Patent Publication Number: US-7222003-B2

Title: Method and computer program product for monitoring integrity of railroad train

Description:
FIELD OF THE INVENTION 
   The present invention is generally related to railroad trains, and more particularly, to techniques for monitoring integrity of a railroad train and determining passage of the train relative to a plurality of virtual blocks defined along a rail track over which the train travels. 
   BACKGROUND OF THE INVENTION 
   Traditional rail traffic signal systems have used an extensive array of wayside equipment to control railway traffic and maintain safe train separation distances. In these traditional systems railway control is achieved by detecting the presence of a train, determining a route availability for each train, conveying the route availability to a train&#39;s crew, and controlling the movement of the train in accordance with the route availability. 
   The presence of a train is typically detected directly through a sensor device, or track circuit, associated with a specific section of the rails, referred to as a block. The presence of a train causes an impedance change in a block&#39;s track circuit. In this manner, the occupancy of each block is determined. Vital decision logic is employed, utilizing the block occupancy information in conjunction with other information provided, such as track switch positions, to determine a clear route availability for trains. Traditional railway systems require the installation and maintenance of expensive apparatus on the wayside for communicating route availability to approaching trains. The wayside equipment physically displays signals, or aspects, that are interpreted by a crew on board a train approaching the signaling device. Thus, the interpretation of signal aspects can be subject to human error through confusion, inattention or inclement weather conditions. 
   An alternative to conventional track circuit-based signaling systems are communication-based train control (CBTC) systems. These train control systems generally include a computer at one or more fixed locations for determining the movement, authority and/or constraints applicable to each specific train. The computer then transmits this train-specific information in unique messages addressed or directed to each individual train. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Advantages of the present invention will be more apparent from the following description in view of the accompanying drawings where: 
       FIG. 1  is a block diagram of an exemplary system for monitoring integrity of a railroad train and determining passage of the train relative to a plurality of virtual blocks. 
       FIG. 2  show a temporal sequence of diagrams representing exemplary operational situations in connection with a train equipped with a system embodying aspects of the present invention 
       FIG. 3  is collectively made up of  FIGS. 3A and 3B  and illustrates a fault tree of exemplary failure modes that could lead to an erroneous determination as to whether an entire train has cleared a boundary for a respective one of the virtual blocks. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Before describing in detail an exemplary system in accordance with aspects of the present invention, it should be observed that such aspects reside primarily in a novel structural combination of standard sensing devices and computational modules configured to process data from such sensing devices and not necessarily in the particular specific configurations of such devices. Accordingly, the structure, control and arrangement of these standard devices have been illustrated in the drawings by readily understandable block diagrams which show just those specific details that are considered pertinent to the present invention, so as not to burden the disclosure with superfluous details that will be readily apparent to those skilled in the art having the benefit of the description herein. Thus, the block diagram illustrations of the figures may not necessarily represent the physical structural arrangement of the exemplary system, but are primarily intended to illustrate the major components of the system in a convenient functional grouping, whereby the present invention may be more readily understood. 
     FIG. 1  is a block diagram of an exemplary onboard system  8  for monitoring integrity of railroad train  10  and determining passage of the train relative to a plurality of virtual blocks, such as may be defined by wireless transmissions along a section of track over which the train travels. Train  10  is generally made up of a plurality of railcars and one or more locomotives that when interconnected to one another constitute a single train. The train generally includes a pneumatic line  18  interconnected among railcars and locomotives therein, as may be used for driving pneumatically driven equipment, such as air brakes. The virtual blocks provide safeguards for the travel of the train relative to other trains on the section of the track when there is a shared use of the section of track. As used herein virtual blocks refer to blocks as may be derived by wireless transmissions without the utilization of track circuits. 
