基于浸入与不变理论的航天器姿态跟踪自适应控制

针对惯性参数不确定的航天器姿态跟踪控制问题，基于浸入与不变（I&I）方法设计出了一种新的姿态跟踪控制器。研究结果表明，传统的浸入与不变方法运用到姿态跟踪模型，存在参数回归矩阵不可积进而导致偏微分方程无解析解的问题。针对该问题，提出了一种对回归矩阵改造使其满足可积条件的方法，通过动态放缩技术消除了回归矩阵改造前后的差异对闭环系统稳定性的影响，设计出了一种新的航天器姿态跟踪自适应控制器。通过李雅普诺夫稳定性分析方法证明了所设计的控制器能够保证闭环系统的全局渐近稳定性。相对于已有的基于动态放缩法的浸入与不变控制器，设计了一种全新的缩放因子，使得控制器的执行不需要缩放因子的信息，并且也不需要惯量矩阵的先验信息。最后，仿真对比实验进一步验证了所设计控制器的有效性和优越性。     

转子叶片径向受限的“冲击-气膜出流”冷却结构流动与换热

为揭示转子叶片径向受限的"冲击-气膜出流"冷却结构流动换热规律,以某型双层壁叶片肋化分割形成的冷却单元为研究对象,通过数值模拟的方式,对冲击雷诺数Rej,旋转数Ro,无因次温比(Tw-Tf)/Tw等参数变化下流场和换热特性变化规律展开研究。结果表明:在哥氏力和离心力作用下,受限空间内存在射流偏转、径向二次流动以及二次冲击等现象;流动的径向受限可抑制射流偏转,强化冲击换热;相同的旋转数Ro下,逆转向冲击(叶背区)换热努赛尔数Nu比顺转向冲击(叶盆区)高8%。在研究的参数范围内,数值模拟和试验结果说明径向受限周向出流结构能有效的抑制旋转对换热的削弱。     

岁差章动模型更新等因素对坐标转换的影响

GCRS(Geocentric Celestial Reference System,地心天球参考系)与ITRS(International Terrestrial Reference System,国际地球参考系)之间的坐标转换方法与岁差章动模型密切相关,IERS(International Earth Rotation and reference systems Service,国际地球自转与参考系服务)规范先后推荐了3组不同的岁差章动模型。论文分析了基于春分点的坐标转换过程,在比较3组岁差章动模型间差异的基础上,以太阳系10个天体为例,计算了岁差章动模型更新、极移、世界时与地球时差值等因素对坐标转换影响的具体数值。结果表明,IAU 2006岁差-IAU 2000AR06章动与IAU 2000岁差-IAU 2000A章动间的差异,对坐标转换的影响在0.5mas以内;而IAU1976岁差-IERS 1996章动与前2组岁差章动间的差异,对坐标转换影响的最大值达到37mas;极移对坐标转换影响的最大值达到0.6″,远高于岁差章动模型更新所带来的影响;当忽略世界时与地球时的差异时,结果完全错误。通过此分析,明确了极移、世界时与地球时的差异对坐标转换影响的具体数值,可为工程计算中岁差章动模型的选取提供参考依据。     

有无蜂窝的直通斜齿流动特性旋转实验研究

为了研究蜂窝对直通斜齿流动特性的影响,在光滑衬套和蜂窝衬套条件下的高速旋转篦齿实验台上,分别测量了工作间隙和流动特性随转速0～8700r/min和压比1.1～1.5的变化规律。实验结果表明:随着转速的增加,泄漏量下降了约50%,流量系数下降了约25%,风阻温升达到40K;随着压比的增加,泄漏量和流量系数也相应增加;蜂窝衬套相对于光滑衬套,流量下降了约20%,流量系数下降了约10%,风阻温升差异微小。蜂窝可以使篦齿流量及流量系数降低,提升封严性能,对风阻温升影响很小。     

A new simpler rotation/curvature correction method for Spalart-Allmaras turbulence model

