Expressions in Closed Form for the Angular Accuracy of a Scanning Radar

Closed-form expressions are given for the standard deviation of the error in estimating angle (usually azimuth) in a scanning radar. The formulas apply to Swerling's lower bound and to the error using a pulse-to-pulse two-pole filter. They apply to non-fluctuating and Swerling II targets and hold for all signal-to-noise ratios. Comparison with graphical results in the literature shows that the average deviation obtained using the formulas is less than 4 percent.     

Optimal guidance of extended trajectory shaping

To control missile＇s miss distance as well as terminal impact angle, by involving the timeto-go-nth power in the cost function, an extended optimal guidance law against a constant maneuvering target or a stationary target is proposed using the linear quadratic optimal control theory.An extended trajectory shaping guidance（ETSG） law is then proposed under the assumption that the missile-target relative velocity is constant and the line of sight angle is small. For a lag-free ETSG system, closed-form solutions for the missile＇s acceleration command are derived by the method of Schwartz inequality and linear simulations are performed to verify the closed-form results. Normalized adjoint systems for miss distance and terminal impact angle error are presented independently for stationary targets and constant maneuvering targets, respectively. Detailed discussions about the terminal misses and impact angle errors induced by terminal impact angle constraint, initial heading error, seeker zero position errors and target maneuvering, are performed.     

Monopulse tracking of Rayleigh targets: a simple approach

A simple derivation of the probability distribution of the monopulse ratio is presented. The derivation is based upon a conditional distribution and considers both Rayleigh targets and simple non-Rayleigh cases. The mean is obtained almost without calculation. The variance expression is given completely general noise and glint interpretation. Analytical expressions for angle error mean and spread, including noise, target width, and unresolved targets, are presented as functions of antenna position, in simple and comprehensive diagrams     

Tracking Performance of a Monopulse Radar in the Presence of Multiple Targets

The equations derived by A. J. Rainal for the probability density function of the angle error output of a monopulse radar excited by a Gaussian signal and Gaussian thermal noise are generalized to include the presence of multiple targets. The examples given demonstrate the radar's behavior for various combinations of target and noise parameters.     

一种基于三维到达角的无偏伪线性卡尔曼滤波

为了解决大场景下基于三维到达角的目标跟踪问题，提出了一种具有无偏性的伪线性卡尔曼滤波。首先，基于三维到达角信息对目标运动模型与量测模型进行建模；之后，对量测模型进行了伪线性化处理，得到了线性形式的目标量测模型。为了解决伪线性卡尔曼滤波存在的有偏性问题，提出了一种结合EKF（extend Kalman filter）的三维伪线性无偏卡尔曼滤波。仿真实验表明，该模型能够对非机动目标与机动目标有效跟踪，对于百公里级别的目标，当角测量误差从0.1°变化到0.5°，算法在仿真时间结束时均能将绝对位置误差降低至10 km以内，且算法的运行速度与EKF为同一个量级，同时兼顾了抗干扰能力、定位跟踪精度、运行效率的要求，能够为大场景下的目标跟踪提供有效方法。     

Detection of Target Multiplicity Using Monopulse Quadrature Angle

The feasibility of using the indicated quadrature angle of arrival of a monopulse radar to discriminate a single target from multiple targets, separated in angle within a radar resolution cell, is investigated. The analysis is performed for steady (fixed) and Rayleigh fluctuating targets which cover a broad range of target characteristics. In both cases, the interfering signals due to noise and clutter in the sum and difference monopulse channels are assumed to be independent, zero-mean Gaussian processes. Detection and false alarm probabilities are evaluated analytically and the receiver operating characteristics are obtained for both fixed and fluctuating target cases. It is shown that multiple targets can be discriminated from a single target condition by integrating the indicated monopulse quadrature angle of arrival from several independent pulses. It is also shown that the probability of detecting multiple targets increases as the fluctuation in the target radar cross section decreases, approaching the fixed amplitude case in the limit.     

