Co-simulation Method of Modelica Platform and UE4 Based on Opendds

Abstract

The present invention relates to a co-simulation method for the Modelica platform and UE4 based on Opendds, including: using the Modelica platform software to model simulation objects to obtain a model file in Modelica language; parsing the model file to generate simulation model source code; using the publish / subscribe mechanism of the Opendds middleware, with the Modelica platform as the publisher and the UE4 software as the subscriber, to establish a data transmission channel between the Modelica platform and the UE4 software through source code integration; establishing a UE4 simulation scene, loading the Opendds subscriber plugin in the simulation scene, encapsulating the interface functions in the Opendds subscriber plugin as blueprint nodes, calling the subscriber in the UE4 simulation scene to receive simulation object data, and loading the simulation objects in the simulation scene; loading local resources, setting the camera perspective of the simulation objects, and starting the multi-perspective visualization simulation of the simulation objects. Compared with the existing simulation systems, through co-simulation, the present invention can achieve a better three-dimensional display effect, has a stronger rendering ability for natural phenomena, and is beneficial to the intuitive analysis of simulation results.

Description

Technical Field

[0001] The present invention belongs to the field of computer simulation, and particularly relates to a co-simulation method for a Modelica platform and UE4 based on Opendds. Background Art

[0002] Currently, computer simulation has become an important means for the analysis, research, testing, evaluation, development, and skill training of complex large systems, and has been widely used in important fields of various industries such as national defense, manufacturing, energy, transportation, agriculture, medical care, education, economy, weather forecasting, etc. With the continuous application of simulation in various industries and fields, engineering simulation visualization, due to the use of computer graphics to visually simulate the engineering space environment and design scheme, can intuitively and vividly express the scheme, sort out the design ideas, or accurately and quickly convey the design intent to a third party, thus developing well in the simulation field.

[0003] Modelica is a multi-domain unified modeling language with great development potential at present and can be applied to simulation modeling in many fields. OpenModelica is an open-source implementation based on Modelica language simulation, providing functions such as modeling, compilation, simulation, and result display based on the Modelica language. There are two problems with the Modelica-based simulation method: one is that the simulation results of the Modelica platform are mainly displayed in one-dimensional or two-dimensional forms of result data. Especially in the field of large-scale aerospace simulation, the display of simulation results is not intuitive enough, and it is difficult to highlight the change characteristics of simulation results. The other is that the three-dimensional display of the simulation results of mainstream simulation software in the engineering field is not prominent, the physical simulation effect is poor, and the rendering ability for natural phenomena such as lighting and weather is even lacking.

[0004] The models established by the existing simulation software generally do not have a model conversion interface, and the model will be damaged or missing after being imported into the simulation engine. For simulation scenarios that need to combine the layout characteristics of the digital earth, the visualization display views of these simulation software cannot guarantee obtaining the overall engineering effect and construction performance. Summary of the Invention

[0005] The purpose of the present invention is to solve the above problems, and provide a co-simulation method for a Modelica platform and UE4 based on Opendds, apply the excellent animation scene rendering ability of UE4 to the object simulation field, establish a data transmission channel between the Modelica platform and UE4 software based on the Opendds middleware, and realize the object simulation of the cooperation between the Modelica platform and UE4.

[0006] The technical solution of the present invention is a co-simulation method for a Modelica platform and UE4 based on Opendds, specifically including the following steps:

[0007] Step 1: Use the Modelica platform to perform simulation modeling to obtain a model file in Modelica language; parse the model file and convert it to obtain the corresponding C language source file;

[0008] Step 2: Use the publish / subscribe mechanism of the Opendds middleware. With the Modelica platform as the publisher and the UE4 software as the subscriber, generate the C / C++ language code for the publisher and subscriber respectively, integrate the code with the Modelica platform and UE4 software respectively, and establish a data transmission channel between the Modelica platform and UE4 software;

[0009] Step 3: Establish a UE4 simulation scenario, load the Opendds subscriber plugin in the simulation scenario, encapsulate the interface functions in the Opendds subscriber plugin as blueprint nodes, call the subscriber in the UE4 simulation scenario to receive simulation object data, and load the simulation object in the simulation scenario; load local resources, set the camera view of the simulation object, and start the multi-view visualization simulation of the simulation object.

