Contact Forces

[Anne Schmitz]

Hi Ayman,

I am trying to add contact to my knee model. How do I use the ContactForceSet in the .osim file? I can't find any documentation on this section.

Thanks,

Anne

[daniel jaramillo]

Hi Anne,

Have you been able to find something about it?

Thanks,

Daniel

[Ayman Habib]

Anne & all,

The ContactForceSet in OpenSim is an Obsolete class. A new/working Contact Force mechanism will be available in version 2.0 due later this year.

Sorry for the confusion,
-Ayman

[Anne Schmitz]

Thanks for the clarification Ayman. Does anyone have a plugin for this?

Thanks,

Anne

[daniel jaramillo]

Hi Anne,

I found somebody who is working on this type of plugin, https://simtk.org/home/jointreaction. I have tried contacting him but have got no response. Maby you will get any response from him.

Thanks,

Daniel

[Matt DeMers]

Hi,

I'm not sure what you are trying to do, but if you are looking for something that implements a contact model, JointReaction is not the answer. If you are looking for a tool to calculate the reaction loads at joints then the JointReaction analysis is exactly what you need. It is now built into the OpenSim installation so you no longer need to build JointReaction as a plug-in. Just run open analyze tool and add JointReaction to the list of analyses to check it out. I monitor the forum on the JointReaction project so if you decide to use it and have any question feel free to post them there.

Best,
Matt

[Anne Schmitz]

A note on use from Matt: You need to have kinematics AND actuator forces (like all muscle forces and and any reserve/residual actuators your model has). these can come from CMC or Static Optimization. supply those and JointReactions calculates the forces and moments required at each joint to make the actuator loads, ground reaction loads, and motion of the model consistent. Thus it is calculating the resulting loads at the joints due to the dynamics and the actuation.

[daniel jaramillo]

Hi,

I have not been able to include this analysis in the Analyze tool. I would really appreciate your help on how to do so.

Thanks,

Daniel

[Ayman Habib]

Matt and all,

The JointReaction analysis is available only in version 1.9 and later which is not available publicly yet, but should be available in few days.

-Ayman

[daniel jaramillo]

Hi,

Under the Analyses folder (Program Files\OpenSim 1.8.1\sdk\include\OpenSim\Analyses) I found a folder related to what Matt is saying and one corresponding to Contact forces. Still I have not been able to add them to the analyze tool. If you have any luck please let me know.

Thanks,

Daniel