The state representing method for underwater remote controlled grab

Hydraulic grabs are used for removal of old facilities in Tokyo Bay of Japan. The grabs are capable of removing blocks of the facility without hitching by divers. However, the grab operators cannot observe the grab and the objects state in the water because of the muddiness. They require the divers' instruction whether the grab is placed in the correct position and the object is grasped in balanced condition or not. The operator must not operate the grab while divers confirm near the grab and must take enough evacuation time of the divers before operation. As a result, efficiency of the removing work by grabs is not so higher than that of conventional way. In order to improve efficiency of the grasping work by grabs, we have made a research on a remote controlled grasping system that is operated by one operator without divers. To accomplish this system, we have developed an experimental grasping system that composes a waterproof model of hydraulic grab, a control panel, and a VR (Virtual Reality) monitor. In this system, the posture of the grab is represented on VR monitor as a CGI (Computer Graphics Image). The position and the shape of the object is drawn by pre-measured data same as the conventional way. Dynamic motion of the grab is represented by combination with data of attitude sensor and numerical model of the grab. The model grab has contact sensors on each claw and slippage sensor mounted below the body. This paper describes the remotely controlled grab system that enables an operator to do grasping work in unclear environment, e.g., seawater is unclear, by providing visual information based on VR technology and sensors data