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Description  |
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BACKGROUND OF THE INVENTION
This invention relates generally to locomotive management, and more
specifically, to tracking locomotives and determining the specific
locomotives in a locomotive consist, which includes determining order and
orientation of the locomotives.
For extended periods of time, e.g., 24 hours or more, locomotives of a
locomotive fleet of a railroad are not necessarily accounted for due, for
example, to the many different locations in which the locomotives may be
located and the availability of tracking device at those locations. In
addition, some railroads rely on wayside automatic equipment
identification (AEI) devices to provide position and orientation of a
locomotive fleet. AEI devices typically are located around major yards and
provide minimal position data. AEI devices are expensive and the
maintenance costs associated with the existing devices is high. There
exists a need for cost-effective tracking of locomotives.
BRIEF SUMMARY OF THE INVENTION
In one aspect, the present invention relates to identifying locomotive
consists within train consists, and determining the order and orientation
of the locomotives within the identified locomotive consists. By
identifying locomotive consists and the order and orientation of
locomotives within such consists, a railroad can better manage it
locomotive fleet.
In one exemplary embodiment, an on-board tracking system for being mounted
to each locomotive of a train includes locomotive interfaces for
interfacing with other systems of the particular locomotive, a computer
coupled to receive inputs from the interface, and a GPS receiver and a
satellite communicator (transceiver) coupled to the computer. A radome is
mounted on the roof of the locomotive and houses the satellite
transmit/receive antennas coupled to the satellite communicator and an
active GPS antenna coupled to the GPS receiver.
Generally, the onboard tracking system determines the absolute position of
the locomotive on which it is mounted and additionally, obtains
information regarding specific locomotive interfaces that relate to the
operational state of the locomotive. Each equipped locomotive operating in
the field determines its absolute position and obtains other information
independently of other equipped locomotives. Position is represented as a
geodetic position, i.e., latitude and longitude.
The locomotive interface data is typically referred to as "locomotive
discretes" and are key pieces of information utilized during the
determination of locomotive consists. In an exemplary embodiment, three
(3) locomotive discretes are collected from each locomotive. These
discretes are reverser handle position, trainlines eight (8) and nine (9),
and online/isolate switch position. Reverser handle position is reported
as "centered" or "forward/reverse". A locomotive reporting a centered
reverser handle is in "neutral" and is either idle or in a locomotive
consist as a trailing unit. A locomotive that reports a forward/reverse
position is "in-gear" and most likely either a lead locomotive in a
locomotive consist or a locomotive consist of one locomotive. Trainlines
eight (8) and nine (9) reflect the direction of travel with respect to
short-hood forward versus long-hood forward for locomotives that have
their reverser handle in a forward or reverse position.
The online/isolate switch discrete indicates the consist "mode" of a
locomotive during railroad operations. The online switch position is
selected for lead locomotives and trailing locomotives that will be
controlled by the lead locomotive. Trailing locomotives that will not be
contributing power to the locomotive consist will have their
online/isolate switch set to the isolate position.
The locomotives provide location and discrete information from the field,
and a data center receives the raw locomotive data. The data center
processes the locomotive data and determines locomotive consists.
Specifically, and in one embodiment, the determination of locomotive
consist is a three (3) step process in which 1) the locomotives in the
consist are identified, 2) the order of the locomotives with respect to
the lead locomotive are identified, and 3) the orientation of the
locomotives in the consist are determined as to short-hood versus long
hood forward.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of an on-board tracking system.
FIG. 2 illustrates a train consist including a system in accordance with
one embodiment of the present invention.
FIG. 3 illustrates a train consist including a system in accordance with
another embodiment of the present invention.
FIG. 4 illustrates a sample and send method.
FIG. 5 illustrates apparent positions of six candidate locomotives for a
locomotive consist.
FIG. 6 illustrates an angle defined by three points.
FIG. 7 illustrates using angular measure to determine locomotive order.
FIG. 8 illustrates coordinates of points forming an angle.
