ADAMS Constant Radius Cornering simulation fault 1

[konrad.stachon]

Hello, I keep running into this error message when trying to set up Constant Radius Cornering simulation. I was ok, before I changed CM location.


---- START: ERROR ----
At time 7.708098512E-01 the integrator is unable to start/restart. Possible Causes:
(1) The accuracy required for the numerical solution can not be attained.
Relax (increase) the value of the acceptable integration ERROR.
(2) Incompatible redundant constraints, a lock up, or a bifurcation
situation. The latter two indicate a mechanism design problem.
(3) The system includes a zero (or relatively small) mass on a part with
an unconstrained translational degree of freedom.
Make sure you have mass on all parts with translational degrees of freedom.
(4) The system includes a zero (or relatively small) inertia on a part
with an unconstrained rotational degree of freedom.
Make sure you have inertias on all parts with rotational degrees of freedom.
(5) An Adams element has a function expression that equals exactly itself.
For example,
SFORCE/id1,I=id2,J=id3,ROT,FUNC=SFORCE(id1,jflag,comp,rm),and
DIFF/id4,IMPLICIT,IC=0,FUNC=DIF1(id4).
Similarly,
VARIABLE/id5, FUNC=VARVAL(id5)*TIME
equals itself at 1 second. Avoid setting an Adams element equal to itself.


---- END: ERROR ----

Dynamic Solution stopped.


End Simulation

Simulate status=-124



---- START: ERROR ----
SIMULATE command failed for minimaneuver: STEADY_STATE
Aborting Execution.

---- END: ERROR ----


---- START: ERROR ----

Adams Solver (C++) run terminating due to STOP requested by user.


---- END: ERROR ----

Termination status=-995

Terminating Adams Car usersubs...


Finished -----
Elapsed time = 10.93s, CPU time = 10.13s, 92.63%

Simulation is complete.

 

[GregLocock]

Great. Your sim is actually running. 1 or 2 is the most likely. Look at the animation and see if anything looks odd.

Cheers

Greg Locock


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[konrad.stachon]

Thank You very much Greg for quick answer. The animation looks strange at this case, because front wheels have fallen off xD. I changed step size, and turn radius a little and for now it works.

Konrad
PGRacing Team

 

[konrad.stachon]

Sadly I've problems with CRC again. For now the simulation works but it looks strange. Below You can see the steering wheel position and simulation parameters. I tried to change simulation error and Hmax parameters but it didn't work. If You have any idea what could be wrong it will be really helpful.

 

[GregLocock]

what's your wheelbase, and steering ratio?


Cheers

Greg Locock


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[GregLocock]

Also try the dynamic event, swept steer. CRC can get a bit grumpy.

Cheers

Greg Locock


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[konrad.stachon]

Others dynamic events like J-turn or mentioned swept steer works good. Wheelbase: 1280mm Reduction ratio: 5.25E-02 (4,71" / 1 rev)

 

[GregLocock]

No, what's the overall steer ratio - should be a number like 10.5



You could try unticking Quasi static skidpad setup (probably not that)


Cheers

Greg Locock


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[konrad.stachon]

I tried to untick Quasi static skidpad setup, but nothing changed. Steering ratio: 3.85

 

[GregLocock]

So, your tire doesn't like quasi static events. What tire model are you using?

Cheers

Greg Locock


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[konrad.stachon]

I use Pacejka 89 and data from TTC consortium.

 

[GregLocock]

Odd, Pac89 is stable generally. I don't use Pac much in ADAMS but can't remember it hating quasi statics. Does the understeer number from your swept steer check out?

Cheers

Greg Locock


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[konrad.stachon]

To be honest I'm not sure what you mean when you write "understeer number", but attached bellow slip angle's graph looks fine I think. The speed was 60 km/h.

 

[GregLocock]

I meant comparing your calculated (linear range) understeer or side slip angles compared with the simulation.

Cheers

Greg Locock


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

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[konrad.stachon]

Calculation based on a tire cornering force graph gave 1,7 deg slip angle for the front axle, which is a similar result to simulation. For the rear axle slip angle is slightly higher and it is 1.8 deg, which is a big difference in comparison to simulation. Weight distribution is 48% on the front and 52% on the rear axle.

 

[GregLocock]

Hmm, can you try a different tire in the CRC test?


Cheers

Greg Locock


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[konrad.stachon]

Ok, I try in the evening and let You know.
Thank You very much for help.

 

[konrad.stachon]

I tried different tires, but the result in CRC is still the same. Good news is that I found a mistake in tire parameters and for now slip angle values are similar to simple calculation for both axles.

 

[GregLocock]

OK, so that eliminates the most likely contender. Have you got friction statements in your model? other than that, the usual procedure is to start from a model that works, and switch in your new subs until something breaks.

Cheers

Greg Locock


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[GregLocock]

Oh, I'dd add that you may have to fiddle with solver settings. I have no advice there - seems unlikely due to the fact everything else works.

Cheers

Greg Locock


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