Abstract:
A system and method for detecting the railway vehicle with a plurality of RFID readers and tags are disclosed. Railway vehicle directional movement on specific track can be detected and updated by the RF communication of the readers and tags. The railway system also includes a computer which monitors a couple of RFID readers for the real-time railway vehicle position. Intelligent detection algorithm is implemented in the reader to identify specific railway vehicle, on a particular track for at least one track in bidirectional or parallel direction. For encoding the data, each RF tag is of unique ID and the RF signal is encrypted.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to the field of railway vehicle detection system, and in particular to a method for arrival and departure detection of the said railway vehicle at railway platform with a plurality of readers and tags over the track. 
       BACKGROUND OF THE INVENTION 
       [0002]    Railway detection in a railway system facilitates the operation of the monitoring of the railway vehicles. Identification of the railway vehicles is the first step to report accurate railway schedule to satisfy passengers. Nowadays, the railway system is extended to a nationwide coverage in which millions of passengers are travelling annually. A systematic approach is needed to report railway schedule especially when accident is happened. A prompt and accurate delay notice announced to the passengers is urgently needed to compensate customers for the postponement. 
         [0003]    As for the railway system, the complexity is another issue causing monitoring and controlling difficulties. Various environmental and railway connections are making the detection and identification process a difficult task. The tracks are typically comprised of two rails in either bidirectional or parallel direction of movement. These characteristics contribute the key reason for the detection predicament. 
         [0004]    It is therefore recommended and desirable to implement a systematic approach and method for detecting a specific railway vehicle, a specific direction and a precise location, especially when the railway vehicle is approaching or departing a station. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    The present invention is directed to at least one pair of RFID reader and active RFID tag for detecting the position and track section of the railway vehicle. In particular, the tag attached on the railway vehicle communicates with the reader installed on the track which precisely updates the arrival and departure schedule. Further, special identification of the railway vehicle on parallel and bidirectional track are focused to report specific railway vehicle. A central computing unit is also served to collect real time arrival and departure information from readers to facilitate the operation of railway system. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1A  shows a top perspective view of RFID reader; 
           [0007]      FIG. 1B  shows a front perspective view of RFID reader; 
           [0008]      FIG. 1C  shows a side perspective view of RFID reader; 
           [0009]      FIG. 1D  shows a side perspective view of active RFID tag; 
           [0010]      FIG. 1E  shows a front perspective view of active RFID tag; 
           [0011]      FIG. 1F  shows a bottom perspective view of active RFID tag; 
           [0012]      FIG. 2  shows a schematic illustration of the installation of RFID reader and active RFID tag on a railway system. 
           [0013]      FIG. 3  shows a schematic illustration of the railway system; 
           [0014]      FIG. 4  shows a timing diagram of the RFID tag identification transmission; 
           [0015]      FIG. 5  shows a communication flow diagram of the present invention; 
           [0016]      FIG. 6  shows a graphical representation of the link quality indicator LQI of the signal strength; 
           [0017]      FIG. 7  shows a flow chart depicting the detection and reporting process of the railway vehicle by reader; 
           [0018]      FIG. 8  shows a flow chart depicting the arrival logic of the reader; 
           [0019]      FIG. 9  shows a flow chart depicting the departure logic of the reader; 
           [0020]      FIG. 10  shows a schematic illustration of the detection logic executed in the central computing unit. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    The following detailed description of present embodiments refers to the accompanying drawings, which illustrate specific embodiments of the invention. Other embodiments having different structures and operations do not depart from the scope of the present invention. The embodiments described herein are also susceptible to variations, modifications and/or additions other than those specifically described and it is to be understood that the invention includes all such variations, modifications and additions which fall within the spirit and scope of the above description. 
         [0022]    Present invention related to the railway vehicle system in which a pair of active RFID (Radio Frequency Identification) reader and tag provides the detection of the railway vehicle. The reader is mounted on the tracks way sleeper or inside the track way drawpit and the tag is mounted underneath the railway vehicle. As illustrated in  FIG. 1A , a top perspective view of the RFID reader is provided. The reader case  101  comprises upper and lower part where four screws are tightened at the corner positions to screw up the case and provide IP67 ingress protection. To operate the reader, power supply and data communication with central computing unit are integrated with two pairs of cable, which are a twisted pair RS-485 cable and a pair of DC power supply cable, within an armour cable. The armour gland  102  provides IP67 ingress protection allowing the reader to be installed at adverse environment. 
