Averaging a signal at periodic intervals in Simulink
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Fargham Ahmad
on 15 Feb 2019
Answered: Fargham Ahmad
on 16 Feb 2019
I am trying to compute the average of a signal at periodic intervals. The signal is sampled at some rate say 0.1s, i want to compute avegare after every one second in simulink. I tried to integrate the signal over every second and then multipy it one second to get an avg value of signal. This method is not valid as the integraor is causing my function to blow up.
Please share any possible methods, Thanks.
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Jim Riggs
on 15 Feb 2019
In my mind, the easiest way to do this is to create a Matlab function to do it, and embed the function into a Matlab block in Simulink. It's a lot harder to do this kind of thing in Simulink because of the complex logic involved. (Stateflow helps a lot)
Make a matlab function that stores the signal in a circular buffer. Once you have enough samples in the buffer, you can output the average value over the N=10 samples. You can make the code so that it only outpus a new value every 1 second, or it can output every 0.1 s. (i.e. a "sliding average" ) using the 10 most recent samples.
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Jim Riggs
on 16 Feb 2019
Edited: Jim Riggs
on 16 Feb 2019
Here is a sample output for a linear ramp test case:
This is a 0.1 sample rate, Navg = 10 and Nout = 10.
This is for Navg = 10 and Nout = 5
And this one is Navg = 10 and Nout = 2
Notice how they all have a 10 sample delay at the start.
Notice also that this test case runs at 0.1 time step for 10 seconds, and therefore generates 100 calls to the WindowAverage function. I set the buffer size to 50 in the function to verify that it wrapped correctly back to the start when it reaches the end.
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