BANDYOPADHYAY et al: WIRELESS INFORMATION AND SAFETY SYSTEM FOR MINES 107Journal of Scientific & Industrial Research

Vol. 68, February 2009, pp.107-117

*Author for correspondence

Telefax: 0326-2296045, E-mail: laxmikb@yahoo.com

Wireless information and safety system for mines

L K Bandyopadhyay1*, S K Chaulya1, P K Mishra1, A Choure1 and B M Baveja2

1Central Institute of Mining and Fuel Research (CIMFR), Dhanbad 826 001, India

2Department of Information Technology, Ministry of Communication and Information Technology,

New Delhi 110 003, India

Received 16 May 2008; revised 21 November 2008; accepted 25 November 2008

This study presents a wireless information and safety system for mines developed by CIMFR, Dhanbad. System consists

of hardware devices and application software. Hardware module is ZigBee-compliant active radio frequency identification

(RFID) devices/ transceivers, which can be programmed to act as end device (tag), router or coordinator that enables them to

form an IEEE 802.15.4-based mesh network. It uses a unified wireless mesh-networking infrastructure to locate, trace and

manage mobile assets and people as well as monitor different environmental conditions using sensors. Another core module is

wireless sensor network (WSN) software, which is developed for tracking of underground miners and moveable equipment by

wireless sensor networking in mines. Software is especially designed for tracking of miners and vehicles, route tracking in

opencast mines, preventing fatal accidents and vehicle collisions, environmental monitoring, observing miners’ unsafe practice,

sending alert message, and preparing computerized miners’ duty hours record.

Keywords: Mining, Tracking and monitoring, Wireless sensor network, ZigBee devices

Introduction

In case of disaster in an underground mine, it is very

difficult for mine management to identify actual person

trapped, their number and exact location. Therefore,

identification and coding of miners is a vital need for

underground mine management in case of disaster as

well as normal operating conditions. Mining industry

is generally capital intensive; cost of maintenance (35%

of operating cost of system) at mechanized mines goes

as high as 50-60% when both direct and indirect costs

are taken into account1. Sometimes, it constitutes 30%

of total production cost. In today’s globally competitive

market scenario, efforts to reduce production cost have

awaken mining industry for automation and optimum

utilization of equipment by increasing its availability

and performance2,3. This study presents a wireless

information & safety system for mines (WISSM),

developed by CIMFR, Dhanbad.

Wireless Information & Safety System for Mines

(WISSM)

Core system component, ZigBee-compliant active

RFID device, can be programmed to act as tag (end

device), router or coordinator (Fig. 1) that enables them

to form an IEEE 802.15.4-based mesh network4. It uses a

unified wireless mesh-networking infrastructure to locate,

trace and manage mobile assets and people as well as

monitor different environmental conditions using

sensors5-7. ZigBee devices have numerous advantages8-11

as follows: i) unlicensed 2.4 GHz industrial, scientific

and medical (ISM) band; ii) ultra low power (ideal for

battery operated system) requirement; iii) operates for

years on inexpensive batteries; iv) large number of nodes/

sensors; v) reliable and secure links between network

nodes; vi) easy deployment and configuration; vii) low

cost system; viii) very fast transition time; ix) digital

battery monitor facility; and x) smaller in size (system

on chip).

In ZigBee transceiver (Fig. 2), incoming 2.4 GHz RF

signal is picked up by antenna (1) and pass to low noise

filter (2) through duplexer. Low noise filter (2) eliminates

DC offset and noise problem, and amplifies radio

frequency (RF) signal from antenna to a suitable level

before feeding to down–conversion mixer (3), which

mixes amplified signal with a high frequency signal

generated by local oscillator (4). Output of down-

conversion mixer (3) is then fed to a band pass filter (5),

and signal thus obtained is down converted in quardrature

108 J SCI IND RES VOL 68 FEBRUARY 2009

to 2 MHz intermediate frequency (IF). Down-conversion

mixer (3) converts received RF frequency to IF, which

is filtered and amplified by a band pass filter (5), and

then auto-tuned by phase locked loop. Output of band

pass filter (5) is fed to amplifier (6), which controls over

gain by inbuilt automatic gain control (AGC). Automatic

frequency control (AFC) of amplifier (6) controls

frequency of local oscillator (4), which is also inbuilt in

amplifier (6). AGC output is sampled with 4 MHz

sampling rate at analog to digital converter (7) for further

digitization. The digitized signal is fed to digital

demodulator (8), where channel filtering and

demodulation are performed in digital domain. Signal

obtained from digital demodulator (8) is an efficient

digitized actual signal containing data, which is fed to

radio data interface (9) and control logic (10). Radio data

interface (9) interfaces signal to microcontroller unit (11).

