Patent Publication Number: US-11030362-B2

Title: Modeling and cooperative simulation of systems with interdependent discrete and continuous elements

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of U.S. application Ser. No. 13/531,995, filed on Jun. 25, 2012, the entirety of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to modeling and simulating systems in general. 
     BACKGROUND OF THE INVENTION 
     Systems engineers often employ modeling tools to model aspects of systems for testing and design purposes. Some modeling tools, such as IBM Rational® Rhapsody®, are adapted for modeling discrete aspects of a system that are event-driven, while other modeling tools, such as Mathworks® Simulink®, are adapted for modeling continuous aspects of a system that are commonly described by time-dependent differential equations. Such tools often enable simulations of models to be performed in order to determine if the models behave as expected. Systems often include both discrete and continuous elements that are interdependent but that are separately modeled and simulated using different modeling tools. 
     SUMMARY OF THE INVENTION 
     In one aspect of the invention a method is provided for cooperative modeling of discrete system elements and continuous system elements, the method including modeling, in a first modeling environment, a discrete system element and a relationship between the discrete system element and a continuous system element, and exporting, from the first modeling environment to a second modeling environment, a description of the discrete system element and of the relationship between the discrete system element and the continuous system element, thereby causing the discrete system element and the relationship between the discrete system element and the continuous system element to be modeled in the second modeling environment, wherein the continuous system element is modeled in the second modeling environment. 
     In other aspects of the invention systems and computer program products embodying the invention are provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the appended drawings in which: 
         FIG. 1  is a simplified conceptual illustration of a system for modeling and cooperative simulation of systems with interdependent discrete and continuous elements, constructed and operative in accordance with an embodiment of the invention; 
         FIGS. 2A and 2B  are simplified flowchart illustrations of exemplary methods of operation of the system of  FIG. 1 , operative in accordance with embodiments of the invention; 
         FIGS. 3A-3C  are simplified conceptual illustrations of various aspects of the operation of the system of  FIG. 1  and methods of  FIGS. 2A and 2B  with respect to an exemplary scenario, operative in accordance with an embodiment of the invention; and 
         FIG. 4  is a simplified block diagram illustration of an exemplary hardware implementation of a computing system, constructed and operative in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention is now described within the context of one or more embodiments, although the description is intended to be illustrative of the invention as a whole, and is not to be construed as limiting the invention to the embodiments shown. It is appreciated that various modifications may occur to those skilled in the art that, while not specifically shown herein, are nevertheless within the true spirit and scope of the invention. 
     As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon. 
     Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical data storage device, a magnetic data storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. 
     A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. 
     Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing. 
     Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirely on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). 
     Aspects of the present invention are described below with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks. 
     The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     Reference is now made to  FIG. 1  which is a simplified conceptual illustration of a system for modeling and cooperative simulation of systems with interdependent discrete and continuous elements, constructed and operative in accordance with an embodiment of the invention. In the system of  FIG. 1  a first modeling environment  100  is configured to model a discrete system element  102  and a relationship  104 , such as a signal flow or data flow, between discrete system element  102  and a continuous system element  106 . Although only one discrete system element  102 , relationship  104 , and continuous system element  106  are shown, it is appreciated that any number of such elements and their relationships may be modeled as shown, and that reference is made to these elements in the singular for the sake of brevity only. Preferably, relationship  104  maps between interfaces exposed by discrete system element  102  in first modeling environment  100  and interfaces exposed by continuous system element  106  in a second modeling environment  110 . A model exporter  108  is configured to export from first modeling environment  100  to second modeling environment  110  a description of discrete system element  102  and of relationship  104  between discrete system element  102  and continuous system element  106 . The description may, for example, include software instructions that second modeling environment  110  may use to simulate discrete system element  102 . Second modeling environment  110  is configured to model discrete system element  102  and relationship  104  in the second modeling environment, preferably responsive to receiving the exported description from model exporter  108 , and preferably where continuous system element  106  is modeled in second modeling environment  110 . 
