Finger Force Direction Recognition by Principal Component Analysis of Fingernail Coloration Pattern

A method based on principal component analysis of the fingernail coloration pattern is presented to infer fingertip force direction during planar contact. Images from 7 subjects were registered and normalized to each other. Results show that the fingernail coloration patterns are similar for the 7 subjects, but the feature centroids vary. It is concluded that there are common features for all people. But accurate detection of fingertip force direction requires individually calibrated centroids