This disclosure is directed toward control systems and methods for a railway grade, or level, crossings.
A grade crossing, also referred to as a level crossing, is a location where a railroad tracks cross a road, sidewalk or other surface used by moving objects (cars, trucks, pedestrians, etc.) at the same grade, or level (i.e., no bridge or tunnel is involved). At such locations, a crossing warning device warns of the approach of a train at a crossing so that moving objects on the road or other surface can avoid being struck as a train on the tracks traverses the crossing. Crossing warning devices may include crossing gate arms (e.g., the familiar red and white striped wooden arms often found at highway grade crossings to warn motorists of an approaching train), crossing lights (such as the two red flashing lights often found at highway grade crossings alone or in conjunction with the crossing gate arms discussed above), and/or crossing bells or other audio alarm devices. These crossing warning devices are controlled by a grade crossing control system.
Some types of grade crossing control systems utilize a type of circuit known in the art as a constant warning time (CWT) circuit to control crossing warning devices. Other types of grade crossing control systems, particularly those used with electrified track in which one or both of the rails along which the train travels is used to carry return current which interferes with the operation of CWT circuits, utilize a track occupancy circuit to control the crossing warning devices at a grade crossing. As discussed in U.S. Pat. No. 8,590,844, the entire contents of which are hereby incorporated by reference, track occupancy circuits are used in the railroad industry to detect the presence of a train in a block of track. The block of track monitored by a track occupancy circuit is typically referred to as an “approach” in the context of a grade crossing, and there is typically an approach on either side of the crossing.
There are several types of track occupancy circuits known in the art. One type, sometimes referred to as an AC overlay track occupancy circuit, includes a transmitter and a receiver, with the transmitter configured to transmit an AC signal, typically in the range of audio frequency, through the track rails at one end of a block of track and the receiver connected to the rails at the other end of the block and configured to detect the signal. Other than the connection through the track rails, there is typically no connection between the transmitter and receiver for a block in such AC overlay track occupancy circuits. When a train is present in a block of track monitored by a track circuit, the train shunts, or shorts, the two rails, with the result that no signal is received at the receiver, and the loss of a signal from the transmitter at the receiver is taken as an indication that a train has entered the block of track. DC track circuits are also known in the art, although they are typically not used in electrified track grade crossing applications. Still other types of track occupancy circuits are known in the art.
In a grade crossing control system using a track circuit, the track circuit may be configured to an approach with a length chosen based in part on a maximum expected speed (e.g., a maximum allowed speed) of a train along that section of track. When an AC overlay track occupancy circuit is used, the receiver may be placed at or near the crossing (e.g., just outside of an edge of the island closest to the block), and the transmitter may be placed at the far end of the block. The grade crossing control system may be configured to activate the grade crossing warning device as soon as the track circuit detects the presence of a train and deactivate the grade crossing warning device after the train has passed the crossing. In such systems, a train moving more slowly than the maximum expected speed will result in an unnecessarily long period during which the grade crossing warning device is activated.
A conventional grade crossing 100 with a grade crossing control system 110 is shown in
When no train is present on the track 100, both of the AC track circuits 120, 130 (each formed by a pair of receivers and transmitters) are energized, indicating that no train is present. When a train 170 traveling along the track 101 reaches AC overlay the transmitter 121 at the start of the West Approach, the train's axles and wheels effectively short the circuit such that no signal or a significantly attenuated signal is received at the receiver 122 (this is referred to in the art as the track circuit 120 or the receiver 122 de-energizing, or dropping). When this occurs, the controller 110 activates the grade crossing warning device 160 (although the grade crossing warning device 160 is illustrated as a single box in
From the foregoing discussion, one of skill in the art will recognize that the amount of time that the grade crossing warning device 160 will remain activated will depend on the speed of the train 170. One of skill in the art will further recognize that if the train is traveling well below the maximum expected speed, the grade crossing warning device 160 will remain activated for an amount of time that is significantly longer than necessary because the length of Approach 1 is chosen based on an expected maximum speed of the train rather.