     A simulation manager  112  is configured to initiate a simulation of discrete system element  102  and continuous system element  106  in second modeling environment  110 , where one or more outputs of continuous system element  106  during the simulation in second modeling environment  110  may be used as input to discrete system element  102 , and/or where one or more outputs of discrete system element  102  during the simulation in second modeling environment  110  may be used as input to continuous system element  106 . 
     In an alternative embodiment, simulation manager  112  is configured to initiate a simulation of discrete system element  102  in first modeling environment  100  and initiate a simulation of continuous system element  106  in second modeling environment  110 , preferably such that both simulations are performed at least partially concurrently. One or more outputs of continuous system element  106  during the simulation in second modeling environment  110  may be provided as input to discrete system element  102  during the simulation in first modeling environment  100 , and/or one or more outputs of discrete system element  102  during the simulation in first modeling environment  100  may be provided as input to continuous system element  106  during the simulation in second modeling environment  110 . This may, for example, be achieved where a common TCP/IP socket is used by both modeling environments during their simulations, such as where the description of discrete system element  102  and relationship  104  exported by model exporter  108  from first modeling environment  100  to second modeling environment  110  includes software instructions that second modeling environment  110  may use to simulate discrete system element  102  and that include instrumentation that enables communications between first modeling environment  100  and second modeling environment  110  via the common TCP/IP socket. 
     Any of the elements shown in  FIG. 1  are preferably implemented by one or more computers, such as computer  114 , in computer hardware and/or in computer software embodied in a non-transitory, computer-readable medium in accordance with conventional techniques. 
     Reference is now made to  FIG. 2A , which is a simplified flowchart illustration of an exemplary method of operation of the system of  FIG. 1 , operative in accordance with an embodiment of the invention. In the method of  FIG. 2A , a discrete system element and a relationship between the discrete system element and a continuous system element is modeled in a first modeling environment (step  200 ). A description of the discrete system element and of the relationship between the discrete system element and the continuous system element is exported from the first modeling environment to a second modeling environment (step  202 ), thereby causing the discrete system element and the relationship between the discrete system element and the continuous system element to be modeled in the second modeling environment (step  204 ), preferably where the continuous system element is modeled in the second modeling environment. A simulation of the discrete system element and the continuous system element is initiated in the second modeling environment (step  206 ). One or more outputs of one of the elements during the simulation are provided as input to the other element during the simulation, and/or vice versa (step  208 ). 
     Reference is now made to  FIG. 2B , which is a simplified flowchart illustration of an exemplary method of operation of the system of  FIG. 1 , operative in accordance with an embodiment of the invention. In the method of  FIG. 2B , a discrete system element and a relationship between the discrete system element and a continuous system element is modeled in a first modeling environment (step  210 ). A description of the discrete system element and of the relationship between the discrete system element and the continuous system element is exported from the first modeling environment to a second modeling environment (step  212 ), thereby causing the discrete system element and the relationship between the discrete system element and the continuous system element to be modeled in the second modeling environment (step  214 ), preferably where the continuous system element is modeled in the second modeling environment. A simulation of the discrete system element is initiated in the first modeling environment (step  216 ). A simulation of the continuous system element is initiated in the second modeling environment, preferably such that both simulations are performed at least partially concurrently (step  218 ). One or more outputs of one of the elements during one of the simulations are provided as input to the other element during the other simulation, and/or vice versa (step  220 ). 
