Single Radar Measurement Method for Antiaircraft Projectile Miss Distance

To measure miss distance for antiaircraft projectile,a radial velocity identification and positioning method with a single radar is proposed. By analyzing the spatial resolution of multi-frequency ranging radar,the discrimination and testing model of this radar for multi-targets（ projectile and target） is established to analyze the systematic error of antiaircraft miss distance. Then through the aerial target flight test and contrast test with optical test equipment,the validity of the measurement method is verified. This newmethod has the potential to be used in the measurement of antiaircraft projectile miss distance.

Multiple targets vector miss distance measurement accuracy based on 2-D assignment algorithms

An extension of 2-D assignment approach is proposed for measurement-to-target association for improving multiple targets vector miss distance measurement accuracy. When the multiple targets move so closely, the measurements can not be fully resolved due to finite resolution. The proposed method adopts an auction algorithm to compute the feasible measurement-to-target assignment with unresolved measurements for solving this 2-D assignment problem. Computer simulation results demonstrate the effectiveness and feasibility of this method.

Effect of direction error on the miss distance of rolling missiles with x-rudder

Based on the analysis of periodic equivalent control force of rolling missiles with x-rudder, the guidance loop model with direction error is established and the relationship between direction error and miss distance is analyzed. Results show that the miss distance is zero or a constant or infinite, and it is always zero when the real parts of system matrix eigenvalues decided by direction error are both positive values in an ideal system, in which all the lags are neglected. However, the miss distance gradually increases with the increase of the direction error and its variation is small when direction error is not more than 5° in the system, in which seeker lag and missile body lag are considered.

Distribution of Miss Distance in Discrete-Time Controlled System with Noise-Corrupted State Information

Miss distance is an important parameter of assessing highly maneuvering targets interception. Due to the noise-corrupted measurement and the fact that not all the state variables can be directly measured, the miss distance becomes a random variable with a priori unknown distribution. Currently, such a distribution is mainly evaluated by the method of Monte Carlo simulation. In this paper, an analytic approach is obtained in discrete-time controlled system with noise-corrupted state information. The system is subject to a bang-bang control strategy. The analytic distribution is validated through the comparison with Monte Carlo simulation.

Distribution of Miss Distance for Pursuit-Evasion Problem

Miss distance is a critical parameter of assessing the performance for highly maneuvering targets interception(HMTI). In a realistic terminal guidance system, the control of pursuer depends on the estimate of unknown state, thus the miss distance becomes a random variable with a prior unknown distribution. Currently, such a distribution is mainly evaluated by the method of Monte Carlo simulation. In this paper, by integrating the estimation error model of zero-effort miss distance(ZEM) obtained by our previous work, an analytic method for solving the distribution of miss distance is proposed, in which the system is presumed to use a bang-bang control strategy. By comparing with the results of Monte Carlo simulations under four different types of disturbances(maneuvers), the correctness of the proposed method is validated. Results of this paper provide a powerful tool for the design, analysis and performance evaluation of guidance system.

A SKELETONIZATION ALGORITHM BASED ON EUCLIDEAN DISTANCE MAPS AND MORPHOLOGICAL OPERATORS

In this letter a new skeletonization algorithm is proposed. It combines techniques of fast construction of Euclidean Distance Maps(EDMs), ridge extraction, Hit-or-Miss Transformation(HMT) of structuring elements and the set operators. It first produces the EDM image with no more than 4 passes through an image of any kinds, and then the ridge image is extracted by applying a turn-on scheme and performing a rain-fall elimination to accelerate the processing. The one-pixel wide skeleton is finally acquired by carrying out the HMTs of two structure elements and the SUBTRACT and OR operations. Experimental results obtained by practical applications are also presented.

