Segment Origin

Main Forum
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Hi,
I have posted similar messages before, however, I’m now trying to use the Leg_TD model. My model is based on the standard FreePostureMove model.
I am simply trying to add a dummy segment to a current segment and drive the location of the dummy segment relative to the original. But in Leg_TD the reference axis of the segment is not “in the middle of” the segment. So I use the AnyKinEqInterPolDriver to try to drive the location of the new segment relative to the original. But because of the axis offset of the original, how do I apply that using the AnyKinEqInterPolDriver?

I only want to drive the dummy segment in the long-axis of the original segment - the y-axis. However, even is the data input into this function has zeros in the x and z columns, and non-zero data in the y, the model doesn’t always replicate this, and for example the interpolated x data is not always zero.

I’m not sure clear this may be, but would greatly appreciate any thoughts you may have!

Many thanks,
Chris Phillips

2

Hi,

Would you please upload your model in the debug section?
Also it is encouraged for you to write the version of your AMS and AMMR.

Best regards,
Moonki

3

Hi Moonki,
I’m using AnyBody v 5.2.0 AMMR 1.4.1. The model is simply the standard FreePostureMove.main.any model with the leg models set to Leg_TD.
I then #include the attatched file into the environment folder. However, I guess my file assumes that the segment axis is at the center of the segment, which in the Leg_TD it’s not. I’m just a little unsure as to how include this offset.

Many thanks,
Chris

4

Hi,

Attached please find a modified version of your original model.

Now, I’ve just modified the FreePostureMove model to include the LegTD setting. Now it works well.

But the issue is, ‘how can we define the middle node of the shank segment?’.

So I assumed that the middle node can be located as the average position between the knee and the ankle joints.

And the ARel value of that node should be same as the ARel of the scaling node of shank.

First, please check whether the definition of the node is proper to your research purpose.

Then, you can ask additional questions.

In fact, I have no idea what you would like to do with AnyBody Modeling System.

I hope this may help you.

Best regards,
Moonki

5

Many thanks Moonki. I think I should try to read (re-read!) the information about scaling to get a firmer understanding.
I’m trying to simulate the time-varying fluid forces acting on a body while swimming. The idea being to find the magnitude and center of pressure (using some theory implemented in a Matlab script) and apply this to the various segments of the body. I guess in reality it doesn’t matter where my reference point is, but I’d started out using the middle of the segment and was struggling to find that point in the Leg_TD model.

A fairly basic question on forces and moments in AnyBody (more of a sanity check!)… If I have a force acting on the shank seg but the distance from the knee joint is zero then there is no moment about that joint, however, this would create a moment about the hip? However, if I applied a moment about the knee, and the moment was 0N (similar to the previous case) but this wouldn’t create any moment at the hip? And similarly if there was a moment of say 10N about the knee, this doesn’t then create a moment at the hip joint?

Regards,
Chris

6

Hi Chris,

It seems that you want to see the ‘effect’ of the fluid force acting on ‘thigh’ because it may cause some moments of hip joints.

There is a good class for your purpose. The name is ‘AnyForceMomentMeasure2’ class.

Here is an example of this class:
http://wiki.anyscript.org/images/b/b2/Muscle_Moment_Measure_example.any

Before using this, please read the description of this class in the reference manual carefully.

I hope this may help you.

Best regards,
Moonki

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