01-07-2013, 04:43 PM
ENHANCING MINE SAFETY WITH WIRELESS SENSOR NETWORKS USING ZIGBEE TECHNOLOGY
ENHANCING MINE SAFETY.pdf (Size: 110.23 KB / Downloads: 82)
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.
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.
Ultrasonic sensor
The purpose of ultrasonic sensor is to identify
any obstacles placed in the path. When compared
to infrared sensors, this sensor has high detection
range and has greater sensitivity. Due to this, it
will easily identify if any obstacle is present in the
robot’s path. The ultra sonic sensor consists of a
set of transmitters and receivers which operate at
the same frequency. The range of obstacle
detection in ultrasonic sensor starts from one
meter. The transmitter has two NAND gates
which act as multi-vibrator whose output is used
to drive a transducer. The trimmer adjusts the
output frequency of the transmitter. The receiver
uses a transducer to obtain the reflected signal; its
output is amplified by a transistor and 741 opamps.
Ultrasonic sensor has beam of angle 30
degree ie, from +15 degree to -15 degree and
some can detect obstacle from 6 meters.
Temperature sensor
For prototype, LM35 Temperature sensor was
used for measuring temperature and to give
analog value equivalent to the temperature to the
controller. It has three pins. One is for supply (5 v
DC), second pin is for analog output, and third pin
is for ground. The maximum and minimum
temperature limits of LM 35 are 150 and -55
degree Celsius.
DESIGN PROCESS
ZigBee nodes were placed along the walls of
Coal mine. Each ZigBee node is connected to a
PIC controller which measures the RSSI value
(Received Signal strength) from its node. RSSI is
the strength of signal received from the ZigBee
node which is connected directly with one
ZigBee node. The RSSI value is indirectly
proportional to temperature and if an explosion
occurs, the temperature in that node’s
environment will be higher than normal
condition which can be detected. By measuring
RSSI in each node, we can find the temperature
variation. For each degree Celsius increase of
temperature, there is a corresponding drop in
RSSI value from 8db to 10 db.
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.