Note: Descriptions are shown in the official language in which they were submitted.
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METHOD & APPARATUS FOR A HYBRID TRAIN CONTROL DEVICE
BACKGROUND OF THE INVENTION
Parent Case Text
This utility application benefits from provisional application of U.S. Ser.
No. 61/127,675
filed on May 15,2008.
Field of the Invention:
This invention relates generally to train control systems, and more
specifically to a train
control system that combines certain structures of cab-signaling technology
with structures used
in communication based train control (CBTC) technology. A hybrid train control
system
employs traditional wayside fixed blocks with associated cab-signal control
devices, as well as
intelligent CBTC carborne equipment. The cab-signal control devices generate
discrete speed
commands that are injected into the running rails of the various cab-signaling
blocks. In turn, an
intelligent CBTC carborne device determines the location of the associated
train, and generates a
movement authority limit (MAL) based on the speed commands received from the
wayside cab-
signaling devices.
Description of Prior Art:
Cab-signaling technology is well known, and has evolved from fixed block,
wayside
signaling. Typically, a cab-signal system includes wayside elements that
generate discrete speed
commands based on a number of factors that include train detection data, civil
speed limits, train
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characteristics, and track geometry data. The speed commands are injected into
the running rails
of the various cab-signaling blocks, and are received by trains operating on
these blocks via
pickup coils. A cab-signal system also includes carborne devices that present
the speed
information to train operators, and which ensure that the actual speed of a
train does not exceed
the speed received from the wayside.
CBTC technology is also known in the art, and has been gaining popularity as
the
technology of choice for new transit properties. A CBTC system is based on
continuous two-
way communications between intelligent trains and Zone controllers on,the
wayside. An
intelligent train determines its own location, and generates and enforces a
safe speed profile.
There are a number of structures known in the art for a train to deterMine its
own location
independent of track circuits. One such structure uses a plurality of passive
transponders that are
located on the track between the rails to provide reference locations to
approaching trains. Using
a speed measurement system, such as a tachometer, the vital onboard computer
continuously
calculates the location and speed of the train between transponders.
The operation of CBTC is based on the moving block principle, which requires
trains in
an area to continuously report their locations to a Zone Controller. In turn,
the Zone Controller
transmits to all trains in the area a data map that contains the topography of
the tracks (i.e.,
grades, curves, super-elevation, etc.), the civil speed limits, and the
locations of wayside signal
equipment. The Zone controller, also, tracks all trains in its area,
calculates and transmits to each
train a movement authority limit. A movement authority is normally limited by
a train ahead, a
wayside signal displaying a stop indication, a failed track circuit, an end of
track, or the like.
Upon receiving a movement authority limit, the onboard computer generates a
speed profile
(speed vs. distance curve) that takes into account the limit of the movement
authority, the civil
speed limits, the topography of the track, and the braking characteristics of
the train. The
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onboard computer, also, ensures that the actual speed of the train does not
exceed the safe speed
limit.
CBTC has a number of advantages over cab-signaling technology, including
shorter
headways, enforcement of temporary speed limits, and enabling trains with
different traction and
braking characteristics to operate on the same line.
While the benefits and advantages of CBTC are well known, it is difficult to
migrate a
cab-signaling installation to a CBTC installation. Also, when implementing an
extension to an
existing line controlled by cab-signaling, a transit or a rail property is
normally limited to a
single choice, namely to use the same train control technology that is used on
the existing line.
In addition, it is desirable to standardize the man-machine-interface provided
by cab-signaling
and CBTC systems. Further, it desirable to achieve a certain level of
interoperability between
cab- signaling and CBTC. The current invention provides a structure that
facilitates the
migration from cab-signaling to CBTC, enables the use of CBTC technology on an
extension of
a line that is controlled by cab-signaling, provides a man-machine-interface
for cab-signaling
systems that is based on the distance-to-go format, and enables CBTC equipped
trains to operate
with wayside cab-signaling devices.
OBJECT OF THE INVENTION
This invention relates to train control systems, and in particular to a hybrid
train control
system that integrates conventional wayside cab-signaling devices with CBTC
onboard
computers. Accordingly, it is an object of the current invention to provide a
method to translate
speed limit information generated by cab-signaling equipment into movement
authority limits.
It is another object of this invention to provide an onboard train control
device that
receives speed limit information from wayside signal control devices, and
generates a movement
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authority limit that corresponds to the received speed information, based on
the current location
of the train.
