Patent Publication Number: US-11021180-B2

Title: Railway road crossing warning system with sensing system electrically-decoupled from railroad track

Description:
BACKGROUND 
     1. Field 
     Disclosed embodiments are generally related to railway road crossing warning systems and, more particularly, to a system for detecting presence and movement of a railway vehicle within a detection area of a railroad track, and control of the railway road crossing warning system using a railway-vehicle sensing system electrically-decoupled from the railroad track. 
     2. Description of the Related Art 
     Railway road crossing warning systems provide protection of crossings by detecting train presence and motion, and activating crossing warning devices such as bells, lights, crossing gate arms, within a specified time period before the arrival of a train at the road crossing. Train presence near the crossing and motion towards/away from the crossing has been traditionally detected by transmitting electrical signals on the railroad tracks. For example, train presence may be detected by receiving a voltage as propagated over the railroad track, as a transmission medium. Train motion may be determined by monitoring the current and voltage applied to the railroad track to determine the impedance of the track, from the crossing to the train. See U.S. Pat. No. 7,254,467 and International Publication Number WO 2014/059487 A1 for respective examples of railway road crossing warning systems. 
     BRIEF DESCRIPTION 
     One disclosed embodiment is directed a railway road crossing warning system including a railway-vehicle sensing system electrically-decoupled from a railroad track where a railway-vehicle travels. A railway road crossing control unit is responsive to at least one signal received from the railway-vehicle sensing system to process the received at least one signal and determine whether the railway-vehicle is in a detection area of the railroad track. The railway road crossing control unit is configured to activate at least one crossing warning device upon determining, based on the received at least one signal, a presence of the railway-vehicle in the detection area of the railroad track, and is further configured to deactivate said at least one crossing warning device upon determining, based on the received at least one signal, an absence of the railway-vehicle from the detection area of the railroad track. 
     Another disclosed embodiment is directed to a railway road crossing warning system including a railway road crossing control unit that may be selectively set by a mode selector unit to a primary mode of operation or a secondary mode of operation. In the primary mode of operation, the railway road crossing control unit is responsive to a primary activation signal received from a primary activation-signal source, such as a positive train control (PTC) system, to activate the at least one crossing warning device. 
     In the event the activation signal from the primary activation-signal source is not available, the railway road crossing control unit is set by the mode selector unit to the secondary mode of operation. In the secondary mode of operation, the railway road crossing control unit is responsive to at least one signal received from a secondary activation-signal source. 
     The secondary activation signal-source comprises a railway-vehicle sensing system electrically-decoupled from a railroad track where a railway-vehicle travels. The railway road crossing control unit is configured to process the received at least one signal and determine whether the railway-vehicle is within a detection area of the railroad track. The railway road crossing control unit is configured to activate the least one crossing warning device upon determining, based on the received at least one signal, a presence of the railway-vehicle in the detection area of the railroad track, and is further configured to deactivate the at least one crossing warning device upon determining, based on the received at least one signal, an absence of the railway-vehicle from the detection area of the railroad track. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top-level schematic of a railway road crossing warning system embodying disclosed concepts. 
         FIGS. 2-4  respectively illustrate an example flow sequence of events in connection with a railway road crossing warning system involving one non-limiting embodiment of a disclosed railway-vehicle sensing system. 
         FIGS. 5-7  respectively illustrate an example flow sequence of events in connection with a railway road crossing warning system involving another non-limiting embodiment of a disclosed railway-vehicle sensing system. 
         FIGS. 8-10  respectively illustrate an example flow sequence of events in connection with a railway road crossing warning system involving still another non-limiting embodiment of a disclosed railway-vehicle sensing system. 
     
    
    
     DETAILED DESCRIPTION 
     Without limiting disclosed embodiment to any particular jurisdiction, in view of requirements mandated in the United States by the Federal Railroad Administration (FRA), the railroad industry in the United States has made a substantial investment in the infrastructure needed to implement a Positive Train Control (PTC) system. Consequently, the railroad industry has pursued applications to leverage that investment into other areas beyond the original mandate of train control to increase safety and operating efficiency in such other areas. One known application is to use train position and speed knowledge obtained by the PTC system to activate the grade crossing warning devices. This eliminates wired connections to the track rails and makes the system robust in the presence of changing weather and avoids variable electrical ballast conditions that otherwise would develop across the rails. This also makes the system impervious to alternating current (AC) electrical interference that can develop across the rails. 
