Invention of a path-following method for unmanned surface vehicle that includes wasted time and delay as control inputs

Yoshimura, Koki*; Morito, Makoto*; Tahara, Junichiro*; Baba, Shoichiro*; Sanada, Yukihisa   

We are researching and developing an unmanned surface vehicle (USV) to measure radiation contained in mud on the seafloor in the waters off Fukushima Prefecture. This is the area where radiation was released due to the accident at the Fukushima Daiichi Nuclear Power Station. We decided to use a USV to collect mud in this area. The USV was developed by JAMSTEC and has an overall length of 6 meters, an airborne weight of 4 tons, and a maximum speed of 4 knots. The hull has a moon pool from which a winch is used to lower the mud sampling equipment to the seafloor for mud sampling. In a previous study, a position maintaining control of this USV was realized by combining sliding mode control and corrective input by a neural network, and tested in actual environment. On the other hand, there is a problem that the condition of the seafloor in the survey area cannot be grasped for mud sampling in the real environment. This may cause the mud sampler to fall over if there is an obstacle or slope on the seafloor at the survey point. In addition, because the soil quality of the seafloor cannot be confirmed prior to mud sampling, it is not possible to efficiently collect data on different soil qualities. Therefore, seafloor mapping operations of the survey area using side scan sonar are necessary.