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Patent 2281604 Summary

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(12) Patent: (11) CA 2281604
(54) English Title: METHOD AND SYSTEM FOR PROXIMITY DETECTION AND LOCATION DETERMINATION
(54) French Title: PROCEDE ET SYSTEME DE DETECTION DE PROXIMITE ET DE DETERMINATION D'EMPLACEMENT
Status: Expired
Bibliographic Data
(51) International Patent Classification (IPC):
  • G01S 5/00 (2006.01)
  • B60T 8/00 (2006.01)
  • G06F 17/00 (2006.01)
(72) Inventors :
  • GROSS, ERIC (United States of America)
  • GUARINO, ANTHONY (United States of America)
  • EASTERLING, SCOTT (United States of America)
  • PEEK, ERNEST L. (United States of America)
  • ZAHM, CHARLES (United States of America)
  • REINHART, LEONARD (United States of America)
  • GOTFRIED, MICHAEL (United States of America)
(73) Owners :
  • GE-HARRIS RAILWAY ELECTRONICS, L.L.C. (United States of America)
(71) Applicants :
  • GE-HARRIS RAILWAY ELECTRONICS, L.L.C. (United States of America)
(74) Agent: OLDHAM, EDWARD H.
(74) Associate agent:
(45) Issued: 2005-04-12
(86) PCT Filing Date: 1998-02-20
(87) Open to Public Inspection: 1998-08-27
Examination requested: 2003-04-14
Availability of licence: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): Yes
(86) PCT Filing Number: PCT/US1998/003252
(87) International Publication Number: WO1998/037432
(85) National Entry: 1999-08-18

(30) Application Priority Data:
Application No. Country/Territory Date
60/038,889 United States of America 1997-02-21
60/034,210 United States of America 1997-03-03

Abstracts

English Abstract





A system and method for preventing collisions between vehicles, such as
railway vehicles, by exchanging data regarding track position
of the vehicles. By use of an on-board track database (550), the system
provides an indication of the distance between vehicles based not
on line-of-sight but on track distance. Additionally, a system and method for
accurately determining location of railway vehicles without
the use of a network of trackside indicators. The disclosed system uses a gyro
(530), tachometer (520), and a satellite position determination
system (510), along with a track database (550), to maintain highly accurate
estimates of measurement errors and track position.


French Abstract

Système et procédé servant à empêcher des collisions entre des véhicules, tels que des trains, ce qui consiste à échanger des données concernant la distance de ces trains sur les voies. L'utilisation d'une base de données (550) de distance située à bord du train, permet au système d'acquérir une indication de la distance entre des trains non basée sur la visibilité optique mais sur la distance sur la voie. L'invention concerne, de plus, un système et un procédé servant à déterminer avec précision l'emplacement de trains sans utiliser de réseau d'indicateurs latéraux. Ce système met en application un gyrophare (530), un tachymètre (520) et un dispositif (510) de détermination de position satellite, ainsi qu'une base de données (550) de distance, de façon à effectuer des évaluations continues extrêmement précises d'erreurs de mesure et de position sur les voies.

Claims

Note: Claims are shown in the official language in which they were submitted.




WHAT IS CLAIMED:
1. An on-board vehicle proximity detector comprising:
(a) means for determining the geographic position of a vehicle
carrying the proximity detector, said vehicle traveling along
a predetermined track layout;
(b) a database of track parameters of the track layout on which
the vehicle is traveling;
(c) means responsive to said database and said geographic
position determining means for determining the track
position of the vehicle;
(d) means for receiving from other vehicles wireless signals
including the track positions of the other vehicles;
(e) means responsive to said track position determining means
and said receiving means for determining the distance along
said track layout between the vehicle carrying the proximity
detector and each of the other vehicles from which track
positions are received; and,
(f) mean; responsive to said distance along the track
determining means for initiating an alarm if the determined
distance is less than a safe amount.


2. The proximity detector of claim 1 including means for transmitting
the track position of the vehicle carrying the proximity detector via
a wireless link.
3. The proximity detector of claim 1 further comprising:
(g)means for automatically initiating a braking action if a crew of
the vehicle fails to respond appropriately to the alarm.
4. The proximity detector claim 1 further comprising:
(h)means for automatically disabling said means for automatically
initiating a braking action at predetermined locations along said
track layout.
5. The proximity detector of claim 1 further comprising:
(i) means for automatically disabling said means for automatically
initiating; a brake action whenever the speed of the vehicle is
below a threshold level.
6. The proximity detector of claim 2 wherein the transmission of the
track position is performed periodically at plural periodic rates,
one of said periodic rates being used when the vehicle is at some
portions of the track layout and others of the periodic rates being
used when the vehicle is at other portions of the track layout.



7. The proximity detector of claim 1 wherein said database includes a
table of successive geographic boxes, each of said boxes being
associated with a different position along said track layout.
8. The proximity detector of claim 7 wherein some of said
geographic boxes represent geographic areas having a first size
and others of said geographic boxes represent geographic areas
having a second size, said first size being different from said
second size.
9. The proximity detector of claim 7 wherein each of said boxes is
defined by a line of longitude and a line of latitude.
10.The proximity detector of claim 7 wherein the size of some of said
geographic boxes is determined, at least in part from the area of
uncertainty associated with said geographic position.
11.A method for determining the location of a railway vehicle along a
track in a track layout having plural parallel tracks for at least a
portion thereof and having switches between some of said parallel
tracks, said railway vehicle comprising a satellite positioning
system, a gyro, a linear position estimating device and a track
database, comprising the steps of:
(a) providing an approximate location of the vehicle from the
satellite positioning system;


(b) determining from the track database all track paths within a
specified area of uncertainty from said approximate
location;
(c) establishing a Kalman filter for each determined track path,
each of said filters monitoring the difference between the
vehicle's heading as measured by said gyro and heading
data stored in the track database;
(d) monitoring at each Kalman filter as the vehicle moves along
the track for residual differences in the heading state;
(e) upon a residual difference exceeding a specified threshold,
value, eliminating the associated track path as one of the
track paths; and,
(f) upon reduction of the number of track paths to one,
declaring the associate path to be the path along which the
vehicle is traveling.
12.A proximity detection system for a vehicle having an identification
associated therewith and traveling along a predetermined track
layout comprising:
(a) a satellite positioning system which provides signals
indicating the geographic location of the railway vehicle;


