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Posted: **Sun May 01, 2016 4:19 pm**

I am looking to estimate the Ground Reaction Force without having force plate data (I do have force data from pressure insoles, and can find Center of Pressure). I would like to be able to use the rolling constraint developed in this article:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3993009/

however, I do not know how to add a constraint to the model, let alone the rolling constraint. The article reads "The constraint utilizes the measured ground reaction force and center of pressure, which will include any errors associated with these experimental measurements... Additionally, by utilizing the measured center of pressure, the rolling constraint is limited to analyses of measured data and cannot be used in predictive simulations (e.g., Wang et al., 2012)."

Is it feasible to use the rolling constraint for estimation purposes given center of pressure and vertical force data from pressure insoles?

Posted: **Tue May 17, 2016 11:10 am**

Based on the requirements of the constraint, that seems feasible.

The API documentation for the class can be found here. However, it may be easier to edit XML directly;

Code: Select all

<RollingOnSurfaceConstraint>
 <!--Flag indicating whether the constraint is disabled or not. Disabled means that the constraint is not active in subsequent dynamics realization-->
 <isDisabled>false</isDisabled>
 <!--Specify the rolling body for this constraint.-->
 <rolling_body></rolling_body>
 <!--Specify the body containing the surface (plane) that the rolling body rolls on.-->
 <surface_body>ground</surface_body>
 <!--Surface normal direction in the surface body.-->
 <surface_normal>0 1 0</surface_normal>
 <!--Surface height in the direction of the normal in the surface body.-->
 <surface_height>0</surface_height>
 <!--Coulomb friction coefficient for rolling on the surface.-->
 <friction_coefficient>0.5</friction_coefficient>
 <!--A guess at the area of contact approximated by a circle of radius.-->
 <contact_radius>0.01</contact_radius>
 </RollingOnSurfaceConstraint>

Posted: **Tue May 17, 2016 11:56 pm**

Hi,

If you are interested to estimate the ground reaction force, there is not an implemented algorithm to this in the current version of OpenSim as far as I know.

viewtopicPhpbb.php?f=91&t=4863&p=11883&start=0&view=

Best

Posted: **Wed May 18, 2016 11:05 am**

Anybody seems to have a method for prediction which they did a Webinar on
https://www.youtube.com/watch?v=tIC5eqKiaEc

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Adding Constraint to Model (Rolling Constraint)

Adding Constraint to Model (Rolling Constraint)

Re: Adding Constraint to Model (Rolling Constraint)

Re: Adding Constraint to Model (Rolling Constraint)

Re: Adding Constraint to Model (Rolling Constraint)