敏捷制造数据源及其实现技术

为满足产品全生命周期管理对制造数据敏捷性的需求,提出一种敏捷制造数据源的数据管理方法.分析了敏捷制造数据的应用需求,将敏捷数据源定义为一种面向产品生命周期不断变化应用需求的数据定义和管理架构,该架构包括核心对象与本体层、元数据元模型层、服务组件层以及实施层等4个层次,对该架构的特点进行了分析.提出了实现敏捷制造数据源的3个实现技术,分别是抽象元建模技术、基于规则的数据视图快速生成技术以及基于服务技术的组件重用与快速重构技术.所提出的敏捷制造数据源为支持产品生命周期内制造数据的敏捷管理、应用以及提升应用信息系统敏捷性提供了新的途径.     

Multi-objective output-feedback control for microsatellite attitude control: An LMI approach

Mixed H₂/H_∞ output-feedback controller with pole placement constraints against the internal uncertainty of moment-of-inertia variation and space environmental disturbances is proposed for mircosatellite attitude control. The multi-objective controller is designed based on linear model of attitude dynamics. The H_∞ performance takes into account both robustness stability against moments-of-inertia uncertainty and the disturbance rejection aspect. H₂ performance takes into account the LQG aspect which avoids the undesirable wheels’ saturation effect. In addition, the closed-loop poles can be forced into some sector of the stable half-plane to obtain well-damped transient responses. The problem is then reduced to a convex optimization involving linear matrix inequalities (LMIs), so it can be efficiently solved. The simulation results demonstrate that the presented mixed H₂/H_∞ control system is robust stable and optimal in the sense of H₂ norm, and has good steady-state and dynamic performances against the parameter uncertainties and various disturbances for the microsatellite attitude control system.     

强信号背景下弱信号角度时延的联合Capon估计方法

针对强信号背景下弱信号角度时延联合估计过程中的弱信号数目难以精确估计问题,在分析Capon谱估计法估计信号DOA原理的基础上,将Capon谱估计法进行扩展,提出了一种在强信号背景下弱信号角度时延联合估计方法。为弥补Capon法分辨力较差的劣势,将扩展的Capon法与有高分辨性能的m-Capon算法结合,提出了一种改进的m-Capon方法,能区分来波方向接近的不同目标信号。研究和仿真结果表明:该方法无需对弱信号的信源数进行估计,也无需分解特征值,且在快拍数较少时仍具适用性。     

Dawn′s exploration of Vesta

On 16 July 2011, after completing nearly four years of interplanetary flight, Dawn entered orbit around (4) Vesta, the second most massive body in the main asteroid belt. Dawn used solar electric propulsion to spiral to six different orbits to accomplish its science campaign. Although the transfers to progressively lower orbits presented significant challenges, all were executed smoothly. During its nearly 14 months in orbit, Dawn spiraled down to 210 km above the surface and back up before initiating the gradual departure to travel to dwarf planet (1) Ceres for a 2015 rendezvous. Dawn′s exploration of Vesta has shown it to be geologically complex and fascinating, resembling terrestrial planets more than typical asteroids. Among the principal features is a 500-km-diameter impact basin within which is the second tallest mountain known in the solar system. This paper presents Dawn′s operations at Vesta and summarizes the principal findings.     

求根传播算子方法及其在ARM抗诱偏中的应用

反辐射导弹（ARM）抗有源诱偏问题中,多源信号在空、频域的强相关性往往造成导引头对信源数目欠估计,从而导致传统超分辨算法的测向性能下降。针对这一问题,提出了一种求根的传播算子方法,该算法首先在信源数过估计情况下计算信号到达角,然后利用每个角度对应的信号功率来剔除虚假角度。求根传播算子方法不需要预先估计信号源数目,而且在信号高度相关的情况下具备很好的角度分辨性能,因此适用于解决ARM抗诱偏问题。仿真实验结果表明,求根传播算子方法在提高ARM抗诱偏能力方面的表现优于MUSIC算法。     

高级波束成形在旋转声源定位中的应用

为了使高级波束成形中的函数波束成形、压缩感知波束成形、正交波束成形在旋转声源定位中获得广泛应用,对3种高级波束成形在旋转声源定位中的应用进行了研究,从声源空间分辨率,动态范围以及声源功率积分上与传统旋转波束成形和DAMAS(deconvolution approach for the mapping of acoustic sources)反卷积作对比。仿真与实验结果表明:3种高级波束成形均可以应用到旋转声源定位中,并且均能显著提升旋转声源空间分辨率和动态范围以及拥有较高的计算效率。函数波束成形在低频段的空间分辨率低于DAMAS并且容易产生较高的声源功率积分误差。压缩感知波束成形整体性能与DAMAS相近,并且在低频段的空间分辨率比DAMAS有优势。正交波束成形在低频段容易产生声源定位位置误差,抗干扰能力较弱,并且声源功率积分整体低于DAMAS。      

基于参数自整定模糊PID控制的大型液压源温控系统设计

根据液压源温度控制系统的非线性、时变的大滞后特性,采用参数自整定模糊比例积分微分(PID)控制算法,通过模糊推理在线调整PID的3个参数,给出了PID参数在线整定原则和模糊控制器设计。仿真结果表明:用该法设计的控制器较传统PID控制器有更好的动态性能和鲁棒性。不同工况的实验验证其液压源油温控制精度达到文献[1]的B级要求(±2℃)。     

Electric field and ion density anomalies in the mid latitude ionosphere: Possible connection with earthquakes?

The problem of earthquake prediction has stimulated the search for a correlation between seismic activity and ionospherical anomalies. We found observational evidence of possible earthquake effects in the near-equatorial and low latitude ionosphere; these ionospheric anomalies have been proposed by Gousheva et al. [Gousheva, M., Glavcheva, R., Danov, D., Angelov P., Hristov, P., Influence of earthquakes on the electric field disturbances in the ionosphere on board of the Intercosmos-Bulgaria-1300 satellite. Compt. Rend. Acad. Bulg. Sci. 58 (8) 911–916, 2005a; Gousheva, M., Glavcheva, R., Danov, D., Angelov, P., Hristov, P., Kirov, B., Georgieva, K., Observation from the Intercosmos-Bulgaria-1300 satellite of anomalies associated with seismic activity. In: Poster Proceeding of 2nd International Conference on Recent Advances in Space Technologies: Space in the Service of Society, RAST ‘2005, June 9–11, Istanbul, Turkey, pp. 119–123, 2005b; Gousheva, M., Glavcheva, R., Danov, D., Angelov, P., Hristov, P., Kirov, B., Georgieva, K., Satellite monitoring of anomalous effects in the ionosphere probably related to strong earthquakes. Adv. Space Res. 37 (4), 660–665, 2006]. This paper presents new results from observations of the quasi-static electric field and ion density on board INTERCOSMOS-BULGARIA-1300 satellite in the mid latitude ionosphere above sources of moderate earthquakes. Data from INTERCOSMOS-BULGARIA-1300 satellite and seismic data (World Data Center, Denver, Colorado, USA) for magnetically quiet and medium quiet days are juxtaposed in time-space domain. For satellite’s orbits in the time period 15.09–01.10.1981 an increase in the horizontal and vertical components of the quasi-static electric field and fluctuations of the ion density are observed over zones of forthcoming seismic events. Some similar post effects are observed too. The emphasis of this paper is put on the anomalies which specify the mid latitude ionosphere. The obtained results contain important information because they confirm our previous results for near-equatorial and low latitude regions.