Spherical joint problem
Spherical joint problem
(OP)
Hi, I am using many spherical joints in my model, and I have some problem. I created them like that:
constraint create joint Spherical &
joint_name=Spherical1 &
adams_id=1 &
i_marker_name=Marker3 &
j_marker_name=Marker4
constraint attribute constraint_name=Spherical1 name_vis=off
group modify group=SELECT_LIST object=Spherical1
And Adams/view says:
WARNING: The markers for JOINT Spherical1 are not initially coincident.
The relative displacement between the markers, expressed in the
J marker coordinate frame is:
Delta X = 0.0 Delta Y = -1.06439E-04 Delta Z = 2.95960E-03.
I don't understand why. This warning bring some strange behavior. How could exit a displacement between the markers whereas I have created a spherical joint between them? How could I avoid that error?
Thanks a lot for your help.
constraint create joint Spherical &
joint_name=Spherical1 &
adams_id=1 &
i_marker_name=Marker3 &
j_marker_name=Marker4
constraint attribute constraint_name=Spherical1 name_vis=off
group modify group=SELECT_LIST object=Spherical1
And Adams/view says:
WARNING: The markers for JOINT Spherical1 are not initially coincident.
The relative displacement between the markers, expressed in the
J marker coordinate frame is:
Delta X = 0.0 Delta Y = -1.06439E-04 Delta Z = 2.95960E-03.
I don't understand why. This warning bring some strange behavior. How could exit a displacement between the markers whereas I have created a spherical joint between them? How could I avoid that error?
Thanks a lot for your help.





RE: Spherical joint problem
It's only a warning, does the model run?
If you like set error to 0.03 to get rid of the warning, if that is an appropriate size for your model.
If you are using 'many' SPHJ then there is a good chance you have created a structure not a mechanism, try using bushings with a realistic stiffness instead.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Spherical joint problem
It's not really a solver problem. During the assembly phase of the solution ADAMS will move parts so that all constraints are fulfilled. But this might not have been what you wanted. So check the coordinates of the markers and adjust the parts as needed.
Jesper Slattengren
www.prattmiller.com
RE: Spherical joint problem
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Spherical joint problem
One warning though:
Marker coordinates in the adm-file are written relative to the part coordinate system (LPRF as it used to be called). So remember to check the part. In this case, it is likely that you moved the part by mistake and the markers that belong to it simply followed along.
Jesper Slattengren
www.prattmiller.com