Mining, Metallurgy & Exploration (2019) 36:541–545, https://doi.org/10.1007/s42461-019-0054-x
Electromagnetic-based proximity detection systems (PDSs) are used on mining machinery to protect workers from being pinned or struck. These systems generate magnetic fields covering the space around a machine, and a miner-wearable component (MWC) detects the field. The PDS determines the distance of miners relative to the machine based on the detected magnetic flux density in the magnetic field. This information is used to establish warning and shutdown zones around the machine. Maintaining a stable magnetic field is essential for system accuracy. However, components used to generate magnetic fields can be influenced by temperature changes. Depending on ventilation conditions and seasonal alternation, a PDS can be subject to significant temperature fluctuation. To better understand and quantify this phenomenon, researchers from the U.S. National Institute for Occupational Safety and Health (NIOSH) developed an experimental apparatus to study the influence of temperature on magnetic field generator circuits used in PDSs. Results from the study show that the electric current through a generator can be influenced by both ambient and internal temperatures, modifying the magnetic field that is produced. These findings show that temperature can significantly influence the ability of PDSs used in underground coal mines to accurately determine a worker’s position in relation to a mining machine. The study also presents methods to overcome the effects of changing temperatures in the form of an automated feedback control system used to stabilize generator currents.