Piezo-dynamometric platform for a more complete analysis of foot-to-floor interaction.

A compound instrument was constructed by superimposing a dedicated pressure platform on a commercial force platform. This instrument simultaneously estimates the ground reaction force resultants (vertical and shear forces, free moment and location of the center of pressure), pressure distribution throughout the foot-floor contact area, the trajectory of the center of pressure superimposed on the contact area (footprint). On the basis of the readings provided by the force plate we calibrated pressure sensors more accurately. We could therefore accurately estimate the vertical local components of the ground reaction. This information and the measured shear force resultants were essential for computing the shear forces acting on elementary areas corresponding to the active surface of each pressure sensor. This, in turn, allowed us to estimate the vertical and shear force resultants and free moment for subareas of the foot. This is a feature peculiar to this compound instrument, and for its effective exploitation we have implemented a few methods for the reliable identification of the subareas of interest. Two application instances are hereby reported.