simtk.org

Hi,

I've migrated my model from SIMM to opensim, creating a model based on the simmkinematics engine. Based on the layout of the examples, I have attempted to further migrate the model to employ the Simbody engine.

I think that I have addressed all of the error messages:
1. transformed the model such that all rot2planar joints are in the XY plane
2. ensured at least one (fixed) DOF per joint (i.e. no "welded" joints)
3. added the SpeedSet for each DOF

Now when I load the file, opensim crashes without any error report. Maybe there is a typo in the model, but VIM editor doesn't show any obvious XML errors.

How can I determine what is wrong in the file?

here is the diagnostics using opensim_w.exe from a command window:

Created model forelimb from file D:\ ...\fullForelimb.osim
Handling locked coordinate.
Found constant rotational offset.
Constant rotational offsets are not currently supported.
Setting the constant rotational offset to 0.0.
Found constant rotational offset.
Constant rotational offsets are not currently supported.
Setting the constant rotational offset to 0.0.
Found constant rotational offset.
Constant rotational offsets are not currently supported.
Setting the constant rotational offset to 0.0.
Found constant rotational offset.
Constant rotational offsets are not currently supported.
Setting the constant rotational offset to 0.0.
Found constant rotational offset.
Constant rotational offsets are not currently supported.
Setting the constant rotational offset to 0.0.
Found constant rotational offset.
Constant rotational offsets are not currently supported.
Setting the constant rotational offset to 0.0.
#
# An unexpected error has been detected by HotSpot Virtual Machine:
#
# EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x0c973852, pid=5864, tid=3840
#
# Java VM: Java HotSpot(TM) Client VM (1.5.0_06-b05 mixed mode)
# Problematic frame:
# C [SimTKsimbody.dll+0x53852]
#
# An error report file with more information is saved as hs_err_pid5864.log
#
# If you would like to submit a bug report, please visit:
# http://java.sun.com/webapps/bugreport/crash.jsp
#
Deleted model default

I've received numerous Access Violations that crash the JVM as well. If you trace through the log files that are output, you will see that there is an error in the native code written for OpenSim(probably C++?) It is likely there is a non-existent pointer being dereferenced (or a similar error).

Only registered developers of the project will be able to access this native source code and trace back to the exact point throwing this exception.

Hi Simon,

Creating a new model is tricky, as the GUI may crash if the model format is not quite right. I have two suggestions.

(1) Did you try importing the SIMM model and changing the Dynamics Engine to Simbody? If that works you won't have to edit the model by hand.

(2) Could you post the model file online? Maybe then I (or someone on the OpenSim team) could take a look at the file and help you debug it.

Thanks,
Sam

ok - I have managed to overcome this problem by pasting my model properties into a model works, item by item.

The causes of crashes were:

1. The joint hierarchy was not directional, i.e. ground was attached to segment1, but the next joint specified "segment2 segment1" instead of "segment1 segment2". While this is not an issue for SimmKinematics engine, Simbody doesn't appear to handle this.

2. When I was pulling segments out of the model I left behind a generalised coordinate that was no longer referenced in the joint specifications.

Both of these issues cause the immediate crash of OpenSim

Hope this of assistance to others building from scratch

Hi Simon,

I'm also trying to build a model basically from scratch. How did you transform the model such that all rot2planar joint are in the xy plane?

Joseph

Joseph

I am working with an equine model, which approximates all joints of one limb as (near) hinge joints in the same plane. Therefore all joints with translations relating to the joint angle are in the same plane.

All of these joints were previously in the X-Z plane. To rotate into the X-Y plane, I rotated the bone geometry in paraview (www.paraview.org/). Then I transformed all muscle and joint parameters to suit.

Hope this helps

Simon,

That does help. Thank you.

Related to my prevision question, is it possible to have multiple joints move with the same coordinate? For example, with the more complicated Simm version of the lower body models the patella and the tibia moved together with the knee joint angle. Do you know if that is possible with the Simbody dynamics engine?

Joseph,

I had two separate joints that moved using the same generalised coordinate in my original model. This was fine with SimmKinematicsEngine, but would not work with SimBody.

Do you need to have the patella and tibia as different bodies? From the look of the example models, you can include more than one geometry in a single body if you orientate it correctly. Have a look at the definition of the pelvis or tibia in gait2392_simbody.osim. There is more than one .vtp file included in the <geometry_files> tag.

Hi Joseph & Simon,

Unfortunately Simbody does not support "constrained" joints (i.e., multiple joints move with the same coordinate). Currently, SimmKinematics handles these types of constrained joints, BUT SimmKinematics cannot be used to perform dynamics analysis (Inv Dynamics, RRA, CMC, Static Opt...).

Very soon, we will be releasing OpenSim 1.6. One of the new features will be the ability of SimBody to handle constrained joint. This will also make SimmKinemaitcs obsolete, so we will be dropping it in future versions of OpenSim.

Not exactly sure when 1.6 will be released to the public. We had a workshop here at Stanford last week where attendees used OpenSim 1.6, and there are still some things to iron out. But, there should be a release very soon.

Let me know if that answers your question.

Cheers,
Sam