FP Type 6

A Type 6 force platform records x, y, and z components for each of its four corners, named 1, 2, 3, and 4.

A Type 6 force platform records 12 ANALOG channels containing the following information:

[Original Analog]= [Fx1_original, Fy1_original, Fz1_original, Fx2_original, Fy2_original, Fz2_original, Fx3_original, Fy3_original, Fz3_original, Fx4_original, Fy4_original, Fz4_original]

A Type 6 force platform includes a 12×12 CalMatrix such that

[Fx1, Fy1, Fz1, Fx2, Fy2, Fz2, Fx3, Fy3, Fz3, Fx4, Fy4, Fz4] = [CalMatrix][Original Analog]

Calculating the desired force signals in the force platform's coordinate system consists of the following steps:

1. Compute baselines by averaging the analog signals for the specified FP_ZERO frames
2. Subtract each channel's baseline from its recorded signal
3. Calculate the the Ground Reaction Force
4. Apply a threshold
5. Transform the signals into the Laboratory Coordinate System

The Force vector for a Type 6 force platform is calculated as follows:

Force[X] = Fx1+Fx2+Fx3+Fx4
Force[Y] = Fy1+Fy2+Fy3+Fy4
Force[Z] = Fz1+Fz2+Fz3+Fz4

The COFP signal for a Type 6 force platform is calculated as follows:

COP[X] = (az0 * Force[X] - M[Y] / Force[Z]) + a
COP[Y] = (az0 * Force[Y] + M[X] /Force[Z]) + b
COP[Z] = az0

Where the moment of force is calculated as:

M[X] = b*( Fz1 + Fz2 - Fz3 - Fz4) + az0*(Fy1 + Fy2 + Fy3 + Fy4)
M[Y] = a*(-Fz1 + Fz2 + Fz3 - Fz4) - az0*(Fx1 + Fx2 + Fx3 + Fx4)
M[Z] = b*(-Fx1 - Fx2 + Fx3 + Fx4) + a*(Fy1 - Fy2 - Fy3 + Fy4)

and the ORIGIN vector is:

a = Origin[X]
b = Origin[Y]
az0 = Origin[Z]

The FreeMoment signal for a Type 6 force platform is calculated as follows:

FreeMoment[X] = 0
FreeMoment[Y] = 0
FreeMoment[Z] = M[Z] + Force[Y]*(M[Y]-az0*Force[X])/Force[Z] + Force[X]*(M[X]+az0*Force[Y])/Force[Z]

The transformation is defined by the location of the force platform corners, and is common to all force platforms.