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How to iterate in simulink?

Asked by Daniel

Daniel (view profile)

on 10 Nov 2013
Latest activity Commented on by Daniel

Daniel (view profile)

on 11 Nov 2013

Hi,

I have the following problem, I want to iterate two variables in Simulink. In normal code it would look like this:

X(i+1)=X(i)+4*(X(i)-Y(i));
Y(i+1)=Y(i)+2*(X(i)-Y(i));

I used For Iterate Block but it doesn't work. I'm getting an error:

"Trouble solving algebraic loop containing 'untitled/For Iterator Subsystem1' at time 0. Stopping simulation. There may be a singularity in the solution. If the model is correct, try reducing the step size (either by reducing the fixed step size or by tightening the error tolerances)."

Here's what i have done in Simulink

0 Comments

Daniel

Daniel (view profile)

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1 Answer

Answer by Azzi Abdelmalek

Azzi Abdelmalek (view profile)

on 10 Nov 2013
Edited by Azzi Abdelmalek

Azzi Abdelmalek (view profile)

on 10 Nov 2013
Accepted answer
% x(i+1)=x(i)+4*(x(i)-y(i));
% can be written as
% x(i+1)-5x(i)=-4y(i)
% z X(z)-5X(z)=-4Y(z)
% H(z)=-4/(z-5)
To get the result you can use a discrete transfer function with 
numerator=-4
denominator=[1 -5]
% input signal=y
% output signal x

3 Comments

Daniel

Daniel (view profile)

on 10 Nov 2013

Thanks, that helped me. I have one more question, how do I include initial conditions x(1)=400 and y(1)=100?

Azzi Abdelmalek

Azzi Abdelmalek (view profile)

on 11 Nov 2013

set initial values of your unit delay block to 400 and 100

Daniel

Daniel (view profile)

on 11 Nov 2013

thanks one more time, that is what i was looking for.

Azzi Abdelmalek

Azzi Abdelmalek (view profile)

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