         [0023]      FIG. 1B  illustrates a front perspective view of the reader. The lower part  103  and upper part  104  of the case can be shown in the front view. Further, the armour gland  105  placed in front represents the direction of the installation of the reader on the track. 
         [0024]      FIG. 1C  illustrates a side perspective view of the reader. Likewise, the side view does not depart from the aforementioned description as the lower part  106 , upper part  107  and armour gland  108  are shown in this figure. 
         [0025]      FIG. 1D  illustrates a side perspective view of the active RFID tag. In the preferred embodiment, the tag is mounted underneath at the front of the railway vehicle to facilitate signal transmission. Similar to the RFID reader, the tag comprises an upper case  109  and a lower case  110  in the same way and case of tag provides IP67 ingress protection. An IP67 ingress protection connector  111  is implemented at the bottom of the tag. A pair of power supply cable is plugged in the connector  111  for power supply. The vehicle identity transmitted from the tag is encrypted to enhance security. 
         [0026]      FIG. 1E  illustrates a front perspective view of the tag. Likewise, the front view does not depart from the aforementioned description as the upper case  112 , lower case  113  and IP67 ingress protection connector  114  are shown in this figure. 
         [0027]      FIG. 1F  illustrates a bottom perspective view of the tag. As shown in the figure, the IP67 ingress protection connector  116  is located underneath of the tag for the power supply purpose. 
         [0028]      FIG. 2  is a schematic illustration of the installation of RFID tag and reader. A preferred installation is shown in the front part of the railway vehicle  201  where the tag  202  is mounted underneath for shortening the distance of signal transmission. The reader  203  is located on the track in coordination with the tag position. 
         [0029]      FIG. 3  is a system overview according to the present invention. A track section comprising two platforms  301 ,  302  are demonstrated for the scenario of intermediary station where the railway directions are in opposing direction  315 ,  316 . In real railway system, curvature of track section, railway direction, platform location and track structure are subjected to variations or modifications according to the environment. The present invention can also be applied to any track section in the railway system. The RFID readers  306 ,  307 ,  308 ,  309  are powered by DC power supply  313  and ground  314 . In particular, the readers  306 ,  307 ,  308 ,  309  can be characterized as an arrival and/or a departure reader. The assignment of the pair of arrival and departure readers depends upon the railway direction. In the preferred scenario, readers  306  and  308  are named to be the arrival readers while readers  307  and  309  are named to be the departure readers. For every track, a pair of arrival and departure readers is installed where the arrival readers  306 ,  308  are placed in front of the corresponding platform and the departure readers  307 ,  309  are placed at the end of the corresponding platform. 
         [0030]    For example, when the railway vehicle arrives at platform  1   301 , the RFID signal from the tag on the said vehicle can be received by the arrival reader  306  in which a unique identity for each railway vehicle is recorded in the signal. After the reader  306  receives the polling message from the central computing unit  312 , the reader  306  replies the central computing unit  312  with the arrived vehicle identity through the RS-485 cables. Likewise, when the railway vehicle departs from platform  1   301 , the reader  307  replies central computing unit  312  with the departed vehicle identity. It is noted that the RS-485 cable and DC power supply cable  314 ,  315  are embedded in a 4-wire armour cable  311  in the aforementioned description. Along the bidirectional track section, a couple of arrival and departure readers  306 ,  307 ,  308 ,  309  are connected as a network by a bus topology  310  wherein the data communication and power supply are transmitted over the network. A T-join is illustrated in the bus topology  310  in the current scenario. 
