Generate and Simulate Standalone FMU in Simulink

Simulink FMU Builder enables you to generate FMUs from your Simulink models and C/C++ code. You can generate Co-Simulation and Model Exchange FMUs that are compatible with FMI 2.0 and 3.0 standards. To learn about FMI and FMU concepts, see Functional Mockup Interface Concepts.

Comparison of FMU with Simulink Alternatives

FMUs provide a way to package your system components into standalone units. Simulink provides alternatives for generating standalone packages from Simulink models or C/C++ code. You can use protected models to generate a standalone package from Simulink models and C MEX S-function to generate standalone S-functions from C/C++ code.

General considerations

This table provides general considerations for choosing a tool to generate your standalone package.

Working Environment	Simulink Model	C/C++ Code
Requires Interoperability	Model to FMU	Code to FMU
Used only in Simulink	Protected Model	C MEX S-Function

Generate Ready-to-run Packages for Simulink Models

You can use FMUs or protected models to generate standalone packages from your Simulink models. Use FMUs when you need interoperability with other tools and plan to share the package outside Simulink. Use Simulink protected models when you are modeling, generating, and integrating the components in the Simulink environment and interoperability with other tools is not required. This table provides a detailed comparison between FMU and protected models.

Feature	FMU	Protected Model
Tool compatibility	Tool-independent	Simulink only
Multi-platform	Yes; can package multiple binaries	No; single-platform
Bus interface	Supports non-virtual busses only	Full bus support
Advanced Simulink Semantics (for example fixed-point, Simscape solver)	Limited	Full compatibility
Simulation fidelity	High for Model Exchange; solver and importer dependent for Co-Simulation	High
Intellectual property protection	Protected by compilation (binary files)	Protected by encryption, (password protection), compilation (binary), and obfuscation (source code)
Debugging capability	Signal and source-code based debugging	Hidden model details

Generate Ready-to-run Packages for C/C++ Code

You can use the Code to FMU tool or a C MEX S-function to generate standalone units for your C/C++ code. Use FMUs when you need interoperability with other tools and to share the package outside Simulink. Use a C MEX S-function when you are modeling, generating, and integrating the components entirely within the Simulink environment. This table provides a detailed comparison between FMU and C MEX S-functions.

Feature	FMU	C MEX S-Function
Tool Compatibility	Tool-independent	Simulink only
Multi-platform	Yes; can package multiple binaries	No; single-platform
System Composer integration	Yes	No; can be included in Simulink Subsystem or Model Reference
Fixed-point compatibility	No	Yes
Simulation fidelity	High for Model Exchange; solver and importer dependent for Co-Simulation	High
Modeling and integration complexity	Moderate	Complex

You can generate Co-Simulation or Model Exchange FMUs for both Simulink models and C/C++ code. To learn more about these FMU types, see FMU Types: Co-Simulation and Model Exchange.

Co-Simulation FMU Solvers: Fixed-Step and Variable-Step

A Co-Simulation FMU that contains both the model and solver can use either a fixed-step or variable-step solver. A fixed-step FMU can run independently of the original modeling environment and does not require additional runtime dependencies. A variable-step co-simulation FMU that is generated from Simulink offers limited Simulink semantics support, does not support cross-compilation, and depends on the MATLAB Runtime (MCR) to execute. As a result, variable-step FMUs are less portable and require the target environment to have the necessary runtime libraries installed.

Feature	Fixed-Step FMU	Variable-Step FMU
MATLAB Runtime	Does not require MATLAB Runtime	Requires MATLAB Runtime
Cross-platform compilation and simulation	Yes	No
Cross-release simulation	Yes	No
`FMUState` support	Yes	No
Windows 32-bit DLL	Yes	No
Multi-Instance support	Yes	No

Generate FMUs in Simulink

Simulink FMU Builder and Simulink enable you to generate FMU from Simulink models or C/C++ and simulate these in the Simulink environment. Simulink FMU Builder supports generation of FMUs compatible with the FMI 2.0 and FMI 3.0 standards.

For a simple workflow demonstration of generating FMU from your Simulink model, see Generate a Basic Standalone FMU from Simulink Model.
To learn how to generate FMU using your C/C++ code, see Generate a Basic Standalone FMU from C/C++ Code.

Import and Simulate FMUs in Simulink

Simulink provides a wide range of features that enhance the usability and integration of FMUs within its environment. Through support for FMI standards and integration with native Simulink capabilities, you can incorporate FMUs into a model development workflows for simulation, verification, and deployment. This enables FMUs to function as integral components within Simulink based systems, supporting a range of development and testing activities. For more information, see Import, Test, and Simulate FMUs in Simulink.