U.S. patent application number 12/332066 was filed with the patent office on 2010-01-21 for distributed simulation.
Invention is credited to Juri V. Jatskevich, Charles E. Lucas, Oleg Wasynczuk.
Application Number | 20100017179 12/332066 |
Document ID | / |
Family ID | 22792086 |
Filed Date | 2010-01-21 |
United States Patent
Application |
20100017179 |
Kind Code |
A1 |
Wasynczuk; Oleg ; et
al. |
January 21, 2010 |
DISTRIBUTED SIMULATION
Abstract
A method and apparatus are presented to facilitate simulation of
complex systems on multiple computing devices. Model authors can
specify state-related information to be exported for viewing or
access by other applications and models. Subsystem models may be
written to enable connection with other subsystem models via
controlled interfaces, such as by defining state-related
information for export and providing for a particular use of data
imported from other models to which a subsystem model is connected.
In some embodiments, a consistent distributed simulation API
enables cross-platform, multi-device simulation of complex systems,
wherein the proprietor of each subsystem simulation can keep its
implementation secret but accessible to others.
Inventors: |
Wasynczuk; Oleg; (West
Lafayette, IN) ; Lucas; Charles E.; (Lafayette,
IN) ; Jatskevich; Juri V.; (Vancouver, CA) |
Correspondence
Address: |
WOODARD, EMHARDT, MORIARTY, MCNETT & HENRY LLP
111 MONUMENT CIRCLE, SUITE 3700
INDIANAPOLIS
IN
46204-5137
US
|
Family ID: |
22792086 |
Appl. No.: |
12/332066 |
Filed: |
December 10, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09884528 |
Jun 19, 2001 |
7490029 |
|
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12332066 |
|
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60212695 |
Jun 19, 2000 |
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Current U.S.
Class: |
703/6 ;
709/201 |
Current CPC
Class: |
G06F 9/546 20130101;
G06F 2111/02 20200101; G05B 17/02 20130101; G06F 30/20
20200101 |
Class at
Publication: |
703/6 ;
709/201 |
International
Class: |
G06G 7/48 20060101
G06G007/48 |
Goverment Interests
[0002] This invention was made with Government support under
Contract F33615-99-C-2911 awarded by the U.S. Department of
Defense. The United States Government has certain rights in the
invention.
Claims
1. A computer-implemented method for simulating operation of a
physical system having a plurality of physical subsystems,
comprising: simulating a first physical subsystem with a first
continuous-time simulation on a first physical computing device,
wherein the first continuous-time simulation is a state-space
simulation; accepting a request for export of information relating
to a number n of state-related variables that characterize the
state of the first physical subsystem in the simulating; sending a
first series of state-related messages, each message containing
information relating to the value of at least one of the n
state-related variables; simulating a second physical subsystem
with a second continuous-time simulation on a second physical
computing device; receiving in the second continuous-time
simulation the first series of state-related messages from the
first continuous-time simulation without the first series of
state-related messages passing through a central communication
process; and outputing data representative of a state of the second
continuous-time simulation; wherein: the first physical subsystem
interacts with the second physical subsystem; and the at least one
state-related variable characterizes at least a portion of the
interaction between the first physical subsystem and the second
physical subsystem.
2. A computer-implemented method for simulating operation of a
physical system having a plurality of physical subsystems,
comprising: simulating a first physical subsystem with a first
continuous-time simulation on a first physical computing device,
wherein the simulation of the first physical subsystem with the
first continuous-time simulation uses a first numerical integration
technique; accepting a request for export of information relating
to a number n of state-related variables that characterize the
state of the first physical subsystem in the simulating; sending a
first series of state-related messages, each message containing
information relating to the value of at least one of the n
state-related variables; simulating a second physical subsystem
with a second continuous-time simulation on a second physical
computing device, wherein the simulation of the second physical
subsystem with the second continuous-time simulation uses a second
numerical integration technique; receiving in the second
continuous-time simulation the first series of state-related
messages from the first continuous-time simulation without the
first series of state-related messages passing through a central
communication process; and outputing data representative of a state
of the second continuous-time simulation; wherein: the first
physical subsystem interacts with the second physical subsystem;
and the at least one state-related variable characterizes at least
a portion of the interaction between the first physical subsystem
and the second physical subsystem.
Description
REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of application Ser. No.
09/884,528, filed Jun. 19, 2001, which claims the benefit of U.S.
Provisional Application No. 60/212,695, filed Jun. 19, 2000, which
are hereby incorporated by reference in their entireties.
BACKGROUND
[0003] The present invention relates to computer programs that
simulate systems. More specifically, the present invention relates
to simulation systems using a distributed computer network, wherein
subsystems can be simulated independently, the subsystem
simulations communicating the values of input/output variables to
simulate subsystem interaction. Present methods of simulating
complex systems suffer from limitations in security,
interoperability, cross-platform communication, and other
functional areas. Many simulation platforms fail to enable
distributed simulation at all, limiting the complexity of systems
that can be modeled as a function of the computing and storage
capacity of a single device. Simulation of complex systems (those
of a tank or aircraft, for example) in a reasonable time is
extremely difficult, if not impossible, using widely available
computing systems.
