Simulink is a graphical control design environment. However, it has the ability to include MATLAB, textual-based, algorithms as part of the model. For some design problems, this is the best approach. In today’s post, I’m going to review the three primary methods for including MATLAB code in your Simulink Model.
Function / Class / System Object
There are three methods for including MATLAB code into Simulink Models; a function, MATLAB classes, or MATLAB Simulink System Objects.
|Generates C code||X||X||X|
|Supports calls to external files||X||X||X|
|Object Oriented Code||X||X|
|Built-in I/O validation routines||X|
|Built-in state save / restore methods||X|
The Class and System Objects provide functionality that is not built into the Function method. However, both require additional knowledge of how to program. A MATLAB function can be written as a simple set of equations while the Object Oriented methods require some base level programing knowlege.
And state data: memory
For models that are targeting Code Generation there is an additional consideration, memory usage. State data, or dWork data in the generated code is used for any variable that is required to be held in memory between time steps. With a MATLAB function the user can explicitly define the variables that are State Data by using the “persistent” keyword.
With the MATLAB class or MATLAB System Object, any data that is defined as a property will be stored as a dWork variable regardless of the need for a state variable. The number of state variables can be decreased in the Class implementation; however in doing so, much of the benefit of the class based approach is lost.