Control logic (10) controls signal of digital demodulator

(8) and digital modulator (12). Transmission of IF signal

coming from radio data interface (9) is modulated by

digital modulator (12), and fed to digital to analog

converter (13) for conversion of digital signal. Output

of digital to analog converter (13) is fed to low pass filter

(14), where signal is filtered and again pass it to up-

conversion mixer (15), which up converts filtered signal

directly to RF by a single sideband modulator using

local oscillator (4). The up-conversion mixer (15) is

designed for low-voltage operation and is ideal for use

in portable consumer equipment. Up conversion mixer

(15) operates with IF input frequencies (40-500 MHz),

and up converts to output frequencies as high as 2.5

GHz. Output of up-conversion mixer (15) is then fed to

power amplifier (16), which power up the signal.

Powered up signal is then passed to antenna (1) through

duplexer, which combines two or more signals onto a

common channel or medium to increase its transmission

efficiency. It allows a transmitter to operate on one

frequency and a receiver on a different frequency to

share one common antenna with minimum interaction

and degradation of different RF signals. Then, RF signal

transmits to antenna (1) for transmission.

Specifications of ZigBee devices are: i) high

performance low power 8051 Microcontroller core; ii)

operating voltage, 2-3.6 V; iii) operating ambient

temperature,– 40°C to 85°C; iv) frequency band, 2.4

GHz ISM; v) current consumption in microcontroller

Fig. 1—ZigBee devices (end device, router and coordinator)

BANDYOPADHYAY et al: WIRELESS INFORMATION AND SAFETY SYSTEM FOR MINES 109

active receiving mode is 26.7 mA and transmitting mode

is 26.9 mA; vi) system clock frequency, 32 MHz; vii)

time delay, 10 ns; viii) radio bit rate, 250 kbps; ix) flash

memory, 128 kb; and x) receiver sensitivity, –92 dBm.

Principle and Operating Procedure

Tracking and Monitoring System

With the help of proposed tracking and monitoring

system, it will be easier to locate each miner and

equipment during disaster situation as well as during

normal working periods for productivity measurement

and employees’ safety. This will improve output per man

shift (OMS) as well as improve safety of miners. This

will also reduce idle time of equipment operating without

going physically inside underground mine. Core

hardware components of tracking and monitoring system

are active RFID devices attached to mobile workers,

vehicles and equipment in mining and tunnel operations.

Each device transmits/receives messages to/from

neighboring devices having ZigBee-compliant network

interfaces and autonomously form network among

themselves and with other static devices (routers) placed

at strategic locations. The location of tagged personnel/

equipment/ vehicles is determined in terms of those static

routers. Each device communicates data in multihop to

a remote computer at a control station in pit top.

Reduction in Fatal Accident

By implementing miner safety application, risk of

fatal accidents will be greatly reduced. This will also

reduce loss of life, financial loss of mine as well as

machine downtime.

RFID reader device is installed inside cabs of mine

vehicles. Ultra long range (ULR) RFID tags worn by

miners are seen by reader units, and transmission signal

triggers a light inside cab to warn driver to reduce his

speed drastically. Reader unit consists of an RFID reader,

a Wiegand interface card, latch relay, reset switch and a

flashing strobe, all housed in a PVC box and is placed

inside vehicle cab. A quarter wavelength whip antenna

is mag-mounted to the roof of cab and cabled to reader.

Power is supplied from standard battery of vehicle. All

miners wear an RFID tag and when reader sees tag,

transmission signal trigger flashing strobe. Once pilot

slowed down and passed miner(s) safely, he pushes reset

button to stop flashing strobe.

