Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHOD AND APPARATUS FOR OPTIMIZING RAILROAD TRAIN
OPERATION FOR A TRAIN INCLUDING MULTIPLE DISTRIBUTED-POWER
LOCOMOTIVES
CROSS-REFERENCE TO RELATED APPLICATIONS
[001] This application is a continuation-in-part application claiming the
benefit of
U.S. Patent Application entitled Trip Optimization System and Method for a
Train,
filed on March 20, 2006 and assigned application number 11/385,354, which is
hereby incorporated by reference.
FIELD OF THE INVENTION
[002] This embodiments of the invention relate to optimizing train operations,
and
more particularly to optimizing train operations for a train including
multiple
distributed power locomotive consists by monitoring and controlling train
operations
to improve efficiency while satisfying schedule constraints.
BACKGROUND OF THE INVENTION
[003] A locomotive is a complex system with numerous subsystems, each
subsystem
interdependent on other subsystems. An operator aboard a locomotive applies
tractive
and braking effort to control the speed of the locomotive and its load of
railcars to
assure safe and timely arrival at the desired destination. Speed control must
also be
exercised to maintain in-train forces within acceptable limits, thereby
avoiding
excessive coupler forces and the possibility of a train break. To perform this
function
and comply with prescribed operating speeds that may vary with the train's
location
on the track, the operator generally must have extensive experience operating
the
locomotive over the specified terrain with various railcar consists.
10041 However, even with sufficient knowledge and experience to assure safe
operation, the operator generally cannot operate the locomotive to minimize
fuel
consumption (or other operating characteristics, e.g., emissions) during a
trip.
Multiple operating factors affect fuel consumption, including, for example,
emission
limits, locomotive fuel/emissions characteristics, size and loading of
railcars, weather,
traffic conditions and locomotive operating parameters. An operator can more
effectively and efficiently operate a train (through the application of
tractive and
braking efforts) if provided control information that optimizes performance
during a
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trip while meeting a required schedule (arrival time) and using a minimal
amount of
fuel (or optimizing another operating parameter), despite the many variables
that
affect performance. Thus it is desired for the operator to operate the train
under the
guidance (or control) of an apparatus or process that advises the application
10051 A distributed power train 8, as illustrated in Figures 1 and 2,
comprises
locomotives 14-18 distributed in spaced-apart relation within the train
consist. In
addition to the head end locomotive consist 12A, including locomotives 14 and
15,
the train 8 comprises one or more additional locomotive consists (referred to
as
remote consists and the locomotives thereof referred to as remote units or
remote
locomotives) 12B and 12C. The remote unit consist 12B comprises the remote
locomotives 16 and 17; the remote unit consist 12C comprises the remote
locomotive
18. A distributed power train can improve train operation and handling by
applying
tractive and braking efforts at locations other than the train's head end.
[006] The locomotives of the remote consists 12B and 12C are controlled by
commands issued by the head end lead unit 14 and carried over a communications
system 10. Such commands, for example, may instruct the remote units to apply
braking or tractive effort. The communications system 10, referred to as a
distributed
power communications system, also carries remote unit replies to lead unit
commands, remote unit alarm condition messages and remote unit operational
parametric data. The remote unit transmissions are transmitted to the head end
lead
unit 14 for the attention of the engineer. Typically, the distributed power
communications system permits the train to be subdivided into a lead consist
and as
many as four remote consists, with each remote consist independently
controllable
from the head end.
[007] The types, contents and format of the various messages carried over the
communications system 10 are described in detail in the commonly owned United
States Patent Nos. 5,039,038 and 4,582,580, both entitled Railroad
Communication
System, which are incorporated by reference herein.
[008] For a remote consist including two or more locomotives, one of the
consist
locomotives is designated the remote consist lead unit, such as the locomotive
16 for
the remote consist 12B. The remote consist lead unit 16 receives commands and
messages from the lead unit 14, executes the commands and messages as required
and
issues corresponding commands and messages to the linked locomotive 17 over an
interconnecting cable 19 (referred to as a train line or an MU (multiple unit)
line).
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The lead unit 14 also controls operation of the linked locomotive 15 by
issuing
commands via the MU line 19 connecting the two locomotives.
[009] The communications system 10 provides communications between the head
end lead unit 14 and land-based sites, such as a dispatching center, a
locomotive
monitoring and diagnostic center, a rail yard, a loading/unloading facility
and wayside
equipment. For example, the remote consists 12B and 12C can be controlled from
either the head end lead unit 14 (Figure 1) or a control tower 40 (Figure 2).
[010] It should be understood that the only difference between the systems of
Figures 1 and 2 is that the issuance of commands and messages from the lead
unit 14
of Figure 1 is replaced by the control tower 40 of Figure 2. Typically, the
control
tower 40 communicates with the lead unit 14, which in turn is linked to the
locomotive 15 by the MU line 17 and to the remote consists 12B and 12C by the
communications system 10.
[011] The distributed power train 8 of Figures 1 and 2, further comprises a
plurality
of railcars 20 interposed between the lead consist 12A and the remote consists
12B/12C. The arrangement of the consists 12A-12C and railcars 20 illustrated
in
Figures 1 and 2 is merely exemplary as the present invention can be applied to
other
locomotive/railcar arrangements.
10121 The railcars 20 comprise an air brake system (not shown in Figures 1 and
2)
that applies the railcar air brakes in response to a pressure drop in a brake
pipe 22 and
releases the air brakes upon a pressure rise in the brake pipe 22. The brake
pipe 22
runs the length of the train for conveying the air pressure changes specified
by the
individual air brake controls 24 in the lead unit 14 and the remote units 16-
18.
[013] In certain applications an off-board repeater 26 is disposed within
radio
communications distance of the train 8 for relaying communications signals
between
the lead unit 14 and the remote consists 12B and 12C over the communications
system 10.
[014] Each of the locomotives 14-18, the off board repeater 26 and the control
tower
40 comprises a transceiver 28 operative with an antenna 29 for receiving and
transmitting communications signals over the communications system 10. The
transceiver 28 in the lead unit 14 is associated with a lead controller 30 for
generating
and issuing the commands and messages from the lead unit 14 to the remote
consists
12B and 12C and receiving reply messages therefrom. Commands are generated in
the lead controller 30 in response to operator control of the traction and
braking
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controls within the lead unit 14. Each locomotive 15-18 and the off-board
repeater 26
comprises a remote controller 32 for processing and responding to received
signals
and for issuing reply messages, alarms and commands.
BRIEF DESCRIPTION OF THE INVENTION
[015] According to one embodiment, the present invention comprises a system
for
operating a railway vehicle comprising a lead powered unit and a non-lead
powered
unit during a trip along a track. The system comprises a first element for
determining
a location of the vehicle or a time from the beginning of a current trip, a
processor
operable to receive information from the first element and an algorithm
embodied
within the processor having access to the information to create a trip plan
that
optimizes performance of one or both of the lead unit and the non-lead unit in
accordance with one or more operational criteria for one or more of the
vehicle, the
lead unit and the non-lead unit.
10161 According to another embodiment the present invention comprises a method
for operating a railway vehicle comprising a lead unit and a non-lead unit
during a trip
along a track. The method comprises determining vehicle operating parameters
and
operating constraints and executing an algorithm according to the operating
parameters and operating constraints to create a trip plan for the vehicle
that
separately optimizes performance of the lead unit and the non-lead unit,
wherein
execution of the trip plan permits independent control of the lead unit and
the non-
lead unit.
[017] According to yet another embodiment, the invention comprises a computer
software code for operating a railway vehicle comprising a computer processor,
a lead
unit and a non-lead unit during a trip along a track. The computer software
code
comprises a software module for determining vehicle operating parameters and
operating constraints and a software module for executing an algorithm
according to
the operating parameters and operating constraints to create a trip plan for
the vehicle
that independently optimizes performance of the lead unit and the non-lead
unit,
wherein execution of the trip plan permits independent control of the lead
unit and the
non-lead unit.
BRIEF DESCRIPTION OF THE DRAWINGS
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10181 A more particular description of the embodiments of the invention will
be
rendered by reference to specific embodiments thereof that are illustrated in
the
appended drawings. Understanding that these drawings depict only typical
embodiments of the invention and are not therefore to be considered to be
limiting of
its scope, the aspects of the invention will be described and explained with
additional
specificity and detail through the use of the accompanying drawings in which:
[019] FIGS. I and 2 depict distributed power railroad trains to which the
teachings
of the present invention can be applied.