Robust H-infinity filtering for time-delaysystems with missing measurements:a parameter-dependent approach

Robust H-infinity filtering for a class of uncertain discrete-time linear systems with time delays and missing measurements is studied in this paper. The uncertain parameters are supposed to reside in a convex polytope and the missing measurements are described by a binary switching sequence satisfying a Bernoulli distribution. Our attention is focused on the analysis and design of robust H-infinity filters such that, for all admissible parameter uncertainties and all possible missing measurements, the filtering error system is exponentially mean-square stable with a prescribed H-infinity disturbance attenuation level. A parameter-dependent approach is proposed to derive a less conservative result. Sufficient conditions are established for the existence of the desired filter in terms of certain linear matrix inequalities （LMIs）. When these LMIs are feasible, an explicit expression of the desired filter is also provided. Finally, a numerical example is presented to illustrate the effectiveness and applicability of the proposed method.

改良数字化导板对第二磨牙游离缺失辅助种植的精确度

背景:静态数字化导板辅助种植可提高种植精度,但对于开口度小和种植位点牙合间距离小的患者后牙区使用较为受限,为此需要对数字化导板进行改良。目的:研究改良数字化导板对第二磨牙游离缺失辅助种植的精确度。方法:选择2020年7月至2023年7月就诊于广州医科大学附属第一医院的第二磨牙游离缺失患者40例,采用掷硬币法随机分为试验组(n=22)与对照组(n=18),分别接受改良数字化导板辅助种植手术与常规自由手种植手术。对患者术前及术后锥形束CT进行重叠分析,比较组间的颈部偏差、尖端偏差、深度偏差、角度偏差值。术后1周,通过目测类比评分评估患者对手术过程的满意度。结果与结论:①试验组植入25颗种植体(上颌12颗,下颌13颗),对照组植入23颗种植体(上颌8颗,下颌15颗),试验组患者颈部偏差、尖端偏差、深度偏差、角度偏差值均小于对照组(P<0.05,P<0.001);试验组组内上颌种植位点与下颌种植位点精确度比较无差异(P>0.05);②两组患者对手术过程的满意度比较差异无显著性意义(P>0.05);③结果表明,改良数字化导板对第二磨牙游离缺失辅助种植可提高手术精度,适用于开口度小和种植位点牙合间距离小的患者后牙区。

Optimal Guidance Law to Maximize Terminal Velocity for Missiles with Impact Angle Constraint

In this paper,an optimal guidance law for missiles with impact angle and miss distance constraints is proposed to achieve the maximal terminal velocity. The normal acceleration command that includes the timevarying coefficients is introduced to satisfy the desired impact angle as well as zero miss distance according to the geometric relation and relative motion parameters between missile and target. The problem is formulated as an optimal control problem by defining the angle of velocity error and flight-path angle as state variables and maximizing a performance index of the terminal velocity. The analytical form of the proposed guidance law is obtained as the solution of the optimal control problem combining optimal control theory and numerical value computation method. Nonlinear simulations of various situations demonstrate the performance and feasibility of the proposed optimal guidance law.

Calculation model of military aircraft suryiyability to a missile

Since missiles are main threat against aircrafts in air war,a model is proposed for calculating the aircraft survivability to a missile.The hit characteristic of aircraft to a missile is analyzed,and then Monte Carlo method is applied to generate missile detonation location according to its distribution rule.In addition,based on the analysis of fragment trajectory and critical components,the intersection point of these two is determined.Then the kill probability of critical component to a fragment can be calculated,and the aircraft survivability to a missile is obtained accordingly.Finally,the feasibility of the proposed method is demonstrated.Simulation results show that this method captures the basic effects of missile detonation locations on aircraft survivability,which may provide an effective reference to aircraft survivability research.

Research on terminal maneuver strategy of anti-ship missiles

To design the terminal maneuver strategy of an anti-ship missile,first,the analytical solution of miss distance when an anti-ship missile has planar weaving maneuver and three-dimension spiral maneuver is presented,in which not only the amplitude and frequency are considered but also the initial phase is taken into account.Next,based on the analytical solution of miss distance,the effects on the miss distance of the amplitude,frequency,initial phase of the anti-ship missile＇s maneuver acceleration and the order of flight control system of the air-ship missile are analyzed.Finally,the optimum weaving maneuver and spiral maneuver which make the miss distance be the largest under some conditions are designed,which is of important meaning for increasing the survival probability of the anti-ship missile.