(b) a track database which includes data regarding the track
used by the railway vehicle, said track including plural track
segments, and said data including the geographic position of
track segments and the heading of track segments;
(c) tachometer measuring the revolutions of one or more of the
wheels of the vehicle for providing the position of the
vehicle along the track;
(d) a gyro for providing the change in heading of the vehicle;
and,
(e) filter which receives the signals indicating the geographic
location, the position of the vehicle along the track the
heading of the vehicle and the track database to provide an
estimate of the error in said geographic position the error in
said heading and the error in said position of the vehicle
along the track to determine the track position of the
vehicle;
(f) means for transmitting via a wireless link said identification
and said track position;
(g)means for receiving wireless signals from other vehicles,
said wireless signals including the identifications and track
position of said other vehicles;


(h)means for determining the distance along said track layout
between said vehicle and said other vehicles; and
(i) means of initiating an alarm if the determined distance is
less than a predetermined amount.
13. The proximity detection system of claim 12 further comprising:
(f) means for automatically initiating a braking action if a crew of
the vehicle fails to respond appropriately to the alarm; and
(g)means for automatically disabling said means for automatically
initiating a braking action at predetermined locations along said
track layout.
l4.The proximity detector of claim 1 wherein said safe amount is a
predetermined distance.
15.The proximity detector of claim 1 wherein said safe amount is
determined, at least in part, from the expected braking distance of
said vehicle. said expected braking distance including an
assessment of the grade of the track.
l6.The proximity detector of claim 2 herein the means for
transmitting and the means for receiving comprise a digital RF
communication processor.



17.The proximity detector of claim 1 where the means for
determining the distance along said track and the means for
initiating an alarm comprise a proximity detection computer.

18.A railway vehicle location determination system comprising:
(a) a satellite positioning system which provides signals
indicating the geographic location of the railway vehicle;
(b) a track database which includes data regarding a track layout
used by the railway vehicle, said track layout including
plural track segments each having an associated mileage
point, and said data including the geographic box associated
with each mileage point;
(c) a computer which compares the geographic location of the
railway vehicle with said geographic boxes to select the
geographic box in which the geographic location of the
vehicle is located; and,
(d) a display for displaying the mileage point associated with
the selected geographic box.

19.The location determination system of claim 18 wherein the size of
said geographic boxes is based on said track layout and the
uncertainty of the measurement of the location.



20.The location determination system of claim 18 wherein the size of
said geographic boxes are defined by longitude and latitude.

21.A railway vehicle location determination system comprising:
(a) a satellite positioning system which provides signals
indicating the approximate geographic location of the
railway vehicle;
(b) a track database which includes data regarding the track
used by the railway vehicle, said track including all track
paths within a specified region of uncertainty for said
approximate position, and said data including the
geographic position of track segments and the heading of
track segments;
(c) a tachometer measuring the revolutions of one or more of
the wheels of the vehicle for providing the position of the
vehicle along the track;
(d) a gyro for providing the change in heading of the vehicle;
(e) a Kalman filter for each track path with the specified region
of uncertainty which receives the signals indicating the
geographic location, the position of the vehicle along the
track, the heading of the vehicle and the track database to
provide an estimate of the error in said geographic position,




the error in said heading and the error in said position of the
vehicle along the track; and
(f) a turn out processor for comparing the turn rate and the
heading from said gyro with the turn rate and heading from
said track database to determine which of said track paths
the vehicle is traveling.

Description

Note: Descriptions are shown in the official language in which they were submitted.



CA 02281604 2004-07-15
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METHOD AND SYSTEM FOR PROXIMITY DETECTION AND LCOATION
DETERMINATION
BACKGROUND OF THE INVENTION
The present application is related generally to systems and methods
for preventing collisions between vehicles on railway systems and, in
particular, to systems and methods for determining accurate locations of
railway vehicles and/or for providing proximity warnings or brake applications
when a collision threat is detected.
A long-standing problem in the railway industry has been the
competing interests of maximizing throughput on the railway system while
maintaining sufficient separation of the vehicles to prevent collisions.
Significant time and resources have been expended towards developing
proximity detecting aystems which alert vehicle operators to potential
collision
threats. The typical proximity detection system includes the capability of the
system to take automatic action to stop the vehicle should the operator not
take the required action in response to a proximity warning.
Generally, in such prior art systems the location, speed, direction of
travel and identification number of each vehicle is collected. This
information
may then be analyzed to determine which vehicles present a collision threat
to one another. Once a vehicle is determined to be a collision threat, the
proximity

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detecting systems will issue a proximity warning once the trains
come within a predetermined threshold distance to each other.
For example; if a train is travelling northbound on a track
towards point A and a second train is travelling southbound on
the same track to point A, a prior art proximity detecting system
would issue a proximity warning to each train as the trains got
within a certain distance of one another. Similarly, if two
trains were travelling on the same track in the same direction
and the trailing train was travelling at a faster speed than the
lead train, a proximity warning would be issued when the distance
between the two trains decreased to a certain predetermined
threshold distance.
A common characteristic of the prior art proximity detection
systems is the automatic enforcement braking if the proximity
warning is not acknowledged by the operator. For example, many
prior art collision avoidance systems require that the operator
acknowledge the receipt of the proximity warning within a certain
amount of time or the proximity detection system initiates
enforcement braking to cause the train to come to a complete
stop.
Some prior art proximity detection systems require more than
mere acknowledgement of the proximity warning. For example, one
such prior art system requires the operator of the train
receiving the proximity warning to establish voice communications
with the identified collision threat train in order to satisfy
the warning acknowledgement and prevent automatic braking of the
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train. See, for example, the Hsu U. S. Patent No. 5,574,69
issued November 12, 1996.
Another general characteristic of many of the prior art
proximity detection systems is that there may be more than one
predetermined threshold distance. For example, when two vehicles
are determined to be a collision threat and come within some
predetermined threshold distance, a proximity warning is issued
to each vehicle. If the distance between the trains should
subsequently decrease to a second predetermined threshold
distance, a second proximity warning may be given. This second
proximity warning may have associated with it some additional
required action of the operator. For example, an operator of a
train may receive a proximity warning when it is determined that
his train and another train pose a potential collision threat to
each other and the distance between the two trains has decreased
to eight miles. The operator may be required to acknowledge the
alarm by depressing an acknowledgement button. If the
acknowledgement button is not depressed within a set amount of
time of receiving the alarm, the train may initiate proximity
enforcement braking commands automatically. If the operator
acknowledges the proximity alarm but the distance between the two
trains decreases to five miles, a second proximity warning may be
issued. This second warning may have associated with it,
required action from the operator in addition to acknowledging
the alarm, such as reducing the speed of the train. In a similar
manner, there may be multiple predetermined threshold distances
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each with an associated required operator action in order to
prevent the proximity detecting system from initiating
enforcement~braking commands to slow the train.
In order to prevent continuous unwanted alarms and
enforcement actions in an area where trains are commonly within
the proximity warning threshold (i.e., railyards) it is common
for the prior art systems to offer a method of allowing the
operator to manually disable the proximity detection system.
However, the ability to disable the proximity detection system
may lead to the inadvertent disablement of the system when the
train leaves an area of congestion. Additionally, because of the
severity of the resulting action if a proximity alarm is not
acknowledged, there may also be situations when the vehicle
operator would prefer to receive a proximity warning but would
want to prevent an enforcement action.
A significant decrease in the net worth of a proximity
detection system occurs if the system can not minimize false
alarms. This is particularly true if the false alarm leads to an
enforcement action which may have ramifications to the schedules
of the entire railway system. For example, a vehicle that is
following another vehicle at approximately the same speed and at
a distance approximately equal to one of the predetermined
threshold distances may cause a proximity alarm if the vehicle
closes to less than the threshold distance. The alarm may clear
if the trailing vehicle falls beyond the threshold distance. If
the trailing vehicle subsequently closes within the threshold
4


