# [ODE] Re: Scientific modelling of a runner

Martin Baeker martin.baeker at tu-bs.de
Fri Sep 23 09:32:36 MST 2005

```Hello all,

thanks for the lots of replies to my question. I was not in the least
aware how many people were working in this field (because stupid me
only thought of science, not of things like people animations for
entertainment, movies etc.)

So here is a more precise description of what I want to do, which is
much simpler, I think, than what my initial question implied:

The problem I am working on is a scientific study of bipedal
locomotion of birds and dinosaurs.  What I want to do is estimate the
muscle force needed for bipedal running. This of course depends on the
exact sequence of motion i.e., on the position of the leg segments in
each part of the gait which is obviously unknown for extinct animals.

Therefore I want to use an optimization procedure to find the gait
with the highest possible speed with a given muscle mass. What the
program I am looking for should do for me is the following: Given a
fixed number (about 5 or 7) of leg positions (that was what I meant by
"frames") , described by the angles between the leg segments (angle
between hip and femur, femur and shank, shank and foot, foot and toe)
at fixed times, calculate the forces and moments needed to move from
one time step to another, including inertial forces and ground
reaction force.

So the input would look like the following sketches:

\
\
\_

\
/
\_

/
/
\_

/
/
/_

And the output should be the forces and moments (averaged over time
step) on each leg segment needed to get from one frame to the next.

The path of motion from one position to the other is rather simple, as
all angles can be assumed to change by a constant rate between the
steps. So the usual optimization needed in robotics is of secondary
importance here - I simply need a tool to calculate the forces and
moments. In addition, the model is 2-dimensional.

I hope this describes it more clearly. Can this kind of thing be done
in ODE and, if so, what is the precision I can expect on the moments?
(It was stated that it may be low which would not be acceptable here.)
If not, is there another software available for this kind of things?
It can be done using rigid body dynamics in the finite element code
ABAQUS, I think, but this seems a bit like an overkill tool for this problem.

Thanks a lot for any help,

best regards,

Martin.

Priv.-Doz. Dr. Martin Bäker
Institut für Werkstoffe
Langer Kamp 8
38106 Braunschweig
Germany
Tel.: 00-49-531-391-3073
Fax   00-49-531-391-3058
e-mail <martin.baeker at tu-bs.de>

```

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