It is also an object of this invention to provide an onboard train control
device that
receives speed limit information from wayside cab-signaling devices, and
calculates a range of
location for the train ahead based on the speed limit information received
from wayside devices,
the current location of the train, and a vital data base stored onboard that
includes the topography
of the track, civil speed limits, and the location of wayside signal
equipment.
It is still an object of this invention to provide an onboard train control
device that
receives speed limit information from wayside cab-signaling devices, and
provides a positive
stop operation in the form of a movement authority limit.
It is another object of the invention to provide an onboard train control
device that
receives speed limit information from wayside cab-signaling devices, and
provides a positive
stop operation in the form of a movement authority limit at locations
identified in an on-board
data base.
It is a further object of this invention to provide an onboard train control
device that
receives speed limit information from wayside cab-signaling devices, and
calculates
corresponding movement authority limits for the train such that an improvement
in the operating
headway provided by the wayside cab-signaling system is achieved.
It is another object of this invention to provide an onboard train control
device that
receives speed limit information from wayside cab-signaling devices, and which
provides a man-
machine-interface that is compatible with a CBTC man-machine-interface.
It is also an object of this invention to provide an onboard train control
device that
receives speed limit information from wayside cab-signaling devices, and
calculates
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corresponding movement authority limits, wherein the allowable safe speed
limits are based on
temporary speed restrictions received from an Automatic Train Supervision
system.
It is still an object of this invention to provide a wayside train control
device that controls
an area of a railroad, and which has two way communications with trains
operating in that area,
and which receives location information from said trains, and which also
receives speed limit
information from a plurality of wayside cab-signaling devices, and which
issues movement
authority limits to said trains, wherein the speed limit information
represents the allowed speeds
in cab-signaling blocks that are determined by the cab-signaling devices based
on the location of
the trains in the area..
It is also an object of this invention to provide an onboard train control
device that
operates in both cab-signaling and CBTC territory, and which provides a
uniform man-machine-
interface in the form of a movement authority limit.
It is another object of this invention to provide an onboard train control
device that
receives speed limit information from wayside cab-signaling devices, and which
calculates
corresponding movement authority limits and allowable speed limits based on
the specific
traction and braking characteristics of the train, and civil speed limits
stored in an onboard vital
data base.
It is yet an object of this invention to provide an onboard train control
device that
receives speed limit information from wayside cab-signaling devices, as well
as movement
authority limits from wayside zone controllers, and which calculates
corresponding movement
authority limits for the train based on a predetermined criterion.
It is also an object of this invention to provide an onboard train control
device that
receives speed limit information from wayside cab-signaling devices, and which
includes a
plurality of modules to interface the control device with a plurality of cab-
signaling systems.
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It is still an object of this invention to provide an onboard train control
device that
receives speed limit information from wayside cab-signaling devices, and which
also receives
information related to the states of interlocking devices in the area, and
calculates corresponding
movement authority limits that reflect said states of interlocking devices.
It is a further object of this invention to provide an onboard train control
device that
receives speed limit information from wayside cab-signaling devices, receives
train location
information from an onboard train location determination system, and which
calculates
corresponding movement authority limits based on one or a plurality of lookup
tables.
It is another object of this invention to provide an onboard train control
device that
receives speed limit information from wayside cab-signaling devices, and which
translates the
speed limit information into an obstruction location that defines a movement
authority for the
train.
It is also an object of this invention to provide an onboard train control
device that
receives a sequence of speed limit commands from wayside devices as the train
moves through
wayside cab-signaling blocks, and generates safe movement authority limits
that are based on the
design criteria for the wayside cab-signaling blocks, the configuration of the
wayside cab-
signaling blocks, the location of wayside interlocking devices, and the
failure modes of the
wayside cab-signaling devices.
It is still an object of the current invention to provide an onboard train
control device that
receives speed limit information from wayside devices, and translates these
speed limits into
movement authority limits in order to provide a train control system that is
independent of the
design assumptions for the wayside cab-signaling block design.
It is a further object of the invention to provide an onboard train control
device that
receives speed limit information from wayside devices, and translates these
speed limits into
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movement authority limits, and then generates an on-board stopping profile
that reflects civil
speed limits included in an onboard data base.
It is also an object of the invention to provide an onboard train control
device that
receives speed limit information from wayside devices, and translates these
speed limits into
movement authority limits based in part on the transition between specific
speed limits in two
adjacent cab-signaling blocks.
