Prior Semantic Costmap-Based Differentiated Safety Inflation Scheme for Substation Inspection Robot Navigation Enhancement

The traditional dynamic window approach (DWA) cannot perceive semantic risk levels in substation environments. We propose a lightweight semantic navigation scheme that takes a prior semantic map as input, applies differentiated safety inflation to semantic regions according to category (danger zones dsafety × 1.5, secondary forbidden zones dsafety × 0.5), and fuses them into the Nav2 costmap via per-cell maximum fusion. The standard DWA thereby gains hierarchical avoidance capability at the costmap representation level, without modifying the DWA planner core. Gazebo simulations were performed with 80 runs per group, each collected under an independent simulation restart. Compared with the conventional baseline, the proposed scheme increases the minimum clearance from the robot silhouette to the physical equipment boundaries from 0.42 m to 0.66 m and the minimum signed clearance to the boundary of the pure semantic forbidden zone—a physically empty region marked only in the semantic layer—from −0.36 m (penetration in every run) to +0.46 m. Center-point entries into semantic forbidden zones are reduced to zero (80/80 → 0/80), at the cost of an 11.8% increase in path length. Statistical significance is confirmed by Welch’s t-tests with Holm–Bonferroni adjustment and by non-parametric Mann–Whitney U tests. Comparison with the Nav2 native KeepoutFilter shows that hard boundaries without soft buffering degrade DWA traversability: the right-angle expanded mask failed in all 50 attempts, and the rounded expanded mask succeeded in only 48% (24/50), whereas the proposed scheme maintained 100% (80/80). Ablation, noise, and offset–delay experiments with 30 runs per condition further validate the robustness of the scheme. In the exploratory new-start-point comparison (n = 10 per group), differentiated inflation matched uniform large inflation at the highest-risk device (0.764 m vs. 0.771 m) while keeping the path 2.6% shorter. The proposed scheme provides a loosely coupled, easily deployable semantic navigation safety enhancement for substation inspection robots.