适应长期在轨的低温推进剂集成管理模块仿真研究

低温推进剂集成管理技术是面向未来火箭上面级长期在轨、多次启动任务的新技术手段。以上面级在轨滑行5天的奔月任务为背景,采用AMESim仿真平台搭建低温推进剂集成管理模块系统模型,开展滑行段工作过程仿真。仿真结果表明低温推进剂集成管理模块内组件工作占空比作为组件重要工作特征及工作参数,随姿控、电池充电等低温推进剂集成管理模块工作阶段变化而变化。     

微重力下低温贮箱内推进剂相变仿真模型研究

低温推进剂具有沸点低、易汽化的特点,相变是低温推进剂长时间在轨蒸发量控制问题中需要考虑的首要影响因素。相变模型对低温推进剂蒸发仿真起到重要作用,构建合理的相变模型成为低温流体蒸发量仿真重要的研究方向。基于4种相变理论,采用FLUENT软件二次开发的方法,建立基于相平衡和非平衡理论的4种相变模型,开展微重力下液氢推进剂蒸发的数值模拟,并与国外探空火箭试验进行比较和验证。研究结果表明：比较4种相变模型对贮箱内压力升高速率预示的准确性,得出了适用于微重力下低温推进剂仿真的相变模型。     

低温贮箱热力学排气系统建模及仿真分析

针对低温推进剂在轨贮箱蒸发量控制问题,建立低温贮箱热力学排气系统自增压和压力控制仿真模型,综合考虑贮箱封头气枕壁面模型、贮箱柱段气枕壁面模型、贮箱液体壁面模型、液相模型、环境模型、气液界面模型、气枕模型以及贮箱壁面液相-气枕壁面液膜模型等仿真模型,模型包含固体节点、气枕节点以及液体推进剂节点,通过对热力学排气系统J-T排气阀、换热器以及排气系统的耦合计算可得到相应的仿真数据。通过对NASA MHTB试验平台50%充灌率的试验进行仿真计算,结果表明,整个热力学排气系统运行过程的仿真数据与美国MHTB试验平台数据相吻合,可为低温推进剂在轨贮存仿真计算提供支撑。     

低冰点推进剂对液体火箭发动机性能影响研究

针对低冰点推进剂在液体火箭发动机性能研究中的重要性,对使用MON25/DT3组合的低冰点推进剂液体火箭发动机的启动过程及稳态过程进行研究.建立了发动机系统的数学模型,采用Matlab/Simulink构造系统的仿真模型.根据仿真结果比较和分析了不同初温的推进剂对燃烧室压强、发动机比冲和推力等各方面性能的影响,得出了这三个参量与推进剂初温的拟合关系式.     

基于粘聚区模型的推进剂开裂数值仿真

为了研究复合固体推进剂裂纹开裂过程,利用粘聚区模型理论构建了复合固体推进剂断裂过程的物理和数学模型;推导了粘聚区单元的有限元离散格式;结合ABAQUS二次开发技术对裂纹扩展过程进行了数值仿真,获得了HTPB推进剂Ⅰ-Ⅱ型裂纹扩展过程中的裂纹扩展路径和裂尖应力变化情况.分析了粘聚区本构参数对仿真结果的影响,确定了其取值范围.将仿真和实验对比,结果表明所建立的数值仿真方法可以较为准确地模拟复合固体推进剂裂尖的损伤应力场,以及预测裂纹扩展路径;粘聚区模型可以为固体推进剂装药完整性和安全性分析提供可靠的分析计算方法.     

基于AMESim的姿控发动机推进剂供应管路优化设计

根据模块化思想,建立了液体姿控火箭发动机推进剂供应管路的AMESim模型,仿真计算了推进剂供应管路优化前后姿控发动机工作时的水击压力.仿真结果表明:在推进剂供应管路上增加的体积容腔能够有效降低管路中的水击压力.通过仿真水击数据和热试车数据对比表明,仿真模型较好地描述了管路水击过程,能对后续液体姿控火箭发动机管路结构优化设计提供借鉴意义.     

HTPB/IPDI复合固体推进剂细观界面率相关参数的反演识别研究

为研究HTPB/IPDI(hydroxyl-terminated polybutadiene/isophorone diisocyanate)复合固体推进剂细观界面性能随加载速率的变化规律,基于分子动力学算法生成了HTPB/IPDI复合固体推进剂的细观颗粒填充模型。颗粒与基体间粘接作用通过结合粘弹性标准机械单元及指数型率无关内聚本构所构建出的率相关内聚力模型模拟。通过HTPB/IPDI基体胶片的应力松弛试验得到细观模型中基体材料的松弛参数。基于模型对HTPB/IPDI推进剂在不同加载速率下(0.1,5,20 mm·min~(-1))的宏观力学响应进行仿真计算。利用数值仿真结果与HTPB/IPDI推进剂单轴拉伸试验结果曲线,通过Hooke-Jeeves优化算法对率相关内聚力模型参数进行反演分析,得到了优化后的界面参数数值。利用所建立的模型对50,100 mm·min~(-1)加载速率下的HTPB/IPDI复合固体推进剂材料的宏观力学行为进行预测。结果显示,预测结果与实际试验结果较为一致。     

