Represent Simulink Integrator block as Matlab Function

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River Rock
River Rock 2012-12-4
评论： Edward Rodriguez 2020-8-10
Hi.
I need to implement the following behavior :
The Integrator and my_Integrator blocks have to be equivalent I/O.
How should I write the Matlab Function ?
Thanks for any reply.

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采纳的回答

Ryan G
Ryan G 2012-12-4
As this looks like a homework problem, I can't answer directly. However I will point you in the direction of persistent variables.

更多回答（4 个）

Azzi Abdelmalek
Azzi Abdelmalek 2012-12-7
编辑：Azzi Abdelmalek 2012-12-8
I don't know why do you need this, maybe if you explain exactly what you need, there is better way
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Azzi Abdelmalek
Azzi Abdelmalek 2012-12-8
编辑：Azzi Abdelmalek 2012-12-8
Ok, I see, If T is constant, you must then set, in model configuration parameters your fixed step time to T, and also your step block sample time to T. In this case you don't need a clock.
function y = fcn(u)
persistent uold yold
T=0.01;
if isempty(uold)
uold=0;yold=0;
end
y = u*T+yold-(u-uold)*T/2
yold=y;uold=u;
River Rock
River Rock 2012-12-8
Changing the sample time of the Step block to 0.01 removed the previous offset. Thanks

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Guy Rouleau
Guy Rouleau 2012-12-5
This is not a good idea. The MATLAB function is not designed for this purpose.
  1 个评论
Edward Rodriguez
Edward Rodriguez 2020-8-10
Excuse me, so, What would be a good idea to implement numerical integration methods in blocks in Simulink?

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River Rock
River Rock 2012-12-5
编辑：River Rock 2012-12-6
My main goal is to implement the differential equations of a physical system using a single Matlab Function. As the sums and gains were easy to represent, I couldn't find any alternative for the integration.
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Ryan G
Ryan G 2012-12-5
What you have written is close it would be more like:
y(z) = yOld+u(z)/SampleTime
You cannot use the ODE solver in the MATLAB function block.
River Rock
River Rock 2012-12-7
Any idea on how to get rid of this offset ?
http://i.imgur.com/cxr5H.png
Code looks like:
function y = fcn(u)
%#codegen
T=0.01;
persistent yOld;
persistent uOld;
if (isempty(yOld))
yOld = 0;
end
if (isempty(uOld))
uOld = 0;
end
y = yOld + (T/2)* (u + uOld);
%y=yOld + u*T;
yOld = y;
uOld = u;

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River Rock
River Rock 2012-12-5
Can anybody suggest a better way of implementing the numerical integration ? The code has to be written inside the Matlab Function Block though.

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