The controller 210 may use the configurable delay period to delay activation of the crossing warning system 260 (referred to as “wrapping” or “bypassing” the track occupancy circuit) after train enters Approach 1 and the track occupancy circuit 220 drops. The delay period may be longer when time between the start and end inputs is long (indicating that the train speed is slow) and may be shorter or nonexistent when the time between the start and end inputs is short (indicating the train's speed is fast or at a maximum). In some embodiments, the delay period may take on a continuous range of values, and in other embodiments the delay period may take on one of a number of fixed values. The length of the section of track should be long enough to ensure that the time between the start and end inputs to the controller 210 accurately reflects the speed of the train and allows for adequate resolution among such fixed values. By delaying the activation of the crossing warning system 260 for a period of time that depends on the speed of the train, the amount of time wasted on unnecessarily long crossing warning system 260 activation periods may be reduced.
As discussed above, the device 280 that provides the start and end inputs to the controller 210 may be realized in many different ways. In one embodiment, a pair of detectors such as laser detectors, RFID tag readers, transponders, etc., may be placed at respective ends of the section of track 281. The detectors may communicate directly or indirectly (with one detector communicating through the other device, and/or one or both devices communicating through one or more additional devices) with the controller 210, and the communication may take place wholly or partly through one or more rails of the track, through one or more separate conductors such as a buried or above-round wire, optically, wirelessly or by any other means.
An embodiment of the device 280 is shown in
A fourth embodiment is shown in
Another option, which may be utilized if different frequencies are not available for the two AC overlay track occupancy circuits 280, 220 of
In operation, prior to the presence of any train in Approach 2, the receiver 282 of the second track occupancy circuit 280 may communicate the absence of a train in Approach 2 to the transmitter 221 of the first track occupancy circuit 220. In response, the transmitter 221 may transmit code A to the receiver 221 of the first track occupancy circuit 221, and the code A information is communicated to the controller 210 which interprets the code A information as indicating that no train is present in either Approach 1 or Approach 2. Once an eastbound train enters Approach 2, the signal transmitted by the transmitter 281 of the second track occupancy circuit in Approach 2 is no longer received by the receiver 282 of the second track occupancy circuit, which causes the receiver 282 to communicate the presence of a train in Approach 2 to the transmitter 221 of the first track occupancy circuit 220. In response to the indication of a detected train in Approach 2 from the receiver 282, the transmitter 221 of the first track occupancy circuit begins transmitted code C rather than code A. The receiver 222 of the first track occupancy circuit communicates the change from code A to code C to the controller 210. Controller 210 interprets the change from code A to code C as an indication that a train has entered Approach 2 but (because a code from the transmitter 221 is still being received by the receiver 222) has not yet entered Approach 1, and uses this as the start time input that is used together with an end time input as an indication of train speed as explained further below.
The transmission and receipt of code A will continue until such time as the train reaches Approach 1, at which point the receiver 222 of the first track occupancy circuit will no longer receive any signal from the transmitter 221 and will communicate this loss of signal to the controller 210. The controller 210 interprets the loss of signal as an indication that the train in Approach 2 has reached Approach 1, and will use this as the end time input. The controller 210 uses the difference between start and end times as an indication of train speed as discussed in further detail below.
In the embodiments discussed above in
However, the length of Approach 2 is constant, and therefore the calculation of the train speed is not necessary, and the controller may simply calculate the difference in time between the start and end inputs and use that difference as an indication of train speed. The delay period may include a safety factor, and may be subject to a maximum and/or a minimum delay which may be chosen depending on specifics of conditions at the actual crossing. The delay period may vary continuously between a minimum and maximum delay period depending on a mathematical formula, or may be one of a number of discrete values determined using a look-up table with the difference between the start and end inputs (which may be rounded or rounded up to the nearest integer value) serving as an index into the table, or may be determined by comparing the difference between the start and end inputs to thresholds associated with discrete delay periods.
Table 1 below illustrates exemplary parameters for one possible application employing thresholds as described above, and used with an installation such as that shown in
In Table 1, “Time Delta” is the calculated time necessary to traverse Approach 2 at the given train speed; “Approach Time” is the calculated time for the train to traverse Approach 1 at the given train speed; “Programmed Time Delta” is the Time Delta rounded up to the nearest whole second; “Wrap Time” is the period of time (the delay period) necessary to delay activation of the warning system after the train enters the inner approach in order to achieve the Warning Time, and “Warning Time” is the desired minimum amount of time between the time at which the grade crossing warning system 260 is activated and the time at which the train will reach the end of Approach 1.
