How to apply experiment force for a certain duration?

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Wentao Li
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Joined: Fri Mar 02, 2018 1:07 pm

How to apply experiment force for a certain duration?

Post by Wentao Li » Fri Jan 17, 2020 2:28 pm

Hi,

I have some problems running RRA. The right ankle twists arbitrarily at the end of gait during its swing phase. I cannot fix it by increasing the weight.

Now I'm considering if the problem is due to GRF applied. Since the experiment used several force plate, the former force plates that were passed still have some force on the right foot which cannnot be filtered maybe. So I wonder if there is a way to specify the time duration each force plate should work.
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OpenSim 4.0
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Dimitar Stanev
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Joined: Fri Jan 31, 2014 5:14 am

Re: How to apply experiment force for a certain duration?

Post by Dimitar Stanev » Mon Jan 20, 2020 2:17 am

Maybe if you increase the weights of the tracking task (one of the file specified in RRA analysis) of the ankle you will solve the problem. Try giving a high value e.g. 300.
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Aaron Fox
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Re: How to apply experiment force for a certain duration?

Post by Aaron Fox » Mon Jan 20, 2020 3:52 pm

Hi Wentao,

If you think the problem is the GRF application and you have marker data you could also configure your analysis pipeline to only apply forces to the body when they are within a specified distance to the force centre of pressure. Not sure whether you are using Matlab or not - but there is a function as part of this project (https://simtk.org/projects/matlab_tools) called 'assign_forces' (I think...) that converts ground reaction force data to an external forces file under the condition of the force being above a certain threshold and within a specified distance to a marker on a body.

Aaron
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