基于二进制标签的改进HSSE—tree算法

随着对航天器自主生存能力要求的提高,基于模型的故障诊断成为国内外的研究热点.计算全体极小碰集是基于模型的故障诊断中的关键步骤,以HSSE-tree算法为基础,结合二进制位标记,提出一种HSSE-tree的高效改进算法——Binary-label HSSE.改进算法采用二进制位标记来代替实际节点元素,并采用了有效的剪枝策略及节点扩展方式,避免了HSSE-tree算法中存在的节点个数及超集个数随着问题规模增大而产生的爆炸式增长的问题;此外,改进算法采用二进制位运算,避免了判断碰集及判断是否超集时的元素遍历,使算法的运行时间进一步减少.仿真结果表明,与HSSE-tree算法相比,改进算法的消耗时间及占用内存均有了大规模减少.这为航天器系统的故障诊断及实时诊断提供了理论依据和应用基础.     

Low-frequency Periodic Error Identification and Compensation for Star Tracker Attitude Measurement

The low-frequency periodic error of star tracker is one of the most critical problems for high-accuracy satellite attitude determination.In this paper an approach is proposed to identify and compensate the low-frequency periodic error for star tracker in attitude measurement.The analytical expression between the estimated gyro drift and the low-frequency periodic error of star tracker is derived firstly.And then the low-frequency periodic error,which can be expressed by Fourier series,is identified by the frequency spectrum of the estimated gyro drift according to the solution of the first step.Furthermore,the compensated model of the low-frequency periodic error is established based on the identified parameters to improve the attitude determination accuracy.Finally,promising simulated experimental results demonstrate the validity and effectiveness of the proposed method.The periodic error for attitude determination is eliminated basically and the estimation precision is improved greatly.     

Ka频段相控阵天线单元互耦的研究

由于互耦效应的影响,相控阵天线单元的辐射特性、阻抗特性都将发生变化,输入阻抗的变化会引起辐射单元与馈电网络的不匹配,造成信号功率的损失,严重时会导致相控阵天线扫描时出现"盲点"效应,使得天线不能正常工作。研制出含EBG栅格结构的相控阵天线阵面,测试结果表明采用该结构能够减小相控阵天线单元间的互耦。     

跨声速涡轮中两种叶片叶尖泄漏流的气动性能

采用数值模拟的方法,研究了跨声速涡轮叶栅中平面叶尖和双肋叶尖泄漏流的气动性能.平面叶尖比双肋叶尖的叶尖间隙内马赫数高,有反射激波结构;双肋叶尖的叶尖间隙内马赫数较低,没有形成明显的反射激波结构.平面叶尖和双肋叶尖的叶尖泄漏流质量流量分别为叶栅进口质量流量的3.87%和3.74%.平面叶尖的气动损失系数为0.079,双肋叶尖的气动损失系数为0.072.研究表明,双肋叶尖的气动性能要好于平面叶尖.      

电动舵机减速器传动特性误差分析与补偿研究

在电动舵机减速器的传动特性测试实验中,由于机械安装,轴承摩擦和电机驱动器非线性等原因造成的测量误差会折算到传动比测量误差中并降低精度。本文以减速器为研究对象,通过动力学方程建立了该系统的数学模型,通过理论分析将机械安装与轴承摩擦作为已知的系统误差,提出一种根据仿真结果获得补偿量,对实测数据进行预处理从而提高传动比测量精度的新方法。计算结果说明此方法能在一定程度上补偿电机驱动器非线性带来的测量误差。     

风力机翼型参数化方法

为满足开发高性能风力机专用翼型所需,提出一种风力机翼型参数化表达方法。首先,基于计算几何理论,开发了一类带形状可调参数的广义Bézier曲线,该曲线不仅保持了Bézier曲线良好的特性,而且具有维持控制多边形不变而实现形状可调的能力,能够更灵活地表达几何外形。然后,针对风力机翼型特点,将此类曲线进行可控性改进,发展了一种风力机翼型参数化表达方法。最后,通过表达常用翼型,以及同其他表达方法进行外形拟合对比,验证了新方法具备全面细致的表达能力,进一步以拟合DU93-W-210为标准算例,与其他方法进行气动特性的吻合表现对比,最终验证了新方法的有效性。     

涨圈密封挤压油膜阻尼器流场与阻尼特性

为研究两端密封型挤压油膜阻尼器流场与阻尼特性,建立了涨圈密封挤压油膜阻尼器三维非定常流场数值仿真模型。基于Fluent软件中的Mixture多相流模型和Schnerr-Sauer空化模型数值模拟得到动态油膜压力与气相体积分数的周向分布规律。将计算得到的阻尼器油膜压力与文献中的试验数据对比,结果显示:两者具有较高的一致性。由动态油膜力导出的平均等效阻尼系数与试验采用阻抗法识别的结果相比仅有0.6%的偏差,从而验证了该数值模型与预测方法的有效性。进一步的数值计算表明增大进动半径、进动频率、涨圈密封的狭缝宽度均会使挤压油膜阻尼器流场中的空化现象加重,同时等效阻尼系数降低。      

A preliminary study of the single crest phenomenon in total electron content (TEC) in the equatorial anomaly region around 120°E longitude between 1999 and 2012

The diurnal variations in total electron content (TEC) in the equatorial ionisation anomaly (EIA) region are not always represented by two crests on both sides of the magnetic equator. Sometimes, only an obvious single crest is evident at equatorial and low latitudes. In this paper, we focus on analysis of the morphological features of the single crest phenomenon in TEC around 120°E longitude during geomagnetic quiet days (Kp < 4₋). The variations in TEC are also compared with morphological parameters (foF2 and hmF2) derived from the International Reference Ionosphere extended to Plasmasphere (IRI–Plas) model. Our results show that the single crest phenomenon occurs mainly on days with extremely low solar activity, while the corresponding F2 layer critical frequency showed obvious asymmetry, or even only a single peak.     

Optimizing Control for Rotor Vibration with Magnetorheological Fluid Damper

The aim of this work is to analyze and design a control system for vibration reduction in a rotor system using a shear mode magnetorheological fluid （MRF） damper. A dynamic model of the MRF damper-rotor system was built and simulated in Matlab/Simulink to analyze the rotor vibration characteristics and the vibration reduction dfeet of the MRF damper. Based on the numerical simulation analysis, an optimizing control strategy using pat- tern search method was proposed and designed. The control system was constructed on a test rotor bench and ex- periment validations on the effectiveness of the proposed control strategy were conducted. Experimental results show that rotor vibration caused by unbalance can be well controlled whether in resonance region （70~） or in non- resonance region （30 ~）. An irregular vibration amplitude jump can be suppressed with the optimization strategy. Furthermore, it is found that the rapidity of transient response and efficiency of optimizing technique depend on the pattern search step. The presented strategies and control system can be extended to multi-span （more than two or three spans） rotor system. It provides a powerful technical support for the extension and application in target and control for shafting vibration.     

采用连续旋转检偏器的天空偏振光探测装置设计与实现

为了实现对运动目标与天空散射光的偏振分布模式进行快速、有效的探测,根据连续旋转检偏器光强度透射的数学模型,利用光电传感器的积分特性,设计并构建了采用连续旋转检偏器的偏振成像探测装置。测试结果表明,该装置对偏振光的角度的测量精度优于0.069°（3σ）,偏振度的测量精度优于0.12%（3σ）。一幅偏振图像的探测时间达到0.7s。在偏振度低于4%的情况下,仍可以探测到有规律的偏振分布模式,其抵抗恶劣天气的性能优于现有的偏振导航探测装置。