How to get around algebraic loop issue ?

[prebasha]

Hi all,

I'm not a power user of Simulink but have started using it for a while now. I'm doing a Vehicle Dynamics simulation and stuck with an algebraic loop issue. I have so far tried following things :
1) Reducing step size.
2) Tightening error.
3) Unit delay and memory block ( though I doubt I know how to use them efficiently)

It would be great if somebody can explain algebraic loops in general and suggest tips to fix that.
Thanks.

PS:
-Use m=8 in Matlab workspace to run the model.

 

[FeX32]

That usually means you system is unstable. Common problem.
I increased the mass to 1000, and right away the error disappeared.
What exactly are you simulating?


Fe

 

[prebasha]

Thanks Fe,

I'm doing a Vehicle Dynamics simulation, which basically calculates slip angle and feed again to calculate new one. If you wish I could give some more details ( I've attached my model the first time)

Let me know. Need help ASAP
Thanks.

-Prebasha

 

[prebasha]

Sorry !!

Didn't read your reply carefully. I've limitation over mass, can not increase to any value. I have set of values which are in constant units and does not have much room to play around with those numbers. It would be great if you can explain what is exactly happening here, and what care I should take while modeling such systems, right here and in future.

Thanks.
-Pre

 

[GregLocock]

Two suggestions for algebraic loops. Either recast the problem to eliminate them, or insert a unit delay or memory block into the loop. The latter WILL affect the dynamics of the sim.



Cheers

Greg Locock


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