   Aspects of the present invention recognize that there may be a plurality of failure modes that can affect a determination of train integrity, such as whether sections of the train have become separated from one another (train separation), that could lead to an erroneous determination of a train having actually cleared a boundary of a respective one of the virtual blocks. For example, if a blockage in a pneumatic line (e.g., an airline) that extends along the entire length of the train were to occur, just monitoring a front airline pressure at a head-of train (H.O.T.) location may not be able to detect a train separation condition since a blockage upstream of the separation point would prevent quick detection of pressure loss in the airline. 
   Similarly, just monitoring motion of an end-of-train (E.O.T.) location may not be able to detect a train separation condition. For example, the E.O.T. may continue to move with forward motion even though a train separation has occurred. Thus, aspects of the present invention identify such failure modes and build up multiple detection layers through the use of multiple sensing devices configured to monitor a different parameter and generate data useful for evaluating whether at least one of the failure modes has occurred. The foregoing combination of data results in a highly reliable system for monitoring and determining passage of a train relative to the plurality of virtual blocks. 
   In one exemplary embodiment, system  8  may include a H.O.T. transceiver  12  in communication (e.g., wireless communication) with a suite of E.O.T. sensing devices  14  by way of an E.O.T. transceiver  15 . For example, the suite of sensing devices  14  may include an E.O.T. pressure-sensing device  16  pneumatically coupled to the pneumatic line  18 . The suite of sensing devices  14  may further include a motion sensor  20 , such as an accelerometer, and a global positioning system receiver  22 . 
   In one exemplary embodiment, system  8  may include a suite of H.O.T. sensing devices  30 , such as one or more pressure sensing devices  32  and  34  as may be pneumatically coupled to pneumatic line  18 . It will be appreciated that H.O.T. sensing devices that may already be part of a lead locomotive, such as speed and position sensing devices, or calculations performed by an onboard controller, may be used for evaluating E.O.T. data in combination with H.O.T. data. 
   A database  40  (or any suitable digital data storage device) may be used for storing a plurality of rules for relating the data collected at the head-of-train location to the data collected at the end-of-train location. These rules may be configured to reduce a probability of making an erroneous determination as to whether the entire train has cleared a boundary for a respective one of the virtual blocks. An example of a straightforward rule may be as follows: If H.O.T. pressure is maintained and a loss of E.O.T. pressure is sensed, then this combination of information may indicate lack of train integrity, even though a blocked airline condition may be present. Another exemplary rule may be as follows: If the magnitude of E.O.T. GPS-based speed is consistent with the magnitude of H.O.T. speed and accelerometer based motion indicates E.O.T. travel motion opposite to H.O.T. travel direction, then this combination of information may indicate lack of train integrity. For example, one separated section of the train could be moving opposite to another separated section of the train within a same range of speed. 
   A processor  42  is configured to process the data collected at the end-of-train and at the head-of train locations using the rules in database  40  to determine whether the entire train has actually cleared a respective one of the virtual blocks. In the event such a determination indicates clearance of the respective block, processor  42  may declare that virtual block as being unoccupied and thus available for another train to enter the block. Conversely, in the event such determination indicates a lack of clearance of the respective block, processor  42  may declare the virtual block as being occupied and thus unavailable for another train to enter the block. The foregoing block status information may be communicated to a train operator by way of a user interface  44 . 
   In accordance with other aspects of the present invention, based on the results of the determination performed by processor  42 , transceiver  12  (or any suitable onboard communication device) may be automatically commanded (without requiring any action by onboard personnel) by processor  42  to communicate to an offboard location, such as wayside equipment  50 , and/or a centralized traffic control system  52 , a present status of the virtual block as to whether or not such block is available for another train, or whether the system is unable to make a determination within an acceptable range of confidence and therefore communicate a cautionary status regarding one or more virtual blocks. This ability for automatically communicating virtual block status and/or to communicate a cautionary status in connection with any such blocks is particularly advantageous since it avoids the possibility of errors due to human intervention, such as may occur if an onboard operator has to interpret and report situational occurrences. Moreover, this conveniently reduces tasks for onboard personnel whom otherwise would have to perform actions for communicating block status to the offboard location. 
