METHOD AND APPARATUS FOR DETERMINING OVERALL LENGTH OF A TRAIN

Method and Apparatus for Determining Overall Length of a Train

BACKGROUND OF THE INVENTION The present invention generally relates to train monitoring and control systems such as end-of-train (EOT) systems or the like and more particularly to a method and apparatus for determining the overall length of a train

Knowledge of a train's overall length is often required to ensure safe operation a*.d handling of the tram For example, the length of a train I utilized to assess whether the train has cleared a point on the track sucn as, for example, a siding or a switch To ensure that the point has been cleared, the crew of the train may move the train past the point a distance equal to the train's length plus a predetermined safety factor Normally, this method assures that the train has safely cleared the point However, if the determined train length is significantly in error, one or more cars of the train may extend past the point possibly resulting a collision with another train

Presently, train length is either measured directly or estimated by moving the train past a fixed point at a known velocity A measurement is started when the front of the train passes the point and ended wnen the end of the train passes that point The length of the train may then be measured by determining the distance of the front of the train from the point or calculated based on the velocity of the train However, this method of determining the train's length is subject to human error ana may prove time consuming when performed each time cars are addeα or removed from the train

Known to the art are end-of-train (EOT) systems whicn provide a variety of functions once perrormed by crew riding in the caboose of a

- 1 train Two types of EOT systems exist one-way EOT systems and a two- way EOT systems Both types of EOT systems provide crew riding in the cab of a locomotive with key end-of-train information such as, for example brake pipe pressure at the rear of the train, end of train motion EOT battery condition, and marker light status

Typically, one-way EOT systems comprises a cab unit mounted in the cab of the lead locomotive of the train and an end-of-train (EOT) unit mounted to the last car of the train The EOT unit includes a transmitter which transmits last car status information monitored by the unit to a receiver in the cab unit The cab unit then displays this information to the crew In two-way EOT systems, the receiver and transmitter of the oneway system are replaced with transceivers which both receive and transmit information between the cab unit and the EOT unit Thus, in addition to providing end-of-train information to the crew, the two-way EOT system allows the crew to command the EOT unit to release brake line pressure at the rear of the train thereby permitting simultaneous application of brakes at the front and rear of the train This feature greatly improves the train's emergency braking capability Consequently, in 1992, Congress amended the Federal Railroad Safety Act to require railroads to install two-way EOT systems by January 1 , 1998 on trains traveling over 30 miles per hour or operating on heavy grades

It is therefore desirable to improve the safety and efficiency of railroad operations by providing apparatus for determining the length of a train utilizing a received signal such as a reference signal from a global positioning system or the like, wherein this determination may be automatically uDdated as cars are added to or removed from the train It

2 - is further desirable that the apparatus be capable of operation in conjunction with existing EOT systems.

-- 3 SUMMARY OF THE INVENTION

Therefore, a principle object of the present invention is to provide a method and apparatus for determining the length of a train.

Another object of the present invention is to provide a method and apparatus capable of updating this determination as cars are added or removed from the train

A further object of the present invention is to provide a method and apparatus for determining the length of a train utilizing received signal such as a reference signal from a global positioning system or the like

Accordingly, the present invention provides a^" novel method and apparatus for determining the length of a train utilizing received signal such as a reference signal from a global positioning system or the like. A first receiver is positioned on a train at a first position, preferably the front of the train. The first receiver receives a signal, such as a reference signal from a global positioning system or the like, from which the first position may be determined. Similarly, a second receiver is positioned on the train at a second position, preferably the end of the train. The second receiver receives a signal from which the second position may be determined A processor, operatively coupled to the first and second receivers, determines the length of the train based on the first and second positions

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory crly and are not restrictive of the invention claimed

The accompanying drawings, which are incorDorated in and constitute a part of the specification, illustrate an embodiment of the

__ 4 ~ invention and together with the general description, serve to explain the principles of the invention.

5 -- BRIEF DESCRIPTION OF THE DRAWINGS

The numerous objects and advantages of the present invention may be better understood by those skilled in the art by reference to the accompanying figures in which:

FIG. 1 depicts a train having a system for determining the length of the train according to an exemplary embodiment of the present invention;

FIG. 2 is a block diagram depicting schematically exemplary apparatus of a system for determining the length of a train as shown in FIG. 1 ; and

FIG. 3 is a block diagram illustrating a two-way EOT system modified according to an exemplary embodiment of the present invention with apparatus for determining the length of a train.

