Muscle Force Components

Main Forum
1

Hello,

I am trying to use AnyBody’s muscle force data in a finite element model so I am interested in having the x, y, and z components of the forces. I have found where the total magnitude of the force can be saved, but I can’t find either the components or the angles at which these forces act anywhere. Is this information easily available anywhere within AnyBody (v3)?

Thank you,
Jennifer

2

Hi Jennifer

Please try include the object “AnyMechOutputFileForceExport” in your study it will export all forces acting on one or multiple segments to a text file. This info includes the muscle force vector.

Best regards
Søren

3

Thank you - I hadn’t seen the new FEA tutorial before. I will look through that and I’m sure any further questions will be answered!

Jennifer

4

Hello,

I see where the FEA tutorial says that the AnyBody-ANSYS link requires AnyBody v3.1 or higher to run. Can you please confirm whether the coding explained in the FEA tutorial will work for AnyBody v3.0.4?

Thank you,
Jennifer

5

Hi Jennifer,

I am one of the developers that worked on the writing Any2Ans, the software that links AnyBody with Ansys (www.ozeninc.com/Any2Ans). If you are able to add the “AnyMechOutputFileForceExport” class to your AnyBody file and get the model to properly run, the connection software to Ansys will work. The original development and integration of Any2Ans occurred during AnyBody v.3.0.x, and I was using some special version builds provided by the AnyBody guys, but I think by the official release of v.3.0.4, most of the capabilities were integrated.

Let me know if you would like a trial license to test out Any2Ans to see if it can be of use to you. You can contact me directly at dwwagner@ozeninc.com

Best,
David Wagner, PhD

6

Hello,

I have some clarification questions about the txt file that can be exported using AnyMechOutputFileForceExport. (I am including this coding within my study to get the muscle force data as mentioned in the FEA tutorial).

I have been able to successfully output the txt file but I am not sure exactly what format the data is in. I see in the FEA documentation/tutorial where it says all coordinates are listed in the global system. If the muscle forces are in the global system, however, I am slightly confused.

All the muscle forces within the txt file are listed only in F[0] (the only F[1] or F[2] are for joint reaction forces), which according to the documentation seems to mean that all of the muscle forces act only in the global x direction. Clearly all of the muscle forces don’t act only along the global x axis, though… Then I thought maybe I had misunderstood the documentation so I tried adding the three numbers following F[0] (as scalars) to get the total muscle force, but the resulting number did not match the single muscle force magnitude that you can get by using the chart within AnyBody (if you plot a muscle’s Fm within Chart2D). Then I thought maybe the three numbers after F[0] were the vector components Fx, Fy, Fz of the muscle force so I vectorally added these three numbers to get the resulting magnitude… but this calculated number also was not the same as the single muscle force you can read from the Chart2D.

Can you please explain exactly what these numbers after the F[0] in the muscle force output are? And if they are force components in x, y, and z, which coordinate system (local/segment or global) are they in?

An example of my output is below:
Force[203]:
Name=Main.HumanModel.BodyModel.Right.Leg.Mus.Soleus
Class=AnyMainFolder.AnyFolder.AnyFolder.AnyFolder.AnyFolder.AnyFolder.AnyViaPointMuscle
Segment=Main.HumanModel.BodyModel.Right.Leg.Seg.Shank
SegmentID=3
Pos=-3.946664569308692e-001;-3.039081003865068e-001;3.790401401351149e-001;
RefFrame=Main.HumanModel.BodyModel.Right.Leg.Seg.Shank.SoleusNode
NumComponents=1
F[0]=-1.482270981649477e+001;1.543415355488255e+001;-1.902331943020444e+002;
M[0]=-0.000000000000000e+000;-0.000000000000000e+000;-0.000000000000000e+000;

Thank you,
Jennifer

7

Hello Jennifer,
basically the components are the forces (Fx, Fy, Fz) given in the global coordinate system. Sorry for the confusion that is caused by the naming “F0”. If you compute the vector norm of the components it should result in the same value as given in the Chart2d. Please compare it with the Ft value, Fm may, depending on the muscle model you use, neglect force components.
Hope this helps, otherwise please write again,
Sebastian

8

Thank you, Sebastian

Using Ft, the vector norm of the force components from the text file is as expected.

Jennifer