FIG. 9 illustrates location of a centroid between two locomotives.
DETAILED DESCRIPTION OF THE INVENTION
As used herein, the term "locomotive consist" means one or more locomotives
physically connected together, with one locomotive designated as a lead
locomotive and the others as trailing locomotives. A "train" consist means
a combination of cars (freight, passenger, bulk) and at least one
locomotive consist. Typically, a train is built in a terminal/yard and the
locomotive consist is at the head end of the train. Occasionally, trains
require additional locomotive consists within the train consist or
attached to the last car in the train consist. Additional locomotive
consists sometimes are required to improve train handling and/or to
improve train performance due to the terrain (mountains, track curvature)
in which the train will be travelling. A locomotive consist at a head-end
of a train may or may not control locomotive consists within the train.
A locomotive consist is further defined by the order of the locomotives in
the locomotive consist, i.e. lead locomotive, first trailing locomotive,
second trailing locomotive, and the orientation of the locomotives with
respect to short-hood forward versus long-hood forward. Short-hood forward
refers to the orientation of the locomotive cab and the direction of
travel. Most North American railroads typically require the lead
locomotive to be oriented short-hood forward for safety reasons, as
forward visibility of the locomotive operating crew is improved.
FIG. 1 is a block diagram of an on-board tracking system 10 for each
locomotive and/or car of a train consist. Although the on-board system is
sometimes described herein in the context of a locomotive, it should be
understood that the tracking system can be used in connection with cars as
well as any other train consist member. More specifically, the present
invention may be utilized in the management of locomotives, rail cars, any
maintenance of way (vehicle), as well as other types of transportation
vehicles, e.g., trucks, trailers, baggage cars. Also, and as explained
below, each locomotive and car of a particular train consist may not
necessarily have such on-board tracking system.
As shown in FIG. 1, system 10 includes locomotive interfaces 12 for
interfacing with other systems of the particular locomotive on which
on-board system 10 is mounted, and a computer 14 coupled to receive inputs
from interface 12. System 10 also includes a GPS receiver 16 and a
satellite communicator (transceiver) 18 coupled to computer 14. Of course,
system 10 also includes a power supply for supplying power to components
of system 10. A radome (not shown) is mounted on the roof of the
locomotive and houses the satellite transmit/receive antennas coupled to
satellite communicator 18 and an active GPS antenna coupled to GPS
receiver 16.
FIG. 2 illustrates a locomotive consist LC which forms part of a train
consist TC including multiple cars C1-CN. Each locomotive L1-L3 and car C1
includes a GPS receiver antenna 50 for receiving GPS positioning data from
GPS satellites 52. Each locomotive L1-L3 and car C1 also includes a
satellite transceiver 54 for exchanging, transmitting and receiving data
messages with central station 60.
Generally, each onboard tracking system 10 determines the absolute position
of the locomotive on which it is mounted and additionally, obtains
information regarding specific locomotive interfaces that relate to the
operational state of the locomotive. Each equipped locomotive operating in
the field determines its absolute position and obtains other information
independently of other equipped locomotives. Position is represented as a
geodetic position, i.e., latitude and longitude.
The locomotive interface data is typically referred to as "locomotive
discretes" and are key pieces of information utilized during the
determination of locomotive consists. In an exemplary embodiment, three
(3) locomotive discretes are collected from each locomotive. These
discretes are reverser handle position, trainlines eight (8) and nine (9),
and online/isolate switch position. Reverser handle position is reported
as "centered" or "forward/reverse". A locomotive reporting a centered
reverser handle is in "neutral" and is either idle or in a locomotive
consist as a trailing unit. A locomotive that reports a forward/reverse
position refers to a locomotive that is "in-gear" and most likely either a
lead locomotive in a locomotive consist or a locomotive consist of one
locomotive. Trainlines eight (8) and nine (9) reflect the direction of
travel with respect to short-hood forward versus long-hood forward for
locomotives that have their reverser handle in a forward or reverse
position.
