How to apply spline data as SFORCE input in MSC Adams

[martinope9]

Dear All,
I'll be grateful if someone might help me.

I have a SPLINE which summarise the trend of a load with respect to the time. I wish to apply it as a SFORCE in MSC Adams by using a SINGLE-COMPONENT FORCE.

I'm actually using the following code "AKISPL(time,0,input_2_12, 0)" but the simulation stops running showing this message:
ERROR: At time 3.545690582E-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.
I read about someone who used "*DTOR" at the end of the code to convert units (from degrees to radians) but I don't have any rotating joint or rotating motion.

Does anyone of you know how to apply this load correctly?

Thanks in advance,

Giuseppe.

 

[GregLocock]

I suggest you elimainate items 1 to 4. DTOR is irrelevant.

Cheers

Greg Locock


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[martinope9]

Hi Greg,
thanks for your reply.

I agree with you to look just at the issue 5. I also think that my problem might be related to this suggestion "VARIABLE/id5, FUNC=VARVAL(id5)*TIME" but I still don't know where the issue is in my model.

When I import the dpline data, I define the column 1 as "independent column index" (which is the time data), then I use the code mentioned before to apply the SFORCE: "AKISPL(time,0,input_2_12, 0)".

Still working on it. I'll post something if I'll fix the issue soon. In the meantime I appreciate any suggestions.

Thanks,

Giuseppe.

 

[GregLocock]

Sorry, I'm suggesting you need to work through 1 to 4 as possibilities, and eliminate them as causes if they don't apply. 5 seems an odd one to me.

Cheers

Greg Locock


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

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