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  #1  
Old 05-23-2017, 12:42 PM
bokku01 bokku01 is offline
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Default Mocap Model Parameter study

Hi this is Bokku from Yonsei Univ. South Korea.

I am beginner of ANYBODY.
I would like to perform a parameter study using a mocap model with exotendon. However, a kinematical error occurs when doing the inversedynamics. Can you tell me what went wrong?
I attach the file I created as an attachment.
Attached Files
File Type: zip Model.zip (3.4 KB, 1 views)
File Type: any MoCap_FullBody.main.any (3.3 KB, 2 views)
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  #2  
Old 05-24-2017, 10:20 AM
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toerholm toerholm is offline
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Hi

I have been looking at the files you have uploaded.

From what i can see you have defined two new segments, and have created two AnyKinLinear measures.

So you have added 2x6 Dof to the model in terms of adding 2 new segments with 6 DOF each, but you have not added any kinematic constraints. When you add DOF to the model you need to add the same amount of constraints.

You have defined two AnyKinLinearMeasure's these will each measure 3 linear positions, but they will not actually drive the position. This means you need still to add 2x6 kinematic constraints to the model.


The missing constraints can be added in numerus way it really depends on what the model is supposed to do.

Example:
  1. a revolute joint between the segments, this will take 5 DOF away
  2. a standard joint between one of the segments and the Thigh? this would take 6 dof away
  3. add one linear constraint between the second segment and the shank.

This will add up to 12 DOF.

Please consider going though the first few tutorials available this will make these things much easier to understand.


I have not been able to debug the model but just looked at the files, please upload a complete model next time.

Best regards
Søren
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  #3  
Old 05-31-2017, 03:47 AM
bokku01 bokku01 is offline
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Default Mocap Model Parameter study

Thank you for your kind reply

As you said, I changed joint to std joint and after my model is running well.

But another problem came after that.

After analysis, the results(MaxAct, Metab) didn't show any differences according to the parameter.

I chose two parameters, one was force of exotendon, and another one was strain value.

I guess the place of parameter study code of my model was wrong.

Could you tell me what went wrong?


Best regards
Bokku
Attached Images
File Type: jpg ??1.JPG (31.1 KB, 1 views)
File Type: jpg ??.JPG (30.8 KB, 3 views)
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  #4  
Old 05-31-2017, 09:13 AM
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toerholm toerholm is offline
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Hi Bokku,

I am not sure what goes wrong here.

I can think of these things:
  1. Some of your code may not be inside the study or not referred to by the study
  2. There is no motion in the tendon?
  3. The MaxAct will display the max activity of any muscle in the model, there can be muscles which are not affected by this tendon and which are defining the max envelope... so no matter the force in the tendon they would remain the same ... e.g. an arm muscle

Best regards
Søren
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  #5  
Old 05-31-2017, 09:35 AM
bokku01 bokku01 is offline
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Default Mocap Model Parameter study

Thank you for your reply!!

I uploaded the modified inversedynamic.any file and the main.any file.

I guess these files are the cause.

I honestly did not understand the code of inversedynamics.any file and main.any file correctly.

Please review what went wrong.

Best regards

Bokku
Attached Files
File Type: any MoCap_FullBody.main.any (3.3 KB, 3 views)
File Type: any InverseDynamics.any (3.5 KB, 1 views)
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  #6  
Old 05-31-2017, 12:04 PM
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toerholm toerholm is offline
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Hi Bokku,

You write in the code :
Code:
//  Main.Studies.InverseDynamicStudy = {
//
  #include "Model/ExoTendon.any"
  #include "Model/ExoParameter.any"
//  
//};
This means that the tendon is not part of the study you are running.

You have created the tendon outside the study you are running and you have made a reference from the study to the tendon either. So effectively the tendon is not part of the analysis.

Please change the lines to be :


Code:
  Main.Studies.InverseDynamicStudy = {

  #include "Model/ExoTendon.any"
  #include "Model/ExoParameter.any"
  
};
Best regards
Søren
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  #7  
Old 06-15-2017, 06:06 AM
bokku01 bokku01 is offline
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Default Parameter study error

Hi again~

As you said, I performed the parameter study and I did it. Thank you for your kind reply.

But I have another question about coordinate problem i guess.

When I run my modified Mocap model, it seems well. But once I tried to run inversedynamic analysis or even initialcondition, my atteched tendon goes woring position. I attached pictures and files so help you understand my situation.

What should I fix my code?
Attached Images
File Type: jpg ??2.JPG (30.7 KB, 5 views)
File Type: jpg ??1.JPG (30.1 KB, 6 views)
Attached Files
File Type: zip Model (2).zip (3.5 KB, 2 views)
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  #8  
Old 06-15-2017, 09:27 AM
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toerholm toerholm is offline
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Hi Bokku,

I am not sure i understand the problem, please explain the issue you think you have in more detail.

I am guessing but maybe your are puzzeled about the two positions of the tendon? If the tendon is made as a shorthestpath this is normal... When the model starts running it will pull the muscle/tendon to one side as defined in a vector this could be what you see in pic1, then it releases the vector and it snaps onto the surface this is what you see in pic2. So this may not be a problem.

If you think i have misunderstood your email, then please write again.

Best regards
Søren
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  #9  
Old 06-15-2017, 10:01 AM
bokku01 bokku01 is offline
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Default Parameter study error

Actually, I didn't use shortestpath function.

It seems the coordinate is changing between the loading of my Mocap model(picture1) and the running inversedynamic analysis(picture2).(as I attached the pictures in the previous post)

My guess is that the coordinate of my c3d data is different from the Mocap model. So I changed the z direction of Mocap model as vertical direction which is originally y direction.

So I just thought my analysis went wrong due to the coordinate change. But it is just my guess..
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  #10  
Old 06-15-2017, 10:15 AM
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toerholm toerholm is offline
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Hi Bokku,

It is normal to see differences between a loading position pic1 and the position found after analysis pic2?

These will only be exactly the same if all segments in the model has been created in a way so that .r0 and .Axes0 are well defined e.g. same position as after solving initpos.

If you think you still have problems, please write agian and describe in more detail what you think is the issue.

Best regards
Søren
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