Patent Application
20100213321
The invention relates generally to railroad end of train telemetry, and more particularly to the reporting of end of train forces.
Within the railroad industry, end of train (EOT) units (sometimes also referred to as end of train devices) are typically attached at the rear of the last car on a train, often to the unused coupling on the end of the last car opposite the head of the train. These EOT devices were originally designed to perform some of the functions previously performed by train personnel located in the caboose, thereby allowing trains to operate without a caboose and with a reduced number of human operators.
Modern EOT units can perform a number of functions, some required by FRA (Federal Railroad Administration) regulations and some not. EOT units monitor air pressure in the air brake pipe and transmit this information to a head of the train (HOT) device located near the front of the train. EOT units also often include an end-of-train marker light to alert trailing trains on the same track of the presence of the end of the train. Two-way EOT units (now required by FRA regulation in the U.S.) can accept a command from the HOT to open a valve to release pressure in the air brake pipe so that the train's air brakes activate to stop the train in an emergency situation. Some EOT units include GPS receivers that are used to transmit location information pertaining to the end of the train to HOT equipment as discussed in U.S. Pat. No. 6,081,769. EOT units typically communicate with the HOT using radio-based communications. This is because there is no hard-wired electrical connection between the head of the train and the end of the train on some trains, especially freight trains.
Some EOT units include motion detectors that are used to inform the HOT as to whether, and in some cases in which direction, a train is moving. In some EOT units, an accelerometer is used as the motion detector. Motion detection is reported by only a single bit (i.e., the single bit indicates only motion or lack thereof without any indication of speed or direction) under AAR Standard S-5701 for “End-of-Train Communications.” The indication of train movement or lack thereof from the motion detector, together with an indication of the head of train movement, may be used by train personnel and/or computerized on-board train control systems to determine whether or not a train separation has occurred. However, such a determination is not very reliable given the single bit used to report motion pursuant to AAR Standard S-5701 because movement in opposite directions, and movement at significantly different speeds in the same direction, cannot be determined.
A somewhat more capable device is described in U.S. Pat. No. 6,087,950, which describes a motion detector that can be attached to an end of train unit. The motion detector includes a single axis accelerometer. The motion detector is configured to report a motion state that can be moving or non-moving and a motion direction that can be forward or reverse.
More recently, EOT units that can communicate their positions to devices located off of the train, such as those described in U.S. Pat. No. 7,096,096 and in U.S. Pat. Pub. No. 2007/0170314 (the entire contents of both hereby being incorporated by reference herein), have become known in the art. These communications allow personnel responsible for such EOT units to locate them. Such communications can occur both when the EOT units are mounted on a train and when they are not mounted on any train.
A more complete appreciation of the invention and many of the attendant features and advantages thereof will be readily obtained as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
a and 2b are perspective and front views, respectively, of an EOT unit according to one embodiment of the invention.
The present invention will be discussed with reference to preferred embodiments of end of train units. Specific details, such as message formats and various reporting methods, are set forth in order to provide a thorough understanding of the present invention. The preferred embodiments discussed herein should not be understood to limit the invention. Furthermore, for ease of understanding, certain method steps are delineated as separate steps; however, these steps should not be construed as necessarily distinct nor order dependent in their performance.
Excessive forces exerted on trains can damage both equipment (train and track) and cargo being carried on the train. Excessive forces applied to a train tends to become magnified at the end of the train. Such excessive forces can result from various causes. An operator can cause excessive forces at the end of the train by accelerating too rapidly, which will cause a car at the end of the train to jerk in the direction of track once the slack between cars is taken up as the locomotive(s) at the head of the train accelerate. An inexperienced operator, or even an experienced operator who is operating a very long train, may not realize the forces being exerted on an end of the train due to his/her actions. Another potential cause of excessive forces at the end of the train can result from excessively “wavy” tracks that cause cars to sway rapidly from side to side as the cars travel along the tracks. These forces occur mainly along an axis perpendicular to the track. Still another potential cause of excessive forces at an end of a train are poor track joints, which may occur at grade crossings, bridges, or the like but which may also occur anywhere along a track. These forces tend to occur primarily along an axis that is vertically oriented with respect to the track. Excessive forces at the end of the train can also be caused in other ways.
