12-10-2012, 03:23 PM
LED-LDR Based Railway Crack Detection Scheme
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Basic rationale:
Transport is a key necessity for specialization that allows production
and consumption of products to occur at different locations. Transport has
throughout history been a spur to expansion as better transport leads to
more trade. Economic prosperity has always been dependent on increasing
the capacity and rationality of transport. But the infrastructure and
operation of transport has a great impact on the land and is the largest
drainer of energy, making transport sustainability and safety a major issue.
In India, we find that rail transport occupies a prominent position in
providing the necessary transport infrastructure to sustain and quench the
ever-burgeoning needs of a rapidly growing economy. Today, India
possesses the fourth largest railway network in the world. However, in
terms of the reliability and safety parameters, we have not yet reached truly
global standards. The principal problem has been the lack of cheap and
efficient technology to detect problems in the rail tracks and of course, the
lack of proper maintenance of rails which have resulted in the formation of
cracks in the rails and other similar problems caused by anti-social
elements which jeopardize the security of operation of rail transport. In the
past, this problem has lead to a number of derailments resulting in a heavy
loss of life and property. Cracks in rails have been identified to be the main
cause of derailments in the past, yet there have been no cheap automated
solutions available for testing purposes. Hence, owing to the crucial
repercussions of this problem, we have worked on implementing an
efficient and cost effective solution suitable for large scale application. We
hope that our idea can be implemented in the long run to facilitate better
safety standards and provide effective testing infrastructure for achieving
better results in the future.
Statistics to justify the problem:
The Indian Railways, today has 113,617 kilometres (70,598 mi).of
total track over a route of 63,974 kilometres (39,752 mi) and 7,083 stations.
It has the world's fourth largest railway network after those of the United
States, Russia and China. The railways traverse the length and breadth of
the country and carry over 30 million passengers and 2.8 million tons
of freight daily. It is the world's second largest commercial or utility
employer, with more than 1.36 million employees. Despite boasting such
impressive figures, we find that Indian rail network is still on the growth
trajectory trying to fuel the economic needs of our nation. Though we find
rail transport in India growing at a rapid pace, the associated safety
infrastructure facilities have not kept up with the aforementioned
proliferation. Our facilities are poor when compared to the international
standards and as a result, we have been having frequent derailments that
have resulted in severe loss of valuable human lives and also property. To
demonstrate the gravity of the problem, statistics say that there have been
11 accidents in 2011 till the month of july alone, which leaves much to be
desired regarding rail safety.
Survey of contemporary solutions:
The prompt detection of the conditions in rails that may lead to a
crack or rather a break now plays a critical role in the maintenance of rails
worldwide. The understanding of these mechanisms is constantly
improving and the evolution of a range of complementary (Non Destructive
Testing)NDT techniques has resulted in a number of tools for us to choose
from. Among the inspection methods used to ensure rail integrity, the
common ones are visual inspection, ultrasonic inspection and eddy current
inspection. Ultrasonic Inspections are common place in the rail industry in
many foreign countries. It is a relatively well understood technique and was
thought to be the best solution to crack detection. However, Ultrasonics can
only inspect the core of materials; that is, the method cannot check for
surface and near-surface cracking where many of the faults are located.
Eddy currents are used to tide over this limitation associated with
ultrasonics. They are effectively used to check for cracks located at the
surface of metals such as rails.
Justification of the proposed solution:
As mentioned in the literature survey, we find that the commonly
employed rail crack detection schemes in foreign countries are usually
ultrasonic or eddy current based techniques which boast of reasonably good
accuracy in most cases. However, the one characteristic which the above
mentioned methods have in common is that they are both expensive, which
makes them ineligible for implementation in the current Indian scenario.
Also, ultrasonics can only inspect the core of materials; that is, the method
cannot check for surface and near-surface cracking where many of the
faults are located. In addition, ultrasonic inspection of rails is usually
restricted to low speeds of around 20-30mph, which limits the viability
of testing many tracks regularly. Many of the most serious defects that can
develop in the rail head can be very difficult to detect using the currently
available inspection equipment.
Advantages of the proposed solution:
The currently existing technical solutions offered by many companies
in the detection of cracks in rails involve periodic maintenance coupled
with occasional monitoring usually once a month or in a similar timeframe.
Our project however possesses the inherent advantage of facilitating
monitoring of rail tracks on a daily basis during nights when the usual train
traffic is suspended. Further, we believe that the simplicity of our idea and
the easy-availability of the components make our project ideal for
implementation on a large scale with very little initial investment. The
simplicity of our project ensures robustness of operation and also the
design has been carefully modified to permit rugged operation. Another
disadvantage that can be attributed to the conventional commercially
available testing equipments is that they are heavy which poses a practical
limitation. However, this important disadvantage has been rectified in our
project as the design is simple and sensible enabling the device to be easily
portable.
Technical overview:
The core of our proposed crack detection scheme basically consists of
a Light Emitting Diode (LED)-Light Dependent Resistor (LDR) assembly
that functions as the rail crack detector. The principle involved in this crack
detection is the concept of LDR. The LED will be attached to one side of the
rails and the LDR to the opposite side. During normal operation, when
there are no cracks, the LED light does not fall on the LDR and hence the
LDR resistance is high. When the LED light falls on the LDR, the resistance
of the LDR gets reduced and the amount of reduction will be approximately
proportional to the intensity of the incident light. As a consequence, when
light from the LED deviates from its path due to the presence of a crack or a
break, a sudden decrease in the resistance value of the LDR can be
observed. This change in resistance indicates the presence of a crack or
some other similar structural defect in the rails. In order to detect the
current location of the device in case of detection of a crack, we make use of
a GPS receiver whose function is to receive the current latitude and
longitude data. To communicate the received information, we make use of a
GSM modem. The GSM module is being used to send the current latitude
and longitude data to the relevant authority as an SMS. The
aforementioned functionality has been achieved by interfacing the GSM
and GPS modules with the ATMEGA328 microcontroller on-board the
Arduino Uno board. The arduino integrated development environment is
an open-source project which simplified the coding greatly. The robot has
four wheels which are powered by two 12V batteries.