[0004] Furthermore, where multiple vendors are responsible for the
various subsystems of a larger system, security and proprietary
concerns may inhibit or prevent formation of cooperative simulation
systems comprising simulation models of each subsystem provided by
each vendor. In some contractual and/or regulatory scenarios,
vendors may be forced against their preferences to disclose their
simulation models to other vendors or authorities, so that
simulations may be conducted of the whole system.
[0005] There is thus a need for further contributions and
improvements to distributed simulation technology.
SUMMARY
[0006] It is an object of the present invention to provide a novel
simulation system. Another object is to provide a simulation system
in which various subsystem simulations are written in different
languages and executed by different programs running on different
computing devices, yet the subsystem simulations communicate to
simulate operation of the combination of subsystems. Yet another
object is to provide a simulation system in which various parts of
the simulation can be executed using different integration methods
and/or parameters from other parts of the simulation.
[0007] These objects and others are achieved by various forms of
the present invention. One form of the present invention is a
unique distributed simulation system. Further forms include a
system in which a plurality of processors each executes a separate
program to independently simulate a different portion of a physical
system. At various points in time, a first one of the processors
communicates messages to a second one of the processors to convey
information regarding the state of the simulated subsystem at a
particular point in simulation time. The second processor uses the
state-related information from the first processor to execute its
model of the second portion of the system. In some embodiments of
this form, the messages are sent at constant intervals in
simulation time, while in other embodiments messages are sent at
constant intervals in real time. In still other embodiments, the
messages are sent at variable intervals depending on the
circumstances, such as a function of one or more variables, the
pattern of change in one or more variables, detected network
congestion or delay, or the behavior of the other state variables
(in the first model, second model, another model, or a combination
thereof).
[0008] In another form of the invention, one program exposes an
interface associated with a first model, while a second program
exposes an interface associated with a second model. The first
interface permits access by the second program to a
program-controlled set of state-related information of the first
model, while preventing access by the second model to a substantial
portion of the first program or model. In some embodiments of this
form, the second program's interface allows the first model to
access a program-controlled set of state-related information of the
second model, while preventing access by the first model to at
least a substantial portion of the second program or model.
[0009] In yet another form of the invention, a system monitor
application provides control and coordination of subsystem
simulations. In some embodiments of this form, each subsystem model
allows itself to be started, stopped, configured, and/or connected
with other models by the system monitor application. In other
embodiments, a model accepts and serves requests to periodically
transmit certain state-related information to one or more data
output applications, which may produce one or more graphs of those
values (or of a function of those values). In some of these
embodiments, a sequence of values of one or more state-related
variables is broadcast to a plurality of possible recipients.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a block diagram of a distributed simulation
system.
[0011] FIG. 2 is a block diagram of two embodiments of model host
computers in a distributed simulation system.
[0012] FIG. 3 is a block diagram of a system monitor computer and a
model host computer in a distributed simulation system.
[0013] FIG. 4 is a flowchart of a distributed simulation.
[0014] FIG. 5 is a sample view of an OSCOPE application in a
distributed simulation system.
[0015] FIG. 6 is a schematic view of a portion of a distributed
simulation system including a subnetwork arrangement.
[0016] FIGS. 7A-7C are a flowchart of a control message handling
loop for use in some distributed simulation systems.
[0017] FIG. 8 is a sample view of a control panel application in a
distributed simulation system.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] For the purpose of promoting an understanding of the
principles of the present invention, reference will now be made to
the embodiment illustrated in the drawings and specific language
will be used to describe the same. It will, nevertheless, be
understood that no limitation of the scope of the invention is
thereby intended; any alterations and further modifications of the
described or illustrated embodiments, and any further applications
of the principles of the invention as illustrated therein are
contemplated as would normally occur to one skilled in the art to
which the invention relates.
[0019] Generally, the distributed simulation system illustrated in
FIGS. 1-3 provides parallel implementations of various portions or
aspects ("subsystems") of a physical system. In this illustrated
embodiment, computer 29 starts, stops, configures, and controls
connections and interactions between a plurality of models 22, 24,
26, 28, running on model host computers 23, 25, 27. Each model 22,
24, 26, 28 implements a model of one or more subsystems and makes
that implementation available for connection to models of other
portions of the system. A consistent external communication
interface (discussed in further detail below) for various hardware
and software platforms allows each subsystem to be modeled on a
different simulation platform and/or operating system, and further
allows different vendors of different subsystems to make models of
their subsystems available for simulation in combination with the
rest of the system.
[0020] It should be noted that the present description can most
easily be understood in terms of simulation of a physical system
with distinct physical subsystems. "System" as used herein,
however, is not intended to be limited to a physical arrangement of
components. The concept should be understood to include the subject
of any simulation. Likewise, a "subsystem" as used in the present
application is not necessarily a physically distinct set of
components. For example, one independently modeled "subsystem"
might be the heat transfer aspects of an item, while another
"subsystem" models the electronic aspects of the item.
[0021] The implementation of a model for simulation purposes may be
programmed by one or many programmers or organizations of
programmers, in the same language as other models in the system, or
in a different language.