Collision Prevention System

In mechanized mine environment, locos (vehicles

transporting coal/mineral) may collide with each other,

resulting often in serious injuries to drivers and

sometimes loss of lives. For mines, this in turn also leads

to downtime and lost productivity. By installing RFID

Fig. 2—Block diagram of ZigBee transceiver

110 J SCI IND RES VOL 68 FEBRUARY 2009

collision prevention system, risk of accidents and

machine downtime will be greatly reduced and

productivity improved. In ZigBee -compliant RFID

collision prevention system, each loco is fitted with two

asset tags (one each at front and back) and an RFID

reader unit, consisting of an ULR RFID reader, a

Wiegand interface, antenna, and a timer relay. Reader

unit is interfaced with loco controller to control speed

(average, 40 km/h). When reader detects an asset tag

signal from another loco in the vicinity at a range of

approx 50 m, power supply from power supply unit

(PSU) to controller is reduced (50%), thus automatically

reducing speed, at which loco is traveling. This in itself

is also a warning to loco driver that another loco is

approaching or in the same area. When RFID tag is no

longer seen by reader, power supply is automatically

increased (100%) and activates controller to run at full

speed again.

Efficiency and Productivity Monitoring System

RFID technology and devices can be used effectively

for monitoring and measuring productivity through an

application that allows for identification of location and

tracking of movement of a mine’s fleet. By using this

automatic (and accurate) means of collecting data over

a period of time, it is possible to determine how

efficiently and productively mine site is being managed.

It is also an indication of whether mines assets (fleet)

are managed cost-effectively. In other words, to optimize

productivity and asset management, mine management

may decide that it needs to either increase or decrease

number of vehicles and/or number of hours worked per

shift. Costs can also be calculated more accurately and

measured against productivity of a particular mine site.

This will also improve OMS, which leads to efficient

productivity.

At an opencast mine, each vehicle is fitted with a Data

Collection RFID unit consisting of: a) RFID reader; b)

tag buffer; c) 24 V to 12 V step-down converter; d) 9-

pin RS-232 serial connector; and e) antenna. RFID tags

are mounted at specific locations around mine site to

mark routes followed by vehicles. When a vehicle fitted

with data collection unit moves past a ‘route marker’,

first and last transmission from tag is recorded in

database of the unit. Data is downloaded and analyzed

to determine each vehicle route. As all records are time

stamped, it is also possible to determine time taken for

each vehicle to complete the route. At present system

based on GPS technology12,13 is popular for tracking and

monitoring of vehicles in opencast mines. But it is costly

and not specifically developed for opencast mine

applications like analysis of shovel-dumper performance.

Even application software of developed technologies is

different from GPS system, which specifically

incorporates module for optimizing shovel-dumper

performance.

Monitoring Miners’ Unsafe Practice and Warning System

Generally, underground miners are unknowingly

going to the danger area, like, unsupported area where

chances of roof fall are frequent, near blasting area,

gaseous area etc. These unsafe practices cause several

accidents in underground mine. Therefore, a continuous

monitoring and warning system must be implemented

in the underground mines to avoid such common

accidents. People working in the underground mine will

be safe and an audio-visual warning will be provided

while particular miner entering in an unsafe area. Thus

frequent accidents will be minimized.

Miners are continuously tracked using RFID tags

provided to each worker. Unsafe practice of concerned

person is analyzed by computerized software, and based

on the information, mine management gives warning to

defaulter. Further, an audio-visual warning system is

incorporated in each tag to automatically warn particular

miner entering into unsafe areas.

Software

WSN software (Fig. 3) was developed in Visual Basic

(VB) under windows as front-end tool and SQL-Server

as back end support. VB is an object oriented based

software package; therefore, various objects available

in VB are used. Moreover, few functions and classes

are designed in VB to integrate software. For reporting

very powerful and extensive software, Crystal Report is

used.

Modules

Software is especially designed for different purposes

in mines and has following modules:

Tracking of Miners and Vehicle

This module allows continuously tracking miners’ and

mining equipment inside an underground mine in real-

time. Locations of miners are detected for each router

and a complete miner path chart is drawn. Software keeps

record of time when respective miner is going inside

mine and coming back. It also helps mine management

to keep record of attendance. Ultimately, this module

helps in preparing computerized reporting on actual duty

hours of each miner.

