Active detumbling technology for noncooperative space target with energy dissipation

Space debris is generally a kind of tumbling noncooperative space target which poses a serious threat to human space activities. In active debris removal (ADR) missions, capturing a space target directly may cause damage to space manipulator and chaser satellite, so it is a feasible strategy to reduce the angular velocity of space target to an acceptable range in the pre-capture phase. In this paper, an active detumbling technology for a free-floating tumbling space target with energy dissipation is studied, and an effective detumbling method utilizing intermittent contact impact between the space target and despin mechanism is proposed. First, the dynamic model of the space target is set up by the Jourdain’s velocity variation principle. Then, a contact model between the space target and despin mechanism is established based on the Hertz contact theory and the method of computer graphics. Finally, the detumbling method is validated by numerical simulations. Simulation results show that our method can reduce the angular velocity of the space target effectively without causing large nutation.     

多源多出复杂压缩空气管网建模及能效分析

针对多源多出的复杂压缩空气管网, 通过分析管网的拓扑结构、压缩空气的压力损失规律以及压力与流量的联动特点,建立了管网矩阵模型,并基于所建数学模型,确定了管网中压缩空气压力和流量间的对应关系.能够根据管网中用气点的流量或压力波动,快速预测出管网中可能出现的压力或流量波动,为准确地用气预测提供了一种解决思路,同时为管网的能效分析奠定了基础.     

基于故障树和快照技术的无人机特情训练方法

针对无人机操作手在执行任务时不能有效地识别与处置特情的难题,提出了一种基于故障树遍历分析和快照技术的无人机特情模拟训练方法,并以样例无人机为研究案例进行了关键技术解析、通用化特情训练系统设计实现和试验.利用故障树理论,建立完备的无人机故障树模型,分析了需重点模拟训练的特情.利用快照技术,实现了不同飞行阶段训练的解耦;结合RTW（Real-Time Workshop）技术、数据库技术和视景仿真技术,完成了通用化无人机特情训练系统的开发,并成功应用于某型无人机的特情训练.给出了样例无人机操作手在不同方法下的训练结果,通过统计数据对比,表明该方法与常规的方法相比,训练效率更高,训练的完备度更好.     

GLONASS-based precise point positioning and performance analysis

Current precise point positioning (PPP) techniques are mainly based on GPS which has been extensively investigated. With the increase of available GLONASS satellites during its revitalization, GLONASS observations were increasingly integrated into GPS-based PPP. Now that GLONASS has reached its full constellation, there will be a wide interest in PPP systems based on only GLONASS since it provides a PPP implementation independent of GPS. An investigation of GLONASS-based PPP will also help the development of GPS and GLONASS combined PPP techniques for improved precision and reliability. This paper presents an observation model for GLONASS-based PPP in which the GLONASS hardware delay biases are addressed. In view of frequently changed frequency channel number (FCN) for GLONASS satellites, an algorithm has been developed to compute the FCN for GLONASS satellites using code and phase observations, which avoids the need to provide the GLONASS frequency channel information during data processing. The observation residuals from GLONASS-based PPP are analyzed and compared to those from GPS-based PPP. The performance of GLONASS-based PPP is assessed using data from 15 globally distributed stations.     

Electrostatic gravity gradiometer design for the future mission

Satellite gravity gradiometry has been applied in GOCE mission to obtain higher harmonics of the Earth’s gravity mapping. In-orbit results showed that the precision of GOCE gradiometry achieved a level of 10–20 mE/Hz^1/2 in the bandwidth of 38–100 mHz, and the major error source came from the intrinsic noise of the core sensor electrostatic accelerometer. Two schemes for improving sensitivity of such accelerometer are presented by optimizing the parameters to reduce the dynamic range and choosing the heavier proof mass to suppress the thermal noise limited by the discharging gold wire. As a result, an accelerometer with a better resolution of 6.6×$6.6\times$10⁻¹³ m/s²/Hz^1/2 could be developed, and then a precision of 3 mE/Hz^1/2, corresponding to a spatial resolution of about 78 km half wavelength, is achievable for the future satellite gradiometric mission.     

航空发动机振动传递特性研究进展

航空发动机振动传递规律是业内研究热点之一。为了控制整个机械系统振动传递,通过找到振动能量的传递主要路 径,进行了结构优化和参数设计。介绍了航空发动机振源机理及研究进展,分别对航空发动机规律性激振源与非规律性激振源进 行了系统地论述,总结了国内外关于转子系统故障的研究情况;详细分析了传递路径分析方法及其衍生方法相关技术的优点以及 近年来传递路径分析法（TPA）、工况传递路径分析法（OTPA）、扩展工况传递路径分析法(OPAX)等传递路径分析方法在汽车、地 铁、船舶、航空领域中的应用,指出了不同传递路径分析方法存在的问题;对航空发动机整机振动传递特性研究的发展趋势进行了 展望。由于振动传递路径分析方法在航空发动机领域并未系统开展,分类综述了航空发动机整机振动传递特性研究成果,搜集整 理了应用于转子-轴承-机匣-吊挂系统振动传递分析方法,可为航空发动机整机振动传递特性研究提供参考。     

提高锻模寿命的途径

针对锻模在使用过程中常见的两种失效形式 ,即热磨损和热疲劳裂纹 ,分析了其产生的原因 ,并提出了为提高锻模寿命而应采取的措施     

A new method to predict fatigue crack growth rate of materials based on average cyclic plasticity strain damage accumulation

By introducing a fatigue blunting factor, the cyclic elasto-plastic Hutchinson-Rice-Rosengren (HRR) field near the crack tip under the cyclic loading is modified. And, an average damage per loading-cycle in the cyclic plastic deformation region is defined due to Manson-Coffin law. Then, according to the linear damage accumulation theory-Miner law, a new model for predicting the fatigue crack growth (FCG) of the opening mode crack based on the low cycle fatigue (LCF) damage is set up. The step length of crack propagation is assumed to be the size of cyclic plastic zone. It is clear that every parameter of the new model has clearly physical meaning which does not need any human debugging. Based on the LCF test data, the FCG predictions given by the new model are consistent with the FCG test results of Cr2Ni2MoV and X12CrMoWVNbN 10-1-1. What’s more, referring to the relative researches, the good predictability of the new model is also proved on six kinds of materials.     

风机叶片用缝编织物渗透性能评估

在渗透性能测试方法归纳介绍的基础上,开展了试验及比较,初步确定了相应的测试试验规范.结合风机叶片的具体工艺和使用部位等,初步选定了缝编织物的渗透性能评估参数和测试方法,以对风机叶片用缝编织物渗透性能测试评估方法的统一规范确定提供一些思路.     

气-气冷流掺混流场缩尺技术

 为研究气-气冷流掺混流场缩尺技术,对多组分气相掺混流动三维Navier-Stokes无量纲方程及其定解条件进行了相似性分析,并将量纲分析方法应用到气-气掺混流动现象中,获得了气-气掺混流场相似准则,该相似准则表明冷流掺混试验件尺寸和试验背压都可以变化;运用该准则,在不同背压工况下进行了3个不同尺寸试验件的单喷嘴气-气喷注器掺混流场的仿真分析和比较,结果表明不同试验件尺寸和不同压力工况下气-气掺混流场具有相似性。研究结果能够指导气-气冷流试验,并为气-气燃烧流场缩尺技术研究提供参考。