Development of underwater inspection system for dam inspection

Deteriorations of social infrastructures have been progresses in Japan. To prevent accident due to its failing, effective inspection system is needed. We have been developing underwater inspection system for dam inspection which is called Dam Inspection System (DIS). It is composed by Unmanned Surface Vehicle (USV), and Remotely Operated Vehicle (ROV). USV is called Surface water platform (SWP) and ROV is called Under Water Platform (UWP) in DIS. The SWP and the UWP are connected by underwater cable, the UWP is hanging from the SWP due to negative weight in water itself. Because of this, the DIS has following advantage compared to current system such as ROV: the inspection position by the UWP can be estimated without external device, operation is easy, and no thrusters blow up the sediment while ascent or descent of the UWP. The accurate positon data is necessary for periodical inspection to evaluate aged deterioration. It is obtained from the SWP´s positon and length of underwater cable while the DIS is stable in static water, but the DIS is moving, it is necessary to consider dynamics for precisely position estimation. The objective of this research is to reveal dynamic characteristic and to develop inspection position estimation method and position control method for the DIS. As the first step, we carried out the simulation using simplified model of the DIS and verification experiment. This paper report simplified model of the DIS and result of simulation and experiment. Both result indicate a DIS´s characteristic that the longer cable and the lighter weight of the UWP in water makes slowly the response of the UWP against the motion of the SWP. On the other hands, we obtained that it is necessary to improve dynamics model of the DIS, and to measure parameter of testbed in accurate, because of the simulation is not reproduce motion of verification experiment sufficiently.