         [0031]      FIG. 4  is a timing diagram of the identification signal from the active RFID tag. The peak  401 - 406  represents the transmission of identification signal wherein the period of the identification signal is relatively short. In the current example, the period is estimated to be around 2 ms. In the timing diagram, it is shown that the identification signal transmits repeatedly and periodically after a delay of 80-110 ms as an example. During the delay, the signal transmission is suspended after the signal transmission. For every delay, the period is randomized within the range of 80-110 ms so as to avoid interference in the proximity of the tag signal, whereby every other delay  407 - 411  varies slightly as shown in the current example. This type of signal generation is best adapted to at least one track in either bidirectional or parallel direction. 
         [0032]      FIG. 5  is a communication flow of the railway system. The railway system comprises active RFID tag on the railway vehicle  501 , RFID readers on the track  502 ,  504  and central computing unit  503 . As a preferred example, the diagram depicts how system devices communicate within the railway system. As an example, reader  1   502  acts as an arrival reader while reader  2   504  acts as a departure reader. When a railway vehicle is approaching  511  the arrival reader  502 , the tag  501  broadcasts identification signals  505  periodically and repeatedly in the wireless RF medium. Whenever the reader  1   502  receive the identification signals  505 , the reader  502  processes the signal in identifying the tag identify, link quality (signal strength) and the time of reception in an arrival list. A new list is constructed as a railway vehicle is detected wherein the attributes are stored and processed in the list. Once the attributes meet the requirement of arrival, an arrival message  513  will be created in a message buffer. 
         [0033]    On the other hand, the central computing unit  503  polls arrival or departure request to the reader by the RS-485 network. A reply  508  will be responded with a message to the central computing unit  503 . In normal occasion, the reply  508  is usually reporting no vehicle approaching. Once the railway vehicle is proved to be approaching  506 , the said arrival message  513  will be replied to the central computing unit  503 . Afterwards, the reply message  514  resumes to report no railway vehicle is approaching. 
         [0034]    As for the central computing unit  503 , the departure reader  504  should receive polling message in the RS-485 network as the central computing unit  503  polls every reader in the network. In this preferred example, the reader  504  does not receive any identification signal  505  from the tag  501  thus reporting no railway vehicle is departing. 
         [0035]      FIG. 6  is a graphical representation of the link quality (signal strength) received in the RFID reader. In the aforementioned description, the said tag transmits signals repeatedly along the track. As for the reader, the link quality received varies as the railway vehicle moves. When the railway vehicle is approaching the reader, the receiver of the reader starts detecting the signal  601 . The link quality increases exponentially  602  as the railway vehicle continuously travels along the reader track section. When the tag of railway vehicle is just past the reader, a peak link quality  604  is expected representing the railway vehicle is located at the reader. In the preferred embodiment, it is noted that the link quality drops drastically  606  when the railway vehicle is beyond the reader. Signal fading due to the interference by machinery in the bottom part of the railway vehicle whereby metallic absorption accounts for the rationale behind this significant drop. As a result, the graphical representation shows an unsymmetrical curve. Consequently, the link quality disappears  607  as the railway vehicle is out of the detection range. 
         [0036]    The characteristics of the arrival and departure readers differentiate with the trigger level setting. For arrival reader, a preferred trigger level  603  of link quality is preset prior to the peak  604  indicating the railway vehicle is meters within the reader. For departure reader, the preferred trigger level  605  is preset beyond the peak  604  indicating the railway vehicle is meters away from the reader. 
         [0037]      FIG. 7  is a detailed flow chart representation of the reader. Generally speaking, the reader handles three functions repeatedly: Logical decision, signal processing and polling response. 
         [0038]    The reader starts  701  and checks the tag record in the first process. As for operating the logical decision of arrival or departure, tag record has to be ensured  702  before logical operation. Then, an identification of arrival or departure nature  703  is processed before applying arrival  704  or departure  705  logic respectively. 
         [0039]    Afterwards, the RF receiver listens to the identification signal  706 . If a signal is received in which the link quality (signal strength) is above an acceptable level  707 , the tag ID is extracted from the signal to check whether the tag ID is existed  708 . The accepted level stated can be set by the railway system administrator. An update of tag record with timing  709  is performed for an existing tag ID while a new addition of tag record with timing  710  is performed for a new tag ID. 
