My name is Arnaud BARRÉ and I’m presently working on a project to
estimate contact forces in the knee joint during the gait cycle. I’m
using a VICON motion analysis system to obtain kinematics data during
gait and we use a ADAL 3D treadmill to mesure the ground reaction
forces and I would want to use the AnyBody Software to estimate
contact forces at the knee joint.
I’d like to know if it is possible to create function or overload it.
For example I use wrench notation for my inverse dynamic program and
i’d like to use it in AnyBody software. Is it possible ?
Is it possible to drive joint forces or plate force with data in a
file ?
I’ve been using the Anybody software only for a week now, so i’m
sorry if my questions are not relevant.
This is not currently possible. AnyScript is a purely declarative
language. This means that you can declare objects such as bones and
joints, and as soon as you have declared them, they become parts of
the mechanical system.
Actually, it should not be necessary to create your own inverse
dynamics functions, since all that is already built into AnyBody.
AnyBody will automatically compute the contact forces in the knee
joint depending on how you have defined the leg model. The model
repository currently has a 2-D and a 3-D leg model. There is a long
story behind those models and their different properties. The
definition of the knee is also an important issue, but all those are
probably beyond the scope of this post. Let me just mention that the
next version of the repository will contain a new knee model. You
can find a description in our Christmas newsletter here: http://www.anybodytech.com/116.0.html?&tx_ttnews[tt_news]
=10&tx_ttnews[backPid]=37&cHash=d80e8fd795
(this entire link must be on a single line)
Imposing force plate data
This is possible and probably necessary to get a good result from
gait analysis. In the current version (1.3) you need to make a small
workaround. The workaround is to create a dummy segment and drive
one of its coordinates according to the GRF. The you define a force
under the foot and set it equal to the dummy segment’s position.
Write again when you get to it, and we will help you get it defined
correctly.
In the next version (2.0) this workaround will be eliminated, and
you can define the force directly as an interpolation function
between measured data from the force plate.
Finally a tip:
In the files section you will find a sample model that demonstrates
how to drive a model by means of marker coordinates as you get them
from Vison.