脉冲多普勒体制导引头功能模型数学建模…

空空导弹的系统建模是导弹研制的基础。本文以脉冲多普勒雷达导引头为例,建立一种脉冲多普勒体制的导弹导引头功能模型,建立了遮挡效应数学模型和失调角测量数学模型的设计过程,并根据PD雷达导引头的制导方式,对典型场景下导弹攻击目标的全过程进行了动态仿真。仿真验证了模型的有效性。     

海上舰船目标的宽带雷达散射特征信号仿真

提出一种将目标高频电磁（EM）散射计算多径回波模型与不同海况条件下粗糙海面前向复反射系数模型相结合的方法,对海上舰船目标宽带雷达回波进行仿真和分析。简要分析了目标-海面相互作用的多径回波模型,给出了目标体的电磁散射计算方法,研究了不同海况条件下海面前向复反射系数随频率和擦地角的变化特性,并通过仿真分析了海面对舰船目标雷达回波的影响。对比分析舰船目标体直接散射及在不同海况条件下考虑多径效应时的雷达散射截面（RCS）变化特性,并在不同海况条件下对目标进行二维逆合成孔径雷达（ISAR）成像仿真,验证了本文方法的有效性。     

射手模型优化与辨识及其对图像制导的影响

基于数据链通信的人在回路制导模式额外引入了射手动力学而且存在图像信号延时,含有射手动力学的控制回路会对目标在视场（LOS）中的误差角进行跟踪补偿,从而提升图像制导弹药的制导控制性能。为探究射手动力学和图像信号延时对人在回路制导性能的影响,基于真实的图像导引头模型及参数,设计校正网络以满足导引头稳定回路的性能需求;引入两类射手模型,针对射手模型2,优化模型结构并通过贴近真实环境的辨识实验得到动力学参数,弥补了现有建模的不足。基于射手对不同图像信号延时的适应性,对比研究了两类射手模型与不同图像信号延时对导引头控制系统稳定性、快速性和人在回路比例导引制导精度的影响。仿真结果表明：图像信号延时越长,导引头跟踪速度越低、误差角越大,制导系统的收敛时间越长;优化后的射手模型2及其参数辨识更准确地描述了射手的操作行为,对制导系统的影响较低且满足系统性能要求。     

基于阵列天线的一种GPS多径抑制方法

为了抑制多径效应对GPS的严重影响,在分析了多径效应对伪码跟踪环路影响的基础上,提出了一种基于空间平滑的改进稳健波束形成算法来抑制GPS多径效应。以直线阵为基础,采用前后向空间平滑算法对阵列接收信号进行预处理,针对各种失配,采用改进的稳健波束形成算法进行处理。该方法既可以有效地抑制GPS多径效应,又可以有效地改善伪码跟踪环路的跟踪精度。仿真实验结果验证了所提方法的正确性和有效性,具有较高的工程实践价值。     

考虑扰动及控制饱和的多约束末制导方法

在末制导阶段,飞行器受到建模误差、风、目标运动等多种扰动的影响,且导引头视场、攻角及落角受到约束。为此,提出一种多约束及扰动下的末制导方法。将制导问题转化为存在扰动与控制饱和的系统的镇定问题。设计低增益状态反馈律镇定系统,利用线性扩张状态观测器观测系统中的扰动并在反馈律中对其进行补偿。以此为基础推导得到末制导律。基于Lambert W函数研究制导律参数对视线角收敛的影响,并提出制导律参数的自适应整定方法。通过在线调整制导律参数,保证全部约束得到满足。在多种扰动下,通过数值仿真验证提出的制导方法。仿真结果表明,制导律满足所有约束且获得的制导精度较高。     

某型空空导弹红外探测系统仿真计算与分析

空空导弹红外探测系统决定着导弹能否探测到目标,在整个导弹系统中具有非常重要的作用,在导弹测试与修理过程中也是必检项目。本文对某型导弹测试过程中导引头输出音响信号原理进行深入分析,充分考虑到目标模拟器、导引头光学系统、锑化铟探测器及前置放大器等因素,建立了红外探测系统输出电压的数学模型,并将该模型与Multisim软件结合起来进行仿真计算。通过与实测值的对比,证明该模型有较好的正确性,对该型导弹导引头原理分析和修理有一定指导作用。     

雷达低空目标俯仰角跟踪的C2算法研究

在单脉冲测角体制下,由于多径回波信号的干扰,极大地降低了雷达低空目标仰俯角跟踪精度,甚至丢失目标。通过对多路径反射环境模型分析,得出了岸、海基单脉冲雷达低空目标跟踪时仰俯角测量误差的产生原因,提出将传统的多目标分辨算法(C2算法)应用于低角多径环境下目标俯仰角的跟踪测量,并在不同多径反射环境下对不同高度、不同飞行速度和飞行方向的目标进行了仿真,得到良好的仿真结果,表明该算法可较大地提高俯仰角跟踪测量精度。通过对仿真结果的分析,验证了该算法在低空目标跟踪中的有效性和可行性。     

跳频体制雷达导引头干扰仿真研究

针对距离拖引、速度拖引以及拖曳式无源诱饵对跳频体制雷达导引头的影响进行了仿真研究,具体分析了不同干扰对导引头产生的影响,并对部分干扰提出了相应的抗干扰策略.     

