To extend AUV exploration ranges in the Arctic, this study presents a pneumatically driven peristaltic sea ice drilling robot that deploys communication relays through boreholes. The robot utilizes an earthworm-inspired mechanism to propel itself while excavating, which is essential for navigating variable borehole diameters caused by fluctuating ice hardness. Experiments in tapered acrylic pipes confirmed successful propulsion over 530 ㎜ under changing diameters. Additionally, a pneumatic flow-based estimation method achieved borehole diameter accuracy within 5%. These results validate the robot's adaptability and demonstrate the feasibility of integrating real-time diameter estimation for stable, autonomous under-ice operations.
