Semi-autonomous touching of underwater object by unmanned untethered vehicle

To investigate an underwater object in detail, it is essential for underwater vehicles to touch the object. However, for the Unmanned Untethered Vehicle (UUV) touching an underwater object is not an easy task because those robots are not apt to be operated remotely via acoustic link which is slow in communication rate and results in a long time-lag. In this paper, on the basis of time-lag compensation by stored video images, ranging technique by image processing and station keeping by visual feedback, a semi-autonomous system is proposed that enables the UUV to touch an underwater object by its hand from any direction. The proposed system is demonstrated experimentally through tank tests using testbed robot Tri-Dog 1 to which a two-degree-of-freedom robot hand is fitted.