NPU-BOLT: A Dataset for Bolt Object Detection in Natural Scene Images

TL;DR

This paper introduces NPU-BOLT, a new dataset of natural scene bolt images for object detection, addressing the gap between laboratory conditions and real-world scenarios to improve detection accuracy.

Contribution

The paper presents a publicly available dataset of 337 natural scene bolt images with diverse conditions, enabling better training and evaluation of bolt detection models in practical environments.

Findings

Dataset improves detection accuracy in real-world conditions

Models tested include YOLOv5, Faster-RCNN, CenterNet

Dataset validated with effective detection results

Abstract

Bolt joints are very common and important in engineering structures. Due to extreme service environment and load factors, bolts often get loose or even disengaged. To real-time or timely detect the loosed or disengaged bolts is an urgent need in practical engineering, which is critical to keep structural safety and service life. In recent years, many bolt loosening detection methods using deep learning and machine learning techniques have been proposed and are attracting more and more attention. However, most of these studies use bolt images captured in laboratory for deep leaning model training. The images are obtained in a well-controlled light, distance, and view angle conditions. Also, the bolted structures are well designed experimental structures with brand new bolts and the bolts are exposed without any shelter nearby. It is noted that in practical engineering, the above well controlled lab conditions are not easy realized and the real bolt images often have blur edges, oblique perspective, partial occlusion and indistinguishable colors etc., which make the trained models obtained in laboratory conditions loss their accuracy or fails. Therefore, the aim of this study is to develop a dataset named NPU-BOLT for bolt object detection in natural scene images and open it to researchers for public use and further development. In the first version of the dataset, it contains 337 samples of bolt joints images mainly in the natural environment, with image data sizes ranging from 400*400 to 6000*4000, totaling approximately 1275 bolt targets. The bolt targets are annotated into four categories named blur bolt, bolt head, bolt nut and bolt side. The dataset is tested with advanced object detection models including yolov5, Faster-RCNN and CenterNet. The effectiveness of the dataset is validated.