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distance again a second proximity alarm would then be received.
Without some method of screening out those situations where a
continuous alarm may be expected, the operator may become de-
sensitized to the importance of the proximity alarm. As a
result, the operator may not acknowledge the "expected" alarm,
inadvertently resulting in an enforcement action and unscheduled
stopping of the vehicle.
Inherent in the operation of railed vehicles is conflict
with not only other vehicles on the railway system but also non-
railway system vehicles whose path may cross the path of a
vehicle system on a railway (i.e., a railway crossing which
allows automobiles to cross over the train tracks). Various
systems have been developed which will warn the non-railway
vehicle of the impending approach of the railway system vehicle.
Generally, in such prior art systems, a wayside centric
approach is taken to warn vehicles of an approaching train. For
example, a train may continuously transmit a signal at a pre-
determined signal strength along the direction of movement of the
train. Wayside receivers located at, the railway crossing will
receive the signal as the train approaches the crossing. When
the signal is received, the wayside unit may cause warning bells
to ring, or warning lights to activate or crossing gates to close
(or any combination of the three). Upon seeing and/or hearing
the warning signals, an operator of a non-railway vehicle will
know a train is approaching the crossing. While this warning
system has proven effective at rail crossings, it is not an

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effective method of preventing collisions between vehicles where
both vehicles are travelling on the same track. For instance,
one characteristic of the prior art warning systems of this type,
is that the actual location of the train is not determined nor
utilized. Rather the relative location of the train with respect
to the crossing is instrumental in activating the warning system.
The warning signal transmitted by the train is usually a fixed
signal of sufficient range to take into account expected
propagation losses such that even in a worst case propagation
loss environment', the warning signals will be activated in
sufficient time to warn~and/or prevent non-railway system
vehicles from colliding with the train at the crossing.
Unlike the previously described proximity warning systems
which are utilized to warn non-railway system vehicles of the
approach of a railway vehicle, a proximity detection system that
prevents collisions between railway system vehicles requires the
accurate determination of location of each vehicle in the railway
system. A system that can not accurately determine the location
of the vehicles, will be forced to factor in a large margin error
to ensure that collisions do not occur and as a result the
vehicles will be spaced more than they need to be, thereby
reducing throughput on the railway system.
It is known in prior art railway proximity warning systems
for the system to display to the operator of the locomotive the
location of the locomotive, and of other potentially conflicting
locomotives. Generally, such locations are determined and
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__~. ......._._.. . _...__r.t_.__._ _~..~...__ . ___._...__..._.__ .,


CA 02281604 1999-08-18
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displayed in geographic coordinates, such as latitude and
longitude. In some situations, the system may also display the
d~.stance between the various locomotives, often calculating the
distance based on the signal strength of the location signals
received from other locomotives or from the geometric
relationship between the geographic coordinates of the
locomotives. Use of signal strength as the measure of distance
between locomotives is often beset with varying signal
transmission difficulties which may make more difficult an
accurate determination of the actual distance between the
locomotives. Moreover, in both signal strength and geometric
calculations, the measure of the distance between the locomotives
is usually a "line of sight" distance. Such a measure may be
sufficient when the locomotives are on relatively straight
sections of the same or parallel track; but, where the track has
a considerable curvature, the distance along the track between
two locomotives may be somewhat different from the line of sight
distance. Because the criticality distance between locomotives
is usually the distance "along the track", a system which uses
merely signal strength or geometric calculations may signal an
alert when none is necessary; i.e., while the locomotives are
within the threshold distance of each other along the line of
sight, they are further apart as measured along the track.
Prior art location determination systems (LDS) disclose
various methods for determining the location of vehicles on a
railway system. Wayside units and local detectors are well known
7

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systems in the prior art and provide an accurate location of
railway vehicles, but the detection systems are expensive to
acquire, install, and maintain, particularly in harsh
environments.
LDS systems using satellite based systems are also well
known. The Global Positioning System (GPS) and other satellite
based location determining systems have been available and in use
for a number of years (the term GPS is used hereafter to denote
any positioning system which uses satellites and has capabilities
similar to those of the GPS system.) Use of GPS systems with a
wide variety of vehicles, including trains, is known to the
field. Also known to the field are the inherent limitations of
GPS use.
An accurate GPS location determination. requires a GPS
receiver to receive signals from four different GPS satellites.
A train or any other vehicle can easily receive signals from the
four required satellites if the vehicle is located in an open
area, free of signal obstructions. For this reason, ships at sea
and airplanes in flight are well positioned to make full use of
GPS to accurately determine their location. A train located in
an open area can similarly receive signals from the required four
satellites. However, trains are not always so conveniently
located.
The very nature of train travel is such that trains will be
found in locations where they cannot easily receive from four
satellites. Trains travel next to tall, signal obstructing
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structures, both natural and man-made. Trains travel through
canyons and other areas which interfere with signal reception.
As such, trains are often in the situation, unique from some
other forms of mass and freight transit, in which they can
receive signals from fewer than the required four satellites, and
frequently can receive signals from only two satellites.
Obviously, there are other methods for determining the
location of a vehicle. Particularly with respect to rail-based
transportation, it is possible for a vehicle to have access to a
database of information pertaining to rail routes whose locations
are fixed and known. Such a database may be used to provide a
way of converting elapsed distance from a known point along a
known route into a location in two or three dimensional
coordinates.
Such a system is well suited to rail vehicles by virtue of
the fact that these vehicles cannot stray from their fixed and
known tracks. The advantages of such a system are limited by its
logistics, however. In order to know the distance traveled from
a fixed point, an odometer type of measurement must be taken.
Such a measurement is generally taken by counting wheel
rotations, which is fraught with inaccuracies: wheels slip on
rails, potentially both during acceleration and braking; wheel
diameter changes over time as wheels wear down and develop flat
spots; any wheel rotation measurement and calculation method is
inherently at least partly mechanical, thus subject to mechanical
problems; all such measurements are based on correctly resetting
9

