satellites and satellite constellations are planned, designed, and operated. New operational paradigms are needed to enable automatic, optimal task definition, and scheduling in a holistic approach.This is the second of two companion papers that investigate the operations of distributed satellite systems. This second article investigates the classification of distributed satellite systems and evaluates commercial tools for automated spacecraft operations, whereas the first article performed a survey of conventional and “new space”operations of spacecraft constellations.Classification metrics for constellations are derived and evaluated with respect to their informative value concerning the operation, the automation, and the scalability of the constellation. The proposed classification system is applied to the Dove and RapidEye constellation and allows for a comparison between the presented automation approaches. Commercial tools for automated spacecraft operations are evaluated for several mission task elements, such as orbit control, orbit maintenance, and collision avoidance. Subsequently, the trends, benefits, and standardization needs for operational automation are identified. 相似文献
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Bao-Jun Pang Dong-Fang Wang Wei-Ke Xiao Bin-Bin Lu 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(8):2274-2281
The availability of engineering models to estimate the risk from space debris is essential for space missions. According to current research, cumulative flux calculation is mostly carried out based on the equal-width interval discretization. The method discretizes the volume around the Earth into cells defined in earth centered inertial coordinates. The resulting debris flux onto a target object is shown to depend on the chosen size of the cells. To avoid a discretization error, this must be accounted for. In order to present reliable flux predictions for space mission, the algorithm improvement is an ongoing topic for the related research field. The aim of this study was to examine the discretization error during the cumulative flux determination process. Both the effect of interval step length and the orbital boundary are under investigation. Several typical orbits are selected as examples here and the 2018/01/03 TLE (Two Line Element) data published by the US Space Surveillance Network is used as the debris background in this paper. Furthermore, the Interval Distance-Based method for Discretization (IDD) is adopted in this paper. A position-centered flux determination method is introduced based on the IDD method. According to the example analysis, the IDD used in the flux calculation process provides results which are less affected by the interval step-size setup; and the orbital boundary has no effect on the calculation process. In other words, the discretization error is significantly reduced. The position-centered method provided a possible suggestion for the improvement of space debris environment models. 相似文献
299.
以词块教学理论为依据,分析在听说教学中进行词块训练的可行性。研究词块训练在听说课堂中的具体实施过程,并通过问卷调查和访谈结果,论证了听说课上引入词块理念能提高英语学习者听说能力从而提出词块学习对语言习得的有效性。 相似文献
300.
徐正国 《长沙航空职业技术学院学报》2005,5(4):77-79
从师爱是教育之本、师德之魂、教师之责、施教之法等四个方面阐述师爱是教师发自内心的对学生关心、爱护、尊重、信任、期待的美好情感活动的体现,揭示作为一名合格的人民教师必须具备师爱素质的道理。 相似文献