Theoretical and experimental investigations of multiple contact points between a biologically inspired tactile sensor and various objects

Abstract

The somatosensory system of mammals includes sensory hairs (vibrissae) for tactile perception during near field exploration. Interacting with the environment, the tactile hair transfers mechanical stimuli to the hair follicle (follicle-sinus complex). The follicle-sinus complex transduces the singnals and transmits them to the central nervous system. Rats, e.g., are able to characterize objects with regard to their surface and geometric shape. Inspired by the biological paragon, the implementation of a vibrissa-like tactile sensor is an object of engineering research. According to the sensory organ, the function of a technical vibrissa is based on the recording of stimuli by the artificial hair shaft and their measurement at the support. This enables the detection of technically relevant information. In this context, the present work focuses on the task of object contour reconstruction. For that purpose, the support reactions are determined during scanning of an object. Previous investigations have been restricted on scanning objects with convex contours. This is due to the limitation of mechanical models to single-point contact scenarios. Goal of the present work is the consideration of multiple contact points between sensor shaft and object contour. The sensor shaft is modelled as a Euler-Bernoulli beam. The mathematical/theoretical description of the deformation of the beam during quasi-static scanning results in a multipoint boundary value problem with switching point. In order to simulate scanning sweeps along two different object types, the corresponding multipoint boundary value problems are solved by applying a shooting method incooperating a Runge Kutta Method of 4th order. The support reactions are calculated during scanning. It shows that multi-point contacts can be identified in the support reactions. The simulation is validated by experiments using selected examples.