ABSTRACT:
‘Accidents’, the word that flashes in today’s news bulletin. We know that the Indian railway network is the biggest in South Asia and perhaps the most complicated of all. Though the timetable has been perfectly framed, it is not possible to adhere to the pre-defined schedule. That is why train accidents have become common phenomena. As there are nearly 30,000 level crossings in India, the Government cannot afford to appoint workers to supervise the level crossings. So why don’t we improvise the system so that it can by itself detect train presence and avoid accidents!!!This paper may be considered as a combination of RFID, embedded systems and various communication techniques. This paper provides a solution to prevent railway accidents at unmanned railway crossings. In this paper we have also tried to provide a solution to the head to head collisions which is a great headache to the Indian railways.
KEYWORDS: RFID tag, embedded systems, RFID reader, transceiver, wireless technology, antenna.
INTRODUCTION:
We should lift up our shoulders to say that our Indian railway system is the 2nd largest in the world with more than 150 years of glorious service. But we must also feel sad about the fact that accidents do occur in this system. There are around 38,000 level crossings throughout India. It is true that railway accidents create a heavy damage to life and property. According to the Statistical Analysis the level crossings are 0.1% per million train km. There is a great demand among public for an accident free railway crossing. Level crossing accidents are mainly due to the impatient driving of the commuters crossing the tracks. They hurriedly cross the level crossings without realizing the super-sonic speed of trains. Though Modernization has entered in all fields of Railways (i.e. even to the extent of introducing bullet trains) we are not able to avert level crossing accidents. As per definition a Level Crossing is a place where a track and Highway/Road intersect each other at the same level.
ARCHITECTURE OF OUR PROJECT
Let us see the basic architecture of our project
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Let us see each block of this system, the way it works and various algorithms that we are designing to produce efficient closing and opening of the gates. We are dividing our paper into 2 main parts
2 MECHANISM
2.1 IDENTIFICAION
The first thing to mechanize the level crossing is Identification of train. We must know exactly where the train is coming in order to do the necessary operations. So in order to exactly identify the train we use RFID Technology. What is RFID? Radio-frequency identification (RFID) is the use of an object (typically referred to as an RFID tag) applied to or incorporated into a product, animal, or person for the purpose of identification and tracking using radio waves. Some tags can be read from several meters away and beyond the line of sight of the reader. This technology has 3 main parts:-
• An antenna or coil.
• A transceiver (with decoder).
• A transponder (or RFID tag) electronically programmed with unique information.
The antenna emits radio signals to activate the tag and read and write data to it. Antennas are the conduits between the tag and the transceiver, which controls the system’s data acquisition and communication. RFID tags are categorized either as active or passive: Active RFID tags are powered by an internal battery and are typically read/write, i.e. tag data can be rewritten and/or modified. Passive RFID tags operate without a separate external power source and obtain operating power generated from the reader. Passive tags are consequently much lighter than active tags, less expensive, and offer a virtually unlimited operational lifetime. Read only tags are typically passive and are programmed with a unique set of data (usually 64 to 2k) that cannot be modified. Read-only tags most often operate as a license plate, into a database similar to linear barcodes that reference a data base containing modifiable product specific information. The significant advantage of all types of RFID systems is the non-contact, non-line-of–sight nature of the technology. Tags can be read through a variety of substances such as snow, fog, ice, paint, crusted grime, and other visually and environmentally challenging conditions where barcodes any other technologies would be useless. A typical system includes several different kinds of readers, also known as sensors. These are radio frequency devices designed to detect and read tags to obtain the information stored on them. The reader powers an antenna to generate an RF field. When a tag passes through the field, the information stored on the chip in the tag is decoded by the reader and sent to the server which, in turn, communicates with the automated computerized system when the RFID system is interfaced with it. These RFID readers will send a high energy RF field described by the antenna position. When a tag comes in contact with the field of the reader, the tag energies due to electromagnetic induction (as it is an LC circuit), and this energy transfer will activate the tag and activate the microprocessor inside the tag and transmit the data stored in it to the reader.