[0010] Further, Step 1 specifically includes: using the Modelica platform to establish a Modelica model, generating a Modelica model file at a specified path; converting the Modelica model file to generate C / C++ language simulation code, compiling and linking the publisher code generated by Opendds with the above-converted C / C++ simulation code to generate an executable simulation model; performing real-time simulation or offline simulation on the executable simulation model and outputting simulation result data.

[0011] Preferably, Step 2 adopts the dynamictype standard of the Opendds middleware to enable the publisher and subscriber to support dynamic data type extension. When the data type transmitted by the Modelica platform changes, the subscriber code of UE4 can receive the dynamically extended data from the publisher without recompilation.

[0012] Further, Step 2 specifically includes:

[0013] Step 2.1: Configure the publisher and subscriber to the same domain value; register the data types transmitted during the simulation process, and configure the data types of the communication convention between the publisher and subscriber; configure the topics corresponding to the registered data types, customize specific names for each topic in the domain, and correspond them to the specific data types published by the publisher;

[0014] Step 2.2: Configure the data writer and publisher. The publisher passes data to the Opendds middleware through the data writer. Each data writer corresponds to a specific topic. The publisher uses the data writer's specified type interface to publish data samples on the bound topic;

[0015] After the data writer encodes the simulation transmission data, it passes it to the publisher for preparation for transmission. After the publisher obtains the data to be published, it passes it to all subscribers in the domain;

[0016] Step 2.3: Configure and register the data type corresponding topic at the subscriber side. Customize a specific name for each topic in the domain and correspond it to the specific data type published by the publisher; The subscriber obtains data by identifying the topic name published by the publisher;

[0017] Configure the data reader and subscriber. The subscriber receives data from the publisher and transmits the obtained data to all associated data readers; Configure the listening code at the subscriber side to transmit the monitored data type to the subscriber; The data reader obtains data from the subscriber, decodes it into the corresponding topic data type, and finally transmits the data to the middleware subscriber node integrated with the UE4 scenario;

[0018] Step 2.4: For the type of data to be transmitted, define and represent the data transmission service according to the interface description language to obtain the IDL file for data definition and representation, and compile the IDL file to map it to the c++ type support file;

[0019] Step 2.5: Write the MPC file, perform the engineering processing of the MPC file, generate the source codes of the publisher and subscriber respectively, and integrate and compile them with the Modelica platform and UE4 into executable files; Run the executable file to perform data transmission.

[0020] Further, Step 3 specifically includes:

[0021] 3.1) Write the Opendds subscriber plug-in module for the UE4 external dynamic plug-in, write the Opendds subscriber code into the plug-in and compile it for use;

[0022] 3.2) Call the Opendds subscriber plug-in module node in the level blueprint of the UE4 scenario, link each node in the blueprint editor, and compile the blueprint to output the subscriber receiving data instance;

[0023] 3.3) Use software such as 3DS MAX, CATIA, UG, and World Machine to generate the simulation object model and load the simulation object model into the simulation scenario;

[0024] 3.4) Load the Cesium for Unreal plug-in in the UE4 software and load the digital globe for the UE4 simulation scene;

[0025] 3.5) Configure camera perspectives to provide users with multi-perspective, all-round simulation situation display.

[0026] Compared with the prior art, the beneficial effects of the present invention include:

[0027] 1) The present invention realizes the object simulation of the collaboration between the Modelica platform and the UE4 software, and solves the problem that the display of the simulation results of the Modelica software is not intuitive enough. Compared with the existing mainstream simulation software in the engineering field, the collaborative simulation method of the present invention has better physical simulation effect, stronger rendering ability for natural phenomena, and better global effect of the simulation scene, especially in the field of large-scale aerospace simulation, the simulation results have good visual effect.

[0028] 2) In view of the data transmission characteristics of the simulation field, such as multiple data sources, large multi-source data volume, complex structure, and frequent transmission, the present invention adopts Opendds as the transmission middleware to meet the data transmission requirements of the collaborative simulation system.

[0029] 3) In view of the technical characteristics of DDS itself, this technology is mainly used in replicated distributed systems that require real-time and efficient data transmission. Developers can apply Opendds to a single computer or deploy it in a distributed manner on different computer devices without paying attention to its underlying physical communication protocol, providing a multi-scenario simulation method.

