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I am seeking a method to sum multilevel bus signals
at the lowest level within their hierarchy
without loss of the bus signal structure.

MWE

For example, in the MWE below,
the bus signal is summed at the lowest level automatically,
however, the bus signal is lost after passing through the Add block.

A vector signal is produced instead.

MWE

I would have preferred a method which yields:

red + blue = purple

or more specifically:

red.[a b c].[1 2] + blue.[a b c].[1 2] --> purple.[a b c].[1 2]

where

purple.b.3 = red.b.3 + blue.b.3

and so forth.

kando
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1 Answers1

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To my knowledge, the only possibility to do math with bus signals is using a MATLAB Function block. Be aware of the potentially bad performance!

To use a MATLAB Function block, first generate a matching bus object and make sure the two bus creators mergin a / b / c each are assigned to output this bus object. Doing so you will receive an error because 1 and 2 aren't valid field names, i changed them to x1 and x2.

In the next step create a MATLAB Function Block. Set the two inputs and one output to your previous defined bus object. Paste the following code:

function y = fcn(u, v)
%#codegen

y.a=innerplus(u.a,v.a);
y.b=innerplus(u.b,v.b);
y.c=innerplus(u.c,v.c);
end

function y=innerplus(u,v)
y.x1=u.x1+v.x1;
y.x2=u.x2+v.x1;
end

enter image description here

Daniel
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  • This is a helpful start. I didn't realize that the bus structures could be interpreted in the Matlab environment as structure type elements. Your example is specific to a certain size; I'll ask how to add the structures in a separate question and provide the link below. – kando Mar 07 '16 at 20:12
  • @kando: It is covered in the documentation (http://www.mathworks.com/help/simulink/ug/attach-bus-signals-to-matlab-function-blocks.html). If anything is unclear feel free to ask a question, but I think that should explain it. – Daniel Mar 07 '16 at 20:15