2.1.1POSITIONING OF RFID TAG
In order to identify a tag by its reader the tag must be placed in proper position so that the readers on any account don’t miss the tag. So what we have decided is that, we place the RFID tags on both sides of the train such that the left side of first three compartments will have a tag and the compartments on the right three also have a tag. An EPC code is stored in it. For our project we change this EPC to ETC (electronic train code). Similar to an EPC code ETC also has 4 blocks. This ETC is made up of two parts:-
1. Train identifier
2. Position Identifier
Train identifier is used to identify the name of the train and position identifier is used to identify the side and the compartment in which the tag is present. Example for ETC is:
10 111011 00011 000001
Header Train code compartment side
Using this ETC we can identify which train is coming and its direction.
HOW RFID WORKS
The processor provides a timer-driven 125 KHz square wave for our carrier frequency. This is then sent through an RF choke, which is essentially a passive low-pass filter with steep drop-off to knock out the upper harmonics and leave us with only a sine wave. The sine wave is then amplified using an emitter follower PNP transistor and a half bridge to maximize current. Since our resonant circuit is a series L-C circuit, maximum resonance is achieved at minimum impedance, so it is very important that we provide adequate current amplification as to not overdrive our microcontroller. To help reduce the strain (and ramp up the current more) further, the square wave output from the MCU is put through parallel inverters.
On the receiving end, the signal is first half-wave rectified, since the negative part of the signal doesn't really make a difference, and is then fed through a half-wave R-C filter to help knock out most of the 125 KHz carrier and detect the envelope signal. This signal is then band pass filtered using a series a Twin-T active band pass filters, and low pass filtered with an active Butterworth filter to further decrease gain in frequencies outside of the 10-20 KHz area and increase gain of the envelope signals such that it saturates the op-amps of the filters. As a final stage the signal is put through a comparator and resistive divider to produce a nice square wave at logic levels. Some D-flip flops and a decade counter are used to extract data from the modulating square waves. Which are fed into the MCU and processed.
2.1.2 POSITIONING OF RFID READERS
Till now we saw how we are going to place the readers now let us see how we are going to place the RFID readers. Let us assume a track near the level crossing with level crossing as its reference. We take 2kms on either side and place the readers. Both the readers are placed opposite each other as shown bellow in the picture.
This is the position where we are going to place the readers in real time. Each reader is nothing but a Transreceiver circuit which acts as a full duplex system. These readers will be forming a field around it. For our project we form a closed lobe with the reader in its circumference. With proper orientation of antennae this region will cover 1 to 1.5 meters from its base. The tags will be detected only in this region so that there is no interference of these readers to the surrounding mobiles or any radio equipments. This is how we are going to identify which train is coming and its direction.
2.2 COMMUNICATIONS
We are dividing this communication into two parts:-
1. Tag - reader communication.
2. Reader –controller communication.
This system consists of a reader, connected to a host (or supervisory) system, which interrogates transponders when present in the reader’s antenna field. The Tag-it Host Protocol defines the communication between the host system and the readers. A second protocol, the Tag-it Transponder Protocol, defines communication between the reader and the transponders present in the reader’s active field. Derived from industry-standard protocols, both protocols have been designed to be efficient and flexible, while still remaining simple to implement. A layered approach allows implementation of compound commands for performance optimization.
The Host Protocol performs two main functions:
• Handling of data communication between host and reader.
• Carrying of requests for commands and responses to those commands from transponders.
Other services that the Host Protocol provides include:
• Management of the reader functionality, e.g. reader software version Reporting.
• Enhancement of basic transponder functionality by requesting execution of compound commands.
The Host Protocol provides the means of controlling the reader through the host system, which may consist of a microcontroller, a personal
Computer or a programmable logic controller. The reader supports a LAN communication interface.
