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Measurement of human arm's position and torque

KP_PC k.p.collins at worldnet.att.net
Wed Nov 5 12:13:02 EST 2003

"Panagiotis Artemiadis" <partem at mail.ntua.gr> wrote in message
news:bob4n3$28qd$1 at ulysses.noc.ntua.gr...
| Do you have any idea of how can i measure
| the position and joint torque of the human arm
| during a movement?
| Thank you in advance
| P.A.

It's simple.

All that's required is Newton's f = ma.

Have your subject hold a standard mass in
his hand.

Record video as he moves his arm.

Then, to your criterion for exactness,
analyze the video. This can be done
on a frame-by-frame basis, translating
it all into 'levers', with respect to which,
[since the mass of the arm is 'constant']
the motion of the standard mass allows
everything to be calculated.

Once you've collected a standardized
set of motion-data [incorporating a wide
range of accellerations ["range-widely :-]]
you don't have to do any more data col-
ection because you can translate it to an
adequate(?) approximation of all pos-
sible masses by just substituting numer-
ical masses.

Or, if you have the $ to be 'fancy', put a
little audio-transmitter in the mass, and
disperse audio-receivers in a 3-D way
that allows you to triangulate via doppler-
shifts. [Polaroid Corporation used to sell
everything needed [at reasonable rates],
but that was a couple of decades ago, so
I'm not sure if they still manufacture the
kits.] Then you can write a computer
program that will give you the information
you seek in real 'time'.

Or, if you just want to have fun, 'suspend'
your subject in a 'webbing' that's comprised
of orthogonally-ordered spring scales. Here,
the readings would be 'isometric', with the
subject holding his position while you read
all the scales. This last method would give
a lot of smiles [and probably some deep
insights into your subject's psychological
predispositions :-]

k. p. collins

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