Title of Invention

A RAILWAY COLLISION AVOIDANCE SYSTEM (RACAS)

Abstract THE INVENTION PROVIDES A RAILWAY COLLISION AVOIDANCE SYSTEM (RACAS) WHICH IS OF RELATIVELY SIMPLE DESIGN, COMPACT CONSTRUCTION AND CAPABLE OF ESTABLISHING A RELIABLE CONNECTIVITY WITH EVERY TRAIN LYING WITHIN A RANGE OF 1 500-3000 METRE AND OPERATING THE BRAKING ACTION TO AVOID COLLISION BETWEEN TRAINS RUNNING ON A COMMON TRACK, OPERABLE FROM A QUASI-CONNECTIVITY PROTOCOL (FORMAT) COMPRISING AN UNNUMBERED INFORMATION FRAME HAVING AN ADDITIONAL 1 MS TRAINING (LEARNING) SEQUENCE CONSISTING OF 26.04 US PULSES BEFORE EVERY START FLAG WITHOUT REQUIRING ACKNOWLEDGEMENT SIGNAL OF THE RECEIPT OF GOOD PACKETS BEFORE TRANSMITTING THE NEXT FRAME OF DATA, AND COMPRISES A PAIR OF MICROCONTROLLER BASED RADIO SIGNAL TRANSPONDERS INSTALLED ONE EACH IN THE DRIVER'S CABIN AND GUARD'S CABIN OF A TRAIN, EACH TRANSPONDER BEING ALLOTTED A UNIQUE IDENTITY TAG CORRESPONDING TO THE NAME OF THE TRAIN AND OF THE TRACK ON WHICH THE TRAIN IS RUNNING; A CONTROL DESK CONTAINING AN ANTI-COLLISION CONTROL (ACC) AND OTHER ACCESSORIES MOUNTED IN THE DRIVER'S CABIN; STATIC BEACONS (SB) INSTALLED AT INTERVALS ALONG THE TRACK; AND STATION PACKET TERMINALS (SPT) INSTALLED ONE EACH AT THE IMPORTANT RAILWAY STATIONS LYING ALONG THE TRACK.
Full Text The present invention relates to a Railway Collision Avoidance System in a railway network.
The system uses a paired digital transponder (i.e. transmitter/receiver) operating in the radio band (i.e. 915-925 MHz) for interrogation and reply between trains in a railway network and producing alarms against any impending head-on or end-on collision between the trains. The system provides a safety measure for preventing collisions between trains arising from human/instrumental errors in the Route Relay Interlocking (RRI) of the existing traffic control system in the railway networks.
In the Indian railway networks collision occurring between trains is still a very serious matter with over thirteen thousand trains moving in the networks everyday. There is room for adopting an improved system for preventing collision between trains caused by human/instrumental errors in the operation of the existing Route Relay Interlocking (RRI) arrangements.
The commonly used Anti-collision RADARS or Anti-Collision device (ACD) can perform track mapping only for a limited distance upto 300-500 metre or so in a congested track circuit with overhead tractions and other structures. But the braking action activated at speeds in excess of 150 Km/hr with all the bulk and momentum of a moving train at distances of the RADAR visfon range is quite inadequate.
The PLCC communication ACD and other copper techniques based on protocols tike the SCADA etc. can make bi-directional transfer of data and control signals for track management but these involve complicated switching circuits for operation in a closed system, which may not be compatible to any of the modern information networks for data transport and control. Moreover the provision of such systems is slow requiring a nigh grade of maintenance for the cable, track and traction.
US 5,620, 155 discloses a railway train signalling system for remotely operating warning devices, at crossings and for receiving warning device operational information, comprising a transmitter and a receiver located in each train, and at each crossing of rail track and road operating in association with a global satellite positioning system or link; and a receiver in each motor vehicle crossing the rail track to receive the warning of an oncoming train.
US 5,890, 682 discloses a railway crossing collision avoidance system for alerting a road vehicle approaching a railroad crossing, of an oncoming rail vehicle, comprising a tracking apparatus, a transmitter, responsive to the tracking apparatus, for transmitting tracking data over a satellite communications link and a satellite communications receiver in each train; and one each of processor, tracking apparatus, I.e. global positioning system receiver, and at least one sensor located at each rail-road crossing.
/2/

