Studies of the Mechanical Impedance of the Index Finger in Multiple Dimensions

For both, the analysis of haptic interaction and the quantification of haptic perception a profound knowledge of the mechanical impedance of human touch are needed. Several models for a user’s impedance have been suggested in literature and some guidelines and quantitative values from independent models for different contact situations are available. However for the analysis of haptic interaction and the quantification of perception it is necessary to allow comparison between different grasps. Therefore a reduced set of models which covers many types of touch in an acceptable quality would be ideal. Additionally the influence of the change of touch – the pretension of fingers – on the impedance is seldom referred to and even more seldom quantified.

In 2005 the authors defined a method to quantify the impedance of a three finger precision grasp. In continuation of this approach and with the aim to collect a catalogue of impedance measures, this document presents results from set of 192 measurements regarding the impedance of the index finger from eight subjects. The resulting models and their dependencies are given as approximated plots of the impedance in dependency of frequency, direction of touch and size of the contact area. The resulting curves are discussed and put into context of the influence of impedance.