Trailing locomotives in a locomotive consist report the appropriate
trainline information as propagated from the lead locomotive. There fore ,
trailing locomotives in a locomotive consist report trainline information
while moving and report no trainline information while idle (not moving).
The online/isolate switch discrete indicates the consist "mode" of a
locomotive during railroad operations. The online switch position is
selected for lead locomotives and trailing locomotives that will be
controlled by the lead locomotive. Trailing locomotives that will not be
contributing power to the locomotive consist will have their
online/isolate switch set to the isolate position.
As locomotives provide location and discrete information from the field, a
central data processing center, e.g., central station 60, receives the raw
locomotive data. Data center 60 processes the locomotive data and
determines locomotive consists as described below.
Generally, each tracking system 10 polls at least one GPS satellite 52 at a
Specified send and sample time. In one embodiment, a pre-defined satellite
52 is designated in memory of system 10 to determine absolute position. A
data mes sage containing the p position and discrete data is then
transmitted to central station 60 via satellite 56, i.e., a data
satellite, utilizing transceiver 54. Typically, data satellite 56 is a
different satellite than GPS satellite 52. Additionally, data is
transmitted from central station 60 to each locomotive tracking system 10
via data satellite 56. Central station 60 includes at least one antenna
58, at least one processor.(not shown), and at least one satellite
transceiver (not shown) for exchanging data messages with tracking systems
10.
More specifically, and i n one embodiment, the determination of locomotive
consist is a three (3) step process in which 1) the locomotives in the
consist are identified, 2) the order of the locomotives with respect to
the lead locomotive are identified, and 3) the orientation n of the
locomotives in the consist are determined as to short-hood versus long
hood forward. In order to identify locomotives in a locomotive consist,
accurate position data for each locomotive in the locomotive consist is
necessary. Due to errors introduced into the solution provided by GPS,
typical accuracy is around 100 meters. Randomly collecting location data
therefore will not provide the required location accuracy necessary to
determine a locomotive consist.
In one embodiment, the accuracy of the position data relative to a group of
locomotives is improved by sampling (collecting) the position data from
each GPS receiver of each locomotive in the consist simultaneously--at the
same time. The simultaneous sampling of location data is kept in
synchronization with the use of on board clocks and the GPS clock. The
simultaneous sampling between multiple assets is not exclusive to GPS, and
can be utilized in connection with other locations devices to such as
Loran or Qualcomm's location device (satellite triangulation).
The simultaneous sampling of asset positions allows for the reduction of
atmospheric noise and reduction in the U.S. government injected selective
availability error (noise/injection cancellation). The reduction in error
is great enough to be assured assets can be uniquely identified. This
methodology allows for consist order determination while the consist is
moving and differs greatly from a time averaging approach which requires
the asset to have been stationary, typically for many hours, to improve
GPS accuracy.
More specifically, civil users worldwide use the SPS without charge or
restrictions. The SPS accuracy is intentionally degraded by the U.S.
Department of Defense by the use of selective availability (SA). As a
result, the SPS predictable accuracy is as follows.
100 meter horizontal accuracy, and
156 meter vertical accuracy.
Noise errors are the combined effect of PRN code noise (around 1 meter) and
noise within the receiver (around 1 meter). Bias errors result from
selective availability and other factors. Again, selective availability
(SA) is a deliberate error introduced to degrade system performance for
non-U.S. military and government users. The system clocks and ephemeris
data is degraded, adding uncertainty to the pseudo-range estimates. Since
the SA bias, specific for each satellite, has low frequency terms in
excess of a few hours, averaging pseudo-range estimates over short periods
of time is not effective. The potential accuracy of 30 meters for C/A code
receivers is reduced to 100 meters.
As a result of the locomotives being very close geographically and sampling
the satellites at exactly the same time, a majority of the errors are
identical and are cancelled out. resulting in an accuracy of approximately
25 feet. This improved accuracy does not require additional processing nor
more expensive receivers or correction schemes.