The systems disclosed in both US 5, 620, 155 and US 5, 890, 682 are meant for providing warning signals to road vehicles and for checking the operating status of signalling devices located at the crossings, operating in association with global satellite communications links. The drawbacks of these prior art systems are that (a) these are not capable of avoiding collision between trains running on the same track by automatically applying braking action on the movement of the trains to avoid collision thereof, (b) these being dependent on global satellite. Communications link for their operation, cannot function when the said link is not available.
The object of the invention is to provide a railway collision avoidance system (RACAS) in a train, which is of relatively simple design, compact construction and capable of establishing a quasi-packet connectivity lasting for 2-3 min or so with every train lying within its radio range, which may be 3000 metre or more in an ideal condition of the track and 1500-3000 metre under not so ideal condition of the track, for ascertaining and averting impending collisions between the trains running on a common track, by operating the braking action, on the movement of the trains automatically.
The design of RACVAS is novel and relatively simple. Each train is provided with a pair of transponders (transmitter/receivers) located one each at the front and rear ends thereof. The microcontroller based transponders are paired to operate in full duplex mode and are allotted a unique identity, which corresponds to the name of the train and track on which the train is running. Each track is allotted an identity with a motion vector (Up/Down or STATIC).
The transponder in each train beacons radio interrogation/identification packets of digital signals every 5/15/30 Sec or so as the train moves up or down of a track in a railway network. A master Control Unit (MCU) in the transponder compares the track identification and motion data in the received signal with the identification and motion data of the track on which the train itself is running and generates alarms against any possible head-on and end-on collision with the train from which the received signal is transmitted. The transponders used are based on the micro controllers and transceivers manufacturers by Texas Instrumwents (TT) operating on radio band (i.e.915-925 MHz), Such devices are found to be compact in size and reliable in performance.
/2a/

The various Analogue and Digital Integrated Circuits (ICs) used in each pair of transponders installed in each train are listed in Tabte I.
In the invented system 250 such transponder pairs can be accommodated in a railway network, each provided with a unique Asset Tag Identity (ATI) but this number can be easily increased as required.
The other sub-units used in the invented system are Static Beacons (SB) and Station Packet Terminals (5PT) which are basically of same configuration with some differences containing a reduced number ICs. The SPTs store data in the PC Hard Disc and hence the Train Data Recorder Memory (32+32 KB) is not required to be used. The SBs are provided with Train Data Recorder Memory (32+32 KB).
The Master Control Unit (MCU) which is logically designated as
TABLE!

LIST OF INTEGRATED
CIRCUITS (ANALOG & DIGITAL) IN RACAS

SL.NO.
IC PART HO.
DESCRIPTION
QTY
MANUFACTURER
01
TOF6900A
Single Chip RF Transceiver
04
UUSA
02
PMS430E112
Mixed Single (EPROM Ver) Microcontroller
08
TI,USA
03
SN75LV4737A
RS232 une Driver/Receiver
02
UOSA
04
CD74HCT151
8 Input Multiplexer
02
UUSA
05
CD74HCT193
4 Bit Up/Down Counter
16
UUSA
06
SN74LVT244B
Octal Buffer/Driver
04
T1,USA
07
SN74HCT244
Octal Buffer/Driver
02
TI.USA
08
CD74HCT154
4 to 16 Une Decoder/Demux
02
UUSA
09
SN74HCT245
Octal Bus Transceiver
04
UUSA
10
SN74HCT373
Octal Transparent Latch
04
UUSA
11
CD74HCT259
8 Bit Addressable Latch
02
UUSA
12
SIM74HCT1G08
Little Logic (AND)
04
UUSA
13
SN74HCT1G04
little Logic (NOT)
04
UUSA
14
TPS7233OD
Vottege Regulator
04
UUSA
15
TPS7230OD
Voltage Regulator
02
TI,USA
16
TPS7250OD
Voltage Regulator
10
UUSA
17
HM62256LP
Static RAM(32KB)
04
Toshiba, JDR,Fuiitsu
18
BGA2001
MMIC (Low Noise, 2 GHz)
02
Philips Holland
19
MSA-0885
MMIC (Substitute MAR-8)
02
Agilent, Mini Circuits
20
M68716
Hybrid Power Module
02
Mitsubishi Japan
21
TIL i53/154/155
Optocupler
36
UUSA
3

