An unmanned underwater vehicle for long-distance water conveyance tunnel inspection

Long-distance inspection of water conveyance tunnels remains difficult because each measurement must retain an accurate position estimate over extended missions, thereby coupling sensing, navigation and motion control in ways that conventional modular inspection architectures do not readily resolve. Here we present a circumferential multibeam sonar (CMBS)-centric unmanned underwater vehicle system in which CMBS supports both tunnel profiling and marker-based absolute position correction. Marker-triggered Kalman updates reduce INS/DVL drift and improve positional accuracy under the designed marker-spacing conditions. Autonomous heading control maintains near-centreline motion for consistent profile acquisition, enabling successive cross-sectional profiles to be assembled into spatially co-registered tunnel geometric models. In controlled experiments, marker-based correction reduced positional error from ± 26.59 m in unaided dead reckoning to ± 0.22 m. Field deployments across three hydraulic infrastructure sites, including the South-to-North Water Diversion Project, demonstrate geometric measurement accuracy, stable operation and spatially consistent geometric modelling under in-service conditions. An unmanned underwater vehicle integrates circumferential multibeam sonar with marker-based navigation correction and autonomous heading control for in-service tunnel inspection. Marker-triggered calibration reduces long-distance positional drift and enables spatially consistent tunnel geometric models in controlled and field deployments.