====== FP Type 2 ======

==== Channels ====
A Type 2 force platform records 6 ANALOG channels containing the following information:
<code>
[Original Analog] = [Fx, Fy, Fz, Mx, My, Mz]
</code>

Note that a [[visual3d:documentation:pipeline:force_commands:fp_type_4|Type 4]] force platform has the same analog channels as a Type 2 force platform but also includes a CalMatrix. Alternatively, a Type 2 force platform can be thought of as a Type 4 force platform where the CalMatrix is the identity matrix.

==== Calculating the Force Signals ====

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

  - Compute baselines by averaging the analog signals for the specified [[Visual3D:Documentation:Pipeline:Force_Commands:FP_ZERO|FP_ZERO]] frames
  - Subtract each channel's baseline from its recorded signal
  - Calculate the the Ground Reaction Force
  - Apply a threshold
  - Transform the signals into the [[visual3d:documentation:definitions:laboratory_coordinate_system|Laboratory Coordinate System]]

=== Force Vector ===

The Force vector for a Type 2 force platform is calculated as follows:
<code>
Force[X]= Fx
Force[Y]= Fy
Force[Z]= Fz
</code>

=== Compute Centre of Pressure ===

The COFP signal for a Type 2 force platform is calculated as follows:
<code>
COP[X]= (ORIGIN[Z]*Force[X] - M[Y]) / Force[Z]
COP[Y]= (M[X] + ORIGIN[Z]*Force[Y]) / Force[Z]
COP[Z]= ORIGIN[Z]
</code>

Where 
<code>
M[X]= Mx*LengthConversion
M[Y]= My*LengthConversion
M[Z]= Mz*LengthConversion
</code>

and where
<code>
LengthConversion = Point units conversion to meters
</code>
for example, if the POINT units are millimetres then the LengthConversion term is 0.001.

**Note:** When comparing Type 2 and Type 4 force platforms, the LengthConversion term for Type 4 force platforms is always 1 because this conversion is part of the CalMatrix.

=== Compute Free Moment ===

The FreeMoment signal for a Type 2 force platform is calculated as follows:
<code>
FreeMoment[X]= 0
FreeMoment[Y]= 0
FreeMoment[Z]= M[Z] - ( COP[X]*Force[Y] - COP[Y]*Force[X] )
</code>

=== Transforming Signals into the Laboratory Coordinate System ===

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