[0030] 4) The latest Opendds supports DynamicType, a dynamic data type. The data structure type can be modified on the publishing side, or when a data transmission topic is added, the subscriber side uses the recorder method to receive new data types without modifying or compiling the code. The subscriber side can receive data at the lowest cost based on changes in simulation software result data.

[0031] 5) UE4's unique blueprint system provides developers with an intuitive and clear editing interface. Compared with the full use of code, this graphical programming method has a relatively large advantage in development efficiency. The functions of this collaborative simulation system are mainly implemented using blueprints.

[0032] 6) The present invention utilizes the excellent rendering capabilities of the UE4 engine to combine the global terrain seamless simulation scene with the Modelica platform. In terms of simulation visual effects, compared with the three-dimensional scene that comes with the simulation software, the UE4 scene is more realistic and more in line with simulation requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0034] Figure 1 Schematic diagram of the co - simulation of the Modelica platform and UE4 in the embodiment of the present invention.

[0035] Figure 2 Schematic diagram of the simulation process of the OpenModelica secondary development software.

[0036] Figure 3 Schematic diagram of the process of building the Opendds middleware.

[0037] Figure 4 Schematic diagram of the MPC project file in the embodiment of the present invention.

[0038] Figure 5 Schematic diagram of the code of the dynamic data extension subscription end.

[0039] Figure 6 Schematic diagram of the process of building the UE4 simulation scene in the embodiment of the present invention.

[0040] Figure 7 Schematic diagram of the method for calling the Opendds middleware subscription - end plugin on the UE4 scene side in the embodiment of the present invention.

[0041] Figure 8 Effect picture of the main interface of the simulation project in the embodiment of the present invention.

[0042] Figure 9 Effect picture of the multi - perspective simulation example of the simulation project in the embodiment of the present invention. Detailed implementation manners

[0043] The simulation object of the embodiment is an aircraft.

[0044] In the embodiment, the Modelica platform selects a software platform based on the secondary development of Openmodelica. Using this platform for simulation modeling, a model file in Modelica language is obtained; the model file is parsed, language conversion is performed on the model file, and an executable file is compiled.

[0045] Opendds middleware: Opendds adopts a publish / subscribe architecture, emphasizes data - centric, provides rich QoS (Quality of Service) strategies, can ensure real - time, efficient, and flexible distribution of data, and can meet the requirements of various distributed real - time communication applications. By configuring the Opendds middleware publisher and subscriber, data is transmitted. At the same time, Opendds supports dynamic data extension. When the data transmission type changes, the project subscriber - end code does not need to be recompiled and can successfully receive the dynamically extended data from the publisher.

[0046] UE4 Simulation Scenario: By comprehensively using software such as 3DS MAX and World Machine, a terrain model corresponding to the simulation terrain scenario is generated, and models such as the simulation object aircraft model, ground inspection equipment, and launch equipment are imported to construct an extremely large three-dimensional simulation space corresponding to the real simulation scenario, providing multi-perspective and all-round simulation situation display for simulation researchers, providing a more intuitive and realistic judgment basis for simulation data results, receiving simulation result data through middleware, loading the result data into the visual scene simulation model, and conducting collaborative simulation.

[0047] A collaborative simulation method between the Modelica platform based on Opendds and UE4 includes the following steps:

[0048] Step 1: The simulation process of the OpenModelica secondary development software is as Figure 2 shown. After the Modelica physical simulation software finishes modeling, save the Modelica model to generate a Modelica model file (.mo file) in the specified path; set the simulation parameters, then call the simulation function to compile the Modelica model file to generate an executable file (.exe file), run the executable file through the execution module, output and display the simulation results, and transmit the simulation data to the middleware publisher node.