无导引头也无惯导导弹的协同制导

为了在不依赖导弹间实时通信与导弹绝对位置信息的情况下实现无导引头也无惯导导弹的"发射后不管",考虑为无导引头也无惯导导弹安装两个捷联探测器,从而可对有导引头导弹上的两个特定目标点进行探测。在此基础上,针对静止点目标分别采用一般的负反馈控制方法以及有限时间收敛原理设计了2种协同末制导律,并针对静止面目标采用动态逆控制设计了1种协同末制导律。上述协同制导律均可在有导引头导弹命中目标前实现无导引头也无惯导导弹的速度方向指向其攻击目标,而此后无导引头也无惯导导弹只需要作直线运动即可命中其攻击目标。仿真结果验证了上述协同制导律的有效性以及优势。     

基于IMM理论的大型舰船被动定位算法研究

针对相控阵导引头跟踪航母等大型舰船目标的要求,为了给雷达成像进行运动补偿、给目标识别提供更多的先验信息,必须对目标运动参数进行准确的估计,但是常规被动定位算法通常采用单一目标运动模型,难以适应大型军舰运动规律的多样化,导致模型不匹配,使得误差较大,难以对目标参数进行准确估计,为解决上述问题,提出了一种基于交互式多模型(IMM)理论的大型舰船被动定位方法,使用不同的模型来匹配舰船不同的运动状态。仿真结果表明,提出的方法与常规的被动定位算法相比,定位精度明显提高,且易于工程实现。     

The effect of inlet conditions on the flow and heat transfer in multiple rotating cavity with axial throughflow

This paper discusses experimental results from two different build configurations of a heated multiple rotating cavity test rig.Measurements of heat transfer from the discs and tangential velocities are presented.The test rig is a 70% full scale version of a high pressure compressor stack of an axial gas turbine engine.Of particular interest are the internal cylindrical cavities formed by adjacent discs and the interaction of these with a central axial throughflow of cooling air.Tests were carried out for a range of non-dimensional parameters representative of high pressure compressor internal air system flows(Re up to 5×106 and Rez up to 2×105).Two different builds have been tested.The most significant difference between these two build configurations is the size of the annular gap between the(non-rotating) drive shaft and the bores of the discs.The heat transfer data were obtained from thermocouple measurements of surface temperature and a conduction solution method.The velocity measurements were made using a two component,LDA system.The heat transfer results from the discs show differences between the two builds.This is attributed to the wider annular gap allowing more of the throughflow to penetrate into the cavity.There are also significant differences between the radial distributions of tangential velocity in the two builds of the test rig.For the narrow annular gap,there is an increase of non-dimensional tangential velocity V/Ωr with radial location to solid body rotation V/Ωr=1.For the wider annular gap,the non-dimensional velocities show a decrease with radial location to solid body rotation.      

Research on Auto-detection for Remainder Particles of Aerospace Relay Based on Wavelet Analysis

Aerospace relay is one kind of electronic components which is used widely in national defense system and aerospace system. The existence of remainder particles induces the reliability declining, which has become a severe problem in the development of aerospace relay. Traditional particle impact noise detection (PIND) method for remainder detection is ineffective for small particles, due to its low precision and involvement of subjective factors. An auto-detection method for PIND output signals is proposed in this paper, which is based on direct wavelet de-noising (DWD), cross-correlation analysis (CCA) and homo-filtering (HF), the method enhances the affectiv-ity of PIND test about the small particles. In the end, some practical PIND output signals are analysed, and the validity of this new method is proved.     

Preparation of Highly Dispersed Antimony-doped Tin Oxide Nano-powder via Ion-exchange Hydrolysis of SnCl4 and SbCl3 and Azeotropic Drying

Antimony-doped tin hydroxide colloid precipitates have been synthesized by hydrolysis of SnCl4 and SbCl3 using: (1) an ion-exchange hydrolysis to remove chlorine ions, and (2) isoamyl acetate as an azeotropic solvent to obviate water. The obtained dried powder is of high dispersivity without any need for further grinding. The size and dispersivity of the final particles are investigated with the aid of TG-DTA, BET, XRD and TEM. After having calcined, the antimony-doped tin oxide nanopowder possesses a tetragonal rutile structure with high dispersivity, uniform particles and low hard agglomeration.     