[0022] System 20 will now be discussed in further detail with
continuing reference to FIG. 1. Network 21 interconnects computers
23, 25, 27, and 29. Models 22, 24, 26, 28, running on those
computers as illustrated collectively model a complete system, by
each modeling at least one subsystem and interacting to communicate
the states of the simulated interfaces between the subsystems at
various intervals in real or virtual time as will be discussed in
further detail below. Other applications involved in the
distributed simulation system 20 are shown in FIG. 1 in various
configurations. A simple model host computer 23 runs a single model
22, which is accessible to other models 24, 26, 28 and other
applications (such as system monitor 31) via network 21.
[0023] In many embodiments of the invention, however, resources
will be available within a single host computer to execute
additional applications. A common configuration is shown in
relation to computer 25 of FIG. 1. There, model 24 simulates one or
more subsystems, and control panel 32 issues start, stop, parameter
setting, connection-related, and other commands as will occur to
those skilled in the art. OSCOPE applications 33 and 34 display the
values of one or more variables or functions of variables of model
24 over time. It has been found experimentally that this grouping
of applications is a reasonably effective use of resources on a
single computer. When the resources required by a model are too
great to support the additional applications (for example, if the
model were a bottleneck in the simulation system), the other
components may be off-loaded from the host computer and executed on
a "neighboring" computer on a local-area network, for example.
[0024] In some situations, multiple models can be executed on a
single computer, as shown in relation to computer 27 in FIG. 1.
Computer 27 runs models 26 and 28, which are each associated with a
control panel (35 and 37, respectively) and OSCOPE (36 and 38,
respectively).
[0025] System monitor 31 runs on computer 29 and controls
parameters of and connections between models 22, 24, 26, 28. In
this exemplary embodiment, while control panels 32, 35, 37 each
control and monitor a single model (24, 26, 28, respectively),
system monitor 31 is designed to manage the whole distributed
simulation system 20. Also running on computer 29 is OSCOPE 39,
which monitors one or more variables or functions of variables of
model 22, for example.
[0026] A "system monitor" application 31 (also discussed in more
detail below) running on computer 29 sets parameters of the models,
controls the connections between the models, monitors their
functioning, and logs relevant facts, parameters, and events in the
simulation. Several functions of system monitor 31 will be detailed
further below.
[0027] Certain functional components of computers 23 and 25 will
now be discussed with reference to FIG. 2. Model host computer 23
comprises processor 41, which in one embodiment is a conventional,
integrated circuit microprocessor arrangement, such as one or more
PENTIUM III or PENTIUM 4 processors (supplied by INTEL Corporation
of Santa Clara, Calif., USA), Athlon processors (supplied by
Advanced Micro Devices, Inc., of Sunnyvale, Calif., USA), or
PowerPC processors (supplied by the Semiconductor Products Sector
of Motorola, Inc., of Austin, Tex., USA).
[0028] Storage 43 provides the data storage required by computer
23, including for example storage for program, model, log, and
other data. Storage 43 may include one or more types of solid-state
electronic memory, magnetic memory, or optical memory, just to name
a few. By way of non-limiting example, storage 43 may include
solid-state electronic Random Access Memory (RAM), Sequentially
Accessible Memory (SAM) (such as the First-In, First-Out (FIFO)
variety or the Last-In, First-Out (LIFO) variety), Programmable
Read-Only Memory (PROM), Electrically Programmable Read-Only Memory
(EPROM), or Electrically Erasable Programmable Read-Only Memory
(EEPROM); an optical disc memory (such as a DVD or CD-ROM); a
magnetically encoded hard disc, floppy disc, tape, or cartridge
media; or a combination of any of these memory types. Also, storage
43 may be volatile, nonvolatile, or a hybrid combination of
volatile and nonvolatile varieties.
[0029] Optional input device(s) 45 may include a keyboard, mouse,
track ball, light pen, and/or microphone, to name just a few
representative examples. Also, optional output device(s) 47 may
include one or more monitors, loudspeakers, printers, and/or other
recording devices, again to name just a few representative
examples.
[0030] Operating system 49 is a general-purpose operating system,
such as a WINDOWS operating system (published by Microsoft
Corporation of Redmond, Wash., USA) or a MAC OS (published by Apple
Computer, Inc., of Cupertino, Calif., USA). Other operating systems
may be used without undue experimentation by those skilled in the
art.
[0031] Running on operating system 49 is calculation platform 51,
which is a general-purpose computation and analysis package such as
MATLAB (published by The MathWorks, Inc., of Natick, Mass., USA).
Some alternative simulation program and platform configurations are
discussed below in relation to computers 25 and 27. In the case of
computer 23, however, an additional simulation toolbox 52 known as
SIMULINK (also published by The MathWorks, Inc.) is included to
allow the incorporation of the distributed simulation API for the
subsystem model implementation 22. Model 22 is, in this example,
written in the MATLAB programming language with references to
procedures and/or objects defined in the SIMULINK toolbox 52 and
the distributed simulation interface 55. Interface 55 provides an
API comprising functions that enable model 22 to programmatically
control connections from other computing devices and to process
data exchanged through them, as discussed further herein.
[0032] Computer 25 is controlled by processor 61 using programs
stored in storage 63 (where processor 61 and storage 63 may be of
any suitable type, as discussed above in relation to processor 41
and storage 43, respectively). Optional output device(s) 67 and
optional input device(s) 65 again facilitate interaction with human
users. Operating system 69 is, in this example, a WINDOWS 2000
operating system, published by Microsoft Corporation. Model 24
executes on OS 69 as a stand-alone application written in one or
more system programming languages, such as C, C++, Fortran, Visual
Basic, or JAVA.