BRIEF SUMMARY OF THE INVENTION
The foregoing and other objects of the invention are achieved in accordance
with a
preferred embodiment of the invention that provides a hybrid train control
system that integrates
conventional wayside cab-signaling devices with CBTC onboard computers. The
onboard
CBTC computers could also communicate with an Automatic Train Supervision
System (ATS),
which controls wayside interlocking equipment, as well as provides service
delivery
functionalities. The ATS system provides information related to temporary
speed restrictions,
work zone limits, and status of interlocking devices.
The configuration of an onboard CBTC device is similar to conventional vital
onboard
CBTC computers, and includes an independent location and speed determination
subsystem, an
interface to the traction, braking and other car subsystems, a vital data base
that includes data
related to track topography, civil speed limits, and location of wayside
signal devices. In
addition, the onboard CBTC device includes an interface to a cab-signaling
pickup coil that
receives wayside speed limit information coded in electrical signals that are
injected through the
running rails. For the preferred embodiment, the location determination
subsystem is based on a
plurality of transponders located on the track. Passive transponders are used
to provide reference
locations to the on-board location and speed determination subsystem. Between
transponders, an
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odometry device continuously calculates train location and speed. Further,
dynamic
transponders could be used at home signal locations to provide vital route
information to the on-
board equipment.
It should be noted that the disclosure of a transponder based system to
provide an
independent location and speed determination is being provided for the purpose
of describing the
preferred embodiment, and is not intended to limit the invention herein. As
would be
appreciated by a person skilled in the art, any location and speed
determination system that is
independent of the wayside track circuits could be used with this invention.
Examples of such
location and speed determination subsystems include figure 8 inductive loops,
radio triangulation
devices, global positioning devices (GPS), or the like.
The methodology described in the preferred embodiment is based on the
conversion of
received cab-signal speed codes into movement authority limits. There are two
main steps in
implementing such conversion. First, the on-board CBTC equipment determines
the cab-
signaling block where the front end of the train is currently located. This
determination is made
based on the current location of the train (as calculated by the on-board
location subsystem), and
the vital data base information. The second step is to determine the block
boundary location for
the cab-signaling block where a track obstruction exists. A track obstruction
could be a train
ahead, a stop signal, a failed wayside detection block, an end of track, a
temporary track block,
or the Re. This determination of block boundary location could be implemented
using a lookup
table that reflects the wayside cab-signaling speed codes versus the statuses
of the various
wayside detection blocks. Alternatively, said block boundary location
determination could be
implemented by an algorithm that employs cab-signaling speed code received,
current cab-
signaling block, and cab-signaling design parameters (i.e. train
characteristics, track profile data,
reaction times, train resistance formulas used, etc.).
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Upon the identification of the cab-signaling block where a track obstruction
exists, the
on-board CBTC computer will generate a movement authority limit up to the
block entry
location for this cab-signaling block. A buffer zone is provided before said
block entry location
to ensure minimum safe separation to a train located at the beginning of the
block where the
track obstruction is located. This movement authority limit is enforced by the
on-board CBTC
equipment. Similar to a CBTC operation, the on-board vital controller will
generate a stopping
profile (speed/distance curve) to control the speed of the train, and enforce
the stopping of the
train at the end of the movement authority limit. Such stopping profile
incorporates the civil
speed limits present in the wayside signal configuration. The on-board vital
controller also
provides over-speed protection by ensuring that the actual speed of the train
does not exceed the
allowable speed limit.
It should be noted that the generation of the movement authority limit is a
dynamic
process that corresponds directly to the cab-signaling speed code received
from the wayside
devices. Within a block, the on-board CBTC equipment will respond to any
change in the
received cab-signaling speed code limit. A more restrictive speed code will
result in a truncation
of the movement authority limit. Alternatively, a more permissive speed code
will result in an
expanded movement authority limit.
It should also be noted that when a train enters a new block, the norm is that
the
movement authority limit remains the same. The exception is when the track
obstruction
limiting the movement authority moves to a different cab-signaling block
simultaneously with
the movement of the train to the new block. This means that under normal
operation, the
dynamic changes in movement authorities will most likely occur within the
boundaries of the
various blocks.
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This hybrid architecture provides a number of safety and operational benefits.
First, a
movement authority normally extends beyond the entry boundary of the block
with a "stop" or
"stop and proceed" speed code. More specifically the movement authority limit
could extend to
the exit boundary of the block in the approach to the block where the
obstruction exists. Such
extension of the movement authority limit provides an enhancement of the
existing throughput.
Second, this hybrid architecture can be used to convert an existing "stop and
proceed" operation
to a "positive stop" operation-by the inherent nature of the movement
authority limit. In such
applications, the hybrid architecture could be used to enhance safety of
operation.