10201 FIG. 3 depicts an exemplary illustration of a flow chart of the present
invention;
[0211 FIG. 4 depicts a simplified model of the train that may be employed;
[022] FIG. 5 depicts an exemplary embodiment of elements of the present
invention;
10231 FIG. 6 depicts an exemplary embodiment of a fuel-use/travel time curve;
[024] FIG. 7 depicts an exemplary embodiment of segmentation decomposition for
trip planning;
[025] FIG. 8 depicts an exemplary embodiment of a segmentation example;
10261 FIG. 9 depicts an exemplary flow chart of the present invention;
[027] FIG. 10 depicts an exemplary illustration of a dynamic display for use
by the
operator;
[028] FIG. 11 depicts another exemplary illustration of a dynamic display for
use by
the operator;
10291 FIG. 12 depicts another exemplary illustration of a dynamic display for
use by
the operator.
DETAILED DESCRIPTION OF THE INVENTION
10301 Reference will now be made in detail to the embodiments consistent with
the
invention, examples of which are illustrated in the accompanying drawings.
Wherever possible, the same reference numerals used throughout the drawings
refer
to the same or like parts.
[031] Aspects of the present invention solve certain problems in the art by
providing
a system, method, and computer implemented method for determining and
implementing a driving strategy of a train including a locomotive consist and
a
plurality of railcars, by monitoring and controlling (either directly or
through
suggested operator actions) a train's operations to improve certain objective
operating
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parameters while satisfying schedule and speed constraints. The embodiments of
the
present invention are also applicable to a train including a plurality of
locomotive
consists, referred to as a distributed power train.
10321 Persons skilled in the art will recognize that an apparatus, such as a
data
processing system, including a CPU, memory, I/O, program storage, a connecting
bus, and other appropriate components, could be programmed or otherwise
designed
to facilitate the practice of the methods of the invention embodiments. Such a
system
would include appropriate program means for executing the methods of the
invention.
[0331 In another embodiment, an article of manufacture, such as a pre-recorded
disk
or other similar computer program product, for use with a data processing
system,
includes a storage medium and a program recorded thereon for directing the
data
processing system to facilitate the practice of the methods of the invention.
Such
apparatus and articles of manufacture also fall within the spirit and scope of
the
embodiments of the invention.
10341 Broadly speaking, the embodiments of the invention teachs a method,
apparatus, and program for determining and implementing a driving strategy of
a train
to improve certain objective operating parameters while satisfying schedule
and speed
constraints. To facilitate an understanding of the present inventions, it is
described
hereinafter with reference to specific implementations thereof. The
embodiments are
described in the general context of computer-executable instructions, such as
program
modules, executed by a computer. Generally, program modules include routines,
programs, objects, components, data structures, etc. that perform particular
tasks or
implement particular abstract data types. For example, the software programs
that
underlie the invention embodiments can be coded in different languages, for
use with
different processing platforms. In the description that follows, examples of
the
embodiments of the invention are described in the context of a web portal that
employs a web browser. It will be appreciated, however, that the principles
that
underlie these embodiments can be implemented with other types of computer
software technologies as well.
[035] Moreover, those skilled in the art will appreciate that the inventions
may be
practiced with other computer system configurations, including hand-held
devices,
multiprocessor systems, microprocessor-based or programmable consumer
electronics, minicomputers, mainframe computers, and the like. The inventions
may
also be practiced in a distributed computing environment where tasks are
perfornied
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by remote processing devices that are linked through a communications network.
In
the distributed computing environment, program modules may be located in both
local and remote computer storage media including memory storage devices.
These
local and remote computing environments may be contained entirely within the
locomotive, or within adjacent locomotives in consist or off-board in wayside
or
central offices where wireless communications are provided between the
computing
environments.
10361 The term locomotive consist means one or more locomotives in succession,
connected together so as to provide motoring and/or braking capability with no
railcars between the locomotives, such as the locomotive consists 12A, 12B and
12C
of FIG. 1. A train may comprise one or more locomotive consists such as the
locomotive consist 12A, 12B and 12C. Specifically, there may be a lead consist
(such
as the consist 12A) and one or more remote consists, such as a first remote
consist
(such as the remote consist 12B) midway along the line of railcars and another
remote
consist (such as the remote consist 12C) at an end-of-train position. Each
locomotive
consist may have a first or lead locomotive (such as the lead unit locomotive
14 of the
consist 12A and the lead unit locomotive 16 of the remote consist 12B) and one
or
more trailing locomotives (such as the locomotive 15 of the consist 12A and
the
locomotive 17 of the remote consist [037] Though a consist is usually
considered as
connected successive locomotives, those skilled in the art will readily
recognize that a
group of locomotives may also be recognized as a consist even with at least
one
railcar separating the locomotives, such as when the consist is configured for
distributed power operation, as described above, wherein throttle and braking
commands are relayed from the lead locomotive to the remote locomotives by the
communications system 10. Towards this end, the term locomotive consist should
be
not be considered a limiting factor when discussing multiple locomotives
within the
same train.
10381 Referring now to the drawings, embodiments of the present invention will
be
described. These embodiments can be implemented in numerous ways, including as
a
system (including a computer processing system), a method (including a
computerized method), an apparatus, a computer readable medium, a computer
program product, a graphical user interface, including a web portal, or a data
structure
tangibly fixed in a computer readable memory. Several embodiments of the
invention
are discussed below.
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10391 FIG. 3 depicts an exemplary illustration of a flow chart of one
embodiment of
the present invention. As illustrated, instructions are input specific to
planning a trip
either on board or from a remote location, such as a dispatch center 110. Such
input
information includes, but is not limited to, train position, consist
composition (such as
locomotive models), locomotive tractive power performance of locomotive
traction
transmission, consumption of engine fuel as a function of output power,
cooling
characteristics, intended trip route (effective track grade and curvature as
function of
milepost or an "effective grade" component to reflect curvature, following
standard
railroad practices), car makeup and loading (including effective drag
coefficients),
desired trip parameters including, but not limited to, start time and
location, end
location, travel time, crew (user and/or operator) identification, crew shift
expiration
time and trip route.
10401 This data may be provided to the locomotive 142 (see FIG. 3) according
to
various techniques and processes, such as, but not limited to, manual operator
entry
into the locomotive 142 via an onboard display, linking to a data storage
device such
as a hard card, hard drive and/or USB drive or transmitting the information
via a
wireless communications channel from a central or wayside location 141, such
as a
track signaling device and/or a wayside device, to the locomotive 142.
Locomotive
142 and train 131 load characteristics (e.g., drag ) may also change over the
route
(e.g., with altitude, ambient temperature and condition of the rails and rail-
cars),
causing a plan update to reflect such changes according to any of the methods
discussed above. The updated data that affects the trip optimization process
can be
supplied by any of the methods and techniques described above and/or by real-
time
autonomous collection of locomotive/train conditions. Such updates include,
for
example, changes in locomotive or train characteristics detected by monitoring
equipment on or off board the locomotive(s) 142.
[0411 A track signal system indicates certain track conditions and provides
instructions to the operator of a train approaching the signal. The signaling
system,
which is described in greater detail below, indicates, for example, an
allowable train
speed over a segment of track and provides stop and run instructions to the
train
operator. Details of the signal system, including the location of the signals
and the
rules associated with different signals are stored in the onboard database 163
(see FIG
9).
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[042] Based on the specification data input into the various embodiments of
the
present invention, an optimal trip plan that minimizes fuel use and/or
generated
emissions subject to speed limit constraints and a desired start and end time
is
computed to produce a trip profile 112. The profile contains the optimal speed
and
power (notch) settings for the train to follow, expressed as a function of
distance
and/or time from the beginning of the trip, train operating limits, including
but not
limited to, the maximum notch power and brake settings, speed limits as a
function of
location and the expected fuel used and emissions generated. In an exemplary
embodiment, the value for the notch setting is selected to obtain throttle
change
decisions about once every 10 to 30 seconds.
[043] Those skilled in the art will readily recognize that the throttle change
decisions
may occur at a longer or shorter intervals, if needed and/or desired to follow
an
optimal speed profile. In a broader sense, it should be evident to ones
skilled in the
art that the profiles provide power settings for the train, either at the
train level,
consist level and/or individual locomotive level. As used herein, power
comprises
braking power, motoring power and airbrake power. In another preferred
embodiment, instead of operating at the traditional discrete notch power
settings, the
present invention embodiments determine a desired power setting, from a
continuous
range of power settings, to optimize the speed profile. Thus, for example, if
an
optimal profile specifies a notch setting of 6.8, instead of a notch setting
of 7, the
locomotive 142 operates at 6.8. Allowing such intermediate power settings may
provide additional efficiency benefits as described below.
[044] The procedure for computing the optimal profile can include any number
of
methods for computing a power sequence that drives the train 131 to minimize
fuel
and/or emissions subject to locomotive operating and schedule constraints, as
summarized below. In some situations the optimal profile may be sufficiently
similar
to a previously determined profile due to the similarity of train
configurations, route
and environmental conditions. In these cases it may be sufficient to retrieve
the
previously-determined driving trajectory from the database 163 and operate the
train
accordingly.