To maximize data, particularly for continuous operation, the reader does not store large amounts of identification data on-board, and does not handle external inputs or outputs other than connection to the host. The Host Protocol is designed for point-to-point, half-duplex communications, with the host controller acting as the primary station and the reader as the secondary station. The host computer initiates all communications using the Host Protocol. This protocol consists, in most cases, of request/response pairs where the host waits for the response before continuing. Therefore, the host is not presented with large sequences of open requests and complex sequence numbering. To reduce message traffic, messages can be run continuously, producing multiple responses for a single message. The host must be able to buffer and process these responses, interrupting the flow if necessary. The Host Protocol is a binary, byte count-oriented protocol. To allow flexibility in controlling the reader, variable length data is passed within a defined frame. The data length is always passed as a parameter within the message, and the possible structures of the data contained are known by the communicating parties. Driven by speedy network processors and advanced software, RFID readers provide the same load balancing, Quos and security found in high-end IP routers. A tag reader will facilitate advanced applications by acting as a gateway between an IP network and tags that provide read-write data storage, on-board sensors and other features.
The network gateway functionality of RFID readers becomes even more critical in light of the channel-sharing, data-exchange and air-interface protocols required to accommodate two-way TCP/IP traffic. Before exchanging information with a tag, a networked reader searches for and retrieves the ID of each tag in its read zone. This discovery process produces a list of IDs, which then must be made available to an external software system such as a warehouse management system that resides on a remote networked server. The same networked discovery process applies in the case of sensor tags. Then, bidirectional communication occurs between the tag and software residing on a networked server. In some cases, such as time-critical movement of tagged packages on a conveyor belt, the reader might be given authority to act quickly on a networked server's behalf. This can be accomplished by running specialized software on the reader, or by implementing and populating a policy-based decision-making mechanism, mimicking those employed by high-end IP routers.
The new RFID readers are designed to provide the functionality of a gateway for large networks. RF interfaces the tags residing on one side of a reader, with a database server and a TCP/IP network interface on the other side, fully equipped to be part of a networked-distributed data aggregation and analysis system. Before going to the embedded control let us see how to processes the data. Let’s move to the computerization.
3 COMPUTERISATION
3.1 DATA PROCESSING UNIT
So far discussed about how we are going to transfer the data from the train in tag to the reader and from the reader to the main controller. Now let us see the processes used in the computer. Let us take a case study of Mumbai where from one station to another there are around 15 to 20 level crossings. What we are going to do is make a closed network with this station as a base. Almost all stations in India have a computer to perform some operation. Every train has a well defined schedule and all routes are predefined. All trains have an exact schedule. We make use of this condition in our concept of CALC. We store each and every train database in the pc kept in station, as in which track it should traveled. All the details we store in the database of the computer. We divide the RFID readers into pairs some on the start point and some on the end point. Once the train has entered the first track we will be sending the details of the reader along with the information collected by it through the LAN network. Every reader has an Ethernet port which is used to form a network with other readers or computers. Since all of them are single way transactions, we use star topology.
Let us see this case when the train is moving from right to left and here this reader 1 & 2 forms a pair when the train enters the region of reader 1. The data is transmitted to the pc where the data is compared with predefined database. The flow diagram is given below:-
Once the pc receives the data the pc knows which gate should be activated. Now we use wireless communication to activate that particular receiver. We are using a device which is similar to RF switch. Each receiver is tuned to a particular frequency. These details we will be stored in the pc. The pc is interfaced to a transmitter with RS232 port when a particular receiver is to be activated.
The pc will instruct the transmitter to transmit the data in that particular frequency using FSK modulation. In order to avoid any false triggering we are going to send a code which is individual to each receiver. The receiver will be activated only if we get the exact data. We will be transmitting 3 times the data so that there is no probability of missing or false triggering. This is how we are going to activate a particular receiver in the network. With high energy transistors we can cover 20 nautical miles, but for our project we want to cover 20 to 30 km with the station as a base. Once the receiver receives the data the control passes over to embedded networks.
ACCIDENT AVOIDER:
Even with such rapid advancement of technologies there are no accurate devices which can detect and avoid accidents. We have analyzed how our proposal can solve this problem. Accidents usually don’t occur near stations, the main reason for accidents are false track changing due to humanoid errors. Recently, due to this false changing of signal, a train collapsed. Why do such errors happen? That is why we want the entire railways to computerize. We have divided the entire railways into 2 regions; 1st track changing layers and 2nd long straight tracks. Any complicated railway lines will fall in these two regions.