This concept could also be implemented such that a combination of "positive
stop," and
"stop and proceed" operations are provided at different geographical locations
based on a data
base parameter. For example, a "positive stop" operation could be provided at
home signal
locations. At the same time, "stop and proceed" operation could be provided at
the boundary of
certain blocks where it is desired to close in on a train ahead under the
protection of the operating
rules. This is implemented by a data base parameter that controls the
selection of either a
"positive stop" operation, or a "stop and proceed" operation at the end of a
movement authority
limit. Further, for systems where an ATS subsystem is employed, this data base
parameter could
be enabled by the ATS dispatcher at a central control location. An acknowledge
function is then
provided on-board the train to ensure that the train operator is aware of the
"stop and proceed"
operation at this location.
Other benefits of this architecture include providing smoother operation
through the
elimination of code change points at the boundaries between the various
blocks, making the train
propulsion and braking characteristics independent of the wayside cab-
signaling block design,
and facilitating the transition from cab-signaling to CBTC operation by
enabling mixed fleet
operation (i.e. cab-signaling trains operating on the same track with CBTC
trains). Another type
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of mixed fleet operation could be provided where, for example, it is desired
to operate freight
trains on the same tracks with commuter trains. In such a case, each type of
train will operate on
the line based on its own propulsion and braking characteristics, and
independent of the
assumptions made for the wayside cab-signaling block design.
It should be noted that the concept of hybrid architecture could be
implemented on an
extension of an existing cab-signaling line. The line extension will be
equipped with wayside
CBTC zone controllers. New trains operating on the extension are equipped with
the hybrid on-
board device, and are able to operate on both the main line and extension
tracks using a
movement authority type operation. Old trains equipped with on-board cab-
signaling equipment
will continue to operate on the main line tracks in a mixed fleet operation,
but cannot operate on
the new extension tracks. Obviously, if it is desired to operate the old
trains on the extension
tracks, then they must be retrofitted with hybrid on-board equipment.
It should also be noted that this hybrid architecture could be used with cab-
signaling
systems that employ the running rails to transmit speed information to trains,
or with cab-
signaling systems that employ inductive loops. This architecture could also be
used with cab-
signaling systems that employ a distant-to-go type operation within a block.
Another advantage of this hybrid architecture is to enable trains with
different traction
and breaking characteristics to operate with existing cab-signaling wayside
installations. In
effect, this architecture will make train control independent of the
assumptions used to design the
wayside cab-signaling block layout.
This hybrid architecture also provides conventional CBTC operation in areas
equipped
with wayside zone controllers. In such areas, a train continuously transmits
its location to the
wayside zone controller via the data communication subsystem. In turn, a zone
controller tracks
the trains in an area, and issues a movement authority to a train based on the
location of the track
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obstruction ahead. This movement authority limit is transmitted to the train
via the data
communication network. The on-board computer then generates and enforces a
stopping
profile that corresponds to the received movement authority limit.
According to one aspect of the present invention, there is provided an on-
board
train control system that interfaces with a wayside cab-signalling
installation comprising: an
on-board location determination subsystem, on-board means for receiving, and
decoding cab-
signalling speed codes, on-board means for converting said cab-signalling
speed codes to
corresponding movement authority limits, and on-board means for generating a
stopping
profile to enforce a movement authority limit; wherein the generation of the
movement
authority limit (32) is a dynamic process that corresponds directly to the cab-
signalling speed
code (30) received from the wayside devices, such that a more restrictive
speed code will
result in a truncation of the movement authority limit and a more permissive
speed code will
result in an expanded movement authority limit.
According to another aspect of the present invention, there is provided a
method for a vital on-board train controller that interfaces with a wayside
cab-signalling
installation comprising the on-board steps of: determining the location of the
train, converting
speed codes received from wayside devices into movement authority limits, and
generating
and enforcing stopping profiles based on said movement authority limits
wherein the
generation of the movement authority limit is a dynamic process that
corresponds directly to
the cab-signalling speed code received from the wayside devices, such that a
more restrictive
speed code will result in a truncation of the movement authority limit and a
more permissive
speed code will result in an expanded movement authority limit.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other more detailed and specific objectives will be disclosed in the
course of the following description taken in conjunction with the accompanying
drawings
wherein:
FIG. 1 is a block diagram of a hybrid cab-signaling/CBTC onboard unit
showing a cab-signal interface in accordance with the invention.
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FIG. 2 indicates a block diagram of the process used to convert a cab-
signaling
speed limit into a movement authority limit in accordance with the invention.
