PILOT:一个智能化的分布式系统管理器

NASA约翰逊航天中心正在作一系列研究,探索提高当前和未来载人指控中心工作效率和实用性的途径。实时数据系统(RTDS)工程已研究了几种技术并用于指控中心环境。该环境是以工程工作站构成的多机种网络,该网中仿真的和实际的航天飞机任务现场数据作实时分配。该系统由一组复杂的交互进程组成,必须以最少的停顿时间提供多种服务。本文介绍一些能保证系统各功能高度可靠和高度可用的方法。包括一个进程可见性工具,一个本地工作站环境监视器,一个网络级通信工具和一个采用人工智能技术的全局进程。     

实时OTF动态GPS系统定位结果

1988年,美国陆军工程部正式开始研究利用GPS载波相位的实时定位系统。该项研究的最终目标是在1993年做成一台实用样机,能实时获得厘米级的三维定位精度。这一目标实现了,1993年3月开始对样机进行测试。1993年8月进行了首次演示,10月进行了首次公开演示。该设备一般能在“动中”(OTF)15秒时间内分辨模糊整周数,不需要作静态初始化。任一相距20km左右的移动平台可利用该设备进行可靠而稳健的精密定位。在各种工作条件下作了试验,以评价动平台精密定位OTF解模糊的极限。本文总结了这些试验的结果。早期所作的实时试验证明三维方向的定位精度可达1—3cm。本文还介绍了最终实时系统的设计方案以及与水文监测平台的结合问题。     

得到市场推动的庞巴迪CRJ-700

庞巴迪宇航集团新近启动的加拿大飞机公司研制的“地区喷气”(CRJ)700系列客机,已获得首家客户法国不列特航空公司的4架确定订货。首架订货计划于2000年第四季度交付。 新的70座CRJ-700为50座的CRJ的加长型。除不列特公司的订货外,它还吸引了来自另外7家航空公司的63架有条件订货、意向订货和备忘录协议订货(全部付有保证金)。尽管这些客户大都未被公布名称,但据说是目前CRJ的用户和初次考虑采用支线喷气机的客户。     

选用陀螺仪—动调陀螺,激光陀螺,光纤陀螺的比较

本文对现有陀螺仪技术：动调陀螺，激光陀螺和光纤陀螺作了综述。作者以一位系统工程师的观点对这些技术作了比较并列出了不同种类陀螺仪的优、缺点。     

用于飞行器动态控制系统的偏航速率传感器

自１９９５年初以来，ＲｏｂｅｒｔＢｏｓｃｈ开始了飞行器动态控制系统的生产。本文将介绍这一系统的关键部件－偏航速率传感器。     

支援干扰发展趋向探讨

战术支援干扰只有与日趋复杂的威胁系统和战术同步发展,才能保持其威力。一、干扰系统要求大功率机载干扰系统,用干扰敌方防空系统及其有关的指挥、控制与通信(C~3)网络来保护我方飞机。实施战术支援干扰决非易事,干扰系统必须处理许多问题,诸如自卫干扰机、威胁告警接收机以及其它复杂问题。支援干扰的主要任务是,通过远处干扰来保护沿不同飞行途径飞行的各种飞机。故要求它具有以下独特功能:1)特大的功率,至少要比常规自卫干扰机的功率大一千倍。这样,支援干扰机才能通过     

Finger heat flux/temperature as an indicator of thermal imbalance with application for extravehicular activity

The designation of a simple, non-invasive, and highly precise method to monitor the thermal status of astronauts is important to enhance safety during extravehicular activities (EVA) and onboard emergencies. Finger temperature (Tfing), finger heat flux, and indices of core temperature (Tc) [rectal (Tre), ear canal (Tec)] were assessed in 3 studies involving different patterns of heat removal/insertion from/to the body by a multi-compartment liquid cooling/warming garment (LCWG). Under both uniform and nonuniform temperature conditions on the body surface, Tfing and finger heat flux were highly correlated with garment heat flux, and also highly correlated with each other. Tc responses did not adequately reflect changes in thermal balance during the ongoing process of heat insertion/removal from the body. Overall, Tfing/finger heat flux adequately reflected the initial destabilization of thermal balance, and therefore appears to have significant potential as a useful index for monitoring and maintaining thermal balance and comfort in extreme conditions in space as well as on Earth.     

Discrimination of aqueous and aeolian paleoenvironments by atomic force microscopy-- a database for the characterization of martian sediments

In the search for aqueous habitats on Mars direct proof of (ancient) flowing water is still lacking, although remote sensing has provided indications of young fluvial systems. To demonstrate that such proof can be given, we examined surface marks on recent terrestrial sand grains by atomic force microscopy (AFM) and applied a quantitative three-dimensional analysis that can numerically distinguish between aeolian and aquatic transport mechanisms in sedimentary deposits on Earth. The surfaces of natural quartz grains as well as olivine, feldspar pyroxene, and monazite sands of known origin were imaged, each image yielding a three-dimensional map of the mineral surface. A fully automated analysis of distribution patterns of the structural elements that constitute the grain surfaces shows that wind-transported quartz grains have short linear elements irregularly distributed on the surface. Linear elements on water-transported grains, however, are longer with orientations that reflect the mineral symmetry. Because the surface patterns found on aqueous grains are due to preferential etching, they can be used as diagnostic fingerprints for the existence of past or present aqueous transport systems. We used a cluster analysis of the cross-correlation distance of distribution patterns in the structures of aeolian and aquatic sand grains to build a phenogram that provides a map for the relationship of the various sediments found on earth. The analysis shows that the method is highly significant and that water and wind transport can clearly be differentiated. In particular, feldspar and olivine sands contributed even more to the discrimination than quartz grains, which indicated that the method is promising for its application on future missions to Mars. Assuming that martian aqueous sand grains exhibit similar erosional patterns to mineral grains on Earth, simple AFM experiments on a Mars lander would be capable of proving the activity of flowing water in modern runoff systems and of analyzing the paleoenvironments of Mars.     

OPTIMAL CONTROL OF REDUNDANT ROBOTS WITH LOCAL DEGREES OF FREEDOM

SupportedbytheNationalNaturalScienceFoundationofChinaRedundantrobotsprovideflexibilityinavarietyoftasks.Methedsusedtodevelopthere-dundancycontrolarewellknown[1~4J-Inthesemethods,kinematicflexibilityisensuredwhiledynamicperformanceisbeingimproved.Itisverydifficult,however,toimplementoptimalredundancycontrolthatsimultaneouslyincludesbothkinematicsanddynamics(dual-optimiza-tion)forrobotmechanismsthathavebeenpreviouslydeveloped.Inthefollowingsections,aredundantrobotmechanismhavinglocaldegreesof…