         [0040]    On the other hand, the central computing unit polls periodically to the reader. The reader listens to the polling message  711  and responds to the central computing unit computer based on the reporting buffer  712 . The reader loops these three functions repeatedly achieving the detection and reporting purposes. 
         [0041]      FIG. 8  is a flow chart representation of the arrival reporting logic where the logic comprises a few checking processes. The arrival logic begins  801  by checking whether the tag has been expired  802  since an expired tag record has to be removed  803 . After a period of time which can be set by railway administrator, the tag is considered as expired if no other tag record is received. If the tag is not expired, a flag indicating whether the tag has been reported is checked  804  to ensure the tag record does not add to the buffer. The checking is to guarantee one and only one report is allowed for a tag record. Once reported, the arrival logic processes will be skipped and returned to the operation of the reader  807 . If the tag record is not reported, the list of the tag record is to be examined if there are enough records  805  representing an arrival message to be set in the report buffer  806 . In this process, an arrival list storing the tag records for specific tag ID is examined. 
         [0042]      FIG. 9  is a flow chart representation of the departure reporting logic where the departure logic is similar to the arrival logic. The departure logic begins  901  by checking whether the tag has been expired  902  since an expired tag record has to be removed  903 . After a period of time which can be set by railway administrator, the tag is considered as expired if no other tag record is received. If the tag is not expired, a special reporting timing is applied to check whether it is the right time to report. The reporting sequence for departure is designed to identify the railway vehicle has past the reader for a period of time. Similarly, when it is the time to report, a flag indicating whether the tag has been reported is checked  905  to ensure the tag record does not add to the buffer. The checking is to guarantee one and only one report is allowed for a tag record. Once reported, the departure logic processes will be skipped and returned to the operation of the reader  908 . If the tag record is not reported, the list of the tag record is to be examined if there are enough records  906  representing a departure message to be set in the report buffer  907 . In this process, a departure list storing the tag records for specific tag ID is examined. 
         [0043]    After the readers have detected and reported to the central computing unit, two approaches are supported by the central computing unit to report the position of the vehicle to the railway system, which can be done by either direct reporting or associated reporting approach.  FIG. 10  is a preferred scenario showing two approaches for an example of bidirectional intermediate station in the central computing unit. The approaches also apply to other stations where parallel tracks are present in the terminus or other scenarios. The object is to identify specific railway vehicle with direction on recognizable track sections in proximity. In this preferred scenario, a railway vehicle  1003  is approaching the station in the direction as shown  1006  where a couple of readers  1008 - 1011  are located at platform  1  and  2   1001 ,  1002  accordingly. Likewise, readers  1008 ,  1010  are named as arrival readers and readers  1009 ,  1011  are named as departure reader. 
         [0044]    In direct reporting approach, the tag mounted underneath the railway vehicle  1003  broadcasts RF signal periodically. Both arrival reader  1008  and departure reader  1011  are capable of receiving the RF signal. A dilemma of which reader collects the respective railway vehicle signal on the respective track is to be analyzed. As the readers  1008 ,  1011  clearly identify the unique ID of the railway vehicle  1003 , the data reported to the railway system  1014  should be able to spot these unreasonable reports wherein both tracks report the same tag signal at the same time. Therefore, systematic railway system  1014  determines the arrival reader  1008  is receiving the arrival signal according to railway schedule while the departure reader  1011  receiving the departure signal is not true indeed. 
         [0045]    In the associated reporting approach, the aforementioned dilemma can also be solved by the preferred detection logic in the central computing unit  1013 . On the same preferred scenario, the central computing unit  1013  first polls the arrival reader  1010  to check whether any railway vehicle has been arrived at platform  2   1002  on track  1005 . The rationale behind this polling analysis is that when there is a departure, there must be an assumed prior arrival within a reasonable time period. It is be understood that if reader  1010  did not report arrival, then the RF signal received in departure reader  1011  must be from alternative track section. The arrival reader  1008  is receiving the correct signal. Therefore, vehicle identity detected by reader  1008  will be reported to the railway system  1014 . 
         [0046]    If the arrival reader  1010  did report prior arrival, it is understood that the RF signal received in departure reader  1011  is receiving the corresponding departure and the arrival reader  1008  is reporting fault indeed.