基于超短基线声传感器阵的高速目标轨迹估计

针对低空高速飞行目标跟踪问题,首先研究了某典型目标噪声信号的时频特性,发现其信号呈现宽带低频特征,难以从频域对目标轨迹进行估计。在此基础上,从各路接收信号的到达时延量入手,考虑到声基阵只能布设于有限空间内的制约,提出了一种基于超短基线阵时延估计的目标跟踪方法。该方法利用各个超短基线阵接收声强极值点分别估计目标运动轨迹垂线方向,计算多个垂线的叉乘向量实现对目标运动方向的估计,再利用多面交汇的方式获估计得到目标运动轨迹。分别对目标俯仰角、方位角及运动轨迹估计的理论误差进行了推导,根据理论估计误差,为能够实现对目标运动轨迹的估计,各个超短基线阵应尽量保证与目标运动轨迹不在同一平面上。根据仿真结果,在采用4个传感器基阵时,角度估计平均误差在4°以内,位置估计相对误差在5%左右。仿真结果验证了该方法的有效性。     

Method for Optical-Flow-Based Precision Missile Guidance

A new precision guidance law is presented for three-dimensional intercepts against a moving target. In contrast to previously published guidance laws, it does not require knowledge of the range to the target. This makes it appropriate for use on platforms which have an imaging device, such as a video camera, as a primary sensor. We prove that with idealized dynamic model, the guidance law results in zero miss distance, and a formula is given for impact angle error which tends to zero as does target speed, making this method particularly suitable against slow moving targets. Computer simulations are used to test the law with a more realistic model, with a video camera and optical-flow algorithm providing target information. It is shown to perform well compared with another law from the literature, despite requiring less information.     

滚转舰炮制导炮弹的空间多约束导引与控制一体化设计

在大口径舰炮制导炮弹打击近岸机动目标的末段,考虑攻击角、控制受限、视线（LOS）角速率测量受限等约束,提出了一种基于块动态面与扩张状态观测器（BDSESO）的多约束空间导引与控制一体化设计（IGC）方法。构建了滚转制导炮弹的空间导引与控制一体化的严块反馈串级模型,运用扩张状态观测器估计视线角速率和目标机动、建模误差、风等系统内外不确定干扰。为了在有限时间内零化视线角跟踪误差与视线角速率,采用自适应指数趋近律设计非奇异终端滑模,通过自适应动态面控制有效镇定串级系统并避免微分膨胀,引入自适应Nussbaum增益函数补偿控制受限的饱和非线性。通过Lyapunov理论证明了视线角跟踪误差、视线角速率的有限时间收敛性与全系统状态的一致最终有界性。半实物仿真实验表明：该方法使制导炮弹在打击具有不同机动形式的目标时,均具备较好的末制导性能。     

非合作目标动态RCS仿真方法

针对非合作目标难以开展动态测量的问题,根据空气动力学原理提出了一种非合作目标动态雷达散射截面（RCS）仿真方法。该方法首先建立测量背景下典型飞行航路模型,然后计算雷达视线在机体坐标系上的时变姿态角。根据姿态角开展电磁计算,获得F-117A隐身攻击机在侧站平飞、背站拉起、对站俯冲、侧站盘旋4种航路下的动态RCS数据。着重分析了动、静态RCS特性在起伏目标检测性能评估上的差异。结果表明：静态RCS特性难以反映目标运动时真实的雷达特性,利用静态数据描述目标特性可能导致错误结论,而文中方法获取的动态RCS数据可以提高结论的完整性和可信度。     

反舰导弹对舰艇编队末端选择能力仿真

选择能力是反舰导弹的一项重要作战性能,它可以提高对编队中预选目标的搜捕概率,有效提升导弹突击效果。综合考虑反舰导弹自控终点散布误差及舰艇目标定位误差,通过蒙特卡洛仿真法,建立反舰导弹对舰艇编队目标的选择能力模型。通过仿真实验得出反舰导弹 6种不同选择模式的搜捕概率与搜索扇面角度、半径及入射角度之间的变化关系曲线图,得出了提高反舰导弹对人字形编队目标选择能力的参数设定。     

Effect of Monopulse Signal Thresholding on Tracking Multiple Targets

The monopulse angle of arrival measured from two targets may wander far beyond the angular separation of the targets. In order to remove large errors, angle of arrival measurements are passed through a threshold detector and the measurements which do not satisfy the threshold are rejected. Thresholding has the tendency to move the mean indicated angle of arrival away from the stronger target and toward the power centroid of the targets, which may be undesirable in some applications. Expressions for the probability density function, the mean, and the variance of the in-phase angle of arrival are developed in this paper as a function of the threshold setting. Background noise and interfering signals are neglected in the analysis.     