Anti-Collision Controller (ACC) is used only in the transponder-Pairs located in Hie trains but: not In the transponders used in Static Beacons (SB) or Station Packet Terminals (SPT).
The SBs are installed at intervals along a trade and at strategic locations. The SPTs inter act with the trains passing a static and log the relevant dais, time of passing and other Information which are ultimately transported to a Network Control Facility (NCF) through a long haul data transport backbone- SBs are used also for Issuing advanced warning to the trains in a circuit In cases of &ack disruption, emergencies etc. SBs can also serve as repeaters in the case of curved tracks to extend the radio range for alerting trains running up and down such curved tracks. SBs can effectively protect the railway level crossings by providing advanced warning to the trains approaching the crossings regarding the traffic congestions there.
The invented system can be extended Into the 3G type Railway Network Management System, which is capable of supporting train email transfers through BBS/TCP/IP connectivity, VOIP etc.
The basic technical features of the invented system are presented in Tables II and XXI.
IABLE1I
BASIC TJCHMSCJtt, FEATURES
Band of operation ; 850 to 950 MHz
Transmit/Receive Frequency : 915 (TX) & 925{RX) MHz (Programmable)
Type of Modulation (RF) ; 2 PSK (deviation ± 30 KHz)
Modulation Data Input, m(t) : Binary Data (Baseband)
Spectra! SandwkfthCR : 150 KHz
Transmit/receive separation : 10 MHz
Transmit/receive operation ; Shdlrecttonaf^fl-dup^Non-Sleep mode
Receive Trigger Sensraviiv : -90 dBm and higher (RSSI alert)
IF Frequency 10.7 MHz
RF Power Output : +37 dBm (5 watt)
RF Input/Output Impedance : 50 ohm (5MA-F/ N type)
Antenna Type : Corner reflector, 60/90 degree with 3/1
dipole
Antenna Polarization : Vertical
Antenna Gain (Approx.) ; 10 to 15 dBi
Power Supply : +12 VDC Battery
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TABLE III INPUT / OUTPUT PARTICULARS
INPUT (2 Byte Composite Data)
Train Identity/Asset Tag data ; 8 0it(i* Byte Data) stored in ACC/MCU Eprom
Trade Identity Data : 4 Bit^0* 8tf& Data/Lower Half, RRI uploaded)
Status /Motion Vector data ; 4 Bit (2nd Byte Data/Upper Half, selected
/enabled
OUTPUT f DISPLAY ft ALAffftV-





Annunciation (Gen.)
Data Display
Alarm

Battery Status
Radio Signal Display
DANGER ALERT

Module Power
RRI Track Data
AUDIBLE AL£RT

Transmit/Receive
Status Data
BRAKING (STOP)


Antenna Switch display



RF CPU Self Diagnostic



Packet Engine Diagnostic



MCU (ACO Diagnostic


OUTPUT fTASKS)-
a) togging of Daia in Train Dat" Recorder (TDR).
b) Data download to all passing statk)ns(SPT).
c) Processing of advanced warnings from Static Beacons {SB},
d) Beacon Transmission of identification signals every 5/15/30 sec.
The particulars of the communication protocol developed ami used in the invented system are presented in Table IV,
Racas QuasKkmnectivitY Format (based on x,25 structure)
PCM Data Coding-Non Return to Zero-Space (NRZ-S)
Data Format-! ms training fleaming) sequence cof"fe"irig of 26.04 us pulses
followed by Start Rag, Address Rekf# Info. Reid, Frame Oieck Sequence and Stop
Rag (Total ;i msTS ^ 7 Byte); Bps -38.8 kbps
Program Intefface - RS232 to Personal Computer or GPS (with NMEA 0183)
The invention is now described in further detail with reference to the preferred embodiments thereof, as illustrated by way of examples only In the accompanying drawings in which -
Figure 1 is a schematic view of the Anti-CoMon Control (ACQ Desk;
Rgure 2(A) Is a sketch showing the side view of train carriages moving on railway tracks;
Rgure 2(8) is a sketch showing plan view of train carriages moving on railway tracks;
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Figure 2 (c) is the block diagram of the transponders located one each at the tail end and head end of a train;
Figure 3 illustrates the coding scheme for a number of tracks;
Figure: 4 shows sketch of the situation for averting a head-on or end-on collision of two trains moving on a common straight track;
Figure 5 shows a situation for averting a head-on or end-on collision of two trains moving on a common curved track;
Figures 6 and 7 illustrate schematically the quasi-connectivrty protocol used in the invented system;
Figure 8A is a block diagram showing the list of modules arranged in a single transponder; Rgure 8B shows the operational logic flowchart diagram of the invented system; Figure 9 shows the architecture of the paired digital transponders used in the system; and Rgure 10 illustrates a display panel of the track animation and radio signal.
Referring to Fig. 1, the anti-coliision control (ACC) (54A) desk (I) comprises a track animation and radio signal display unit (18), a battery status Indicator (2), a module power Indicator (3), a route relay interlocking (RRI) track data indicator (4), a status data indicator (5), a data transmission /reception (TXfRX) Indicator (6), a motion vector set (7), a system reset (8), an activation key/switch (9), a control bypass/standby set (10), a mode control (11), an audio alarm (12), an input data port (13), an output data port (14), with a pin jack (15) for connecting equipment marked (15A to 15 D and 34), a manual alert button (16), a danger alert (17), a master control unit (MCU) diagnostic (18), an alarm /alert set (19), a packet engine (PE) diagnostic (20), a RF CPU/ train data recorder (TDR) diagnostic (21) and an antenna (RX) (22).
The input at the input data port (13) comprises a 2 byte composite data containing the train identity/asset tag data of S bit (1st byte data) stored In the anti-collision controller / master control unit (ACC/MCU EPROM), track identity data of 4 bit (2nd byte data / lower half, RRI uploaded); and status/motion vector data of 4 bit (2nd byte data /upper half, selected/enabled).
The features of the output: data are also setout in Table XXL
Referring to Bgs 2(A), 2 (B) and 2 (Q, a transponder (23) is located one each at the tail end (24) and head end (25) of a train (26) travelling on track (tl) (27).
A signal postttiavtng signal (29), and a static beacon post (30) with static beacon (SB) (31) are also provided on the track (27). A station (32) having a station packet terminal (SPT) (33) is shown on the tack (27).
6

