Error Nonlinear solver to advance time one step

I need help. I was make simulator by using simulink, simhydraulics and simmechanics about robotics. But when run this model any Error Message, like this

Nonlinear solver to advance time one step failed to converge due to Linear Algebra error. Failed to solve using iteration matrix.

...Here is the set of components with unconverged equations: 'comet_virtual2/Leg 2/Foot Hydraulic1/Double-Acting Hydraulic Cylinder2' 'comet_virtual2/Leg 2/Shank Hydraulic1/Double-Acting Hydraulic Cylinder1'

[JAKEER]

Hi, I got the same error message while working with Simscape's custom blocks. Did you solve the problem what you have experienced in 2013 year? If so, please help me how to get out of this error.

Answer 1

[Walter Roberson]

Your Double Acting Hydraulic Cylinder calculations have a singularity, or diverge, perhaps produce an infinity, or due to numeric instability (e.g., round-off is making a big difference in the calculation.)

[Kenzo]

Mr. Walter Roberson, thanks for your explantions. Please, could you tell me (more detail), how to solve it ?

Answer 2

[Seng Tak Goh]

Hi I had the same problem and I managed to solve mine.

I have a Solve Configuration block in the model.

I was able to run my model initially but I ran into the LA convergence issue when I modified my model.

Once I increased the Nonlinear iterations count the solver managed to complete.

Hope this helps

[Anaïs Auberval]

Hi I'm facing the same issue, by how much did you increase the nonlinear iterations ?

Thank you in advance.

[Seng Tak Goh]

Hi Anais,

I actually found out later that, inceasing the iterations count was not the only step I took to actually get the simulation foward.

It was rather a trial-and-error approach.

Maybe I should provide a little more background to my problem and solution...

I took a Simscape model from file exchange, it ran with attached local solver block configured with "Use Fixed-cost runtime Consistency iterations"

I then modified it to suit my target model. The simulation failed on the above problem. Then I played around by increasing the Nonlinear iterations (from 3 to 5, simply), it then managed to get pass that problem. But later I found out the result wasnt right (as expected). If I remembered correctly I also changed the Linear Algebra matrices from Sparse to Full.

So finally I got it rightly simulated by unchecking "Use Fixed-cost runtime Consistency iterations", setting Linear Algebra to Auto.

I dont actually know why it was that way...just being lucky.

Hope it helps

[Anaïs Auberval]

Thank you very much !

It didn't work with changing the nonlinear iterations, from 3 to 5 and Linear Algebra to Full it didn't solve the problem. But when I tried unchecking "Use Fixed-cost runtime consistency iterations" and put Linear Algebra back to auto, it worked !

I also don't know why but thank you !

[kuldeep singh]

I am facing the same issue now. I looked for discussions here. I still am facing issues

[Lalitesh Kumar]

Last year (2020) I have faced same issue (MATLAB 2016) but when I scaled my controller then it started working and results was good. But when I run the same simulink model in MATLAB 2021 then the same problem started. I don't know why ? I do not know what should be the problem of change of MATLAB version. However, still I am getting my results in MATLAB 2016 version.