BTK use for perturbation platform

[suren]

Hi, 

  

    I am a beginner to use BTK toolbox and try to extract the analog data from c3d files (generated from Vicon Nexus) and in my case I am using a perturbation platform to measure the dynamic balance. When i used the BTK tool kit to extract the force and moments, It inverts the data and I get a Matlab warning as below

"Warning: Origin for the force platform #1 seems to be located from the center of the working surface instead of the inverse. Data are inverted to

locate the center of the working surface from the platform's origin. 

Warning: Origin for the force platform #2 seems to be located from the center of the working surface instead of the inverse. Data are inverted to

locate the center of the working surface from the platform's origin."

I am not very sure why it is this way. Also, I am not very sure how to calculate the joint angles during the perturbation as the time frame is very small. If someone has any idea on this issue,would be great. Thank You in advance.

Kind Regards,

Suren

[Arnaud Barré]

Hi Suren,

This is not an issue but more an information given to you. The C3D file format requires to store the coordinates of the force platform origin relative to its surface and expressed in the force platform reference axes. Some times ago Vicon did the opposite. BTK is able to detect that and sends you a warning. You will find more information on the website of the C3D file format : https://www.c3d.org/HTML/type21.htm

You can disable this warning if you want. See the following instructions : http://b-tk.googlecode.com/svn/doc/Matlab/0.3/_warnings_i_d.html

Arnaud

> --
> You received this message because you are subscribed to the Google Groups "BTK Users" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to btk-users+...@googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.