Development and application of the soft collision-protection structure for dam inspection underwater vehicle

Operations in the upstream reservoir pose significant challenges for remotely operated vehicles (ROV) due to deep water with poor water quality, complex changes in flow state during the dam inspection tasks. Although the rigid frames and buoyancy shells can support underwater vehicles, the collision risk often results in structural damage and information loss for ROV. Hence, a novel type of quick-disconnected soft collision-protection structure is proposed, which safeguards the body devices, with the merits of lightweight, limited size, soft material in elastic deformation to absorb energy self-adaptively and assembly into groups for customization. To achieve high collision protection performance, the mechanical behavior of the Component model is numerically investigated, and the experimental equipment is set up for underwater collision. The findings indicate that TPU material shell filled with H250 PU foam presents superior collision protection properties. Component 1 is identified as optimal for the main body, where structural dimension extension from Component 1 to Component 3 yields a 15.9% peak contact force reduction but 27.3% SEA value decrease. In addition, elastic deformation-based energy absorption mechanisms enable single soft protection structure to safeguard ROV under 0.5 m/s-velocity collisions with 100 kg-counterweight self-adaptively. While higher-speed collisions exhibit a 34.8% prolonged peak force occurrence compared to lower-speed cases. Eight soft collision-protection units are matched to a bionic protection group for the dam inspection underwater vehicle, with a verification in the field water cushion pool. This work presents an effective solution for dam inspection underwater vehicle collision protection on soft materials in group assembly.