Understanding FMU Generation

Oct 13, 2025 by talynt.org 60 views

Introduction

Functional Mock-up Units (FMUs) are a crucial component in model exchange and co-simulation, enabling the integration of complex models from various sources into a unified simulation environment. However, generating FMUs from OpenModelica (OM) can be a challenging task, especially when dealing with models that have unspecified start values. In this article, we will delve into the issues surrounding FMU generation, specifically when using OpenModelica v1.24.0 with ThermoSysPro, and explore strategies for overcoming these challenges.

Understanding FMU Generation

FMU generation involves converting a model from a specific modeling environment into a standardized format that can be exchanged and simulated across different platforms. The Functional Mock-up Interface (FMI) standard provides a set of guidelines for creating FMUs, which can be used for model exchange, co-simulation, or even standalone simulation. However, the process of generating FMUs can be complex, especially when dealing with models that have unspecified start values.

Challenges in FMU Generation

When generating FMUs from OpenModelica, several challenges can arise, particularly when dealing with models that have unspecified start values. These challenges can be attributed to the following reasons:

Unspecified start values: In some cases, the start values of model parameters may not be specified in the xml modelDescription, even though they exist in the OM model. This can lead to errors when simulating the FMU or loading start values.
Incomplete modelDescription: The xml modelDescription may not contain all the necessary information, such as start values, units, or min/max values, which can cause issues during FMU generation.
Inconsistent model structure: The model structure may not be consistent across different models, leading to difficulties in generating FMUs that can be exchanged and simulated seamlessly.

FMI Options in OpenModelica

To generate FMUs from OpenModelica, several FMI options can be configured:

FMI version: The FMI version can be set to 2.0, which is the latest version of the standard.
Model Exchange or Co-Simulation: The model exchange or co-simulation option can be selected, depending on the desired use case.
Name and File path: The name and file path of the FMU can be specified, ensuring that the FMU is saved in the correct location.
Native Platform: The native platform can be set to win64, which is the 64-bit version of the Windows operating system.
Source Code included: The source code can be included in the FMU, which can be useful for debugging and customization purposes.

DynamicDrum_CC Model

The DynamicDrum_CC model is a complex model that has several Real Output and RealInput parameters, some of which are connected to sensors. The start values of the input parameters are specified in the xml modelDescription, but a majority of the parameters do not have a start value specified. This can lead to errors when simulating the FMU or loading start values.

Overcoming Challenges in FMU Generation

To overcome the challenges in FMU generation, several strategies can be employed:

Specify start values: Ensure that all model parameters have start values specified in the xml modelDescription.
Complete modelDescription: Ensure that the xml modelDescription contains all the necessary information, such as start values, units, or min/max values.
Consistent model structure: Ensure that the model structure is consistent across different models, making it easier to generate FMUs that can be exchanged and simulated seamlessly.
Use FMI options: Configure the FMI options in OpenModelica to ensure that the FMU is generated correctly.
Debug and customize: Use the source code included in the FMU to debug and customize the model, if necessary.

Conclusion

FMU generation is a complex process that requires careful attention to detail. By understanding the challenges in FMU generation and employing strategies to overcome these challenges, developers can create high-quality FMUs that can be exchanged and simulated seamlessly across different platforms. In this article, we have explored the issues surrounding FMU generation, specifically when using OpenModelica v1.24.0 with ThermoSysPro, and provided strategies for overcoming these challenges.

Future Work

Future work in FMU generation should focus on developing tools and techniques that can automatically generate FMUs from complex models, reducing the manual effort required in the process. Additionally, research should be conducted to improve the consistency of model structure across different models, making it easier to generate FMUs that can be exchanged and simulated seamlessly.

References

[1] Functional Mock-up Interface (FMI) Standard, Version 2.0.
[2] OpenModelica User Manual, Version 1.24.0.
[3] ThermoSysPro User Manual, Version 1.0.

Appendix

The following appendix provides additional information on FMU generation, including:

FMU generation workflow: A step-by-step guide to generating FMUs from OpenModelica.
FMI options in OpenModelica: A detailed explanation of the FMI options available in OpenModelica.
DynamicDrum_CC model: A detailed description of the DynamicDrum_CC model, including its parameters and connections.
FMU Generation: Q&A =====================

Q: What is an FMU, and why is it important in model exchange and co-simulation?

A: An FMU (Functional Mock-up Unit) is a standardized format for models that can be exchanged and simulated across different platforms. It is a crucial component in model exchange and co-simulation, enabling the integration of complex models from various sources into a unified simulation environment.

Q: What are the main challenges in FMU generation, and how can they be overcome?

A: The main challenges in FMU generation include unspecified start values, incomplete modelDescription, and inconsistent model structure. These challenges can be overcome by specifying start values, completing the modelDescription, and ensuring consistent model structure.

Q: What are the FMI options available in OpenModelica, and how can they be configured?

A: The FMI options available in OpenModelica include:

FMI version: The FMI version can be set to 2.0, which is the latest version of the standard.
Model Exchange or Co-Simulation: The model exchange or co-simulation option can be selected, depending on the desired use case.
Name and File path: The name and file path of the FMU can be specified, ensuring that the FMU is saved in the correct location.
Native Platform: The native platform can be set to win64, which is the 64-bit version of the Windows operating system.
Source Code included: The source code can be included in the FMU, which can be useful for debugging and customization purposes.

Q: What is the DynamicDrum_CC model, and what are its parameters and connections?

A: The DynamicDrum_CC model is a complex model that has several Real Output and RealInput parameters, some of which are connected to sensors. The start values of the input parameters are specified in the xml modelDescription, but a majority of the parameters do not have a start value specified.

Q: How can I debug and customize the FMU, if necessary?

A: The source code included in the FMU can be used to debug and customize the model, if necessary. This can be done by modifying the source code and re-generating the FMU.

Q: What are the future directions for FMU generation, and how can they be improved?

A: Future directions for FMU generation include developing tools and techniques that can automatically generate FMUs from complex models, reducing the manual effort required in the process. Additionally, research should be conducted to improve the consistency of model structure across different models, making it easier to generate FMUs that can be exchanged and simulated seamlessly.

Q: What are the references for FMU generation, and how can they be accessed?

A: The references for FMU generation include:

[1] Functional Mock-up Interface (FMI) Standard, Version 2.0.
[2] OpenModelica User Manual, Version 1.24.0.
[3] ThermoSysPro User Manual, Version 1.0.

These references can be accessed through the OpenModelica website or by contacting the authors directly.

Q: What is the appendix for FMU generation, and what does it contain?

A: The appendix for FMU generation contains additional information on FMU generation, including:

FMU generation workflow: A step-by-step guide to generating FMUs from OpenModelica.
FMI options in OpenModelica: A detailed explanation of the FMI options available in OpenModelica.
DynamicDrum_CC model: A detailed description of the DynamicDrum_CC model, including its parameters and connections.

This appendix provides a comprehensive overview of FMU generation and can be used as a reference for further research and development.