 A new and much simpler rotation and curvature effects factor, which takes the form of Richardson number suggested by Hellsten originally for SST k-x model, is presented for Spalart and Shur's rotation and curvature correction in the context of Spalart-Allmaras (SA) turbulence model. The new factor excludes the Lagrangian derivative of the strain rate tensor that exists in the SARC model, resulting in a simple, efficient and easy-to-implement approach for SA turbulence model (denoted as SARCM) to account for the effects of system rotation and curvature, techniquely. And then the SARCM is tested through turbulent curved wall flows: one is the flow over a zeropressure- gradient curved wall and the other is the channel flow in a duct with a U-turn. Predictions of the SARCM model are compared with experimental data and with the results obtained using original SA and SARC models. The numerical results show that SARCM can predict the rotation-curvature effects as accurately as SARC, but considerably more efficiently. Additionally, the accuracy of SARCM might strongly depend on the rotation-curvature model constants. Suggesting values for those constants are given, after some trials and errors.     

Lorentz Symmetry breaking studies with photons from astrophysical observations

Lorentz Invariance Violation (LIV) may be a good observational window on Quantum Gravity physics. Within last few years, all major gamma-ray experiments have published results from the search for LIV with variable astrophysical sources: gamma-ray bursts with detectors on-board satellites and Active Galactic Nuclei with ground-based experiments. In this paper, the recent time-of-flight studies with unpolarized photons published from the space and ground based observations are reviewed. Various methods used in the time delay searches are described, and their performance discussed. Since no significant time-lag value was found within experimental precision of the measurements, the present results consist of 95% confidence level limits on the Quantum Gravity scale on the linear and quadratic terms in the standard photon dispersion relations.     

压力探针临壁效应的试验研究

在窄通道中测量时（如全台压气机试验），临壁效应会使压力探针的测量结果发生误差。对几种常用型式的压力探针的试验研究表明，由于探针多属非流线形物体，所以其临壁效应的机理与流线形的机翼不同，不应简单套用机翼临壁效应的结论。临壁效应所造成的测量误差与探针的形状有关。     

Mercury’s Interior Structure, Rotation, and Tides

This review addresses the deep interior structure of Mercury. Mercury is thought to consist of similar chemical reservoirs (core, mantle, crust) as the other terrestrial planets, but with a relatively much larger core. Constraints on Mercury’s composition and internal structure are reviewed, and possible interior models are described. Large advances in our knowledge of Mercury’s interior are not only expected from imaging of characteristic surface features but particularly from geodetic observations of the gravity field, the rotation, and the tides of Mercury. The low-degree gravity field of Mercury gives information on the differences of the principal moments of inertia, which are a measure of the mass concentration toward the center of the planet. Mercury’s unique rotation presents several clues to the deep interior. From observations of the mean obliquity of Mercury and the low-degree gravity data, the moments of inertia can be obtained, and deviations from the mean rotation speed (librations) offer an exciting possibility to determine the moment of inertia of the mantle. Due to its proximity to the Sun, Mercury has the largest tides of the Solar System planets. Since tides are sensitive to the existence and location of liquid layers, tidal observations are ideally suited to study the physical state and size of the core of Mercury.     

旋转矢量航姿算法的一种新的表达式

传统的旋转矢量航姿算法一般采用陀螺的角增量输出来构造积分算法，本文将光纤陀螺输出的角速率信号再引入航姿计算，提出一种新的航姿算法表达式，并分析了此算法在圆锥运动输入下的误差。与传统的旋转矢量法比较，新算法具有较高的精度，为改进旋转矢量算法提供了一种新的思路。     

电子角跟踪导引头技术及其应用前景

对电子角跟踪在反辐射导引头中的应用进行了研究。介绍了导引头的组成、电子角跟踪的工作原理和特点。研究了如灵敏度、角跟踪误差、制导信号提取、弹体扰动去耦、角搜索模糊，以及单目标跟踪等关键技术，最后分析了电子角跟踪技术在雷达、单机无源定位、反辐射、救生和机器人等技术领域的应用前景。