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a counter at a designated zero point from which such measurements
are taken, which might not be easily performed; and independent
of the ability to measure distance travelled, the entire system
is subject to the accuracy of the initial database upon which the
final location determination is based.
It is desirable to combine the best features of satellite
based and elapsed distance based location determination methods.
Such a system could approximate a rail vehicle's location based
on a track database to within some range of error. This estimate
could be used as the basis for a satellite based measurement
which takes into account not only the estimated location of the
rail vehicle, but also the relative location of nearby
geosynchronous satellites. Such a system need not have access to
the full four satellites normally required.
While the typical prior art location determination systems
require three or more satellites to achieve the accuracy required
to efficiently plan train movement, recent developments in
technology have allowed accurate location determination system
with fewer than three satellites. A further explanation of how
to determine location with as few as two satellites is disclosed
in the Zahm et al. U.S. Patent Application Serial No. 08/733,963,
filed October 23, 1996, entitled "Application Of GPS To A
Railroad Navigation System Using Two Satellites And A Stored
Database", to which this application is a continuation-in-part
application.
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Most prior art location determination systems are unable to
distinguish between parallel tracks situated close together. For
example, a train may be directed to a siding for a planned "meet
and pass" with another train. Because the siding is parallel and
located adjacent to the main track, the typical location
determination system can not determine whether the train is on
the main track or the siding. If this location position was then
entered into a proximity warning system, the proximity system may
indicate a collision situation between two trains, when in
actuality the trains are correctly positioned for a meet and
pass.
Because the typical proximity detection systems determine
the location of each vehicle, it is possible to calculate the
"line of sight" distance between the vehicles. This distance
combined with the speed and direction of each vehicle enables the
proximity detection systems to determine which vehicles pose a
collision threat to each other. However, the collision threat
determination of the typical prior art system may not always be
accurate. For example, the determination of the actual location
of two trains will permit the "line of sight" distance between
the two trains to be determined. However, because the trains are
constrained to operate on railway tracks, and the railway tracks
may not run in a straight line between the two trains, the actual
track distance between t-.he two trains may differ significantly
from the "line of sight" distance. Similarly, some prior art
proximity detection systems do not take into account that the
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vehicles may be travelling on separate non intersecting tracks so
that although the vehicles appear to be travelling towards each
other, there is no opportunity for a collision because they are
on separate tracks.
Regardless of the type of LDS system used, the location of
the vehicles on the railway system is necessary component in the
typical proximity detection system. The more accurate the
location determination, the more closely that vehicles can be
positioned together because the margin of error is reduced
without having to account for the uncertainties of vehicle
locations.
Accordingly, it is an object of the present invention to
provide a novel of method and system for controlling railway
vehicles which obviates these and other known difficulties in
collision avoiding and location determining systems for railways.
It is a further object of the present invention to provide a
novel of method and system for controlling railway vehicles which
increases the throughput of vehicles on a railway system while
minimizing collisions between the vehicles.
It is another object of the present invention to provide a
novel method and system for controlling railway vehicles which
determines the track distance between vehicles on a railway
system.
It is yet another object of the present invention to provide
a novel method and system for controlling railway vehicles by
automatically disabling the alarming and the enforcement function
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of a proximity detection system based upon the location or the
speed of the vehicle.
It is still another object of the present invention to
provide a novel method and system for controlling railway
vehicles by manually disabling the enforcement function of a
proximity detection device without disarming the warning feature.
It is a further object of the present invention to provide a
novel method and system for controlling railway vehicles by
reducing the number of expected alarms received from the
proximity detection system.
It is yet a further object of the present invention to
provide a novel method and system for controlling railway
vehicles by differentiating railway vehicle locations between
closely positioned track paths.
It is still a further object of the present invention to
provide a novel method and system for controlling railway
vehicles by improving the accuracy of their location
determination systems.
It is yet another object of the present invention to provide
a novel method and system for determining and displaying railway
vehicle information consistent with railway operating practices.
These and many other objects and advantages of the present
invention will be readily apparent to one skilled in the art to
which the invention pertains from a perusal of the claims, the
appended drawings, and the following detailed description of the
preferred embodiments.
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BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a simplified block diagram of the major
components o.f the Proximity netection Device (PDD) system and
method of the present invention.
Figure 2 is a simplified block diagram of a PDD processor
which can be used in the system of Figure 1.
Figure 3 is a simplified pictorial representation of a PDD
display unit which can be used in the system of Figure 1.
Figure 4 is a simplified block diagram of the LDS which can
be used in the processor of Figure 2.
Figure 5 is a simplified lock ~agram of the data and
signal flow through the LDS o Figure 4.
Figure 6 is a simplified block diagram of an implementation
of the LDS of Figure 4.
Figure 7 is a simplified block diagram of an implementation
of the velocity filter of Figure 6.
Figure 8 is a simplified pictorial representation of a track
layout which can be used in the system of Figure 1.
Figure 9 is a simplified pictorial representation of a track
boundary box which can be used in the LDS of Figure 2.
Figure 10 is a simplified pictorial representation of a
track boundary box which can be used in the LDS of Figure 2.
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DESCRIPTION OF PREFERRED EMBODIMENTS
With reference to Figure 1, the components of the proximity
detection d2vice (PDD) may all be located on a single vehicle and
may include a PDD processor 200, a display unit 210, an event
recorder 230, and a human/machine interface 220 which can be used
to receive inputs from a person controlling the vehicle.
In operation, the PDD processor 200 receives and compares
the location data from vehicles on the railway system and
compares it to the location data for the vehicle on which it is
installed (platform vehicle). The PDD processor 200 can provide
the vehicle information to the display unit 210 so that the
vehicle operator is aware of vehicles of concern. The PDD
processor 200 analyzes the vehicle information and generates a
warning which activates an alarm on the display unit 210 if a
collision threat exists. The alarm may be aural as well as
visual. The human/machine interface (HMI) 220 allows the
operator to acknowledge alarms and control the operation of the
proximity detection system. Such control commands may include a
remote acknowledgment and disabling all or a portion of the PDD.
The event recorder 230 may be connected to the PDD processor 200
which may record all information and alarms as well as subsequent
enforcement actions taken by the proximity detection system or
taken by other PDD equipped vehicles. The event recorder may be
a conventional event recorder which is well known in the railway
arts.

