Design and Control of a Subsurface Untethered Burrowing Robot (SUBOT) for Deploying Exploration Sensors in Loose Sand Environments

Abstract This paper presents the development and evaluation of a fully autonomous, untethered robotic system—referred to as SUBOT—designed for deploying seismic exploration sensors beneath the surface of loose sandy environments. SUBOT introduces a four-legged screw-driven locomotion design, allowing it to drill vertically into the sand without external tethering or anchoring mechanisms. Each leg of the robot is independently actuated using high-torque rotary motors, providing the mechanical force necessary for vertical propulsion. The mechanical structure of the robot, including a square-frame motor support and a cross-shaped chassis formed by L-beams, was carefully engineered for structural integrity, torque distribution, and compactness. In addition to mechanical considerations, the robot integrates a dual PID-based feedback control system, utilizing an inertial measurement unit (IMU) to autonomously stabilize its orientation during burrowing. This control system mitigates tilt and ensures consistent vertical motion even in highly granular environments. Experimental testing in a controlled sandbox environment demonstrated the robot's ability to autonomously burrow to depths of up to 75 cm, self-level in response to pitch and roll disturbances, and ascending without human intervention. The results highlight the system's potential for improving subsurface seismic sensor deployment, offering an automated alternative to manual placement in land exploration and environmental monitoring applications.