10451 When a previous plan is not available, methods to compute a new plan
include, but are not limited to, direct calculation of the optimal profile
using
differential equation models that approximate train physics of motion.
According to
this process, a quantitative objective function is determined, commonly the
function
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comprises a weighted sum (integral) of model variables that correspond to a
fuel
consumption rate and emissions generated plus a term to penalize excessive
throttle
variations.
[046] An optimal control formulation is established to minimize the
quantitative
objective function subject to constraints including but not limited to, speed
limits and
minimum and maximum power (throttle) settings. Depending on planning
objectives
at any time, the problem may be setup to minimize fuel subject to constraints
on
emissions and speed limits or to minimize emissions subject to constraints on
fuel use
and arrival time. It is also possible to setup, for example, a goal to
minimize the total
travel time without constraints on total emissions or fuel use where such
relaxation of
constraints is permitted or required for the mission.
10471 Throughout the document exemplary equations and objective functions are
presented for minimizing locomotive fuel consumption. These equations and
functions are for illustration only as other equations and objective functions
can be
employed to optimize fuel consumption or to optimize other locomotive/train
operating parameters.
10481 Mathematically, the problem to be solved may be stated more precisely.
The
basic physics are expressed by:
dx = v; x(0) = 0.0; x(Tr )= D
dt
dv = Te (u, v) - G. (x) - R(v); v(0) = 0.0; v(Tf )= 0.0
dt
where x is the position of the train, v is train velocity, t is time (in
miles, miles per
hour and minutes or hours as appropriate) and u is the notch (throttle)
command input.
Further, D denotes the distance to be traveled, Tf the desired arrival time at
distance D
along the track, Te is the tractive effort produced by the locomotive consist,
Ga is the
gravitational drag (which depends on train length, train makeup and travel
terrain) and
R is the net speed dependent drag of the locomotive consist and train
combination.
The initial and final speeds can also be specified, but without loss of
generality are
taken to be zero here (train stopped at beginning and end of the trip). The
model is
readily modified to include other dynamics factors such the lag between a
change in
throttle u and a resulting tractive or braking effort.
[049] All these performance measures can be expressed as a linear combination
of
any of the following:
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TI
min fF(u(t))dt - Minimize total fuel consumption
u(t) 0
min T. - Minimize Travel Time
n(r)
nd
min (u; - u;_, )2 - Minimize notch jockeying (piecewise constant input)
n,
r=i
Tf
min f(du / dt)2 dt - Minimize notch jockeying (continuous input)
n(t)
0
10501 Replace the fuel term F(=) in (1) with a term corresponding to emissions
production. A commonly used and representative objective function is thus
Tf Tf
min a, f F(u(t))dt + a3T f+ a2 f(du / dt)2 dt (OP)
n(t) 0 0
The coefficients of the linear combination depend on the importance (weight)
given to each of
the terms. Note that in equation (OP), u(t) is the optimizing variable that is
the continuous
notch position. If discrete notch is required, e.g. for older locomotives, the
solution to
equation (OP) is discretized, which may result in lower fuel savings. Finding
a minimum
time solution (a, set to zero and a2 set to zero or a relatively small value)
is used to find a
lower bound for the achievable travel time (Tf = Tfiõiõ). In this case, both
u(t) and Tf are
optimizing variables. The preferred embodiment solvzs the equation (OP) for
various values
of Tf with Tf > Tfm;,, with a3 set to zero. In this latter case, T f is
treated as a constraint.
[0511 For those familiar with solutions to such optimal problems, it may be
necessary to adjoin constraints, e.g. the speed limits along the path :
05v<_SL(x)
or when using minimum time as the objective, the adjoin constraint may be that
an
end point constraint must hold, e.g. total fuel consumed must be less than
what is in
the tank, e.g. via:
T,
0 < fF(u(t))dt 5 WF.
0
where WF is the fuel remaining in the tank at Tf. Those skilled in the art
will readily
recognize that equation (OP) can presented in other forms and that the version
above
is an exemplary equation for use in the embodiments of the present invention.
[052] Reference to emissions in the context of the embodiments of the present
invention is generally directed to cumulative emissions produced in the form
of
oxides of nitrogen (NOx), unburned hydrocarbons and particulates. By design,
every
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locomotive must be compliant with EPA emission standards, and thus in an
embodiment of the present invention that optimizes emissions this may refer to
mission-total emissions, for which there is no current EPA specification.
Operation of
the locomotive according to the optimized trip plan is at all times compliant
with EPA
emission standards.
[053] If a key objective during a trip is to reduce emissions, the optimal
control
formulation, equation (OP), is amended to consider this trip objective. A key
flexibility in the optimization process is that any or all of the trip
objectives can vary
by geographic region or mission. For example, for a high priority train,
minimum
time may be the only objective on one route because of the train's priority.
In another
example emission output could vary from state to state along the planned train
route.
[054] To solve the resulting optimization problem, in an exemplary embodiment
the
present invention transcribes a dynamic optimal control problem in the time
domain
to an equivalent static mathematical programming problem with N decision
variables,
where the number 'N' depends on the frequency at which throttle and braking
adjustments are made and the duration of the trip. For typical problems, this
N can be
in the thousands. In an exemplary embodiment a train is traveling a 172-mile
stretch
of track in the southwest United States. Utilizing certain aspects of the
present
invention, an exemplary 7.6% fuel consumption may be realized when comparing a
trip determined and followed using the present features of the inventions
versus a trip
where the throttle/speed is determined by the operator according to standard
practices.
The improved savings is realized because the optimization provided by the
present
invention produces a driving strategy with both less drag loss and little or
no braking
loss compared to the operator controlled trip.
10551 To make the optimization described above computationally tractable, a
simplified model of the train may be employed, such as illustrated in FIG. 4
and set
forth in the equations discussed above. A key refinement to the optimal
profile is
produced by deriving a more detailed model with the optimal power sequence
generated, to test if any thermal, electrical and mechanical constraints are
violated,
leading to a modified profile with speed versus distance that is closest to a
run that
can be achieved without damaging the locomotive or train equipment, i.e.
satisfying
additional implied constraints such thermal and electrical limits on the
locomotive and
in-train forces.
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[056] Referring back to FIG. 3, once the trip is started 112, power commands
are
generated 114 to put the start the plan. Depending on the operational set-up
of the
various embodiments of the present invention, one command causes the
locomotive to
follow the optimized power command 116 so as to achieve optimal speed.
According
to its various embodiments, the present invention obtains actual speed and
power
information from the locomotive consist of the train 118. Due to the common
approximations in the models used for the optimization, a closed-loop
calculation of
corrections to the optimized power is obtained to track the desired optimal
speed.
Such corrections of train operating limits can be made automatically or by the
operator, who always has ultimate control of the train.
10571 In some cases, the model used in the optimization may differ
significantly
from the actual train. This can occur for many reasons, including but not
limited to,
extra cargo pickups or setouts, locomotives that fail in-route, errors in the
initial
database 163 and data entry errors by the operator. For these reasons a
monitoring
system uses real-time train data to estimate locomotive and/or train
parameters in real
time 120. The estimated parameters are then compared to the assumed parameters
when the trip was initially created 122. Based on any differences in the
assumed and
estimated values, the trip may be re-planned 124. Typically the trip is re-
planned if
significant savings can be realized from a new plan.
[058] Other reasons a trip may be re-planned include directives from a remote
location, such as dispatch, and/or an operator request of a change in
objectives to be
consistent with global movement planning objectives. Such global movement
planning objectives may include, but are not limited to, other train
schedules, time
required to dissipate exhaust from a tunnel, maintenance operations, etc.
Another
reason may be due to an onboard failure of a component. Strategies for re-
planning
may be grouped into incremental and major adjustments depending on the
severity of
the disruption, as discussed in more detail below. In general, a "new" plan
must be
derived from a solution to the optimization problem equation (OP) described
above,
but frequently faster approximate solutions can be found, as described herein.
[059] In operation, the locomotive 142 will continuously monitor system
efficiency
and continuously update the trip plan based on the actual measured efficiency
whenever such an update may improve trip performance. Re-planning computations
may be carried out entirely within the locomotive(s) or fully or partially
performed at
a remote location, such as dispatch or wayside processing facilities where
wireless
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technology can communicate the new plan to the locomotive 142. The various
embodiments of the present invention may also generate efficiency trends for
developing locomotive fleet data regarding efficiency transfer functions. The
fleet-
wide data may be used when determining the initial trip plan, and may be used
for
network-wide optimization tradeoff when considering locations of a plurality
of
trains. For example, the travel-time fuel-use tradeoff curve as illustrated in
FIG. 6
reflects a capability of a train on a particular route at a current time,
updated from
ensemble averages collected for many similar trains on the same route. Thus, a
central
dispatch facility collecting curves like FIG. 6 from many locomotives could
use that
information to better coordinate overall train movements to achieve a system-
wide
advantage in fuel use or throughput.
