Convert variable-sized signal to fixed

I have a custom block (block on the right) that takes a fixed size signal, but I would like to adjust the size of the input signal as needed. The subsystem that is present 10 times in the photo below outputs a number if it's input is 1 or an empty signal if it is zero. Then I make the 10 signals into 1 using a bus selector. However, the output signal of the bus selector is of variable-size. Is there any way to convert a variable sized signal to fixed?

Answer 1

[Shlok]

Hi John,

I understand you're looking for an approach to convert a variable-sized signal into a fixed size. You can achieve this by using a “MATLAB Function” block. This block allows you to write custom MATLAB code within Simulink to perform calculations, control logic, or manipulate signals.

Within this function block, you can reshape the incoming signal, either by padding it with zeros or removing excess values to match the desired fixed size. This method allows you to manage the signal's dimensions dynamically and keeps a consistent output size for further processing in your Simulink model.

Here’s a sample code of the function:

% u: input signal (1-D Array) 
% fixedSize: size of output signal (Integer)  
function y = varToFixedSize(u, fixedSize) 
    y = zeros(fixedSize, 1); 
    inputSize = length(u); % Determine the size of the input signal 
    if inputSize <= fixedSize 
        y(1:inputSize) = u; 
    else 
        y = u(1:fixedSize); 
    end 
end

To know more about “MATLAB Function” block, you can refer to the following MATLAB documentation:

• https://www.mathworks.com/help/releases/R2020b/simulink/ug/what-is-a-matlab-function-block.html
• https://www.mathworks.com/help/releases/R2020b/simulink/ug/creating-an-example-model-that-uses-a-matlab-function-block.html