[Preprint] Dynamic Modeling, Gait Synthesis, and Control of a Novel Subsurface Bore Propagator

2026-07-01

AI Summary

This study addresses the challenge of anchoring and propulsion for underground robots in complex soil environments by proposing a five-module biomimetic robot inspired by earthworm locomotion and tunnel boring machines. Leveraging Euler–Lagrange dynamics modeling, modular decoupled design, and centralized finite-state-machine-based gait synthesis, the authors develop a sim-to-real control framework integrated with ROS and Unity physics simulation. The system successfully executed three complete gait cycles in real soil, achieving stable 30-mm forward progression and reliable anchoring without human intervention, thereby demonstrating the feasibility of autonomous subsurface burrowing.

Abstract

In this article, we present dynamic modeling, gait synthesis, and feedback control design for a modular novel subsurface robot, designed for human-free subsurface exploration and excavation. The subsurface propagator design is based on two major aspects: 1) anchor and propel movement like an earthworm and 2) excavation similar to tunnel boring machines. This design is decoupled into five separate modules: one drill head to excavate and create cavity for propagation, two modules to anchor the robot, and two modules to enable propagation of the body. In order to design a controller for each of the modules, dynamic models using the Euler-Lagrange framework are developed. These mathematical models are used as a baseline to design controlled decoupled operation of the different joint movements. The operation of robotic assembly is constructed via a centralized state machine for gait synthesis with integration of the designed feedback controller. The controllers are tested on the real robot geometry to aid sim-to-real integration: A physics-based Unity simulation using a CAD model of the robot and integration of the trained controller via ROS verifies the performance of the robot. The experimental results demonstrate that the proposed design, controllers and the gait synthesis strategy together are capable of anchoring the robot in place and creating an total advancement of 30\,mm into the soil after completing 3 gait cycles.

Problem

• subsurface exploration
• robotic excavation
• gait synthesis
• anchor-propel mechanism
• modular robot

Innovation

• subsurface robot
• gait synthesis
• Euler-Lagrange modeling
• modular excavation
• sim-to-real transfer