Modeling and identification of an electro-mechanical system: The LISA grabbing positioning and release mechanism case

In the frame of space missions, mechanisms often constitute critical systems whose functionality and performance need to be tested on ground before the mission launch. The LISA scientific space mission will detect gravitational waves by measuring the relative displacement of pairs of free-floating test masses set into geodesic motion onboard of three spacecrafts. Inside each satellite, the injection of the test masses from the caged configuration into the geodesic trajectory will be performed by the grabbing positioning and release mechanism. To provide a successful injection, the test masses must be dynamically released with a minimal residual velocity against adhesion with the holding device. A parameter that determines the test mass residual velocity is the quickness of the retraction of the holding device. The need arises then to characterize the dynamic response of the release mechanism in order to predict its behaviour in the in-flight conditions. Once a validated model of the mechanism is available, the compliance of the system to the tight requirement on the maximum allowed residual velocity of the test mass may be verified. Starting from an electro-mechanical model of the mechanism dynamics, this paper presents the results of the experimental identification of its relevant parameters.     

Development of life support requirements for long-term space flight.

When humans move out into the solar system to stay for long durations, the most immediate challenge will be the provision of a life-supporting environment in locations that are naturally devoid of food, air, and water. Life support systems must provide these commodities in all phases of space flight--during intravehicular activity (IVA) and during extra-vehicle activity (EVA). Systems that support human life must provide: overall reliability in the space environment, allowing maintenance and component replacement in space; reduced resupply mass of consumables and spares; for planetary surfaces, the ability to utilize local resources for increased self sufficiency; and the minimized mass power and volume requirements necessary for all space flight systems. This paper will discuss the melding of these technical requirements in such a way as to meet the human needs of space flight.     

遗传算法在质量矩导弹姿态控制中的应用

研究了三轴稳定控制系统的姿态控制问题.建立了内部带有3个可移动滑块的数学模型.利用RBF(Radial Basis Function)网络的快速自学习以及自适应特性,将其作为控制器不断调整滑块的位置.同时利用遗传算法(GA)的全局、并行寻优及增强式学习能力对神经网络控制器的权系进行优化.通过对滑块位置的协调控制,改变导弹的飞行姿态.最后讨论了滑块运动特性对系统性能产生的影响并对系统稳定性进行了分析.仿真结果表明该控制律能在保证系统稳定的情况下有效地实现导弹的姿态调整,并且提高了系统的动态响应品质.      

The private sector: A global pool of technical talent for remote sensing training and program support

The growing global pool of highly trained, technical talent in the private sector throughout the world reflects the degree of maturation that remote sensing from air and space vehicles has undergone, especially during the past ten years. This has been further spawned by the US Government move to commercialize the Landsat system. The number of qualified technicians and scientists has grown in proportion to the amount of data that has become available for public and private use. Applications of the data have matured from research investigations to operational use in many disciplines and geographic areas. Private and public industry corporations have established their own image processing and analytical laboratories to ensure their competitive positions. This has been further enhanced by the simultaneous availability of lower cost, analytical computer systems. Training and operational project development remain prominent objectives.While these are all very positive aspects a note of caution must be raised. Concern has recently been expressed by representatives of developing nations that not enough attention is given by remote sensing specialists to spelling out the limitations of the sensing systems or qualifying the degree of accuracy of the results obtained. Such criticisms are probably justified and it is recommended that remote sensing workers be mindful of such concerns.     

Taurid complex meteoroids detected near aphelion with Ulysses

Between 3.4 and 4.0 AU the dust detection system aboard the Ulysses spacecraft showed an increase in detection rate for particles with masses greater than 5 × 10⁻¹³ g. The spacecraft meteoroid encounter geometry indicates highly eccentric orbits detected near aphelion. The outer limit of the enhanced flux is imposed as meteoroids on such orbits move outside the aperture of the dust detector. The inner edge of the enhanced flux would be consistent with the aphelion distance acquired by 50-200 μm particles evolving for 10-20 kyr under Poynting-Robertson drag from an Encke type orbit. We propose such meteoroids provide a source population from which collisional fragmentation produces particles in the mass range to which the Ulysses detector is sensitive. Daughter fragments produced away from the aphelia of the parent orbits, a 2.2 AU, e 0.85, enter hyperbolic orbits which are not evident in the Ulysses data. The spatial density of fragments from collisions very near aphelion drops off rapidly as they evolve inward under Poynting-Robertson drag while collisions closer to 3.4 AU leave the subsequent peak density outside that radius for a significant fraction of the fragment's subsequent lifetime. The rapid orbital evolution for these collision fragments implies a recent breakup and probably a large reservoir of parent meteoroids.     