     The inventors of the present invention have recognized some practical limitations regarding the foregoing application of the PTC system. For instance, in this application of the PTC system, there is no longer the ability to use traditional island circuits to activate the grade crossing warning devices. This is not an issue so long as the PTC system is fully functional; however, there will be instances when the PTC system may not be available for any one of a variety of reasons. Based on typical designs of current grade crossing warning systems, in these instances, one may need to rely on cumbersome techniques for activating the grade crossing warning devices in the absence of a PTC actuating signal. These techniques may involve train stoppage, which decreases efficiency of railroad operation regarding both timeliness and energy consumption. Additionally, train stoppage increases a possibility of cargo damage on the train. 
     In view of such recognition, the present inventors propose an innovative technical solution involving no wired connections to the track rails. The proposed technical solution maintains robustness in the presence of changing weather and avoids variable electrical ballast conditions that otherwise would develop across the rails, while providing a cost-effective and reliable backup capability for a PTC-started crossing system. 
     In the following detailed description, various specific details are set forth in order to provide a thorough understanding of such embodiments. However, those skilled in the art will understand that disclosed embodiments may be practiced without these specific details that the aspects of the present invention are not limited to the disclosed embodiments, and that aspects of the present invention may be practiced in a variety of alternative embodiments. In other instances, methods, procedures, and components, which would be well-understood by one skilled in the art have not been described in detail to avoid unnecessary and burdensome explanation. 
     Furthermore, various operations may be described as multiple discrete steps performed in a manner that is helpful for understanding embodiments of the present invention. However, the order of description should not be construed as to imply that these operations need be performed in the order they are presented, nor that they are even order dependent, unless otherwise indicated. Moreover, repeated usage of the phrase “in one embodiment” does not necessarily refer to the same embodiment, although it may. It is noted that disclosed embodiments need not be construed as mutually exclusive embodiments, since aspects of such disclosed embodiments may be appropriately combined by one skilled in the art depending on the needs of a given application. 
     The terms “comprising”, “including”, “having”, and the like, as used in the present application, are intended to be synonymous unless otherwise indicated. Lastly, as used herein, the phrases “configured to” or “arranged to” embrace the concept that the feature preceding the phrases “configured to” or “arranged to” is intentionally and specifically designed or made to act or function in a specific way and should not be construed to mean that the feature just has a capability or suitability to act or function in the specified way, unless so indicated. 
       FIG. 1  is a top-level schematic of a railway road crossing warning system  10  embodying disclosed concepts. As will be appreciated by those skilled in the art, railway road crossing warning system  10  may be used in connection with a road crossing  11  that intersects a portion of a railroad track  12 , such as may be made up of a pair of track rails  13  and  14 . For the sake of simplicity of illustration, the figures illustrate just a singular railroad track disposed perpendicular relative to the road crossing. It should be appreciated that disclosed embodiments are not limited to singular railroad tracks, or to any particular geometric arrangement between the railroad track and the road crossing. 
     In one non-limiting embodiment, a crossing control system  16  includes a railway road crossing control unit  18  that may be selectively set by a mode selector unit  20  (labeled S/U in the drawings) to a primary mode of operation or a secondary mode of operation. In the primary mode of operation, the railway road crossing control unit is responsive to a primary activation signal  21  received from a primary activation-signal source  22 , as may be generated, without limitation, from a positive train control (PTC) system, to activate at least one crossing warning device  24 , as may include bells, lights, crossing gate arms, etc. 
     In this primary mode, when a railway-vehicle  30 , e.g., a train, approaches crossing  11 , continuous location-tracking and time of arrival calculations performed by the PTC system may be used to generate primary activation signal  21  conveyed to railway road crossing control unit  18  and in turn activate crossing warning device/s  24  at an appropriate time, such as may be configured to ensure an optimum advanced activation time. 
     In the event primary activation signal  21  from primary activation-signal source  22  is not available, (e.g., PTC system down) railway road crossing control unit  18  is set by mode selector unit  20  to the secondary mode of operation, where railway road crossing control unit  18  is responsive to at least one signal  25  received from a secondary activation-signal source  26 . 