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With reference to Figure 2, the PDD processor 200 may
include a PDD computer 300, a location determination system (LDS)
310, a communication processor 320 and a track database 330. The
track database 330 contains specific information for the railway
system serviced by the PDD system and may include one or more of:
the location of all possible railway track paths, milepost
markers, switches, curve data, grade profile, railyard
boundaries, signal locations and speed restrictions. Vehicle
sensors 340 provide the PDD computer 300 with the necessary
information to determine vehicle speed and direction of travel.
In operation, the LDS 310 determines the geographic location
of the vehicle, such as the longitude and latitude of the
vehicle, and sends this information to the PDD computer 300. If
needed, the PDD computer 300 converts the geographic location
from the LDS 310 to a specific mile post number of the railway
system based on information retrieved from the track database
330. For additional accuracy, cross=checking and safety, the PDD
computer 300 may also receive inputs of the vehicle's direction
of travel and velocity from vehicle sensors 340.
With continued reference to Figure 2, the communications
processor 320 may receive signals indicating the location of
other, similarly equipped vehicles, and may provide such vehicles
with signals indicating the location of the vehicle on which it
is installed. The information transmitted (and received from
other vehicles) by the communications processor 320 may include
the vehicle's identification number, its location (geographic or
16
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by mile post), its direction of travel and its speed. The
communication processor 320 may transmit vehicle information as a
digital RF signal. In order to reduce the bandwidth required to
transmit vehicle location, the communication processor 320 may
transmit vehicle location as a milepost location rather than a
latitude and longitude position because the milepost location may
require fewer digits of information. The transmission of
milepost information may also require less processing by the
receiving PDD in order to compute distances.
After receiving the location of other vehicles from the
communications processor 320, the PDD computer 300 may then
access the track database 330 to determine which vehicles pose a
collision threat. The PDD computer 300 will initiate a proximity
alarm if the track distance to any vehicle identified as a
collision threat is less than the predetermined threshold
distance. By accessing the track database 330, the PDD computer
300 is able to determine the track distance (as opposed to the
line of sight distance) between the PDD platform vehicle and all
other vehicles. If the~operator does not acknowledge the
proximity alarm through the HMI 220, the PDD computer 300 may
issue a penalty brake command to the brake control system to stop
the platform vehicle. Upon enforcement application of the
braking system by the PDD computer on an equipped vehicle, the
communications processor 320 may immediately broadcast a message
to other equipped vehicles in the railway system. A message
indicating that enforcement braking has taken place on another
17