Because of the different possible causes for excessive forces at the end of the train, different actions are performed in different embodiments discussed herein. The first step is to detect the occurrence of an excessive force. This step may be performed using an accelerometer located in an end of train unit (it being understood that an accelerometer measures acceleration, which is proportional to force). In preferred embodiments, the accelerometer is a tri-axial accelerometer with the axes oriented such that a first axis is along a direction of the track, a second axis is along a direction perpendicular to the track and a third axis is along a direction vertical to the track. This arrangement is advantageous in that it provides the ability to determine a direction along with an acceleration has occurred, which may be indicative of the cause of the acceleration (e.g., a sudden vertical acceleration may result from a problem with the track whereas a sudden acceleration in a direction of a track may result from an operator accelerating a train from a stopped position too rapidly). In other embodiments, a single or dual axis accelerometer is used. Such embodiments may employ one or more accelerometers along one of the three axes discussed above, or may orient the accelerometer such that it is sensitive to accelerations in more than one axis as discussed in U.S. Pat. No. 6,087,950. Embodiments utilizing a single accelerometer can be less expensive than embodiments employing multiple accelerometers or multiple axis accelerometers.
The accelerometer(s) may be periodically polled in real time to detect forces greater than a threshold. Alternatively, a triggering circuit such as a one-shot may be used to generate an interrupt when the accelerometer measures a force greater than the threshold. The accelerations reported by the accelerometers are typically “instantaneous” accelerations, and these instantaneous accelerations are used directly in some embodiments. In other embodiments, a plurality of instantaneous accelerations are filtered (e.g., moving window average filtering, Kalman filtering, etc.).
Various embodiments employ different thresholds. In some embodiments, the threshold may be fixed. In such embodiments, the threshold may be set to an acceleration based on a safety factor and maximum force for which a typical car coupling can withstand divided by a maximum car weight. A typical freight car coupling in use in the U.S. can withstand a force of about 350,000 pounds, and a current maximum expected car weight in the U.S. freight railroad industry is 268,000 pounds (this represents the weight of the car plus a maximum cargo). In some embodiments, the acceleration threshold based on these values and a safety factor is chosen as 1 g. The threshold is preferably 0.25 g or greater to ensure that accelerations associated with normal movement of the train are not reported as excessive. In yet other embodiments, the threshold is set dynamically. The threshold may be set dynamically based on a particular cargo being carried on the train, particular equipment (e.g., couplings, types of cars) used on the train, or any other factor which may affect a desirable maximum EOT force.
Once an excessive force has been detected, the detection must be communicated. The communication may occur immediately or soon after the detection has been made, and/or the detection may be recorded and communicated later. In some embodiments, the occurrence of the excessive force is communicated to a head of train device for display to an operator immediately or soon after the detection occurs (such display being different from the manner in which an indication of movement of the train is normally displayed to the operator). The message and/or display may include a simple indication that an acceleration greater than the threshold has been observed, or may include the actual (preferably instantaneous) acceleration (or accelerations in multiple axis accelerometer embodiments) measured by the accelerometer. In such embodiments, the head of train device relays the message to a central office, either in addition to or instead of displaying the message. In other embodiments, the EOT device may transmit the message directly to a central data collection site. For example, EOTs equipped for long range communication with a central site (e.g., via a cellular modem that communicates with a cellular base station) are disclosed in U.S. Pat. Pub. No. 2007/0170314. As disclosed in that publication, the EOT may periodically transmit a message including the EOT location.
