Embedded Matlab function, simulink loop

Hello.

I have been working with the matlab Embedded function in simulink and I have a problem. I am doing an on-off controller by adding many if statements like this:

if a>10
  a=-1;
else
  a=9;
end

In this case, a is an input and an output, so I need to feedback it. I have tried to feedback it by conect them directly, by using the workspace and using a Memory block, however I always get this warning:

"Found algebraic loop containing..."

The result is the simulation runs for some seconds but suddently it stops without a reason.

How can I solve this problem?

Thanks

Answer 1

[Kaustubha Govind]

How about if you insert a Unit Delay block in the feedback loop?

[Robinson Medina]

Hello.,

Thanks for your answer... I have tryed but it did not work, simulation is still unstable. Is there any command in the embedded Matlab Function block in simulink, that let me save a varible until the next sample time? That could solve my problem.

Regards

[Nicholas]

Have you considered using a persistent variable type?

http://www.mathworks.com/help/techdoc/ref/persistent.html

[Kaustubha Govind]

Robinson: Could you explain what you mean by "unstable" - did you mean in the context of controller dynamics? Did the error about algebraic loops go away though?

Nicholas' comment answers the rest of your question.