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vehicle in the proximity of a train may be displayed on the
display unit 210 and may be accompanied by an aural alarm.
When an alarm is sounded and cleared by the operator, the
PDD may use hysteresis to avoid unnecessarily sounding the alarm
again for a trains that have remained relatively fixed in
position with respect to each other. Thus, for following trains
which are approximately the alarm distance apart from each other,
the alarm will not be restarted merely because the distance
between the trains fluctuates around the alarm trip point. The
hysteresis can be implemented either on the basis of distance
between the trains or the time that the trains have spent at
approximately the same distance.
In an alternative embodiment, the alarm can be triggered not
strictly on the basis of distance but also on the basis of speed
and/or expected train braking distance. While such an embodiment
may require the transmission of additional data between trains,
the proximity warning system in this embodiment may avoid
unnecessary warnings. For example, a train following along the
same track at a relatively slow speed may not be considered as
much of a collision danger as a train travelling at a higher
speed. The PDD may set different alarm points for the trains
depending upon their speed, the track conditions (wet or dry,
etc.), the grade of the track, and/or the expected braking
distance for the particular train.
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In a preferred embodiment, the PDD computer 300 may also
control the mode of the PDD based upon a preestablished set of
guidelines.' For example, when a train enters a railyard or other
area of known traffic congestion, the continuous sounding of
proximity alarms and the potential enforcement braking
application may be distracting and detrimental to the safe
operation of the train, yet it may be desirous to continue to
display vehicle location information. The geographic limits of
the railyards and other high traffic areas may be entered into
track database 330. Accordingly, if the PDD computer 300
determines that the vehicle has entered the boundaries of a
railyard, the PDD computer 300 may automatically disable the
automatic alarm and enforcement braking features of the proximity
detecting device while maintaining the broadcasting, receiving
and displaying of information. When the PDD computer 300
determines that the vehicle has left the boundaries of the
railyard, the PDD computer 300 may enable the automatic
enforcement braking feature. Similarly, PDD computer 300 may
disable the automatic enforcement braking feature when it senses
that the vehicle's speed is less than some predetermined
threshold. Accordingly, at slow speeds, where automatic
enforcement action may not be as crucial, the PDD computer 300
may prevent the disruptive effect of an unintended braking
application.
The presence of multiple PDD equipped vehicles in close
proximity such as a railyard may also result in a degradation of
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the communications environment due to transmission congestion.
In a preferred embodiment, if the PDD computer 300 may reduce the
rate at which transmissions of vehicle data are transmitted by
communications processor 320. For example, if PDD computer
determines it has entered the boundaries of a railyard as
described above, the PDD computer 300 may direct the
communication processor 320 to transmit platform vehicle
information once per minute rather than the transmission rate
outside the railyard boundary of once per three seconds.
In a preferred embodiment of the present invention, the
vehicle operator may manually control the operation of the PDD
through the HMI 220. For example, a PDD locomotive may be used
in conjunction with other PDD equipped locomotives in a single
consist in a distributed power arrangement. The operator may
command the PDD for each trailing locomotive to a passive mode.
When the PDD is in a passive mode, the communications processor
320 may still receive transmissions and display unit 210 may
still display received information but the communications
processor 320 may not transmit platform vehicle information and
the PDD computer may disable the proximity warning and
enforcement features.
Similarly, the operator may use the HMI 220 to specify to
the PDD that the locomotive is currently on a siding (or
conversely on the main track). The PDD can use this information
to determine whether to raise an alarm and the urgency of such an
alarm. For example, a train wholly within a siding, may be
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considered not to be a collision threat to trains on the main
line. The PDD can operate to automatically change a siding
designation ~to the main line when, for example, the location
determination system determines that the train has travelled past
the end of the siding. Under these circumstances, the PDD can
automatically change the "siding" designation to show that the
train has re-entered the main line.
Figure 3 represents a specific embodiment of the PDD display
unit 210. The display unit 210 may have the capability to
display the following information:
ID -- unique vehicle identification number
MP -- mile post location of the vehicle
TRAK -- M/T (Main), SDG (siding), yard identification number,
LOST ( GPS f ai lure ) or OUT ( out of PDD range )
DIST -- track distance from active vehicle
D -- direction of other vehicle from platform PDD
T -- direction of travel of vehicle
SP - speed of vehicle
STATUS - NORMAL, ALARM, NAP, or BRAKES
AGE - age of information displayed
The presentation of the information on display unit 210 may
generally be consistent with standard railway operating
practices. For example, the direction of travel of each vehicle
(N, S, E or W) is derived from the ascending or descending
mileage as determined from the track database 330, as opposed to
a direction of travel determined from point to point GPS fixes.
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This direction of travel corresponds with the direction of travel
as listed in standard railway timetables. Accordingly, if a
vehicle is travelling along a railway path that is defined as
South in the railway timetable, the display unit will display a
"S" for direction of travel, even if the vehicle is temporarily
heading or moving to the north due to the changing direction of
the track (i.e., switchbacks). Similarly, the location of the
vehicles may be displayed by milepost which may be more familiar
to the vehicle operator rather than a latitude and longitude
position.
With continued reference to Figure 3, line item displays 400
represent the information for the four closest vehicles to the
platform vehicle. Line item display 405 represents the platform
vehicle information. Display unit 210 may provide the vehicle
operator with the sufficient information to identify each vehicle
that may pose a collision threat as well as provide sufficient
prompting to avoid a potential collision. For example, the
information represented on display lines 400 have associated with
it a column representing the age of the data being displayed. If
for some reason communications is lost with any of the vehicles
being displayed, the age of the data displayed for that vehicle
will indicate that the information displayed may no longer be
current. Additionally, the display may also be able to indicate
when a vehicle, either the platform or other displayed vehicle,
has left the area where the PDD coverage is operable.
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The specific implementation of the PDD data unit shown in
Figure 3 is illustrative only and not intended to be limiting.
Those skilled in the art will understand that other specific
embodiments of the data unit may be implemented within the
teachings of the present application and the scope of the present
invention.
With reference to Figure 4, one specific embodiment of the
location determination system (LDS) provides for a solution of
heading, speed and vehicle position that arises from optimally
fusing the outputs of four different sensors in a Kalman filter
500, coupled with track correlation data from a track database
550. The four sensors may include a GPS 510, tachometer 520,
gyro 530 and accelerometer 560. The LDS may also use a turn out
processor 540 to identify which of several possible track paths
the vehicle may be travelling. By blending the above sensors
together with the track database 550, the turn out processor 540
is able to determine which of several candidate tracks it can be
located on by using very accurate gyro inputs into the Kalman
filter 500 to ascertain when a switch is taken.
The track database 550 may include data representing the
identification of the track (as used by the railway, including
timetable direction), the location of the track segments
(latitude and longitude), the curvature of the track segments
(including switches), the grade of the track, control points and
switch locations. The heading and/or elevation of the track at
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various locations can be computed from the curvature and/or grade
data points or (for ease of computation) may be stored.
In operation, the Kalman filter 500 may be a seven state
extended Kalman filter that processes up to ten measurements.
The measurements may consist of the pseudorange errors from up to
8 GPS satellites obtained by subtracting the GPS provided
pseudorange from the calculated pseudorange based on satellite
location and location derived from the track database 550,
heading errors obtained from subtracting the heading obtained
from the track database 550 from the heading obtained from the
gyro 530, and a position error which is generated when the train
takes a switch or a well defined turn, by subtracting the
estimated location of the turn as derived from the tachometer 520
from the location of the turn obtained from the track database
550. The output of the Kalman Filter 500 consists of the
following error estimates:
position error along track, velocity error along track, heading
error, gyro bias correction, tachometer scale factor error, GPS
receiver clock error and GPS receiver clock frequency error.
These error estimates are then fed back to the various sensors to
make the appropriate corrections.
With continuing reference to Figure 4, the LDS may use a
specific method of track matching to determine which of several
possible track paths a vehicle is travelling. For example, LDS
uses GPS 510 to provide an approximate location of the vehicle.
The track database 550 may then provide all track paths within a
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specified region of uncertainty for the approximate position of
GPS 510. The specified region of uncertainty is a function of
the Horizontal Dissolution of Precision (HDOP) of the GPS point
solution. A separate Kalman filter is established for each
possible track path contained within the region of uncertainty.
As the vehicle travels down the track, each Kalman filter
monitors the residuals in heading state. For each Kalman filter,
as the residual difference between the heading from the track
database 550 and from the gyro 530 exceed a predetermined
threshold, that possibls track path is eliminated. When all
possible track paths are eliminated but one, the LDS declares
that it has determined which track the vehicle is located and
where on that track the vehicle is positioned. As the vehicle
continues down the track, the Kalman filter 500 continues to
identify the current region of uncertainty. When switches,
identified in the track database 550, move into the current
region of uncertainty, separate Kalman filters are established,
one for each path. The turn out processor 540 retrieves from the
track database the expected turn rate for each track path. The
turn out processor 540 compares the turn rate from the gyro 530
with the expected turn rates from the track database 550 and
compares the heading derived from the gyro 530 with the expected
heading from the track database 550 to verify which track path
the vehicle has taken. Once the turn out processor 540 has
determined which track path the vehicle has taken, the filter for
the other path is eliminated.


