3-D Finite Element Analysis of Elastic Continua for Tactile Sensing.

Sensing elements in tactile arrays are often covered for protection by a layer of complaint polymer. The responses of these sensors are determined by the mechanical filtering that occurs between objects indenting the surface and the sensing elements below. To characterize the stress and strain fields that result from contact at the surface, a finite element method is described that allows the stress tensor at any point in the interior of the elastic layer to be calculated. This method requires that the area of contact and distribution of pressure be known. Given this information the interaction between an object and the elastic layer is modeled as an arbitrarily dense array of point loads indenting the surface. The stress tensor at any point within the layer is then calculated as the sum of the tensors produced by each of the discrete point loads. Using this method a detailed analysis of a sphere indenting an elastic layer is performed. The results are used to illustrate several filtering methods for the determination of contact boundaries and for the calculation of normal versus shear force ratios.