I'm trying to do simple averaging in Simulink and need some help with it.

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Assume AI'm acquiring a noisy signal at 1 mS interval and I want to get 1 point every 50 mS. I would like to collect the data for the 50 mS and spit out an average for logging. I'm not sure how to do it.
Any simple solutions would be appreciated.

Accepted Answer

Alexander Bottema
Alexander Bottema on 9 Nov 2011
function y = my_average(u) %# codegen
persistent i buf bufSum;
if isempty(buf)
buf = zeros(1,50);
bufSum = 0;
i = 1;
end
bufSum = bufSum - buf(i);
buf(i) = u;
bufSum = bufSum + u;
i = i + 1;
if i > numel(buf)
i = 1;
end
y = bufSum / numel(buf);
  2 Comments
Guillermo
Guillermo on 9 Nov 2011
It seems to have worked. It generates a warning at every iteration but I can live with that.
Thank you,

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More Answers (4)

Fangjun Jiang
Fangjun Jiang on 9 Nov 2011
Use the "Weighted Moving Average" block from Simulink>Discrete, click help for details.
  2 Comments
Fangjun Jiang
Fangjun Jiang on 9 Nov 2011
Hah, it is obsolete! http://www.mathworks.com/help/toolbox/simulink/ref_obsolete_blocks/weightedmovingaverageobsolete.html
Use the new Discrete FIR Filter, http://www.mathworks.com/help/toolbox/simulink/slref/discretefirfilter.html

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Walter Roberson
Walter Roberson on 9 Nov 2011
Feed the signal in to an integration block that is reset to 0 every 50 samples; take the 50th output and divide it by 50 to get the average for that period.
There might be a cleaner way to only trigger the output collection every 50 outputs and tie that in to the integration block being cleared right afterwards.
  1 Comment
Guillermo
Guillermo on 9 Nov 2011
I would like to try this, but I'm not yet very familiar with simulink. How do it set up the integration block?
The initial condition is set to 0, how about the saturation limits? and the Ignore limit and reset when linearizing check box?
Thanks again,

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Guillermo
Guillermo on 9 Nov 2011
I got my code to work too, thanks to the sample by Alexander. The two codes give the same result and I'm not sure either which is more efficient. I tried passing the number of elements n to acquire so that I can pass a number of points to average but got an error...
function y = fcn(u)
%#codegen
persistent i n buf;
if isempty (buf)
i = 0;
n = 50;
buf = NaN(50,1);
end
buf = circshift(buf, [1,1]);
buf(1) = u;
n = numel(~isnan(buf));
y = sum(buf)/n;

Martin Murtagh
Martin Murtagh on 23 Mar 2021
I have replaced the moving average block in my models with the subsystem shown. By setting the delay length to the moving average value divided by the time-step and the gain value to one over the moving average value, this subsystem will calcuate the moving average in the same way as the moving average function with a sliding window.

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