     FIG. 2  represents a temporal sequence of diagrams representing exemplary operational situations in connection with a train equipped with a system embodying aspects of the present invention. Diagram  50  shows a train  52  on a track  54 , where lines  56  represent boundaries for a plurality of virtual blocks derived using communication based-techniques. Track Section  55  represents a side section adjacent to track  54  that may also benefit from the innovations provided by the present invention. For an example of such communication-based techniques, reference is made to U.S. Pat. No. 6,459,965, titled “Method For Advanced Communication-Based Vehicle Control”, which is herein incorporated by reference. A line  58  represents a last known rear location of train  52 , as verified by processor  42  in combination with a last E.O.T. data update. In diagram  50 , virtual blocks a, b and c (as represented with the underlying “xxxxx” letter pattern) may be designated as occupied and thus unavailable for other trains. 
   In diagram  60 , a line  62  represents a request (e.g., polling) of new E.O.T. data. Note that blocks a, b and c continue to be designated as occupied as well as blocks d, e and f, since the requested E.O.T. data has not been received and processed by processor  42 . 
   In diagram  70 , a line  72  represents a new known rear location of train  52 , as verified with the new E.O.T. data update. Note that in this case, virtual blocks a, b and c are now designated as clear (as represented by the “yyyyy” letter pattern). In the event the system is unable to satisfactorily verify train integrity, then blocks a, b and c would be designated as unverified (as represented by the question mark pattern) in diagram  80  and this loss of integrity information would be automatically communicated in the form of a cautionary message to the off-board location, such as traffic control system  52  ( FIG. 1 ), where an appropriate action would be taken to communicate that caution information to other trains and/or independently determine the status of such blocks. It is contemplated that in one exemplary embodiment a next approaching train (upon receipt of a cautionary message from the traffic control system and having slowed down to a sufficiently safe train speed) may proceed to make a determination as to the status of the virtual blocks in question. For example, an operator in the next approaching train may visually verify as to the status of such virtual blocks. This information in turn would be communicated back to the traffic control system and/or would be used for setting any applicable wayside equipment to display an appropriate condition, such as whether or not the blocks are clear for safe train passage. 
     FIG. 3 , collectively made up of  FIGS. 3A and 3B , is a fault tree illustrating exemplary failure modes that could lead to an erroneous determination as to whether an entire train has cleared a boundary for a respective one of the virtual blocks. The fault tree may be a multi-layered tree and configured to evaluate aspects of the present invention regarding combined utilization of E.O.T. data together with H.O.T. data to meet a required safety level. The fault tree comprises elements that represent potential faults, such as enclosed by blocks interconnected by suitable logical connectors, e.g., OR and AND logical operators. Circles  80  and  82  represent interconnecting nodes for  FIGS. 3A and 3B . 
   One exemplary manner of clearing block occupancy may be as follows:
         When processor  42  has estimated (for example, within a predefined range) the E.O.T. train location relative to a virtual block boundary, processor  42  through H.O.T. transceiver  12  will poll the E.O.T. transceiver  15  for an information update. The information update may include the following data:
           end-of-train air pressure from pressure sensing device  16 ,   GPS derived end-of-train speed from GPS receiver  22 ,   Accelerometer derived train motion status (e.g., stopped, forward motion, or reverse motion) from accelerometer  20 .   Processor  42  may clear the block occupancy provided the following conditions are satisfied:   the predefined range for E.O.T. location is determined to be past the block boundary,   the reported end-of-train air pressure is greater than a predefined minimum value for a given train type,   the reported end-of-train GPS-based speed is consistent with a processor calculated H.O.T. speed, and   the reported end-of train motion status is consistent with a processor calculated H.O.T. motion status.   
               

