Steering simulation issue

[VojtechBrychta]

Hello,

I have encountered an issue and I was wondering whether you can help me with it.

I have a front axle assembly with a steering system trying to run a suspension analysis:steering. The steering consists of a steering wheel that goes to a steering lever through a reduction box. Now, if I set up the reduction at 10 and run an analysis from -100 to 100 degrees, the simulation runs just fine. If I set up the reduction at 1 and run the analysis from -10 to 10deg, the simulation fails pointing out a following error:

Static equilibrium analysis has not been successful.
The maximum number of iterations 25, has been reached.
For the last attempted iteration:
The equation with the largest error was model.testrig.controller_steering Comp = 0 Error = 0.000000
The variable receiving the largest increment was model.testrig.jostra_steering_part Comp = 3 Delta = 9.099849.

This means I try to run the simulation with the same inputs, only difference is the reduction. I checked the pvs_max_steering_torque and angles, and both should be within the limits. I don't see any other inputs that might cause the simulation to fail.

Do you have any tips?

Thanks a lot!
Sincerely,
Vojtech

 

[GregLocock]

In the solver settings change MAXIT to 400, and use a static funnel. Please could you post a screenshot of the wheel steer vs SWA for the successful run with reduction at 10?

Cheers

Greg Locock


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[VojtechBrychta]

Hello Greg,

thanks for your reply.

I don't know how to run a static funnel with the A/CAR simulation as there is nothing much in the .acf file.

preferences/solver=CXX
preferences/list,status=on
control/ routine=acarSDM::con950, function=user(950,35,37,1,2,18,20,1,3,2,3,34,36,2,3,34,36,1,1,0,0,0)
simulate/static, end=251.000000, steps=250
!
stop

Could you explain how to do it please? Nevertheless, the MAXIT at 400 helps with the steering simulation. I attached the wheel steering angles in the function of the steering wheel angle to the attachment. Now there are 2 successful runs with and without reduction.


However, I also noticed an issue when running other static simulations, for example the parallel wheel travel. Unless I set the reduction above certain value I get an error when the PWT is set to start with the wheels without the contact with the testrig. It helps when I completely lock the steeering system (add 0 motion to the steering joint) or remove the steering subsystem completely. The error message ends with following:

Begin Simulation

****** Performing Quasi-Static Simulation ******
Simulation Step Function Cumulative CPU Slvr
Time Size Evaluations Steps Taken time type
___________ ___________ ___________ ___________ ________ ___
9.00000E-01 1.00000E-01 125 10 1.17 1


Time: 9.498712739E-01.
QSTATIC: Step Size Too Small: 6.119229265E-06

End Simulation

Simulation failed



Begin Static Solution


STATICS: Original static solver will be used with the Sparse linear solver.

Static Solution converged in 2 iterations
Residual imbalance is less than 0.00000E+00

End Static Solution
command: simulate/static, end=251.000000, steps=250
Begin Simulation

****** Performing Quasi-Static Simulation ******
Simulation Step Function Cumulative CPU Slvr
Time Size Evaluations Steps Taken time type
___________ ___________ ___________ ___________ ________ ___
9.49871E-01 0.00000E+00 0 0 1:30 1


Time: 9.498712739E-01.
QSTATIC: Step Size Too Small: 6.104739471E-05

End Simulation

Simulate status=-124

command: !
command: stop

Termination status=0

Terminating Adams Car usersubs...


Finished -----
Elapsed time = 113.29s, CPU time = 112.48s, 99.29%

Analysis failed!
Please check the error messages to determine the cause.

Thanks again for the support Greg.

Sincerely,
Vojtech

 

[GregLocock]

50 degrees of wheel steer is pushing it. Sorry I can't remember how to switch static funnel on, I assume it is buried in the solver settings somewhere.



Cheers

Greg Locock


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[VojtechBrychta]

It doesn't work even for smaller angles.


I was advised to by the MSC support to check the following link:

https://simcompanion.hexagon.com/cu...ng-torque-and-steering-displacement-kb8019191

Then to set environment variable MSC_SD_STTRQ_MAX which limits the maximum steering torque for any simulation done in Adams. But still no success. I'm still in contact with the support, I will post the solution here if I'm successful. Seems to me like an internal A/CAR issue.

Thank you Greg for your time.

Sincerely,
Vojtech

 

[VojtechBrychta]

Hello,

Just to come back on the issue I was facing. I received a feedback from Adams support. The issue seems to be really in the solver settings. Changing the stability parameter from 1e-5 to 1e-7 solves the problem I have. I cannot tell if there is something else I can do within the model to avoid changing the solver's setting.

Thanks a lot for your time.

Have a nice day,
Vojtech

 

[GregLocock]

Yes, we waste a lot of time getting the solver set up correctly. Other software does't seem to suffer from this to the same extent.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?