CASE 1:TRACK CHANGING SYSTEM
Consider an example; the 1st train is passing from right to left and the 2nd train from left to right in real time. The train two should wait until the train one crosses the track but most of the time this fails. Before the 1st train crosses the track the train two hits the 1st train resulting in major accidents. So in order to avoid such accidents in future, we propose this concept. In this concept there will be a reader on all the sides of the track. When train 1 reaches reader one, the reader one will sense the tag in the first three compartments of the train and transmit the data to the network to which it is connected. The controller analyses the data and checks whether the track is to be changed. At the same time if reader 3 also sends a data then the track will automatically switch and until train 1 reaches reader 3, the signal to the train 2 will be red. Once the train clears the way the signal automatically changes to green. As we use computers, the speed calculations and the process will be in terms of mille per second. Therefore there is sufficient time to avoid accidents and save number of lives.
CASE 2:A SINGLE LONG TRACK
In this case there will be a single long track and the readers are placed at starting and ending of the track. When the train moves from left to right, the reader1 will send the data to the P.C. Once we have the data we can identify the track information and where it is placed. Before train 1 reaching reader 2, if some other train due to false track changing enters the same track as train 1, reader two will be attached with the small embedded system which will immediately turn all the four signals placed on the track to glow red. Since the signals are placed at starting and ending of the track, any accidents due to head on collision can be avoided. Thus the property of the public, the life of the people and the cost of the Govt. is saved. Once saved. Once this case ends it will move forward to case
EMBEDED CONTROL:
This is a last part where the actions are taken. Once the receiver receives the data, with the help of embedded system, we check whether the data present in the signal is the same as the data given initially. Once this is checked the control is transformed to a loud speaker to alert the surroundings. Then after five seconds the gate automatically closes. Thus we avoid unnecessary accidents happening at the level crossings. Along with the siren there is a red light to indicate the arrival of the train. Another problem here is how to help some one stuck in the middle. We cannot leave them like that. Once again there are two types: 1) the vehicle is stuck in between two closed gates. 2) The vehicle is at the closing of the gate for the first case. We don’t use any special technology here. We just increase the spacing between the railway line and the gate, so that even a can accommodate in this space. If the vehicle is at the closing end of the gate, then such a heavy load fall can cost damage to the life of the person inside the vehicle and the vehicle itself. So we use I.R. technology here. This will activate only at the time of closing of the gates. Once the ‘close’ signal is given by the embedded system we check whether any interrupt is present. If ‘yes’, the alarm is given to the driver to move and once the interrupt is clear, the gate is closed.
FUTURE SCOPE:
This entire network can be made wireless in the near future. The range of wireless transmission can also be increased to a large extent. If this wireless technology is fully implemented then we will be able to monitor the train throughout and even track changing mechanisms. This can be made automatic which helps in preventing train collision. Thus we will be able to convert our second largest railway network as the most sophisticated and modernized network in the world.
In this new concept of approaching train-warning system, WARNING SYSTEM is installed at level crossings for providing warning to road traffic about the approaching train. The warning starts only when the train is present at a pre determined distance from the level crossing and the warning continues for about 3 minutes. This concept can be applied to level crossings where heavy traffic passes and when visibility is poor.
CONCLUSION:
In the advent of modernization in Indian Railways, the bottleneck in safety, like accidents in unmanned level crossings is to be dealt in a scientific manner involving latest technologies along with rational thinking for minimizing the accidents. This idea, if brought to limelight in Indian railway systems, will definitely hit the other nations with a bang!!!!!
REFERENCES:
1. RFID.A.Guide.to.Radio.Frequency. Identification- v. Daniel hunt Albert Puglia mike Puglia
2. RFID handbook-Klaus Finkenzeller
3. D.M. Ewatt and M. Hayes. Gillette razors get new edge: RFID tags.
4. Mapping and Localization with RFID Technology -Matthias Phil pose
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