2019 年 37 巻 4 号 p. 330-340
Seabed mineral resources were found on the bottom of the ocean. To utilize these resources, it is necessary to collect and analyze samples. Therefore, we intend to develop a seafloor robotic explorer that can excavate and sample the seafloor soil. In a previous study, we developed a drilling robot and experimentally demonstrated the ability of this robot to produce curved boreholes with a turning radius of 1,670[mm], and a depth of 613[mm] in land environment. However, an underwater excavation has not been successful. It is necessary to improve the gripping torque and to reduce the drilling resistance for underwater excavation. In this paper, we present a propulsion unit with the setae that imitates an earthworm's setae. As a result, the drilling robot succeeded in drilling into the ground while underwater. In addition, we aim to reduce the drilling resistance. We adjusted the penetration speed and the rotational speed of the drilling robot based on the drilling properties of underwater ground. We also consider the shape of the earth auger to reduce the drilling resistance. As a result, we succeeded in reducing the drilling resistance, which both lowered the excavation energy by 39.2% and reduced the completion time.