Each locomotive transmits a status message containing a location report
that is time indexed to a specific sample and send time based on the known
geographic point from which the locomotive originated. A locomotive
originates from a location after a period in which it has not physically
moved (idle). Locomotive consists are typically established in a
yard/terminal after an extended idle state. Although not necessary, in
order to obtain a most accurate location, a locomotive should be moving or
qualified over a distance, i.e., multiple samples when moving over some
minimum distance. Again, however, it is not necessary that the locomotive
be moving or qualified over a distance.
Each tracking system 10 maintains a list of points known as a locomotive
assignment point (LAP) which correlates to the yards/terminals in which
trains are built. As a locomotive consist assigned to a train departs a
locomotive assignment point (LAP), onboard system 10 determines the
departure condition and sends a locomotive position message back to the
data center. This message contains at a minimum, latitude, longitude and
locomotive discretes.
The data for each locomotive is sampled at a same time based on a table
maintained by each locomotive and the data center, which contains LAP ID,
GPS sample time, and message transmission time. Therefore, the data center
receives a locomotive consist message for each locomotive departing the
LAP, which in most instances provides the first level of filtering for
potential consist candidates. The distance at which the locomotives
determine LAP departure is a configurable item maintained on-board each
tracking system.
FIG. 3 illustrates train consist TC including an on-board system in
accordance with another embodiment of the present invention. Each
locomotive L1-L3 and car C1 includes a GPS receiver antenna 50 for
receiving GPS positioning data from GPS satellites 52. Each locomotive
L1-L3 and car C1 also includes a radio transceiver 62 for exchanging,
transmitting and receiving data messages with central station 60 via
antennas 64 and 66. The on-board systems utilized in the FIG. 3
configuration are identical to on-board system 10 illustrated in FIG. 1
except that rather than a satellite communication 18, the system
illustrated in FIG. 3 includes a radio communicator.
Generally, and as with system 10, each tracking system 10 polls at least
one GPS satellite 52 at a specified send and sample time. In one
embodiment, a pre-defined satellite 52 is designated in memory to
determine absolute position. A data message containing the position and
discrete data is then transmitted to central station 60 via antenna 64
utilizing transceiver 62. Additionally, data is transmitted from central
station 60 to each locomotive tracking system via antenna 64. Central
station 60 includes at least one antenna 66, at least one processor (not
shown), and at least one satellite transceiver (not shown) for exchanging
data messages with the tracking systems.
In another embodiment, each on-board system includes both a satellite
communicator (FIG. 1) and a radio communicator (FIG. 3). The radio
communicators are utilized so that each on-board system can exchange data
with other on-board systems of the train consist. For example, rather than
each locomotive separately communicating its data with central station 60
via the data satellite, the data can be accumulated by one of the on-board
systems via radio communications with the other on-board systems. One
transmission of all the data to the central station from a particular
train consist can then be made from the on-board system that accumulates
all the data. This arrangement provides the advantage of reducing the
number of transmissions and therefore, reducing the operational cost of
the system.
Data center 60 may also include, in yet another embodiment, a web server
for enabling access to data at center 60 via the Internet. Of course, the
Internet is just one example of a wide area network that could be used,
and other wide area network as well as local area network configurations
could be utilized. The type of data that a railroad may desire to post at
a secure site accessible via the Internet includes, by way of example,
locomotive identification, locomotive class (size of locomotive), tracking
system number, idle time, location (city and state), fuel, milepost, and
time and date transmitted. In addition, the data may be used to
geographically display location of a locomotive on a map. Providing such
data on a secure site accessible via the Internet enables railroad
personnel to access such data at locations remote from data center 60 and
without having to rely on access to specific personnel.
FIG. 4 illustrates the above described sample and send method. For example,
at LAP-22, three locomotives are idle and at some point, are applied to a
train ready for departure. As the train departs the yard, each on-board
system for each locomotive determines that it is no longer idle and that
it is departing the LAP-22 point. Once LAP departure has been established,
the on-board tracking system changes its current sample and send time to
the sample and send time associated with LAP-22 as maintained onboard all
tracking equipped locomotives. Based on the information in the example,
the three (3) locomotives would begin sampling and sending data at ten
(10) minutes after each hour.
