Research on TEDS image defect detection based on lightweight linear self-attention reverse knowledge distillation network
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摘要:
动车组运行故障图像检测系统((trouble of moving electric multiple units detection system, TEDS)需进行检测的部件形态多样、体积大小不一, 导致既有的检测方法误报率、漏检率高, 提出一种伪缺陷多头深度可分离自注意力反向知识蒸馏网络进行TEDS图像的无监督缺陷检测. 首先通过深度可分离卷积取代矩阵生成自注意力头向量,并以聚焦函数调整相似度的尖锐分布, 构建的多头深度可分离线性自注意力享有线性运算复杂度;其次通过倒瓶颈残差模块和多头深度可分离线性自注意力模块构建以轻量级教师-学生模型为主干的反向知识蒸馏网络, 提高网络特征提取能力的同时减少网络可训练参数量, 加速检测速度;在教师网络各个模块后设置投影层, 同时采用Simplex和随机裁剪伪缺陷机制来模拟训练过程中的伪缺陷样本, 通过多重损失引导投影层从正常特征空间中推开缺陷信息, 迫使投影层专注于探索正常特征的更深层表示来限制缺陷信息流向学生网络, 使得教师、学生网络对缺陷有更大的特征差异. 研究表明, 改进后的网络能有效提高TEDS图片的缺陷检测能力, 评价指标Sample-Auroc、pixel-Auroc、Aupro分别达到94.6%、91.7%、80.1%, 和其他算法对比, 分别提高3.3、3.8、4个百分点;且能够取得0.37秒/张的TEDS缺陷检测速度, 满足TEDS系统的实时性需求.
Abstract:
The trouble of moving electric multiple units detection system (TEDS) needs to detect components with diverse shapes and sizes, which leads to high false positive and missed detection rates in existing detection methods. Therefore, a pseudo anomaly multi-head depth separable self-attention reverse knowledge distillation network is proposed to achieve anomaly detection on TEDS images. Firstly, the self-attention head vector is generated by replacing the matrix with depthwise separable convolution, and the sharp distribution of similarity is adjusted with a focus function. The constructed multi-head depthwise separable linear self-attention enjoys linear computational complexity. Secondly,a lightweight attention teacher-student model based reverse knowledge distillation network is constructed using a bottleneck residual module and a multi-head depth separable linear self-attention module, which improves the network’s feature extraction ability while reducing the number of trainable parameters, and accelerates the detection speed. Projection layers are set after each module of the teacher network. Meanwhile, the Simplex and random cropping pseudo-defect mechanisms are employed to simulate pseudo-defect samples during training. Through multi-loss guidance, the projection layers are pushed away from the normal feature space to exclude defect information, forcing them to focus on exploring deeper representations of normal features and restricting the flow of defect information to the student network, resulting in greater feature differences between the teacher and student networks for anomaly. Research shows that the improved network can effectively enhance the anomaly detection capability of TEDS images; the evaluation metrics of image-Auroc, pixel-Auroc, and Aupro reach 94.6%, 93.3%, 80.1%, respectively. Compared with other algorithms, these metrics show improvements of 3.3, 3.8, 4 percentage points, respectively. This method can achieve a detection speed of 0.37 seconds per sheet, meeting the real-time requirements of TEDS systems.