BANDYOPADHYAY et al: WIRELESS INFORMATION AND SAFETY SYSTEM FOR MINES 111

Fig. 3—WSN software layout

112 J SCI IND RES VOL 68 FEBRUARY 2009

Route Tracking in Opencast Mines

This module allows tracking a dumper movement in

opencast mine. Locations of dumper are detected for

each router and a complete dumpers path chart is drawn.

Software keeps record of time when respective vehicle

is going inside mine and coming back. It also helps mine

management to keep record of duration of time.

Ultimately, this module helps in preparing computerized

reporting on actual duty hours of each dumper. This

module can also be used for optimizing shovel-dumper

performance and deploying optimum number of dumpers

for a particular opencast mine.

Preventing Fatal Accidents

This module allows preventing fatal accident in

underground mine by transmitting warning signal to

miners and loco drivers. Software detects position and

path of miner and moving loco, and automatically warns

miner and loco driver when miner and loco are

approaching nearer in same path.

Preventing Vehicle Collisions

This module allows monitoring locos’ position inside

an underground mine and transmitting warning signal

to vehicle drivers approaching nearer. Software detects

position and path of moving vehicle to/fro then

automatically warns driver after sensing vehicle reader

tag, if both vehicles are in same path and approaching

nearer.

Environmental Monitoring

This module allows wirelessly monitoring mine’s

environmental conditions using appropriate sensors.

Software automatically collects data through coordinator

of a router to which a sensor is coupled. On-line

environmental data and graph can be seen on monitor.

System gives warning when concentration of a particular

gas reaches its permissible limit.

Monitoring Miners’ Unsafe Practice

This module monitors miners’ unsafe practices and

generates warning. System automatically detects router,

which is placed in unsafe area. When any miner

approaches near unsafe area router, then system warns

the particular miner by audio-visual alarm and system

automatically starts beeping at surface computer. This

can help in ensuring miners safety and generates a log

file for keeping record with a particular date and time.

Sending Alert Message

This module generates alarm messages on user-

defined conditions. Different coded messages can also

be sent to respective miner as and when required.

Operating Mode

Software operates on-line and off-line. In on-line

(real-time) mode, CPU is connected to coordinator by a

serial port, and read periodic tag’s data through various

routers by multi-hoping technique. Coordinator receives

signal from different routers, which are placed in

strategic locations. Active RFID devices are attached to

underground miners. Each device can transmit/receive

signal to/from neighbouring devices. Devices with

ZigBee-complaint network interfaces can autonomously

form network among themselves and with other static

devices. The locations of tagged personnel are displayed

numerically or graphically on the system and data is

automatically saved in a database file. In this mode of

operation, location of miner is detected for each router

and draws a complete miner path chart as per request.

Software keeps record of time when respective miner is

going inside mine and coming back. It also helps mine

management to keep record of attendance. Ultimately,

this software helps in preparing computerized reporting

on actual duty hours of each miner.

In off-line mode, one can display stored data by simply

selecting file of required date. Graphical location of

particular miner can also be displayed on screen. In both

operating modes, software supports hard copy printing

of data (numerical or graphical as desired).

Administrator can change software configurations, like

working area of mine plan, unit of scale, router locations,

router status and different essential parameters. Enough

security has been maintained using password.

Requirement

Minimum requirements for running WSN software

are: i) hardware requirements include CPU – Pentium

IV, HDD – 40 GB (free), RAM – 512 MB, colour monitor

resolution – 1024 × 768, 32 bit colour quality, one free

serial communication port, and serial data cable; and ii)

software requirements include operating system –

Windows NT/XP/2000/2003, SQL server 2000, and

Crystal Report 8.5.