In some embodiments, the message further includes information (e.g., an amount of excessive force or an indication that an excessive force has been detected together with a location and/or time at which the excessive force was detected). In yet other embodiments, the EOT device includes an event recorder which records information pertaining to the excessive force. The data from the EOT device is accessed later and appropriate action (e.g., informing the operator of the excessive force if the operator was the cause, repairing the section of track causing the excessive force) is taken. In still other embodiments, an excessive force detection message sent from the EOT to the HOT is recorded in an event recorder included in the HOT device and/or forwarded from the HOT device to the train's main event recorder. Still other methods for communicating the detection of an excessive force are possible.
An exemplary embodiment of an EOT force reporting system will now be discussed. This embodiment will include multiple EOT force reporting methods as discussed above. It should be understood that other embodiments employ less than all of, or alternatives to, the reporting methods discussed in connection with this embodiment.
a and 2b illustrate an embodiment of the EOT unit 100. The EOT unit 100 includes a housing 110 in which the internal components of the EOT unit 100 (discussed in further detail below) are located. A handle 111 is attached to the housing 110 to facilitate the installation and removal of the EOT unit 100 from a train car. Also attached to the housing is a connector 120 for connecting the EOT unit 100 to an air brake hose 10 which is in fluid communication with the train's air brake pipe (not shown in
A block diagram 30 of the EOT unit 100 of
The processor 210 is connected to control an EOT marker light 140 (although a direct connection is illustrated in
Also connected to the processor 210 is an air pressure transducer 240, which is in fluid communication with the air brake pipe 10 and is configured to detect the pressure in the air brake pipe 10. The processor 210 reads the pressure in the air brake pipe 10 reported by the transducer 240 and periodically transmits this and other information to the HOT using the HOT transceiver 250. Under AAR Standard S-5701, the report occurs once every 55-65 seconds in the absence of significant pressure changes. The format of an exemplary report is set forth below:
In embodiments in which excessive EOT forces are reported to the HOT device 300, the occurrence and/or measurement(s) (e.g., magnitudes) of excessive accelerations can be included in the “optional block data bits” portion of the message described above or may be sent in a separate message.
An emergency solenoid 280 is also connected to the processor 210 and the air brake pipe 10. When the processor 210 receives an emergency braking command from the HOT via the HOT transceiver 250, the processor 210 controls the solenoid 280 to open, causing a loss of pressure in the air brake pipe 10 and activation of the train's brakes. In some embodiments, another solenoid (not shown in
An accelerometer 290 is also connected to the processor 210. As discussed above, the accelerometer may be a single axis, dual axis or three axis accelerometer in various embodiments. Those of skill in the art will recognize that the signals from some accelerometers may be in analog form and that an analog-to-digital (A/D) converter (not shown in
Also connected to the processor 210 is an event recorder 295. The event recorder 295 records data pertinent to the EOT unit 100, such as the content and time of transmission of various messages sent and received by the EOT unit 100. As discussed above, the occurrence of excessive acceleration events are also recorded for later retrieval in some embodiments. The data recorded for such events can include the date, time, and location of the train at the time of the event as reported by the positioning system 270 plus other circumstances surrounding the event.
The processor 210 is further connected to a positioning system 270, which is a GPS receiver in preferred embodiments but may also be an INS (intertial navigation system), LORAN device, or any other positioning system. The positioning system 270 supplies the processor 210 with reports on the position of the EOT unit 100.
The processor 210 is also connected to a cellular modem 260. The processor 210 uses the cellular modem to send reports including an identifier of the EOT unit 100 and location (and preferably time) information obtained from the positioning system 270 to an EOT tracking station at periodic intervals. The processor 210 also receives “page” messages (messages requesting the EOT unit to report its current location) and “disable” messages (messages instructing the EOT unit to enter an non-operational state) via the cellular modem 260. In addition to reporting EOT location to the EOT tracking facility 302, the cellular modem 260 may also report excessive accelerations detected by the accelerometer 290. This reporting is in addition to (or, in some embodiments, in lieu of, the reporting accomplished via recording at the EOT event recorder 295, the display at the HOT device 300, and/or the recording at the event recorder 301).
