Mining operations depend on current, accurate maps of the active mine and adjacent mine works to limit the risk of encroachment and breeching. Adjacent mines, however, may be decades or centuries old with missing, inaccurate, or ambiguous maps. Dangers such as flooding, roof-fall, rotten support timbers, and poor ventilation preclude human entry to survey these spaces. Remote mapping techniques such as ground penetrating radar and thermal imaging rely on geophysical models and assumptions to statistically infer the existence of underground voids. Only robots may enter and directly observe these otherwise inaccessible underground spaces, providing incontrovertible evidence of the mines existence and extent.
This paper presents a mobile robot, dubbed Groundhog, capable of navigating through and acquiring maps of abandoned mines. Groundhog addresses a number of common challenges in locomotion, communication and navigation. Coalmines are generally dark and damp, with low ceilings and miles of densely networked corridors. The surrounding geology is visually featureless and its density inhibits radio communication. Coal dust and gases such as methane and hydrogen sulfide can collect in pockets to form explosion hazards. Abandoned mines may be partially or completely inundated, and accumulate a treacherous layer of sulfurous sludge over time.