Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
METHODS AND SYSTEMS FOR END OF TRAIN FORCE REPORTING
Field
[001] The invention relates generally to railroad end of train telemetry, and
more
particularly to the reporting of end of train forces.
BACKGROUND
[002] Within the railroad industry, end of train (EOT) units (sometimes also
referred to as
end of train devices) are typically attached at the rear of the last car on a
train, often to the
unused coupling on the end of the last car opposite the head of the train.
These EOT
devices were originally designed to perform some of the functions previously
performed
by train personnel located in the caboose, thereby allowing trains to operate
without a
caboose and with a reduced number of human operators.
[003] Modem EOT units can perform a number of functions, some required by FRA
(Federal Railroad Administration) regulations and some not. EOT units monitor
air
pressure in the air brake pipe and transmit this information to a head of the
train (HOT)
device located near the front of the train. EOT units also often include an
end-of-train
marker light to alert trailing trains on the same track of the presence of the
end of the train.
Two-way EOT units (now required by FRA regulation in the U.S.) can accept a
command
from the HOT to open a valve to release pressure in the air brake pipe so that
the train's air
brakes activate to stop the train in an emergency situation. Some EOT units
include GPS
receivers that are used to transmit location information pertaining to the end
of the train to
HOT equipment as discussed in U.S. Patent No. 6,081,769. EOT units typically
communicate with the HOT using radio-based communications. This is because
there is
no hard-wired electrical connection between the head of the train and the end
of the train
on some trains, especially freight trains.
[004] Some EOT units include motion detectors that are used to inform the HOT
as to
whether, and in some cases in which direction, a train is moving. In some EOT
units, an
accelerometer is used as the motion detector. Motion detection is reported by
only a single
bit (i.e., the single bit indicates only motion or lack thereof without any
indication of speed
or direction) under AAR Standard S-5701 for "End-of-Train Communications." The
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indication of train movement or lack thereof from the motion detector,
together with an
indication of the head of train movement, may be used by train personnel
and/or computerized
on-board train control systems to determine whether or not a train separation
has occurred.
However, such a determination is not very reliable given the single bit used
to report motion
pursuant to AAR Standard S-5701 because movement in opposite directions, and
movement
at significantly different speeds in the same direction, cannot be determined.
[005] A somewhat more capable device is described in U.S. Patent No.
6,087,950, which
describes a motion detector that can be attached to an end of train unit. The
motion detector
includes a single axis accelerometer. The motion detector is configured to
report a motion
state that can be moving or non-moving and a motion direction that can be
forward or reverse.
[006] More recently, EOT units that can communicate their positions to devices
located off of
the train, such as those described in U.S. Patent No. 7,096,096 and in U.S.
Pat. Pub.
No. 2007/0170314, have become known in the art. These communications allow
personnel
responsible for such EOT units to locate them. Such communications can occur
both when
the EOT units are mounted on a train and when they are not mounted on any
train.
SUMMARY
[006a] According to one aspect of the present invention, there is provided an
end of train unit
suitable for use on a train, the end of train unit comprising: a processor
connected to a
housing; a first coupling connected to the housing, the first coupling being
configured to
engage a train coupling; an end of train marker light connected to the housing
and configured
to be controlled by the processor; a pressure transducer connected to the
processor and in fluid
communication with a second coupling connectable to an air brake pipe of a
train; an
accelerometer connected to the processor; and a first transmitter connected to
the processor;
wherein the processor is configured to perform the steps of receiving an
acceleration from the
accelerometer; performing a comparison of the acceleration to a threshold;
determining that
the acceleration exceeds the threshold; and transmitting a message via the
first transmitter in
response to the acceleration exceeding the threshold, wherein the message
includes a
magnitude of the acceleration.