During normal operation, the processor 210 controls the EOT marker light 140, communicates air brake pipe pressure information to the HOT, activates the emergency solenoid 280 in response to commands from the HOT, communicates train position to the EOT tracking facility 302 and performs other functions that will not be discussed further herein to avoid obscuring this disclosure.
In addition to the operations discussed above, the processor 210 monitors the accelerometer 290 in order to detect excessive accelerations. A flowchart 400 of the operations performed by the processor 210 is shown in
If the filtered acceleration is below the threshold, no reporting is necessary and the processor 210 delays a period of time (100 ms in some embodiments) at step 408 before repeating step 402. If the filtered acceleration exceeds the threshold at step 406, the processor 210 records the filtered acceleration in the EOT event recorder 295 at step 410. Next, the processor 210 reports the filtered acceleration to the EOT Tracking Facility 302 via the cellular modem 260 at step 412. The processor 210 then reports the filtered acceleration to the HOT device 300 at step 414. The processor then delays for a brief period at step 408 before repeating steps 402 and following.
The HOT device 300 of
A block diagram of the HOT device 300 is shown in
If the message from the EOT does indicate that an excessive EOT force has been detected by the EOT unit 100 at step 404, a message is displayed at the HOT display 351 at step 408. In those embodiments in which the excessive force message from the EOT only indicates that an excessive EOT force has been detected, the message in the display 351 may simply indicate “EXCS EOT ACC DET.” In those embodiments in which the detected EOT force is reported in the message from the EOT, the HOT may display a message such as “EOT ACC XXG DET,” where XX represents the EOT acceleration (filtered or unfiltered) reported by the EOT unit 100. In those embodiments utilizing a triaxial accelerometer, the message shown to the operator in display 351 may also include an X, Y, or Z to indicate the axis on which the excessive EOT acceleration occurred. In some embodiments, the processor 320 may take corrective action, such as requiring the operator to acknowledge the excessive acceleration (e.g., by pushing one of the indicator buttons 330 or keys 340) or forcing an emergency braking operation in the event that no acknowledgement from the operator is received. Such corrective action may occur only when the EOT acceleration exceeds a second, higher threshold and/or only after a certain number of excessive accelerations have been detected in some period of time in some embodiments. In yet other embodiments, the processor 320 requires an operator acknowledgement if a first threshold is exceeded and initiates an emergency braking operation if the second threshold is exceeded.
It should be noted that, in some embodiments, the accelerometer may be used to both a) determine whether the train is in motion, and b) detect excessive EOT acceleration. In such embodiments, a first threshold is used for the former and a second, higher threshold is used for the latter. Such embodiment may also employ a still higher third threshold that can be used to include an indication in a message to a head of train device that the train's brakes should be activated (alternatively, the third threshold can be implemented in the HOT device).
Next, the processor 320 records the occurrence of the excessive EOT force at the event recorder 301 at step 410 and transmits a message to a central office (e.g., a dispatcher) at step 412. The next EOT message is then processed at step 402. Alternatively, in embodiments in which the excessive force indication is in a message with the format of Table 1, the rest of the message is processed at step 406.
Those of skill in the art will recognize that various modifications to the EOT unit 100 are possible. For example, it is possible to operate the EOT unit 100 solely with battery power rather than using batteries in conjunction with an air powered generator. Cellular modem 260 may be replaced with any type of wireless communication system. Various other modifications to the components of the EOT unit 100 are also possible.
Furthermore, the purpose of the Abstract is to enable the U.S. Patent and Trademark Office and the public generally, and especially the scientists, engineers and practitioners in the art who are not familiar with patent or legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of the technical disclosure of the application. The Abstract is not intended to be limiting as to the scope of the present invention in any way.
While the invention has been described with respect to certain specific embodiments, it will be appreciated that many modifications and changes may be made by those skilled in the art without departing from the spirit of the invention. It is intended therefore, by the appended claims to cover all such modifications and changes as fall within the true spirit and scope of the invention.
