Although underwater robots, including inspection ROVs for maintenance purposes, are being researched and developed as effective tools, they are basically designed not to collide to objects. However, in the case of unpredictable disturbance including wave turbulence under piers and near structures and ship waves, underwater robots are difficult to manipulate, and so they might collide with structures and be damaged. This risk prevents their wider use.

In this study, we cladded the exterior of hovering-type underwater robots. We aimed to mitigate the maximum velocity of these robots accelerated by collision to enable them to continue to operate without breaking. With this goal, we investigated the impact mitigating effects of the cladding.

We cladded underwater robots with several exterior claddings including aluminum frames, measured the acceleration velocity acting on the robot bodies when they collided with concrete walls and steel pipes, and evaluated these measurements quantitatively.

We aimed to reduce the maximum acceleration velocity which occurs during collision by lengthening the time from collision to stopping, and proposed exterior claddings including a cladding shaped so as to make the robots' bodies rotate upon collision. In addition, the combined use of springs and dampers further reduced the maximum acceleration velocity.

We are going to investigate the effects on collided structures and efficient operation methods.