某推进剂瞬态热传导数值模拟

根据某推进剂的使用环境及其所在系统对推进剂的特殊要求,利用ANSYS/LS-DYNA程序瞬态热传导算法,使用能够反映工作过程和试验过程的工程模型,通过建立瞬态热传导有限元模型,采用不同时刻对该推进剂进行了数值分析,并对比了该试验过程,证明该方法完全符合工程实际情况。     

近空间飞行器推进系统研究

根据给定的飞行参数指标,建立了近空间飞行器的设计仿真模型和弹道模型.以余氧系数为变量参数,对其使用的双组元液体推进剂进行了分析和选择,并对泵压式和挤压式两种推进系统方案进行了比较研究.研究结果表明,选择过氧化氢/煤油作为组合推进剂比较合理,泵压式推进系统方案要优于挤压式推进系统方案.研究结果可为其它同类近空间飞行器的推进系统研究提供借鉴和依据.     

固体推进剂的仿真技术

推进剂装药形状的燃烧面积值是固体火箭发动机燃烧性能设计中的重要参数。但是推进剂装药形状复杂 ,用几何学方法很难迅速精确计算其燃烧面积值。因此国外研究了利用“颗粒跟踪法”,即利用软件逐次计算因燃烧而变化的推进剂燃烧面积仿真系统 ,并探讨了其计算值的正确性。证明利用该系统计算的燃烧面积值与利用几何学方法计算值之差在1%以内。     

Stability of the Third Generation Intensifier under Illumination

The stability under illumination of transmission-mode GaAs photocathode sealed in the third generation intensifier is investigated by use of spectral response testing instruments. The variations of spectral response with the illumination times under weak and intense illumination are compared. The variations of photoemission performance parameters are also characterized. The results show that during initial several weak illuminations photocathode behaves no evident decay and a maximum sensitivity is achieved, while under intense illumination the sensitivity of photocathode begin to decrease largely at the first illumination. The calculated performance parameters show that the variation of surface escape probability with illumination times is a direct cause of instability of photocathode. It is also found that under intense illumination peak wavelength is moved towards short-wave and peak response is decreased, which shows that the ability of long-wave response of photocathode is decreased.     

Passive Acoustic Radar for Detecting Supersonic Cruise Missile

A Passive Acoustic Radar is presented as a necessary complement to electromagnetic wave radar, which will be expected to be an effective means for detecting cruise missiles. Acoustic characteristics of supersonic flying projectiles with diverse shapes are expounded via experiment. It is pointed out that simulation experiment could be implemented using bullet or shell instead of cruise missile. Based on theoretical analysis and experiment, the ““acoustic fingerprint““ character of cruise missile is illustrated to identify it in a strong noise environment. After establishing a locating mathematical model, the technique of acoustic embattling is utilized to resolve a problem of confirming the time of early-warning, considering the fact that velocity of sound is much slower than that of light. Thereby, a whole system of passive acoustic radar for detecting supersonic cruise missile is formed.     

Super-resolution Restoration of Remote-sensing Images

A novel image restoration scheme, which is super-resolution image restoration algorithm Poisson-maximum-afterword-probability based on Markvo constraint （MPMAP） combined with evaluating image detail parameter D, has been proposed. The advantage of super-resolution algorithm MPMAP incorporated with parameter D lies in the fact that superresolution algorithm MPMAP model is discrete, which is in accordance with remote-sensing imaging model, and the algorithm MPMAP is proved applicable to linear and non-linear imaging models with a unique solution when noise is not severe. According to simulation experiments for practical images, super-resolution algorithm MPMAP can retain image details better than most of traditional restoration methods; at the same time, the proposed parameter D can help to identify real point spread function （PSF） value of degradation process. Processing result of practical remote-sensing images by MPMAP combined with parameter D are given, it illustrates that MPMAP restoration scheme combined PSF estimation has a better restoration result than that of Photoshop processing, based on the same original images. It is proved that the proposed scheme is helpful to offset the lack of resolution of the original remote-sensing images and has its extensive application foreground.     