10601 Many events during daily operations may motivate the generation of a new
or
modified plan, including a new or modified trip plan that retains the same
trip
objectives, for example, when a train is not on schedule for a planned meet or
pass
with another train and therefore must make up the lost time. Using the actual
speed,
power and location of the locomotive, a planned arrival time is compared with
a
currently estimated (predicted) arrival time 25. Based on a difference in the
times, as
well as the difference in parameters (detected or changed by dispatch or the
operator)
the plan is adjusted 126. This adjustment may be made automatically responsive
to a
railroad company's policy for handling departures from plan or manually as the
on-
board operator and dispatcher jointly decide the best approach for returning
the plan.
Whenever a plan is updated but where the original objectives, such as but not
limited
to arrival time remain the same, additional changes may be factored in
concurrently,
e.g. new future speed limit changes, which could affect the feasibility of
recovering
the original plan. In such instances if the original trip plan cannot be
maintained, or in
other words the train is unable to meet the original trip plan objectives, as
discussed
herein other trip plan(s) may be presented to the operator, remote facility
and/or
dispatch.
(0611 A re-plan may also be made when it is desired to change the original
objectives. Such re-planning can be done at either fixed preplanned times,
manually
at the discretion of the operator or dispatcher or autonomously when
predefined
limits, such a train operating limits, are exceeded. For example, if the
current plan
execution is running late by more than a specified threshold, such as thirty
minutes,
the embodiments of the invention can re-plan the trip to accommodate the delay
at the
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expense of increased fuel consumption as described above or to alert the
operator and
dispatcher as to the extent to which lost time can be regained, if at all,
(i.e. what is the
minimum time remaining or the maximum fuel that can be saved within a time
constraint). Other triggers for re-plan can also be envisioned based on fuel
consumed
or the health of the power consist, including but not limited time of arrival,
loss of
horsepower due to equipment failure and/or equipment temporary malfunction
(such
as operating too hot or too cold), and/or detection of gross setup errors,
such in the
assumed train load. That is, if the change reflects impairment in the
locomotive
performance for the current trip, these may be factored into the models and/or
equations used in the optimization process.
[062] Changes in plan objectives can also arise from a need to coordinate
events
where the plan for one train compromises the ability of another train to meet
objectives and arbitration at a different level, e.g. the dispatch office, is
required. For
example, the coordination of meets and passes may be further optimized through
train-to-train communications. Thus, as an example, if an operator knows he is
behind schedule in reaching a location for a meet and/or pass, communications
from
the other train can advise the operator of the late train (and/or dispatch).
The operator
can enter information pertaining to the expected late arrival for
recalculating the
train's trip plan. According to various embodiments, the present invention can
also be
used at a high level or network-level, to allow a dispatch to determine which
train
should slow down or speed up should it appear that a scheduled meet and/or
pass time
constraint may not be met. As discussed herein, this is accomplished by trains
transmitting data to dispatch to prioritize how each train should change its
planning
objective. A choice can be made either based on schedule or fuel saving
benefits,
depending on the situation.
10631 For any of the manually or automatically initiated re-plans, the
invention may
present more than one trip plan to the operator. In an exemplary embodiment
the
present invention presents different profiles to the operator, allowing the
operator to
select the arrival time and also understand the corresponding fuel and/or
emission
impact. Such information can also be provided to the dispatch for similar
considerations, either as a simple list of alternatives or as a plurality of
tradeoff curves
such as illustrated in FIG. 6.
10641 In one embodiment the present invention includes the ability to learn
and
adapt to key changes in the train and power consist that can be incorporated
either in
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the current plan and/or for future plans. For example, one of the triggers
discussed
above is loss of horsepower. When building up horsepower over time, either
after a
loss of horsepower or when beginning a tnip, transition logic is utilized to
determine
when a desired horsepower is achieved. This information can be saved in the
locomotive database 161 for use in optimizing either future trips or the
current trip
should loss of horsepower occur again later.
10651 FIG. 5 depicts an exemplary embodiment of elements of the present
invention.
A locator element 130 determines a location of the train 131. The locator
element 130
comprises a GPS sensor or a system of sensors that determine a location of the
train
131. Examples of such other systems may include, but are not limited to,
wayside
devices, such as radio frequency automatic equipment identification (RF AEI)
tags,
dispatch, and/or video-based determinations. Another system may use
tachometer(s)
aboard a locomotive and distance calculations from a reference point. As
discussed
previously, a wireless communication system 147 may also be provided to allow
communications between trains and/or with a remote location, such as dispatch.
Information about travel locations may also be transferred from other trains
over the
communications system.
[066] A track characterization element 133 provides information about a track,
principally grade, elevation and curvature information. The track
characterization
element 133 may include an on-board track integrity database 136. Sensors 138
measure a tractive effort 140 applied by the locomotive consist 142, throttle
setting of
the locomotive consist 142, locomotive consist 142 configuration information,
speed
of the locomotive consist 142, individual locomotive configuration
information,
individual locomotive capability, etc. In an exemplary embodiment the
locomotive
consist 142 configuration information may be loaded without the use of a
sensor 138,
but is input by other approaches as discussed above. Furthermore, the health
of the
locomotives in the consist may also be considered. For example, if one
locomotive in
the consist is unable to operate above power notch level 5 this information is
used
when optimizing the trip plan.
[067] Information from the locator element may also be used to determine an
appropriate arrival time of the train 131. For example, if there is a train 31
moving
along a track 134 toward a destination and no train is following behind it,
and the
train has no fixed arrival deadline to satisfy, the locator element, including
but not
limited to radio frequency automatic equipment identification (RF AEI) tags,
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dispatch, and/or video-based determinations, may be used to determine the
exact
location of the train 131. Furthermore, inputs from these signaling systems
may be
used to adjust the train speed. Using the on-board track database, discussed
below,
and the locator element, such as GPS, embodiments of the invention can adjust
the
operator interface to reflect the signaling system state at the given
locomotive
location. In a situation where signal states indicate restrictive speeds
ahead, the
planner may elect to slow the train to conserve fuel consumption.
[068] Information from the locator element 130 may also be used to change
planning
objectives as a function of distance to a destination. For example, owing to
inevitable
uncertainties about congestion along the route, "faster" time objectives on
the early
part of a route may be employed as hedge against delays that statistically
occur later.
If on a particular trip such delays do not occur, the objectives on a latter
part of the
journey can be modified to exploit the built-in slack time that was banked
earlier and
thereby recover some fuel efficiency. A similar strategy can be invoked with
respect
to emission-restrictive objectives, e.g. emissions constraints that apply when
approaching an urban area.
10691 As an example of the hedging strategy, if a trip is planned from New
York to
Chicago, the system may provide an option to operate the train slower at
either the
beginning of the trip, at the middle of the trip or at the end of the trip.
The
embodiments of the present invention optimize the trip plan to allow for
slower
operation at the end of the trip since unknown constraints, such as but not
limited to
weather conditions, track maintenance, etc., may develop and become known
during
the trip. As another consideration, if traditionally congested areas are
known, the plan
is developed with an option to increase the driving flexibility around such
regions.
Therefore, in one embodiment the present invention may also consider
weighting/penalizing as a function of time/distance into the future and/or
based on
known/past experiences. Those skilled in the art will readily recognize that
such
planning and re-planning to take into consideration weather conditions, track
conditions, other trains on the track, etc., may be considered at any time
during the
trip wherein the trip plan is adjusted accordingly.
[070] FIG. 5 further discloses other elements that may be part of an
embodiment of
the present invention. A processor 144 operates to receive information from
the
locator element 130, track characterizing element 133 and sensors 138. An
algorithm
146 operates within the processor 144. The algorithm 146 computes an optimized
trip
17
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plan based on parameters involving the locomotive 142, train 131, track 134,
and
objectives of the mission as described herein. In an exemplary embodiment the
trip
plan is established based on models for train behavior as the train 131 moves
along
the track 134 as a solution of non-linear differential equations derived from
applicable
physics with simplifying assumptions that are provided in the algorithm. The
algorithm 146 has access to the information from the locator element 130,
track
characterizing element 133 and/or sensors 138 to create a trip plan minimizing
fuel
consumption of a locomotive consist 142, minimizing emissions of a locomotive
consist 142, establishing a desired trip time, and/or ensuring proper crew
operating
time aboard the locomotive consist 42. In an exemplary embodiment, a driver or
controller element, 151 is also provided. As discussed herein the controller
element
151 may control the train as it follows the trip plan. In an exemplary
embodiment
discussed further herein, the controller element 151 makes train operating
decisions
autonomously. In another exemplary embodiment the operator may be involved
with
directing the train to follow or deviate from the trip plan in his discretion.
