kwon3d

10-17-2005, 01:20 PM

Dear all,

The following is what Chris Kirtley sent me but I believe he meant to send

it to Biomch-L.

>Dear Kwon, Tomislav and all,

>

>It is worth noting that in AMTI plates (and Bertec, I think?) the total net

forces and moments on the plate: Fx,y,z and Mx,y,z (6 variables) are derived

by suitable manipulation (in hardware), and ouput directly. The equations

then simplify: see my scan of an AMTI manual:

http://www.univie.ac.at/cga/faq/CoP.GIF

>

>The 'c' of your equations is here called Zoff - I have also often (e.g.

Dave Winter's books) seen it signified by Dz.

>

>Chris

Probably, one of the best places to see a complete set of CP & Tz equations

for the AMTI (Bertec) plates and Kistler plates will be my webpage:

http://kwon3d.com/theory/grf/cop.html. Or if you are interested in the

force-plate-related issues in general, I recommend

http://kwon3d.com/theory/grf/grf.html. The CP (X and Y) & Tz equations for

an AMTI plate are actually more complex than what Chris scanned because it

has something called the 'true origin':

X = [ My + c*Fx ] / Fz + a [1]

Y = [ Mx - c*Fy ] / Fz + b [2]

Tz = Mz - ( x - a )*Fy + ( y - b )*Fx [3]

where ( a, b, c ) = true origin of the plate (c < 0). 'a' and 'b' for a

Bertec plate are equal to 0 but those for an AMTI plate are not. Consult the

manual and the calibration sheet of the AMTI plate for the true origin

coordinates.

Young-Hoo

-------------------------------------------------------------------

Young-Hoo Kwon, Ph.D.

Biomechanics Laboratory

Texas Woman's University

Phone & Fax: (940) 898-2598

ykwon@mail.twu.edu / kwon3d@kwon3d.com

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The following is what Chris Kirtley sent me but I believe he meant to send

it to Biomch-L.

>Dear Kwon, Tomislav and all,

>

>It is worth noting that in AMTI plates (and Bertec, I think?) the total net

forces and moments on the plate: Fx,y,z and Mx,y,z (6 variables) are derived

by suitable manipulation (in hardware), and ouput directly. The equations

then simplify: see my scan of an AMTI manual:

http://www.univie.ac.at/cga/faq/CoP.GIF

>

>The 'c' of your equations is here called Zoff - I have also often (e.g.

Dave Winter's books) seen it signified by Dz.

>

>Chris

Probably, one of the best places to see a complete set of CP & Tz equations

for the AMTI (Bertec) plates and Kistler plates will be my webpage:

http://kwon3d.com/theory/grf/cop.html. Or if you are interested in the

force-plate-related issues in general, I recommend

http://kwon3d.com/theory/grf/grf.html. The CP (X and Y) & Tz equations for

an AMTI plate are actually more complex than what Chris scanned because it

has something called the 'true origin':

X = [ My + c*Fx ] / Fz + a [1]

Y = [ Mx - c*Fy ] / Fz + b [2]

Tz = Mz - ( x - a )*Fy + ( y - b )*Fx [3]

where ( a, b, c ) = true origin of the plate (c < 0). 'a' and 'b' for a

Bertec plate are equal to 0 but those for an AMTI plate are not. Consult the

manual and the calibration sheet of the AMTI plate for the true origin

coordinates.

Young-Hoo

-------------------------------------------------------------------

Young-Hoo Kwon, Ph.D.

Biomechanics Laboratory

Texas Woman's University

Phone & Fax: (940) 898-2598

ykwon@mail.twu.edu / kwon3d@kwon3d.com

--------------------------------------------------------------------