应用微机校定三相变压器的联结组及标号

三相变压的联结组标号对其正常运行极为重要，必须校定，而目前变还缺少全面快捷的校定方法和设备。本文介绍采用微机系统来实现联结组桔的校定，首先把四类联结组差别区分开，然后分析指出同一类联结组中，除有六种正序标号外，存在六种逆序标号，提出用新的筛选法能简捷地判别校定同一类的十二种标号，当微机系统进行实际测试时，必须考虑电源电压三相不对称程序的影响，故经数学推导得出用实测计算值代替理想计算值作判别比较的基     

Chemical and biological evolution in space

Astronomical infrared spectra are used to confirm the existence of complex organic molecules produced by ultraviolet photoprocessing of interstellar grain mantles. This material is shown to be the major component of the interstellar grains between the sun and the galactic center and, by inference, constitutes more than 10 million solar masses — or close to one part in a thousand of the entire mass of the milky way galaxy. It may be demonstrated that the primitive chemistry of the earth's surface was dominated by these extraterrestrial molecules after aggregated into comets if the rate of comet impacts with the earth was comparable with that required to account for the extinction of species over the past 300 million years.

Ultraviolet irradiation of bacterial spores has been studied for the first time under simulated interstellar conditions. The inactivation time predicted for the less dense regions of space is at most several hundred years. Within molecukar clouds it is shown on theoretical and experimental grounds that this t the estimated cloud. However survival of spores during their initial exposure to the solar ultraviolet presents a problem for panspermia because it requires that in the process of ejection from the earth's surface they must be enclosed within a cocoon (or mantle) of ultraviolet absorbing material of 0.6 μm thickness. Thus, although panspermia can not be rejected on the basis of lack of interstellar survival there may remain insurmountable obstacles to its occuring because of the very special protective shield requirements during ejection from its planetary source.     

Utilization of CAM,CAF, MAX,and FAX for space radiation analyses using HZETRN

To estimate astronaut health risk due to space radiation, one must have the ability to calculate various exposure-related quantities that are averaged over specific organs and tissue types. Such calculations require computational models of the ambient space radiation environment, particle transport, nuclear and atomic physics, and the human body. While significant efforts have been made to verify, validate, and quantify the uncertainties associated with many of these models and tools, relatively little work has focused on the uncertainties associated with the representation and utilization of the human phantoms. In this study, we first examine the anatomical properties of the Computerized Anatomical Man (CAM), Computerized Anatomical Female (CAF), Male Adult voXel (MAX), and Female Adult voXel (FAX) models by comparing the masses of various model tissues used to calculate effective dose to the reference values specified by the International Commission on Radiological Protection (ICRP). The MAX and FAX tissue masses are found to be in good agreement with the reference data, while major discrepancies are found between the CAM and CAF tissue masses and the reference data for almost all of the effective dose tissues. We next examine the distribution of target points used with the deterministic transport code HZETRN (High charge (Z) and Energy TRaNsport) to compute mass averaged exposure quantities. A numerical algorithm is presented and used to generate multiple point distributions of varying fidelity for many of the effective dose tissues identified in CAM, CAF, MAX, and FAX. The point distributions are used to compute mass averaged dose equivalent values under both a galactic cosmic ray (GCR) and solar particle event (SPE) environment impinging isotropically on three spherical aluminum shells with areal densities of 0.4 g/cm², 2.0 g/cm², and 10.0 g/cm². The dose equivalent values are examined to identify a recommended set of target points for each of the tissues and to further assess the differences between CAM, CAF, MAX, and FAX. It is concluded that the previously published CAM and CAF point distributions were significantly under-sampled and that the set of point distributions presented here should be adequate for future studies involving CAM, CAF, MAX, or FAX. It is also found that the errors associated with the mass and location of certain tissues in CAM and CAF have a significant impact on the mass averaged dose equivalent values, and it is concluded that MAX and FAX are more accurate than CAM and CAF for space radiation analyses.     

