Autonomous Multimodal System for Intelligent Railway Inspection

We propose an autonomous aerial inspection system to address growing safety concerns of railway infrastructure degradation. Unlike conventional labor- and sensor-intensive methods, our quadrotor integrates a depth camera, monocular inspection camera, Global Positioning System (GPS) module, and onboard computing unit. Combining visual-inertial fusion with GPS, it achieves robust localization even in GPS-denied environments. A lightweight deep learning model built on You Only Look Once v12 (YOLOv12) enables real-time detection of key components such as spikes and clips. To enhance autonomy, we introduce Railway Autonomous Navigation Guided by Embedded Recognition (RANGER), a novel algorithm that reconstructs 3D world coordinates from 2D detections using only onboard sensing, without requiring prior global maps. By fusing detection with localization data, RANGER enables precise track following and stable altitude control in complex or GPS-denied conditions. This reduces hardware demand while ensuring accurate navigation. Our system reduces operational costs, enhances scalability, and enables accurate, real-time inspections in complex, unstructured environments.