[0033] Browser 71 enables access to and viewing of resources
available through network 21, such as Hypertext Markup Language
(HTML) files and JAVA applets (such as system control applet 32).
Browser 71 may be, for example, Netscape Navigator (published by
Sun Microsystems, Inc., of Palo Alto, Calif., USA). OSCOPE
applications 33 and 34 read state-related information from model 24
and send it as output to the user via output device(s) 67. Like
interface 55, distributed simulation interface 75 provides
communication-related functionality to model 24.
[0034] FIG. 3 shows the components of computers 27 and 29 (see also
FIG. 1). In computer 27, storage 83, optional input device(s) 85,
and optional output device(s) 87 are analogous to (though not
necessarily the same as) 43, 45, and 47. Here, again, subsystem
model implementations 26, 28 are stand-alone applications written
in one or more system programming languages, such as C, C++,
Fortran, Visual Basic, or JAVA, to name just a few nonlimiting
examples. Processor 81 is a custom-designed, application-specific
integrated circuit (ASIC) specially adapted for simulation
computations. A custom-designed simulation operating system 89 runs
subsystem model implementations 26 and 28, which communicate with
each other and with other models in system 20 via distributed
simulation interface 88. Control panel application 35 and OSCOPE
application 36 connect to model 26 and run on simulation operating
system 89, which also runs control panel 37 and OSCOPE 38 in
conjunction with model 28. System monitor application 31 runs on
operating system 99 to provide command and control functionality
for system 20 as summarized above and discussed in more detail
below. OSCOPE application 39 also runs on operating system 99,
displaying to the user at computer 29 an output of state-related
information from model 22 on computer 23 (see FIG. 1).
[0035] Computer 29 includes processor 91, storage 93, input
device(s) 95, and output device(s) 97 (analogous to, but not
necessarily the same as, corresponding components in computer 23;
namely, components 41, 43, 45, and 47). Operating system 99 is, for
example, a UNIX or UNIX-like operating system such as Red Hat Linux
(published by Red Hat, Inc., of Durham, N.C., USA).
[0036] While the above description relating to FIGS. 1-3
illustrates several uses and arrangements of computing resources,
and several illustrations of connections and relationships among
components, applications, applets, models, and other physical and
functional parts of system 20, it should be noted that those
skilled in the art will be able to implement distributed simulation
systems according to the present invention with these or other
physical and/or virtual configurations. For example, any
functionality described herein can be implemented in any computing
device in communication with at least one other component in the
system.
[0037] The process for carrying out a simulation according to one
embodiment of the present invention will now be discussed in broad
terms in relation to FIG. 4, with continuing reference to items
shown in and discussed in relation to FIGS. 1-3. Additional detail
regarding the control of connections among models in a selected
embodiment of the present invention will be discussed below in
relation to FIGS. 7A-7C. The process 100 in FIG. 4 starts at START
point 101. The various models are started at block 110. In various
embodiments, this event may be initiated for each model by an
action of a local user (such as a gesture in a desktop graphical
user interface (GUI)), by a remote user (for example, through a web
browser or by way of another signal), or by an automated process
(such as invocation by a task scheduler), to name just a few
possible triggers. In some of these embodiments, the operating
system 49, 69, 89, 99, calculation platform 51, simulation toolbox
52, subsystem model implementations 22, 24, 26, 28, and distributed
simulation interface software 55, 75, 88 are loaded into memory and
initialized with simulation parameters as will be understood by
those skilled in the art.
[0038] At block 120, parameters (such as capacitance of a
capacitor, or density of fuel in the system being simulated) for
the various models 22, 24, 26, 28 are set, for example, by the
system monitor application 31 or the control panel 32, 35, 37
associated with each particular model. In various embodiments,
these parameters may be provided by a local configuration file,
user input, a signal from system monitor 31 or a control panel, or
other source as would occur to one skilled in the art.
[0039] Models may be connected to and/or disconnected from other
models at block 130, again under the control of system monitor 31
or the model's respective control panel 32, 35, 37. For example, in
some embodiments that use the TCP/IP protocol stack, IP addresses
and TCP port numbers are obtained (e.g., from local storage 43, 63,
83, one or more command line parameters, system monitor 31, etc.),
and TCP connections are opened.
[0040] Connected models exchange control and state-related
information at block 140 and export state-related information to an
OSCOPE or other monitoring process at block 150. In the example
embodiment shown in FIGS. 1-3, subsystem model implementation 24
receives state-related messages from subsystem model implementation
22 that communicate information relating to one or more state
variables from subsystem model implementation 22. Subsystem model
implementation 24 then uses that information in its simulation. For
example, subsystem model implementation 24 will, in some
implementations, use the information from the state-related
messages as an input to the subsystem being simulated. In some of
these embodiments, state-related messages from subsystem model
implementation 24 to subsystem model implementation 22 provide
information relating to one or more state variables in subsystem
model implementation 24 as input(s) to the operation of subsystem
model implementation 22.
