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3D visualization of GRF

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Petcu Daniel, Jan 25, 2012.

  1. Petcu Daniel

    Petcu Daniel Active Member


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    Hello,

    I would like to visualize in 3D the GRF vector as it results from an AMTI force platform data. I'm thinking at an open-source software ...

    Thank you for any suggestion !
    Daniel
     
  2. Daniel, I'd ask the same question on Biomech-l, you are more likely to find the answer you seek there. http://biomch-l.isbweb.org/forum.php
     
  3. Petcu Daniel

    Petcu Daniel Active Member

    Thanks for Biomech-l ! Unfortunately, I wasn't able to find a solution there. So I've tried with FreeMat and with a small script I succeed to obtain something like in the attached view !

    Now, I have to verify if it is a correct representation of GRF !

    Daniel
     

    Attached Files:

  4. Griff

    Griff Moderator

    Did you ask the question on Biomch-L Daniel? I didn't notice it over the last week if you did.
     
  5. Petcu Daniel

    Petcu Daniel Active Member

    No, I didn't ! I thought that I'll find a similar question with an answer, but I didn't succeed to find one ! Probably I didn't search well! Do you know if there is an answer at this question on Biomech-L ?

    Thanks !
     
  6. Petcu Daniel

    Petcu Daniel Active Member

    I've asked and I've received some answers !
    Thank you !

    Daniel
     
  7. David Smith

    David Smith Well-Known Member


    I've only just noticed this question and spookily enough someone else had been asking the me same question, You can do it in MS Excel but I can't attach an Excel file here to show you how.

    Dave
     
  8. Petcu Daniel

    Petcu Daniel Active Member

    I know the method to vizualize GRF through a Pedotti diagram -from "Constructing a Pedotti diagram using excel charts",Srinivas B.S. Kambhampati, Journal of Biomechanics 40 (2007). But, as far as I know, Excell doesn't allow 3d charts ! Maybe new versions ?

    Regards,
    Daniel
     
  9. David Smith

    David Smith Well-Known Member

    Ah! I see, you want a 3D characterisation of the resultant force vectors, I was thinking that you wanted to find the single 3D resultant vector of the 3 xyz orthogonal force data that you have from the AMTI system.

    Dave
     
  10. David Smith

    David Smith Well-Known Member

  11. Petcu Daniel

    Petcu Daniel Active Member

    Yes, this is!
    And it create me another problem when I'm trying to represent in 3D the average GRF vector of a number of trials. Because I've need an "average COP trajectory"! The reason for which I've started the thread "Average COP trajectory".
    Any help will be very appreciated !

    Thanks,
    Daniel
     
  12. David Smith

    David Smith Well-Known Member

  13. Petcu Daniel

    Petcu Daniel Active Member

    Hello,


    Starting from this thread and from suggestion to find an answer on http://biomch-l.isbweb.org/forum.php I've found Mokka - an open-source software for analyzing of biomechanical data : http://b-tk.googlecode.com/svn/web/mokka/index.html

    Thanks to Arnaud Barre in the version 0.5.1 it was introduced the option to visualize in 3D the GRF vector as it results from an AMTI force platform data [see attached image]. Also , I think it is an interesting item the possibility to calculate the angle of direction of GRF vector !



    Thank you,

    Daniel
     

    Attached Files:

  14. efuller

    efuller MVP

    That got me thinking as to what you could use the angle of the vector for.

    You do need to have the angle of the vector to calculate the moment about the STJ axis. I am having a hard time figuring out what else that you could do with the vector that you couldn't do with just one of the components.

    I've always wanted to look at the posterior to anterior shear after heel off before and after treatment. This would look at the concept of propulsion. This concept was taught when I was in podiatry school and it was thought that this was a good thing and an indication of orthotic effectiveness. Contrary to what some sagittal plane facilitators think, you can push the trailing limb forward.

    Eric
     
  15. Nice work, Daniel :drinks
     
  16. Petcu Daniel

    Petcu Daniel Active Member

    The idea of evaluating the direction of GRF vector was inspired by the article "In-Shoe Pressure Measurement and Foot Orthosis Research A Giant Leap Forward or a Step Too Far?"
    There is one question regarding the definition of GRF vector's angles :
    - in the attached image there are :
    -1. the definition of GRF vector's angles as it is implemented in Mokka - figure 1
    -2. the definition of GRF vector's angles as the angle between the vector's direction and the planes of the reference system - figure 2

    Which one do you think is more useful ?

    Another point is, according to the developer, Mokka is using PWA (point of wrench application-using all the components of the forces and moments measured by force platform) instead of COP as it is calculated by force platform, only from the Mx and My moments and the Fz force [reference: http://books.google.ch/books?id=wp3z...page&q&f=false ]

    Sincerely,
    Daniel
     

    Attached Files:

    Last edited: Apr 18, 2012
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