System Installation Procedure

Installation procedures for underground mine with

shaft entrance and with incline entrance (Fig. 4) and

opencast mine (Fig 5) are depicted. ZigBee transceivers/

BANDYOPADHYAY et al: WIRELESS INFORMATION AND SAFETY SYSTEM FOR MINES 113

PC1 C1

R1

R8 R9 R2 R5 R6 R7

R12 R11

R4

R3

R14 R13

R15 R16 R17 R18 R19

E1 E2

E3

E6 E7 E8

E9

E5 E4

R10

U1

S1

CR1

SH

G1

G2

G3

C2 PC2

R27

R28

R29

R23

R24

R25

R26

R33 R34 R31 R32 R30

E10

E12 E13 E11

R21 R22 S2

U2

CR2

R20

I 1 I 2

G4

A)

Fig. 4—Layout of ZigBee devices in an underground mine having: A) shaft entrance; and B) Incline entrance

B)

devices (end devices, routers and coordinator) are housed

in hard and tough structure to sustain tough mining

conditions. Coordinator (C) is connected with computer

(PC) to using RS232 cable in surface control room.

Routers (R) are hanged in pole in surface or hanged from

roof /side of shaft (SH)/ incline (I)/ gallery (G) so that it

should not obstruct movement of man and machinery.

Distance between two routers (R) may vary (40-80 m)

in straight gallery (G)/ road (TR)/ shaft (SH)/ incline

(I), where line-of-sight range is more. In case of small

and labyrinth gallery (G), distance between routers (R)

should be kept at lesser distance so that line-of-sight

114 J SCI IND RES VOL 68 FEBRUARY 2009

distance is maintained among routers (R), which should

be placed in such a way that in case of disaster in a

particular portion of mine, communication can be

established by alternative routes automatically.

Following above guidelines, routers (R) are placed on

required portion of mine, where monitoring and tracking

of miners and moveable equipment are needed. These

routers (R) form wireless network with coordinator (C).

Required environmental monitoring sensors are attached

to particular routers, where gas monitoring is essential.

End devices (E) are assigned to miners and moveable

equipment. End devices (E) transmit signal to respective

routers (R), which receives signal and transmit to next

routers (R) and subsequently data is transmitted to

coordinator (C) through intermediate routers by multi-

hop transmission mechanism. Finally, coordinator (C)

sends data to computer (PC). Same data is processed,

analyzed and stored in computer (PC) using WSN

software, which controls and commands all operations

performed by total network.

Wireless sensor network (Fig. 4A) in an underground

mine having shaft entrance consists of a personnel

computer (PC1), coordinator (C1), router (R1 to R19)

and end devices (E1 to E9). PC1 is connected to C1

using RS232 cable in surface (S1) control room (CR1).

Routers (R1 to R4) are wirelessly connected with C1 at

a distance 60 m apart in an underground (U1) shaft (SH).

Routers (R5 to R7) placed in left and routers (R8 to R9)

placed in right side of first galley (G1), at 50 m apart are

wirelessly connected to router R2. End devices (E1 and

E2) attached with miners/moveable equipment are

wirelessly communicated with routers R6 and R9

respectively. Routers (R10 to R12) placed in left and

routers (R13 to R14) placed in right side of second galley

(G2), are wirelessly connected to router R3. End devices

(E3, E4 and E5) attached with miners/moveable

equipment is wirelessly communicated with routers R12,

R13 and R14, respectively. Routers (R15 to R17) placed

in left and routers (R18 to R19) placed in right side of

third galley (G3), are wirelessly connected to router R4.

End devices (E6 to E9) attached with miners/moveable

equipment are wirelessly communicated with routers

R16, R15, R18 and R19, respectively.

Wireless sensor network in an underground mine

having incline entrance (Fig. 4B) consists of a personnel

computer (PC2), coordinator (C2), router (R20 to R34)

and end devices (E10 to E13). PC2 is connected to C2

using RS232 cable in surface (S2) control room (CR2).

Routers (R20, R21 and R22) are wirelessly connected

to C2 at 80 m apart in surface (S). Routers (R23 to R26)

placed in intake incline (I1) at 50 m are wirelessly

connected to router R22. Routers (R27 to R29) placed

in return incline (I2) are wirelessly connected to R20.

Routers (R30 to R34) placed in gallery (G4) at 50 m are

wirelessly connected to R26 and R29. End device (E10

to E13) fitted with miners/moveable equipment is

wirelessly communicated with routers R24, R34, R26

and R31, respectively.