— o DESCRIPTION OF THE PREFERRED EMBODIMENT Reference will now be made in detail to the presently preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings

Referring now to FIG 1 , a train having a system for determining the length of the tram according to an exemplary embodiment of the present invention is shown The tra 100 preferably comprises one or more locomotives coupled to a plurality of cars which may be configured for transporting raw materials, freight, or passengers An end car 102 of the tram 100 may be equipped with a first receiver 104 which receives a signal such as a reference signal from a global positioning system and determines a first position such as, for example, a geo-referenced end-of- tra position for the end of the train 106 Similarly, the front or lead locomotive 108 of the train 100 may be equipped with a second receiver 110 which receives a signal such as a reference signal from the global positioning system and determines a second position such as, for example, geo-referenced front-of-tra position for the front of the train 112 A processor may be operatively coupled to the first and second receivers 104 & 1 10 (see FIG. 2) For example, the first receiver 104 may be coupled to a transmitter which communicates the first position to the processor via the second receiver 110 or a third receiver operatively coupled to the processor (see FIG 2) The processor may then calculate the length of the train 100 based on the first and second positions by applying basic kinematic methods

Preferably both the first receiver 104 and the second receiver 110 are capable of receiving a geo-refereπcing signal from a global positioning

.. 7 „ system in order to accurately geo-reference the positions of front and end of the train. The global positioning system is preferably the Global Positioning System (GPS), a space-based radio-navigation system managed by the U.S. Air Force for the Government of the United States. The Government provides civilian access to the Global Positioning System which is called the Standard Positioning Service (SPS). The Standard Positioning Service is intentionally designed to provide a positioning capability which is iess accurate than the positioning service provided to military operators, however various techniques have been developed to improve the accuracy of the civilian positioning service wherein position accuracy of one to five meters may be achieved.

The present system may be utilized in conjunction with the Global Positioning System (GPS) to accurately geo-reference the positions of the front and end of the train at a given time. The first and second receivers 104 & 110 may each receive a reference signal from a satellite 1 14 operating as part of the GPS satellite constellation. Typically the signals from at least three satellites are required to derive a coordinate position solution. Further reference signals which are not part of the government operated GPS system may also be used in order to compensate for the degraded civilian GPS signal (which may be transmitted as an FM carrier sublink by land based or space based locations or by an RS-232 data bus, for example). Such correcting signals may be provided by a third- party differential correction service provider. Other ways of correcting the degraded civilian signal may also be utilized which do not require an independent correcting signal to be transmitted. For example, signai processing techniques such as cross correlation of the military signai and the civilian signal may be utilized to improve the accuracy of the civilian signal

Referring now to FIG 2, a block diagram depicting schematically exemplary apparatus of a system for determining the length of a tram is shown The system 200 preferably comprises an end-of-train unit 202 mounted to the last or end car of the tram and a front-of-tram unit 204 mounted in the cab of the first or lead locomotive

The end-of-train unit 202 may include a GPS receiver 206 having an integral antenna 208 which receives a reference signal from the Global Positioning System (GPS) A processor 210 may periodically determine a geo-referenced end-of-train position for the end of the tram utilizing the received reference signal from the GPS receiver 206 Preferably, the processor 210 also records the time when reference signal is received and the geo-referenced end-of-train position is determined The processor 210 may be coupled to a transmitter 212 such as, for example, a radio frequency (RF) transmitter or transceiver and an antenna 214 The transmitter 212 preferably transmits the determined end-of-train position and recorded time to the front-of-tram unit 204 where they are received by a receiver 216 such as an RF receiver or transceiver having a second antenna 218

The front-of-tra unit 204 may include a second GPS receiver 220 having an integral antenna 222 for receiving a reference signal from the Global Positioning System (GPS) Preferably when the end-of-train position and recorded time are received by the receiver 216, a processor 224 in the front-of-tram unit 204 causes the second GPS receiver 220 to receive a reference signal from the Global Positioning System (GPS)

9 - The processor 224 may then use the reference signai to determine a geo- referenced front-of-tram position for the front of the tram The processor 210 may also record the time when the reference signal is received and the geo-referenced front-of-tram position is determined The processor 224 may then apply basic kinematic methods to determine the length of the tram based on the determined front-of-tram and end-of-train positions, recorded times when these positions were determined and speed of the train

Those skilled in the art will recognize, however, that if the tram is traveling on a curved section of track a simple kinematic calculation of the straight line distance between the end-of-train position and the front-of- train position will yield a tram length which may be significantly shorter than the actual or true tram length To compensate for this problem, the front-of-tram unit 204 may include a database 226 for storing reference information against which the determined end-of-train and front-of-tram positions may be compared This reference information preferably includes topographical information such as geo-referenced coordinates defining the path of the track on which the train is traveling When calculating the length of the train, the processor 224 may interrogate this data base 226 and correlate the determined geo-referenced end-of-train and front-of tram positions with the reference information stored in the database 226 to determine if the train is traveling aiong a straight or curved section of track The processor 224 may then apply an adjustment factor for the curvature of the track on which the tram is traveling to the calculation of the train's length This adjustment factor may be stored in the database 226 and retrieved by the processor 224 based on the

