Problems using neck model

[Moe Curtin]

I have been trying to use Anita's neck model in OpemSim and I have had a few problems, I've tried a couple workarounds but still amn't getting anywhere. Here's what I've done (sorry if its a bit long-winded)

I imported the SIMM model using the Neck3dof.jnt and NeckMus.msl files. That worked fine.

I then tried to load the motion files associated with this particular model (head3dir.mot , Pitch.mot , Roll.mot , Yaw.mot) but got the following error message for all of them:

Could not read motion file.

I edited head3dir.mot and deleted all the spaces in between the rows and the file then opened. The motion file ran for the correct time span (0 - 100), but the actual motion itself ran far too slowly and only approx 30% of the motion was executed before the time ran out.

I edited the motion file again, this time adding a column titled "time" and inserting values evenly spaced between 0-100 in the appropriate rows. The motion file was now running correctly.

I then tried to perform inverse dynamics. The program ran, but outputted -1.#IND0000000000000000 into every cell in the output file InverseDynamics_force.sto

Seeing as I've hit so many obstacles, I wonder if anybody could help me out?

Thanks

[Ayman Habib]

Dear Moe,

For the .mot files, we assume that either you have a time column or you have a "range" specified in the header. Lacking both, what you did is a fine workaround, except that you specified that the motion goes over 100 seconds so the playback is going to be slow but you can change the playback speed using the spinner in the toolbar (or change the values you put for time in the file to more realistic numbers).

InverseDynamics will not work unless you have masses specified for all segments, do you have that? Also what forces are you applying? Usually a NAN in results is due to a (large) force applied to a segment of 0 or very small mass.

Hope this helps,
-Ayman

[Moe Curtin]

Hi Ayman,

Thanks for your reply. I had masses defined for all segments and no external forces were applied. Looks like the masses I had were too big (and unrealistic). When I reduced them, the inverse dynamics returned some results. Thanks for your help.