Parallel chain linking for

[Rory Turnbull]

Hi All,

I am building on the 2D MOCO example to test a model I would like to run. Building on the 2D_gait.osim model I have added a single DOF exoskeleton shell on either side matching the joints of the skeleton model using pin joints. The hip section attaches at the pelvis with a weld joint, the system then move down to the feet where there is a weld joint between the footplate and the calcaneus of each side.

This has been assembled fine using the Matlab API. However, when I plug this into the example2DWalking.m file with all the same inputs as the example I get the following error:


Error using example2DWalking (line 92)
Java exception occurred:
java.lang.RuntimeException: Component 'LeftFootExo_slave_0_weld' of type WeldConstraint has no owner and is not the root.
Verify that finalizeFromProperties() has been invoked on the root Component or that this Component is not a clone, which has not been added to another Component.
Thrown at Component.cpp:1681 in initComponentTreeTraversal().

at org.opensim.modeling.opensimMocoJNI.MocoTrack_initialize(Native Method)

at org.opensim.modeling.MocoTrack.initialize(MocoTrack.java:549)


I tried changes the weld joint between the foot and plat to a slider joint, in an attempt to alleviate any over constraining that might have occurred but it didn't help. Have any of you come across something similar or have any suggestions on how I can move past this?

Any help is appreciated as I am a little stumped at the moment.

Best wishes,
Rory Turnbull

[Ross Miller]

Hi Rory,

You'll probably get a better response by posting this on the main OpenSim forum (indexPhpbb.php?f=91) since it seems like it's more of an OpenSim issue than a Moco issue.

I would guess something in the definition of the joint is probably just missing or is incorrect. It sounds like you are trying to define a closed kinematic chain which I know has some tricks to it for e.g. simulating cycling/pedaling in OpenSim. There's a good thread on this but I couldn't find it, I will update this post if I find it.

Hope this helps,
Ross

[Rory Turnbull]

Hi Ross,

Cheers for the response. I'll have another comb through the OpenSim forum then post it in there!

Best wishes,
Rory