Wireless sensor network in an opencast mine (Fig. 5)

consists of a personnel computer (PC3), coordinator

(C3), router (R35 to R44) and end devices (E14 and

E15). PC3 is connected to C3 using RS232 cable in

surface control room (CR3). Routers (R35 to R44)

placed along transport road (TR) of an opencast mine

(OCM) at an interval of around 80 m distance are

wirelessly connected with said coordinator (C3). End

devices (E14 and E15) fitted with dumpers (D1 and D2)

are wirelessly communicated with said routers (R38 and

R42) routers, respectively.

Case Study

Experiments were carried out at an underground mine

of Bharat Coking Coal limited, Dhanbad, India to

evaluate performance of developed system in terms of

packet delivery ratio of devices. Depending upon packet

delivery ratio, efficiency of network topology, position

of routers and maximum operating distance among end

devices, router and coordinator were determined. Fixed

packet injection rate and total number of packets sent

by end device to router or coordinator were 300 ms and

100, respectively for all experiments. Distance between

end device and coordinator was increased gradually from

40 m and 60 m for finding out maximum operating

distance considering packet loss detection (Fig. 6a).

Communication among one coordinator and two routers

was carried out simultaneously by increa

sing intermediate distance gradually from 60 m to 80 m

(Fig. 6b). Experiment was carried out to test data

communication from end device to a remote coordinator

in multi-hop topology by placing one router (Fig. 6c)

and two routers (Fig. 6d), respectively between

coordinator and end device. Experiment was carried out

to test data transmission from end device to a remote

coordinator in multi-hop even if routing path was L-

shaped (Fig. 6e) or S-shaped (Fig. 6f), which are very

common in underground mines. Packet delivery ratio is

100% for all experiments except L-shape (99%) and S-

shape (97%) topologies. It was also observed that

BANDYOPADHYAY et al: WIRELESS INFORMATION AND SAFETY SYSTEM FOR MINES 115

increment of intermediate distance between coordinator

and end device decreased packet delivery ratio.

Therefore, intermediate distance between coordinator

and end device is inversely proportional to packet

delivery ratio. Again, lesser number of hops routers

between end device and coordinator increased packet

delivery ratio. Therefore, relation between number of

hops and packet delivery ratio is also inversely

proportional. In underground mines near bends and

tunnels, packets were transmitted in either L-shape

topology or S-shape topology, which did not hamper rate

of packet delivery ratio.

Fig. 5—Layout of ZigBee devices in an opencast mine

116 J SCI IND RES VOL 68 FEBRUARY 2009

Conclusions

To overcome day-to-day problem faced by mine

management, installation of WISSM is a vital need for

mining industry. With the help of central processing unit

at pit top, it will be possible to keep track of miners and

machines moving in underground. It will also be possible

to keep record of time when respective miner is going

inside mine and coming back. Implementation of system

will also help mine management to keep record of

attendance and to identify persons who are delaying to

start his scheduled duty and/or coming back early. In

case of disaster, system will help in identifying trapped

miner along with their location and numbers, and this

will improve safety of miners.

E C

60 m

A)

R

R C

80 m

60 m

B)

E R C 40 m 40 m

C)

E R C R

D)

60 m 40 m 20 m

E

60 m

40 m

E R

R 40 m C

F)

80 m

20 m

R

C

E)

Fig. 6—Communication between: A) end device and coordinator; B) two routers and coordinator; C) & D)

end device and coordinator via routers; E) end device and coordinator via router in L-bend; and

F) end device and coordinator via router in S-bend

BANDYOPADHYAY et al: WIRELESS INFORMATION AND SAFETY SYSTEM FOR MINES 117

Acknowledgements

Authors thank Department of Information Technology

(DIT), Ministry of Communication and Information

Technology, Govt of India, New Delhi for funding the

work. Authors are also grateful to Dr K R Kini, Director,

Society for Applied Microwave Electronics Engineering

& Research (SAMEER), IIT Bombay Campus and Prof

A Bhattacharjee, IIT, Kharagpur for providing valuable

suggestions. Authors also thank Director, CIMFR,

Dhanbad for necessary help and support.

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