[071] In one embodiment of the present invention the trip plan is modifiable
in real
time as the plan is being executed. This includes creating the initial plan
for a long
distance trip, owing to the complexity of the plan optimization algorithm.
When a
total length of a trip profile exceeds a given distance, an algorithm 46 may
be used to
segment the mission by dividing the mission into waypoints. Though only a
single
algorithm 146 is discussed, those skilled in the art will readily recognize
that more
than one algorithm may be used and that such multiple algorithms are linked to
create
the trip plan.
[072] The trip waypoints may include natural locations where the train 131
stops,
such as, but not limited to, single mainline sidings for a meet with opposing
traffic or
for a pass with a train behind the current train, a yard siding, an industrial
spur where
cars are picked up and set out and locations of planned maintenance work. At
such
waypoints the train 131 may be required to be at the location at a scheduled
time,
stopped or moving with speed in a specified range. The time duration from
arrival to
departure at waypoints is called dwell time.
10731 In an exemplary embodiment, the present invention is able to break down
a
longer trip into smaller segments according to a systematic process. Each
segment
can be somewhat arbitrary in length, but is typically picked at a natural
location such
as a stop or significant speed restriction, or at key waypoints or mileposts
that define
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junctions with other routes. Given a partition or segment selected in this
way, a
driving profile is created for each segment of track as a function of travel
time taken
as an independent variable, such as shown in FIG. 6. The fuel used/travel-time
tradeoff associated with each segment can be computed prior to the train 131
reaching
that segment of track. A total trip plan can therefore be created from the
driving
profiles created for each segment. In one embodiment the invention optimally
distributes travel time among all segments of the trip so that the total trip
time
required is satisfied and total fuel consumed over all the segments is
minimized. An
exemplary three segment trip is disclosed in FIG. 8 and discussed below. Those
skilled in the art will recognize however, though segments are discussed, the
trip plan
may comprise a single segment representing the complete trip.
[074] FIG. 6 depicts an exemplary embodiment of a fuel-use/travel time curve.
As
mentioned previously, such a curve 150 is created when calculating an optimal
trip
profile for various travel times for each segment. That is, for a given travel
time 151,
fuel used 152 is the result of a detailed driving profile computed as
described above.
Once travel times for each segment are allocated, a power/speed plan is
determined
for each segment from the previously computed solutions. If there are any
waypoint
speed constraints between the segments, such as, but not limited to, a change
in a
speed limit, they are matched during creation of the optimal trip profile. If
speed
restrictions change only within a single segment, the fuel use/travel-time
curve 150
has to be re-computed for only the segment changed. This process reduces the
time
required for re-calculating more parts, or segments, of the trip. If the
locomotive
consist or train changes significantly along the route, e.g. loss of a
locomotive or
pickup or set-out of railcars, then driving profiles for all subsequent
segments must be
recomputed creating new instances of the curve 150. These new curves 150 are
then
used along with new schedule objectives to plan the remaining trip.
10751 Once a trip plan is created as discussed above, a trajectory of speed
and power
versus distance allows the train to reach a destination with minimum fuel
and/or
emissions at the required trip time. There are several techniques for
executing the trip
plan. As provided below in more detail, in one exemplary embodiment of a
coaching
mode, the present invention displays control information to the operator. The
operator follows the information to achieve the required power and speed as
determined according to the optimal trip plan. Thus in this mode the operator
is
provided with operating suggestions for use in driving the train. In another
exemplary
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embodiment, control actions to accelerate the train or maintain a constant
speed are
performed by the present invention. However, when the train 131 must be
slowed,
the operator is responsible for applying brakes by controlling a braking
system 152.
In another exemplary embodiment, the present invention commands power and
braking actions as required to follow the desired speed-distance path.
10761 Feedback control strategies are used to correct the power control
sequence in
the profile to account for such events as, but not limited to, train load
variations
caused by fluctuating head winds and/or tail winds. Another such error may be
caused by an error in train parameters, such as, but not limited to, train
mass and/or
drag, as compared with assumptions in the optimized trip plan. A third type of
error
may occur due to incorrect information in the track database 136. Another
possible
error may involve un-modeled performance differences due to the locomotive
engine,
traction motor thermal deration and/or other factors. Feedback control
strategies
compare the actual speed as a function of position with the speed in the
desired
optimal profile. Based on this difference, a correction to the optimal power
profile is
added to drive the actual velocity toward the optimal profile. To assure
stable
regulation, a compensation algorithm may be provided that filters the feedback
speeds
into power corrections to assure closed-loop performance stability.
Compensation
may include standard dynamic compensation as used by those skilled in the art
of
control system design to meet performance objectives.
10771 The embodiments of the invention allow the simplest and therefore
fastest
means to accommodate changes in trip objectives, which is the rule rather than
the
exception in railroad operations. In an exemplary embodiment, to determine the
fuel-
optimal trip from point A to point B where there are stops along the way, and
for
updating the trip for the remainder of the trip once the trip has begun, a sub-
optimal
decomposition method can be used for finding an optimal trip profile. Using
modeling methods, the computation method can find the trip plan with specified
travel time and initial and final speeds to satisfy all the speed limits and
locomotive
capability constraints when there are stops. Though the following discussion
is
directed to optimizing fuel use, it can also be applied to optimize other
factors, such
as, but not limited to, emissions, schedule, crew comfort and load impact. The
method may be used at the outset in developing a trip plan, and more
importantly to
adapting to changes in objectives after initiating a trip.
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10781 As discussed herein, aspects of the invention may employ a setup as
illustrated
in the exemplary flow chart depicted in FIG. 7 and as an exemplary three
segment
example depicted in detail in FIGS. 8. As illustrated, the trip may be broken
into two
or more segments, T1, T2, and T3, though as discussed herein, it is possible
to
consider the trip as a single segment. As discussed herein, the segment
boundaries
may not result in equal-length segments. Instead the segments use natural or
mission
specific boundaries. Optimal trip plans are pre-computed for each segment. If
fuel
use versus trip time is the trip object to be met, fuel versus trip time
curves are
generated for each segment. As discussed herein, the curves may be based on
other
factors wherein the factors are objectives to be met with a trip plan. When
trip time is
the parameter being determined, trip time for each segment is computed while
satisfying the overall trip time constraints.
[079] FIG. 8 illustrates speed limits for an exemplary three segment 200 mile
trip
197. Further illustrated are grade changes over the 200 mile trip 198. A
combined
chart 199 illustrating curves of fuel used for each segment of the trip over
the travel
time is also shown.
[080] Using the optimal control setup described previously, the present
computation
method can find the trip plan with specified travel time and initial and final
speeds, to
satisfy all the speed limits and locomotive capability constraints when there
are stops.
Though the following detailed discussion is directed to optimizing fuel use,
it can also
be applied to optimize other factors as discussed herein, such as, but not
limited to,
emissions. The method can accommodate desired dwell times at stops and
considers
constraints on earliest arrival and departure at a location as may be
required, for
example, in single-track operations where the time to enter or pass a siding
is critical.
[081] Embodiments of the present invention find a fuel-optimal trip from
distance
Do to DM, traveled in time T, with M-1 intermediate stops at D1,...,DM_,, and
with the
arrival and departure times at these stops constrained by
tmin (i) ~ tarr (Di ) ~ tmax (i) - Ot;
tarr \Di )+ At, C t d e p (Di ) ~ tmax (1) l M - I
where t,rr (D; ), tdep (D; ), and At, are the arrival, departure, and minimum
stop time
at the i'h stop, respectively. Assuming that fuel-optimality implies
minimizing stop
time, therefore tdep (D; ) = tarr (D; ) + Ot; which eliminates the second
inequality above.
Suppose for each i= 1,...,M, the fuel-optimal trip from Di_i to Di for travel
time t,
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T in (i) <_ t<- Tmax (i) , is known. Let F(t) be the fuel-use corresponding to
this trip. If
the travel time from D,j_I to D.j is denoted T, then the arrival time at Di is
given by
i
tarr lDi ) - 1 lT . + Otj_l )
j 1
where Oto is defined to be zero. The fuel-optimal trip from Do to DM for
travel time T
is then obtained by finding Ti, i=1,...,M, which minimizes
M
Fi (Tr ) Tmin (1) ~ Ti C Tmax \I)
i=1
subject to
tmin (1) :!~1(L ~+ Atj_I ):!~tmax (l) - Ati 1= l,..., M- l
j=1
M
1 (T. +Otj_1) = T
J=I
10821 Once a trip is underway, the issue is re-determining the fuel-optimal
solution
for the remainder of the trip (originally from Do to D,u in time T) as the
trip is
traveled, but where disturbances preclude following the fuel-optimal solution.
