Full-sea Depth Sound Speed Profiles Prediction Using RNN and Attention Mechanism
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摘要: 海水中的声速剖面具有明显的时间演化特性,其预测问题可以看作一个非线性的时间序列预测问题。解决此类问题的常用方法大多使用预定义的非线性形式,无法捕捉真正潜在的非线性关系。循环神经网络作为一种为序列建模特别设计的深度神经网络,在捕捉非线性关系上具有极大的灵活性,在非线性自回归的时间序列预测这一问题上展现了它的有效性;注意力机制能够从众多信息中选择出对当前任务目标最关键的信息,对多变量时间序列在时空维度上的非线性关系进行捕捉。该文利用深度学习中的循环神经网络,添加双层注意力机制构建多变量时间序列预测模型,对浅海环境下时变的全海深声速剖面进行预测。多个模型的预测结果表明,该模型相对于单纯的编码-解码模型有着明显的预测性能提升,并且注意力权重的分布能够与实际物理现象相关联,为水声学中物理模型与机器学习的结合提供了新的思路。Abstract: The Sound Speed Profiles (SSPs) in sea water have obvious time evolution characteristics, and their prediction can be regarded as a nonlinear time series prediction. Recurrent Neural Networks (RNN), a type of deep neural network designed for sequence modeling, can capture nonlinear relationships flexibly. Attention Mechanism (AM), which selects the most critical information for the current task, can describe the nonlinear relationships in space and temporal dimensions. In this paper, RNN and AM are used to construct a multivariate time series prediction model to learn the historical SSPs and predict the time-varying full-sea SSPs in shallow sea environment. Experiments on real sound speed data show that the proposed method is effective and outperforms other methods, and provides a new idea for the combination of physical model and machine learning in underwater acoustics.
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表 1 不同模型对全海深声速剖面的预测性能
模型 数据集1 数据集2 数据集3 数据集4 $ \bar E $ $E_{ {\rm{best} } }$ $ \bar E $ ${E_{{\rm{best}}} }$ $ \bar E $ ${E_{{\rm{best}}} }$ $ \bar E $ ${E_{{\rm{best}}} }$ Encoder-Decoder (32) 0.3319 0.2370 0.5521 0.3818 0.3802 0.2264 0.2831 0.1763 Encoder-Decoder (64) 0.2899 0.2224 0.4395 0.3144 0.2590 0.2109 0.2225 0.1744 Encoder-Decoder (128) 0.2332 0.1802 0.3360 0.2631 0.2438 0.1362 0.1702 0.0925 Encoder-Decoder (256) 0.1953 0.1604 0.2732 0.1678 0.1593 0.0923 0.1399 0.0885 Encoder-Attn-LSTM (32) 0.2467 0.1308 0.3564 0.2232 0.2178 0.1028 0.1375 0.0987 Encoder-Attn-LSTM (64) 0.2263 0.1210 0.3128 0.2216 0.1884 0.1132 0.1197 0.0842 Encoder-Attn-LSTM (128) 0.2001 0.1201 0.2835 0.1881 0.1525 0.0956 0.1055 0.0691 Encoder-Attn-LSTM (256) 0.1776 0.0931 0.2595 0.2022 0.0942 0.0563 0.0919 0.0541 Decoder-Attn-LSTM (32) 0.2245 0.1672 0.3769 0.2592 0.2103 0.1076 0.1293 0.0976 Decoder-Attn-LSTM (64) 0.2091 0.1635 0.3384 0.2150 0.1879 0.1101 0.1172 0.0807 Decoder-Attn-LSTM (128) 0.2061 0.1250 0.3129 0.2427 0.1508 0.0939 0.1029 0.0667 Decoder-Attn-LSTM (256) 0.1591 0.1111 0.2658 0.1628 0.1023 0.0597 0.0911 0.0620 DA-LSTM(32) 0.1072 0.0515 0.1794 0.1005 0.1287 0.0711 0.1245 0.1010 DA-LSTM (64) 0.0975 0.0456 0.1477 0.0948 0.1068 0.0512 0.1019 0.0532 DA-LSTM (128) 0.0802 0.0428 0.1264 0.0878 0.0806 0.0459 0.0893 0.0708 DA-LSTM (256) 0.0609 0.0312 0.1116 0.0811 0.0604 0.0341 0.0768 0.0414 -
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