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Journal of ZheJiang University (Engineering Science)  2023, Vol. 57 Issue (2): 267-276    DOI: 10.3785/j.issn.1008-973X.2023.02.007
    
T-CNN time series classification method based on Gram matrix
Jun-lu WANG(),Su LI,Wan-ting JI,Tian JIANG,Bao-yan SONG*()
School of Information, Liaoning University, Shenyang 110036, China
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Abstract  

Time series classification is the basis of streaming data event analysis and data mining. A T-CNN time series classification method based on Gram matrix was proposed, aiming at the problems of loss of time attribute, low classification accuracy and low efficiency of the existing methods. Specifically, the time series was denoised by wavelet threshold to filter out normal curve noise, and a lossless transformation method based on the Gram matrix was proposed to convert the time series into time-domain images and retain all event information. Then the CNN classification method of time series was improved, and the Toeplitz convolution kernel matrix was introduced into the convolutional layer calculation to realize the replacement of convolution operation with matrix product. The Triplet network was introduced to construct the T-CNN classification model, and the square loss function of CNN was optimized by calculating the similarities between similar events and different kinds of events, so as to improve the convergence rate of gradient descent and the classification accuracy of the T-CNN model. Experimental results show that compared with the existing methods, the proposed T-CNN time series classification method can improve the classification accuracy by 35%, the classification precision by 35% and the classification efficiency by 40%.



Key wordsGram matrix      T-CNN model      Toeplitz      loss function      Triplet network     
Received: 28 July 2022      Published: 28 February 2023
CLC:  TP 181  
Fund:  国家重点研发计划资助项目
Corresponding Authors: Bao-yan SONG     E-mail: wangjunlu@lnu.edu.cn;bysong@lnu.edu.cn
Cite this article:

Jun-lu WANG,Su LI,Wan-ting JI,Tian JIANG,Bao-yan SONG. T-CNN time series classification method based on Gram matrix. Journal of ZheJiang University (Engineering Science), 2023, 57(2): 267-276.

URL:

https://www.zjujournals.com/eng/10.3785/j.issn.1008-973X.2023.02.007     OR     https://www.zjujournals.com/eng/Y2023/V57/I2/267


基于Gram矩阵的T-CNN时间序列分类方法

时间序列分类是流式数据事件分析和数据挖掘的基础. 针对现有方法损失时间属性、分类准确率低、效率低等问题,提出基于Gram矩阵的T-CNN时间序列分类方法. 该方法对时间序列进行小波阈值去噪,过滤正态曲线噪声,提出基于Gram矩阵的无损时间域图像转换方法,保留事件全部信息. 改进时间序列CNN分类方法,在卷积层计算引入Toeplitz卷积核矩阵,实现矩阵乘积替换卷积运算. 引入Triplet网络思想,构建T-CNN分类模型,通过计算同类事件与不同类事件间的相似度优化CNN的平方损失函数,提高T-CNN模型梯度下降的收敛速率及分类准确性. 实验表明,相比现有方法,T-CNN时间序列分类方法能够提高35%的分类准确率、35%的分类精确率及40%的分类效率.


关键词: Gram矩阵,  T-CNN模型,  Toeplitz,  损失函数,  Triplet网络 
Fig.1 Schematic diagram of time series
Fig.2 Schematic diagram of time series polar coordinates
Fig.3 Time domain image diagram
Fig.4 Schematic diagram of Toeplitz matrix transformation process
环境 配置
CPU Intel Core(TM)i7-7500U
内存 8 GB
硬盘容量 1 TB
操作系统 Windows 8.1 (64bit)
编程语言 Java
JDK版本 1.7.0_45
Tab.1 Software and hardware environment
Fig.5 Result diagram of T-CNN model iteration times
Fig.6 Comparison of classification accuracy of different classification models
Fig.7 Comparison of classification precision of different classification models
Fig.8 Comparison of classification recall of different classification models
Fig.9 F1 comparison of different classification models
Fig.10 Comparison of classification efficiency of different classification models
Fig.11 Comparison of Toeplitz convolution and traditional convolution running time
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