弹箭磁屏蔽效能仿真及分析

为了分析磁传感器的测量误差,建立了弹体静磁屏蔽效应数学模型,利用ANSYS软件进行弹体三维磁场仿真,分析了弹体相对磁导率、壁厚等自身因素对磁屏蔽系数的影响,仿真结果与理论计算结果一致。仿真研究并拟合出弹体磁屏蔽系数与弹体姿态角之间的关系。结果表明,当弹轴与磁场方向平行时,磁屏蔽系数最小,随着夹角的增大,磁屏蔽系数增大,当弹轴与磁场方向垂直时,磁屏蔽系数最大。建立了磁屏蔽椭球模型,提出直接获取软磁误差矩阵的方法,为磁传感器的误差校正提供了理论基础;给出了利用磁屏蔽椭球模型直接解算弹体相对于地磁矢量姿态角的方法,为磁传感器在弹上的应用提供了理论基础。     

基于有限元的弹体磁屏蔽效能分析

在地磁导航系统中,弹体的磁屏蔽作用对磁传感器的测量带来很大的误差。为了对该误差进行补偿,文中采用ANSYS软件对弹体的磁屏蔽效能进行分析。首先针对无限长圆柱腔的弹体磁屏蔽系数进行数学建模得到理论值,然后采用ANSYS软件进行仿真分析得到实验值,最后分析得到了磁导率对弹体磁屏蔽系数的影响规律。通过比较可得实验值与理论值的误差很小,验证了利用有限元方法对弹体磁屏蔽效能进行分析的可行性。     

基于地磁传感器的弹体姿态测量方法

针对现有求解弹体姿态角方法存在易受天气影响、不易分析解的存在性的不足,提出了一种基于地磁传感器的弹体姿态测量方法。该方法基于弹体坐标系及弹轴坐标系之间的转换关系求得弹轴坐标系上磁场强度,并通过迭代的方法解算出弹体姿态角,解决了常规利用磁传感器求解弹体姿态角难以分析解的存在性的问题。仿真结果表明,姿态角解算结果具有较小的误差,且不随时间积累,能实现对弹体的姿态测量。     

基于非正交磁传感器组合的旋转弹体横滚角测试

针对微惯性传感器测量误差随时间严重发散且量程不能满足旋转弹体横滚角测量的要求,采用磁传感器组合对旋转弹体的横滚角测量及工程可实现性进行了研究。对于不同角度、位置安装的磁传感器,给出了其敏感轴上的数学表达式,并且利用两个非正交安装的磁传感器输出的极值之比与俯仰角呈固定关系进行姿态角求解。分析了产生奇异的条件和使用磁传感器进行横滚角测量的可行性,并对传感器布阵方案及解算方法进行了半实物实验。实验结果表明,俯仰角和横滚角的解算误差基本控制在1°以内,此测量方案适用于偏航角变化不大的旋转弹体。     

基于两磁传感器极值比值的弹体横滚姿态测量

针对高转速弹体飞行过程中的高速旋转,微惯性器件无法满足测量要求的问题,提出利用两个磁传感器组合测量姿态的方法.将磁传感器组合中的一个与弹轴成锐角安装,利用两磁传感器输出的极值信息,采用极值比值的方法确定姿态,无需知道地磁场强度且解算过程中只需要标量运算.与Thomas Harkins,David Hepner提出的零交叉法相比,姿态角信息多且是单值的.针对极值比值算法及磁传感器安装角度误差进行了仿真,仿真结果表明:该算法具有较高的精度,解算的姿态角与真实姿态角相符;对磁传感器的位置误差修正后,姿态角的解算精度有所提高.     

高速旋转弹载体干扰磁场补偿算法

为解决高速旋转弹载体磁场会严重影响捷联地磁传感器的测量精度问题,文中在对弹体的载体干扰磁场机理分析与误差建模基础上,提出了基于Kalman滤波技术的弹体载体磁场误差参数估计与补偿方法。最后以152 mm旋转弹药载体磁场为研究仿真对象,对所述载体磁场补偿方法进行了算法仿真验证,结果表明该算法可有效实现载体磁场误差参数的准确估计,且地磁传感器测量数据在经误差补偿后,其测量精度提高一个数量级。     

基于动态学习策略多群体粒子群的消磁站水下磁传感器位置校正方法

消磁站海底敷设磁传感器是舰艇磁场测量的主要形式之一，水下磁传感器的位置偏差直接影响着舰艇磁场的测量精度和防护能力评估。针对现有方法难以准确定位消磁站水下磁传感器的问题，提出一种基于动态学习策略多群体粒子群的消磁站水下磁传感器位置校正方法。该方法首先将通电载流线圈等效成磁偶极子磁源，再通过线性多重计量方法改变磁源与磁传感器的相对位置以获取多组磁传感器磁场测量数据，据此建立水下磁传感器位置校正模型，并采用动态学习策略多群体粒子群优化算法优化求得位置偏差矢量，从而实现水下磁传感器位置的高精度校正。在综合分析磁偶极子等效误差等主要影响因素的基础上，设计了数值模拟实验和物理缩比模型实验，结果表明：该方法可有效解决消磁站水下磁传感器的位置校正问题，校正后x轴、y轴和z轴三个方向的位置误差均小于0.1 m。经过校正后的消磁站磁场测量精度可以满足舰艇磁场测量要求，该方法可以对消磁站位置安装偏差不大于0.3 m的水下磁传感器完成校正工作，具有较好的实用价值。     

高速旋转弹捷联磁传感器在线校准方法

针对高速旋转弹用磁传感器的误差校准参数在发射前后发生变化,造成磁测姿态误差较大的问题,文中提出了基于递推最小二乘估计的磁传感误差参数的在线校准方法。滤波器选取磁传感器的误差模型为系统的动态方程,磁传感器输出作为量测信息,采用递推最小二乘估计完成误差参数估计。以152 mm炮射榴弹为仿真对象,对所设计的滤波器进行仿真验证,结果表明该方法能有效的提高磁测姿态系统的测量精度。     

基于磁传感器/GPS组合制导飞行弹体的姿态和位置估计

提出一种基于磁传感器/GPS组合制导的飞行弹体的姿态和位置估计方法。使用两个简化的随机动态方程分别建立飞行弹体的轨迹和姿态动态模型，利用GPS和磁传感器的测量值，基于Kalman滤波和Unscented变换(UT)的组合滤波器，得到弹体轨迹和姿态角的估计值。对155 mm旋转弹的仿真结果表明了该方法的可行性和有效性。     

某常规弹载体感应磁场分布的仿真技术研究

在常规弹的地磁导航系统中,载体磁场是影响磁传感器测量精度的主要干扰因素。为了准确地对这一干扰磁场加以消除或者补偿,文中对载体磁场中感应磁场的分布规律进行了仿真研究。文中采用磁标量法求解磁场,研究了常规弹的三维静态磁场仿真技术,使用有限元工具ANSYS仿真得到了弹体上各点磁感应强度的数值解,根据绘制的云图和数据变化曲线图,分析得到了匀强磁场中弹体内部以及沿弹壁轴向和横截面上感应磁场的变化规律。     

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.