Effect of fingerpad mechanics and anatomical structures on tactile detection of compliant object

Human fingerpad and planar objects in contact constitute a complex mechanical system, and contact mechanics involving in this system is important for object recognition and tactile virtual rendering. Although the interactions of fingerpad and compliant planar objects are common, there are not general mechanistic models for fingerpad and planar objects in contact to uncover the role of contact deformation dependent on skin mechanics and anatomical structures in tactile recognition. A 2-D FE model combined with Augmented Lagrange algorithm, from the physiological characteristics of fingerpad, is developed to simulate the interactions between fingerpad and compliant plates with finite thickness, and attempts are made to develop an analytical models of total contact force versus indentation, or contact-area radius, and spatial distribution profiles of contact pressure, respectively. It is demonstrated that the exponential law is more approximate than the power law in describing the compressive stress-strain behaviors of soft tissues within fingertip in the case of human fingerpad against planar objects. However, in the case of contact force versus contact-area radius, the power law is more suitable. In addition, the study indicates that the contact pressure decays following an exponential law away from the contact center. By multiplying the exponential term dependent on bone width into Hertz contact pressure model, a modified model can describe well the spatial contact pressure profiles.