In this embodiment, the Time Delta is rounded up to the nearest integer number of seconds to result in the Programmed Tile Delta as a safety factor, and the Programmed Time Deltas serve as the thresholds to which the time difference between the start and end inputs may be compared. In this example, the lengths of the inner approaches may be chosen to result in the desired minimum delay for a train traveling a maximum speed; as a consequence, no wrap time may be needed for a train traveling at the maximum speed. The remaining three train speeds in Table 1 (i.e., 80, 60 and 40 mph, respectively) each have an associated Programmed Time Delta. These Programmed Time Deltas may be used as thresholds to which is compared the time difference between the start and end inputs associated with an inbound train in the outer approach. Thus, if the time difference between the start and end inputs is at least 5 seconds (the Programmed Time Delta associated with 80 mph) but not more than 6 seconds (the Programmed Time Delta associated with 60 mph), the 10 second Wrap Time associated with the 80 mph train may be selected. Similarly, if the time difference between the start and end inputs is at least 6 seconds (the Programmed Time Delta associated with 60 mph) but not more than 9 seconds (the Programmed Time Delta associated with 40 mph), the 27 second Wrap Time associated with the 80 mph train may be selected. Finally, if the time difference between the start and end inputs is at least 9 seconds or more, the 59 second Wrap Time associated with the 40 mph train may be selected.
In each case in Table 1, the warning time is at least approximately 41 seconds (it will actually be longer due to the safety factor associated with rounding the Time Delta up to the Programmed Time Delta and for trains that are traveling at speeds between those of nominal speeds associated with each threshold. The latter is true because the Wrap Time is the same for trains traveling at a nominal speed of 80 mph and for trains traveling at nominal speeds below 80 mph and above 60 mph, which means that the Warning Time for the trains traveling at nominal speeds below 80 mph and above 60 mph will be longer than the warning time for the 80 mph train).
The minimum, maximum and granularity of the values and in Table 1 may be a function of the range of expected train speeds, the physical configuration of the crossing, the types of circuits and devices used to provide the start and end inputs in the outer approach, the type of track occupancy circuit used in the inner approach, and safety considerations. For example, if the components and types of circuits chosen are such that the start input energizes more quickly than the end input de-energizes or otherwise provides the end input, it may be necessary to use more coarse granularity or shorten the wrap times to account for this difference. Finer or more coarse granularities (i.e., smaller or larger numbers of thresholds, which are not necessarily fixed at integer number of seconds) may be used in other embodiments. In some embodiments, the controller may include a user interface screen, or may communicate with an external user interface screen that provides the user with the ability to select the following options for each track circuit in an inner approach: 1) a source of the start input; 2) a source of the end input (which may be the de-energization of the inner approach track itself); 3) a number of discrete delay periods used by the track circuit (i.e., the granularity of the delay period); 4) for each discrete delay period, a threshold time period corresponding to the difference between the start and end inputs (a Programmed Time Delta; and 5) for each discrete delay period, a length of the delay period (a Wrap Time).
In another embodiment, the time difference between the start and end inputs is used as an input to a mathematical formula to calculate the delay period/wrap time necessary to achieve the desired warning time. If the speed in the outer approach and the speed in the inner approach are assumed to be constant (which was assumed in Table 1 above), the delay period/wrap time for a desired warning time may be calculated according to the following formula:
DP=(Δt*(outer approach length/inner approach length))−WT
where DP is the wrap time or delay period in seconds, Δt is the difference between the start and end inputs in seconds, and WT is the desired warning time in seconds. For a crossing configured as discussed above in Table 1 and a 41 second desired warning time, this equation becomes:
DP=(Δt*12)−41
The result of this calculation may be rounded down to the nearest integer number of seconds to result in a shorter delay period, and thus a longer warning time, for the sake of safety.
