Identification method for helicopter flight dynamics modeling with rotor degrees of freedom

A comprehensive method based on system identification theory for helicopter flight dynamics modeling with rotor degrees of freedom is developed. A fully parameterized rotor flapping equation for identification purpose is derived without using any theoretical model, so the confidence of the identified model is increased, and then the 6 degrees of freedom rigid body model is extended to 9 degrees of freedom high-order model. Bode sensitivity function is derived to increase the accuracy of frequency spectra calculation which influences the accuracy of model parameter identification. Then a frequency domain identification algorithm is established. Acceleration technique is developed furthermore to increase calculation efficiency, and the total identification time is reduced by more than 50% using this technique. A comprehensive two-step method is established for helicopter high-order flight dynamics model identification which increases the numerical stability of model identification compared with single step algorithm. Application of the developed method to identify the flight dynamics model of BO 105 helicopter based on flight test data is implemented. A comparative study between the high-order model and rigid body model is performed at last. The results show that the developed method can be used for helicopter high-order flight dynamics model identification with high accuracy as well as efficiency, and the advantage of identified high-order model is very obvious compared with low-order model.     

惯组中光纤陀螺温度漂移的二维插值建模研究

光纤陀螺对温度较为敏感,输出受温度及温度变化率影响严重,在实际工作中需要对温度漂移误差进行建模补偿。传统多项式拟合方法如最小二乘法,无法很好地满足精度要求。因此,首先对光纤陀螺工作原理与温度漂移误差产生原理进行分析,得出光纤陀螺温度漂移误差特性。利用传统多项式模型对不同温度下启动的光纤陀螺进行建模补偿,得到补偿后的精度并不理想。利用新的二维插值模型对上述试验重新进行建模补偿,结果表明二维插值模型明显优于多项式模型,光纤陀螺的零偏稳定性由补偿前的0.0153(°)/h提高到0.0051(°)/h,有利于工程上应用。     

大功率舰船燃气轮机压气机增容模化设计研究

某重点项目的船用燃气轮机领域提出了更高等级功率燃气轮机的要求。为了在研制周期内快速设计一型压气机,以现有机型为母型机进行模化设计,在母型机特性图上合理选择模化点,确定模化比,得到增容后模化机的叶片和几何通流结构,划分网格时,充分考虑叶顶间隙、倒角、引气孔、梳齿密封等,以更接近于工程实际情况,对模化机进行全三维数值模拟计算,结果表明,模化机设计点性能指标达到要求,非设计工况喘振裕度基本与母型机相同,模化后叶顶相对间隙的降低会带来阻塞点流量的升高、失速点流量的降低,导致低转速下喘振裕度的升高和高转速下喘振裕度的降低。总体来说,模化增容设计继承了母型机优良的气动性能,为快速、高效研发新机型提供宝贵经验。     

半球谐振陀螺全角模式控制技术研究

介绍了半球谐振陀螺全角模式的工作机理及其技术特点。对全角模式下振型的控制进行了理论分析,采用乘法相干解调对陀螺振型参数进行提取,并采用参数激励方法对谐振子进行驱动和控制。设计了数字电路进行实验,结果表明该全角模式控制技术实现了半球谐振陀螺的角速率积分功能,能够0°～360°全角度敏感输出,测得的角速度测量值超过300(°)/s,角度测量线性度优于10~(-4),与传统的力平衡模式相比,半球谐振陀螺的动态特性得到大幅提升。     

Testing the three-dimensional IRI-SIRMUP-P mapping of the ionosphere for disturbed periods

