Measurement of human arm's position and torque
k.p.collins at worldnet.att.net
Thu Nov 6 15:50:46 EST 2003
"Panagiotis Artemiadis" <partem at mail.ntua.gr> wrote in message
news:bocp31$28io$1 at ulysses.noc.ntua.gr...
| But what about the mass of the human arm?
In vectorizing the body's motion, the mass of the
body [the arm] can be treated as constant. Con-
stants drop out of the calculations. [In reality,
there are moment-of-inertia changes as muscles
contract and expand, and as generalized con-
sequences of exercise [fluid loss and its dist-
ribution, stored-energy consumption, oxygen
intake, vasodilation, etc.] but if you want to
calculate at that 'level', you still have to construct
a 'platform' for calculating at that 'level' by, first,
doing the simple thing.
I gave you all you need in my prior post - except
that you need at least two cameras if you don't
want to 'guess' with respect to 'depth' info in a
single camera's field of view. Orient the cameras'
viewing axes at right angles [cheap internet cam-
eras will do.
All the calculations you need can be found in an
introductory Physics textbook. Thumb through
the first few chapters looking for lever-arm prob-
lems. The body's skeleton is just a bunch of
such lever arms.
Come to think of it, there should be software
that help you with all of this - look up Fractal
Design Poser. I don't think it does stuff with
added masses, though, but perhaps it would
help provide the vectorization as data that you
It's an interesting exploration with respect to
nervous system function. I can't toss anything
at a waste basket, or a garbage bin, without
marvelling at the great ease with which nervous
systems calculate the necessary effector act-
ivations, despite the widely-varying masses
that can be involved [including the inferior
olive's 'crumpled-bag' nucleus coordinate
system translation dynamics that are dis-
cussed, and reduced to TD E/I-minimization,
in AoK, Ap6 [for those who have AoK].
But, sorry, I won't do the calcs for you.
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