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[00613] According to another aspect of the present invention, there is
provided a system for
end of train force reporting, comprising: an end of train unit comprising: an
end of train unit
processor connected to a housing; a first coupling connected to the housing,
the first coupling
being configured to engage a train coupling; an end of train marker light
connected to the
housing and configured to be controlled by the end of train unit processor; a
pressure
transducer connected to the end of train unit processor and in fluid
communication with a
second coupling connectable to an air brake pipe of a train; an accelerometer
connected to the
end of train unit processor; and a first transmitter connected to the end of
train unit processor;
a head of train unit comprising: a head of train unit processor; a wireless
receiver connected to
the head of train unit processor; and a display connected to the head of train
unit processor;
the system performing the steps of: detecting, by the accelerometer, an
acceleration of the end
of train unit, performing, by the end of train unit processor, a comparison of
the detected
acceleration to a first threshold, transmitting, by the first transmitter to
the wireless receiver, a
message indicating that an excessive end of train acceleration has been
detected and the
magnitude of the acceleration, when the detected acceleration exceeds the
first threshold,
receiving, by the wireless receiver, the message transmitted by the first
transmitter,
performing, by the head of train unit processor, a comparison of the magnitude
of the
acceleration to a second threshold, and taking a corrective action if the
magnitude of the
acceleration exceeds the second threshold.
BRIEF DESCRIPTION OF THE DRAWINGS
10071 A more complete appreciation of the invention and many of the attendant
features and
advantages thereof will be readily obtained as the same become better
understood by
reference to the following detailed description when considered in connection
with the
accompanying drawings, wherein:
[008] Fig. 1 is a system for reporting excessive EOT force according to one
embodiment of
the invention.
[009] Figs. 2a and 2b are perspective and front views, respectively, of an EOT
unit according
to one embodiment of the invention.
2a
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100101 Fig. 3 is a block diagram of the EOT unit of Figs. 2a and 2b.
100111 Fig. 4 is a flow chart illustrating a location reporting subroutine
performed by the end
of train unit of Fig. 3.
2b
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[0012] Fig. 5 is a front view of a head of train device according to one
embodiment of the
invention.
[0013] Fig. 6 is a block diagram of the head of train device of Fig. 5.
[0014] Fig. 7 is a flow chart illustrating processing performed by the head of
train device
of Fig. 5.
DETAILED DESCRIPTION
[0015] The present invention will be discussed with reference to preferred
embodiments
of end of train units. Specific details, such as message formats and various
reporting
methods, are set forth in order to provide a thorough understanding of the
present
invention. The preferred embodiments discussed herein should not be understood
to limit
the invention. Furthermore, for ease of understanding, certain method steps
are delineated
as separate steps; however, these steps should not be construed as necessarily
distinct nor
order dependent in their performance.
[0016] Excessive forces exerted on trains can damage both equipment (train and
track)
and cargo being carried on the train. Excessive forces applied to a train
tends to become
magnified at the end of the train. Such excessive forces can result from
various causes.
An operator can cause excessive forces at the end of the train by accelerating
too rapidly,
which will cause a car at the end of the train to jerk in the direction of
track once the slack
between cars is taken up as the locomotive(s) at the head of the train
accelerate. An
inexperienced operator, or even an experienced operator who is operating a
very long
train, may not realize the forces being exerted on an end of the train due to
his/her actions.
Another potential cause of excessive forces at the end of the train can result
from
excessively "wavy" tracks that cause cars to sway rapidly from side to side as
the cars
travel along the tracks. These forces occur mainly along an axis perpendicular
to the
track. Still another potential cause of excessive forces at an end of a train
are poor track
joints, which may occur at grade crossings, bridges, or the like but which may
also occur
anywhere along a track. These forces tend to occur primarily along an axis
that is
vertically oriented with respect to the track. Excessive forces at the end of
the train can
also be caused in other ways.