   It is contemplated that one may provide a suitable margin that accounts for train position measurement uncertainty (e.g., worst case H.O.T. location) plus the total time delay associated with the polling of the E.O.T. and the receipt of a response.
         If processor  42  does not receive the requested information update from the E.O.T., then the block will remain occupied until the successful receipt of a subsequent requested information update.       

   An exemplary manner of supervising train integrity may be as follows:
         Assuming one has initially established appropriate train length and train integrity, processor  42  monitors the H.O.T. pressure sensing devices  32  and  34 . Processor  42  may determine that there has been a loss of train integrity when either of the two pressure measurements indicates a loss of air pressure below a specified threshold value.   If the processor  42  does not receive the requested E.O.T. data for a specified number of consecutive block clearing attempts, then processor  42  will declare a loss of train integrity. It is contemplated that one could reduce the operational impact of poor E.O.T. communication at specific track locations (e.g., tunnel, bridges) by not placing virtual block boundaries at those locations.   In addition to polling the E.O.T. for information as part of each block boundary clearing process, processor  42  is configured to ensure that the E.O.T. transceiver is periodically polled at some specified frequency.   Processor  42  will also monitor the end-of-train air pressure as part of the train integrity supervision function. Processor  42  may determine that there has been a loss of train integrity when a value of greater than a predefined threshold value (as defined for a given train type) is not received from the E.O.T. for longer than a specified period of time.   Processor  42  will monitor the end-of-train accelerometer-based motion status. Processor  42  may determine that there has been a loss of train integrity when a reported status that is consistent with a processor  12  calculated status is not received from the E.O.T. for longer than a specified period of time.   Processor  42  will monitor end-of-train GPS-based speed. Processor  42  will conclude that there has been a loss of train integrity when a reported speed that is consistent with a processor  12  calculated speed is not received from the E.O.T. for longer than a specified period of time.       

   Analytically-derived Exemplary Probabilities Regarding An Undetected Train Break Condition. 
   
     
       
         
             
             
             
           
             
                 
                 
             
           
          
             
                 
               H.O.T. Data Monitoring Only 
               = 5.7 × 10 − 6 
             
             
                 
               E.O.T. Data Monitoring Only 
               = 2.1 × 10 − 8 
             
             
                 
               Combined H.O.T. and E.O.T. Data 
               = 1.2 × 10 − 13 
             
             
                 
                 
             
          
         
       
     
   
   Accordingly, it is expected that the combined probability calculation will conservatively meet typical requirements, such as required by
 
Safety Integrity Level (SIL) 4 train safety standards=1×10−10
 
   Aspects of the invention can also be embodied as computer readable code on a computer readable medium. The computer readable medium is any data storage device that can store data, which thereafter can be read by a computer system. Examples of computer readable medium include read-only memory, random-access memory, CD-ROMS, DVDs, magnetic tape, optical data storage devices. The computer readable medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. 
   Based on the foregoing specification, the invention may be implemented using computer programming or engineering techniques including computer software, firmware, hardware or any combination or subset thereof. Any such resulting program, having computer-readable code means, may be embodied or provided within one or more computer-readable media, thereby making a computer program product, i.e., an article of manufacture, according to the invention. The computer readable media may be, for example, a fixed (hard) drive, diskette, optical disk, magnetic tape, semiconductor memory such as read-only memory (ROM), etc., or any transmitting/receiving medium such as the Internet or other communication network or link. The article of manufacture containing the computer code may be made and/or used by executing the code directly from one medium, by copying the code from one medium to another medium, or by transmitting the code over a network. 
   An apparatus for making, using or selling the invention may be one or more processing systems including, but not limited to, a central processing unit (CPU), memory, storage devices, communication links and devices, servers, I/O devices, or any sub-components of one or more processing systems, including software, firmware, hardware or any combination or subset thereof, which embody the invention as set forth in the claims. 
   User input may be received from the keyboard, mouse, pen, voice, touch screen, or any other means by which a human can input data to a computer, including through other programs such as application programs. 
   One skilled in the art of computer science will easily be able to combine the software created as described with appropriate general purpose or special purpose computer hardware to create a computer system or computer sub-system embodying the method of the invention. 
   While the preferred embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to those of skill in the art without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.