Object Shape Recognition and Reconstruction Using Pivoted Tactile Sensors

L Merker,C Behn,C Will,J Steigenberger

doi:10.1155/2018/1613945

Abstract

Many mammals use some special tactile hairs, the so-called mystacial macrovibrissae, to acquire information about their environment. In doing so, rats and mice, e.g., are able to detect object distances, shapes, and surface textures. Inspired by the biological paradigm, we present a mechanical model for object contour scanning and shape reconstruction, considering a single vibrissa as a cylindrically shaped Euler-Bernoulli-bending rod, which is pivoted by a bearing. In doing so, we adapt our model for a rotational scanning movement, which is in contrast to many previous modeling approaches. Describing a single rotational quasi-static sweep of the vibrissa along a strict convex contour function using nonlinear Euler-Bernoulli theory, we end up in a boundary-value problem with some unknown parameters. In a first step, we use shooting methods in an algorithm to repeatedly solve this boundary-value problem (changing the vibrissa base angle) and generate the support reactions during a sweep along an object contour. Afterwards, we use these support reactions to reconstruct the object contour solving an initial-value problem. Finally, we extend the scanning process adding a second sweep of the vibrissa in opposite direction in order to enlarge the reconstructable area of the profile.

Highlights

Tactile sensors are frequently used in uncertain environments, where optical sensors reach their capability
In many areas of application, e.g., in mobile robotics, tactile sensors are designed from simple passive impact sensors all the way through to complex, integrated systems, giving more detailed contact information
The facial vibrissae array consists of a variety of vibrissal systems, each consisting of a hair shaft, which is embedded in its own support— the so-called follicle-sinus complex (FSC)

Summary

Introduction

Tactile sensors are frequently used in uncertain (changing, dark, noisy) environments, where optical sensors reach their capability. A big disadvantage of using only small pushing angles is the need of changing the support position in order to scan a larger part of the object contour This problem does not occur within the present paper. The scanning process is treated analytically as far as possible in order to generate the unknown support reactions, when the rod is swept along a profile contour This analytical approach is in contrast to just performing experiments and measurements. Some publications take various morphological characteristics like the elasticity of the FSC [17] or the tapered and precurved geometry of a vibrissa into account [20,21,22,23], there is no mechanical model for generating the support reactions during a rotatory scanning sweep as well. The governed results extend and complement the ones from [13,14,15,16,17, 24]

General Modeling of a Rotational Sweep

Conclusion and Outlook