[0041] Other commands are processed by the models at block 160, and
it is determined at decision block 170 whether the system 20 should
continue operation. If so, process 100 returns to the beginning of
the command processing loop at block 120. If system 20 is not to
continue operation (negative result) at decision block 170, the
process 100 is ended at END point 199.
[0042] While process 100 is illustrated in FIG. 4 as a linear,
single-threaded task, it may be implemented in a multi-threaded
form, on multiple computing devices, or with an alternative control
flow, as would occur to one skilled in the art.
[0043] In this exemplary embodiment, distributed simulation
interfaces 55, 75, 88 expose an application programming interface
(API) for development of the various subsystem model
implementations 22, 24, 26, 28. The functions in this API, the ACSL
version of which is shown below in Table 1, allow the subsystem
model implementation programmer to control the variables that are
imported from and exported to other subsystem simulations.
TABLE-US-00001 TABLE 1 Function Arguments Description COM_INIT
(MIN) MIN--model index number Initialize a model for distributed
processing. ADD_PORT (name, desc., name--string name for the port
Declares a channel to be used status) desc--string that provides a
for input and/or output description variables/messages.
status--connection status variable ADD_PORT_VAR_IN (PIN, var)
PIN--port index number Associates an input variable var--variable
name for input with a port. from port ADD_PORT_VAR_OUT PIN--port
index number Associates an output variable (PIN, var) var--variable
name for output with a port. to port ADD_PARAM (name, value)
name--parameter name Declares a simulation variable value--initial
value that can be set by system monitor 31 and/or control panel 32,
35, 37 when this subsystem simulation is initialized or started. A
default value is provided. OSCOPE (OIN, t_interval, OIN--oscope
index number Defines a set of variables for var1, . . . , varN)
t_interval--communication export to an OSCOPE interval application
and the var1, . . . , varN--variable (simulation) time interval
names between samples. EXCHANGE (PIN, t_interval) PIN--port index
number Sets the rate of data exchange t_interval--communication for
a given port. interval COM_LISTEN (t_interval)
t_interval--communication Defines the frequency with interval which
the model will check for new control panel, system monitor, and
remote model data connections. COM_CLOSE No Arguments Stops the
model from listening for connections and exchanging data; frees
computing resources allocated to inter-model communication.
In this exemplary embodiment, port index numbers (PINs) and OSCOPE
index numbers (OINs) are sequentially assigned, beginning with
zero, each time the ADD_PORT or OSCOPE functions, respectively, are
called. Then, when an OSCOPE requests a connection to a particular
model, the model connects the requesting application (or applet) to
the next available OSCOPE index number, if another exists.
[0044] Thus, in the illustrated embodiment, the interval between
exchanges of data is set by the programmer of the model using the
commands shown in Table 1 before the simulation is executed.
Exchanges for a given port occur at regular intervals (which may be
the same as or different from the intervals used for other ports)
in simulation time, using the model time as a frame of reference.
In some alternative embodiments, a real-time or other external
frame of reference is used, while in other embodiments, the
intervals are dynamically controlled as discussed herein.
[0045] The functions shown in Table 1 are provided in various forms
to accommodate the various simulation environments that may be
available within system 20. For example, the functions may be
implemented in a dynamically linked library (.DLL), source code
library, device driver, operating system API or other format as
would occur to one skilled in the art and be acceptable given the
constraints of its implementation environment.
[0046] A message-handling loop for processing simulation control
messages appears in FIGS. 7A-7C. This example may easily be
modified by those skilled in the art to include additional message
processing tasks or other events that may occur in a given
implementation of the invention. Furthermore, non-message-based
control mechanisms may be used in various embodiments of the
invention.
[0047] A message handling loop 300 for a given model will now be
described in relation to FIGS. 7A-7C. To summarize, loop 300 begins
at START point 301, handles system monitor connection activity in
part 310, handles control panel activity in part 320, handles
commands from the control panel in part 330, handles incoming model
connection requests in part 350, handles incoming OSCOPE connection
activity in part 360, handles system monitor commands in part 370,
and ends at END point 399.
[0048] In part 310 of loop 300, the model confirms at block 312
that it is listening for incoming connection requests from system
monitor programs. If it is determined at decision block 314 that a
system monitor connection request is pending (positive result),
then at block 316 the system monitor attempting to connect is
established as the active system monitor for the local model(s).
Then, or if no such connection is pending (negative result at
decision block 314), processing in part 310 ends and loop 300
proceeds to part 320.
[0049] Loop 300 handles incoming control panel connection activity
in part 320 by first confirming in block 321 that the system is
listening for incoming control panel connections. If it is
determined at decision block 323 that an incoming connection is
pending from a control panel application (positive result), the
control panel application is established at block 325 as the active
control panel. Current parameter and port information for the local
model is then sent to that control panel at block 327, and if a
system monitor is active, it is notified of the new connection at
block 329. At that point, or if it is determined at block 323 that
no connection from an external control panel is waiting (negative
result), loop 300 proceeds beyond part 320 into part 330.
[0050] Loop 300 handles any pending control panel commands at part
330. It is determined at decision block 331 whether a control panel
is currently connected to the local model. If not (negative
result), loop 300 proceeds beyond part 330 (via placeholder A) to
part 350. If it is determined that a control panel is connected
(positive result at decision block 331), it is determined at
decision block 333 whether a command from that control panel is
waiting. If not (negative result at decision block 333), loop 300
proceeds to part 350 (via placeholder A).
