external load location coordinate system

[Zheqi Hu]

I need to input the external load file from Vicon System, but the result went bad. It might cause by the external load file.

I have checked the example external load file of model gait2354, the position of external load might not be in the same coordinate system as the model. I'm wondering that where the original point of the frame is.

Any advise would be helpful.

Zheqi

[Dimitar Stanev]

Hi,

The grf must be transformed from the lab's reference frame to the model reference frame. The forces are expressed typically in the ground frame, and are applied at a specific point on a body. I would suggest you to use the existing tools that generate the appropriate OpenSim files from Vicon.

http://simtk-confluence.stanford.edu:80 ... otion+Data

[Zheqi Hu]

Hi,

The grf must be transformed from the lab's reference frame to the model reference frame. The forces are expressed typically in the ground frame, and are applied at a specific point on a body. I would suggest you to use the existing tools that generate the appropriate OpenSim files from Vicon.

http://simtk-confluence.stanford.edu:80 ... otion+Data

Thanks for your reply.

As it can be seen, the loads are applied at a specific point on a body, so are the coordinate of the load points in the frame of the body? For example, when the load is applied on calcaneum, should the coordinate of the load point in the reference frame based on the calcaneum, which is different from the frame used in marker trajectories file? If yes, how could the frame be identified?