FIG.3 shows a two step process to convert a cab-signaling speed limit into a
movement authority limit using lookup tables.
FIG.4 shows a sequence of cab-signaling blocks, and demonstrates the process
used to map the CBTC train location to said blocks for the purpose of
identifying which block
is occupied by the train.
FIG. 5 shows a lookup table to generate movement authority limits that
correspond to received cab-signaling speed codes, for various wayside blocks.
FIG. 6 shows the cab-signaling movement authority limits for consecutive
blocks relative to the position of a train ahead.
FIG. 7 shows the cab-signaling movement authority limits for consecutive
blocks relative to the position of a wayside signal that displays a stop
aspect.
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FIG. 8 indicates a wayside cab-signaling block layout that employs "no code"
for "stop
& proceed" operation.
FIG. 9 shows a cab-signaling movement authority relative to a CBTC movement
authority for the condition of a train ahead.
FIG. 10 shows a cab-signaling movement authority relative to a CBTC movement
authority for the condition of a signal ahead displaying a stop aspect.
FIG. 11 shows a lookup table to generate movement authority limits that
correspond to
received cab-signaling speed codes, for various wayside blocks, as well as
type of operation
desired at each block when a no code condition exists.
FIGS. 12-14 show an example of the operation of the preferred embodiment
according to
the current invention in a section of the track where a civil speed limit is
present.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The preferred embodiment of the present invention describes a structure,
and/or a method
to provide safe operation of trains over sections of cab-signaling track
territory. The main
concept of the present invention is to employ cab-signaling speed codes
received from wayside
cab-signaling devices to generate corresponding movement authority limits on
board trains. In
effect the structure used by the present invention is a hybrid architecture
that combines wayside
cab-signaling devices, and onboard CBTC controller.
The present invention maintains the running rails as an integral part of the
train control
system, while providing many of the advantages of CBTC operation. The
preferred embodiment
also employs a vital on-board data base that includes track topography
information, cab-
signaling block configuration, location of wayside signal devices, limits of
station platforms, and
civil speed limits. A cab-signaling pickup coil, together with a cab-signaling
decoder, is used to
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detect and decode the cab-signaling code rate present in the running rails.
Further, a reverse cab-
signaling design process is used to determine the location of the obstacle
corresponding to the
received cab-signaling rate.
Referring now to the drawings where the illustrations are for the purpose of
describing
the preferred embodiment of the invention and are not intended to limit the
invention hereto,
FIG. 1 is a block diagram of the onboard train control device in accordance
with the preferred
embodiment of the invention. It includes a vital onboard controller (VOBC) 10,
which includes a
vital data base 20. The VOBC 10 interfaces with a transponder reader 12, an
odometry device
14, a data communication unit 18, the car propulsion and braking systems 16,
and a cab-
signaling interface unit 22. The transponder reader 12 receives location
information from
passive transponders installed on the tracks, and provides reference location
information to the
on-board location determination subsystem. The transponder reader 12 could
also provide route
data based on information provided by wayside interlocking devices to dynamic
transponders
located at said interlocking devices. The odometry device 14 provides location
and/or speed
measurement functions to the VOBC 10 so that the VOBC 10 can continuously
determines the
location and speed of the train as the train moves on the track. Similar to
traditional CBTC
systems, the reference location received from the transponder reader 12 is
used to reset any
uncertainty in the calculated train location.
The data communication unit 18 is an optional device, and is used in
embodiments that
employ wayside zone controllers. In such a case, the VOBC 10 receives CBTC
movement
authority limits (MAL) from wayside zone controllers, and transmits the train
location to said
zone controllers via the data communication unit 18. The cab-signal interface
unit 22 provides
the cab-signaling speed code signal detected in the rails to the VOBC 10. This
signal is normally
in the form of a modulated carrier frequency. The code rates normally
correspond to the cab-
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signaling speed limits in the wayside cab-signaling blocks. The decoding or
demodulation of the
received speed signal could be performed as part of the cab-signaling
interface unit 22, or could
be integrated in the VOBC functions.
FIG. 2 describes the general process of translating the decoded cab-signaling
speed 30
into a cab-signaling movement authority limit 32. In effect, the vital control
logic embedded in
the VOBC 10 generates a movement authority limit 32 that corresponds to the
received cab-
signaling speed limit 30 using a reverse cab-signaling block design process
24. The data
required for such process includes the CBTC train location 28, the cab-
signaling block
boundaries 25, the decoded cab-signaling speed 30, and route data 26 if
required. The CBTC
train location 28 is generated by the on-board location determination
subsystem based on
information received from the transponder reader 12 and the odometry unit 14.
