DWPIS: Dynamic-Weight Parallel Instance and Skeleton Network for Railway Centerline Detection

The primary premise of autonomous railway inspection using unmanned aerial vehicles is achieving autonomous flight along the railway. In our previous work, fitted centerline-based unmanned aerial vehicle (UAV) navigation is proven to be an effective method to guide UAV autonomous flying. However, the empirical parameters utilized in the fitting procedure lacked a theoretical basis and the fitted curves were also not coherent nor smooth. To address these problems, this paper proposes a skeleton detection method, called the dynamic-weight parallel instance and skeleton network, to directly extract the centerlines that can be viewed as skeletons. This multi-task branch network for skeleton detection and instance segmentation can be trained end to end. Our method reformulates a fused loss function with dynamic weights to control the dominant branch. During training, the sum of the weights always remains constant and the branch with a higher weight changes from instance to skeleton gradually. Experiments show that our model yields 93.98% mean average precision (mAP) for instance segmentation, a 51.9% F-measure score (F-score) for skeleton detection, and 60.32% weighted mean metrics for the entire network based on our own railway skeleton and instance dataset which comprises 3235 labeled overhead-view images taken in various environments. Our method can achieve more accurate railway skeletons and is useful to guide the autonomous flight of a UAV in railway inspection.