A Field-Validated GNSS-Assisted Quadruped Robotic System for Remote Multi-Waypoint Radiation Inspection

Remote robotic radiation inspection can reduce personnel exposure during nuclear-facility operation, radioactive-source management, decommissioning, and emergency response. However, repeated multi-waypoint missions remain difficult when pre-registered inspection locations must be revisited under conventional global navigation satellite system (GNSS) and human teleoperation. GNSS fluctuations, discrete updates, communication delay, continued robot motion, and operator response can affect final approach, stable waypoint confirmation, and repeatable task execution. To address these issues, we developed a field-validated GNSS-assisted quadruped robotic system integrating long-range teleoperation, onboard video, waypoint management, radiation sensing, distance-dependent translational assistance, and structured mission logging. Waypoint confirmation combines a 4 m entry radius, a 5 m exit radius, continuous dwell, and GNSS quality gating, while the operator retains control over direction, obstacle avoidance, rotation, and the physical stopping location. Evaluation included static GNSS characterization, state-machine boundary tests, three paired ON/OFF field comparisons, four complete eight-waypoint missions, a five-distance communication-link test, and offline replay of 27 parameter combinations. Assistance reduced mean GNSS-reported confirmation distance by 1.569, 0.460, and 0.485 m in the three comparisons, and eliminated the pre-confirmation distance resets observed in the corresponding OFF runs. All four Site B missions completed eight of eight waypoints; checkpoint-based recovery supported interrupted tasks. Supplementary ICMP measurements quantified network RTT and packet loss at tested separations of approximately 100–800 m. These results show that the proposed workflow can support repeated remote radiation inspection with conventional GNSS.