实测载荷谱数据处理系统

简要介绍了实测载荷谱数据处理系统，较深入地论述了实测载荷谱数据处理的几个重要方面，给出了该系统处理直升机旋翼系统动部件实测载荷谱的实例，通过大子样二维疲劳２载荷母体分布参数估计及假设检验，发现载荷幅值服从半正态分布，载荷均值服从三参数Ｗｅｉｂｕｌｌ分布。     

Hexapod多自由度微激励系统的振动时域波形控制

摘要： Hexapod多自由度微激励系统常用于航天器有效载荷在轨微振动环境的模拟，但采用现有控制方法无法精确稳定跟踪低频正弦加速度，这是由于系统耦合度高、非线性在低频段较强，被控对象相位滞后过大造成的.针对此问题，基于传统离线迭代控制方法，提出一种复合超前校正、多倍频陷波滤波器的改进离线迭代控制方法.其中，离线迭代进行补偿控制，超前校正进一步补偿系统相位，多倍频陷波滤波器去除非线性干扰.跟踪低频定频正弦加速度的实验结果表明，对比传统离线迭代控制方法，改进方法收敛快、控制精度高；对比现有自适应正弦振动控制方法，改进方法将符合精度要求的加速度控制频带下限由14.5 Hz扩宽至8 Hz.实验结果验证了所提方法的有效性.     

Time-series analysis of GPS measurements for long-span bridge movements using wavelet and model prediction techniques

This study aims at assessing the safety behavior of the Incheon long-span bridge using high rate (10?Hz) geodetic monitoring global positioning system (GPS). The time series of wavelet spectrum analysis is utilized to assess the dynamic behavior of the bridge. The coefficients and model errors of the time series autoregressive-moving average (ARMA) model are used to evaluate the movement performances of the bridge. The results show that: (i) the accuracy of GPS measurements to extract the dynamic behavior of the bridge is 97.27% when compared with the design results. (ii) the behavior of the bridge is within the safety limits of the bridge design with minimum observed changes for the historical GPS measurements in time and frequency domains, the mean deflection of bridge deck is 8.26?mm and frequency changes of bridge is 0.004?Hz compared with the design results. (iii) the time series analysis of the wavelet spectrum and ARMA model coefficients can be used to detect the significant frequency changes and study the rigidity of the bridge performance, respectively; and the both methods are found to be suitable techniques to estimate the performance changes of the GPS measurements in the time and frequency domains during the monitoring time period.     

一次民机飞行中甚高频通信不稳定的排故

针对某型号民用飞机甚高频通信系统在飞行中出现断续故障的情况，对系统的架构进行描述，分析了故障产生的机理，提出了排故思路，记述了排故过程，并总结了甚高频通信系统的设计要点和工艺要点。     

Abnormal changes of dynamic derivatives at low reduced frequencies

A number of studies have found that abnormal changes of dynamic derivatives occurred at very low reduced frequencies, but its inducement mechanism is not very clear. This paper has researched the abnormal changes and analyzed the influence on some parameters by solving the unsteady flow around forced oscillation airfoils based on Navier-Stokes equations. Results indicate that when the reduced frequency approaches to zero, the dynamic derivatives obtained by the numerical method will diverge. We have also proven it in theory that this phenomenon is not physical but completely caused by numerical singularity. Furthermore, the abnormal phenomenon can be effectively mitigated by using the time spectral method to solve the aerodynamic forces and the integral method to obtain the dynamic derivatives. When the reduced frequency is in the range of 0.001–0.01, the dynamic derivative maintains nearly unchanged for the whole speed region. This study can provide a reference for the reasonable choice of the reduced frequency in calculations and experiments of dynamic derivatives.     

DME脉冲调制信号波形参数对空间频谱占用的影响分析

航空测距器DME的开发、调试和性能验证都要用到高斯双脉冲调制格式的DME信号。由于专用的DME信号模拟器技术复杂、价格昂贵,人们常用具有快沿双脉冲调制功能的模拟信号源替代。本文以航空测距器DME信号要求为依据,初步分析了这种替代可能存在的问题,并通过实验对不同边沿条件下高斯双脉冲、矩形双脉冲调制信号的功率频谱占用情况进行了验证。     

Ionospheric F2-Layer critical frequency retrieved from COSMIC radio occultation: A statistical comparison with measurements from a meridional ionosonde chain over Southeast Asia

In this paper, we compared the F2-Layer critical frequency (foF2) derived from FORMOSAT-3/COSMIC radio occultation (RO) and ionosondes at Chiang Mai, Chumphon and Kototabang during the years 2008–2015 to evaluate the performance of COSMIC RO over Southeast Asia region. The results show that the time development of foF2 values derived from COSMIC RO generally agrees well with those from ionosonde measurements. However, the differences between the foF2 derived from COSMIC RO and that derived from ionosonde observations display latitudinal dependence. COSMIC RO tends to underestimate foF2 at Chiang Mai and Kototabang, which is near to the north EIA crest and the south one, respectively, while a little overestimate foF2 at Chumphon, which is close to the geomagnetic equator. COSMIC RO agrees best with ionosonde at Chumphon and worst at Chiang Mai. At each ionosonde station, the quality of COSMIC RO data degrades with the increase of solar activity. In addition, at the station Chiang Mai and Kototabang, COSMIC RO performs better in summer than in equinox and winter. Furthermore, the differences in foF2 derived from COSMIC RO and that from ionosonde measurements vary with local time, i.e., the differences in foF2 are generally smaller at night and larger in noontime when equatorial ionization anomaly (EIA) is well developed.     

采用霍尔传感器的旋翼频率采集设计

为达到对旋翼飞机的控制,需要对旋翼转速进行采集.霍尔转速传感器以其高可靠性等优点常被用来测量转速.介绍了一种使用霍尔传感器进行旋翼转速采集系统,包括硬件构架,逻辑采集单元和软件设计,并给出了优化策略;通过试验数据分析,采集精度达到了预期.     

无人机高速DS/FH混合扩频通信系统关键模块设计

针对UAV(Unmanned Aerial Vehicle,无人机)测控链路高抗干扰需求,给出了实现跳频速率20 000次/s的扩跳混合无人机测控数据链系统实现方案.系统采用跳频频率并行捕获模式.跳频源设计采用直接频率合成、DDS(Direct Digital Synthesis,直接数字频率合成)和PLL (Phase-Locked Loop,锁相环)相结合的混合频率合成技术.利用相位响应滤波器,通过正交调制技术完成MSK(Minimum Shift Keying,最小频移键控)、GMSK (GaussianMinimum Shift Keying,高斯最小频移键控)调制.通过推导得出2 bit差分解调输出与载波频率选择有关,且为四分之数据率的整数倍关系.然后通过实例分析给出了跳频频率间隔选取方法,即跳频间隔应当将临近跳频的主瓣分开,同时跳频载波频率应当设在其他跳频频谱的零点处.最后总结了高速扩跳频系统参数设计一般步骤.     

RFID技术在航空领域的应用研究

射频识别(RFID)技术现已广泛用于物流、金融、零售等各个行业.航空领域的RFID应用起步较晚,通过对RFID技术在飞机制造商、原始设备生产厂家(OEM)、航空公司的一些典型的应用案例的分析,提出RFID技术应用于航空领域所面临的挑战及必要性,为其未来航空业自动识别技术的发展指明了方向.