The transponder (23) is an UHF full duplex, frequency shift keying (FSK) transmitter/receiver. The two transponders, one located at the tail end and the other located at the head end of a train are operable in a master/slave mode. Each train in a railway network is allotted an unique Asset Tag Identity (ATT) of a Byte Word programmed in the Master Control Unit (MCU) (34) which is also a logically anti collision controller(ACQ.
Referring to Fig. 3, tracks (tl) (27) in a railway network are each allotted a unique identity code such as Tracks tl,t2,t3,t4,t5,t6,....tlO.
The motion vector or motion status of a train moving up /down a track Is as shown below:

The motion vector or motion status of a train is an input function set by the driver of the train in the control desk shown in Fig 1.
The existing route relay interlocking device (RRI) (35) is provided with means, such as magnetic or optical or any other typer to upload a 4 bit track data to the Master Control Unit (MCU) (34) as the train moves over a track. When the train moves up^ the track, the track data is transmitted at a frequency fi MHZ (e-g. 915 MHz) and is received at a frequency f2 MHz (eg.925 MHz). When the train moves down| the track, the track data is transmitted at a frequency f2 MHZ (e.g. 925 MHZ) and is received at a frequency fi MHZ (e.g. 915 MHZ).
Static beacon SB(3i) and station packet terminal (SPT) (33) each are also provided with transponders (23) which are similar to the transponders used In the train with some changes for uploading and downloading of data from the trains passing over the track and the station and for issuing advanced warning In case of any track disruption or emergency situation occurring In the railway network.
Referring to fig.4, when two trains approach each other in a head-on or end-on direction the radio signals transmitted from the transponder of each train are intercepted by each train as soon as the two trains are in the radio range of at least 1000-1500 metre. The Master Control Unit (MCU) (34) of foe transponder in each train decodes the intercepted signal data and compares the decoded data with the track data contained therein. If it is found that the two trains are on
7

the same track, the MCU switches to Its ALERT MODE and transmits continuously the Beacon Alert Signals and thereby both the trains are brought to a halt to avoid a collision thereof.
Referring to Rg. 5, static beacons (SB) (31) are provided at the bends of a curved track (27), to act as repeaters for increasing the range of tf" radio signals transmitted from the tamsponders in the train moving on the same track (27).
Referring to Figs. 5 ,6 and 7 the invented system is operated with link-layer protocol named as the Quase-Connectivity Format developed for modification of the known 'OCnT. Recommendation X.25 Frame Format provided with a Start Rag and a Stop Rag, by employing Bit stuffing in the flag sequence to make the packet frame less bulky. The particulars of the quasl-connectivlty format are presented in Table IV.
The Quar.i-Connectivity Format (35A) uses an unnumbered information frame (U.I.) (36) having an additional 1ms training (learning) sequence 05) (37) consisting of 26.04 us pulses before every start flag, making thereby a deviation from full connectivity format of the said C&TT, Recommendation X.25 protocol which demands ttte use of numbered frames with return acknowledgement before transmission of the next frame to maintain the connectivity and data integrity in coherence. The full connectivity protocol requires a fairly steady channel of tolerable bit error rate (BER).
The quasi-connectMty protocol according to the present invention provides a mode of synchronous transfer of data from one point to another without requiring the acknowledgement (ACK) signal of receipt of good packets before transmission of the next frame, and without rejecting bad packets, and Is capable of carrying out date Justification and verification liberally after receipt of every frame. The quasi-connectivity protocol defines a digital transmission which starts with a training (learning) sequence (TS) (37) of 1 ms consisting of 26.04 us pulses followed by a Start flag (TF) (38) and ending with a Stop Rag (SB (39) in one single frame (36), which contains also a 2 byte address (40) consisting of 8 bit train data (ID) (41), 4 bit track data (42) and 4 bit status (43). 1 Byte information (44) consisting of 4 bit track identity (TI) (46), 4 bit Status(47) and 2 byte frame check sequence (FCS) (45).
Referring to Figs. 8A and 8B the flow chart shown is used to exchange packet frame (UI) (36 of fig.7) containing track data (ID) (42) and status data (43) between two trains approaching each other, so that the two trains can read and compare each others data and take stock of the situation on the track. When the two trains are within the radio range (1500-3000 metre) of each other, the packet of digital frames transmitted from one train transponder (23) (Rg.2) is intercepted by the transponder in the other train generating a data interrupt in the packet engine (PE) (15A) (Rg.l) of the interceptor train in synchronism with the 1 ms training (learning) sequence (T5) (37) (Rg.7) and the start flag (SF) (38) (Rg.7). The data stream is read by the packet engine (PE) (15A of Rg.l.) of the interceptor train and the S byte of the data excluding the flags (Rg. 7) is stored in the memory((32 KB RX Static Random Access Memory (SRAMJfto perform the steps of the operation shown in Rg. 8B as stated below.
(a) It registers the 2 byte long frame check sequence (FCS) (45) (Rg.7), calculates the FCS derived from the received chain of l's and 0's and compares the same with its own FCS (45) . If both are same (And Logic) then the data is accepted for logging and further comparison. This is a Cycle Redundancy Check (CRQ performed on every received frame.
8