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This method of track matching enables the LDS to distinguish
between multiple track paths similarly situated in close
proximity. For example, in a meet and pass situation, one train
may be directed on to a siding (which is parallel and adjacent to
the main track) to allow another train to pass on the main track.
Without a method to differentiate between the train locations on
these two paths, the proximity detection system would initiate an
unnecessary proximity alarm.
With reference to Figure 5, the flow of data and signals
through an LDS in accordance with one embodiment of the present
invention may be illustrated by the simplified functional block
diagram of Figure 5. With reference to Figure 5, the speed of
the vehicle acts on the on board sensors within the Along Track
Navigation function 800 to produce a change in position over a
given time period. The change in position (along the track)
during the time period can be applied to logic circuits 805 which
update the last estimate of position along the track (latitude,
longitude, heading, altitude) and the track database to determine
an update position estimate (latitude, longitude and altitude)
and an updated heading estimate. The position estimate may be
converted to a three-axis, earth-centered estimate (X, Y, Z
coordinates) and compared to an estimate of the position
concurrently received from a GPS system 810. The two position
estimates may be compared to develop pseudorange errors which are
input to the Kalman filter.
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Similarly, the heading estimate received from the track data
base may be compared by a Heading Error process 815 to the
heading obtained from the gyro. This heading error can likewise
be provided as an input to the Kalman filter. Finally, the
change in position (along the track) as determined by the
tachometer and associated logic circuits may be provided to the
Kalman filter.
A specific implementation of the LDS 310 in accordance with
the present invention is illustrated in Figure 6 in which similar
elements to those in the system of Figure 4 bear the same
reference numeral. A gyro 530, such as a digital gyro, along
with a gyro interface 620 may be fixedly mounted to a vehicle and
provide signals indicating a rate of turn being experienced by
the gyro (and the vehicle). The rate signals may be adjusted by
a current gyro bias and rate error and integrated over time to
provide an estimate of the current heading. The results of the
heading determination may be correlated by a track correlator
which compares the heading obtained from the gyro 530 to a
heading expected from the curvature of the track (as obtained
from the track database 550). The output of the track correlator
630 may include an estimate of the position error and a
correlation coefficient which can be provided to the Kalman
filter 500 and an identification (or confirmation) of the track
over which the vehicle is running.
Simultaneously with the operation of the gyro 530, the LDS
may use the wheel tachometer 520 to provide an estimate of the
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velocity of the vehicle. The output from the tachometer 520 may
be accumulated by a pulse stream accumulator 635 and provided to
a tachometer scaler 640 which computes the velocity from the
tachometer counts, taking into account the bias provided by any
changes in wheel diameter. The determined velocity may be
provided to a velocity filter 645 which adjusts for the current
estimate of the velocity error along the track. An accelerator
560 fixed to the vehicle may provide an output to a signal
conditioner 660 which is then converted to a digital signal by an
analog/digital converter 670. The digital acceleration signal is
provided to the thermal and gravity preprocessor 680 to correct
for the temperature and for the grade of the track the vehicle is
traveling. This corrected acceleration signal is input to the
velocity filter 645 to determine velocity bias due wheel slip.
The filtered velocity measurement may be provided to an
integrator 648 which determines the position of the vehicle along
the track, adjusting for the current position error estimate.
The measured position of the vehicle along the track can be used
by the track data base manager and the track correlator 630 to
coordinate the measured position and heading information.
With continued reference to Figure 6, the LDS may also
include a satellite based position determining system, such as a
GPS system 510. If desired for improved accuracy, the position
determining system may be a Differential GPS system, as in known
in the art. Depending upon the number of satellites visible at
any one time to the DGPS 510, the DGPS provides a measurement of
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the pseudorange from the DGPS receiver (on the vehicle) to the
satellites. The pseudoranges and the ephemeris of the positions
of the satellites may be used by a GPS processor 655 to provide
an estimate of the vehicle's location (in latitude, longitude,
altitude and velocity). In addition, the DGPS estimate of the
position of the vehicle may be compared to the estimate of the
position obtained from the track database 550 to provide
pseudorange error estimates of the Kalman filter 500.
As noted above, the Kalman filter 500 may provide updated
error estimates of each of the measuring sensors which may then
be applied to future estimates from each of the sensors. As will
be recognized by those skilled in the art, the use of the track
database 550 which may precisely locate the vehicle at various
points (such as turnouts, etc.) along its movement in conjunction
with a Kalman filter provides a continuous estimate of vehicle
position which is highly accurate and remains so over the
entirety of the trip by the vehicle. Because the system of the
present invention obtains such positional accuracy without the
use of conventional trackside position indicating equipment, the
system represents a location system which is both highly accurate
and readily maintained by railway managers.
A specific implementation of the velocity filter which may
be used in a system in accordance with the present invention is
illustrated in the simplified block diagram of Figure 7. In this
illustrated filter, the accelerometer 560 is used in conjunction
with the tachometer 520 of the system of Figure 6 to provide
29


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filtering to remove the effects of wheel slip. The output of the
accelerometer 560 is integrated to determine the velocity and the
distance along the track. The change is velocity as determined
from the output of the accelerometer is compared to the change in
velocity as measured by the tachometer 520 for some set interval.
If the change in velocity as determined from the output of the
accelerometer 560 and the change in velocity as determined from
the output of the tachometer 520 agree to within a predetermined
threshold level, it may be assumed that no significant wheel slip
is present and a correction to accelerometer bias and to the
integrated velocity along track is applied based on the current
tachometer velocity.
Depending upon a railway's specific requirements for safety,
freedom from unnecessary warnings, track layout, etc., a PDD in
accordance with the present invention may not need to use a LDS
which provides the location accuracy provided by the LDS
described above. Accordingly, alternative embodiments of an LDS
may readily be used in a PDD system in accordance with the
present invention. With reference now to Figure e, in present
day railway track layouts, the track is marked by wayside markers
(often on posts). which indicate the mileage along the track from
predetermined initial points. Train crew personnel use these
mile markers to orient themselves as to their location and to
identify their location to others during radio communications.
Often, the mileage markers are not precisely placed exactly one
mile apart, often being either more or less than a mile,
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depending upon local conditions. In establishing a track
database which correlates mileage markers to geographic position,
such as may be used in an LDS, recognition should be made of the
facts that the mileage markers are not always exactly one mile
apart and that the system determining the geographic position
(such as a satellite navigation system) will have certain errors
or uncertainties in identifying the location of the train. For
example, a train 910 travelling along a track 915 may compute
that its position is at a point X not on the track. Because the
accuracy of the location determining equipment may not be able to
determine the location of the train sufficiently precisely, it
can be expected that the point X will usually not align perfectly
with the track location as stored in the track database.
To determine the track mileage to display and to transmit to
other trains, the system of the present invention could calculate
the distance to the nearby track mileage points stored in the
track data base and select the mileage point nearest to the
satellite-determined position: Such a method would involve
considerable mathematical processing to calculate the candidate
distances, particularly when the variable distance between lines
of latitude are taken into effect. In another embodiment of the
system of the present invention, such processing is largely
avoided by the use of areas boxes associated with each mileage
point.
With reference now to Figure 9, a track can be represented
by a set of points (for example, a latitude and longitude), one
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set at each of the mileposts of the track. For finer
granularity, the database can store data points for smaller
increments of distance along the track (0.1 miles, for example).
In one embodiment of the present invention, the mileage points
are not stored but rather the system uses a series of boxes, the
size of which are defined around the mileage points based on the
track layout and the expected uncertainty of the measurement of
location. A location measurement which falls within a defined
box is considered to be associated with the mileage point
associated with that box (u.sually mileage point at the center of
the box). If the definitions of the box boundary points are
stored tabularly, the progress of a train from one mileage point
to another mileage point can be determined by a simple comparison
of the measured location to the boundaries, avoiding the
considerable computations needed for a direct comparison of
computed distances from the locations of the mileage points.
Note that in this embodiment of the present invention, that the
boxes defined by the boundaries can have different sizes
depending upon the track layout. For example, the boxes
associated with railyards can be relatively large (as large as
the railyard) because of the PDD's ability to reduce the alarm
sounding and position transmission within such yards.
If the location as measured by whatever measuring system is
being utilized falls outside the boundary boxes stored in the
track database, a signal can be sent to the train personnel
alerting them that they have left the geographic area covered by
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the PDD. Of course, such a signal should not be sent until
sufficient filtering has been done to ensure that the measured
location is~stable and not merely a transient anomaly.
variable size boxes can also be used to account for the
angle of the movement of the vehicle with respect to the grid
used by the location measurement system. For example, and with
reference to Figure 10, if the vehicle is moving at an angle of
approximately 45 degrees to the grid of the boxes, the system of
the present invention may have a tendency to have a reduced
tolerance for uncertainty at locations midway between adjacent
boxes. In this situation, the size of the boundary boxes can be
increased, which increases the overlap between the adjacent boxes
but also provides a system in which uncertainty in the measured
location in a direction perpendicular to the direction of travel
remains at or above a predetermined minimum. For example, and
with continued reference to Figure 10, if a standard box used in
a location determining system is of the size shown by the smaller
boxes 970, the box size can be increased in the appropriate
sections of the route to the size shown by boxes 975.
Note also that the relatively simple location determining
system of this embodiment is not limited to use on trains but may
also be readily used by any vehicle which is supposed to be
running a predetermined route, such as a bus, and alerting
signals when the vehicle leaves the PDD area can be sent not only
to the vehicle operator but also to supervisory or control
personnel.
33

