Subsystem References is new functionality to Simulink, it is only supported since R2019b. So industry will only slowly evolve to using the functionality.
I will try to explain use-cases for using Subsystem Reference, and contrast it with Model Reference. Both are saved into their own .slx file, and are referenced by a parent model. The difference is that with Model Reference, the signal interfaces are fixed, such as data types and signal dimensions. With a Subsystem Reference, these interfaces do not need to be fixed. Look at this documentation page. You can use a Subsystem Reference in multiple instances where one instance receives a scalar while another instance receives a vector signal. This is similar to using a library block: the same library block can be used for different instances with different signal dimensions or data types. A Model Reference only accepts signals of a fixed data type and dimensions.
Besides this, a Model Reference can have its own Configuration Parameters and Model Workspace, while a Subsystem does not have it and inherits this from the parent model.
I would say that a Subsystem Reference is more closely related to a library subsystem, with the advantage that:
- The subsystem is inside its own .slx file, which can be versioned through GIT. This means a different team member can develop this subsystem reference inside the .slx file without disturbing other systems. If you do this with a library, the whole library will be affected.
- A subsystem reference can be tested and developed inside a harness.
In a model-based design project, I would say typically a Model Reference is used for:
- A controller
- A plant model
which are then referenced in harnesses for:
- Code generation
- Real-time prototyping
- Simulation
while Subsystem References are used for:
- Speed controller subsystem inside the controller
- Position estimator subsystem inside the controller
- ...
- Induction motor model inside the plant model
- Synchronous motor model inside the plant model
- ...
This link also provides a comparison overview.