The locomotives run-thru LAP 44 (no idle). The three locomotives therefore
continue through LAP-44 on the run-thru tracks without stopping the train.
The on-board systems determine entry and exit of the proximity point, but
the sample and send time would remain associated with the originating LAP
point (22).
The three (3) locomotives then enter LAP-66 and a proximity event would be
identified. The train is scheduled to perform work in the yard which is
anticipated to require nine (9) hours. During this time, the three (3)
locomotives remain attached to the consist while the work is performed.
After completing the assigned work, the train departs the yard (LAP-66)
destined for the terminating yard (LAP-88). At this point, each on-board
system determines it is no longer idle and switches its sample and send
time to that specified in their table for LAP-66, i.e., at 2 minutes after
each hour. At this point, the three (3) locomotives have departed LAP-66
and their sample and send time is now two (2) minutes after each hour.
At some point, the three (3) locomotives enter LAP-88 (proximity alert) and
become idle for an extended period. The locomotives continue to sample and
send signals based on their last origin location, which was LAP-66.
As locomotive position reports are received by the data center, the sample
time associated with the reports is utilized to sort the locomotives based
on geographic proximity. All locomotives that have departed specific
locations will sample and send their position reports based on a lookup
table maintained onboard each locomotive. The data center sorts the
locomotive reports and determines localized groups of locomotives based on
sample and send time.
A first step in the determination of a locomotive consist requires
identification of candidate consists and lead locomotives. A lead
locomotive is identified by the reverser handle discrete indicating the
handle is in either the forward or reverse position. Also, the lead
locomotive reports its orientation as short-hood forward as indicated by
trainline discretes. Otherwise, the locomotive consist determination
terminates pursuing a particular candidate locomotive consist due to the
improper orientation of the lead locomotive. If a lead locomotive is
identified (reverser and orientation) and all of the other locomotives in
the candidate consist reported their reverser handle in the centered
(neutral) position indicating trailing locomotives, the next step in the
consist determination process is executed.
At this point, candidate locomotive consists have been identified based on
their sample and send time and all lead locomotives have been identified
based on reverser handle discretes. The next step is to associate trailing
locomotives with a single lead locomotive based on geographic proximity.
This is accomplished by constructing and computing the centroid of a line
between each reporting locomotive and each lead locomotive. The resulting
data is then filtered and those trailing locomotives with centroids that
fall within a specified distance of a lead locomotive are associated with
the lead as a consist member. This process continues until each reporting
locomotive is either associated with a lead locomotive or is reprocessed
at the next reporting cycle.
Then, the order of the locomotives in the locomotive consist is determined.
The lead locomotive was previously identified, which leaves the
identification of the trailing units. It should be noted that not all
locomotives are equipped with on-board tracking systems and therefore,
"ghost" locomotives, i.e., locomotives that are not equipped with tracking
systems will not be identified at this point in time. It should also be
noted that in order to identify ghost locomotives, the ghost locomotives
must be positioned between tracking equipped locomotives.
FIG. 5 depicts six points in a plane which are defined by returned
positional data from six locomotives in a power consist of a train. The
points P.sub.1, . . . ,P.sub.6 represent the respective location of each
locomotive, and since GPS positional data is not perfect, the reference
line shown is taken to be the line best fitting the points (approximating
the actual position of the track).
With the notation denoting the unsigned magnitude of an angle defined on
points X, Y, and Z, with Y as the vertex, as shown in FIG. 6, the angles
defined by the positions of locomotives are used in order to establish
their order in the locomotive consist.
Referring to FIG. 7, data collection of locomotive discretes onboard the
locomotive allows the determination of the position of the lead locomotive
by information other than its position in the consist. Therefore, it is
known that all other locomotives are behind the lead locomotive. Since the
lead locomotive is identified, it is assigned the point P.sub.1. For the
remaining points, there is no specific knowledge of their order in the
power consist, other than that they follow P.sub.1. The following
relationships exist.
