Represent Simulink Integrator block as Matlab Function

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River Rock 2012-12-4

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评论： Edward Rodriguez 2020-8-10

采纳的回答： Ryan G

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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Azzi Abdelmalek 2012-12-4

What is your goal?

River Rock 2012-12-5

Please see http://www.mathworks.com/matlabcentral/answers/55705#answer_67551

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Ryan G 2012-12-4

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

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Azzi Abdelmalek 2012-12-7

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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 2012-12-8

编辑：Azzi Abdelmalek 2012-12-8

在 MATLAB Online 中打开

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 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 2012-12-5

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This is not a good idea. The MATLAB function is not designed for this purpose.

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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 2012-12-5

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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 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 2012-12-7

在 MATLAB Online 中打开

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;