10.Research on Unmanned Underwater Construction and Survey

Background and Objectives

The major part of underwater construction work in ports and at airports is currently implemented by divers’ manual labor. In contrast to onshore work, visual information is mostly limited due to unclear seawater or muddiness caused by the construction work itself. In addition, impact from waves and tidal currents significantly constrains the safety and efficiency of under water operations. The aging and shortage of divers in the future is also of significant concern in the light of the decreasing younger working population, which is threatening the underwater construction work industry. Since April 2007 when the Basic Act on Ocean Policy was enacted, public interest in marine issues has increased. The marine activities of oil recovery as environmental improvement,
development and maintenance of shipping channels, and of mooring GPS-mounted buoys have been nationally applied. The ocean surrounding Japan, however, is a deepwater and large-wave area, so that manned operations in this area are limited.
Considering the recent severe fiscal situation and the appropriate maintenance of deteriorated port structures, repair work is expected to increase. The development of unmanned technologies for underwater operations is essential following the enactment of Basic Act on Ocean Policy.

Research topics

We have been developing non-contact thickness measurement techniques, which do not require removing the marine organisms attached to the structures, for performing indispensable measurement of board thickness to examine deterioration in steel structures in port areas.
We will also develop unmanned examination systems for mooring devices for GPS-mounted buoys set at a depth of around 200 meters.
Development of chain-net recovery equipment, which enables safe recovery of wave-dissipating blocks from under the sea without any divers, is expected to be conducted.
We will achieve multifunctional safe underwater operations by developing operation manipulators based on the system innovated over the past years for underwater backhoe manipulator techniques.

Activities in FY 2010 

Based on the results of studies conducted up until the previous fiscal year, we know how to apply chain-net recovery equipment to the relocation of large-size blocks that exceed 50 tons.
We solicited private sectors for joint research of noncontact measuring equipment for steel structures that utilizes ultrasonic waves to allow such equipment to be highly applicable to sites and to be more practical. We started joint study on developing tools that are applicable to various structures and investigating guidelines for handling obtained data to be utilized for structure maintenance and management.
Examination systems for mooring devices for GPSmounted buoys were used for actual work procedure examinations in the sea off the coast of Kamaishi, Iwate Prefecture. Through the actual experiments, the effectiveness in the sea was evaluated and verified.
Regarding the remote control system for underwater backhoes, two of our researchers visited South Korea to lecture about the achievements of the study at the Korea Ocean Research and Development Institute (KORDI) as well as to exchange opinions with local researchers. After that, Korean researchers visited Japan to conduct further opinion exchange.