This paper describes the three-dimensional (3-D) electron density mapping of the ionosphere given as output by the assimilative IRI-SIRMUP-P (ISP) model for three different geomagnetic storms. Results of the 3-D model are shown by comparing the electron density profiles given by the model with the ones measured at two testing ionospheric stations: Roquetes (40.8°N, 0.5°E), Spain, and San Vito (40.6°N, 17.8°E), Italy. The reference ionospheric stations from which the autoscaled foF2 and M(3000)F2 data as well as the real-time vertical electron density profiles are assimilated by the ISP model are those of El Arenosillo (37.1°N, 353.3°E), Spain, Rome (41.8°N, 12.5°E), and Gibilmanna (37.9°N, 14.0°E), Italy. Overall, the representation of the ionosphere made by the ISP model is better than the climatological representation made by only the IRI-URSI and the IRI-CCIR models. However, there are few cases for which the assimilation of the autoscaled data from the reference stations causes either a strong underestimation or a strong overestimation of the real conditions of the ionosphere, which is in these cases better represented by only the IRI-URSI model. This ISP misrepresentation is mainly due to the fact that the reference ionospheric stations covering the region mapped by the model turn out to be few, especially for disturbed periods when the ionosphere is very variable both in time and in space and hence a larger number of stations would be required. The inclusion of new additional reference ionospheric stations could surely smooth out this concern.     

New Cutting Force Modeling Approach for Flat End Mill

A new mechanistic cutting force model for flat end milling using the instantaneous cutting force coefficients is proposed. An in-depth analysis shows that the total cutting forces can be separated into two terms: a nominal component independent of the runout and a perturbation component induced by the runout. The instantaneous value of the nominal component is used to calibrate the cutting force coefficients. With the help of the perturbation component and the cutting force coefficients obtained above, the cutter runout is identified. Based on simulation and experimental results, the validity of the identification approach is demonstrated. The advantage of the proposed method lies in that the calibration performed with data of one cutting test under a specific regime can be applied for a great range of cutting conditions.     

A spanwise loss model for axial compressor stator based on machine learning

In the early stage of aircraft engine design, the through-flow method is an important tool for designers. The accuracy of the through-flow method depends heavily on the accuracy of the loss model. However, most existing models cannot(or cannot well) provide the spanwise loss distribution. To construct an effective spanwise loss model, both turbomachinery knowledge and machine learning skills were used in this paper. A large number of numerical simulations were carried out to build a database con...     

双星预警系统弹道参数估计及一些问题分析

主要讨论由2颗地球同步轨道卫星组成的卫星预警系统(简称双星预警系统)中弹道导弹参数的估计问题。阐述了主动段运动的建模问题和弹道数据处理方法,考虑到微分求速的重要性,采用了带光滑约束的样条拟合方法。结合预警系统对弹道导弹预警的具体情况,分别讨论了预警系统下的发射原点估计、射向估计、关机时刻估计、关机点弹道参数估计、落点估计等问题。还讨论了系统中存在的两个问题的分析与解决。模型及分析方法均经过理论和仿真的验证,可应用于双星预警系统下的实际预警的研究。     

基于雷达对抗试验等效推算的密集压制干扰研究方法

面向雷达干扰研究的现实需求及作战目标雷达难以获取的现实困难,针对密集假目标压制干扰这一典型干扰样式,研究了密集假目标压制干扰效果替代等效推算的基本原理,建立了数学推算模型和仿真模型,构建了作战目标雷达的仿真系统,并基于试验数据表明了推算模型和仿真模型的正确性,为研究密集假目标压制干扰对作战目标雷达的干扰效果提供了高效、可靠的分析工具。     

超宽带无线电引信接收机时域建模与仿真

为得到弹目交会过程中超宽带无线电引信接收机的时域输出信号,实现高速交会条件下引信接收机的性能优化,推导了取样积分微分电路的时域数学模型,提出了一种基于无载波信号时域多普勒效应的接收机输出信号时域仿真方法.弹目接近速度对接收机输出信号的影响研究表明,输出信号频率与弹目接近速度成正比;信号幅度与弹目接近速度关系曲线存在速度驻点.选择合理的积分、微分电容可设置恰当的速度驻点,提高引信的抗干扰性能.