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441.
徐焕然 《中国民航学院学报》1992,10(1):58-64
本文根据航空发动机和动力传动系统减速器的特点,提出了常用的NGW型行星减速器设计是“机械设计”课程设计的最佳题目。扼要分析了其计算特点和结构特点,并给出了设计题目及部分原始数据以供参考。 相似文献
442.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2023,71(1):645-653
This paper investigates the asteroid hovering problem using the Multiple-Overlapping-Horizon Multiple-Model Predictive Control method. The effectiveness of the predictive controllers in satisfying control constraints and minimizing the required control effort is making Model Predictive Control a desirable control method for asteroid exploration missions which consist of the asteroid hovering phase. However, the computational burden of Model Predictive Control is an obstacle to employing the asteroid’s complex gravitational field model. As an alternative option, the Multiple Horizon Multiple-Model Predictive Control method has been introduced previously, which could provide a solution with the less computational burden with respect to the nonlinear Model Predictive Control. It was shown that it is not necessary to deduce the exact dynamics model to predict the system’s behavior during a long period using this approach. However, the calculated control acceleration was not smooth enough because of the crisp borders of consecutive horizons, which may cause an image motion and degrades the geometric accuracy of high-resolution images in asteroid hovering missions. In this paper, the Multiple-Overlapping-Horizon Multiple-Model Predictive Control method is introduced instead to solve the problem of controlling acceleration fluctuations by overlapping consecutive horizons. Numerical simulation results are presented to validate the effectiveness of the proposed control method, and its advantage is demonstrated accordingly for the asteroid hovering problem in achieving the hovering position and velocity. 相似文献
443.
444.
双三体系统不变流形拼接成的低成本探月轨道 总被引:3,自引:0,他引:3
传统的探月轨道设计原理为二体模型框架下的Hohmann变轨理论,但1991年日本的Hiten探月器利用太阳的摄动,用比传统的方法更少的燃料完成了探月任务。利用三体问题非线性系统的不变流形设计了节省燃料的探月轨道。沿用JPL研究组的思路,将太阳-地球-月亮-航天器四体问题分解成太阳-地球-航天器和地球-月亮-航天器两个共面的圆形限制性三体问题,对Hiten类的探月轨道给出了更深刻的数学、力学解释;给出了流形的结构以及更合理的拼接方式;找到了发射位置、发射速度和拼接点;设计出了类似Hiten探月器的探月轨道,可比传统方法节省速度增量12%左右。结果证明了三体系统不变流形在登月轨道设计研究中的可行性和优越性。 相似文献
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446.
考虑了行星架微位移、时变啮合刚度、旋转阻尼和构件自重,建立了行星传动系统动力学微分方程.利用多领域工程系统建模、分析与优化语言Modelica进行求解,分析了各主要构件支撑刚度对行星传动系统均载特性的影响.研究结果表明:刚性支撑条件下,较小的系统误差都将引起行星轮间载荷分配严重不均匀.一个或者多个构件的支撑刚度小于107N/m时系统能获得较好的均载效果.在构件支撑刚度敏感区间,随着该构件支撑刚度的增大,系统均载性能将迅速恶化.多个构件支撑刚度减小时,系统的均载效果比单个构件支撑刚度减小要好.改变其中某个行星轮的支撑刚度会使载荷在行星轮间重新分配,降低某个行星轮的支撑刚度,其分配的载荷减小. 相似文献
447.
G. Salamuni
car 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,33(12):2281-2287
The Mathematical Statistics Theory (MST) and the Mathematical Theory of Stochastic Processes (MTSP) are different branches of the more general Mathematical Probability Theory (MPT) that represents different aspects of some physical processes we can analyze using mathematics. Each model of a stochastic process according to the MTSP can provide one or more interpretations in the MST domain. The importance of MTSP is that each such interpretation can provide large amount of new information. While large body of work on the impact crater statistics according to MST has already been done, it is yet to be investigated as to how we can model a stochastic process according to MTSP; for example, bombardment of the planetary surface or something else in a Lunar and Planetary Science (LPS) domain. In order to show possible achievements, the possible existence of a Martian ocean was chosen as a query that could be addressed through computations using presumptions according to MTSP, including probability of existence as well as lateral and vertical extent and duration of time. While the presumptions for this particular case will also be addressed in certain degree, this will be done primarily to show complexities of some physical process that can be modeled, rather than to prove correctness of the concrete values computed here. While this in itself can be the objective in some future work toward the formal proof of the probability, extent, and timing of oceans on Mars, the basic idea here is to show the basic principles of MTSP, and its potential for addressing LPS-related phenomena. Here, I attempt to show how this approach can: (1) provide large amounts of previously unknown information about physical processes on the surface of the planet, (2) lead to a better understanding of the processes that have shaped the surface of the planet, and/or (3) help constrain the amount of resurfacing. Coupled with other current methodologies, MTSP can result in a better understanding of the history of Mars, as well as other lunar and planetary bodies. 相似文献
448.
449.
月球巡视探测器系统研究 总被引:1,自引:0,他引:1
简要回顾月球探测的发展现状,给出月球巡视探测器的概念和主要功能.据此分析和研究系统方案设计、分系统组成、工作状态和工作模式。最后提出月球巡视探测器的关键技术,以期为月球巡视探测器的工程研制提供参考。 相似文献
450.
This paper gives a brief introduction of YingHuo-1 (YH-1), a Chinese Martian Space Environment Exploration Orbiter. YH-1 is a micro-satellite developed by Chinese Aerospace Industry,and will be launched together with Russian spacecraft, Phobos-Grunt, to orbit Mars in September,2009. Four payloads are selected for the mission, plasma package, including of electron analyzer, ion energy and mass analyzer; sat-sat occultation receiver; flux-gate magnetometer; and optical monitor.YH-1 mission focus on the investigation of the characteristics and its evolution of the Martian space Environment, and identifying major plasma processes, which provide channels for Martian volatiles escaping. 相似文献