[0017] Because of the different possible causes for excessive forces at the
end of the train,
different actions are performed in different embodiments discussed herein. The
first step
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is to detect the occurrence of an excessive force. This step may be performed
using an
accelerometer located in an end of train unit (it being understood that an
accelerometer
measures acceleration, which is proportional to force). In preferred
embodiments, the
accelerometer is a tri-axial accelerometer with the axes oriented such that a
first axis is
along a direction of the track, a second axis is along a direction
perpendicular to the track
and a third axis is along a direction vertical to the track. This arrangement
is advantageous
in that it provides the ability to determine a direction along with an
acceleration has
occurred, which may be indicative of the cause of the acceleration (e.g., a
sudden vertical
acceleration may result from a problem with the track whereas a sudden
acceleration in a
direction of a track may result from an operator accelerating a train from a
stopped
position too rapidly). In other embodiments, a single or dual axis
accelerometer is used.
Such embodiments may employ one or more accelerometers along one of the three
axes
discussed above, or may orient the accelerometer such that it is sensitive to
accelerations
in more than one axis as discussed in U.S. Patent No. 6,087,950. Embodiments
utilizing a
single accelerometer can be less expensive than embodiments employing multiple
accelerometers or multiple axis accelerometers.
[0018] The accelerometer(s) may be periodically polled in real time to detect
forces
greater than a threshold. Alternatively, a triggering circuit such as a one-
shot may be used
to generate an interrupt when the accelerometer measures a force greater than
the
threshold. The accelerations reported by the accelerometers are typically
"instantaneous"
accelerations, and these instantaneous accelerations are used directly in some
embodiments. In other embodiments, a plurality of instantaneous accelerations
are filtered
(e.g., moving window average filtering, Kalman filtering, etc.).
[0019] Various embodiments employ different thresholds. In some embodiments,
the
threshold may be fixed. In such embodiments, the threshold may be set to an
acceleration
based on a safety factor and maximum force for which a typical car coupling
can
withstand divided by a maximum car weight. A typical freight car coupling in
use in the
U.S. can withstand a force of about 350,000 pounds, and a current maximum
expected car
weight in the U.S. freight railroad industry is 268,000 pounds (this
represents the weight
of the car plus a maximum cargo). In some embodiments, the acceleration
threshold based
on these values and a safety factor is chosen as 1g. The threshold is
preferably 0.25g or
greater to ensure that accelerations associated with normal movement of the
train are not
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reported as excessive. In yet other embodiments, the threshold is set
dynamically. The
threshold may be set dynamically based on a particular cargo being carried on
the train,
particular equipment (e.g., couplings, types of cars) used on the train, or
any other factor
which may affect a desirable maximum EOT force.
[0020] Once an excessive force has been detected, the detection must be
communicated.
The communication may occur immediately or soon after the detection has been
made,
and/or the detection may be recorded and communicated later. In some
embodiments, the
occurrence of the excessive force is communicated to a head of train device
for display to
an operator immediately or soon after the detection occurs (such display being
different
from the manner in which an indication of movement of the train is normally
displayed to
the operator). The message and/or display may include a simple indication that
an
acceleration greater than the threshold has been observed, or may include the
actual
(preferably instantaneous) acceleration (or accelerations in multiple axis
accelerometer
embodiments) measured by the accelerometer. In such embodiments, the head of
train
device relays the message to a central office, either in addition to or
instead of displaying
the message. In other embodiments, the EOT device may transmit the message
directly to
a central data collection site. For example, EOTs equipped for long range
communication
with a central site (e.g., via a cellular modem that communicates with a
cellular base
station) are disclosed in U.S. Pat. Pub. No. 2007/0170314. As disclosed in
that
publication, the EOT may periodically transmit a message including the EOT
location.
[0021] In some embodiments, the message further includes information (e.g., an
amount
of excessive force or an indication that an excessive force has been detected
together with
a location and/or time at which the excessive force was detected). In yet
other
embodiments, the EOT device includes an event recorder which records
information
pertaining to the excessive force. The data from the EOT device is accessed
later and
appropriate action (e.g., informing the operator of the excessive force if the
operator was
the cause, repairing the section of track causing the excessive force) is
taken. In still other
embodiments, an excessive force detection message sent from the EOT to the HOT
is
recorded in an event recorder included in the HOT device and/or forwarded from
the HOT
device to the train's main event recorder. Still other methods for
communicating the
detection of an excessive force are possible.
