Contact distance estimation by a soft active whisker sensor based on morphological computation

Mammals use whiskers to sense their surrounding environments. By whisking over an object to transduce tactile signals (forces or moments) to mechanoreceptors at the snout, then transmitting this data to the somatosensory cortex in the brain, they can extract features such as contact distance, texture and shape of the object. In this study, we propose a morphological computation method to localize the contact position/locate the contacted object by investigating the induced strain, measured by a strain gauge representing sensory nerves, along the length of a whisker. To accomplish this task, an artificial tapered whisker sensor was made from a soft material (silicon rubber) to provide flexibility, sensitivity and more importantly adaptability. The first part of this paper introduces an analytical model of the proposed whisker based on elastic linear beam theory, and describes the unique correlations among the strain, contact distance, and whisker movements. The second part of this paper analyzes differences between the analytical model and a practical model to ascertain the optimum sensing conditions and any similarities in tactile behavior among the proposed whisker and a biological one. Our final goal is to give an idea of simple soft whisker-like sensory system which can be integrated in an autonomous robot.