     The secondary activation signal-source includes a railway-vehicle sensing system  28  electrically-decoupled from railroad track  12 , where railway-vehicle  30  travels. Non-limiting examples may be railway-vehicles, such as a train, involving a series of connected railway-vehicles, that runs along railroad track  12  to transport cargo or passengers. Other non-limiting examples of railway-vehicles may be discrete railway-vehicles, such as may be used for maintenance of the railroad tracks and other applications. 
     As elaborated in greater detail below, railway road crossing control unit  18  may be configured to process the received signal/s  25  from railway-vehicle sensing system  28  and determine whether railway-vehicle  30  is within a detection area of the railroad track. It will be appreciated that the size and configuration of the detection area may be appropriately tailored based on the needs of a given application. 
     Without limitation, railway road crossing control unit  18  may be configured to activate crossing warning device/s  24  upon determining, based on the received signal/s  25 , a presence of the railway-vehicle in the detection area of the railroad track. Railway road crossing control unit may be further configured to deactivate crossing warning device/s  24  upon determining, based on the received signal/s  25 , an absence of railway-vehicle  30  from the detection area of the railroad track. The description below will proceed to describe various disclosed embodiments of railway-vehicle sensing system  28  that may be used alone, or in combination, if so desired. 
       FIGS. 2-4  respectively illustrate an example flow sequence of events in connection with one non-limiting embodiment of a disclosed railway-vehicle sensing system  28  ( FIG. 1 ), such as may involve a wireless telemetry link  29  ( FIG. 3 ) formed by a telemetry system onboard railway-vehicle  30 , such as in a train. As will be appreciated by those skilled in the art, such telemetry system may include a head-of-train (HOT) electronic device  32  and an end-of-train (EOT) electronic device  34  ( FIG. 3 ) and may be part of train equipment that may be customarily used for monitoring, for example, brake pipe pressure information and initiate emergency operation of a braking system in the train. HOT and EOT electronic devices  32  and  34  operate at two different frequencies allowing for full duplex communication. These frequencies are allocated to the railroad industry and are substantially immune to from external interference. 
     In one non-limiting embodiment, as train  30  approaches crossing  11 , as schematically illustrated in  FIG. 2 , a signal  36  from HOT electronic device  32  may be detected and processed by railway road crossing control unit  18  to determine entry of the train in the detection area of the railroad track. Without limitation, when the level of signal  36  is at or exceeds a certain threshold limit value, then this would allow making a determination of entry of the train in the detection area of the railroad track, and railway road crossing control unit  18  would activate crossing warning device/s  24 . 
     As train  30  passes continues to pass over crossing  11 , as schematically illustrated in  FIG. 3 , signal  36  from HOT electronic device  32  and signal  38  from EOT electronic device  34  may be detected and processed by railway road crossing control unit  18  to determine a continued presence of the train in the detection area of the railroad track. By way of example and without limitation, when the respective levels of signals  36 ,  38  are within a certain range of values, then this would allow making a determination of continued presence of the train in the detection area of the railroad track, and railway road crossing control unit  18  would continue to maintain activation of crossing warning device/s  24 . 
     As train  30  continues to eventually depart from the crossing, as schematically illustrated in  FIG. 4 , signal  38  from EOT electronic device  34  may be detected and processed by railway road crossing control unit  18  to determine departure of the train from the detection area of the railroad track. By way of example and without limitation, when the respective level of signal  38  is below a certain threshold limit value, then this would allow making a determination of departure of the train from the detection area of the railroad track, and railway road crossing control unit  18  would deactivate crossing warning device/s  24 . It will be appreciated that this embodiment would allow the train to pass through the crossing at a permissible speed, even if the PTC system is bypassed for train control purposes. 
       FIGS. 5-7  respectively illustrate an example flow sequence of events in connection with another non-limiting embodiment of a disclosed railway-vehicle sensing system  28  ( FIG. 1 ), as may involving wireless sensors  50  appropriately arranged to monitor the detection area of the railroad track. Non-limiting examples of wireless sensors  50  may include magnetometer sensors (labeled M in the figures), radar sensors, lidar sensors, ultrasonic sensors (collectively labeled R/L/U in the figures), and a combination of two or more different types of such wireless sensors. 
