How to avoid algebraic loops in model?

I want to avoid algebraic loop in my model. My model is running in discrete time step with step size of 100usec. To avoid loop I tried using unit delay which resulted in unexpected results. so using delay is not an option for me. Also tried using IC block from simulink library for initializing the signal value but unable to avoid any loop. Please suggest some ways to avoid algebraic loops an discrete time system.

Answer 1

[Ryan G]

Here are some good tips for algebraic loops:

Causes of Algebraic Loops

Fixing Algebraic Loops

If you are running a fully discrete model you can explicitly set all the sample times too 100 usec, run the model at a faster rate and set the unit delay to that faster rate so the data will be available at the beginning of the next time step. Not 100% sure how well that will actually work though.

[ANKIT]

Hi Ryan, Thanks for your reply. My model is running in a Triggered subsystem with frequency of 10KHz(100usec), so I am not able to explicitly set sample times to 100usec as it allows only sample time of -1(inherited) or inf. I am looking for some option other than using unit delay.

[TAB]

Can you attach the snapshot of part of the model causing algebric loop ?

[ANKIT]

Hey Tab, I am not getting any option to upload a snapshot.Can u just guide me how it can be done?

[TAB]

@ANKIT

Upload your picture on any image hosting website (like tinypic.com) and link the image in your question, comment or answer(see markup help).

Answer 2

[Khim Chhantyal]

Hi,

I have the similiar problem.

I can avoid algebriac loop using both "Initial condition" block and "unit delay" block.

However, using unit delay, the system response is different AND unfortunately, I can only build an .exe file by using unit delay option.

For .exe file, initial condition block does not remove algebriac loop. :(

Can you please help me with this?

Thanks.

-Khim