Recent advances of research on coal mine underground space positioning technology

China's coal-dominated energy structure determines that efficient mining of coal resources is crucial to national energy security, and intelligentization of coal mines is the only way for high-quality development of the coal industry. Underground space positioning technology is the foundation for realizing the intelligentization of coal mines. Accurate positioning information can be used to ensure the safety of miners, optimize mining operations, improve equipment utilization, and reduce operating costs. The unavailability of satellite navigation signals in mines, the enclosure and confined operation space, and the harsh electromagnetic and lighting conditions have put forward new requirements for positioning technology. This article focuses on the positioning problem in the special scenario of coal mines. Firstly, it systematically introduces four basic positioning technologies, including distance intersection, database matching, dead reckoning, and multi-source information fusion. Then, it provides a detailed review of the specific implementation schemes of these four positioning technologies, analyzes and summarizes the challenges faced by the underground positioning system in coal mines, such as the increase of error in absolute positioning, the difficulty in correcting the calculated positioning, the decrease in performance of multi-source fusion positioning method, and the lack of comprehensive standard guidance. Finally, the possible development direction of the positioning system is prospected. It can be considered to adopt multi-system collaboration to improve positioning ability, introduce brain-like bionic navigation to explore new positioning solutions, enhance seamless positioning and emergency positioning capabilities, and also consider the privacy protection of positioning system to improve system security.