[0022] An exemplary embodiment of an EOT force reporting system will now be
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discussed. This embodiment will include multiple EOT force reporting methods
as
discussed above. It should be understood that other embodiments employ less
than all of,
or alternatives to, the reporting methods discussed in connection with this
embodiment.
[0023] Fig. 1 is a block diagram of a system 10 for measuring and reporting
EOT forces.
The system includes an EOT unit 100 configured for wireless communications
with an
HOT device 300. The HOT device 300 is connected to an event recorder 301. The
EOT
unit 100, the HOT device 300 and the event recorder 301 are all located
onboard a train.
The HOT device 300 is configured for wireless communications with a central
office 303.
The EOT unit 100 is also configured for wireless communications with and EOT
Tracking
Facility 302.
[0024] Figs. 2a and 2b illustrate an embodiment of the EOT unit 100. The EOT
unit 100
includes a housing 110 in which the internal components of the EOT unit 100
(discussed
in further detail below) are located. A handle 111 is attached to the housing
110 to
facilitate the installation and removal of the EOT unit 100 from a train car.
Also attached
to the housing is a connector 120 for connecting the EOT unit 100 to an air
brake hose 10
which is in fluid communication with the train's air brake pipe (not shown in
Figs. 2a or
2b). Also attached to the housing 110 is a coupler 130 which couples the EOT
unit 100 to
a train car coupling. The EOT unit 100 also includes a marker light 140
attached to the
housing 110. Three antennas are also attached to the housing 110: a first
antenna 150 for
communicating with the HOT, a second antenna 160 for communicating with a
cellular
base station network, and a third antenna 170 for receiving messages from GPS
satellites.
[0025] A block diagram 30 of the EOT unit 100 of Fig. 1 is illustrated in Fig.
3. The EOT
unit 100 is controlled by a processor 210. The processor 210 receives power
from a power
subsystem 220 which includes an air-powered electrical generator 221 connected
to the air
brake pipe 10, a rectifier 222, a voltage regulator 223 and one or more
batteries 224.
Details concerning the power subsystem 220 are discussed in greater detail in
corresponding U.S. Patent No. 7,096,096.
[0026] The processor 210 is connected to control an EOT marker light 140
(although a
direct connection is illustrated in Fig. 2, those of skill in the art will
understand that the
processor 210 may supply the control of power to the EOT marker light 140 via
a relay or
similar device) in accordance with applicable FRA regulations. Also connected
to the
processor 210 is a tilt sensor 230. The processor 210 uses the tilt sensor
230, among other
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things, to determine when the EOT unit 100 has been placed in a horizontal
position so
that the processor 210 can take the EOT unit to a low power state to conserve
battery
power.
[0027] Also connected to the processor 210 is an air pressure transducer 240,
which is in
fluid communication with the air brake pipe 10 and is configured to detect the
pressure in
the air brake pipe 10. The processor 210 reads the pressure in the air brake
pipe 10
reported by the transducer 240 and periodically transmits this and other
information to the
HOT using the HOT transceiver 250. Under AAR Standard S-5701, the report
occurs
once every 55-65 seconds in the absence of significant pressure changes. The
format of an
exemplary report is set forth below:
[ 0028] Table 1. FRA Message Guidelines - Standard S-5701
Basic Bit sync 69 bits
Block
Frame sync 11 bits
Chaining bits 2 bits
Device battery condition 2 bits
Message type identifier 3 bits
Unit address code 17 bits
Rear brake pipe status and pressure 7 bits
Discretionary information 11 bits*
Motion detection 1 bit
Marker light battery condition 1 bit
Marker light status 1 bit
Basic block BCH code 18 bits
Trailing bit 1 bit
Total Length 144 bits
* For two-way systems, see paragraph 3Ø
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Optional Bit sync 69 bits
Block(s)
Frame sync 11 bits
Chaining bits 2 bits
Block format indicator bit 1 bit
Optional block data bits 42 bits
Optional block BCH code 18 bits
Trailing bit 1 bit
Total length 144 bits
In embodiments in which excessive EOT forces are reported to the HOT device
300, the
occurrence and/or measurement(s) (e.g., magnitudes) of excessive accelerations
can be
included in the "optional block data bits" portion of the message described
above or may
be sent in a separate message.
