【作者】 沈明华；

【导师】 庄钊文； 付强；

【作者基本信息】 国防科学技术大学 ， 信息与通信工程， 2008， 博士

【摘要】 本文以“973”国家安全重大基础研究项目“雷达自动目标识别新机理、新方法研究”为背景,着重从特征提取和分类器设计两个方面研究高分辨雷达目标分类识别的理论与关键技术,主要涉及以下三方面内容:基于散射中心参数估计的分布特征提取、高分辨雷达目标分类中支持向量机参数优化和支持向量数据描述单类分类器向多类分类推广。(1)基于散射中心参数估计的分布特征提取方面针对传统估计方法分辨力低、估计的散射点位置特征无法直接用于目标分类的问题,提出了一种基于散射中心径向相对位置估计的分布特征提取方法,该方法首先通过回波预测目标散射中心个数,然后对散射中心的幅度和位置信息进行高分辨估计,并依据估计结果提取散射中心间相对距离信息组成特征向量。经仿真实验验证,所提取的分布特征与传统方法中位置特征相比更稳定,并在一定角度范围内具有旋转和平移不变性,最后基于该特征提取方法实现了对三类目标的有效识别,并与已有方法进行比较,验证了该方法的有效性和稳健性。(2)高分辨雷达目标分类中支持向量机分类器参数优化方面针对以往基于遗传算法支持向量机参数优化中适值函数选取与研究背景结合不紧密且缺乏理论指导、参数优化时参数搜索范围靠人工盲目指定、遗传算法不能根据遗传迭代进展情况自适应调整造成收敛过快或过慢等问题,开展了以下几个方面研究:首先,从估计精度、运算时间代价、稳健性等方面比较了常用泛化误差估计方法的性能,选出了适合高分辨雷达目标分类的泛化误差估计方法,得到了遗传算法的适值函数。其次,基于高分辨一维距离像,分析了参数与支持向量机泛化能力的关系,为后续参数优化中参数搜索范围确定提供了参考依据,避免了人工指定的盲目性。最后,提出了一种基于改进遗传算法的支持向量机参数优化和特征提取方法,可同时优化核函数参数、惩罚因子、组合核系数、以及遗传算法的交叉率和变异率。并可以根据遗传算法迭代情况自适应调整交叉变异率。通过对三类目标高分辨一维距离像的分类实验,验证了所提出优化方法的有效性。(3)在支持向量数据描述单类分类器向多类分类推广研究方面支持向量数据描述是一种单类分类器,不能直接用于多类分类,针对此问题,开展了以下研究:首先比较了支持向量数据描述、最近邻数据描述、K近邻数据描述、K均值聚类数据描述等常用数据描述方法的性能,然后简单研究了核函数参数对支持向量数据描述分类边界的影响,最后基于最小距离规则和阈值处理策略提出了一种支持向量数据描述多类分类算法(SVDD_MDRTS),实现了支持向量数据描述从单类分类器向多类分类的推广。采用仿真实验,分析了核函数参数、噪声等因素对SVDD_MDRTS算法性能的影响,结果表明存在最优参数值使算法性能最佳且算法具有较好的抗噪性能。采用高频电磁散射数据对SVDD_MDRTS算法的分类性能进行了验证,设定几种测试条件,从识别混淆矩阵和识别ROC曲线等方面验证了不同条件下算法的性能,并将SVDD_MDRTS与SVM、NN多类分类器在识别性能和测试时间两方面进行了比较,结果表明SVDD_MDRTS具有更好的分类性能、测试和训练时间更短。更多还原

【Abstract】 All the work in the dissertation is supported by the project of“973”National Security Important and Foundational Research, which is focused on investigation of the new mechanism and methods in radar automatic target recognition. Aiming at the background of high-resolution radar target classification, the feature extraction of scattering center parameter estimation and the key technique of classifier based on kernel method are investigated. Three important issues are included, which are feature extraction method based on scattering centers parameter estimation, parameter optimazation of Support Vector Machine (SVM) in high resolution radar target classification and research on generalizing Support Vector Data Description (SVDD) to multi-class classification.In the aspect of feature extraction of scattering center parameter estimation, one new feature extraction method is proposed. The resolution of traditonal methods is low and the extracted position of scattering centers cannot be directly used in radar target classification. The scattering center number estimation is performed and the amplitude and position of scattering centers are estimated based on one super-resolution method. Then the distributed feature of relative distance between scattering centers is extracted, which is rotationally and translationally invariant compared with position feature itself in a certain aspect scope. Finally by identifying one-dimensional range profiles of three targets, the effectiveness and robustness of the proposed method are testified.In the aspect of SVM parameters optimazation in high-resolution radar target classification, one parameter optimization method based on improved Gentic algorithm (GA) is proposed.Aiming at the problems of loose relationship between fitness function selection of GA and research background, blind determination of parameter searching scope and nonautomatic adjustation of GA convergence, several problems have been investigated.The fitness function selection in high-resolution radar target classification is investigated firstly. Parameter optimization performances of several generalization error estimation methods are analyzed and the estimation precision, computing time cost and robustness are compared respectively. One estimation method fit for SVM parameters optimization in high range resolution radar target classification is chosen as the fitness function of GA.Then the relationship between parameters and performance of SVM classifier is studied using one-dimensional range profiles. The parameter seaching scope is determined by analyzing the relationship. The study here overcomes the blind determination of parameter searching scope. In the end, one parameter optimization and feature extraction algorithm based on improved GA is proposed. Parameters such as kernel function parameter, penalty factor, composite kernel coefficient, the crossover ratio and mutation ratio of GA are all optimized simultaneously. The improved GA can automatically adjust the crossover and mutation ratios according to the state of GA progress, which overcomes the fast-speed or low-speed convergence of GA because of inappropriate crossover and mutation ratio. At last by classifying radar range profiles of three targets, the effectiveness of the algorithm is testified.In the aspect of research on generalizing SVDD to multi-class classification, one SVDD multi-target classification method based on minimal distance classifier is brought forward.SVDD is a one-class classifier and it cannot be directly used in multi-class classification. To solve this problem, research has been performed as follows.The performances of SVDD and other data description method are compared and then the relationship between kernel function parameter and SVDD classifier is analyzed. Finally, based on the idea of minimum distance classifier and threshold strategy, one SVDD multi-class classification algorithm is propsed, which is nominated as SVDD_MDRTS. Based on simulation range profiles, the effects of kernel function parameter and noise on SVDD_MDRTS are analyzed. Based on high-frequency electronic and magnetic scattering data, the confusion matrix and Receiver Operating Characteristic (ROC) curve are investigated. Finally the classification performance and testing time of SVDD_MDRTS, SVM and NN are compared, experimental results indicate that SVDD_MDRTS has better perfomance and shorter training and testing time than SVM and NN.更多还原