Type I supernovae origin: “Dualistic” hypothesis

Stars that explode as Type I Supernovae (SNI) are white dwarfs with masses practically equal to the Chandrasekhar limit M_ch. These white dwarfs forme either as a result of gas overflow onto a degenerate component in a binary system or due to the evolution of nuclei of the stars whose mass, on the main sequence, was 3 to 7 M_o. The masses of their nuclei are quite close to M_ch. It is convenient to consider three types of stellar evolution 1) “hyperbolic”: masses of nuclei formed as a result of evolution are > M_ch; such evolution ends in a Type II Supernova (SNII) outburst; 2) “parabolic” - masses of nuclei ≈ M_ch, with the evolution ending in an SNI outburst; 3) “elliptical” with nuclei masses < M_ch. The latter type of evolution leads to the formation of planetary nebulae and white dwarfs. A new hypothesis is suggested that explains more frequent occurrence of SNI in irregular galaxies by flashes of star formation.     

Actual performance and capabilities of the Argos system

Since 1978, a new operational platform location system has come into being, namely the Argos system, which has the great advantage of bringing all results together at a single point. At the same time, this system provides for measurement data collection from platforms equipped with a simple electronics package, wherever they may be in the world.The data relayed by this system concern all environment-related disciplines, irrespective of whether we are referring to land masses, oceans, polar regions or the atmosphere.The central point where all location calculations are performed and all collected data handled is the Toulouse Space Center. Results are available at the Center just a few hours after their acquisition. Users can consult the results files via switched communications networks or have the data sent to them in one form or another.     

Low-mass bare strange stars

Strange stars with low masses are suggested to exist in reality, the origin of which could be via accretion-induced collapse of white dwarfs. Such a strange star is likely bare, and would thus spin very fast, even to a period of <0.1 ms. Strange stars with low masses may differ from those with solar masses in various astrophysical appearances. Observations to test this “low-mass” idea are proposed.     

航天技术综合效益模型探讨

航天飞行器综合效益模型是在运用系统思想和投资——消耗理论基础上建立起来的动态模型,包括一般效益模型和优化效益模型。通过系统分析,对卫星、平台和空间站的实用,可获得综合效益值,并用工程估算法校核计算,证明效益动态模型的定量计算可行而且可信,对效益分析计算,具有一定的普遍意义。它又指明:为获取较高的航天技术的效益,不仅需要大量投资,而且要讲究投资策略;在整个投资周期内坚持饱和水准M 可变是提高效益的一条好途径,也是今后要加强研究的重要课题。     

Indicators of black-hole mass and Eddington accretion ratio from QSO X-ray and UV spectra

The evolution of luminous QSOs is linked to the evolution of massive galaxies. We know this because the relic black-holes found locally have masses dependent on the properties of the host galaxy’s bulge. An important way to explore this evolution would be to measure dependences of black-hole masses and Eddington accretion ratios over a range of redshifts, i.e., with cosmological age. For low redshift QSOs (and their lower luminosity Seyfert galaxy counterparts) it has been possible to infer black-hole masses from the luminosities and velocity dispersions of their host-galaxy bulges. These masses agree with those virial black-hole masses calculated from the Doppler widths of the broad Hβ emission lines. The latter method can then be extended to more distant and luminous QSOs, up to redshifts of 0.6 with ground-based optical observations. We discuss ways to extend these explorations to higher redshifts – up to 3 using the widths of QSOs’ broad UV emission lines, and in principle, and to redshifts near 4 from ground-based infrared observations of rest-frame Hβ at 2.5 μm. We discuss the possibility of investigating the accretion history of the higher redshift QSOs using measures of Eddington accretion ratio – the soft X-ray spectral index and the eigenvectors of Principal Components Analyses of QSOs’ UV emission-line spectra.     