Let the
current distance and speed be x and v, respectively, where D;_, < x<- Di.
Also, let the
current time since the beginning of the trip be ta,t. Then the fuel-optimal
solution for
the remainder of the trip from x to DM, which retains the original arrival
time at DM, is
obtained by finding T , . , T j, j i+ 1,...M , which minimizes
M
F(T.,x,v)+ I FF.(Tj)
j=i+t
subject to
tmin (i) ~ G, + T. 5 tmax At,
7~ k
tmin (K ) C tac.t + T +L' (T + Atj_1 tmax (k) - Atk k = 1+ 1,..., M - I
j=i+l
M
tact + T + I (Tj + Atj-l ) = T
j=i+l
Here, F. (t, x, v) is the fuel-used of the optimal trip from x to D;, traveled
in time t,
with initial speed at x of v.
[083] As discussed above, an exemplary process to enable more efficient re-
planning constructs the optimal solution for a stop-to-stop trip from
partitioned
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segments. For the trip from Di_1 to D;, with travel time T;, choose a set of
intermediate
points Dij, j=1,..., N; -1. Let D,o = Di_1 and D,N, = D; . Then express the
fuel-use for
the optimal trip from D;_1 to D; as
N;
Fi (t) _ I -f7 (tii - t+,i-1 9 Vi,l-1 9 vt~ )
j=1
where fIy(t, v; j_l , vY) is the fuel-use for the optimal trip from D;j_t to
Du,
traveled in time t, with initial and final speeds ofv,,;_l and v,,.
Furthermore, t;; is the
time in the optimal trip corresponding to distance D. By definition, t,N, -
t;p = T,. .
Since the train is stopped at D;o and D;N, , v,o = v;N; = 0.
[084] The above expression enables the function F,(t) to be alternatively
determined
by first determining the functions fjj(=),1 <_ j<_ N; , then finding zj,1 <_
j<_ N; and
v;~ ,1 <_ j < N; , that minimize
N;
F (t) _ I fi (zj, v=,;-l, vj)
i=1
subject to
N;
y z, = T
;-1
Vmin 09 A ~ Vrj !~ Vmax 01 j) i - 1,..., NJ - 1
V;o = V;N = 0
10851 By choosing D; (e.g., at speed restrictions or meeting points),
Vmax 01 j) - Vmin 0, j) can be minimized, thus minimizing the domain over
which f,{)
needs to be known.
10861 Based on the partitioning described above, a simpler suboptimal re-
planning
approach than that described above restricts re-planning to times when the
train is at
distance points D, ,1 < i 5 M,15 j 5 N; . At point D;f, the new optimal trip
from D;~
to DM can be determined by fmding r;k, j< k 5 N; , va, j< k< N;
and
r,,,,,,i<m<_M,1<_n<_Nm,Vmn,i<m<_M,1<_n<Nm,whichminimize
N, ~' M N~,
~j/ik(Zik9Vi,k-lIVik)+ 2: ~jJmnlzmn~Vm,n-IVmn)
k=1+1 m=i+1 n=1
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subject to
N;
tmin (Z) ~ tact +I Zik C tmax (l) - Oti
k=j+l
N;
tmin lnl :!~ tact +> Zik +(Tm +Atm-l l C tmax (Yd) Atn n = Z+ 1,..., M- 1
k=j+l m=i+l
N; M
tact + ~j 'rik + 1 (T +Otm-1 ) = T
k=j+l m=i+l
where
T = ~j ~ m n
n=1
[087] A further simplification is obtained by waiting on the re-computation of
Tm , i< m<_ M, until distance point D; is reached. In this way at points D,j
between Di_
1 and Di, the minimization above needs to be performed only over
zik , j< k<_ Ni , vik , j< k< Ni . Ti is increased as needed to accommodate
any longer
actual travel time from Di_I to D,j than planned. This increase is later
compensated, if
possible, by the re-computation of T, i< m<_ M, at distance point Di.
[088] With respect to the closed-loop configuration disclosed above, the total
input
energy required to move a train 131 from point A to point B consists of the
sum of
four components, specifically difference in kinetic energy between the points
A and
B; difference in potential energy between the points A and B; energy loss due
to
friction and other drag losses; and energy dissipated by the application of
the brakes.
Assuming the start and end speeds are equal (e.g., stationary) the first
component is
zero. Furthermore, the second component is independent of driving strategy.
Thus, it
suffices to minimize the sum of the last two components.
[089] Following a constant speed profile minimizes drag loss. Following a
constant
speed profile also minimizes total energy input when braking is not needed to
maintain constant speed. However, if braking is required to maintain constant
speed,
applying braking just to maintain constant speed will most likely increase
total
required energy because of the need to replenish the energy dissipated by the
brakes.
A possibility exists that some braking may actually reduce total energy usage
if the
additional brake loss is more than offset by the resultant decrease in drag
loss caused
by braking, by reducing speed variation.
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[090] After completing a re-plan from the collection of events described
above, the
new optimal notch /speed plan can be followed using the closed loop control
described herein. However, in some situations there may not be enough time to
carry
out the segment-decomposed planning described above, and particularly when
there
are critical speed restrictions that must be respected, an alternative may be
preferred.
Aspects of the present invention accomplish this with an algorithm referred to
as
"smart cruise control". The smart cruise control algorithm is an efficient
process for
generating, on the fly, an energy-efficient (hence fuel-efficient) sub-optimal
prescription for driving the train 131 over a known terrain. This algorithm
assumes
knowledge of the position of the train 131 along the track 134 at all times,
as well as
knowledge of the grade and curvature of the track versus position. The method
relies
on a point-mass model for the motion of the train 131, whose parameters may be
adaptively estimated from online measurements of train motion as described
earlier.
[091] The smart cruise control algorithm has three principal components,
specifically a modified speed limit profile that serves as an energy-efficient
guide
around speed limit reductions; an ideal throttle or dynamic brake setting
profile that
attempts to balance minimizing speed variations and braking; and a mechanism
for
combining the latter two components to produce a notch command, employing a
speed feedback loop to compensate for mismatches of modeled parameters when
compared to reality parameters. Smart cruise control can accommodate
strategies in
the embodiments of the invention without active braking (i.e. the driver is
signaled
and assumed to provide the requisite braking) or a variant that does provide
active
braking.
[092] With respect to the cruise control algorithm that does not control
dynamic
braking, the three exemplary components are a modified speed limit profile
that
serves as an energy-efficient guide around speed limit reductions, a
notification signal
to notify the operator when braking should be activated, an ideal throttle
profile that
attempts to balance minimizing speed variations and notifying the operator to
apply
brakes and a mechanism employing a feedback loop to compensate for mismatches
of
model parameters to reality parameters.
[093] One embodiment of the present invention includes an approach to identify
key
parameter values of the train 131. For example, with respect to estimating
train mass,
a Kalman filter and a recursive least-squares approach may be utilized to
detect errors
that may develop over time.
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10941 FIG. 9 depicts an exemplary flow chart of the present invention. As
discussed
previously, a remote facility, such as a dispatch center 160 can provide
information
for use by the steps of the flow chart. As illustrated, such information is
provided to
an executive control element 162. Also supplied to the executive control
element 162
is a locomotive modeling information database 163, a track information
database 136
such as, but not limited to, track grade information and speed limit
information,
estimated train parameters such as, but not limited to, train weight and drag
coefficients, and fuel rate tables from a fuel rate estimator 164. The
executive control
element 162 supplies information to the planner 112, which is disclosed in
more detail
in FIG. 3. Once a trip plan has been calculated, the plan is supplied to a
driving
advisor, driver or controller element 151. The trip plan is also supplied to
the
executive control element 162 so that it can compare the trip when other new
data is
provided.
[095] As discussed above, the driving advisor 151 can automatically set a
notch
power, either a pre-established notch setting or an optimum continuous notch
power
value. In addition to supplying a speed command to the locomotive 131, a
display
168 is provided so that the operator can view what the planner has
recommended.
The operator also has access to a control panel 169. Through the control panel
169
the operator can decide whether to apply the notch power recommended. Towards
this end, the operator may limit a targeted or recommended power. That is, at
any
time the operator always has final authority over the power setting for
operation of the
locomotive consist, including whether to apply brakes if the trip plan
recommends
slowing the train 131. For example, if operating in dark territory, or where
information from wayside equipment cannot electronically transmit information
to a
train and instead the operator views visual signals from the wayside
equipment, the
operator inputs commands based on information contained in the track database
and
visual signals from the wayside equipment. Based on how the train 131 is
functioning, information regarding fuel measurement is supplied to the fuel
rate
estimator 164. Since direct measurement of fuel flows is not typically
available in a
locomotive consist, all information on fuel consumed to a point in the trip
and
projections into the future if the optimal plans are followed use calibrated
physics
models, such as those used in developing the optimal plans. For example, such
predictions may include, but are not limited to, the use of measured gross
horse-power
and known fuel characteristics to derive the cumulative fuel used.
