Transport Delay of Zero

I have the following block diagram.

My step input is set to 1000 sec. By changing the TM value in the I'm attempting to get the following graph. One with tm=1000 and the second with tm= 0. This is the graph I'm supposed to get for the block without preditictive control.

Instead this is what I'm getting

I'm getting an error when I set the transport delay to zero, it says that there maybe an algrebraic loop. Any idea how I might fix this?

[Jade O'Connor]

It should work if you move the time delay block into the feedback loop :)

[Robert U]

Hi Jade,

Your suggestion probably does not work, either, when setting the time delay to Zero.

Kind regards,

Robert

Answer 1

[Robert U]

Hi Shane Cheshire,

There is plenty of hints in Matlab documentation on how to fix algebraic loops. Most conveniant is to introduce a unit-delay block that will delay the feedback signal by one time step. That usually does not have any significant impact on the simulation result.

Doc: Remove Algebraic Loops

Another option is to use very small signal delay times. But this option might increase simulation time dramatically.

Kind regards,

Robert