Joint Stop

Easy peasy way is to define a non linear torsional spring. This has the advantage that you can shape the force vs deflection curve to represent the real stiffness of your end stops. If you do this right you'll end up with much faster solve times than if you use contacts.

It will be difficult to add damping or friction to that system without using contacts, but there may be a clever way similar to the method at the end of this note.

Using contacts isn't very difficult, it is just numerially unstable, and rather hard to calibrate.

An alternative approach is like this, where a bumper only exerts a force when it is in vertical contact, and also has damping only when it is in contact. Note that this formulation explicitly does not use contact for speed and robustness.

VARIABLE/118971,
,FUNC=(DZ(118971,118775,118775)+ABS(DZ(118971,118775,118775)))/2.0
! bumper elastic force
VFORCE/118971,I=118775,JFLOAT=1189711, RM=118775
, FX=0\FY=0\FZ=ABS(AKISPL(VARVAL(118971),0,118971))


VARIABLE/118775,FUNC=VZ(118971,118775,118775,118775)
! bumper damping force
VFORCE/118775,I=118775,JFLOAT=1189712, RM=118775
, FX=0\FY=0\FZ=STEP(VARVAL(118971),0,0,.1,0.1*(VARVAL(118775)))






Cheers

Greg Locock


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

Hello,

Thank you for your answer. Yes, my problem is the calibration of the contact, not its using.

I will try the nonlinear spring, this solution probably has also calibration problem, but maybe easier to solve it, because my joint stop device (in the real design) is a bumper, a rubber like material.

And thanks for the last suggestion, I will test it.

Dezsit