Indian Mine Monitors Workers and Toxic Gases

By Dave Friedlos

Sept. 5, 2008—Indian startup company PervCom Consulting has developed a combined real-time location system (RTLS) and real-time sensing system (RTSS) able to simultaneously track persons and assets, as well as monitor environmental conditions. The combined system, PervTrack, utilizes battery-powered RFID tags, routers and sensors compliant with the IEEE 802.15.4 standard to create a wireless mesh network.

The Central Institute of Mining and Fuel Research (CIMFR) Dhanbad is currently piloting the system in the Bagdigi coal mine to monitor workers underground and in potentially dangerous environment conditions, while the Indian aluminum mining company Vedanta is trialing the system, minus the sensors, to track vehicles and other mobile assets.

CIMFR's deputy director, Laxmi Bandyopadhyay, says the institute received backing from India's Ministry of Information Technology to develop an underground tracking application. "It can be difficult to track miners underground, and we felt that RFID would give us the best solution," he explains. "So we approached PervCom to develop a mine-specific RFID system."

CIMFR and PervCom are devising the system together, with CIMFR providing the mining expertise and system requirements, while PervCom focuses on software and hardware. PervCom developed the PervTrack RTLS, which employs active RFID tags operating at 2.4 GHz, attached to miners' cap lamps. Six R-101 routers were then placed at strategic locations throughout the mine, forming a wireless mesh network compliant with the IEEE 802.15.4 standard, and two miners were issued tags to test the system.

The routers receive and forward data transmitted by WiTrak Tags, and serve as nodes in the wireless mesh network formed by other routers, tags and gateways within their vicinity. The location of the miner and tag is determined by the tag's position relative to the nearest router, which has a transmission range of up to 1.3 kilometers (0.8 miles). The tags also act as a communications device, with miners able to send pre-coded messages to a central station by pressing a button on the tag. In addition, they can receive alerts from remote monitoring stations.

It was then decided, Bandyopadhyay says, that the system could also monitor environmental data, including the detection of potentially poisonous gases, such as carbon dioxide or methane. PervCom developed the RTSS, in which the company's WiSense WiS-101 sensor-actuator nodes were embedded into PervCom's existing WiTrak WiT-101 RFID tags. The wireless nodes contain temperature, humidity and air-contaminant sensors capable of detecting smoke and fire, and of monitoring the air quality in buildings.

Information is transmitted in multi-hops to a remote monitoring station, where it is then transferred to bespoke PervTrack software. The data is sent at specified intervals to software that analyzes the information and automatically generates an alert if the measurements exceed specified levels.