周向畸变下轴流压气机的失速预警方法研究及应用

为了探究进气畸变条件下轴流压气机的有效失速预警方法并将其应用于主动控制系统中,在一台低速单转子轴流压气机上对均匀进气和周向畸变条件下的失速预警方法进行了实验研究。实验通过在进口布置高度可调节的插板来产生不同强度的周向畸变,并通过在转子叶顶布置的动态压力传感器测得非定常压力信号,运用自相关、互相关和均方根算法对其进行分析,比较了周向畸变下三种失速预警方法的可靠性。分析结果表明:只有传感器安装在畸变区时自相关和均方根分析才有效;互相关分析不依赖于传感器的安装位置,在畸变区和非畸变区均能有效感受到畸变的影响,且互相关系数随着周向畸变的产生或消失相应地下降或上升,因此在周向畸变下互相关分析为更有效的失速预警方法;最后在基于互相关分析的基础上对该单转子轴流压气机实施了喷气主动控制应用,在24.75%畸变强度条件下,主动喷气能取得9.32%的失速裕度改善,与定常喷气相比,获得几乎相等的失速裕度改善的同时节省了约40%的喷气量。     

Active collision avoidance maneuver under constant thrust

In this paper, the relative position parameters of the target spacecraft are obtained by using the vision measurement and the target maneuver positions are calculated through the isochronous interpolation method. Furthermore, new switch control laws under constant thrust are designed for active collision avoidance maneuver of the chaser along a specified trajectory. The switch control laws are obtained based on the acceleration sequences and the working times of thrusters in three axes which can be respectively computed by the time series analysis method. The perturbations and fuel consumptions are addressed during the computation of the working times.     

Solar magnetic feature detection and tracking for space weather monitoring

We present an automated system for detecting, tracking, and cataloging emerging active regions throughout their evolution and decay using SOHO Michelson Doppler Interferometer (MDI) magnetograms. The SolarMonitor Active Region Tracking (SMART) algorithm relies on consecutive image differencing to remove both quiet-Sun and transient magnetic features, and region-growing techniques to group flux concentrations into classifiable features. We determine magnetic properties such as region size, total flux, flux imbalance, flux emergence rate, Schrijver’s R-value, R^∗ (a modified version of R), and Falconer’s measurement of non-potentiality. A persistence algorithm is used to associate developed active regions with emerging flux regions in previous measurements, and to track regions beyond the limb through multiple solar rotations. We find that the total number and area of magnetic regions on disk vary with the sunspot cycle. While sunspot numbers are a proxy to the solar magnetic field, SMART offers a direct diagnostic of the surface magnetic field and its variation over timescale of hours to years. SMART will form the basis of the active region extraction and tracking algorithm for the Heliophysics Integrated Observatory (HELIO).     

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.     

基于hp自适应伪谱法的固体运载火箭轨迹优化

多级固体运载火箭轨迹优化是一个多阶段多约束的最优控制问题。hp自适应伪谱法融合了有限元法和全局伪谱法的思想,采用双层优化策略对细化单元数和插值基函数的阶次进行自适应调节以满足精度和快速性要求。对基于hp自适应伪谱法的多级固体运载火箭主动段轨迹优化问题进行了数值计算,结果表明该优化方法能够很好的满足过程约束和终端入轨条件,具有收敛速度快、对初值不敏感等优点,有一定的工程应用价值。     

活性填料控制的先驱体裂解制备陶瓷基复合材料研究进展

从先驱体转化法存在的问题出发,阐述了添加活性填料的意义和特点,介绍了活性填料控制的先驱体裂解过程中的尺寸变化、化学热力学和反应动力学以及制备陶瓷基复合材料的特点及国内外研究现状,并展望了未来发展。     

一种航空发动机多变量自抗扰解耦控制律设计

研究了航空发动机多变量解耦控制律设计问题。提出了一种用于航空发动机多回路控制的多变量自抗扰解耦控制算法:首先通过静态解耦算法实现多变量耦合系统的静态解耦,而后通过ADRC非线性扩张观测器的补偿控制实现各回路的动态解耦,最终实现复杂多变量耦合系统的解耦控制。以某涡扇发动机非线性部件级实时数学模型为被控对象,基于上述多变量自抗扰解耦控制算法设计了发动机中间状态以上多变量控制律。在全包线内,与基于增广LQR控制方法设计发动机闭环系统,进行了对比研究。数字仿真结果表明,前者使得发动机闭环系统具有更好的指令跟踪和多回路解耦能力。     

发动机燃烧室主动冷却管道的热-力耦合分析

为了准确高效地进行发动机冷却管道结构的热-力耦合数值分析,基于边界单元法提出一种冷却介质中结构对流换热过程的新型计算方法,计算过程中采用径向积分法将对流换热边界积分方程中的域积分转换为等效的边界积分,从而显著降低计算难度。采用改进后的边界单元法和有限元方法分别进行发动机燃烧室主动冷却管道处的热-力耦合分析,计算并获得了该处的温度场、位移场和应力场,发现了不同物理量随管道轴向的变化规律。通过比较基于两种不同数值方法的计算结果可以发现本文数值方法在显著降低计算模型复杂度的同时,取得了合理的计算结果。因此利用本文方法可以简便有效地进行发动机燃烧室主动冷却管道结构的热-力耦合分析。      

基于LMI的鲁棒H∞状态估计

给出了基于线性矩阵不等式（ＬＭＩ）鲁棒Ｈ∞状态估计器的设计过程,该方法克服了基于代数Ｒｉｃｃａｔｉ方程（ＡＲＥ）中处理不确定性的限制,整个设计过程完全通过求解三个ＬＭＩ很到,简化了设计过程,在惯性导航系统（ＩＮＳ）地面自对准中的应用表明,其于ＬＭＩ的鲁棒Ｌ∞状态估计器在系统具有不稳定性时,仍然能估计误差保持收敛,优于传统的性能状态估计。     

挠性悬臂板的变结构控制研究

针对航天器上太阳帆板这种悬臂外伸薄板结构的挠性附件 ,在存在建模参数不确定及外部扰动条件下所引起的振动 ,本文采用压电致动片作为执行器 ,将变结构控制应用于板的主动振动控制。通过仿真研究结果与应变律反馈控制比较 ,可知变结构控制具有较强的鲁棒性 ,同时控制器结构简单 ,易于实现