# Shear-invariant Sliding Contact Perception with a Soft Tactile Sensor

## TL;DR

This paper introduces a shear-invariant tactile perception method using PCA with a soft sensor, enabling robots to accurately perceive objects during continuous contact and sliding, demonstrated through successful contour-following tasks.

## Contribution

The novel shear-invariant perception approach effectively handles sliding contact, improving tactile perception in continuous manipulation tasks.

## Key findings

- Method successfully traces contours on various objects
- Demonstrates generalization to different curvatures
- Enables robust perception during sliding contact

## Abstract

Manipulation tasks often require robots to be continuously in contact with an object. Therefore tactile perception systems need to handle continuous contact data. Shear deformation causes the tactile sensor to output path-dependent readings in contrast to discrete contact readings. As such, in some continuous-contact tasks, sliding can be regarded as a disturbance over the sensor signal. Here we present a shear-invariant perception method based on principal component analysis (PCA) which outputs the required information about the environment despite sliding motion. A compliant tactile sensor (the TacTip) is used to investigate continuous tactile contact. First, we evaluate the method offline using test data collected whilst the sensor slides over an edge. Then, the method is used within a contour-following task applied to 6 objects with varying curvatures; all contours are successfully traced. The method demonstrates generalisation capabilities and could underlie a more sophisticated controller for challenging manipulation or exploration tasks in unstructured environments. A video showing the work described in the paper can be found at https://youtu.be/wrTM61-pieU