[0049] Step 2: The creation process of the data transmission channel based on the Opendds middleware is as Figure 2 shown. Opendds defines a service for participants to effectively transmit data in a distributed deployment program. This service is divided into two interface layers: the first layer is the DCPS layer (Data Centric Publish Subsribe, publish / subscribe centered on data), and the second layer is the DLRL layer (Data Local Reconstruction Layer, data local reconstruction layer). The DCPS layer matches the topics and QoS protocols of the publisher / subscriber end to transmit data from the publisher to the subscriber. The data writer transmits the simulation result data to the publisher (Publisher), and the data reader reads data from the subscriber (Subsribe);

[0050] Step 2.1: The publisher and subscriber configure the same domain value. In different domains, different programs on the same set of hosts or on the same host will be isolated from each other in communication and unable to transmit data. The API interface Creat_participant is used to configure the publisher and subscriber to be in the same logical communication network. Using a unified domain value enables DCPS to perform data exchange. Register the simulation transmission data type. The API interface DemoTopic1TypeSupportImpl is obtained through the custom data type in the IDL interface file. Call DemoTopic1TypeSupportImpl to configure the data type DemoTopic1 for the communication convention between the publisher and subscriber. Configure the topic corresponding to the registered data type. The API interface createtopic is used to create a topic. Write the name of the dynamically extended data structure in the function createtopic. Each topic in the domain must be customized with a specific name and correspond to the specific data type published by the publisher. The publishing process specifies the topic when publishing data, and the subscriber obtains the data by requesting the corresponding topic;

[0051] Step 2.2: Configure the Data Writer and Publisher. Call the API interfaces creat_publisher and creat_datawriter to create the Data Writer and Publisher respectively. The middleware publisher inherited by the simulation software passes data to Opendds through the Data Writer. Each Data Writer can only correspond to a specific topic. The publisher uses the Data Writer to specify the type interface and publishes data samples on the bound topic. The Data Writer first encodes the simulation transmission data and then passes it to the publisher for preparation for transmission. After the publisher obtains the data to be published, it passes it to all subscribers in the domain;

[0052] Step 2.3: Similar to Step 2.1 and Step 2.2, register the subscriber domain and data type. Configure the topic corresponding to the registered data type. The API interface create_typeless_topic is used to create a typeless topic. Write the name of the dynamically extended data structure in the function create_typeless_topic. Each topic in the domain must be customized with a specific name and correspond to the specific data type published by the publisher. The publishing process specifies the topic when publishing data, and the subscriber obtains the data by requesting the corresponding topic;

[0053] Configure a Data Reader and a Subscriber. Call the API interfaces creat_subsriber and creat_datareader to create a Data Reader and a Subscriber respectively. The Subscriber receives data from the Publisher and transfers the acquired data to all associated Data Readers. The subscriber side configures the recorder to listen for code through the function create_recorder, which is used to listen for dynamically extended data types and transfer the monitored data types to the subscriber; the Data Reader obtains data from the subscriber, decodes it into the corresponding topic data type, and finally transfers the data to the middleware subscriber node integrated with the UE4 scene;

[0054] Step 2.4: For the types of data that need to be transmitted, define and represent the data transmission service according to the interface description language to obtain the IDL file of the data definition and representation. In the IDL file, the "@" annotation is used to specify the data types required for transmission and processing by the Data Distribution Service (DDS). In order to generate the necessary C++ code for type support when generating the transmission data type, after the IDL is written, it is processed and compiled by the TAO IDL compiler and the Opendds IDL compiler, and finally mapped to the c++ type support file;

[0055] Step 2.5: Write the MPC file and perform MPC engineering processing to generate the VC project file. The content of the MPC file is as Figure 4 shown. Start running the executable files of the publisher and subscriber to start the transmission of dynamically extended data types. Configure the dynamically extended subscriber code as Figure 5 shown.

[0056] Step 3: Load the Opendds subscriber plugin in the UE4 scene, encapsulate the interface functions in the Opendds subscriber plugin as blueprint nodes, and the UE4 scene receives data by calling the subscriber node to simulate the physical model. The construction process of the UE4 ultra-large terrain map is as Figure 6 shown;

[0057] Step 3.1: In the UE4 external dynamic plugin module, the plugin module code is the subscriber code described in Steps 2.3, 2.4, and 2.5. Compile the subscriber code to obtain the middleware subscriber plugin module, which is automatically encapsulated as a visual blueprint node by UE4;

