A lightweight road crack detection algorithm based on improved YOLOv7 model

Road crack detection plays a crucial role in protecting road safety. However, early manual detection is not only time-consuming and laborious but also highly inefficient. Although existing road inspection vehicles have powerful functions and precise detection, their high cost makes them not universally applicable. Besides, existing object detection algorithms have high computational costs, but the computing power of edge devices is often limited, making it difficult to deploy detection algorithms on edge devices. To this end, we propose a lightweight and efficient road crack detection algorithm, YOLOv7 BiFPN-G, based on YOLOv7. In response to the shortcomings of PANet in feature fusion in the original YOLOv7, we introduce the BiFPN structure to construct a better backbone feature extraction network. It achieves a higher level of feature fusion through different weights. To reduce the number of parameters, we introduce a lightweight Ghost convolution instead of the standard convolution, which continuously compresses the number of parameters through depthwise separable convolution. Then, we reduce the channel width and depth training parameters to further reduce the number of parameters and use knowledge distillation to improve the performance of the reduced model. Finally, we developed a road crack detection system based on the obtained model, which is mobile-friendly, inexpensive, and universal. We conduct visual experiments to compare the detection performance of multiple algorithms in various complex road environments. Compared with YOLOv7, YOLOv7 BiFPN-G is more lightweight, with only 7.4M parameters and a model size of only 14.MB, while there is no significant degradation in model accuracy. Compared with lightweight models YOLOv5-s and YOLOv7-tiny, YOLOv7-BiFPN-G shows leading performance in average accuracy, recall, and accuracy. The experimental results demonstrate that YOLOv7-BiFPN-G has good performance in normal road environments.