[0028] An emergency solenoid 280 is also connected to the processor 210 and
the air
brake pipe 10. When the processor 210 receives an emergency braking command
from the
HOT via the HOT transceiver 250, the processor 210 controls the solenoid 280
to open,
causing a loss of pressure in the air brake pipe 10 and activation of the
train's brakes. In
some embodiments, another solenoid (not shown in Fig. 2) is also connected to
the
processor 210 and between the air brake pipe 10 and the air powered generator
221. This
solenoid is used to perform certain tests required by the FRA.
[0029] An accelerometer 290 is also connected to the processor 210. As
discussed above,
the accelerometer may be a single axis, dual axis or three axis accelerometer
in various
embodiments. Those of skill in the art will recognize that the signals from
some
accelerometers may be in analog form and that an analog-to-digital (A/D)
converter (not
shown in Fig. 3) may be used to convert the analog sensor signal to digital
form if the
processor 210 does not include an integral A/D converter. The accelerometer
290
preferably measures instantaneous acceleration. The processor 210 is
configured to filter
the instantaneous acceleration reported from the accelerometer in some
embodiments; in
other embodiments, no filtering is used. In embodiments in which filtering of
the
instantaneous accelerations measured by the accelerometer is employed, care
must be
taken in choosing the filtering parameters such that sensitivity to
accelerations of short
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temporal duration (such as those that may occur when an end of train is first
forced into
motion from a stopped state by a locomotive) are not missed. Some embodiments
employ
a moving window average filter with a window size of the three most recent
readings, with
readings being taken every 10 milliseconds.
[0030] Also connected to the processor 210 is an event recorder 295. The event
recorder
295 records data pertinent to the EOT unit 100, such as the content and time
of
transmission of various messages sent and received by the EOT unit 100. As
discussed
above, the occurrence of excessive acceleration events are also recorded for
later retrieval
in some embodiments. The data recorded for such events can include the date,
time, and
location of the train at the time of the event as reported by the positioning
system 270 plus
other circumstances surrounding the event.
[0031] The processor 210 is further connected to a positioning system 270,
which is a
GPS receiver in preferred embodiments but may also be an INS (intertial
navigation
system), LORAN device, or any other positioning system. The positioning system
270
supplies the processor 210 with reports on the position of the EOT unit 100.
[0032] The processor 210 is also connected to a cellular modem 260. The
processor 210
uses the cellular modem to send reports including an identifier of the EOT
unit 100 and
location (and preferably time) information obtained from the positioning
system 270 to an
EOT tracking station at periodic intervals. The processor 210 also receives
"page"
messages (messages requesting the EOT unit to report its current location) and
"disable"
messages (messages instructing the EOT unit to enter an non-operational state)
via the
cellular modem 260. In addition to reporting EOT location to the EOT tracking
facility
302, the cellular modem 260 may also report excessive accelerations detected
by the
accelerometer 290. This reporting is in addition to (or, in some embodiments,
in lieu of,
the reporting accomplished via recording at the EOT event recorder 295, the
display at the
HOT device 300, and/or the recording at the event recorder 301).
[0033] During normal operation, the processor 210 controls the EOT marker
light 140,
communicates air brake pipe pressure information to the HOT, activates the
emergency
solenoid 280 in response to commands from the HOT, communicates train position
to the
EOT tracking facility 302 and performs other functions that will not be
discussed further
herein to avoid obscuring this disclosure.