(b) If the received FCS does not laity, then it compares the data at the address field (2nd
byte) with that of the information ftdd (1 byte) . It is to be noted that the track data (42)
and the status data (43) which are inserted in the address field is again repeated in the
information field (44) (Rg.7) to provide forward error correction (FEQ with 50% vital
data redundancy. If the two fields i.e. address (40) and information (44) match (Rg.7)
and are the same (AND logic) , then the data is accepted for logging and further
comparison.
(c) If, on the otherhand, the two fields i.e. address (40) and information (44) (Rg,7) do not
match i.e. are not the same, then, the packet Engine (PE) (15A) (Hgs.l) rejects the frame
and does not log it. A further branch of processing is then done at the master control unit
(MCU) (34) (Rg.4) by registering the address (40) and information (44) field date as
different sets of data in the presence of receive signal strength Indicator (RSSI) (48) Alert
which is monitored for 60 to 90 sec without any different identification packet received
within the time period, and comparing the same with its own track data before deciding
on a Braking Action. This fuzzy reasoning in particular has been provided to ensure safety
from all logical angles. The fuzzy logic based on RSSI (48) Alert is also helpful for
detecting collisions over much longer distances, although at times such logic may be
embarrassing.
(d) The received/intercepted track and status data is compared with the train's resident track
and status data stored in the TX memory (32KB, RX SRAM). If the two are same, then Braking Action follows along with frantic Beacon Alerts on the channel.
The quasi -connectivity protocol (table IV) is a logical compromise between full connectivity and no connectivity (Proto and Unproto modes). In the Interests of safety, data fields can not be rejected as long as they are not verified. And finally if the same cannot be decided digitally, then fuzzy logic based on RSSI levels and signal direction can supplement a final evasive action.
The paired digital transponders used in the invented system and shown in Rg.8A and 9 are each a dual transponder, identical In all aspects, but configured in a master/slave fashion. Only one of the two transponders in a pair carries out the braking action. Referring to Fig., 8A and 9, each transponder of a pair comprises (a) RF Part (49), (b) Packet Part (15B) and (c) Anti-Collision Control (ACC) (34A).
(a) The RF Part (49) contalns:-
i. 2 nos. TRF69O0A RF Modules based on the TOF6900A T1,USA Single Chip Transceiver, one being used for receiving and other for transmitting mode 0 and mode 1 respectively.
ii. X set of RX Antenna (52) and Antenna Switcher (AS) (53) comprising a 180 degree Scan Comer Reflector Antenna with three resonant dipoles switched by an Antenna Switcher with a low noise amplifier for FSK reception (Deviation ± 30KHZ/Bandwidth 150KH2).
iii. 1 no. TX Antenna (54) and RF Power Amplifier (PA) (55) comprising a 90 degree angle corner reflector Antenna with a 5 watt RF Amplifier for WBFSK transmission.
9

