Mining Contract: Demonstration of Inertial Sensor Tracking and Communication System

Contract Status & Impact

This contract is complete. To receive a copy of the final report, send a request to mining@cdc.gov.

The Mine Improvement and New Emergency Response Act (MINER Act) of 2006 mandated that all underground coal mines have a plan in place to install an emergency two-way wireless communication and electronic tracking system by June 2009. All electronic tracking systems as of September 30, 2010, approved by the Mine Safety and Health Administration (MSHA) were based on Radio Frequency Identification (RFID) technology. The accuracy of these systems can be highly dependent on the spacing of the readers (or the tags in a reverse RFID system) and the accuracy of their placement. Most of these systems have a location accuracy of 500-1,500 feet. Because most are not real-time (that is, they only transmit data when a tag passes close to a reader), the location data may be several minutes old at the time of an underground accident or event. To comply with the MINER Act and enhance the safety of mine workers, mining companies require a tracking system that is sufficiently accurate while being cost-effective, real- time, and a two-way communication system.

The research under this contract tested how well inertial measurement unit (IMU) technology performed in a beta test at a working coal mine. The tests involved tracking 12 belt-worn tracking units through a series of tunnels containing a network of 12 tracking system access points. Tests were designed to measure such variables as error rate of the system, durability of system components, and life of the rechargeable batteries used within the tracking units.

The principal electronic component in the tracking unit was an IMU based on micro-electro-mechanical-systems (MEMS) technology. The MEMS IMU continually sampled acceleration and rate of rotation of the miner wearing the tracking unit. Through signal processing of these quantities, an estimate of the position of the miner was generated within the tracking unit. The tracking unit then relayed this position estimate to the network of access points for display on the surface. The promise of the technology was that the position of the miner could be determined more accurately than if the tracking system were based on conventional Radio Frequency Identification (RFID) technology alone.

Based on the results of the field tests, the promises and expectations of the tracking system were not met. The noise and drift performance of the selected IMU was such that it did not appreciably increase the accuracy of the tested system over that of traditional RFID tracking system. It was determined that the noise and drift characteristics of reasonably priced IMU devices were insufficient for incorporation into miner tracking solutions at the time.