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Re: Summary: force plate issue

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  • Re: Summary: force plate issue

    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:
    >The 'c' of your equations is here called Zoff - I have also often (e.g.
    Dave Winter's books) seen it signified by Dz.

    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: Or if you are interested in the
    force-plate-related issues in general, I recommend 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

    Young-Hoo Kwon, Ph.D.
    Biomechanics Laboratory
    Texas Woman's University
    Phone & Fax: (940) 898-2598 /