It should be noted that the labeling of the train location data 28 as CBTC
train location is
disclosed for the purposes of describing the preferred embodiment, which has
hybrid architecture
so that the on-board VOBC 10 can operate both in cab-signaling and CBTC
territory. As would
be appreciated by a person skilled in the art, this concept could be used to
operate entirely in cab-
signaling territory, and in such a case the CBTC train location data 28 could
be simply labeled
on-board train location.
The cab-signaling block boundaries data is stored in the on-board vital data
base as part
of a dataset that includes the topography of the track (i.e. track stationing
information, grade
information, curve information, super elevation data, etc.), civil speed
limits, location of wayside
signal equipment, location of station platforms, etc.
The route data 26 includes the position of wayside track switches, and the
status of
wayside signals. This route data 26 is not normally required for the
determination of a cab-
signaling movement authority limit except in wayside cab-signaling
installations where a cab-
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signaling speed code is based in-part on a civil speed limit present at an
interlocking route (for
example, when a train proceeds over a diverging route). Route data 26 could
also be required to
provide information to operating personnel on the train operator display
(TOD).
Depending on the application requirements, the route data 26 could be provided
by
wayside transponders, from a wayside zone controller, or from the ATS
subsystem using the data
communication unit 18. The route data 26 could also be implied from the
received cab-signaling
speed code 30 in conjunction with information stored in the on-board data base
20.
The reverse cab-signaling design process 24 could be implemented by one of a
plurality
of structures. A software algorithm could be provided to identify the location
of the block where
an obstacle exists (train ahead, stop signal, end of track, etc.). Such
software algorithm will be
based on track topography data, and design assumptions used for the wayside
cab-signaling
block design. For example, train traction or propulsion characteristics, safe
braking model,
reaction times, etc. A second structure is shown in FIG. 3, and is based on a
two step process
that employs lookup tables.
In the first step 34, lookup table 1 is used to identify the wayside block 38
where the front
end of the train is located. This lookup table uses the CBTC train location 28
as determined by
the on-board train location subsystem, and the boundary location information
for the wayside
blocks 40, which are provided by the on-board vital data base, to identify
said wayside block 38.
A graphical representation of this first step 34 is shown in FIG. 4. Wayside
block Bi 44, where
the train is located, is determined by comparing the on-board train location
46 with the
boundaries of the various wayside blocks. This process continues as the train
moves in the
established traffic direction 42.
In the second step 36 shown in FIG. 3, lookup table 2 is used to determine the
cab-
signaling movement authority limit 32. This lookup table uses the block
information 38
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determined in the first step, and the received cab-signaling speed code 30 to
generate the cab-
signaling MAL 32. FIG. 5 shows an example of a lookup table where MAL12 56
represents the
cab-signaling movement authority limit that corresponds to cab-signaling speed
code S2 54 when
the train is in block Bi 52. As the train continues to move in the established
direction of traffic
42, new movement authority will be generated based on the block identity, and
the received
speed code limit.
It should be noted, and as shown in FIG. 6, with a train 62 in block Bi+4 64
traveling in
the established direction of traffic 42, the movement authority limits Bi 66,
Bi+i 68, B1+2 70, and
B1+3 72 terminate at the same point, namely at the beginning of a buffer zone
at the boundary
between blocks B1+3 & B1+4. This means that as the following train 65 crosses
to a new block, the
movement authority for the train will most likely remains the same. The
exception occurs when
simultaneously with the following train 65 crossing to a new block, the
preceding train 62 also
moves to a new block. This also means that a change in the movement authority
limit for a train
will most likely occur within a block rather than at a block boundary. FIG. 7
shows that the
same operation indicated in FIG. 6 occurs when the movement authorities 78,
80,82 & 84 are
limited by a signal 74 displaying a stop aspect.
It should also be noted that a movement authority is truncated only in the
event of a
failure, or if an unusual operating condition occurs. For example, a track
circuit failure, or a loss
of speed code will result in a truncation of movement authority. Also, the
cancellation or
downgrading of an aspect at a wayside signal will cause the movement authority
to be truncated.
A movement authority limit generated by the VOBC 10, or received from the
wayside
zone controller via the CBTC data communication subsystem 18 is enforced by
the on-board
VOBC 10. Similar to a CBTC operation, the vital on-board controller 10 will
generate a
stopping profile (speed/distance curve) to control the speed of the train, and
enforce the stopping
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of the train at the end of the movement authority limit. Such stopping profile
incorporates the
civil speed limits present in the wayside signal configuration, and stored in
the on-board vital
data base 20. The VOBC 10 also provides over-speed protection by ensuring that
the actual
speed of the train as measured by the odometry module 14 does not exceed the
allowable speed
limit determined by the generated stopping profile. In the event of an over-
speed condition, the
VOBC will activate the train brake subsystem.