     In one non-limiting embodiment, as train  30  approaches crossing  11 , as schematically illustrated in  FIG. 5 , upon at least some of the respective wireless sensors  50  (e.g., wireless sensors proximate an entrance side of the detection area) sensing entry of the railway-vehicle in the detection area of the railroad track, railway road crossing control unit  18  would activate crossing warning device/s  24 . 
     As train  30  continues to pass over crossing  11 , as schematically illustrated in  FIG. 6 , respective wireless sensors  50  would continue to sense presence of the train in the detection area of the railroad track, and railway road crossing control unit  18  would continue to maintain active crossing warning device/s  24 . 
     As train  30  continues to eventually depart from the crossing, as schematically illustrated in  FIG. 7 , at least some of the respective wireless sensors (e.g., wireless sensors proximate an exit side of the detection area) would sense departure of the train from the detection area of the railroad track, and railway road crossing control unit  18  would deactivate crossing warning device/s  24 . It will be appreciated that this embodiment would also allow trains to pass through the crossing at a permissible speed, even if the PTC system is bypassed for train control purposes. Additionally, this embodiment provides control of crossing warning device/s  24  for railway vehicles that may not be equipped with the telemetry system discussed above in the context of  FIGS. 2-4 . Moreover, this embodiment is not contingent on functionality of equipment onboard the passing train. 
       FIGS. 8-10  respectively illustrate an example flow sequence of events in connection with still another non-limiting embodiment of a disclosed railway-vehicle sensing system  28  ( FIG. 1 ) involving wheel-sensing and/or axle-sensing devices  60 , (labeled W in the drawings) such as may be disposed at opposite sides of the detection area of the railroad track. As would be appreciated by one skilled in the art, wheel-sensing and/or axle-sensing devices  60  would be mechanically mounted onto the rails but would not be electrically coupled to the rails, (no electrical connection), and therefore eliminating the effects of weather and ballast leakage variances that occur in prior art sensing systems that involve electrical connections with the rails. 
     In one non-limiting embodiment, as railway vehicle  30  approaches crossing  11 , as schematically illustrated in  FIG. 8 , when a first axle of the railway vehicle passes over a sensing device  60  disposed at an entrance of the detection area of the railroad track, railway road crossing control unit  18  would activate crossing warning device/s  24 . By way of example and without limitation, a counter arrangement  62  (labeled C/A in the drawings) in railway road crossing control unit  18  would indicate a positive count at this point. For instance, counter arrangement  62  may include a counter to additively register counts from a sensing device  60  disposed at an entrance side of the detection area of the railroad track. Counter arrangement  62  may be programmed to substractively register counts from a sensing device  60  disposed at an exit side of the detection area of the railroad track. 
     As train  30  continues to pass over the crossing, as schematically illustrated in  FIG. 9 , respective axles of the railway vehicle would continue to be respectively counted in and out as the respective axles of the railway vehicle pass over the respective wheel-sensing and/or axle-sensing devices  60 . As long as the axle count is positive in counter arrangement  62 , this would indicate presence of the railway vehicle in the detection area of the railroad track railway and road crossing control unit  18  would continue to maintain activated crossing warning device/s  24 . 
     As train  30  departs from the crossing, as schematically illustrated in  FIG. 10 , without limitation, when a last axle of the train passes over a sensing device  60  disposed at the exit side of the detection area of the railroad track, at this point, counter arrangement  62  would indicate a zero count and railway road crossing control unit  18  would deactivate crossing warning device/s  24 . This embodiment, like the embodiment discussed in the context of  FIGS. 5-7 , provides control of crossing warning device/s  24  for railway vehicles that may not be equipped with the telemetry system discussed above in the context of  FIGS. 2-4 . 
     In operation, disclosed embodiments offer an innovative technical solution in railway road crossing warning system that involves no wired connections to the track rails. Disclosed embodiments maintain operational robustness in the presence of changing weather and avoid variable electrical ballast conditions that otherwise could develop across the rails, while providing a cost-effective and reliable backup capability for a PTC-started crossing system. 
     While embodiments of the present disclosure have been disclosed in exemplary forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the scope of the invention and its equivalents, as set forth in the following claims.