Effects of Mo on the Microstructure and Hydrogen Sorption Properties of Ti-Mo Getters

The effects of Mo on the microstructure evolution, porosity and hydrogen sorption properties of Ti-Mo getters are investigated in this work. The results show that the addition of Mo prolongs the densification process of Ti-Mo getters and results in a significant amount of sintered pores. With the Mo content increasing, the porosity of getters firstly increases reaching the maximum value as it at- tains about 7.5wt.%, and then drops. At the room temperature, the hydrogen sorption property of getters increases progressively with the Mo content increasing, but the tendency is not very clear before its content lies below 2.5wt.%. When the Mo content achieves about 7.5wt.%, the hydrogen sorption property proves to be the best. The discussion is made about the above mentioned phenomena inclusive of hydrogen sorption properties of getters under different activation conditions (from 500-750 ℃).     

超声速燃烧数值模拟中的湍流与化学反应相互作用模型

高精度数值模拟有助于理解超声速湍流燃烧中湍流与化学反应的相互作用,可为发动机燃烧室等工程应用设计提供可靠的预测模型。除直接数值模拟外,目前在湍流燃烧应用中使用的大涡模拟和雷诺平均Navier-Stokes模拟均需要借助模型模化发生在湍流小尺度上的流动与化学反应过程对湍流大尺度运动的影响。现有的湍流与化学反应相互作用模型大致可分为:火焰面类模型和概率密度函数类模型,2类模型在不同的应用中各自具有优势和局限性。此外,现有模型大都基于低马赫数燃烧,而超声速燃烧中通常会伴随快速混合、局部熄火和再着火以及激波等复杂过程,这为发展其中的湍流与化学反应相互作用模型提出了更多的挑战。     

适于低轨卫星IP网络的单核共享树组播算法(英文)

为了解决低轨卫星IP网络中现有典型源组播算法的信道资源浪费问题,本文提出了一套单核共享树组播算法,即核心群合并共享树(CCST)和加权核心群合并共享树(w-CCST)算法。CCST 算法包括动态近似中心(DAC)选核方法和核心群合并组播路径构建方法。DAC方法专为周期、规律运动的低轨卫星网络提出,不需要复杂的星上计算。在核心群合并方法中,以核节点作为初始核心群,通过核心群和剩余组成员的最短路径方法逐步扩展直至整棵组播树构建完成,从而使得组播树的树代价最小,大大提高了网络的带宽利用率和组播传输效率。w-CCST 算法中所提出的加权因子可以调整树代价和端到端传播时延之间的折衷程度,因此,可以通过调整加权因子来适度增大树代价、降低端到端传播时延以支持某些端到端时延要求苛刻的实时组播业务。最后,与低轨卫星 IP 网络中典型算法进行了性能比较,仿真结果说明,CCST 算法的平均树代价比其它算法显著降低,w-CCST 算法的平均端到端传播时延小于 CCST 算法。     

Jet Vectoring Control Using a Novel Synthetic Jet Actuator

A primary air jet vectoring control system with a novel synthetic jet actuator (SJA) is presented and simulated numerically. The results show that, in comparison with an existing traditional synthetic jet actuator, which is able to perform the duty of either “push” or “pull”, one novel synthetic jet actuator can fulfill both “push” and “pull” functions to vector the primary jet by shifting a slide block inside it. Therefore, because the new actuator possesses greater efficiency, it has potentiality to replace the existing one in various appli- cations, such as thrust vectoring and the reduction of thermal signature. Moreover, as the novel actuator can fulfill those functions that the existing one can not, it may well be expected to popularize it into more flow control systems.     

Nonlinear Adaptive Slewing Motion Control of Spacecraft Truss Driven by Synchronous V-gimbaled CMG Precession

The slewing motion control of a truss arm driven by a V-gimbaled control-moment-gyro (CMG) is a nonlinear control problem. The V-gimbaled CMG consists of a pair of gyros that must precess synchronously. The moment of inertia of the system, the angular momentum of the gyros and the external disturbances are not exactly known. With the help of feedback linearization and recursive Lyapunov design method, an adaptive nonlinear controller is designed to deal with the unknown items. Performance of the proposed controller is verified by simulation.     

An SOR Implicit Time-accurate Scheme in Calculating Unsteady Flows

A new time-accurate marching scheme for unsteady flow calculations is proposed in the present work. This method is the combination of classical Successive Over-Relaxation (SOR) iteration method and Jacobian matrix diagonally dominant splitting method of LUSGS. One advantage of this algorithm is the second-order accuracy because of no factorization error. Another advantage is the low computational cost because the Jacobian matrices and fluxes are only calculated once in each physical time step. And, the SOR algorithm has better convergence property than Gauss-Seidel. To investigate its accuracy and convergency, several unsteady flow computa- tional tests are carried out by using the proposed SOR algorithm. Roe’s FDS scheme is used to discritize the inviscid flux terms. Un- steady computational results of SOR are compared with the experiment results and those of Gauss-Seidel. Results reveal that the numerical results agree well with the experimental data and the second-order accuracy can be obtained as the Gauss-Seidel for unsteady flow computations. The impact of SOR factor is investigated for unsteady computations by using different SOR factors in this algorithm to simulate each computational test. Different numbers of inner iterations are needed to converge to the same criterion for different SOR factors and optimal choice of SOR factor can improve the computational efficiency greatly.