Hi,
I want to run Bergmann. et al data in AnyBody. It will be based on GaitFullBody and GaitLowerExtremity.
In these two files, the input form of kinetic data is c3d. If I want to run Bergmann data (only has the joint rotation angle ralated with time), do I need to modify c3d file, or do I need to quit c3d file and put AnyBody kinematic functions in these two models?
Please could you elaborate the procedure?
Regards,
Jerry
Hi Jerry,
C3D files usually contain marker data and force platform data and AnyBody’s interface to C3D is set up to expect this contents by default. The Bergmann data, as far as I remember, is simply text files with joint angle variations, so to use those, you have to set up your model differently than the normal gait models. Each anatomical angle has to be driven directly by an interpolation driver the same way it is done in the FreePostureMove example.
In fact, our current gait models also work like that to some extent. You first run the parameter optimization, which uses the raw marker data. This process then saves the joint angle variations to text files, which are used to drive the joint angles in the subsequent inverse dynamic analysis. Perhaps you can just skip the first step and feed the Bergmann data directly into these files.
In terms of the force platforms, have a look at the way they are defined in the GaitVaughan model. You should be able to do the same.
By the way, when we processed the Hip98 CD data from Bergmann’s group several years ago we found that the force platform data was misaligned in most of the trials in the sense that the center of pressure was outside the footprint. We have found later that a lot of gait labs have force platforms that are inaccurate and need new calibration. This is because the labs previously only used the force data separately from the kinematic data. So please be careful when you process your data and make sure to visualize the center of pressure of the force platform and make sure that it is under the foot.
Best regards,
John