Underwater Excavation by Excavation Robot Equipped with Propulsion Unit Based on Earthworm Setae

Soil discharging mechanism for seafloor drilling robot

“…To determine the target value of the fluidization for adjusting the flow rate, we find the excess pore water pressure ratio when the drilling torque is lower than the allowable limit and when the flow rate is as small as possible. As a drilling torque above 11.6 N m was previously shown to cause SEAVO II to enter a "propulsion impossible" mode 5 , an allowable limit of torque was set to 11.6 N m. The experimental method is the same as that in Section 4.1. We measure the drilling torque and the pore water pressure, and the experiment starts with the excavation unit being filled with drilled soil.…”

“…The excavation unit consists of a motor (RS-775GM504, Suzakugiken), discharging outlet, casing pipe, earth auger, and head part, as shown in Figure 4. The internal structure of propulsion unit, shown in Figure 5, consists of setae 5 , plates, a casing pipe, guide shafts, a pneumatic cylinder (CJ2B16-15Z, SMC), and a rubber tube. Currently, pneumatic actuators are used, but hydraulic actuators should be implemented before any deep-sea applications.…”

“…However, due to their susceptibility to earth pressure and inability to adequately discharge drilled soil, they could not excavate deep underground. To overcome these challenges, an underwater drilling robot, SEAVO II, was developed that was able to successfully drill 430 mm into the seabed 5 . Furthermore, drilling methods to reduce the drilling resistance have also been addressed 6,7 .…”

Soil Discharging Mechanism Utilizing Water Jetting to Improve Excavation Depth for Seabed Drilling Explorer

“…In our previous study, we developed a drilling robot named SEAVO that succeeded in excavating 613 mm at a turning radius of 1670 mm on land [26]. We also developed an underwater drilling robot named SEAVO II which successfully drilled 430 mm into the ground while underwater [27], [28]. Furthermore, we studied drilling methods to reduce the drilling resistance [29], [30].…”