Design and Simulation of TF and TA Controller for Missile

A nonlinear terrain following(TF) and terrain avoidance(TA) controller is proposed for missile control systems. Based on classical TF algorithm (adaptive angle method), a new method for TF controller is proposed by using angle of attack. A method of obtaining terrain outline data from digital elevation map (DEM) for TF control is discussed in order to save store space. A TA algorithm is proposed by using bank-to-turn technique. The block control model, which is suitable for backstepping design, is given for nonlinear model of missile. Making full use of the characteristics of the system and combining block control principle and backstepping technique, a robust controller design method is proposed. Uncertainties in every sub-block are allowed, and can be canceled by using the idea of nonlinear damping. It is proved that the state tracking errors are converged to a neighborhood of the origin exponentially. Finally, nonlinear six-degree-of-freedom simulation results for the missile model are presented to demonstrate the effectiveness of the proposed control law.     

Design and Analysis of Test Schemes of Static Postponing Time on Shrapnels Used to Riot Control

The test scheme of static postponing time given in our actual national military test standard on shrapnels used to control riot is a nine-point test scheme on the combined action of three kinds of temperatures and three kinds of pressures,the consumed ammunitions are more excessive. Statistic analysis and tentative checkout about a lot of test data are done,feasibility gists are put forward for optimizing of the test design scheme. The optimizing design and data analysis of test scheme of the item are done by managing uniformity design theory, two scientific and reasonable six-point test schemes are confirmed. The feasibility and reliability of the optimizing design schemes put forward above are proved ulteriorly by test validating. The gained schemes not only have good design uniformity and little ammunition wastage and meet the test demand, but also have better forecast ability for the result data of other points using the mathematic models from the actual test points.     

Design of Non-fragile Satisfactory Estimator for Linear Continuous Perturbed Stochastic Systems

The design problem of non-fragile estimator is addressed for a class of perturbed linear continuous systems. The perturbations occur on the plant and estimator parameters. The estimator designed should force the error system to achieve the desired decay rate and force the steady error variance less than the specified upper bound irrdevancy of the admissible plant perturbations and estimator perturbations. Consistency problem of the decay rate with the variance upper bound is first considered via linear matrix inequality （LMI） approach. The solution of the estimator parameter under specifications to be consistent is then discussed. The consistency condition of specifications and estimator parameter solution are transformed to feasible or minimum problems subject to a set of LMI respectively. The method is illustrated by a numerical example.     

An Improved Scene-based Nonuniformity Correction Algorithm for Infrared Focal Plane Arrays Using Neural Networks

The improved scene-based adaptive nonuniformity correction （NUC） algorithms using a neural network （NNT） approach for infrared image sequences are presented and analyzed. The retlna-like neural networks using steepest descent model was the first proposed infrared focal plane arrays （IRFPA） nonuniformity compensation method, which can perform parameter estimation of the sensors over time on a frame by frame basis. To increase the strength and the robustness of the NNT algorithm and to avoid the presence of ghosting artifacts, some optimization techniques, including momentum term, regularization factor and adaptive learning rate, were executed in the parameter learning process. In this paper, the local median filtering result of Xij （ n ） is proposed as an alternative value of desired network output of neuron Xij （ n ）, denoted as Tij （ n ）, which is the local spatial average of Xij （ n ） in traditional NNT methods. Noticeably, the NUC algorithm is inter-frame adaptive in nature and does not rely on any statistical assumptions on the scene data in the image sequence. Applications of this algorithm to the simulated video sequences and real infrared data taken with PV320 show that the correction results of image sequence are better than that of using original NNT approach, especially for the short-time image sequences （several hundred frames） subjected to the dense impulse noises with a number of dead or saturated pixels.     

Piecewise Filter of Infrared Image Based on Moment Theory

The disadvantages of IR images mostly include high noise, blurry edge and so on. The characteristics make the existent smoothing methods ineffective in preserving edge, To solve this problem, a piecewise moment filter （PMF） is put forward. By using moment and piecewise linear theory, the filter can preserve edge. Based on the statistical model of random noise, a related-coefficient method is presented to estimate the variance of noise. The edge region and model are then detected by the estimated variance. The expectation of first-order derivatives is used in getting the reliable offset of edge. At last, a fast moment filter of double-stair edge model is used to gain the piecewise smoothing results and reduce the calculation. The experimental result shows that the new method has a better capability than other methods in suppressing noise and preserving edge.     

Bistatic Sonar Localization Based on Best Linear Unbiased Estimation

A best linear unbiased estimation （BLUE） algorithm for bistatic sonar localization is proposed. The Cramer-Rao bound for bistatic Sonar and the geometrical dilution of precision （GDOP） in different conditions are given. The simulation results show that the location accuracy of BLUE algorithm is higher than the weighted least square method.     

Research on Gear-broken Fault Diagnosis in a Tank Gearbox

A fault diagnosis method of working position gear in a tank gearbox is put forward based on simulating the fault of working position gear in an actual tank, extracting the envelope of vibration signal by Hilbert transformation amplitude demodulation method, and zooming the low-frequency band to envelope signal.