Why do i keep get the message "Index expression out of bounds" ?

I'm simulating a sliding-mode controller with Simulink. Some function in my subsystems keep getting the message "Index expression out of bounds". I have 4 signal go into the mux block, so it supposes to be ranged from 1 to 4 but in the diagnostic viewer said the range is 1-1.

Answer 1

[Abhaya]

Hi Hung,

I encountered a similar issue when using a Simulink ‘Mux’ block alongside a ‘MATLAB Function’ block. The error occurs because the Simulink Mux block outputs a virtual vector, which the ‘MATLAB Function’ block processes as individual double values. To resolve this error, you can set a fixed size for the input to the ‘MATLAB Function’ block.

Follow these steps to address the issue:

1. Open the ‘MATLAB Function’ block within your model.
2. In the ‘Function’ tab, select the 'Edit Data' icon.

3. In the ‘Symbol pane’ at the bottom left corner, click on the 'u' variable.

4. In the Property Inspector, set a fixed size for the variable 'u'.

To explore more about Simulink ‘Mux’ block, please refer to the following MATLAB documentation.

https://www.mathworks.com/help/releases/R2020b/simulink/slref/mux.html

Hope this resolves the issue.