In overlap areas between cab-signaling and CBTC territories, it is possible to
receive both
a movement authority from a wayside zone controller, and a cab-signaling speed
code limit from
cab-signaling wayside devices. In such a case, and since both generated and
received movement
authority limits are vital, the more permissive movement authority limit is
used. As would be
appreciated by a person skilled in the art, an on-board logic could be added
to define precisely
the demarcation point between cab-signaling based operation and CBTC based
operation. Such
logic will depend on information stored in the vital data base.
The hybrid architecture shown in FIG. 1 for the preferred embodiment could be
implemented with both a cab-signaling system that employs a dedicated code
"SO" for a
"positive stop" operation, as well as a cab-signaling system that employs a no
code "NC" to
provide a "stop & proceed" operation. FIG. 8 demonstrates how the concept
presented herein is
implemented when no code "NC" 92 is used as part of normal operation. More
specifically, the
system must differentiate between the NC 92 corresponding to "stop & proceed"
operation, and a
no code resulting from a loss of cab-signaling code in a block, i.e. a failure
caused by either
trackside equipment or in the on-board cab-signaling interface unit 22.
As shown in FIG. 8, when a train 86 crosses the boundary point 93 between a
block that
has a valid cab-signaling code 95 and a block with no code 92, it is desirable
to maintain a valid
movement authority to the end of the block that has a no code 92. This is
possible due to the fact
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that prior to the point in time when the train 86 crosses 94 the boundary
point 93, it is receiving a
valid cab-signaling speed code S I, which indicates that the no code block 92
is vacant. This is
different from the condition when a valid cab-signaling speed code S3, S2 or
Si is lost within a
block limit resulting in a no code condition. In such a case, the no code
condition will result in a
truncated movement authority. Therefore, to implement this architecture for a
cab-signaling
system that employs no code for a "stop & proceed" operation, the on-board
data base is used to
differentiate between a no code condition within a block boundary, and a no
code condition 92 at
the boundary of a block 93 where a no code condition is expected. In this
case, the transition
from a first speed code to a no code at a block boundary is used as a pre-
requisite to maintain the
movement authority to its current limit.
As shown in FIG. 9, the architecture disclosed in the preferred embodiment
will result in
a headway improvement 106 in cab-signaling systems that provide positive stop
operation. A
train 98 following a preceding train 108 normally stops at the beginning of a
block 104 with SO
code. The cab-signaling movement authority 100 allows the train to proceed to
the end of the
block. The extent of such headway improvement 106 is dependent on the wayside
cab-signaling
block design. It should be noted that the headway improvement 106 in the case
where the
movement authority is limited by a train ahead 108 is less that the headway
improvement
provided by a CBTC movement authority 102. However, in the case where the
movement
authority is limited by a wayside signal displaying a stop aspect 118, as
shown in FIG. 10, the
headway improvement 120 is the same for both the cab-signaling based operation
as measured
by its movement authority 116, and the CBTC based operation as measured by its
movement
authority 114.
It should also be noted that the architecture shown in FIG. 1 provides a
simple and
effective way to convert a "stop & proceed" operation to a "positive stop"
operation. As shown
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in FIG. 8, a cab-signaling MAL 91 will ensure that the following train 86
stops at the end of the
block with no code condition 92, rather than a "stop & proceed" operation 90
that allows a train
to close in on the preceding train 88 under the protection of the operating
rules. This hybrid
architecture will therefore enhance the safety of operation by reducing the
reliance on the
operating rules employed in the "stop & proceed" operation, and by minimizing
the probability
of a human error.
Further, as shown in FIG. 11, the lookup table that provides the various
movement
authorities corresponding to received cab-signaling speed limits could be
expanded to include the
type of operation desired at each block when a no code condition is
encountered. For example, a
positive stop operation could be specified at the end of a block in approach
to a home signal, or
in approach to the end of track. Stop and proceed operation could be
maintained at other blocks
where it is operationally desirable to allow a train to close in on a train
ahead. In addition, where
an Automatic Train Supervision subsystem is used, and is communicating with
the vital on-board
computer 10, the "stop & proceed" operation could be enabled in the vital data
base, but
dynamically activated by the central ATS dispatcher. An acknowledgment
function could then
be implemented in the vital software of the VOBC 10 to ensure that the train
operator is
conscious of the "stop & proceed" operation at that location.
