飞机数字化装配工艺仿真技术

利用产品的三维数字样机,对产品的装配过程统一建模,在计算机上实现产品从零件、组件装配成产品的整个过程的模拟和仿真.这样,在建立了产品和资源数字模型的基础上,就可以在产品的设计阶段模拟出产品的实际装配过程,而无需实物样机.     

面向开发过程的产品结构形式化建模

为满足开发过程产品结构数据的动态结构配置、动态任务协作、动态目标求解、动态状态跟踪等应用需要,在对开发过程产品结构属性及其相互关系进行分析的基础上,提出了一种面向开发过程应用的产品结构形式化模型.结合产品开发活动的时域行为特征,给出了产品结构的时域定义,并以此为基础构建了产品结构模型的时域扩展定义.通过分析产品状态与开发任务时域行为的映射关系,在产品结构时域扩展定义的基础上,提出了基于时间截面的开发过程产品结构状态追踪方案及算法,并通过模拟产品对象在开发过程中的状态变迁过程,验证了模型及相关应用方案的实用性和有效性.      

A reappraisal of the habitability of planets around M dwarf stars

Stable, hydrogen-burning, M dwarf stars make up about 75% of all stars in the Galaxy. They are extremely long-lived, and because they are much smaller in mass than the Sun (between 0.5 and 0.08 M(Sun)), their temperature and stellar luminosity are low and peaked in the red. We have re-examined what is known at present about the potential for a terrestrial planet forming within, or migrating into, the classic liquid-surface-water habitable zone close to an M dwarf star. Observations of protoplanetary disks suggest that planet-building materials are common around M dwarfs, but N-body simulations differ in their estimations of the likelihood of potentially habitable, wet planets that reside within their habitable zones, which are only about one-fifth to 1/50th of the width of that for a G star. Particularly in light of the claimed detection of the planets with masses as small as 5.5 and 7.5 M(Earth) orbiting M stars, there seems no reason to exclude the possibility of terrestrial planets. Tidally locked synchronous rotation within the narrow habitable zone does not necessarily lead to atmospheric collapse, and active stellar flaring may not be as much of an evolutionarily disadvantageous factor as has previously been supposed. We conclude that M dwarf stars may indeed be viable hosts for planets on which the origin and evolution of life can occur. A number of planetary processes such as cessation of geothermal activity or thermal and nonthermal atmospheric loss processes may limit the duration of planetary habitability to periods far shorter than the extreme lifetime of the M dwarf star. Nevertheless, it makes sense to include M dwarf stars in programs that seek to find habitable worlds and evidence of life. This paper presents the summary conclusions of an interdisciplinary workshop (http://mstars.seti.org) sponsored by the NASA Astrobiology Institute and convened at the SETI Institute.     

电推进航天器的特殊环境及其影响

文章介绍了应用离子和霍耳电推进系统在航天器周围产生的等离子体和电磁场等特殊环境,讨论了这些特殊环境对航天器各分系统或部件产生的溅射腐蚀、沉积污染、充放电、等离子体干扰、碰撞动力学扰动等影响效应,探讨了研究电推进与航天器相互作用效应的地面试验技术、空间飞行试验技术和模型分析技术,介绍了离子电推进系统与航天器相容性分析评价的技术要点。     

动力增升飞行LQG/LTR鲁棒控制器设计

研究线性高斯二次型回路传输恢复(LQG/LTR)鲁棒设计方法在动力增升阶段飞行/推进综合控制器设计中的应用问题,以带宽和Gibson准则作为基本的飞行品质指标,以奇异值作为鲁棒性指标,深入分析了基于LQG/LTR鲁棒控制的参数选择规律,包括姿态和速率指令的分配、前置滤波器的影响、扰动水平的预设、高频环节对系统鲁棒性和飞行品质的影响等问题.示例飞机构形的控制器设计结果表明:在LQG/LTR鲁棒飞行控制器设计过程中,适当选取响应类型参数和扰动水平因子,可以折衷飞机的飞行品质和鲁棒性能.      

高超声速串联式组合动力装置方案

为保证高超声速运输机在宽广的飞行包线内(Ma＝0~5,H=0~30km)稳 定可靠工作,对涡轮/冲压组合动力装置串联方案展开研究.首先建立了经试验数据校核的 适于高超声速飞行的组合动力装置部件级变循环详细非线性性能计算模型;在此基础上,利 用发动机设计点热力循环分析和非设计点性能分析方法对串联方案的综合特性进行评估,最 终给出一种经过优化的串联布局涡扇/冲压组合动力装置总体性能设计方案.研究结果表明 ,优化方案可有效地缩小组合发动机的结构尺寸与重量,有利于进气道,喷管的调节以及冲 压燃烧室燃烧的组织.通过综合调整发动机5个可调几何部位以及涡轮发动机燃油流量和冲 压燃烧室燃油流量,可以实现涡扇/冲压模式的平稳转换.      

在MSC.PATRAN中机翼有限元模型加载模块的二次开发

介绍了使用PCL语言对强度计算软件MSC.PATRAN进行二次开发程序编制的方法,以及开发机翼有限元模型加载模块的过程,为在MSC.PATRAN中增加计算模块提供了方法和思路。该计算模块已应用于具体型号的强度设计分析中。     

一种用于反辐射导弹的被动红外导引头方案设想

文章介绍了一种用于复合制导反辐射导弹的被动红外导引头的方案设想。以美制某型防空导弹系统的探测雷达作为设想打击目标,结合目标特性对红外导引头相关技术指标进行了分析,介绍了导引头的总体方案。     

Model development and adaptive imbalance vibration control of magnetic suspended system

A system model is developed to describe the translational and rotational motion of an active-magnetic-bearing-suspended rigid rotor of a single-gimbal control moment gyro (SCMG) onboard a rigid satellite. This model closely reflects the motion characteristics of the rotor by considering the dynamic and static imbalance as well as the coupling between the gimbal's and the rotor's motion on a satellite platform. Adaptive autocentering control is strictly constructed for the preceding rotor with unknown dynamic imbalance. The rotor achieves its rotation about the principal axis of inertia by identifying the little rotational angles from the geometric axis to the principal axis and then using the results to tune a stabilizing controller, which is composed of a decentralized PD controller with cross-axis proportional gains and high-pass and low-pass filters. The main disturbance in the wheel spinning can thereby be completely removed and the vibration acting on the satellite can be attenuated.     

发射箱导轨用石墨填充碳/酚醛复合材料研究

采用石墨填充碳/酚醛模压复合材料技术成形导轨面材料,通过试验,研究和分析了材料各组分对材料摩擦磨损性能的影响。试验结果表明,在石墨含量为10%,碳纤维含量为30%时,石墨、碳纤维填充酚醛树脂复合材料的摩擦磨损性能、烧蚀性能较好,且摩擦系数低,适于用作导轨表面材料。