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951.
针对以飞轮为执行机构的空间飞行器进行姿态大角度机动递阶饱和控制。在初始状念任意,反作用轮输出力矩受限、速率饱和约束条件下,提出递阶饱和的变结构机动策略,即针对飞行器的运动学模型,利用飞行器的误差四元数和角速度,通过绕瞬时欧拉轴旋转,引入误差凹元数限幅器,对姿态偏差进行逐次消除,提出了不需事先规划轨迹的绕欧拉轴逐次逼近控制算法。并且引入模糊推理规则来改进递阶饱和变结构控制设计,使得系统轨迹既能快速趋近滑动面又能降低抖振,有效减弱了一般变结构控制律中抖振问题,从而提高了变结构控制律的品质。 相似文献
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954.
Time profile of the fluxes of energetic solar particles generated by solar flares (including their phase of decline) is formed to a large extent by the structure of the interplanetary magnetic field and its irregularities that move away from the Sun with the solar wind velocity. When propagation is a pure diffusion, the solar particle fluxes decay after the maximum in a power-law manner. At the same time in many cases this decay is exponential, which is indicative of a considerable role played by the convective sweep of particles and their adiabatic deceleration in the expanding solar wind. In this paper we consider the events with long exponential decays and newly discovered series of successive events with identical exponential decays lasting for one to two weeks or more. They allow us to assume that the interplanetary space is stable and homogeneous during this period. 相似文献
955.
956.
A mode of motion of a satellite with respect to its center of mass is studied, which is called the biaxial rotation in the orbit plane. In this mode of rotation, an elongated and nearly dynamically symmetric satellite rotates around the longitudinal axis, which, in turn, rotates around the normal to the plane of an orbit; the angular velocity of rotation around the longitudinal axis is several times larger than the orbital angular velocity, deviations of this axis from the orbit plane are small. Such a rotation is convenient in the case when it is required to secure a sufficiently uniform illumination of the satellite's surface by the Sun at a comparatively small angular velocity of the satellite. The investigation consists of the numerical integration of equations of the satellite's motion, which take into account gravitational and restoring aerodynamic moments, as well as the evolution of the orbit. At high orbits, the mode of the biaxial rotation is conserved for an appreciable length of time, and at low orbits it is destroyed due to the impact of the aerodynamic moment. The orbit altitudes and the method of constructing the initial conditions of motion that guarantee a sufficiently prolonged period of existence of this mode are specified. 相似文献
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本文提出了铅化合物催化双基推进剂燃烧的反应历程。充分说明这类化合物是最终通过提高燃烧表面处嘶嘶区温度梯度提高燃速的。本文还提出了“铅化合物有通过增加燃烧表面上碳质物量增加燃速的一面,还有通过减少碳质物抑制燃速增加的一面”这一新的论点及抑制碳质物增加的反应并阐明了压力对这种抑制能力的影响。最后根据本文提出的作用机理及传热原理圆满解释了超速、平平和/或麦撒效应。 相似文献
959.
In this paper we continue the analysis of the influence of solar and interplanetary events on magnetic storms of the Earth that was started in [9, 10]. Different experimental results on solar-terrestrial physics are analyzed in the study and the effects are determined that arise due to differences in the methods used to analyze the data. The classifications of magnetic storms by the K
p and D
st indices, the solar flare classifications by optical and X-ray observations, and the classifications of different geoeffective interplanetary events are compared and discussed. It is demonstrated that quantitative estimations of the relationships between two types of events often depend on the direction in which the events are compared. In particular, it was demonstrated that the geoeffectiveness of halo CMEs (that is, the percentage of Earth-directed coronal mass ejections that result in geomagnetic storms) is 40–50%. Higher values given in some papers were obtained by another method, in which they were defined as the probability of finding candidates for a source of geomagnetic storms among CMEs, and, strictly speaking, these values are not true estimates of the geoeffectiveness. The latter results are also in contrast with the results of the two-stage tracing of the events: first a storm—an interplanetary disturbance, and then an interplanetary disturbance—a CME. 相似文献
960.