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B. Suneel Kumar S. Sreenivasan J.V. Subba Rao R.K. Manchanda 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
The zero pressure plastic balloons used for high altitude studies are generally made from polyethylene material. Tensile properties of the thin film polymer are the key parameters for material selection due to extremely low temperature of −90 °C encountered by the balloons in the tropopause region during the ascent at equatorial latitudes. The physical and structural properties of the material determine the uniformity of the stress distribution over the entire shell. Load stresses from the suspended load propagate via load tapes heat sealed along with the gore seals as per the balloon design. A balance between this heat seal strength and the film strength is a desirable property of the basic resin in terms of the bubble strength, gauge uniformity, and long-term storage properties. In addition, the design of the top shell of the balloon and its stress distribution play an important role since only a fraction of the balloon is deployed during the filling operation and the ascent. In this paper we describe the mechanical properties of the ‘ANTRIX’ film developed by us and the optimized design of single cap balloons, which have been successfully used in our experiments over the past 5 years. 相似文献
473.
介绍了一种用于被动型氢钟单频调制的数字伺服电路,实现了系统的锁定,测试了中短期稳定度。最后分析了D/A的位数对其稳定度的影响。 相似文献
474.
Changsheng Cai Yang Gao Lin Pan Wujiao Dai 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
With the rapid development of the COMPASS system, it is currently capable of providing regional navigation services. In order to test its data quality and performance for single point positioning (SPP), experiments have been conducted under different observing conditions including open sky, under trees, nearby a glass wall, nearby a large area of water, under high-voltage lines and under a signal transmitting tower. To assess the COMPASS data quality, the code multipath, cycle slip occurrence rate and data availability were analyzed and compared to GPS data. The datasets obtained from the experiments have also been utilized to perform combined GPS/COMPASS SPP on an epoch-by-epoch basis using unsmoothed single-frequency code observations. The investigation on the regional navigation performance aims at low-accuracy applications and all tests are made in Changsha, China, using the “SOUTH S82-C” GPS/COMPASS receivers. The results show that adding COMPASS observations can significantly improve the positioning accuracy of single-frequency GPS-only SPP in environments with limited satellite visibility. Since the COMPASS system is still in an initial operational stage, all results are obtained based on a fairly limited amount of data. 相似文献
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针对非合作目标存在对抗性力矩输出情况下的组合体航天器姿态控制系统,提出了一种基于模糊神经网络干扰观测器(Fuzzy Neural Network Disturbance Observer, FNNDO)的非奇异终端滑模(Nonsingular Terminal Sliding Mode, NTSM)有限时间控制策略。首先以服务航天器为基准,建立组合体航天器姿态数学模型,然后针对包含惯量不确定性、目标对抗性力矩等的等效干扰力矩,设计了一种具有自适应能力的FNNDO,可以实现对等效干扰的有效跟踪。在FNNDO的基础上,设计NTSM控制器,利用Lyapunov理论证明闭环系统的有限时间稳定性。最后,仿真实验结果表明了控制策略的有效性和观测器在观测性能上的优越性。 相似文献
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在单片机测控系统中,抗干扰性能是系统可靠性的重要指标,抗干扰设计是单片机测控系统研制中必须要考虑的重要内容。通过比较探讨抗电源干扰、抗信号通道干扰、印刷电路板抗干扰以及软件抗干扰等四种单片机测控系统中的四种干扰类型,结合工业现场给出了几种行之有效的抗干扰措施。 相似文献
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针对执行器失效的一类飞行控制系统,提出基于迭代学习观测器的模糊容错控制律,利用Takagi-Sugeno(T-S)模糊模型对非线性系统进行描述、建模和控制.一旦系统发生故障,迭代学习观测器在估计系统状态的同时估计执行器的卡死值,然后利用估计的状态和故障信息构成反馈模糊控制律进行调节,以实现故障系统对参考系统的状态跟踪.给出了系统能进行容错控制的参数匹配条件,并利用Lyapunov理论详细分析了系统的稳定性以及闭环系统信号的有界性,某歼击机的仿真实例证明了本文方法的有效性. 相似文献
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