Internal and External rotation of Knee

Main Forum
1

Hi!!
I want to make an oscillation motion for the knee(internal/external rotation). To do this, the thigh was fixed and only shank with foot does rotation. We must use the AnyKinFourierDriver and my question ist to know, how we can calculate the Fourier’s coefficients A0,An and Bn. I look the example of PushUp in AnyBody repertory but I don’t understand the coefficients.

Thanks

2

Hi Simon

Welcome to the forum

Please have a look in the Reference manual on page 200 there are some equations explaining the use of the coefficients. The best way to test the driver is do to a one segment model with one dof and play around with the influence of the coefficients.

If you have further questions please ask again.

Best regards
Søren, AnyBody Support

3

Hi,
I will read and try to do it .
thanks

4

Hello !!
I went where you told me (Reference manual on page 200) and I found nothing. In Reference manual page 130, we have an explanation of AnyKinEqFourierDriver without explanation of coefficients.

Best regards
Simon

5

Hi Simon

I am sorry about the wrong page number, i think i must have been opening the manual for forthcomming version by mistake, it is on page 134, the title of the page has to be “AnyKinEqFourierDriver”

Here you will find four equations 4.2-4.5 the A_j and B_j corresponds to the coefficients you are questioning.

If this does not help please do not hesitate to write again.

Best regards
Søren, AnyBody Support

6

Hi Soren

I looked for all Reference manual pages and especially on page 134 and I fund no explanation of the fourier coefficients.
I do not know if I’m in the right manual. To achieve this: www.anybodytech.com----technology&research—reference manual.

If this achieve is rigth, please copy the page and sent me.

Best regard
Simon

7

Hi Simon

Sorry about the confusion

In the current online version at

http://www.anybodytech.com/fileadmin/AnyBody.3.x.x/doc/AnyBodyRefManual.pdf

the page number is 130, and the title of the page is as prescribed previously “AnyKinEqFourierDriver” if you are looking for the description of a certain object you can always search for it in the manual.

if the equations does not help please do not hesitate to ask again.

Best regards
Søren, AnyBody Support

8

Hi Soren!

I have some questions about the fourier coefficient, but i will do it next.
Now, i want to known the very meaning of the maximal muscle activity, because i simulate a flexion movement of lower limb and the maximal muscle activity is the same as in many other muscles. Is that possible? and why?

Best regards
Simon

9

Hi Simon

That is normal, there will be many muscles sharing the same activity.

For further details on the recruitment it would advice you to go through the tutorial:

http://www.anybodytech.com/index.php?id=691

it gives examples on the various settings and provide some basic equations.

If you have further questions please ask again.

Best regards
Søren, AnyBody Support

10

Hi Soren
The Fourier driver is working now, this allows me only in kinematic analysis to make the internal and external rotation.
When I simulate in inverse dynamic analysis, i have always this error:" [SIZE=1]
ERROR(OBJ1)[/SIZE] : [SIZE=1]C:/D…s/s…e/M…s/A…y/R…1/A…n/E…s/R…r/Echantillon.Main.any[/SIZE] : ‘MyStudy’ : Muscle recruitment analysis failed, simplex solver reports that solution does not satisfy all constraints."

I change the contraints in different places of the model, but noting. What can i do to make an internal and external rotation in Inverse dynamic analysis?
If you want, i will sent you the anyscript for this model.

Best regard
Simon

11

Hi Simon,

There can be several reason for the system not being able to solve the inverse dynamic. It could be some instability of the solver, try change to another solver, add a small penalty and add a small amount of gravity in the 0 gravity directions.

If this doesn’t do it then it is probably some mistake in the modeling. I guess you have been playing around with the knee constraints, make sure that you didn’t remove by mistake some reactions other than the ext/int rotation.
You can try to add a reaction force to one or more dof in order to locate more precisely what is causing the problem. That will make it easier to solve.

Best regards, Sylvain.

12

Hi Sylvain !!
I do all thing you tell me to try (change of Solver, playing with constraints…) but nothing changes.
I decide to sent you a copie of my work. I think the problem comes from the last anyscript of the folder EnvironmentModel.
You can look it and help me to resolve the problem.
Try the kinematic analysis first to see the movement I want to do with Dynamic analysis.

Tanks
Simon

13

Hi Simon.

I’m going to ask you a bit more of work, sorry for that. According to the structure of the new forum this thread should now go into the debuging section (as you are asking for debuging).

So please choose one of the two license term (please read the description for each, AnyBody Support do not post in the Self-Supported forum) and create a new thread in the debug section with your files. Thank you.

Best regards, Sylvain.

14

Dear all,

I am also looking at internal and external rotation in the knee. I understand your principle of adding the constraint, but I’d be interested in knowing how you plan to drive the rotation.
There is a large evidence base to suggest external marker motion analysis is not accurate enough to drive seconday knee motion (STA error) with the current marker sets (Mod Helen Hayes).
Are you using technical marker sets on the Shank?
Have you thought about combined motion analysis and fluroscopy for driving a more accurate knee model?

best wishes

Peter