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PCT/US98/03252
While preferred embodiments of the present invention have
been described, it is to be understood that the embodiments
described are illustrative only and the scope of the invention is
to be defined solely by the appended claims when accorded a full
range of equivalence, many variations and modifications naturally
occurring to those of skill in the art from a perusal hereof.
34
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Representative Drawing
A single figure which represents the drawing illustrating the invention.
Administrative Status

For a clearer understanding of the status of the application/patent presented on this page, the site Disclaimer , as well as the definitions for Patent , Administrative Status , Maintenance Fee  and Payment History  should be consulted.

Administrative Status

Title Date
Forecasted Issue Date 2005-04-12
(86) PCT Filing Date 1998-02-20
(87) PCT Publication Date 1998-08-27
(85) National Entry 1999-08-18
Examination Requested 2003-04-14
(45) Issued 2005-04-12
Expired 2018-02-20

Abandonment History

Abandonment Date Reason Reinstatement Date
2002-02-20 FAILURE TO PAY APPLICATION MAINTENANCE FEE 2002-04-16
2003-02-20 FAILURE TO REQUEST EXAMINATION 2003-04-14

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Application Fee $300.00 1999-08-18
Registration of a document - section 124 $100.00 1999-09-23
Maintenance Fee - Application - New Act 2 2000-02-22 $100.00 2000-01-10
Maintenance Fee - Application - New Act 3 2001-02-20 $100.00 2000-11-27
Reinstatement: Failure to Pay Application Maintenance Fees $200.00 2002-04-16
Maintenance Fee - Application - New Act 4 2002-02-20 $100.00 2002-04-16
Maintenance Fee - Application - New Act 5 2003-02-20 $150.00 2003-01-16
Reinstatement - failure to request examination $200.00 2003-04-14
Request for Examination $400.00 2003-04-14
Maintenance Fee - Application - New Act 6 2004-02-20 $150.00 2003-12-29
Maintenance Fee - Application - New Act 7 2005-02-21 $200.00 2005-01-14
Final Fee $300.00 2005-01-25
Maintenance Fee - Patent - New Act 8 2006-02-20 $200.00 2006-02-13
Maintenance Fee - Patent - New Act 9 2007-02-20 $200.00 2007-01-15
Maintenance Fee - Patent - New Act 10 2008-02-20 $250.00 2008-01-15
Maintenance Fee - Patent - New Act 11 2009-02-20 $250.00 2009-01-30
Maintenance Fee - Patent - New Act 12 2010-02-22 $250.00 2010-02-02
Maintenance Fee - Patent - New Act 13 2011-02-21 $250.00 2011-01-31
Maintenance Fee - Patent - New Act 14 2012-02-20 $250.00 2012-01-30
Maintenance Fee - Patent - New Act 15 2013-02-20 $450.00 2013-01-30
Maintenance Fee - Patent - New Act 16 2014-02-20 $450.00 2014-02-17
Maintenance Fee - Patent - New Act 17 2015-02-20 $450.00 2015-02-16
Maintenance Fee - Patent - New Act 18 2016-02-22 $450.00 2016-02-15
Maintenance Fee - Patent - New Act 19 2017-02-20 $450.00 2017-02-13
Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
GE-HARRIS RAILWAY ELECTRONICS, L.L.C.
Past Owners on Record
EASTERLING, SCOTT
GOTFRIED, MICHAEL
GROSS, ERIC
GUARINO, ANTHONY
PEEK, ERNEST L.
REINHART, LEONARD
ZAHM, CHARLES
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
Documents

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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Drawings 2004-07-15 9 189
Description 2004-07-15 34 1,385
Claims 2004-07-15 9 237
Representative Drawing 2004-08-26 1 6
Cover Page 1999-10-21 1 61
Description 1999-08-18 34 1,398
Representative Drawing 1999-10-21 1 12
Abstract 1999-08-18 1 58
Claims 1999-08-18 7 181
Drawings 1999-08-18 9 198
Cover Page 2005-03-16 1 43
Prosecution-Amendment 2004-07-15 22 594
Correspondence 2007-04-17 1 16
Correspondence 1999-09-29 1 2
Assignment 1999-08-18 3 86
PCT 1999-08-18 5 159
Prosecution-Amendment 1999-08-18 1 20
Assignment 1999-09-23 7 288
PCT 1999-11-23 4 178
Prosecution-Amendment 2003-02-21 1 50
Prosecution-Amendment 2003-04-14 2 78
Prosecution-Amendment 2004-03-19 4 119
Correspondence 2005-01-25 1 29
Fees 2006-02-13 1 37
Correspondence 2006-09-13 1 16
Correspondence 2006-10-13 1 18
Correspondence 2006-09-22 2 70
Correspondence 2007-02-12 1 20
Correspondence 2009-02-18 1 20
Correspondence 2007-03-01 2 66
Correspondence 2009-03-27 1 13
Correspondence 2009-02-26 1 27