Singular-value and finite-element analysis of tactile shape recognition

Detecting the surface shape or pressure distribution of a tactile sensor made of a homogeneous and elastic material, given internal stresses or strains, is an ill-posed problem. The difficulties are further compounded by introduction of inhomogeneities into the sensor material in order to perform the transduction, which significantly change the sensor´s mechanical behaviour. In order to investigate the numerical stability of curvature detection, we discretized a linear elastic half-space. Using closed-form solutions of surface pressures for rigid indentors, a regularized solution can be formulated. From finite-element models of inhomogeneous 3D tactile sensors, subsurface strains can be estimated in a physically realistic fashion. Using these as input to the regularized solution, we have found that it is not possible to reliably deduce the difference between contacting the sensor´s surface with various axisymmetric objects