Effects of Multi-Point Contacts during Object Contour Scanning Using a Biologically-Inspired Tactile Sensor.

Lukas Merker,Sebastian J Fischer Calderon,Jorge H Alencastre Miranda,Carsten Behn,Moritz Scharff

doi:10.3390/s20072077

Abstract

Vibrissae are an important tactile sense organ of many mammals, in particular rodents like rats and mice. For instance, these animals use them in order to detect different object features, e.g., object-distances and -shapes. In engineering, vibrissae have long been established as a natural paragon for developing tactile sensors. So far, having object shape scanning and reconstruction in mind, almost all mechanical vibrissa models are restricted to contact scenarios with a single discrete contact force. Here, we deal with the effect of multi-point contacts in a specific scanning scenario, where an artificial vibrissa is swept along partly concave object contours. The vibrissa is modeled as a cylindrical, one-sided clamped Euler-Bernoulli bending rod undergoing large deflections. The elasticae and the support reactions during scanning are theoretically calculated and measured in experiments, using a spring steel wire, attached to a force/torque-sensor. The experiments validate the simulation results and show that the assumption of a quasi-static scanning displacement is a satisfying approach. Beyond single- and two-point contacts, a distinction is made between tip and tangential contacts. It is shown that, in theory, these contact phases can be identified solely based on the support reactions, what is new in literature. In this way, multipoint contacts are reliably detected and filtered in order to discard incorrectly reconstructed contact points.

Highlights

Rats and mice use their vibrissae for tactile determination of object features, e.g., shapes and textures [1,2]
The biological principle of vibrissae frequently serves as a paragon developing tactile sensors, e.g., for object shape recognition
Deriving the modeling equations resulted in an ordinary differential equations (ODE)-system describing the deflection of the rod, where one equation depends on the contact scenario single- or two-point contact, respectively

Summary

Introduction

Rats and mice use their vibrissae for tactile determination of object features, e.g., shapes and textures [1,2]. The biological principle of vibrissae frequently serves as a paragon developing tactile sensors, e.g., for object shape recognition. Even though vibrissa-inspired sensors are nowhere near from the accuracy of conventional tactile sensors, such as coordinate measuring machines, they offer a number of benefits: Firstly, the universal applicability for the detection of different object features shows an important potential. Since most conventional sensors take advantage of stiff probes as force transmitters, allowing for an easy localization of objects in space, they are vulnerable to damage when accidentally colliding with an obstacle. Sweeping a long and flexible rod over an object’s surface by a single continuous movement of its base relative to the object, directly provides a large number of sensed points

Methods

Results

Conclusion