单级入轨运载器推进系统方案分析

选择了九种双组元和三组元发动机系统方案,计算了各种方案发动机的性能和质量。当单级入轨运载器主推进系统由这些发动机组成时,计算和分析了推进系统的组成方式对运载器干质量的影响。计算结果表明,当推进系统全部由三组元发动机组成时,运载器干质量最小。     

飞行控制系统传感器故障的检测及校正

飞行控制系统必须具有很高的可靠性,本文给出了一种控制系统故障检测与估计的修正偏差分离估计方法,并将该方法应用到飞行控制系统传感器的故障检测及校正中。为验证该方法的有效性,用一个简化纵向飞行系控制统进行了模拟,结果表明,该方法很有效。     

Water movement on the convex surfaces of porous media under microgravity

A plant growth system for crop production under microgravity is part of a life supporting system designed for long-duration space missions. A plant growth in soil in space requires the understanding of water movement in soil void spaces under microgravity. Under 1G-force condition, on earth, water movement in porous media is driven by gradients of matric and gravitational potentials. Under microgravity condition, water movement in porous media is supposed to be driven only by a matric potential gradient, but it is still not well understood. We hypothesized that under microgravity water in void spaces of porous media hardly moved comparing in void spaces without obstacles because the concave surfaces of the porous media hindered water movement. The objective of this study was to investigate water movement on the convex surfaces of porous media under microgravity. We conducted parabolic flight experiments that provided 20–25?s of microgravity at the top of a parabolic flight. We observed water movement in void spaces in soil-like porous media made by glass beads and glass spheres (round-bottomed glass flasks) in the different conditions of water injection under microgravity. Without water injection, water did not move much in neither glass beads nor glass spheres. When water was injected during microgravity, water accumulated in contacts between the particles, and the water made thick fluid films on the particles surface. When the water injection was stopped under microgravity, water was held in the contacts between the particles. This study showed that water did not move upward in the void spaces with or without the water injection. In addition, our results suggested that the difficulty of water movement on the convex (i.e. particle surfaces) might result in slower water move in porous media under microgravity than at 1G-force.     

系统电磁兼容技术综述与展望

系统电磁兼容问题已成为飞行器等大型复杂系统全寿命周期中必须面对的客观问题。如果解决不当,不仅带来大量研制经费的浪费,同时还将导致系统从根本上丧失使用能力。系统电磁兼容问题不同于设备分系统电磁兼容问题,无论是在分析方法、设计方法、试验方法方面,均为系统工程问题。重点围绕航空飞行器研制中的电磁兼容问题,介绍一种全新的系统电磁兼容设计方法:飞机整机电磁兼容精确化协同优化设计方法。该方法有效实现了从飞机总体角度进行全机电磁兼容性设计和从飞机顶层高度提出全机电磁兼容量化指标要求。该技术不但可以实现全机电磁兼容问题在过程中得到管理和控制,并且实现了飞机全机电磁兼容设计的一次性成功,从电磁兼容角度保证了飞机的安全性。     

自适应卡尔曼滤波实时性研究及其应用

自适应卡尔曼滤波在估计系统状态的同时，也估计系统噪声统计值，因而计算量很大，通常在实际的应用中，其实时性很难保证。通过在ＴＭＳ３２０Ｃ３０芯片上实现惯性导航系统／全球定位系统（ＩＮＳ／ＧＰＳ）组合导航系统的自适应卡尔曼滤波可以看出，采用ＴＭＳ３２０Ｃ３０芯片来解决自适应卡尔曼滤波的实时性问题是可行的。     

产品数据管理系统中PPOR模型研究与实践

面对数量和体积急剧增长的产品设计信息,企业必须加强产品数据信息管理.尽管从不同的产品数据管理的观点看,有不同的产品数据管理系统,但仍然有一些基本特性是一致的,总结并提出了产品数据管理应当满足的几项原理.PDM(Product Data Management)内涵是集成并管理与产品有关的信息与过程,因此对产品数据管理中的数据管理模型的研究是实现产品数据管理系统的关键步骤.PPOR模型分别是指产品(Product)管理模型、过程(Process)数据管理模型、组织(Organization)管理模型和资源(Resource)管理模型,各模型之间相互关联,构成了产品信息管理的框架.这些模型都用EXPRESS-G语言描述,并且按此实现了基于STEP标准的原型系统.