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vlehner1-Visitor
1-Visitor
June 12, 2017
Solved

Solve-Block-Solution: non linear EQN-System

  • June 12, 2017
  • 2 replies
  • 5886 views

Hi!

Maybe today it is much too hot and I have drunk too little water and coffee, but i can't find a stable solution for a defined problem:

I have to solve a mechanical problem (dimensioning steel cables) with the solve block including 18 equations with 18 unknowns:

It is required that the length change, the number of threads and all forces, etc. are calculated with the solver.


Please see the sketch (you can doubleclick the .exe file to view it, it's an e-drawing file) and worksheet in attach.


The Problem is: I have as many equations as unknowns and when i change the guess values, i get always different results.

Are my equations right, and do i define something double or contradictory?


Any help will be appreciated.

Thank you very much for your efforts.

Volker

Best answer by DJF

I believe you have not formulated it correctly.  If you get multiple answers that usually means there are multiple answers.  Mathcad stops as soon as it finds one solution.  Running a quick check of your results shows that all of the constraints are solved properly with your results.  Maybe TOL or CTOL would make a difference, but I doubt it.  Check the results to see what isn't making sense.

check.png

2 replies

V
24-Ruby IV
ValeryOchkov24-Ruby IV
24-Ruby IV
June 12, 2017

Try please copy the answer and input it as guess value.

Better to have the guess value not as x:=1 y:=2 ets but as two vectors.

As here for example

Fig-2-Find.png

Fig-4-Find.png

The second answer is correct!

V
vlehner1-VisitorAuthor
1-Visitor
June 12, 2017

Thanks Valery, that's cool idea!

I used the results for guess-values like you did (in Vector-Form) but i got unrealistic results although i checked my equations again after that.

V
24-Ruby IV
ValeryOchkov24-Ruby IV
24-Ruby IV
June 12, 2017

And second!

Non linrar system can have not one solution!

See please Video Link : 2418

D
DJF16-PearlAnswer
16-Pearl
June 12, 2017

I believe you have not formulated it correctly.  If you get multiple answers that usually means there are multiple answers.  Mathcad stops as soon as it finds one solution.  Running a quick check of your results shows that all of the constraints are solved properly with your results.  Maybe TOL or CTOL would make a difference, but I doubt it.  Check the results to see what isn't making sense.

check.png

V
vlehner1-VisitorAuthor
1-Visitor
June 13, 2017

Hi dferry,

Thank you!

I'll check this again.

You are concentrated to the problem and sorry for the other answes in my thread: I don't need nice animations and Van Goghs-this is out of my topic, i need solutions and that non linear systems can have multiple solutions is clear for me and can be told in one sentence !!!

Volker

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