基于概率密度的自适应k近邻缺失值填充方法

基于k近邻的缺失值填充方法通常使用样本间的距离来度量样本的相似性,在计算距离时,没有区分样本各属性的权重,即所有属性对距离的贡献是一样的。然而,在非均匀分布的不平衡数据集中,样本的异质性往往体现在取值不常见的属性上,即样本之间的相似性受属性取值概率影响,此时用传统的距离公式来度量相似性是不够准确的。因此,文章针对非均匀分布的不平衡数据集提出了一种自适应k近邻缺失值填充方法(AkNNI):首先,引入属性的概率密度,动态调整各个属性的重要性,凸显稀疏值与缩小频繁值在距离计算上的贡献,从而更好地表达样本的异质性以及捕捉样本之间的相似性;然后,针对高缺失率下数据集中完备样本稀少的情况,综合考虑了样本的相似性和完整性,设计了新的k近邻的选择流程。实验选取了6个非均匀分布数据集,对比了AkNNI方法与其他5种经典填充方法的填充效果,验证了填充后的数据集在k近邻分类器的分类效果,深入探索了3种评估指标的相互关系。实验结果表明AkNNI方法具有更高的填充准确度和分类准确度:在6种缺失值填充算法中,AkNNI方法在各个数据集上取得的平均RMSE最低、平均皮尔逊相关系数最高以及平均分类准确率最高。同时,在高缺失率下,AkNNI方法在各个数据集上仍能保持较低的RMSE、较高的皮尔逊相关系数和较高的分类准确度。

基于YOLOv8改进的脑癌检测算法

自动检测脑部肿瘤在磁共振成像中的位置是一个复杂、繁重的任务,需要耗费大量时间和资源。传统识别方案经常出现误解、遗漏和误导的情况,从而影响患者的治疗进度,对患者的生命安全产生影响。为了进一步提高鉴定的效果,引入了4项关键改进措施。首先,采用了高效的多尺度注意力EMA(Efficient Multi-scale Attention),这种方法既可以对全局信息进行编码,也可以对信息进行重新校准,同时通过并行的分支输出特征进行跨维度的交互,使信息进一步聚合。其次,引入了BiFPN(Bidirectional Feature Pyramid Network)模块,并对其结构进行改进,以便缩短每一次检测所需要的时间,同时提升图像识别效果。然后采用MDPIoU损失函数和Mish激活函数进行改进,进一步提高检测的准确度。最后进行仿真实验,实验结果表明,改进的YOLOv8算法在脑癌检测中的精确率、召回率、平均精度均值均有提升,其中Precision提高了4.48%,Recall提高了2.64%,mAP@0.5提高了2.6%,mAP@0.5:0.9提高了7.0%。

行进间地面机动目标射击诸元解算方法

针对地面机动目标运动模式未知、无源跟踪缺乏距离量测信息导致传统射击诸元解算方法解命中精度下降的问题,提出一种基于纯角度测量的行进间地面机动目标射击诸元解算方法。在传统固定参数的当前统计(CS)模型基础上,利用模糊推理动态调整机动频率,并根据加速度历史估计信息设置机动加速度方差,提高目标方位角的估计精度;在一次测距的基础上,基于简化刚体弹道模型,利用割弦迭代法计算出命中点坐标,并在每次迭代中利用虚拟脱靶量对射击诸元进行修正,减少对弹道方程的计算次数,提高射击诸元解算的实时性和精度。仿真结果表明,该方法有效可行,基于模型参数自适应的CS模型提高了目标角度跟踪的精度,基于虚拟脱靶量的迭代修正算法提高了诸元解算的实时性,解命中精度相对于传统射击诸元解算方法得到了显著改善。

基于类的余弦距离聚类缺失值填补方法研究

【目的】为了解决欧氏距离计算相似性带来的高维度问题,提出了基于类的余弦距离聚类缺失值填补方法。【方法】首先将不完整数据集分为两个不同的组(G1和GIM);其次通过聚类中心对GIM组中的缺失数据进行预填补;再次利用余弦距离计算相关性;最后选择与G1组中距离最小的数据来填补缺失值。【结果】实验结果表明,该方法在类别和混合数据集上均优于其他插补方法。【结论】该方法显著提高了准确率、召回率、F1-score及插补效果。