iv. t no. RF CPU ((Central Processing Unit, & 1 no. Radio Signal Display (RSD) (ST) which 1$ provided to display the resultant direction with respect to the proximity estimated by a 5-levei signal rating of -90 dBm to 40 dBm as the Track Animation and Radio Signal on the Control Desk (Rg.l). The radb signal display {RSD) (57) displays the logic output from the RF CPU (56) which is a 4 bit data which Is decoded again on a 4 to 16 line decoder (58) in the RSI panel and is displayed by an array of LEDyPanet lamps (59) as shown in Rg.10. During boot up and during system failure the RSD Panel (57) is used by the RF CPU (56) as a diagnostics display to communicate to the user the type of failure that has occurred In the RF Part.
The Packet or the Packet engine (ISA) (Figs. 1,8A,9) is based on PMS 430E112, which is the High Level Date link Layer controller (HDLQ that encodes and decodes, end compares Hie packettsed data as per the RACAS protocol (Table W) and stores valid data in the Train Data Recorder (TDR) (60) (Rg.9) which is interfaced to the pocket engine (PE) (ISA) (Fig.9) through one of its communication serial ports, the (TOR) 60).
For sending identification beacons every 5/15/3Q sec. or so, an Interval Hmer Program is run either in the MCU (34) or in the PE (iSA) to generate a timed interrupt to run the Beacon subroutine programmed in the PE (ISA).
Other than the programming mode, there are two other modes, namefy Safe Mode and Blind
Mode. Safe Mode Is the normal mode when track and status data uploading faculty fe available
andthePE(15A)b"consther")dcntd^
the data stored in TOR (60) IX bank. Blind Mode, though not generally recommended, may be
required for those railway networks whfch have limited route relay interlocking (RfO) (35) (fig.2)
uploading /refreshing facility.
The ACC (34A) (fig. 8A and 9) contains the MCU (14) acting obo us the AntK&Hfckm Controller and carries out the track surveillance and bra&ng action for the entire train carriaae.
The trade and status data signal as uploaded by the RR1 (35) (Ro.2) is terminated at a conventional RRI panel. The invented system installed in the driver's /guard's cabin interfaces with the train control circuitry through optocouites, such as of type TXU53/154/155. These
10

optocouplers are installed on the MCU (34) data input port which scans for track and status data at periodic intervals and loads them into its internal 16 Wt register and refreshes the PE (ISA) with valid trade, and status data as and when uploaded through the RR1 (35) panel. The PE (ISA) in turn updates the received data of track end status only in the MCU (34) for comparison and necessary action. Ultimately it is the MCU (34), which takes the final action for preventing any collision between the trains running on the some track.
Referring to Rg.9, the architecture of the used in the invented system comprises a data input block (51A), a trfock (51) containing the master control unit (MCU) (34) acting as the anti-collision control (ACQ (34A), a block (60) containing the tram data recorder (TOR) (60B) and a number of data memories (60Q, a Mock (15B) containing the packet engine (PE) (15A), a block (56A) containing RF centra! processing Unit (RF CPU) (SB), a Mock (49) containing the receiving-unit (RX) (49A) to which the receiving antenna (52) is connected through antenna selector (AS) (53), a block (50) containing the transmitting unit (TX) (50A) to which the transmitting antenna (54) is connected through power amplifier (PA) (55), a block (55A) containing the program interface for the packet engine(PE) (ISA) and a block (5SB) containing the power supply unit (P/S) (5513) for deriving the system vottages from the 12VDC Train Battery. The said transponders are interconnected by buses (60A) . The directions of the flow of the data between the individual blocks Inside the transponders are Indicated by arrows in Rg.9.
The MCU (34) through iis optoisolated output port drives an eight-column LED array on the Control Desk (1) (fig.l) which displays eight different types of emergent/faulty situations. The signals received from the RSD MATRIX (€1) are used in the application of the invented system for prevention of collisions between the trams running on a common track. Experiments conducted with the invented system on a miniature scale have shown satisfactory performance of the invented system.
The advantages of the invented system over the known systems are:-
1. The building units of the invented system are of compact size and reliable performance in
the field of application i.e. prevention of collision between trains.
2. The invented system is flexible for easily accommodating additional trains/tracks within its
control.
3. The invented system is capable detecting the possibility of collision between the trains
running on a common track from a longer distance 1500-3000 metre compared with the
known systems which can detect such train from a much shorter distance of around 300-
metre or so onfy.
4. The invented system is capable of receiving signals from an approaching train from a
longer distance of 1500-3000 metre even under situations of shorter line of sight (LOS)
caused by the presence bends in the tracks, hills/tall structures near the tracks.
5. The installation of "Static Beacons' at intervals along the tracks and of Station Packet
Terminals' at important railway stations in the invented system provides means for
interaction between the passing trains and the stations with automatic logging of important
traffic data, and issuing advanced warning to the passing trains in case of emergent
situations, such as disruption of the tracks, traffic congestion at the level crossings, etc.
11

I Claim:-
1. A railway collision avoidance system (RACAS) of relatively simple design, compact construction and capable of establishing a reliable connectivity with every train lying within a range of 1500-3000 metre and operating the braking action to avoid collision between trains running on a common track, characterized in that the system comprises :-
C\) a pair of microcontroller based radio signal transponders (23) installed one each in the driver's cabin at the front end (25) and in the guard's cabin at the rear end (24) of a train (26), each said transponder being allotted a unique identity tag corresponding to the name of the train (26) and of the track (27) on which the train is running ;
(ii) a control desk (1) containing an anti-collision control (ACC) (34A) together with other necessary accessories mounted in the driver's cabin;
(ii) Static Beacons (31) installed at intervals along the track (27);
(iv) Station Packet Terminals (33) installed one each at the important railway
stations lying along the track;
The said components (i) to (iv) being arranged to operate in an inter-dependent manner based on the radio signals received/transmitted by the same.
2. The system as claimed in claim 1, characteriozed in that the transponders
in each pair used in a train are of identical configuration, being operable
in a master/slave relation.
3. The system as claimed in claim 2, characterized in that only one of the
transponders in a pair is capable of carrying out the braking action on the
train.
4. The system as claimed in anyone of claims 1 to 3, characterized in that
each transponder of a pair contains a RF part (49), a packet part (15B)
and an anti-collision controller (34A).