Ship target recognition using low resolution radar and neuralnetworks

The classification of ship targets using low resolution down-range radar profiles together with preprocessing and neural networks is investigated. An implementation of the Fourier-modified discrete Mellin transform is used as a means for extracting features which are insensitive to the aspect angle of the radar. Kohonen's self-organizing map with learning vector quantization (LVQ) is used for the classification of these feature vectors. The use of a feedforward network trained with the backpropagation algorithm is also investigated. The classification system is applied to both simulated and real data sets. Classification accuracies of up to 90% are reported for the real data, provided target aspect angle information is available to within an error not exceeding 30 deg     

Optimum and mismatched detection against K-distributed plusGaussian clutter

We derive the optimum radar receiver to detect fluctuating and non-fluctuating targets against a disturbance which is modeled as a mixture of coherent K-distributed and Gaussian-distributed clutter. In addition, thermal noise, which is always present in the radar receiver, is considered. We discuss the implementation of the optimum coherent detector, which derives from the likelihood ratio test under the assumption of perfectly known disturbance statistics, and evaluate its performance via a numerical procedure, when possible, and via Monte Carlo simulation otherwise. Moreover, we compare the performance of the optimum detector with those of two detectors which are optimum for totally Gaussian and totally K-distributed clutter respectively, when they are fed with such a mixed disturbance. We conclude that, though the optimum detector has a larger computational cost, it provides sensibly better detection performance than the mismatched detectors in a number of operational situations. Thus, there is a need to derive suboptimum target detectors against the mixture of disturbances which trade-off the detection performance and the implementation complexity     

High Range-Resolution Monopulse Tracking Radar

High range-resolution monopulse (HRRM) tracking radar which maintains wide instantaneous bandwidth through both range and angle error sensing channels provides range, azimuth, elevation, and amplitude for each resolved part of the target. The three-dimensional target detail can be used to improve and extend radar performance in several ways: for improved precision of target location, for target classification and recognition, to counter repeater-type ECM, to improve low-angle multipath tracking, to resolve multiple targets, as a miss-distance measurement capability, and for improved tracking in chaff and clutter. These have been demonstrated qualitatively except for the ECCM to repeater ECM and low-altitude tracking improvement. Initial results from an experimental HRRM radar with 3-ns pulse length show resolution of aircraft into its major parts and precise location of each resolved part accurately in range and angle. Realtime closed-loop tracking is performed on aircraft in flight using high-speed sampled, digitized, and processed HRRM range and angle video data. Clutter rejection capability is also demonstrated.     

基于脱靶量数据的发射系航迹参数求解方法

针对当前海态巡航飞行试验末段外测无法跟踪测量的实际问题,基于现有脱靶量测量系统,建立了利用某脱靶量测量数据到发射系的转换模型。此模型将脱靶量测量数据统一到发射系航迹中,有利于航迹分析工作。并建立了转换结果的误差估计模型,误差模型充分考虑了脱靶量测量误差、靶船定位误差以及靶船航向角误差。利用仿真数据对转换模型及误差模型进行了计算验证。结果表明,位置误差满足精度要求。该方法对延拓外测处理时段具有积极意义。     

Modified rolling guidance law for single moving mass controlled reentry vehicle against maneuvering target with impact angle constraints

This paper deals with the problem of guidance law design for the single moving mass controlled reentry vehicle when impact angle constraints and maneuvering target are taken into consideration. More specifically, a modified rolling guidance law is proposed with the interactive virtual target and the landing point prediction strategy. First, considering the fact that the roll channel can be controlled directly, the relative motion between the single moving mass controlled reentry vehicle and the ...     

基于不敏变换的动基座传感器偏差估计方法

提出了一种新的基于合作目标的动基座传感器误差绝对配准方法。该方法利用所获得的合作目标位置信息,将载体平台姿态角偏差转换为传感器测量偏差中的一部分,并建立偏差状态方程和测量方程。在此基础上,采用广义最小二乘方法以实现传感器测距误差的估计,不敏滤波的方法则用于实现平台载体的姿态偏差和角度测量偏差的实时估计。仿真结果表明,该方法实现简单,收敛速度快,可以实现单部动基座传感器的偏差估计。     

Impact time control guidance against maneuvering targets based on a nonlinear virtual relative model

Aiming at the problem of high-precision interception of air-maneuvering targets with impact time constraints, this paper proposes a novel guidance law based on a nonlinear virtual relative model in which the origin is attached to the target. In this way, the original maneuvering target is transformed into a stationary one. A polynomial function of the guidance command in the range domain with two unknown coefficients is introduced into the virtual model, one of the coefficients is determined to ...     

基于非合作目标的运动平台导航误差估计

针对运动平台位置测量通常精度不高的问题,文章基于非合作目标的运动平台导航误差估计方法,将平台的导航误差建立为随时间一阶变化的模型,求解平台的运动参数,并使用线性模型拟合不同目标相对于不同平台的位置测量。通过对比参考平台与其他平台对相同目标运动参数估计的差异,求解平台的导航误差参数,并对平台运动参数进行校正。数值仿真证明了算法的有效性,并分析了测量次数对导航误差估计精度和目标定位精度的影响。