In certain cab-signaling installations, the calculation of the wayside cab-
signaling speed
code is based on track occupancies, status of wayside signal aspects as well
as additional factors.
These factors could include civil speed limits, and dynamic route information
such as when the
train operates over a diverging route. In such installations, additional
onboard lookup tables
and/or logic are provided to differentiate between a cab-signaling speed code
that reflects a civil
speed limit, and a cab-signaling speed code that reflects the position of a
train ahead, or the
condition of a wayside signal displaying a stop aspect.
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FIGS. 12 & 13 demonstrate an example of a civil speed limit 130, which limits
the speed
code in the associated block 130 to Si independent of the location of the
train ahead 124. What
is different between the two figures is the speed in the block 128 in the
approach to the block 130
associated with the civil speed limit 130. In FIG. 12, the speed limit in the
approach block 128
is S3, while in FIG. 13, the speed in said block is S2. The on-board logic
recognizes that the
transition from S2 to S1 at the border between the two blocks is a pre-
requisite to maintain a cab-
signaling MAL 122 to the end of the SO block limit 129 as shown in FIG. 12.
Alternatively, a
transition from S3 to Si will maintain a cab-signaling MAL 132 to the end of
the SO block as
shown in FIG. 13.
It should be noted that if the train ahead 124 moves to a new block while the
following
train 126 is still in the block associated with the civil speed limit, then
the cab-signaling MAL
122 will not advance, and will remain to the end of the Si block 129 as shown
in FIG. 14. This
condition, however, will not adversely impact operation since the train 126
must comply with the
civil speed limit 130 irrespective of the movement authority limit. As would
be appreciated by a
person skilled in the art, the configuration described in FIGS. 12-14 is only
one example of
various cab-signaling configurations with different civil speed limits that
could be present at a
particular line. Accordingly, as the case with traditional signal design
applications, the specific
design of the onboard logic will be customized to the specific wayside cab-
signaling block
configuration.
Similarly, additional lookup tables and/or logic are provided in applications
where the
train is operating in the approach to and on a diverging route. In such a
case, the transition
between various combinations of cab-signaling speed codes could imply the
position of the
wayside track switch. Alternatively, the position of the switch could be
provided through a
dynamic wayside transponder that is read by the on-board location subsystem.
Also, in
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embodiments where an ATS subsystem is used, information related to the
position of wayside
switches could be transmitted to the train for non-vital functions
applications such as providing
route information on the train operator display.
As would be understood by those skilled in the art, alternate embodiments
could be
provided to implement the new concepts described herein. For example,
different location
subsystems could be used to determine the location of the train independent of
the underlying
fixed block detection system. Also, different algorithms could be used to
provide a reverse cab-
signaling block design on board. In addition, this hybrid architecture could
be integrated in a
wayside zone controller. In such a case, trains will transmit their on-board
locations to the
wayside zone controller. Similarly, the speed codes from the various wayside
blocks are
imputed to the zone controller. In turn, the zone controller will determine a
movement authority
limit based on the speed code in a certain block, and will transmit said
movement authority limit
to the train in than block via the CBTC data communication subsystem.
Furthermore, the onboard VOBC 10 could be implemented using a plurality of
vital
modules. These modules could be independent software modules operating on a
common
hardware platform, or each of the modules could operate on a separate hardware
platform. In
such an alternate embodiment, a first vital module will provide the function
of location
determination; a second vital module will provide the function of decoding a
speed code, and
converting it into a movement authority limit; and a third vital module will
generate and enforce
a stopping profile based on the generated movement authority limit. The second
module could
incorporate an algorithm that performs a reverse block design process, or in
the alternative could
employ a plurality of lookup tables.
Also, alternate vital programs may be utilized to implement the conversion of
received
cab-signaling speed codes into movement authority limits. Obviously these
programs will vary
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54106-1290
from one another in some degree. However, it is well within the skill of the
signal engineer to
provide particular programs for implementing vital algorithms to achieve the
functions described
herein. It is also to be understood that the foregoing detailed description
has been given for
clearness of understanding only, and is intended to be exemplary of the
invention while not
limiting the invention to the exact embodiments shown. Obviously certain
subsets,
modifications, simplifications, variations and improvements will occur to
those skilled in the art
upon reading the foregoing. It is, therefore, to be understood that all such
modifications,
simplifications, variations and improvements have been deleted herein for the
sake of
conciseness and readability, but are properly within the scope of the
following claims.
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