GRF point in MOCO vs OpenSim

OpenSim Moco is a software toolkit to solve optimal control problems with musculoskeletal models defined in OpenSim using the direct collocation method.
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Burak Kula
Posts: 31
Joined: Wed Dec 04, 2019 3:34 pm

GRF point in MOCO vs OpenSim

Post by Burak Kula » Tue Jun 29, 2021 10:29 pm

Hello Everyone,

I am wondering that, how moco 1.0 knows GRF points (center of pressure(CoP) points) ?
As I know, in Moco there is no way to calculate CoP but when I visualize the result, I can see the GRF forces on display video but when I load the "result.sto" file that is obtained in Moco, I could not see the GRF forces as I see in Moco. In moco GRF forces act from contact points on toes (e.g.: in my model its name is front) and in OpenSim GRF forces act on only middle of "floor" body not on calcaneus or toes

Burak.

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Nicholas Bianco
Posts: 963
Joined: Thu Oct 04, 2012 8:09 pm

Re: GRF point in MOCO vs OpenSim

Post by Nicholas Bianco » Mon Jul 12, 2021 9:42 am

Hi Burak,

Moco doesn't compute CoP from the SmoothSphereHalfSpaceForce elements in your model, but you can compute CoP based on the forces and moments that these elements report (i.e, from 'createExternalLoadsTableForGait()'). See this webpage: http://www.kwon3d.com/theory/grf/cop.html.

The Simbody visualizer creates a force visualization from the simulation result, but the GUI unfortunately does not.

Best,
-Nick

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