A Causal Interventional SAR ATR Method with Limited Data via Dual Consistency
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摘要: 在小样本条件下提升方法的泛化性能,是合成孔径雷达自动目标识别(SAR ATR)的重要研究方向。针对该方向中的基础理论问题,该文建立了一个SAR ATR因果模型,证明了SAR图像中背景、相干斑等干扰在充足样本条件下可以被忽略;但在小样本条件下,这些因素将成为识别中的混杂因子,在提取的SAR图像特征中引入虚假相关性,影响SAR ATR性能。为了甄别和消除这些特征中的虚假效应,该文提出一个基于双重一致性的小样本SAR ATR方法,其中双重一致性包括类内一致性掩码和效应一致性损失。首先,基于鉴别特征应具有类内一致和类间差异的原则,利用类内一致性掩码,捕获目标的类内一致鉴别特征,甄别出目标特征中的混淆部分,准确估计出干扰引入的虚假效应。其次,基于不变风险最小化的思想,利用效应一致性损失,将经验风险最小化数据量需求转变为对效应相似度的度量需求,降低虚假效应消除对数据量的需求,消除特征中的虚假效应。因而,所提基于双重一致性的小样本SAR ATR方法可实现特征提取中的真实因果,实现准确的识别性能。两个基准数据集上的识别实验,验证了该方法的合理性和有效性,可提升小样本条件下SAR目标识别的性能。Abstract: Improving the generalization performance of methods under limited sample conditions is an important research direction in Synthetic Aperture Radar Automatic Target Recognition (SAR ATR). Addressing the fundamental problem in this field, a causal model is established in this paper for SAR ATR, demonstrating that interferences in SAR images, such as background and speckle, can be neglected under sufficient sample conditions. However, under limited sample conditions, these factors become confounding variables, introducing spurious correlations into the extracted SAR image features and affecting the generalization of SAR ATR. To accurately identify and eliminate these spurious effects in the features, this paper proposes a limited-sample SAR ATR method via dual consistency, which includes an intra-class feature consistency mask and effect-consistency loss. Firstly, based on the principle that discriminative features should have intra-class consistency and inter-class differences, the intra-class feature consistency mask is used to capture the consistent discriminative features of the target, subtracting the confounded part in the target features, and identifying the spurious effects introduced by interferences. Secondly, based on the idea of invariant risk minimization, the effect-consistency loss transforms the data requirement of empirical risk minimization into a need for labeling the similarity among effects of different samples, reducing the data demand for eliminating spurious effects and removing the spurious effects in the features. Thus, the limited-sample SAR ATR method proposed in this paper achieves true causal feature extraction and accurate recognition performance. Experiments on two benchmark datasets validate the effectiveness of this method which can achieve superior performance of SAR target recognition with limited sample.
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表 1 MSTAR数据集下的训练集与测试集
类别 训练集 测试集 数量 俯仰角 数量 俯仰角 BMP2- 9563 233 17° 195 15° BRDM2-E71 298 274 BTR60- 7532 256 195 BTR70-c71 233 196 D7-92 299 274 2S1-b01 299 274 T62-A51 299 273 T72-132 232 196 ZIL131-E12 299 274 ZSU234-d08 299 274 表 2 MSTAR数据集不同训练样本数量下10类目标的识别性能(%)
类别 每类目标训练样本数 5 10 20 25 30 40 60 80 100 BMP2 73.33 83.59 92.31 94.87 95.90 97.95 98.97 97.44 98.46 BRDM2 77.74 94.89 93.80 96.72 97.08 98.18 99.27 99.64 98.91 BTR60 83.59 86.67 91.79 94.36 94.87 95.90 98.97 96.92 97.44 BTR70 70.92 90.82 92.35 95.92 96.94 98.47 97.96 98.98 98.98 D7 68.98 83.58 92.70 95.26 95.99 97.45 98.54 99.64 99.64 2S1 81.75 80.29 93.80 95.99 97.08 98.54 98.91 99.64 98.91 T62 74.36 90.11 92.67 95.60 97.07 98.53 97.44 99.63 99.63 T72 89.80 86.22 91.84 95.41 96.94 98.47 98.98 98.98 98.98 ZIL131 68.25 85.77 93.07 96.72 97.81 98.54 98.91 99.64 99.64 ZSU234 74.45 80.29 93.80 96.72 97.08 98.18 98.54 99.64 99.64 平均值 76.13 86.38 93.00 96.07 97.01 98.24 98.79 99.32 99.35 表 3 OpenSARShip数据集中训练与测试集
类别 成像条件 训练样本数 测试样本数 总样本数 Bulk Carrier VH 和 VV, C 波段
分辨率=5~20 m
入射角=20°~45°
仰角=±11°
Rg20 m×az22 m200 475 675 Container Ship 200 811 1011 Tanker 200 354 554 表 4 OpenSARShip数据集不同训练样本数量下3类舰船目标的识别性能(%)
类别 每类训练样本数 10 20 30 40 50 60 70 80 100 200 Bulk Carrier 65.89 63.58 65.68 75.16 60.21 66.11 68.21 65.26 72.84 73.47 Container Ship 71.27 75.46 75.96 76.57 82.49 79.04 80.02 85.20 83.35 90.75 Tanker 79.10 82.77 81.92 74.01 84.46 86.16 84.46 81.92 78.81 82.77 平均值 71.51 73.75 74.41 75.66 76.58 76.92 77.66 78.86 79.41 84.12 表 5 消融实验:20个训练样本下不同消融配置的识别性能(%)
方法
配置特征 效应 BMP2 BRDM2 BTR60 BTR70 D7 2S1 T62 T72 ZIL131 ZSU234 平均值 V1 × × 80.51 75.91 74.87 80.10 73.72 76.28 78.75 82.14 84.31 86.86 79.59 V2 √ × 88.21 89.05 81.54 88.27 85.77 96.35 81.68 84.18 87.23 94.16 88.16 V3 √ √ 92.31 93.80 91.79 92.35 92.70 93.80 92.67 91.84 93.07 93.80 93.00 表 6 MSTAR数据集下SAR目标识别性能对比(%)
方法 每类样本数 10 20 40 55 80 110 165 220 All data 传统方法 PCA+SVM [14] – 76.43 87.95 – 92.48 – – – 94.32 ADaboost [14] – 75.68 86.45 – 91.45 – – – 93.51 DGM [14] – 81.11 88.14 – 92.85 – – – 96.07 数据增强 GAN-CNN [14] – 81.80 88.35 – 93.88 – – – 97.03 MGAN-CNN [14] – 85.23 90.82 – 94.91 – – – 97.81 新颖模型 Deep CNN [15] – 77.86 86.98 – 93.04 – – – 95.54 Simple CNN [16] – 75.88 – – – – – – – Dens-CapsNet [17] 80.26 92.95 96.50 – – – – – 99.75 ASC-MACN [18] 62.85 79.46 – – – – – – 99.42 本文方法 86.38 93.00 98.24 – 99.32 – – – – -
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