Closed Chain Movements (snowboarding)

Provide easy-to-use, extensible software for modeling, simulating, controlling, and analyzing the neuromusculoskeletal system.
POST REPLY
User avatar
Paul McAlpine
Posts: 8
Joined: Sun May 24, 2009 6:34 pm

Closed Chain Movements (snowboarding)

Post by Paul McAlpine » Tue Jun 16, 2009 6:37 pm

Hello, I am attepting to modify the gait2392 model to create a closed chain movement pattern. This is to be used to simulate snowboarding where both feet are fixed relative to the board by non-release bindings.

To do this I have created a joint between each foot and the 'ground' and reversed the order of the segment parent-child arrangement so the proximal segment moves relative to the distal segment (e.g. tibia moves forward over foot during dorsiflexion).

I can achieve this for the individual limbs however when i get to the pelvis I strike a problem.... As far as I know I can only use one segement as the parent of the pelvis (either right or left femur) and thus I cannot create both hip joints.

I would like the relative position of the femurs to dictate the position and orentation of the pelvis in space.

If anyone has dealt with this problem or has any pointers I would be greatly appreciative.

Regards

Paul McAlpine

User avatar
Ajay Seth
Posts: 136
Joined: Thu Mar 15, 2007 10:39 am

RE: Closed Chain Movements (snowboarding)

Post by Ajay Seth » Wed Jun 17, 2009 3:09 pm

You can use the gait2392 model and add WeldConstraints to affix the feet to the board.
Add something like the following to the ConstraintSet:


<WeldConstraint name="">
<isDisabled> false </isDisabled>
<body_1> board </body_1>
<body_2> calcn_r </body_2>
<location_body_1> 0.0000000000 0.000000000 0.0840000000 </location_body_1>
<orientation_body_1> 0.0000000000 0.0000000000 0.0000000000 </orientation_body_1>
<location_body_2> 0.000000000 -0.0200000000 0.000000000 </location_body_2>
<orientation_body_2> 0.0000000000 0.0000000000 0.0000000000 </orientation_body_2>
</WeldConstraint>

User avatar
Paul McAlpine
Posts: 8
Joined: Sun May 24, 2009 6:34 pm

RE: Closed Chain Movements (snowboarding)

Post by Paul McAlpine » Wed Jun 17, 2009 3:49 pm

Thanks Ajay, thats a great help.

Have have successfully attached the right calcaneus to the board but I am having issues with the left calcaneus - irrespective of the location coordinates that I enter for either body the left calcaneus ends up in the same location as the right one in the opensim program.

Any suggestions?

Kind Regards

Paul

User avatar
Paul McAlpine
Posts: 8
Joined: Sun May 24, 2009 6:34 pm

RE: Closed Chain Movements (snowboarding)

Post by Paul McAlpine » Wed Jun 17, 2009 5:48 pm

This appears to be a problem with Open Sim version 1.8.1. If I use version 1.8 I can weld both feet to the board with no probelms

Thanks again

Paul

User avatar
Michala Cadova
Posts: 40
Joined: Tue Nov 23, 2010 3:45 am

Re: Closed Chain Movements (snowboarding)

Post by Michala Cadova » Thu Aug 09, 2012 4:56 am

Hi,
What exactly means tags <location_body_1> and <orientation_body_1> (and for the second body as well) ?

Michala

User avatar
Michael Sherman
Posts: 807
Joined: Fri Apr 01, 2005 6:05 pm

Re: Closed Chain Movements (snowboarding)

Post by Michael Sherman » Thu Aug 09, 2012 9:12 am

Hi, Michala. Those parameters specify the location and orientation of a coordinate frame attached to each body. Then the weld constraint acts to hold the origins of those two frame in the same spatial location, and to align their axes. So if you leave those at their default values (0,0,0) the frames will be coincident with the body frames, and the weld constraint will act to hold the body frames of each body coincident.

Regards,
Sherm

POST REPLY