[0051] If it is determined at decision block 333 that a command is
waiting (positive result), the command is read at block 335, and
the relevant parameter name and value for a "set parameter" are
read at block 337. The given parameter is updated to reflect the
new value at block 339, and if a system monitor is connected, it is
notified at block 341 of the update.
[0052] Decision block 343 implements an optional method for
connecting/disconnecting remote models via control panel commands.
If the parameter read at block 337 is not a valid port index number
("X" result at decision block 343), loop 300 proceeds to part 350
(via placeholder A). If the parameter name is a valid port index
number, and the corresponding port status value is not one
(negative result at decision block 343), the connection through
that port is closed at block 345, and loop 300 proceeds to part 350
(via placeholder A).
[0053] If the port status value is one (positive result at decision
block 343), model connection parameters (including, for example,
the IP number of the remote model host, the remote model index
number, the remote port index number, and the local model index
number) are read from the control panel at block 347. A connection
between the identified local model and the identified remote model
is then initiated at block 349, and loop 300 continues with part
350.
[0054] Loop 300 processes incoming connection requests from other
models in part 350. At block 351, it is confirmed that the server
is listening for model connection requests. If such a request is
not waiting (negative result at decision block 353), loop 300
proceeds to part 360. If a model connection request is waiting
(positive result at decision block 353), the requested PIN is read
at block 355, and a connection to the remote model is finalized at
block 357. The internal port status is then updated at block 359,
and loop 300 proceeds to part 360.
[0055] In part 360, loop 300 handles incoming requests for
connections from OSCOPE applications or applets. First, it is
confirmed at block 361 that the model is listening for such
connections. Then, if no OSCOPE connection request is waiting
(negative result at decision block 363), loop 300 proceeds to part
370. If such a request is waiting (positive result at decision
block 363), the next available OSCOPE identifier is determined at
block 365, and the metadata (the number of variables available via
the requested port, the names of those variables, and the name of
the model, for example) for that OSCOPE identifier is sent to the
OSCOPE application or applet at block 367. At block 369, the active
system monitor (if one is connected) is notified of the activity.
Loop 300 continues with part 370.
[0056] Commands from the system monitor (if one is connected) are
processed in part 370 of loop 300. First, it is checked at block
371 whether a system monitor is, indeed, connected. If not
(negative result), loop 300 ends at END point 399. If a system
monitor is connected (positive result at decision block 371), it is
determined at decision block 373 whether a command from that system
monitor is waiting to be processed. If no system monitor command is
waiting (negative result at decision block 373), loop 300
terminates at END point 399. If a command is waiting (positive
result at decision block 373), loop 300 proceeds (via placeholder
B) to part 400, shown in FIG. 7C. When processing in part 400 is
complete, loop 300 reaches END point 399 and terminates, or repeats
by beginning again at START point 301.
[0057] At block 401 in loop 400 shown in FIG. 7C, the requested
command is read from the system monitor. At decision block 411, it
is determined whether the system monitor is requesting display of
parameter and/or port data. If so, the name of the item being
requested is read at block 413. If that name is "PARAMS" or "ALL"
(positive result decision block 415), the names and corresponding
values of each parameter of the model are sent at block 417 to the
system monitor. Then (or upon a negative result at decision block
415) it is determined at decision block 419 whether the name that
was read at block 413 is "PORTS" or "ALL." If so (positive result
at decision block 419), the name and status of each port of the
model are sent to the system monitor at block 421. If, however, the
result at decision block 419 is negative, the name and value of the
specified (at block 413) parameter are sent to the system monitor
at block 423. After the actions of either block 421 or 423, loop
300 returns (via placeholder C) to the END point 399.
[0058] If the command read at block 401 is not a request for
display of one or more parameters (i.e., a negative result at block
411), it is determined at decision block 431 whether the command is
for the registration of a model. If so, the model name is read at
block 433 and the model is registered at block 435. Loop 300 then
returns (via placeholder C) to END point 399.
[0059] If the command read at block 401 is also not for
registration of a model (negative result at decision block 431), it
is determined at decision block 441 whether the command was a
request to set a parameter value. If so (positive result), the name
and new value are read at block 443, and the value of the specified
parameter is updated at block 445. Then, for logging, debugging, or
other purposes, the names and values of all parameters and ports
are sent to the control panel at block 447. Loop 300 then returns
(via placeholder C) to END point 399.
[0060] If the command read at block 401 is also not a request to
set a model parameter (negative result at decision block 441), it
is determined at decision block 451 whether the command is a
request to connect a local model to a remote model. If so (positive
result), the parameters for establishing that connection (see above
discussion in relation to block 347) are read at block 453. The
requested connection between the remote model and the local model
is then initiated and established at block 455. Loop 300 continues
at block 447 by sending the values and status of the parameters and
ports to the control panel as discussed above, and returns (via
placeholder C) to END point 399.
[0061] If the command read at block 401 is not a request to connect
a model (negative result at decision block 451), it is determined
at block 461 whether the command is to disconnect a model. If so
(positive result), the port to disconnect is read at block 463. It
is then determined at decision block 465 whether all ports have
been requested to be disconnected. If so (positive result), all
ports are closed at block 467 and loop 300 proceeds with a report
to the control panel of parameter and port information at block
447, discussed above. If a specific port was requested to be closed
(negative result at decision block 465), that specific port is
closed at block 469, and loop 300 continues with the report of
parameter and port information at block 447, discussed above.
