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实验硬件和软件环境如表1所示。
Experiment platform Model parameters Operating system Ubuntu18.4 CPU I9-12900 KF 3.2 GHz GPU RTX2070 S 8 GB Graphics card 12 G Frame Pytorch Programming language Pyhton Table 1. Experimental platform parameter settings
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由于目前并没有导线的公开数据集,故文中建立了专用于红外图像架空导线检测的标签数据集。文中利用双光无人机,采集1000张红外架空导线图片,作为数据集的来源。图像尺寸统一修改为128×128,其中,将图像中的导线标记为wire,所有图片标签均通过Labelme软件自行标注,生成json文件,并用于训练,图7为训练样本的原始图像及标签图像。按照8∶2的比例对数据集和测试集进行划分,即800张用于训练,200张用于测试。
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为了验证文中构建的导线分割模型的性能,需选取合适的性能评价指标,在语义分割领中有多种评价精度的指标,文中选取均像素精度(Mean Pixel Accuracy,MPA)、平均交并比(Mean Intersection over Union,MIoU)这3个指标作为衡量模型分割精度的标准。其中MPA表示所有类别像素精度的均值,是语义分割领域中最普遍的指标之一,如公式(1)所示。MIoU表示的是真实值与预测值的交集比并集,如公式(2)所示。其中MPA侧重表现像素级的准确率,而MIoU更加侧重于表现模型计算分割区域的完整性以及分割位置的准确性。
式中:k表示类别总数;pij表示实际像素类别i,被预测为类别j的像素数量;pii表示实际像素类别为i,被预测为类别i的像素数量;k+1表示分割类别的数量,其中含有一个背景类。
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为说明该算法的有效性,文中先使用传统算法(Canny算子)对导线目标进行检测,进行实验对比,对30幅导线图的导线条数做了统计,人眼可看到的导线一共有132根,利用Canny算子一共检测到108根导线,检测率是81.8%,Canny算子能够检测到部分边缘,但是图像中还存在大量噪声,且会丢失部分导线信息,检测效果不佳。而后使用文中提出的算法,实验表明,该算法具有良好的检测效果。文中先使用原 Deeplabv3+的网络结构对导线目标进行检测,然后对 Deeplabv3+的特征提取主干网络ResNet50进行改进,引入注意力机制,再引入特征金字塔网络,再次进行实验,实验结果如表2所示。
Method MPA MIOU Deeplabv3+ 92.91% 86.79% Proposed algorithm 93.52% 87.83% Table 2. Experiment results metrics
3种检测算法的实验结果对比如图8所示,其中图(a)为原图;图(b)为Canny算子检测结果,从图中可以看出,Canny算子的检测存在大量噪声,且导线信息提取不完整,在道路这种具有热辐射的图像中,该算子会将道路误检为导线目标;图(c)为原 Deeplabv3+可以较好地提取到导线信息,但对于特别细小的导线目标提取不完整,这是因为原 Deeplabv3+算法在进行特征提取时,随着网络的加深,一些细小的导线目标会消失在最后一层特征图中,导致后续的网络无法检测到该目标;图(d)为文中的改进算法,结合了注意力机制及特征金字塔,改善了特征提取过程中,像素点少的细小的导线目标丢失的问题,能够完整地提取到导线信息,效果最好。
Infrared aerial image overhead wire identification algorithm based on improved Deeplabv3+
doi: 10.3788/IRLA20220112
- Received Date: 2022-04-10
- Rev Recd Date: 2022-05-25
- Publish Date: 2022-11-30
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Key words:
- Deeplabv3+ /
- feature pyramid /
- overhead wire /
- attention mechanism /
- ResNet50
Abstract: With the continuous expansion of the scale of the national grid, overhead conductors, as an important component of the power system, have become extremely important to its regular inspection. At the same time, with the opening of the low-altitude flight field, the identification of overhead conductors has also become extremely important to ensure the normal operation of the national grid and the safety of low-altitude flight. The method for identifying overhead wires in infrared aerial images was proposed using the Deeplabv3+ semantic segmentation network model, and the algorithm was improved according to the characteristics of infrared overhead wire image targets in this paper. Firstly, an attention mechanism was added to the feature extraction backbone network ResNet50 of the original Deeplabv3+ algorithm, so that the network highlights the characteristics of the area where the wire target was located, and paid more attention to the location of the wire target, thereby weakening the background and other non-main area features; Then, the encoder part of Deeplabv3+ was improved, and the Feature Pyramid Networks (FPN) was added to the ResNet50 model, which can fuse the shallow and deep features, enhance the network's ability to identify the attributes of targets of different sizes, and the performance of small targets such as wires, and then improve the overall recognition effect of the network. The experimental results show that the improved algorithm has good detection performance, the average pixel accuracy is 93.52%, and the average intersection ratio is 87.83%.