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[0034] In addition to the operations discussed above, the processor 210
monitors the
accelerometer 290 in order to detect excessive accelerations. A flowchart 400
of the
operations performed by the processor 210 is shown in Figure 4. The processor
reads the
accelerometer 290 at step 402 and uses the value read (which is an
instantaneous
acceleration in this embodiment) to calculate a filtered acceleration value at
step 404. In
some embodiments, the filtering algorithm is a moving window filter with a
width of three
accelerations values. The processor 210 then compares the filtered
acceleration to a
threshold at step 406. The threshold may be a fixed value, or may be set by an
operator of
the train on which the EOT unit 100 is mounted and communicated by messages
received
from the HOT device, or may be communicated to the EOT unit 100 via a message
received on the cellular modem 260 from the EOT Tracking Facility 302. Others
ways of
setting the threshold are also possible. The comparison of step 210 may be an
absolute
value comparison (i.e., the absolute value of the acceleration is compared to
a threshold)
or may be a signed value comparison. An absolute value comparison is
preferable in some
circumstances (e.g., in connection with an accelerometer measuring vertical
acceleration
for the purpose of detecting track defects) whereas a signed value comparison
is preferable
in others (e.g., in connection with an accelerometer measuring acceleration in
the direction
of the track for the purpose of detecting accelerations caused by an operator
incorrectly
starting movement of a train).
[0035] If the filtered acceleration is below the threshold, no reporting is
necessary and the
processor 210 delays a period of time (100 ms in some embodiments) at step 408
before
repeating step 402. If the filtered acceleration exceeds the threshold at step
406, the
processor 210 records the filtered acceleration in the EOT event recorder 295
at step 410.
Next, the processor 210 reports the filtered acceleration to the EOT Tracking
Facility 302
via the cellular modem 260 at step 412. The processor 210 then reports the
filtered
acceleration to the HOT device 300 at step 414. The processor then delays for
a brief
period at step 408 before repeating steps 402 and following.
[0036] The HOT device 300 of Fig. 1 is shown in more detail in Fig. 5. As
discussed
above, the HOT device is typically (but not necessarily) mounted in a
locomotive at the
head of the train. In North America, the HOT device 300 communicates with the
EOT
unit 100 using a short range 2-watt digital radio transceiver over certain
frequencies
assigned by the FCC in the U.S. Additional details concerning HOT device/EOT
unit
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communications can be found in U.S. Pat. App. No. 11/929,605.
Shown in Fig. 5 is an EOT emergency switch
342 for use by an operator in initiating an emergency braking operation. A
display 350
indicates the brake pressure measured by the EOT unit 100, and a second
display 351 is
used for displaying various messages including a message indirating that an
excessive
EOT force/acceleration has been detected can be displayed to the operator. A
keypad 340
is available to the operator for entering data such as the serial number of
the EOT unit 100
with which the HOT device 300 is to communicate. Various indicators 330, some
of
which are combined with push buttons are available for use by the operator as
described
further in the above-mentioned application. One of the indicators 330
indicates to the
operator when the train is in motion.
[0037] A block diagram of the HOT device 300 is shown in Fig. 6. The HOT
device
includes a processor 320 which is connected to a memory (the memory is shown
onboard
the processor 320 in Fig. 6, but those of skill in the art will recognize that
one or more
external memories, such as ROM, RAM, etc. may also be used). The processor 320
is
connected (via an interface not shown in Fig. 6) to a train event recorder
301. An EOT
transceiver 330 is also connected to the processor 320 for communications with
an EOT
unit 100. A speed sensor input port 360 connects the processor 320 to a speed
sensor 470.
A GPS receiver 480 is also connected to the processor 320 in some embodiments
(this is
particularly useful in the event that the EOT unit 100 does not include its
own GPS
receiver; in this case, the GPS position from the GPS receiver 480 can be used
to
determine and report the location of the train upon the receipt of an
excessive EOT force
message from the EOT unit 100 and an approximate EOT location can be
calculated with
knowledge of a length of the train).
