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191.
The tracking of orientation and angular velocity is a primary attitude control task for an on-orbit space- craft. The problem for a rigid spacecraft tracking a desired angular velocity profile is addressed using an adaptive feedback control. An angular velocity feedback tracking algorithm is firstly developed based on the precisely known attitude dynamics of the spacecraft, and the global tracking of the control algorithm is proved based on the Lya- punov analysis. An adaptation mechanism is then designed to deal with the dynamic uncertainties of the spacecraft. Such an adaptation mechanism enables the controller to track any desired angular velocity trajectories even in the presence of uncertain inertia parameters, although it does not guarantee the inertia tensor being precisely identified. To verify the effectiveness of the proposed adaptive control policy, computer simulations on dynamic equations of a spacecraft are conducted and their results are discussed. 相似文献
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193.
Yuliang Qiao Shangmin Zhao Liu Zhen Jia Bei 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
The launch and successful operation of Chinese–Brazil Earth resources satellite (CBERS-1) in China has accelerated the application of space technology in China. These applications include agriculture, forestry, water conservation, land resources, city planning, environment protection and natural hazards monitoring and so on. The result of these applications provides a scientific basis for government decision making and has created great economic and social benefits in Chinese national economy construction. In this paper we present examples and provide auxiliary documentation of additional applications of the data from Earth resource monitoring. 相似文献
194.
The infrared radiation signature of the plume from solid propellants with different energy characteristics is not the same. Three kinds of double-base propellants of different energy characteristics are chosen to measure the infrared spectral radiance from 1000 cm 1 to 4500 cm 1 of their plumes. The radiative spectrum is obtained in the tests. The experimental results indicate that the infrared radiation of the plume is determined by the energy characteristics of the propellant. The radiative transfer calculation models of the exhaust plume for the solid propellants are established. By including the chemical reaction source term and the radiation source term into the energy equation, the plume field and the radiative transfer are solved in a coupled way. The calculated results are consistent with the experimental data, so the reliability of the models is confirmed. The temperature distribution and the extent of the afterburning of the plume are distinct for the propellants of different energy characteristics, therefore the plume radiation varies for different propellants. The temperature of the fluid cell in the plume will increase or decrease to some extent by the influence of the radiation term. 相似文献
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196.
Vortex-acoustic coupling is one of the most important potential sources of combustion instability in solid rocket motors (SRMs). Based on the Von Karman Institute for Fluid Dynamics (VKI) experimental motor, the influence of the thermal inhibitor position and temperature on vortex-shedding-driven pressure oscillations is numerically studied via the large eddy simulation (LES) method. The simulation results demonstrate that vortex shedding is a periodic process and its accurate frequency can be numerically obtained. Acoustic modes could be easily excited by vortex shedding. The vortex shedding frequency and second acoustic frequency dominate the pressure oscillation characteristics in the chamber. Thermal inhibitor position and gas temperature have little effect on vortex shedding frequency, but have great impact on pressure oscillation amplitude. Pressure amplitude is much higher when the thermal inhibitor locates at the acoustic velocity anti-nodes. The farther the thermal inhibitor is to the nozzle head, the more vortex energy would be dissipated by the turbulence. Therefore, the vortex shedding amplitude at the second acoustic velocity antinode near 3/4L (L is chamber length) is larger than those of others. Besides, the natural acoustic frequencies increase with the gas temperature. As the vortex shedding frequency departs from the natural acoustic frequency, the vortex-acoustic feedback loop is decoupled. Consequently, both the vortex shedding and acoustic amplitudes decrease rapidly. 相似文献
197.
用应力降落法测定单向PAN基碳纤维T300增加热碳基复合材料在1900-2350℃蠕变内应力σ0,结果及分析表明,对单向C/C复合材料,σ0不是一个材料常数,而是温度T、初始力σs及结构因子S的函数,即σ0=σ0(t,σs,S)。 相似文献
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199.
对传统的质量控制算法和常规计算机质量控制算法进行了比较,把它们统一起来,并提出了一个变形了的EWMA质量控制算法,推导验证了其无偏估计量,分别针对抛弃和非抛弃两种形式求出了各自递推表达式。最后设计了一个基于EWMA计算机辅助质量控制系统,并据此进行了实验仿真。 相似文献
200.
提出一种在计算机集成环境下编制工艺现程的方法,以“约束”的概念体现工艺学原则和实际生产环境信息。零件的被加工表面信息直接从集成数据库中获取。通过工艺数据库得到各被加工表面的各种可能的加工活动信息。对以这些加工活动为元素的集合施加位置关系约束,采用一定算法得到零件的多个可行工艺规程。该CAPP方法可在产品设计由粗到细的各个阶段实现,适于并行工程环境。 相似文献