Error while using function block in simulink

Hi, For a large system i'm trying to simulate i had to write specific code as block in simulink. for simplicity i first tried to do the following simple task (the real function is more complicated but as a sainity check):

But i get the following error:

I would really appriciate any help.

Answer 1

[Sebastian Castro]

This is an algebraic loop, which means that the output of the block depends directly on the input.

In this case, y cannot be computed without knowledge of u -- both of which refer to the same signal. As the error messages say, this is not valid.

If it makes sense given your modeling requirements, I would recommend using a Unit Delay block in the loop. This delay will change the equations from:

y = u (AT THE CURRENT TIME STEP) + randn(1,2); % Does not work

to:

y = u (AT THE PREVIOUS TIME STEP) + randn(1,2); % Will work

Just make sure the Unit Delay block is sampled at the rate you want by setting its sample time parameter.

- Sebastian

[shahar lutati]

Thank you !