This paper studies the method of calling Matlab function in Simulink model.

1 Matlab Function module

When modeling in Simulink, sometimes you find that the functions you want cannot be realized by conventional modules and subsystems in Simulink, but can be easily realized by Matlab functions. In other words, some toolkits can be called through Matlab, but there is no such function in Simulink, but I want to implement this function in the model.

For the above problems, you can use the Matlab Function module in Simulink, and then write the Matlab code in the module. In this way, Matlab functions can be called through the Simulink model.

2 Modeling and code generation

This chapter demonstrates the modeling of Matlab Function module through examples of Pythagorean theorem.
1) Open Simulink and drag out a Matlab Function module. Double-click the module to enter, you can see that there is already a function definition named fcn inside.

2) Modify the function to the Pythagorean theorem calculation in the figure below.

In the Matlab function c = gougu(a,b), a and b are equivalent to the input of the subsystem, and c is equivalent to the output of the subsystem.

3) Click Edit Data in the upper right corner to edit the input and output attributes. Here change the input and output data types to single. It is equivalent to the type of Inport and Outport in Simulink subsystem.

4) Save and close the function editing window, add the input constant and disp module to the model, then run the model and observe the output result. Note that since the input and output data types are defined in the function, single constants must be input to the external signal interface.

5) To generate the verification code, replace the input end with Inport and the output end with Outport and configure the code generation (refer toSimulink code generation (a) Embedded Coder configuration）。

6) Ctrl + B generates code. The C code of the Pythagorean theorem is implemented in the generated step function.

3 Data management in Matlab Function

3.1 Associate Signal Object

In Edit Data, you can configure the Signal object in the input and output associated data dictionary.
1) Check Data must resolve to signal object in Ports and Data Manager.

2) Create a new Signal object in the Matlab workspace, and configure the type and StorageClass as follows.

3) Ctrl + B generates code. You can see that the c variable is defined in data.c.

3.2 Establish the parameters in the function

1) Click Add–>Data in Ports and Data Manager to create a new parameter.

2) Change the Name of the parameter to d, Scope to Parameter, and Type to single.

3) Create a new constant d=single(0.1) in the Matlab workspace.

4) Change the code in Matlab Function to open the radical and multiply by d.

5) Ctrl + B generates code. As can be seen from the code, the step function inlined the parameter d.

4 Limitations of Matlab Function code generation

Matlab Function has many restrictions on code generation, such as not supporting dynamic memory allocation and cell arrays.

In addition, there are many matlab functions and toolkits that cannot generate code. For details, please refer to the help file in the upper right corner of Matlab Function.

5 Summary

The use of the Matlab Function module allows Simulink to integrate Matlab functions, but it is better to use other Simulink modules to build control strategies and use less Matlab Function modules. Because the readability of Matlab Function is not friendly, and the generated code has many restrictions.

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