Algebraic Loop Journey of Understanding

I seem to have introduced an algebraic loop into my model by adding an enable port and a supervisor block to start the model when certain conditions are met. When I debug it seems that the only algebraic loop is through the input and output ports of the enabled block and the enable port itself, rather than any details of the enabled block. Can anyone comment on why it would behave that way?

Answer 1

[Jarrod Rivituso]

Adding an Enable port to a subsystem makes the subsystem Atomic, so Simulink has to treat the internal contents of the subsystem as indivisible (enable Format -> Block Displays -> Sorted Order to see what I mean).

This has a consequence that sometimes "ghost" algebraic loops are created. Here's a great blog post on the issue:

http://blogs.mathworks.com/seth/2008/07/03/how-did-i-get-an-algebraic-loop-error-when-the-diagnostic-was-set-to-warning/

I would recommend trying what the blog suggests

1. Right-click the subsystem
2. Enable the Mimize Algebraic Loop Occurences option
3. Try simulating again

Good luck!

[Jarrod Rivituso]

ps - Seth I think you should vote my answer up cause I referenced your blog :)