HAS-Motion Software Documentation

The FP_TYPE force platform parameter indicates the type of force platform used in the C3D file. This is important as different force platforms record a different number of analog channels and store different information in these channels. Understanding the type of force platform used allows Visual3D to correctly compute the desired Force, Centre of Pressure, and Free Moment signals from the recorded analog signals.

More in-depth information about each force platform type is available on the respective page:

Channel contents for Types 3, 6, and 7 refer to the four corners of the force platform numbered 1, 2, 3, and 4.

Channel contents for Type 5 refer to the four corners of the force platform named A, B, C, and D.

A CalMatrix (or Inverse Sensitivity Matrix) is used to pre-multiply the original analog signal recorded when required by the force platform type.

Force platforms of Type 4 include a 6×6 CalMatrix. Type 2 platforms can be thought of as Type 4 platforms where the CalMatrix is the identity matrix.

Force platforms of Type 7 include a 12×12 CalMatrix. Type 3 platforms can be thought of as Type 7 platforms where the CalMatrix is the identity matrix.

Although each force platform type records different information in its different channels, the process for converting the original recorded analog signals into the desired Force, COFP, and FreeMoment signals follows the same common steps:

1. Compute baselines
2. Subtract baselines from original signals
3. Pre-multiply by the calibration matrix (if applicable)
4. Calculate the Ground Reaction Force
5. Apply a threshold
6. Transform data to the Laboratory Coordinate System