Applying an external force

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Clarissa LeVasseur
Posts: 8
Joined: Mon May 18, 2015 1:28 pm

Applying an external force

Post by Clarissa LeVasseur » Mon Jun 29, 2015 9:03 am

Hello!

I am working with an upper extremity model, and I want to apply a force that will constantly be applied at the center of the hand for a forward dynamic simulation. Without using motion capture systems and force plates to generate a motion or storage file that can be applied to the forward dynamic simulation, is there any way to write in this external force into my model? I have played around with a prescribed force, but I either don't have the code correct, or it is not what I want to do.
This is what my code looks like:
<PrescribedForce name="prescribedF">
<!--Flag indicating whether the force is disabled or not. Disabled means that the force is not active in subsequent dynamics realizations.-->
<isDisabled>false</isDisabled>
<!--Name of the body the force is applied to.-->
<body>hand</body>
<!--Flag indicating whether the point (specified in pointFunctions) is in global frame.-->
<pointIsGlobal>false</pointIsGlobal>
<!--Flag indicating whether the quantities (specified in force/torqueFunctions) is in global frame.-->
<forceIsGlobal>true</forceIsGlobal>
<!--Three functions describing the force to be applied.-->
<FunctionSet name="forceFunctions">
<forceFunctions>
<function>
<Constant name="forceX">
<value>-100000</value>
</Constant>
</function>
<function>
<Constant name="forceY">
<value>0</value>
</Constant>
</function>
<function>
<Constant name="forceZ">
<value>0</value>
</Constant>
</function>
</forceFunctions>
</FunctionSet>
<!--Three functions describing the location at which the force is applied.-->
<FunctionSet name="pointFunctions">
<pointFunctions>
<function>
<Constant name="pointX">
<value>0</value>
</Constant>
</function>
<function>
<Constant name="pointY">
<value>0</value>
</Constant>
</function>
<function>
<Constant name="pointZ">
<value>0</value>
</Constant>
</function>
</pointFunctions>
</FunctionSet>
</PrescribedForce>

I would prefer to stick with writing this on xml.
Thanks!
Clarissa
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jimmy d
Posts: 1375
Joined: Thu Oct 04, 2007 11:51 pm

Re: Applying an external force

Post by jimmy d » Thu Jul 02, 2015 8:14 am

You can apply the force in the body frame. When specifying the application of force, select 'Body Force'. This will apply your forces to the COM of the body.
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Malavika Harikrishnan
Posts: 12
Joined: Wed Mar 02, 2016 9:38 am

Re: Applying an external force

Post by Malavika Harikrishnan » Thu May 12, 2016 2:12 am

Hello,

I'm trying to do something similar and am facing the same issue
Do you have an update on how you solved this?

Thanks in advance
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