[0058] Step 3.2: Call the middleware subscriber plugin module node in the UE4 scene level blueprint, and the connection between UE4 and Opendds can be completed. The UE4 calls the blueprint node as Figure 7As shown in the figure. Among them, Event BeginPlay is the main function called by the blueprint. The OpenDDSPlugin Init node encapsulates the Opendds subscriber code and initializes Opendds. The node parameters Ptopic and S topic define the publish and subscribe topics respectively, and rtps is the definition of the transmission method. Set time by event is a dot timer that sets the output data interval time for the subscribed data. GetMSG Content is a custom event used to obtain the subscribed data from the subscriber side and transmit the data to the structure splitting node Break DDSmessage to split the structure for the data types required for scene calls. Print String is to print the received data;

[0059] Step 3.3: Comprehensively use software such as 3DS MAX, CATIA, UG, and World Machine to generate a simulation object model. The UE4 scene model format is FBX, and models in non-FBX format can be converted to FBX format through CAD Exchange software;

[0060] Step 3.4: Load the Cesium for unreal plugin in UE4 to load the digital earth for the UE4 scene and generate an ultra-large three-dimensional virtual space corresponding to the real simulation scene;

[0061] Step 3.5: Configure the camera perspective for the simulation object model to provide a multi-perspective and all-round simulation situation display for simulation researchers and a more intuitive and realistic judgment basis for the simulation data results. After loading the subscriber plugin and the Cesium for unreal plugin at the UE4 scene end and hanging the model simulation perspective camera, the entire simulation scene can be compiled, the UE4 scene can be started, and the visual simulation can be started.

[0062] In the simulation project of the embodiment, first load the digital earth. The UE4 scene calls the Opendds subscriber port plugin through the UE4 level blueprint node OpenDDSPlugin Init. The subscriber recorder receives the data sample function encapsulated in this node. By calling this node, the middleware can be used to transmit data in the scene. Further, import the aircraft model. To improve the simulation demonstration effect of the scene, multiple cameras are hung on the model. By splitting the simulation screen display, set multiple cameras with multiple perspectives to monitor the missile flight state in real time, Figure 8 The figure shows the main interface of the aircraft simulation project of the embodiment, Figure 9The simulation effects from different perspectives of the aircraft simulation process are shown. The Cesium digital earth is used for the project simulation scenario. 10-level tile maps are loaded on the digital earth, enabling simulation analysis for the global scene flight of the aircraft. The implementation results of the method of the present invention show that during the simulation process, the simulation result data of each group of aircraft can be completely received, and the data transmission delay can meet the requirements of scene display. During the entire simulation process of the aircraft's launch, takeoff, and accelerated flight, the flight coordinates match the geographical coordinates of the digital earth, and the heading angle matches the flight attitude, enabling a 0-error display of the model flight state and accurately reaching the flight end point from the flight starting point.

[0063] In summary, by linking the Opendds middleware with the UE4 simulation scenario, the Opendds technology simplifies the configuration process of various complex data transmission protocols. Through the data-centric publish / subscribe method, it greatly improves the flexibility of data transmission, making the linking process of multiple different software more convenient. Given the characteristics of this technology itself, Opendds is particularly suitable for the data transmission requirements in the simulation field where there are many data sources, large volumes of multi-source data, complex structures, and frequent transmissions. At the same time, Opendds supports dynamic data expansion at the publisher and subscriber ends. When facing changes in the types of simulation result parameter variables, regardless of how the publisher changes the data transmission type or increases the number and content of data transmission topics, the subscriber does not need to modify the code or compile the code twice, and the subscriber can successfully receive the dynamically expanded data types from the publisher.

[0064] On the UE4 scene side, the custom plugin module provided by UE4 makes it more flexible to load the Opendds subscriber. Without learning and modifying the underlying source code of UE4, the project requirements can be completed. UE4's powerful scene rendering ability has unparalleled advantages in building simulation scenes. For the rendering of natural scene effects such as simulation object models, super-large seamless terrain loading, and sky atmosphere lighting, compared with traditional simulation scene effects, UE4 scenes are more realistic and closer to the actual test scene effects. Therefore, by utilizing the distributed bridging capabilities of the Opendds middleware for various software, the co-simulation requirements between the Modelica platform and UE4 are realized. At the same time, this co-simulation system can effectively meet the requirements of the current visualization simulation platform for the display of simulation results by using UE4.

