Applying forces to bodyparts

Main Forum
1

Hello everyone,
I need to apply some forces to lower limb of the body via the skin of the human. Can anybody please suggest a method for doing this
Thank you

2

Hi Isuru,

You need to define a reference frame, which would represent a position of the force application on the skin relative to the segmental reference frame. Once this is done (you could use AnyRefNode class for that, see manual) - you can apply a 3D force (AnyForce or AnyForce3D classes) to this chosen ref. frame.


// this object needs to be define in the subfolder of the relevant segment 
AnyRefNode force_application_node = { 
 sRel = {0.1, 0, 0}; // 10 cm along x axis from the origin of the segmental ref frame
};

AnyForce3D force = {
 AnyRefFrame &rf = .force_application_node;
 F = {100, 0, 0}; // 100 N in the global X direction
};

Kind regards,
Pavel

3

Thank you very much for your quick reply. I have another simple question to ask. How do I convert the coordinates given in the global reference frame into a local reference frame?

4

Well, normally you can find global positions and rotations of both objects, after that the differences between positions and rotations will be your relative translation and rotation.

Does this make sense? Which coordinates are we talking about?

Regards,
Pavel

5

I am a new user to anybody. I am trying to understand the FEA tutorial in anybody modelling system. In that example, in force output file, all the forces and their points of action are given in the global coordinate system. I need to transform these coordinate system to local coordinate system of the L5 segment. Can you please explain the way of doing this?
Thank you for your time and consideration.

6

Hi Isuru,

i am sorry for the late reply.
If you look at the reference manual (which is always a good idea) of AnyMechOutputFileForceExport class used in the tutorial - it has an input variable called: RefFrame - it is an object pointer variable to supply an output reference frame.

Which could be used in such way:

AnyMechOutputFileForceExport export_forces = {
//... some code here
 RefFrame = &Main.HumanModel.BodyModel.Trunk.SegmentsLumbar.PelvisSeg.Right.HipJoint;
//... some code here
};

Where the reference frame of interest is the right hip joint node.

Kind regards,
Pavel