Development and Motion Mechanism of a Novel Underwater Exploration Robot for Stratum Drilling

Abstract

As the exploitation of natural gas hydrates intensifies, there is a growing imperative to enhance the monitoring of extraction and storage areas. However, existing monitoring methods, such as seismic detection and seabed drilling technology, exhibit inherent limitations. These shortcomings primarily stem from challenges associated with conducting prolonged, in situ monitoring and the constrained scope of exploration. Addressing these shortcomings necessitates the development of innovative exploration methods or devices. This article introduces Stratloong, a novel underwater exploration robot designed specifically for drilling in seabed stratum. Comprising a drill bit, front and rear support units, and a propulsion unit, Stratloong emulates the peristaltic motion of an earthworm to achieve efficient drilling. In this research, kinematic and dynamic models of the robot are formulated, and a task-based control method based on inverse kinematic control is presented. In addition, a generic motion control framework is proposed to realize the drilling motion. Straight drilling tests are conducted in prepared seabed clay under different static settlement times to assess Stratloong's performance. Data collected include rotational speed, displacement, and axial force during motion. The robot maintained over 90% motion efficiency in the prepared seabed clay. Furthermore, outdoor tests confirmed the robot's ability to drill into soil without external thrust. The robot advanced 2230 mm with 89% motion efficiency. The comprehensive evaluation of Stratloong's drilling capabilities, conducted through a series of laboratory and field tests, yields valuable data and experiences for its potential application in seabed strata exploration.