     The system of  FIG. 1  and method of  FIGS. 2A and 2B  may be illustrated by way of example with reference to  FIGS. 3A-3C . In  FIG. 3A , IBM Rational® Rhapsody®, commercially available from International Business Machines Corporation, Armonk, N.Y., is used to create a structure block  300  in which discrete system elements ‘c:Controller’ (part ‘c’ of class Controller) and ‘s:Speedometer’ are modeled as blocks  302  and  304 . Continuous system elements ‘pf:PFeedback’ and ‘vd:VehicleDynamics’ are modeled as blocks  306  and  308 , and are preferably identified within IBM Rational® Rhapsody®, such as with a ‘SimulinkBlock’ stereotype, as being associated with corresponding continuous system elements that are modeled in Mathworks® Simulink®, commercially available from The MathWorks, Inc., Natick, Mass. The relationships between any of blocks  302 ,  304 ,  306 , and  308  are also modeled within structure block  300 . A structure block  310  is created within IBM Rational® Rhapsody® as shown in  FIG. 3B  that includes only discrete elements  302  and  304  of structure block  300 , where the relationships between discrete elements  302  and  304  and continuous elements  306  and  306  are modeled as relationships to/from structure block  310 . IBM Rational® Rhapsody® exports structure block  310  to Mathworks® Simulink® as a user-defined ‘S-Function’ definition. As shown in  FIG. 3C , Mathworks® Simulink® models the exported ‘S-Function’ definition as an ‘S-Function’ simulation node  312  and associates its relationships with continuous elements  314  and  316  that are modeled within Mathworks® Simulink® as well and that correspond to blocks  306  and  308  in structure block  300  of IBM Rational® Rhapsody®. The process of exporting the ‘S-Function’ definition from IBM Rational® Rhapsody® to Mathworks® Simulink® is preferably done when initiating a simulation of structure block  300  within IBM Rational® Rhapsody®, where IBM Rational® Rhapsody® also causes Mathworks® Simulink® to initiate a simulation of simulation node  312  and continuous elements  314  and  316 . IBM Rational® Rhapsody®, and Mathworks® Simulink® are both preferably configured in accordance with conventional techniques, such as using software plug-ins or common communications sockets, to communicate with each other. In this manner, interdependent discrete and continuous system elements may be cooperatively simulated, where outputs from continuous system elements during a Mathworks® Simulink® simulation are provided as inputs to discrete system elements during an IBM Rational® Rhapsody® simulation, and/or outputs from discrete system elements during an IBM Rational® Rhapsody® simulation are provided as inputs to continuous system elements during a Mathworks® Simulink® simulation. 
     Referring now to  FIG. 4 , block diagram  400  illustrates an exemplary hardware implementation of a computing system in accordance with which one or more components/methodologies of the invention (e.g., components/methodologies described in the context of  FIGS. 1, 2A, and 2B ) may be implemented, according to an embodiment of the invention. 
     As shown, the techniques for controlling access to at least one resource may be implemented in accordance with a processor  410 , a memory  412 , I/O devices  414 , and a network interface  416 , coupled via a computer bus  418  or alternate connection arrangement. 
     It is to be appreciated that the term “processor” as used herein is intended to include any processing device, such as, for example, one that includes a CPU (central processing unit) and/or other processing circuitry. It is also to be understood that the term “processor” may refer to more than one processing device and that various elements associated with a processing device may be shared by other processing devices. 
     The term “memory” as used herein is intended to include memory associated with a processor or CPU, such as, for example, RAM, ROM, a fixed memory device (e.g., hard drive), a removable memory device (e.g., diskette), flash memory, etc. Such memory may be considered a computer readable storage medium. 
     In addition, the phrase “input/output devices” or “I/O devices” as used herein is intended to include, for example, one or more input devices (e.g., keyboard, mouse, scanner, etc.) for entering data to the processing unit, and/or one or more output devices (e.g., speaker, display, printer, etc.) for presenting results associated with the processing unit. 
     The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions. 
     It will be appreciated that any of the elements described hereinabove may be implemented as a computer program product embodied in a computer-readable medium, such as in the form of computer program instructions stored on magnetic or optical storage media or embedded within computer hardware, and may be executed by or otherwise accessible to a computer (not shown). 
     While the methods and apparatus herein may or may not have been described with reference to specific computer hardware or software, it is appreciated that the methods and apparatus described herein may be readily implemented in computer hardware or software using conventional techniques. 
     While the invention has been described with reference to one or more specific embodiments, the description is intended to be illustrative of the invention as a whole and is not to be construed as limiting the invention to the embodiments shown. It is appreciated that various modifications may occur to those skilled in the art that, while not specifically shown herein, are nevertheless within the true spirit and scope of the invention.