[0062] If the command read at block 401 is determined at decision
block 461 not to be a disconnect request, the command is ignored,
and loop 300 proceeds (via placeholder C) to END point 399. It
should be noted that various embodiments of the present invention
may process different, additional, or fewer commands than those
discussed in relation to part 400, as would be understood by those
skilled in the art. It should also be noted that those skilled in
the art will understand other commands to be available via the
control panel other than the "set parameter" command described in
relation to FIGS. 7A-7C.
[0063] It may also be observed that loop 300 illustrates the
simultaneous connection of at most one system monitor and one
control panel to a given model. While some embodiments of the
present invention may operate with both types of control
applications being connected, others may prevent the simultaneous
connection of both types of control applications, and others may
require both to be connected for certain functionality. Still
others may allow multiple instances of one or both types of control
applications to a given model.
[0064] It should also be noted that the discussion of loop 300 has
been simplified for easier understanding by omitting details
relating to communication protocols being used, acknowledgements
being sent and/or expected, and error handling. For example, it is
preferred that model, port, OSCOPE, and other identification
numbers and handles be validated by distributed simulation
interfaces 55, 75, 88 before they are used. In some embodiments,
errors are ignored, while in other embodiments, they cause a log
entry to be created, alarm to be set off, and/or the system
halted.
[0065] An exemplary embodiment of an OSCOPE application according
to one form of the present invention will now be discussed with
reference to FIG. 5. The OSCOPE application facilitates access to
particular state-related information of the various models 22, 24,
26, 28 of system 20. A graphical user interface (GUI) 200,
comprising control elements 202, output formatting elements 204,
and graph elements 206, facilitates user interaction with the
OSCOPE application. Control elements 202 accept the user's
selection of a model host (IP address), model index number (MIN),
and output format for the display. When the user selects the
"connect" check box, the OSCOPE application attempts to connect to
the selected model.
[0066] As the simulation data is received from the selected model,
it is displayed in output graphs 206. Various user interface
components 204 allow the user to select a wide variety of formats
for display, including selecting the variable to graph, scaling the
graph in one or more dimensions, automatically scaling the graph
using the ranges of data points acquired, displaying repeated
traces based on one or more trigger points in one or more signals
being graphed, connecting the sample points in the display, and/or
transforming the signal through a FFT (fast Fourier transform) to
name just a few nonlimiting examples. In this illustration, the
output is graphed in graphs 206, which can be saved on any
appropriate medium in any appropriate format, including for example
a graphics file on a magnetic disk. It will be understood by those
skilled in the art that alternative selection, control, and output
forms and techniques may be used as required or desired in a
particular embodiment. For example, signal data may be printed in
the form of a page, plot, or strip chart by a printer that
comprises an "output device" 67 in FIG. 2.
[0067] A GUI for use with system 20 is illustrated in FIG. 8. Check
box 221 establishes or breaks a connection with a particular model
based on user input. Model information area 223 reflects the values
of the connected model's parameters and the status of the model's
ports. The "parameter" and "value" fields can be used to change the
parameters of the model to which the control panel is connected,
while the "Local I/O Port" and "Port Status" elements can be used
to connect/disconnect models to/from the model being controlled.
When it is desired to connect to a remote model, the IP address,
port identification number, and model identification number are
entered in area 225 of GUI 220. In this embodiment, each time the
user desires to submit information to the model, the "submit"
button 227 is selected, and the information is transmitted to the
model using methods, techniques and protocols known in the art.
Messages received from the connected model as well as any error
messages are shown to the user in text box 229.
[0068] As will be apparent to those skilled in the art, traditional
and/or alternative components may exist in or be attached to any of
the computing devices discussed in this description. Similarly, the
networks shown may also connect devices not shown herein, including
but not limited to devices that have no role in the distributed
simulation.
[0069] In one alternative embodiment of the invention, subsystem
model implementations 22, 24, 26, 28 are dynamically connected and
configured while the model is being executed. In some cases, this
dynamic connection simulates physical connection or reconnection of
the physical components being modeled in the respective
implementations.
[0070] In another alternative embodiment, a plurality of simulation
programs together simulate a system, each simulation program
simulating a different subsystem of the system. In yet another
embodiment, different persons specify the parameters and data of
the various subsystem models that can be viewed and/or controlled
by or through other computers in the network.
[0071] A portion of still another embodiment is shown in FIG. 6. A
plurality of computers 251 form a subnetwork 261 in communication
with network 21. Each computer 251 models part of a subsystem,
while a gateway computer 251a in the subnetwork 261 serves as a
communication gateway for state-related messages sent between the
computers in the subnetwork 261 and the rest of the network 21.
Gateway computer 251a may or may not also host one or more models.
In some embodiments of this configuration, the simulations taking
place on the non-gateway computers 251 occur independently (i.e.,
without reliance on state information from any other model). In
these cases, gateway computer 251a collects the results of those
subsystem simulations, and may aggregate them or pass along the raw
data to other models or other components in system 20.