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10961 The train 131 also has a locator device 130 such as a GPS sensor, as
discussed
above. Information is supplied to the train parameters estimator 165. Such
information may include, but is not limited to, GPS sensor data,
tractive/braking effort
data, braking status data, speed and any changes in speed data. With
information
regarding grade and speed limit information, train weight and drag
coefficients
information is supplied to the executive control element 162.
[097] The embodiments of the present invention may also allow the use of
continuously variable power throughout the optimization planning and closed
loop
control implementation. In a conventional locomotive, power is typically
quantized
to eight discrete levels. Modern locomotives can realize continuous variation
in
horsepower that may be incorporated into the previously described optimization
methods. With continuous power, the locomotive 142 can further optimize
operating
conditions, e.g., by minimizing auxiliary loads and power transmission losses,
and
fine tuning engine horsepower regions of optimum efficiency or to points of
increased
emissions margins. Example include, but are not limited to, minimizing cooling
system losses, adjusting alternator voltages, adjusting engine speeds, and
reducing
number of powered axles. Further, the locomotive 142 may use the on-board
track
database 36 and the forecasted performance requirements to minimize auxiliary
loads
and power transmission losses to provide optimum efficiency for the target
fuel
consumption/emissions. Examples include, but are not limited to, reducing a
number
of powered axles on flat terrain and pre-cooling the locomotive engine prior
to
entering a tunnel.
10981 In one embodiment, the present invention may also use the on-board track
database 136 and the forecasted performance to adjust the locomotive
performance,
such as to ensure that the train has sufficient speed as it approaches a hill
and/or
tunnel. For example, this could be expressed as a speed constraint at a
particular
location that becomes part of the optimal plan generation created solving the
equation
(OP). Additionally, one embodiment may incorporate train-handling rules, such
as,
but not limited to, tractive effort ramp rates and maximum braking effort ramp
rates.
These may incorporated directly into the formulation for optimum trip profile
or
alternatively incorporated into the closed loop regulator used to control
power
application to achieve the target speed.
10991 In a preferred embodiment the present invention is installed only on a
lead
locomotive of the train consist. Even though in one embodiment the present
invention
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is not dependent on data or interactions with other locomotives in the train,
it may be
integrated with a consist manager, as disclosed in U.S. Patent No. 6,691,957
and
Patent Application No. 10/429,596 (both owned by the Assignee and both
incorporated by reference), functionality and/or a consist optimizer
functionality to
improve efficiency. Interaction with multiple trains is not precluded as
illustrated by
the example of dispatch arbitrating two "independently optimized" trains
described
herein.
11001 In a train utilizing a consist manager, the lead locomotive in a
locomotive
consist may operate at a different notch power setting than other locomotives
in that
consist. The other locomotives in the consist operate at the same notch power
setting.
In one embodiment, the present invention may be utilized in conjunction with
the
consist manager to command different notch power settings for the locomotives
in the
consist. Thus based on this embodiment, since the consist manager divides a
locomotive consist into two groups, lead locomotive and trailing units, the
lead
locomotive can be commanded to operate at a certain notch power and the
trailing
locomotives can be commanded to operate at a different notch power, each
trailing
locomotive not necessarily operating at the same notch power.
11011 Likewise, when a consist optimizer is used with a locomotive consist, in
one
embodiment the present invention can be used in conjunction with the consist
optimizer to determine notch power for each locomotive in the locomotive
consist.
For example, suppose that a trip plan recommends a notch power setting of four
for
the locomotive consist. Based on the location of the train, the consist
optimizer can
use this information to determine the notch power setting for each locomotive
in the
consist. In this implementation, the efficiency of setting notch power
settings over
intra-train communication channels is improved. Furthermore, implementation of
this
configuration may be performed utilizing the distributed power communications
system.
11021 An embodiment of the present invention may be used with a distributed
power
train such as illustrated in FIGS. 1 and 2 and described above. Absent the
teachings
of the present inventions, a distributed power train can be operated in a
normal or an
independent mode. In the normal mode, the operator in the lead unit 14 of the
lead
consist 12A commands each of the locomotive consists 12A, 12B and 12C to
operate
at the same notch power or to apply the same braking effort as applied by the
lead
locomotive 14. If the lead locomotive 14 of the lead consist 12A commands
motoring
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at notch N8, all other locomotives 15-18 are commanded to motoring at notch N8
by a
signal transmitted over the communications system 10 from the lead locomotive
14.
[103] In the independent mode, the distributed power train is segregated into
two
independent locomotive consist groups, i.e., a front group and a back group by
the
operator when the communications system is set-up. For example, the locomotive
consist 12A is configured as the front group and the locomotive consists 12B
and 12C
are configured as the back group. Each of the front and back groups can be
commanded to different operation. For example, as the train crests a
mountaintop, the
front group locomotives 14 and 15 in the lead consist 12A (on the downward
slope of
the mountain) are commanded to progressively lower notch settings (including
perhaps a braking setting) as the front group descends the grade. The back
group
locomotives 16, 17 and 18 in the remote consists 12B and 12C (on the upward
slope
of the mountain) remain in a motoring mode until the end of the train crests
the
mountain. The division of the train into front and back groups and
differential control
of the two groups can minimize tensile forces on the mechanical couplers that
connect
the railcars and the locomotives. According to the prior art, operating the
distributed
power train in independent mode requires the operator to manually command the
front
group locomotives and the back group locomotives via a display in the lead
locomotive.
11041 Using the physics based planning model, train set-up information
(including
the performance capabilities and location of each locomotive in the train,
which can
be determined by the operator during set-up or automatically by one embodiment
of
the trip optimizer), on-board track database information, operating rules,
location
determination systems, real-time closed loop power/brake controls, sensor
feedback,
etc. (as described elsewhere herein), one embodiment of the trip optimizer
system of
the present invention determines optimum operation for each locomotive 14-18
to
achieve optimal train operation. Responsive to the optimized trip plan, the
trip
optimizer controls the distributed power train by independently controlling
each
locomotive, whether in the same or a different locomotive consist. Thus the
trip
optimizer, as applied to a distributed power train, provides more granular
train control
and optimizes train performance to the individual locomotive level. Unlike the
prior
art distributed power trains in which the locomotives are segregated and
controlled
according to a front group and a back group, independent trip optimizer
control of the
individual locomotives according to the aspects of the present invention
segregates
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the train into multiple consists (where by electing to group certain
locomotives
together or control each locomotive independently, the number independently
controlled locomotives can include any number up to the total number of
locomotives
in the train). Thus the performance of the train and its individual
locomotives can be
controlled to improve fuel consumption, for example.
[105] The trip optimizer and/or the lead unit operator can command each
individual
locomotive or one or more locomotive consists to operate at different notch
and/or
braking settings to optimize the performance of each individual locomotive. If
desired, of course, all locomotives can be operated at the same notch power or
brake
setting. The notch power or braking settings are communicated over the
distributed
communications system 10 to the remote locomotives 15-18 for execution at each
remote locomotive. Thus application of the trip optimizer concepts to a
distributed
power train allows the train to be segregated into smaller controlled sections
(creating
multiple, individually-controlled but coupled trains) to improve train
operation and
control, including a reduction in in-train forces, simplification of in-train
force
management, improved control over stopping distances and more optimal
performance for each locomotive. Further, longer and/or heavier trains can be
better
and more safely controlled when the locomotives are subject to independent and
individual control.
[106] Since operating parameters of the train are affected by the location of
the
locomotives in the train and the number of railcars between the locomotives,
independent control of the locomotives reduces the affects of these factors on
train
performance and control. The trip optimizer also controls train acceleration
and
deceleration by raising or lowering the notch position of one or more of the
remote
locomotives by suitable commands sent over the communications system 10,
promoting economy, flexibility in train makeup, train force reduction,
increased train
sizes, etc.
[107] Independent locomotive control also offers additional degrees of freedom
for
use by the trip optimizing algorithm. Additional objectives or constraints
relating to
in-train forces can therefore be incorporated into the performance function
for
optimization.
[108] A dynamic brake modem link can also be used to provide the optimized
trip
control information to each locomotive of the train. This link is a serial
high
frequency communications signal imposed on a DC voltage carried by a trainline
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connects the locomotives of the train. The modem carries signals to the
operator in
the lead locomotive that indicate the application of dynamic brakes at one or
more
remote locomotives.