Claims

1. A co-simulation method for the Modelica platform and UE4 based on Opendds, characterized in that, it includes the following steps: Step 1: Use the Modelica platform to perform simulation modeling to obtain a model file in Modelica language; Parse the model file and convert it into simulation code in C / C++ language; Step 2: Use the publish / subscribe mechanism of the Opendds middleware. Take the Modelica platform as the publisher and the UE4 software as the subscriber, and generate the C / C++ language code for the publisher and subscriber respectively. Integrate the code with the Modelica platform and UE4 software respectively to establish a data transmission channel between the Modelica platform and UE4 software; Step 2.1: Configure the publisher and subscriber to the same domain value; Register the data types transmitted during the simulation process, and configure the data types of the communication convention between the publisher and subscriber; Configure the topics corresponding to the registered data types, customize specific names for each topic in the domain, and correspond to the specific data types published by the publisher; Step 2.2: Configure the data writer and publisher. The publisher passes the data to the Opendds middleware through the data writer. Each data writer corresponds to a specific topic. The publisher uses the data writer's specified type interface to publish data samples on the bound topic; After the data writer encodes the simulation transmission data, it passes it to the publisher for preparation for transmission. The publisher passes the data to be published to all subscribers in the domain after obtaining it; Step 2.3: Configure the topics corresponding to the registered data types at the subscriber end, customize specific names for each topic in the domain, and correspond to the specific data types published by the publisher; The subscriber obtains the data by identifying the topic name published by the publisher; Configure the data reader and subscriber. The subscriber receives the data from the publisher and transmits the obtained data to all associated data readers; Configure the listening code at the subscriber end to transmit the monitored data types to the subscriber; The data reader obtains the data from the subscriber, decodes it into the data type corresponding to the topic, and finally transmits the data to the middleware subscriber node integrated with the UE4 scene; Step 2.4: For the types of data that need to be transmitted, define and represent the data transmission service according to the interface description language to obtain an interface description language file for data definition and representation, and compile the interface description language file to map it to a c++ type support file; Step 2.5: Generate the executable files for the publisher and subscriber, and run the executable files for the publisher and subscriber to perform data transmission; Step 3: Establish a UE4 simulation scene, load the Opendds subscriber plugin in the simulation scene, and encapsulate the interface functions in the Opendds subscriber plugin as blueprint nodes. Call the subscriber in the UE4 simulation scene to receive simulation object data, and load the simulation object in the simulation scene; Load local resources, set the camera view of the simulation object, and start the multi-view visualization simulation of the simulation object.

2. The co-simulation method according to claim 1, characterized in that, Step 1 specifically includes: establishing a Modelica model using the Modelica platform, generating a Modelica model file at a specified path; converting the Modelica language in the Modelica model file into C / C++ language, and finally compiling and linking the converted C / C++ file and the publisher code file to generate an.exe executable simulation model; performing real-time simulation or offline simulation on the executable simulation model and outputting simulation result data.

3. The co-simulation method according to claim 2, characterized in that, Step 2 adopts the dynamictype standard of the Opendds middleware, enabling the publisher and subscriber to support dynamic data type extension. When the data type transmitted by the Modelica platform changes, the subscriber code of UE4 can receive the dynamically extended data from the publisher without recompilation.

4. The co-simulation method according to claim 3, characterized in that, In step 2.5, an MPC file is written and the engineering processing of the MPC file is carried out to generate the source code files of the publisher and subscriber.

5. The co-simulation method according to claim 4, characterized in that, Step 3 specifically includes: 3.1) Writing an Opendds subscriber plug-in module for the external dynamic plug-in of UE4, writing the Opendds subscriber source code into the plug-in and compiling it for use; 3.2) Invoking the Opendds subscriber plug-in module node in the level blueprint of the UE4 scene, linking each node in the blueprint editor, and compiling the blueprint for outputting the subscriber received data instance; 3.3) Using software such as 3DS MAX, CATIA, UG, and World Machine to generate a simulation object model and loading the simulation object model into the simulation scene; 3.4) Loading the Cesium for unreal plug-in in the UE4 software to load the digital earth for the UE4 simulation scene; 3.5) Configuring the camera view to provide users with a multi-view and all-round simulation situation display.

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