Sensing and Control of Friction Mode for Contact Area Variable Surfaces (Friction-variable Surface Structure)

TL;DR

This paper introduces a novel contact area variable surface (CAVS) with controllable friction modes, enabling robotic grippers to switch between sliding and grasping, enhancing manipulation capabilities.

Contribution

The study presents a new sensible CAVS with friction anisotropy analysis, sensing, and control systems for mode switching in robotic grasping applications.

Findings

CAVS exhibits significant friction anisotropy, especially in the longitudinal direction.

The gripper successfully switches between sliding and grasping modes using friction control.

Experimental validation confirms effective manipulation using the developed CAVS system.

Abstract

Robotic hands with soft surfaces can perform stable grasping, but the high friction of the soft surfaces makes it difficult to release objects, or to perform operations that require sliding. To solve this issue, we previously developed a contact area variable surface (CAVS), whose friction changed according to the load. However, only our fundamental results were previously presented, with detailed analyses not provided. In this study, we first investigated the CAVS friction anisotropy, and demonstrated that the longitudinal direction exhibited a larger ratio of friction change. Next, we proposed a sensible CAVS, capable of providing a variable-friction mechanism, and tested its sensing and control systems in operations requiring switching between sliding and stable-grasping modes. Friction sensing was performed using an embedded camera, and we developed a gripper using the sensible CAVS, considering the CAVS friction anisotropy. In CAVS, the low-friction mode corresponds to a small grasping force, while the high-friction mode corresponds to a greater grasping force. Therefore, by controlling only the friction mode, the gripper mode can be set to either the sliding or stable-grasping mode. Based on this feature, a methodology for controlling the contact mode was constructed. We demonstrated a manipulation involving sliding and stable grasping, and thus verified the efficacy of the developed sensible CAVS.