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31.
基于量子行为鸽群优化的无人机紧密编队控制 总被引:1,自引:2,他引:1
随着军事、民用需求的提高和相关领域的技术推动,无人机编队协同作业已成为当今人们逐渐关注的焦点。无人机紧密编队是指无人机间侧向距离在1~2倍翼展内的编队,因其可有效改善编队中无人机的气动性能而备受瞩目。基于无人机紧密编队条件下的气动耦合效应,建立三维空间下的状态空间方程描述双机相对运动,并推导了紧密编队条件下的双机最优编队构型,在此构型下将人工势场法和编队控制相结合作为控制系统中的间接控制环,并针对基本鸽群优化算法的寻优缺陷利用量子行为规则对其进行改进,将改进后的鸽群优化算法和无人机控制量结合作为控制系统中的直接控制环,最后通过仿真对比验证了此控制系统对于紧密编队控制的有效性。 相似文献
32.
立方体星的技术发展和应用前景 总被引:2,自引:1,他引:1
系统论述了立方体星技术发展的三个阶段;从2010-2013年已成功发射的立方体星与纳卫星中挑选了10颗典型卫星,研究分析其技术水平、应用价值和特点优势;并重点论述了立方体纳卫星的应用;最后预测了立方体纳卫星的未来应用前景。 相似文献
33.
The past dozen years have produced a new paradigm with regard to the source regions of comets in the early solar system. It
is now widely recognized that the likely source of the Jupiter-family short-period comets (those with Tisserand parameters,
T > 2 and periods, P, generally < 20 years) is the Kuiper belt in the ecliptic plane beyond Neptune. In contrast, the source
of the Halley-type and long-period comets (those with T < 2 and P > 20 years) appears to be the Oort cloud. However, the comets
in the Oort cloud almost certainly originated elsewhere, since accretion is very inefficient at such large heliocentric distances.
New dynamical studies now suggest that the source of the Oort cloud comets is the entire giant planets region from Jupiter
to Neptune, rather than primarily the Uranus-Neptune region, as previously thought. Some fraction of the Oort cloud population
may even be asteroidal bodies formed inside the orbit of Jupiter. These comets and asteroids underwent a complex dynamical
random walk among the giant planets before they were ejected to distant orbits in the Oort cloud, with possible interesting
consequences for their thermal and collisional histories. Observational evidence for diversity in cometary compositions is
limited, at best.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
34.
Periodic relative orbits of two spacecraft subject to differential gravity and electrostatic forcing
Coulomb forces between charged close-flying satellites can be used for formation control, and constant electric potentials enable static equilibria solutions. In this work, open-loop time-varying potential functions, which produce periodic, two-craft, Coulomb formation motions are demonstrated for the first time. This is done in the rotating Hill-Frame, with linearized gravity, and craft position components assumed in the form of simple harmonic oscillators. Substitution of the oscillatory functions into the dynamics, further constrains these functions, and yields necessary potential histories, to produce the periodic flow. The assumed position functions, however, are not arbitrary, since the dynamical model restricts what oscillatory trajectories are allowed. Specifically, a Hill-Frame integral of motion is derived, and this is used to show certain candidate periodic functions to be inadmissible. The system dynamics are then linearized to expose stability properties of the solutions, and it is established that asymptotic stability is impossible for all orbit families. Finally, the degree of instability in the assumed motions, over free parameter ranges, is determined numerically via the Floquet multipliers of the associated full-cycle state-transition matrices. 相似文献
35.
This paper advances scenarios for an evolutionary approach to the establishment of a Human Mission from Planet Earth involving exploration and utilization of the Moon and Mars. Of critical importance are the concepts of robotic–human and Moon–Mars synergies. The paper discusses the rationale variables that have an influence on types of space activities pursued and thus the policy that leads to particular scenarios. In this regard, the technological, scientific, and sociopolitical/socioeconomic impacts and consequences related to a Human Mission from Planet Earth are examined. 相似文献
36.
Dong-Yoon Kim Byoungsam Woo Sang-Young Park Kyu-Hong Choi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009,44(11):1257-1269
A hybrid optimization method is developed for fuel-optimal reconfigurations of a group of satellites flying in formation. The genetic algorithm performs a global search to find two-impulse trajectories, and primer vector analysis finds multiple-impulsive local optimal trajectories with the two-impulse trajectories as initial guesses. Hybrid optimization finds globally optimal trajectories for formation reconfigurations, including formation resizing, reassignment and reorientation maneuvers. Multiple-impulse trajectories reduce the fuel consumption from the two-impulse trajectories by up to 4.4% for those maneuvers. In real missions, satellites can follow two-impulse trajectories to gain the advantage of a smaller number of impulses, with the cost of slightly more propellant. The qualitative characteristics of the optimal trajectories are analyzed from the number of optimal trajectories found by hybrid optimization. 相似文献
37.
Yann Alibert Christoph Mordasini Olivier Mousis Willy Benz 《Space Science Reviews》2005,116(1-2):77-95
We present models of giant planet formation, taking into account migration and disk viscous evolution. We show that migration
can significantly reduce the formation timescale bringing it in good agreement with typical observed disk lifetimes. We then
present a model that produces a planet whose current location, core mass and total mass are comparable with the one of Jupiter.
For this model, we calculate the enrichments in volatiles and compare them with the one measured by the Galileo probe. We
show that our models can reproduce both the measured atmosphere enrichments and the constraints derived by Guillot et al. (2004), if we assume the accretion of planetesimals with ices/rocks ratio equal to 4, and that a substantial amount of CO2 was present in vapor phase in the solar nebula, in agreement with ISM measurements. 相似文献
38.
39.
Bruno Sicardy 《Space Science Reviews》2005,116(1-2):457-470
Planetary rings are found around all four giant planets of our solar system. These collisional and highly flattened disks
exhibit a whole wealth of physical processes involving dust grains up to meter-sized boulders. These processes, together with
ring composition, can help understand better the formation and evolution of proto-satellite and proto-planetary disks in the
early solar system. The present chapter reviews some fundamental aspects of ring dynamics and composition. The forthcoming
exploration of the Saturn system by the Cassini mission will bring both high resolution and time-dependent information on Saturn’s rings. 相似文献
40.
H.-E. Frhlich V. Müller H. Oleak 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,3(10-12)
Dusty pregalactic Population III objects may provide a mechanism for an effective thermalization of the star radiation. They may generate the observed microwave background and so the high cosmic photon entropy. Assuming a tepid universe a smaller primordial entropy contribution results in reasonable mass scales and amplification factors of pregalactic density fluctuations. 相似文献