基于无人机目标跟踪的舰炮脱靶量测量系统

脱靶量是检验部队训练水平、武器性能的一个重要指标,同时也是优化方法、改善参数的重要反馈依据。针对海面舰炮脱靶量测量成本高、方式复杂、受海面气候影响大、测量精度不高等问题,提出了一种基于无人机目标跟踪的舰炮脱靶量测量方法。该方法使用无人机作为观测平台,通过与靶船通信,确定规则的相对运动,拍摄清晰的脱靶图像及相关位置信息。地面站系统利用YOLOv5-DeepSORT目标检测和跟踪算法对炸点水柱进行检测和跟踪,从而实现对炸点水柱脱靶量的测量。该方法实施简单,测量精度高,可有效增强脱靶量测量的效果,提高部队的战斗力水平。

脱靶量测量技术综述

对鉴定和评估精确制导武器的性能起关键作用的脱靶量测量技术进行了综述,介绍了脱靶量测量的几个主要方向和发展现状。归纳了脱靶量量测量的基本体制、基本工作方式和基本原理,对当前国际、国内最先进的基于非协同式无线电脱靶测量系统做了详细介绍,总结了国内外脱靶量测量技术的发展过程和研究现状,展望了脱靶量测量技术的发展趋势。矢量脱靶量测量技术的发展主要集中在多普勒雷达和冲击雷达两种体制上,其中采用冲击雷达技术的矢量脱靶量测量系统是今后发展的重要方向。

简易制导脉冲控制力修正技术研究

根据开发低成本脉冲修正弹药的实际需要,研究一种开环修正的方法.从弹道的角度建立弹道模型,分析了修正距离与脉冲控制力大小的关系以及脉冲发动机级数与脱靶量之间的关系.根据最大散布误差和最大脱靶量指标选择脉冲控制力大小,并对脉冲发动机分级.通过对8级脉冲发动机参数进行的仿真计算,验证了此修正方法的可行性.

激光跟踪仪精密跟踪系统的设计

对激光跟踪仪的跟踪伺服控制系统进行了整体研究并给出了总体设计方案。针对跟踪目标的精密探测问题,研究了新型探测手段以及微弱光电信号的精细调理技术与数字滤波方法,使得脱靶量探测稳定性优于±2.0μm。针对跟踪角度精密测量问题,设计了圆光栅数据采集系统,实现了角度脉冲的细分、辨向与准确计数;基于谐波分析方法建立了跟踪过程中的误差补偿模型,将角度测量精度由3.5″提高到1.5″。建立了跟踪伺服电机的数学模型,分析了电流环在跟踪控制中的作用机理,提出了电流、速度、位置三闭环控制结构和复合跟踪控制策略。跟踪实验表明:系统最远跟踪距离不小于41.7m,跟踪速度不低于2.0m/s。该项技术还能为空间动态目标跟踪、激光通信等提供有益借鉴。

红外捕获跟踪设备闭环注入式仿真试验的理论研究

提出了一种采用数字图像注入式方法进行红外捕获跟踪设备闭环仿真和性能测试。在仿真测试时,红外捕获跟踪设备的传感器被图像仿真机和图像注入设备取代,图像生成及脱靶量计算环节的延迟和误差使跟踪伺服系统的性能与实际工作情况不一致,影响了仿真试验结果精度和置信度。从设备的实际情况和注入式仿真试验下伺服控制系统的等效性考虑,利用某型实际设备的伺服控制系统模型,仿真分析了在不同脱靶量延时和脱靶量误差下,系统跟踪迎头飞行目标时的稳定性和动态跟踪精度的变化,获得了设备允许的脱靶量大小和图像仿真最大延时。结果表明:脱靶量输出延迟不大于2帧时设备能稳定跟踪目标,为保持两种情况下伺服系统性能的一致,注入式试验时脱靶量随机误差最大为25″,图像仿真的最大延迟时间为19 ms。研究成果为红外捕获跟踪设备的闭环注入式仿真试验的可行性提供了理论支撑。