If no end input was pending at step 704 when the start input is received (thus indicating an inbound train), the controller may start a timer at step 708. The timer may be set to a maximum allowed time for receipt of the end input. The controller 210 may then check for receipt of an end input at step 710. The end input may be received from a component such as a laser detector positioned at the end of the outer approach, from a receiver forming part of track occupancy circuit configured to monitor the inner approach (in which case de-energization of the inner approach track circuit may be the end input), or by any of the other mechanisms discussed earlier. If the end input is not received at step 708, the controller 210 may determine whether the timer has expired at step 712. If the timer has expired at step 712, which signifies that the maximum time for receipt of the end input has been exceeded, the controller 210 may set the delay period to zero at step 714 and then may continue with step 720 as will be explained below.
If the end input is received at step 710, the controller 210 determines the Delta Time (the difference between the start and end inputs) at step 716. The controller 210 may perform this step in a number of ways. For example, the controller 210 may start a timer when the start input is received and simply read the elapsed time to determine the Time Delta. Alternatively, the controller 201 may record the time at which the start input is received at step 702 and subtract that time from the time at which the end input is received at step 710. Still other ways in which the controller 210 may determine the Time Delta will be apparent to those of skill in the art. As discussed above, the controller 210 may round (or round up) the Time Delta to an integer number of seconds as part of this step 716. The controller 210 may then determine the delay period (the Wrap Time) at step 718. As discussed above, the controller 210 may perform this step by calculating a mathematical function using the Time Delta as a parameter to determine the delay period, or may use the Time Delta as in index into a lookup table to retrieve a delay period, or may compare the calculated Time Delta to a plurality of thresholds to determine a minimum threshold exceeded by the Time Delta and then set the delay period to the a delay period associated with the minimum threshold in the manner described above. Those of skill in the art will recognize that still other schemes for determining the delay period based on the Time Delay may be performed by the controller 210.
Once the delay period has been determined at step 718 or set to zero at step 714, the controller may wait until the track circuit for the inner approach de-energizes at step 720 and then may apply the delay period at step 722 before activating the warning system 260 at step 724. The start and stop inputs may then be cleared at step 706 and the process may be repeated starting at step 702. It should be noted that other steps not illustrated in
The controller circuit disclosed herein can be implemented in digital electronic circuitry, or in computer software, firmware, hardware, or in combinations of one or more of them. The logical operations described herein can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer readable medium for execution by, or to control the operation of, data processing apparatus. The computer readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter effecting a machine-readable propagated signal, or a combination of one or more them. The term “data processing apparatus” encompasses all apparatus, devices, and machines for processing data, including by way of example a programmable processor (including, but not limited to microprocessors and microcontrollers), a computer, multiple processors or computers, or special purpose logic circuitry. The data processing apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. A propagated signal is an artificially generated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal, which is generated to encode information for transmission to suitable receiver apparatus.
A computer program (also known as a program, software, software application, script, or code) can be written in any programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.
The processes and logic operations described in this document can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors and microcontrollers, digital signal processors, and any one or more processors of any kind of digital computer. The processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit). Computer readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto optical disks; and CD ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.
While various embodiments have been described above, it should be understood that they have been presented by way of example and not limitation. It will be apparent to persons skilled in the relevant art(s) that various changes in form and detail can be made therein without departing from the spirit and scope. In fact, after reading the above description, it will be apparent to one skilled in the relevant art(s) how to implement alternative embodiments.
In addition, it should be understood that any figures which highlight the functionality and advantages are presented for example purposes only. The disclosed methodology and system are each sufficiently flexible and configurable such that they may be utilized in ways other than that shown.
Although the term “at least one” may often be used in the specification, claims and drawings, the terms “a”, “an”, “the”, “said”, etc. also signify “at least one” or “the at least one” in the specification, claims and drawings.
Finally, it is the applicant's intent that only claims that include the express language “means for” or “step for” be interpreted under 35 U.S.C. 112(f). Claims that do not expressly include the phrase “means for” or “step for” are not to be interpreted under 35 U.S.C. 112(f).
Filing Document | Filing Date | Country | Kind |
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PCT/US2018/021063 | 3/6/2018 | WO | 00 |