24-08-2012, 02:58 PM
ENHANCING MINE SAFETY WITH WIRELESS SENSOR NETWORKS USING ZIGBEE TECHNOLOGY
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ABSTRACT
In coal mines, whenever explosions occur, the rescue work is done by rescue workers without any prior
knowledge of the environmental condition inside coal mine because the mine monitoring systems may be
destroyed or damaged. This makes the life of rescue workers very risky. It also takes some time for the
rescue workers to reach the spot. According to the proposed system, a ZigBee network controlled automatic
robot has been developed for assisting rescuers. This system works even when a ZigBee node fails.
Whenever any explosions occur, the robot automatically detects the explosion, finds the explosion location
and enters the coal mine tunnel well before the arrival of rescuers. It finds the location of accident, searches
for survivors to give them first aid at right time and informs the rescue team about environmental
conditions and about the survivors inside the coal mine.
INTRODUCTION
In any hazardous work environment mines,
safety of human life is an important concern.
Mines [1]-[5] and specifically coal mines are
places where constantly lives are lost and many
countless are injured due to landslides and
explosions. Not only this, there are great losses
in property too. The present systems installed in
many such places are still incapable of saving
lives of those who risk their lives for this
profession. To improve life safety, many systems
have been designed, and have even been
implemented in some countries today.
One such design is to send a robot inside a
coal mine. A robot equipped with sensors for
detecting various poisonous gases and a wireless
transmitter and receiver can be our eyes and ears
in such an environment. It can navigate through a
mine and send back information to the person
monitoring its movement from a safe place
outside, all that is happening inside the mine and
even warn the workers regarding the places that
may actually be life threatening. A robot with
this given description was designed. In previous
efforts, the robots were controlled by the coal
miners using remote control and were not
automatic. The unique thing about this proposed
system is that the robot is automatic.
WIRELESS SENSOR NETWORKS
A wireless sensor network [6]-[10] such as
one using ZigBee can penetrate walls and be
used in places where a wired network is either
not suitable or cannot be established. The
advances in the wireless technology have made it
possible to establish a network just by placing
the communicating nodes at the required places
and switching on the transmitters in them. It is
possible to have great transfer rates even at long
ranges. With such usefulness and many more
features, a wireless network is the surely needed
in mines where it is not possible to establish a
network in time using wires. Also, in case of
cave-ins, or an explosion the wire may get
damaged making the entire network useless.
ZigBee is used to overcome all the shortcomings
of a wired network. With its great range even
through solid objects such as walls or in this
case, mines, it is the most suited technology for
our purpose.
OVERVIEW OF THE SYSTEM FRAME
WORK
Whenever a landslide or explosion occurs, the
ZigBee node in that particular area may get
damaged or its signal strength may be reduced.
Furthermore when any blast occurs or, which is
about to occur, the surrounding temperature to
that ZigBee node will be very high beyond the
limit. Since RSSI is indirectly proportional to
temperature, RSSI value decreases in accordance
with a corresponding increase in temperature.
RSSI value from each node is checked so that it
does not go beyond its lowest limit.
The lowest signal strength is fixed by
measuring temperature of the same node for
many numbers of iterations and taking lowest of
all such readings. The other ZigBee nodes in its
network carry the information about the
damaged node to the coordinator, which is kept
at a fixed point in the entrance of coal mine.
Then the coordinator directs a ZigBee node in
robot to route the robot towards the damaged
ZigBee node’s location. In case of any unhealthy
condition on its way to the destination, the robot
sends the information to the coordinator so that
the rescue workers can be alerted about the
conditions before entering the coal mine.
ZigBee
It is a wireless communication protocol, with a
short distance, safe and reliable connection. It is
capable of collecting various parameters from
different nodes. Since GPS, technology will not
work under closed environment; ZigBee was
more suitable for this application. Transmission
rate of ZigBee is 250kb/s. It is a 20 pin chip. Pin 2
is meant for serial data out and Pin3 is for serial
data in. Pin 1 is for supply. Pin 10 is for ground.
Pin 6 is meant for RSSI. ZigBee can be
configured to form different types of networks
like peer to peer, ring type and mesh. ZigBee used
here is Tarang. Its outdoor line of sight range is up
to 50kms with directional antennas. Transmit
power is 1 watt/ 30 db. Receiver sensitivity is up
to 107db.
CONCLUSION
This work solves the issues like prevention of
second explosion caused if the amount of methane
gas is high in air by early detection. Time taken
for rescue work will be reduced since it is
automated. Increase life safety of rescuers and
coal mine workers, reduces the risk taken by
rescuers and complexity. The ZigBee system
works even if a ZigBee node gets damaged by
explosion.