11091 According to this embodiment of the trip optimizer, various train
operating
parameters can be optimized, including fuel consumption, emissions generated,
sand
control, application of tractive and braking efforts and air brake
applications. The
train length, in-train force limits and stopping distances, which are
constrained by the
position and control of the locomotives in the consist and the number of cars
in the
train between locomotives, can also be optimized. The embodiment thus allows
the
railroad to run longer and/or heavier trains and provides better performance
as
measured by costs, such as the cost of fuel and sand. Increased train length
increases
railroad network throughput, without sacrificing train handling
characteristics.
[110] Furthermore, as discussed with respect to other embodiments, the present
inventions as applied to distributed power trains may be used for continuous
corrections and re-planning based on previous or expected railroad crossings,
grade
changes, approaching sidings, approaching depot yards and approaching fuel
stations
where each locomotive in the consist may require a different control
operation. For
example, if the train is coming over a hill, the lead locomotive may enter a
braking
mode whereas the remote locomotives, having not reached the peak of the hill
may
have to remain in a motoring state.
[111] FIGS. 10, 11 and 12 depict exemplary illustrations of dynamic displays
for use
by the operator. FIG. 8 illustrates a provided trip profile 172. Within the
profile a
location 173 of the locomotive is indicated. Such information as train length
205 and
the number of cars 206 in the train is provided. Elements are also provided
regarding
track grade 207, curve and wayside elements 208, including bridge location 209
and
train speed 210. The display 168 allows the operator to view such information
and
also see where the train is along the route. Information pertaining to
distance and/or
estimated time of arrival to such locations as crossings 212, signals 214,
speed
changes 216, landmarks 218 and destinations 220 is provided. An arrival time
management too1225 is also provided to allow the user to determine the fuel
savings
realized during the trip. The operator has the ability to vary arrival times
227 and
witness how this affects the fuel savings. As discussed herein, those skilled
in the art
will recognize that fuel saving is an exemplary example of only one objective
that can
be reviewed with a management tool. Thus, depending on the parameter being
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viewed, other parameters, discussed herein can be viewed and evaluated with a
management tool visible to the operator. The operator is also provided with
information regarding the time duration that the crew has been operating the
train. In
exemplary embodiments time and distance information may either be illustrated
as the
time and/or distance until a particular event and/or location or it may
provide a total
elapsed time.
[112] As illustrated in FIG. 11 an exemplary display provides information
about
consist data 230, an events and situation graphic 232, an arrival time
management tool
234 and action keys 236. Similar information as discussed above is provided in
this
display as well. This display 168 also provides action keys 238 to allow the
operator
to re-plan as well as to disengage 240 the control features of the present
inventions.
11131 FIG. 12 depicts another exemplary embodiment of the display. Typical
information for a modem locomotive including air-brake status 172, analog
speedometer with digital inset 174, and information about tractive effort in
pounds
force (or traction amps for DC locomotives) is visible. An indicator 14 shows
the
current optimal speed in the plan being executed as well as an accelerometer
graphic
to supplement the readout in mph/minute. Important new data for optimal plan
execution is in the center of the screen, including a rolling strip graphic
176 with
optimal speed and notch setting versus distance compared to the current
history of
these variables. In this exemplary embodiment, location of the train is
derived using
the locator element. As illustrated, the location is provided by identifying
how far the
train is away from its final destination, an absolute position, an initial
destination, an
intermediate point and/or an operator input.
11141 The strip chart provides a look-ahead to changes in speed required to
follow
the optimal plan, which is useful in manual control and monitors plan versus
actual
during automatic control. As discussed herein, such as when in the coaching
mode,
the operator can either follow the notch or speed suggested by the embodiments
of the
invention. The vertical bar gives a graphic of desired and actual notch, which
are also
displayed digitally below the strip chart. When continuous notch power is
utilized, as
discussed above, the display will simply round to closest discrete equivalent,
the
display may be an analog display so that an analog equivalent or a percentage
or
actual horse power/tractive effort is displayed.
11151 Critical information on trip status is displayed on the screen, and
shows the
current grade the train is encountering 188, either by the lead locomotive, a
location
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elsewhere along the train or an average over the train length. A cumulative
distance
traveled in the plan 190, cumulative fuel used 192, the location of or the
distance to
the next stop as planned 194 and current and projected arrival time 196 at the
next
stop are also disclosed. The display 168 also shows the maximum possible time
to
destination with the computed plans available. If a later arrival is required,
a re-plan
is executed. Delta plan data shows status for fuel and schedule ahead or
behind the
current optimal plan. Negative numbers mean less fuel or early compared to
plan,
positive numbers mean more fuel or late compared to plan. Typically these
parameters trade-off in opposite directions (slowing down to save fuel makes
the train
late and conversely).
11161 At all times these displays 168 gives the operator a snapshot of the
trip status
with respect to the currently instituted driving plan. This display is for
illustrative
purpose only as there are many other ways of displaying/conveying this
information
to the operator and/or dispatch. Towards this end, any other items of
information
disclosed above can be added to the display to provide a display that is
different than
those disclosed.
[117] Other features that may be included in different embodiments of the
present
invention include, but are not limited to, generating of data logs and
reports. This
information may be stored on the train and downloaded to an off-board system.
The
downloads may occur via manual and/or wireless transmission. This information
may
also be viewable by the operator via the locomotive display. The data may
include
such information as, but not limited to, operator inputs, time system is
operational,
fuel saved, fuel imbalance across locomotives in the train, train journey off
course and
system diagnostic issues, such as a GPS sensor malfunction.
11181 Since trip plans may also take into consideration allowable crew
operation
time, an embodiment of the present invention may take such information into
consideration as a trip is planned. For example, if the maximum time a crew
may
operate is eight hours, then the trip can be fashioned to include stopping
location for a
new crew to replace the present crew. Such specified stopping locations may
include,
but are not limited to rail yards, meet/pass locations, etc. If, as the trip
progresses, the
trip time may be exceeded, the present invention may be overridden by the
operator to
meet other criteria as determined by the operator. Ultimately, regardless of
the
operating conditions of the train, such as but not limited to high load, low
speed, train
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stretch conditions, etc., the operator remains in control to command a safe
speed
and/or operating condition of the train.
11191 Using the aspects of the present invention, the train may operate in a
plurality
of different operational concepts. In one operational concept the present
invention
provides commands for commanding propulsion and dynamic braking. The operator
handles all other train functions. In another operational concept, the present
invention
provides commands for commanding propulsion only. The operator handles dynamic
braking and all other train functions. In yet another operational concept, the
present
invention provides commands for commanding propulsion, dynamic braking and
application of the airbrake. The operator handles all other train functions.
11201 The present inventions may also notify the operator of upcoming items of
interest or actions to be taken, such as forecasting logic of the present
invention, the
continuous corrections and re-planning to the optimized trip plan, the track
database.
The operator can also be notified of upcoming crossings, signals, grade
changes,
brake actions, sidings, rail yards, fuel stations, etc. These notifications
may occur
audibly and/or through the operator interface.
[121] Specifically using the physics based planning model, train set-up
information,
on-board track database, on-board operating rules, location determination
system,
real-time closed loop power/brake control, and sensor feedback, the system
presents
and/or notify the operator of required actions. The notification can be visual
and/or
audible. Examples include notification of crossings that require the operator
to
activate the locomotive horn and/or bell and "silent" crossings that do not
require the
operator to activate the locomotive horn or bell.
[122] In another exemplary embodiment, using the physics based planning model
discussed above, train set-up information, on-board track database, on-board
operating rules, location determination system, real-time closed power/brake
control,
and sensor feedback, the present invention may present the operator
information (e.g.
a gauge on display) that allows the operator to see when the train will arrive
at various
locations, as illustrated in FIG. 11. The system allows the operator to adjust
the trip
plan (target arrival time). This information (actual estimated arrival time or
information needed to derive off-board) can also be communicated to the
dispatch
center to allow the dispatcher or dispatch system to adjust the target arrival
times.
This allows the system to quickly adjust and optimize for the appropriate
target
function (for example trading off speed and fuel usage).
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[123] This written description of the various embodiments of the invention
uses
examples to disclose these embodiments, including the best mode, and also to
enable
any person skilled in the art to make and use the embodiments of the
invention. The
patentable scope of these embodiments are defined by the claims, and may
include
other examples that occur to those skilled in the art. Such other examples are
intended to be within the scope of the claims if they have structural elements
that do
not differ from the literal language of the claims, or if they include
equivalent
structural elements with insubstantial differences from the literal languages
of the
claims. For example, although described in the context of a railroad network
over
which trains comprising locomotives and railcars operate, the teachings of the
invention are also applicable to other railway and rail-based systems and
vehicles
including, but not limited to, interurban trains, people movers, shuttles and
trams.
