Identifying Contact Distance Uncertainty in Whisker Sensing with Tapered, Flexible Whiskers

Whisker-based tactile sensors have the potential to perform fast and accurate 3D mappings of the environment, complementing vision-based methods under conditions of glare, reflection, proximity, and occlusion. However, current algorithms for mapping with whiskers make assumptions about the conditions of contact, and these assumptions are not always valid and can cause significant sensing errors. Here we introduce a new whisker sensing system with a tapered, flexible whisker. The system provides inputs to two separate algorithms for estimating radial contact distance on a whisker. Using a Gradient-Moment (GM) algorithm, we correctly detect contact distance in most cases (within 4% of the whisker length). We introduce the Z-Dissimilarity score as a new metric that quantifies uncertainty in the radial contact distance estimate using both the GM algorithm and a Moment-Force (MF) algorithm that exploits the tapered whisker design. Combining the two algorithms ultimately results in contact distance estimates more robust than either algorithm alone.

I. Introduction

Many rodents navigate dark spaces using rhythmic protraction and retraction of their whiskers, a behavior called “whisking.” The ability to navigate and develop a three-dimensional (3D) map even in darkness [1]–[3] has inspired engineered whisker arrays that can do the same. The most effective whisker arrays can identify the contact point along the whisker's length to create 3D scene maps [2]. In application, such arrays have mapped the fine details of a 3D face model [4], classified objects [5], defined shapes [6]–[8] and performed SLAM in a 3D scene [3].