5. The system as claimed in claim 4, characterized in that the RF Part
comprises two RF modules one module being used for receiving 0 mode
and the other module for transmitting 1 mode of digital signal, one RX
(receiving) antenna (52), one antenna switcher (53), one TX (transmitting)
antenna (54), one RF CPU (Central Processing Unit) (56) acting as a mixed
signal microcontroller and one RSD (Radio Signal Display) (57).
6. The system as claimed in claim 5, characterized in that each RF module is
of type TRF 6900A based on TRF 6900A Tl, USA, single chip transceiver.
7. The system as claimed in claim 5, characterized in that the RX (receiving)
antenna (52) comprises a 180 degree scan corner reflector having three
resonant dipoles which are switched by the antenna switcher to a low noise
amplifier.
8. The system as claimed in claim 5, characterized in that the TX
(transmitting) antenna (54) comprises a 90 degree angle corner reflector
and is connected to a 5 watt RF amplifier (55).
5.
9. The system as claimed in claim 5, characterized in that the RF CPU (centra! processing
unit) is of type PMS 430E112,EPROM ver and is capable of acting as a mixed signal
microcontroller for controlling all programming (serial) for transmitting, receiving, antenna
switching, data encoding and decoding and RSSI (received signal strength indication).
10. TJie system as claimed in claim 9, characterized in that the RF CPU comprises a 4 K Byte
EPROM memory for storing channel configurations of a particular railway network with FSK
(Frequency shift keying) deviation, LNA gain, TX power, mode 0 and mode 1 settings stored
as default
11. The system as claimed in claim 9, characterized en that the RF CPU is capable of
communicating with MCU (34) through its serial port to ascertain its respective status
(Master/Slave) on boot up and sending RSSI Alert (48) data as and when a signal is
intercepted on the relevant channel.
12. The system as claimed in claim 9, characterized in that the RF CPU Is capable, after bootup,
of carrying out serial programming of the two RF modules, one at a time, and then running
a RSSI program, wherein an ADC module is setup on port 2 to monitor the RSSI slope
voltage from the RF module.
13.The system as claimed in claim 9, characterized in that the RF CPU is capable of outputting an antenna switching logic on one of its ports and running a correlation logic between the digitized RSSI value and the antenna position to make an estimation of the direction of the intercepted signal through RJZZY logic with respect to the head-on /end-on, port side or the star board side of train.
14. The system as claimed in claims 5 and 13 characterized in that the RSD (57) is capable of
displaying the resultant direction with respect to the proximity estimated by a 5-leve! signal
rating of -90 dBm to - 40 d&m i.e. FUZZY logic and carrying out as the track animation and
radio signal display on the control desk (1).
15. The system as claimed fn claim 14, characterized in that the radio signal display (RSD) (57)'
is provided with a panel containing an array of LED/ Panel lamps for displaying 4 bit
decoded data.
16. The system as claimed in any one of claims 1 to 9, characterized in that each transponder
of a pair installed in a train is constructed with a data input block (51A), a block (51)
containing the master control unit (MCU) (34) acting as the anti-collision control (ACC)
(34A), a block (60) containing the train data recorder (TOR) (SOB) together with a number
of data memories (60C), a block (15B) containing the packet engine (PE) (ISA), a block
(56A) containing the RF central processing unit (RF CPU) (56), a block (49) containing the
receiving unit (RX) (49A) to which the receiving antenna (52) is connected through antenna
selector (AS) (53), a block (50) containing the transmitting unit (TX) (50A) to which the
transmitting antenna (54) is connected through power amplifier(PA) (55), a block (55A)
containing the program interface for the packet engine (PE) (ISA), a block (558) containing
the power supply unit (P/S) (55B) for supplying 12 V DC and buses (60A) for
interconnecting said transponders for data flow between the front and rear transponders.
13

