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  #11  
Old 06-15-2017, 11:08 AM
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toerholm toerholm is offline
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Hi Bokku,

I am sorry but please describe what you think is the problem i have not understood this.

It is normal to see a difference between a loading position and a running position, this is not a wrong and not a problem. The loading position only needs to be good enough so that the model is assembling correctly in the first time step, the loading position will not alter results, only if the model do not assemble correctly.

Please describe what is the problem?

Best regards
Søren
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  #12  
Old 06-15-2017, 11:48 AM
bokku01 bokku01 is offline
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Default Parameter study error

Originally, I tried to do the parameter study about exotendon according to the position. The exotendon is consists of two and connected from shoulder to the pelvis, right,left so total 4 tendon(AnyViaPointLigament) used to do the analysis. My plan was the position parameter study of the middle point of each exotendon. In other words, I wanted to find x,y position of middle point of exotendon according to the object function(which is the lowest value of sum of metabolic energy of some muscles etc.). So I set up the parameter like picture 1 as I attached, but once I ran the inversedynamicanalysis or parameterstudy, the middle point of exotendon placed wrong position(picture 2). I guess the coordinate is misplaced or used wrong.

Because I am beginner of this problem, so (I am pretty sure that) I misused something or misunderstood something about this program.

If you still don't understand about my problem, I will explain more specifically.

Thank you
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  #13  
Old 06-15-2017, 01:14 PM
toerholm's Avatar
toerholm toerholm is offline
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Hi Bokku,

Thanks now i understand better

I have looked at the files you have uploaded.

Here are my findings:
  1. In Exotendon.any you have tendons lig1 and lig2 which spans nodes on the same segment... so the length between these nodes will never change and the ligament will nto be stretched at any point.
  2. You have only include the Exotendon and exoParamters into the InverseDynamicStuy, this means that if you runnig any other study such as the parameter study you will not see the exo model to be updated... it will stay in load position.. i think this exoplains the difference between the images...


Please note that the parameter study in the mocap model is not suited for for what you are trying to do here... it is designed to run a parameter optimization on the kinematics in the model.

As i understand your problem you woudl like to do a paramter study on the position of the connection point between the tensdons.

To do that please follwo these steps:

  1. Follow the tutorial on parameter and optimization this will make things more clear
  2. Define a new parameter study in the model next to the inverse study.
  3. Make your positions of the connector segment a design variable
  4. Create an AnyOutput function for your objective function the metabolic energy.
  5. Run the parameter study and find the design var value with lowest energy


Alternatively to this it could be done usign an FDK approach, so having a free segment sliding on back of the spine and four springs which would determine the position of the segment. Fundamentally both ways (if set up in a similar way) would give same results.

Sorry for any typos.

Best regards
Søren
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