10 - determined front-of-tram and end-of-train positions

The processor 224 may further compare the determined end-of- tram position or front-of-tram position with a known coordinate position of a point along the track so that an appropriate indication or warning may be provided when the tram approaches or clears that point For example, the crew riding in the locomotive may be provided with an indication that the end of the train has compietelv cleared a siding or switch, for example A geo-referenced coordinate position of the siding or switch may be storeα in the database 224 As the train approaches the siding or switch, the processor 224 may compare the determined front-of-tram position with this coordinate position and provide an indication or warning to the crew that the tram is approaching a siding or switch As the tram passes the siding or switch, the processor may periodically compare the determined end-of-train position with the coordinate position and provide an indication or warning to the crew that the end of the train has cleared the siding or switch In this manner, safer, more precise handling of the train may be accomplished

It may be impossible, due to the design of the end car or lead locomotive to position the end-of-train unit or the front-of-tram unit at the precise end or front of the tram Consequently, a small error in the train length calculation may be introduced To compensate for this error, the processor 224 may apply an offset to the calculation of the train's length This offset may be entered into the database 226 for example, when the end-of-train unit 202 and front-of-tram unit 204 are installed

A display 226 such as for example, a liquid crystal display (LCD), cathode ray tube (CRT) display or the like may disDlay the length of the

1 1 - train to the crew of the lead locomotive Preferably, the length of the tram may be provided in alphanumeric or graphical formats For example, the display 226 may provide an alpha-numeric indication of the trains length such as, for example "900 feet" or "300 meters." The length of the train may also be displayed graphically by representing the tram on a map of the surrounding track. The display 226 may further provide warnings indicating that the tram is approaching or has cleared a point such as a siding or switch and may include an audible warning device such as a loudspeaker, siren, horn, or the like

Turning now to FIG. 3, a block diagram is shown illustrating a two- way end-of-train (EOT) system modified to operate in conjunction with apparatus of the present invention to determine the length of a tram Although a two-way EOT system is descπbed herein, those skilled in the art will recognize that other kinds of tram monitoring and control systems such as, for example, one-way EOT systems and distributed power or braking systems may be similarly modified .v.-n apparatus according to the present invention.

The EOT system 300 preferably comprises a cab unit 302 mounted in the cab of the tram's lead locomotive and an end-of-train (EOT) unit 304 mounted to the last car of the tram The EOT unit 304 may include a first transceiver 306 and antenna 308 for transmitting key last car status information monitored by the unit to a second transceiver 310 and antenna 312 in the cab unit 302 Preferably, the EOT system 300 provides crew riding in the cab of a locomotive with key end-of-train information such as, for example, brake pipe pressure 314 at the rear of the tram, end of train motion 316, EOT battery condition 318, and marker

12 -- light status 320 Tne cab unit 304 displays this information to the crew via a display 322 In addition to providing end-of-tram information to the crew, the EOT system 300 allows the crew to command the EOT unit 304, via the brake system 324 and cab unit 302, to release brake pipe pressure 314 at the rear of the tram thereby permitting simultaneous application of brakes at the front and rear of the tram

According to an exemplary embodiment of the present invention, the EOT system 300 may be modified to provide length of train information as an additional function A first GPS receiver 326 and antenna 328 may be operatively coupled to the processor 330 of the EOT unit 304 The GPS receiver 326 receives a reference signal from the Global Positioning System (GPS) The processor 330 of the EOT unit 304 may periodically determine a geo-referenced end-of-train position of the of end of the train utilizing this reference signal Preferably, the processor 330 also records the time when reference signal is received and the geo- referenced end-of-train position is determined The determined end-of- tram position and recorded time are preferably transmitted to the cab unit 302 via the EOT system's transceivers 306 & 310 and antennas 308 & 312

Similarly, a second GPS receiver 332 and antenna 334 may be operatively coupled to the processor 336 of the cab unit 302 Preferably, when the end-of-train position and recorded time are received by the transceiver 310, the processor 336 causes the second GPS receiver 332 to receive a reference signal from the Global Positioning System (GPS) The processor 336 may then use the reference signal to determine a geo- referenced front-of-train position for the front of the tram The processor

13 -- 336 may also record the time when the reference signal is received and the geo-referenced front-of-train position is determined. The processor 336 may then apply basic kinematic methods to determine the length of the train based on the determined front-of-train and end-of-train positions, recorded times when these positions were determined, and velocity of the train. The EOT system shown in FIG. 3 is not provided with a database for adjusting measurements taken on curved sections oτ tiack. Thus, the system as shown would only be capable of providing accurate train lengths along straight sections of track. However, the EOT system could be further modified to include such a database if desired.

It is believed that the method and apparatus for determining the length of a train of the present invention and many of its attendant advantages will be understood by the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely an explanatory embodiment thereof, it is the intention of the following claims to encompass and include such changes.

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