[0072] In another form of the present invention, a plurality of
interrelated simulation programs are executed on a plurality of
computers in a network. The plurality of interrelated simulation
programs operate in parallel and exchange data with each other. In
some embodiments of this form, the various simulation programs are
each executed on the same software package (such as ACSL (published
by The Aegis Technologies Group, Inc., of Huntsville, Ala.,
U.S.A.), Saber (published by Avant! Corporation of Fremont, Calif.,
U.S.A.), MATLAB/SIMULINK, or EASY 5 (published by The Boeing
Company of Chicago, Ill., U.S.A.)). In other embodiments of this
form, the various subsystem simulations are executed by a
heterogeneous group of software packages (such as an ACSL model on
one computer and two MATLAB/SIMULINK models, each on another
separate computer).
[0073] In one embodiment of this form, the plurality of simulation
programs together simulate a real system, wherein each simulation
program simulates a different real subsystem of the real system. In
another embodiment of this form, different persons specify the
parameters and data of the various simulation programs that can be
viewed and/or controlled by or through other computers in the
system 20.
[0074] In another form of the present invention, a
computer-readable medium is encoded with programming instructions
executable by a first processor to (a) implement a first simulation
model having a first state variable, (b) accept a first command
signal from a program being executed by another processor, and (c)
manage the first simulation model based on the first command
signal; likewise, second computer-readable medium is encoded with
programming instructions executable by a second processor in
communication with an output device to (1) send the first command
signal to the first processor, (2) cause the output device to make
a first output reflecting information relating to the first state
variable over a period of simulation time. In one embodiment of
this form of the invention, information relating to the value of
one or more state variables in the first simulation are passed to
(or received from) the second simulation at regular intervals of
real time. In another embodiment of this form, information relating
to the values of one or more state variables in the first
simulation are passed to (or received from) the second simulation
at regular intervals of simulation time. In yet another embodiment
of this form, information relating to the values of one or more
state variables in the first simulation are passed to (or received
from) the second simulation at intervals of simulation time that
vary according to the state(s) of one or more models in the system.
In still another embodiment of this form, information relating to
the values of two or more state variables in the first simulation
are passed to (or received from) the second simulation. In a
further embodiment, information relating to the values of four or
more state variables in the first simulation are passed to (or
received from) the second simulation. In a still further embodiment
of this form, information relating to the values of n.gtoreq.2
state variables in the first simulation are passed to (or received
from) the second simulation, and at least one message in a series
of state-related messages sent by the first simulation contains
information relating to the value of each of the n.gtoreq.2 state
variables. In a yet further embodiment, information relating to the
values of n.gtoreq.2 state variables in the first simulation are
passed to (or received from) the second simulation, and at least
one message in a series of state-related messages sent by the first
simulation contains information relating to the value of exactly
one of the n state variables. In other embodiments of this form,
one process makes the request, but the first simulation directs the
series of state-related messages to a different process. In yet
another embodiment, a process receives the series of state-related
messages and displays (e.g., a graph of a function of a state
variable versus [simulation] time) on an output device (e.g., a
monitor or printer) information carried by a plurality of the
messages in that series.
[0075] Yet another form of the present invention comprises a
plurality of simulations operating on a plurality of computers. A
system monitor communicates with each simulation, and is capable of
configuring, controlling, and/or coordinating each simulation. In
one embodiment of this form, a local control panel applet is also
provided for each simulation and is capable of configuring,
controlling, and/or coordinating that particular simulation.
[0076] In some embodiments, different subsystem model
implementations 22, 24, 26, 28 use different techniques and/or
parameters for integration. For example, one model might use the
finite Euler integration technique with new values being estimated
every millisecond, while another uses Runge-Kutta integration with
a one microsecond estimation interval. This type of embodiment
enables more efficient simulation of systems that include
fast-changing and slow-changing signals by "sampling" each
subsystem at an appropriate rate without wasting computing
resources on frequent sampling of slow-changing signals.
[0077] In some embodiments, plug-in components are provided for
simulation development, wherein a "black box" element is placed in
a subsystem model implementation design to represent one or more
other subsystems in the simulation. Parameters are programmed for
the "black box" that define the inputs and outputs of the subsystem
that will be provided by and to (respectively) the neighboring
subsystem. In some of these embodiments, the "black box" is
represented by a block in a GUI simulation design tool. Fields
associated with the "black box" in the subsystem model
implementation indicate the networking (e.g., IP address and TCP
port number) and signaling (e.g., messaging frequency and
availability of variables) parameters for that connection.
[0078] It will be understood by those skilled in the art that
computers 23, 25, 27, 29, and other computers discussed in this
description may comprise additional or alternative components as
needed or desired in a particular implementation. Likewise,
additional or alternative devices may be connected to network 21
and or subnetwork 261 (see FIGS. 1 and 6) without departing from
the spirit of this invention.
[0079] All publications, prior applications, and other documents
cited herein are hereby incorporated by reference in their entirety
as if each had been individually incorporated by reference and
fully set forth.
[0080] While the invention has been illustrated and described in
detail in the drawings and foregoing description, the same is to be
considered as illustrative and not restrictive in character, it
being understood that only the preferred embodiments have been
shown and described and that all changes and modifications that
would occur to one skilled in the relevant art are desired to be
protected.
* * * * *