[0038] Fig. 7 is a flowchart 600 illustrating operations performed by the HOT
device 300
in some embodiments of the invention. Less than all of the reporting steps
illustrated in
Fig. 6 may be performed in various alternative embodiments. The flowchart of
Fig. 7 is
suitable for implementation as a subroutine called upon receipt of a message
from the EOT
unit 100. The EOT message is read at step 402. The processor 320 determines
the type of
message at step 404. If the EOT message is a message other than an excessive
force
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message, other processing (which shall not be discussed in detail herein to
avoid obscuring
the invention) is performed at step 406.
[0039] If the message from the EOT does indicate that an excessive EOT force
has been
detected by the EOT unit 100 at step 404, a message is displayed at the HOT
display 351
at step 408. In those embodiments in which the excessive force message from
the EOT
only indicates that an excessive EOT force has been detected, the message in
the display
351 may simply indicate "EXCS EOT ACC DET." In those embodiments in which the
detected EOT force is reported in the message from the EOT, the HOT may
display a
message such as "EOT ACC XXG DET," where XX represents the EOT acceleration
(filtered or unfiltered) reported by the EOT unit 100. In those embodiments
utilizing a
triaxial accelerometer, the message shown to the operator in display 351 may
also include
an X, Y, or Z to indicate the axis on which the excessive EOT acceleration
occurred. In
some embodiments, the processor 320 may take corrective action, such as
requiring the
operator to acknowledge the excessive acceleration (e.g., by pushing one of
the indicator
buttons 330 or keys 340) or forcing an emergency braking operation in the
event that no
acknowledgement from the operator is received. Such corrective action may
occur only
when the EOT acceleration exceeds a second, higher threshold and/or only after
a certain
number of excessive accelerations have been detected in some period of time in
some
embodiments. In yet other embodiments, the processor 320 requires an operator
acknowledgement if a first threshold is exceeded and initiates an emergency
braking
operation if the second threshold is exceeded.
[0041] It should be noted that, in some embodiments, the accelerometer may be
used to
both a) determine whether the train is in motion, and b) detect excessive EOT
acceleration.
In such embodiments, a first threshold is used for the former and a second,
higher
threshold is used for the latter. Such embodiment may also employ a still
higher third
threshold that can be used to include an indication in a message to a head of
train device
that the train's brakes should be activated (alternatively, the third
threshold can be
implemented in the HOT device).
[0041] Next, the processor 320 records the occurrence of the excessive EOT
force at the
event recorder 301 at step 410 and transmits a message to a central office
(e.g., a
dispatcher) at step 412. The next EOT message is then processed at step 402.
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Alternatively, in embodiments in which the excessive force indication is in a
message with
the format of Table 1, the rest of the message is processed at step 406.
[0040] Those of skill in the art will recognize that various modifications to
the EOT unit
100 are possible. For example, it is possible to operate the EOT unit 100
solely with
battery power rather than using batteries in conjunction with an air powered
generator.
Cellular modem 260 may be replaced with any type of wireless communication
system.
Various other modifications to the components of the EOT unit 100 are also
possible.
[0041] Furthermore, the purpose of the Abstract is to enable the U.S. Patent
and
Trademark Office and the public generally, and especially the scientists,
engineers and
practitioners in the art who are not familiar with patent or legal terms or
phraseology, to
determine quickly from a cursory inspection the nature and essence of the
technical
disclosure of the application. The Abstract is not intended to be limiting as
to the scope of
the present invention in any way.
[0042] While the invention has been described with respect to certain specific
embodiments, it will be appreciated that many modifications and changes may be
made by
those skilled in the art without departing from the scope of the invention. It
is intended
therefore, by the appended claims to cover all such modifications and changes
as fall
within the true scope of the invention.
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