17.The system as claimed in any one of the preceding claims, characterized in that the system is operable over a frequency band 850 to 950 MHz with F5K modulation at ± 30 KHz deviation, spectral bandwitdth 150 KHz, and transmitting and receiving frequency
separation 10 MHz in bi-directional full-duplex non-sleep mode at a RF power output of 5
watt: and power supply from 12 V DC battery.
18. The system as claimed in any one of the preceding claims, characterized in that the system is operable from a quasi-connettivity protocol (format) (35A) developed by modification of the known full-connectivity protocol CCIIT, Recommendation X.25.
19.The system as claimed in claim 18, characterized in that the quasi-connecUvity protocol (format) used in the system comprises an unnumbered Information frame (UI) (36) having an additional 1 ms training (learning) sequence (TS) (37) consisting of 26.04 us pulses before every start flag without requiring acknowledgement signal of the receipt of good packets before transmitting the next frame of data.
20.A method of preventing collision between trains running on a common track by using the system as claimed fn any one of the preceding dalms, characterized in tfiat a paired digital transponder operating in the frequency band 915 - 925 MHz is installed in each train, one transponder of Hie pair be&ig installed in the driver's cabin at the front end and the other in the guard's cabin at the rear end of the train for interrogating and replying between tains in a network within a radio range of 1500-3000 metre and producing alarms against any impending head-on or end-on collision between the trains.
21. The method as claimed in claim 20, characterized in that static beacons containing
transponders are installed at intervals along a track and station packet terminals also
containing transponders are installed at important railway stations lying along a track for
upfoad&ig and down loading of data from the trains passing over the track
22. The method as claimed in claims 20 and 21, characterized in that when two trains approach
each other in a head-on or end-on direction, the radio signals transmitted from the
transponders of each train are Intercepted by each train as soon as the two trains are In the
radio range of 1500-3000 metre and the master control unit (MCU) (34) of the transponders
in each train decodes the intercepted signal data, compares the decoded data with the track
data contained therein, transmits the beacon alert signals continuously and thereby brings
the two trains to a half by causing the brakes to act before occurrence of said collision.
THE INVENTION PROVIDES A RAILWAY COLLISION AVOIDANCE SYSTEM (RACAS) WHICH IS OF RELATIVELY SIMPLE DESIGN, COMPACT CONSTRUCTION AND CAPABLE OF ESTABLISHING A RELIABLE CONNECTIVITY WITH EVERY TRAIN LYING WITHIN A RANGE OF 1 500-3000 METRE AND OPERATING THE BRAKING ACTION TO AVOID COLLISION BETWEEN TRAINS RUNNING ON A COMMON TRACK, OPERABLE FROM A QUASI-CONNECTIVITY PROTOCOL (FORMAT) COMPRISING AN UNNUMBERED INFORMATION FRAME HAVING AN ADDITIONAL 1 MS TRAINING (LEARNING) SEQUENCE CONSISTING OF 26.04 US PULSES BEFORE EVERY START FLAG WITHOUT REQUIRING ACKNOWLEDGEMENT SIGNAL OF THE RECEIPT OF GOOD PACKETS BEFORE TRANSMITTING THE NEXT FRAME OF DATA, AND COMPRISES A PAIR OF MICROCONTROLLER BASED RADIO SIGNAL TRANSPONDERS INSTALLED ONE EACH IN THE DRIVER'S CABIN AND GUARD'S CABIN OF A TRAIN, EACH TRANSPONDER BEING ALLOTTED A UNIQUE IDENTITY TAG CORRESPONDING TO THE NAME OF THE TRAIN AND OF THE TRACK ON WHICH THE TRAIN IS RUNNING; A CONTROL DESK CONTAINING AN ANTI-COLLISION CONTROL (ACC) AND OTHER ACCESSORIES MOUNTED IN THE DRIVER'S CABIN; STATIC BEACONS (SB) INSTALLED AT INTERVALS ALONG THE TRACK; AND STATION PACKET TERMINALS (SPT) INSTALLED ONE EACH AT THE IMPORTANT RAILWAY STATIONS LYING ALONG THE TRACK.

Documents:

00448-cal-2001-abstract.pdf

00448-cal-2001-claims.pdf

00448-cal-2001-correspondence.pdf

00448-cal-2001-description(complete).pdf

00448-cal-2001-drawings.pdf

00448-cal-2001-form-1.pdf

00448-cal-2001-form-18.pdf

00448-cal-2001-form-2.pdf

00448-cal-2001-form-3.pdf

00448-cal-2001-letters patent.pdf

448-CAL-2001-(03-01-2012)-FORM-27.pdf

448-CAL-2001-CORRESPONDENCE.pdf

448-CAL-2001-FORM 27.pdf


Patent Number 201106
Indian Patent Application Number 448/CAL/2001
PG Journal Number N/A
Publication Date 19-Jan-2007
Grant Date 19-Jan-2007
Date of Filing 16-Aug-2001
Name of Patentee INDRANIL MAJUMDER
Applicant Address MANDEVILLE GARDENS, APARTMENT 5F, KOLKATA-700019 WEST BENGAL
Inventors:
# Inventor's Name Inventor's Address
1 INDRANIL MAJUMDER MANDEVILLE GARDENS, APARTMENT 5F, KOLKATA-700019 WEST BENGAL
PCT International Classification Number G08 G 1/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA