Beijing Key Laboratory of Health Monitoring and Self⁃Recovery for High-End Mechanical Equipment,College of Mechanical and Electrical Engineering,Beijing University of Chemical Technology,Beijing 100029,China
With the intelligent development of mechanical equipment, bearing fault diagnosis is facing more complex and changeable challenges. Traditional neural networks suffer from redundant features, limited feature recognition, and poor classification performance. To solve these problems, this paper proposes a SE-TCN⁃SVM bearing fault diagnosis model that combines a squeeze⁃and⁃excitation (SE) attention mechanism, a temporal convolutional network (TCN), and a support vector machine (SVM). By introducing the squeeze-and-excitation module, the model can adaptively enhance the weights of key channel features and optimize the modeling ability of TCN for the long-term dependence of vibration signals. The SVM classifier is used instead of Softmax to improve the robustness of sample classification by using its structural risk minimization characteristics. Experiments on bearing datasets from Case Western Reserve University and Jiangnan University show that the classification accuracy of SE⁃TCN-SVM reaches 98.92% and 96.88%, respectively. Compared with other benchmark models, it achieves better classification performance, faster training efficiency, and is suitable for different bearing data. This method enhances feature selection through the SE attention mechanism and improves generalization performance by combining SVM classifier. Our method provides a highly accurate, efficient, and adaptable solution for bearing fault diagnosis under complex working conditions.
Qian等[5]将高阶KL散度(high⁃order Kullback⁃Leibler divergence,HKL)和迁移学习结合,搭建了一个对工况变化具有鲁棒性的新型故障诊断网络。他们利用训练的卷积神经网络模型进行迁移学习,且通过校准源域和目标域分布的高阶矩来进一步适应领域分布;又将HKL散度嵌入到稀疏滤波(sparse filtering)和softmax回归中,并构建了一个基于它们的鲁棒故障诊断网络。Zhao等[6]提出在CNN中添加级联空间投影(a combination of color names and PCA,CSP),添加的CSP用于数据预处理,有效地改善了多个通道之间的空间分辨率和故障数据类别之间的可区分性,较其他模型在保障诊断准确性的同时缩短了计算时间。
虽然卷积神经网络可避免递归模型的内存消耗和梯度消失问题,但由于感受野范围限制,其长时间序列特征提取能力较差。为了解决上述问题,出现了时间卷积网络(temporal convolutional network,TCN)。TCN通过膨胀因果卷积捕捉时间序列中的长距离依赖关系,同时具备并行计算的优势,有效避免了梯度消失问题;并且通过使用因果卷积,网络模型能够更好地应用在时间序列的处理上。TCN具有灵活的感受野,可以通过设置膨胀系数来决定感受野的大小。这些特点使得TCN在振动信号处理领域表现出色,被广泛应用于轴承故障诊断中。Shi等[7]提出了基于迁移学习和深度自动编码器的TCN初始故障预测模型,他们将去噪自编码器(denoising autoencoder,DAE)和收缩自编码器(contractive autoencoder,CAE)用作前两个隐式层和最后一个隐式层,构造可以提取滚动轴承数据特征的深度自编码器(deep autoencoder,DCAE)。同时,TCN提取的数据间时序相关性能够捕捉更完整的初始故障特征与时间序列信息,改进后的模型精度和平滑度更佳。Ding等[8]提出将时间卷积网络与软阈值算法结合,用于旋转机械中的智能故障诊断,他们把连续小波变换后的振动信号作为TCN模型的输入,再用所提的自注意力机制结合时间卷积网络与软阈值算法(self⁃attention mechanism combining time convolutional network with soft thresholding algorithm,SAM⁃TCN⁃ST )来捕获基本的数据特征和分类性能。与纯TCN模型相比,SAM⁃TCN⁃ST算法提高了故障识别的精度,然而在实际使用中发现,随着卷积层和残差结构的增加,TCN结构会存在参数过多、出现大量冗余特征的问题,从而导致耗费大量训练时间。
SE模块是一种通道注意力机制,能够自适应地调整特征图中各个通道的权重,从而增强模型对重要特征的提取能力。其核心思想是通过全局平均池化(global average pooling,GAP)对特征图进行压缩,然后通过全连接层和Sigmoid激活函数生成通道权重,最后将权重与原始特征图相乘,得到加权后的特征图。
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