The Industrial Internet of Things (IIoT), a concept that combines sensor networks and control systems, has been employed in several industries to improve productivity and safety. U.S. National Institute for Occupational Safety and Health (NIOSH) researchers are investigating IIoT applications to identify the challenges of and potential solutions for transferring IIoT from other industries to the mining industry. Specifically, NIOSH has reviewed existing sensors and communications network systems used in U.S. underground coal mines to determine whether they are capable of supporting IIoT systems. The results show that about 40 percent of the installed post-accident communication systems as of 2014 require minimal or no modification to support IIoT applications. NIOSH researchers also developed an IIoT monitoring and control prototype system using low-cost microcontroller Wi-Fi boards to detect a door opening on a refuge alternative, activate fans located inside the Pittsburgh Experimental Mine and actuate an alarm beacon on the surface. The results of this feasibility study can be used to explore IIoT applications in underground coal mines based on existing communication and tracking infrastructure.
The through-the-earth (TTE) wireless communication system, in which the RF signal can directly penetrate the earth separating a transmitter and receiver, is likely to survive a mine disaster because it requires no cabling between the surface and underground. One of the biggest challenges for TTE communication is that the ambient electromagnetic (EM) noise can be significant and impose a limitation on the reception sensitivity. Both underground and surface RF noise characteristics were obtained and analyzed from experimental data collected at several coal mines. The results show the surface has a higher noise level than underground. Moreover, the parameters obtained in an empirical noise model can be used to predict a TTE system's performance at a specific mine site.
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