Extrinsic Contact Sensing with Relative-Motion Tracking from Distributed Tactile Measurements

TL;DR

This paper presents a method for localizing external contacts of grasped objects using distributed tactile sensors, leveraging object motion constraints to improve contact detection in manipulation tasks.

Contribution

It introduces a constraint-based estimation framework that utilizes distributed tactile measurements to localize extrinsic contacts, contrasting with traditional force/torque sensing methods.

Findings

Validated in simulation and real experiments

Effective in localizing fixed point and line contacts

Highlights the advantages of distributed tactile sensing

Abstract

This paper addresses the localization of contacts of an unknown grasped rigid object with its environment, i.e., extrinsic to the robot. We explore the key role that distributed tactile sensing plays in localizing contacts external to the robot, in contrast to the role that aggregated force/torque measurements play in localizing contacts on the robot. When in contact with the environment, an object will move in accordance with the kinematic and possibly frictional constraints imposed by that contact. Small motions of the object, which are observable with tactile sensors, indirectly encode those constraints and the geometry that defines them. We formulate the extrinsic contact sensing problem as a constraint-based estimation. The estimation is subject to the kinematic constraints imposed by the tactile measurements of object motion, as well as the kinematic (e.g., non-penetration) and possibly frictional (e.g., sticking) constraints imposed by rigid-body mechanics. We validate the approach in simulation and with real experiments on the case studies of fixed point and line contacts. This paper discusses the theoretical basis for the value of distributed tactile sensing in contrast to aggregated force/torque measurements. It also provides an estimation framework for localizing environmental contacts with potential impact in contact-rich manipulation scenarios such as assembling or packing.