.angle.P.sub.i P.sub.j P.sub.1.apprxeq.180.degree..fwdarw.P.sub.i follows
P.sub.j,
and
.angle.P.sub.i P.sub.j P.sub.1.apprxeq.0.degree..fwdarw.P.sub.i follows
P.sub.j.
By forming a matrix with all rows and columns indexed by the locomotives
known to be in the consist, and initially setting all entries of the
matrix to zero, then a 1 is placed in any cell such that the row entry
(locomotive) of the cell occurs earlier in the consist than the column
entry, as determined by the angular. criterion given above. Since the lead
locomotive is already known, a 1 is placed in each cell of row 1 of the
matrix, except the cell corresponding to (1,1). This leads to (N-1)(N-2)/2
comparisons, where N locomotives are in the consist, since pair (P.sub.i,
P.sub.j) i.noteq.j must be tested only once, and P.sub.1 need not be
included in the testing.
The matrix is shown below.
##EQU1##
The order of the locomotives in the consist corresponds to the number of
ones in each row. That is, the row with the most ones is the lead
locomotive, and the locomotives then occur in the consist as follows:
P.sub.1 --five 1's, lead locomotive,
P.sub.6 --four 1's, next in consist,
P.sub.3 --three 1's next in consist,
P.sub.5 --two 1's next in consist,
P.sub.2 --one 1 next in consist,
P.sub.4 --zero 1's last in consist.
The above described method does not require that all locomotives be in a
single group in the train. If a train is on curved track, the angles would
vary more from 0.degree. and 180.degree. than would be the case on
straight track. However, it is extremely unlikely that a train would ever
be on a track of such extreme curvature that the angular test would fail.
Another possible source of error is the error implicit in GPS positional
data. However, all of the locomotives report GPS position as measured at
the same times, and within a very small distance of each other. Thus, the
errors in position are not be expected to influence the accuracy of the
angular test by more than a few degrees, which would not lead to confusion
between 0.degree. and 180.degree..
The determination of angle as described above need not actually be
completely carried out. In particular, the dot product of two vectors
permits quick determination of whether the angle between them in closer to
0.degree. or 180.degree.. FIG. 8 illustrates three points defining an
angle, with coordinates determined as though the points were in Cartesian
plane. Given these points and the angle indicated, the dot product may be
expressed by the simple computation:
S=(A.sub.x -B.sub.x)(C.sub.x -B.sub.x)+(A.sub.y -B.sub.y)(C.sub.y
B.sub.y).
The geometric interpretation of the dot product is given by:
S=.parallel.AB.parallel..multidot..parallel.BC.parallel..multidot.
cos(.angle./ABC),
where the notation .parallel.XY.parallel. denotes the length of a line
segment between points X and Y. The lengths of line segments are always
positive, so that the sign of s is determined soley by the factor
cos(.angle.ABC), and that factor is positive for all angles within
90.degree. of 0.degree., and is negative for all angles within 90.degree.
of 180.degree.. Therefore, a test for the relative order of two
locomotives can be executed by using the absolute positions of the
locomotives and computing dot products for the angles shown in FIG. 6. The
sign of the dot product then suffices to specify locomotive order.
Locomotive positions have been interpreted as Cartesian coordinates in a
plane, while GPS positions are given in latitude, longitude, and altitude.
Using the fact that a minute of arc on a longitudinal circle is
approximately 1 nautical mile, and that a minute of arc on a latitudinal
circle is approximately 1 nautical mile multiplied by the cosine of the
latitude, one obtains an easy conversion of the (latitude, longitude) pair
to a Cartesian system. Given a latitude and longitude of a point,
expressed as(.theta.,.phi.), conversion to Cartesian coordinates is given
by:
x=60.multidot..theta..multidot.cos(.theta.), y=60.multidot..phi.
This ignores the slight variations | | |
