An Origami-Inspired Variable Friction Surface for Increasing the Dexterity of Robotic Grippers

TL;DR

This work tackles the challenge of limited in-hand manipulation in two-finger grippers by introducing an origami-inspired variable friction (O-VF) surface that can switch between high and low friction states. The surface uses a deformation-limited accordion fold to expose two contact surfaces controlled by a single actuator, and its design is made parametric to optimize friction modulation and thickness changes. Through finite-element analysis, material testing, and a tendon-driven prototype, the authors demonstrate improved translation and rotation capabilities across multiple objects, with unit-density and pattern density emerging as key determinants of performance and reliability. The proposed approach offers a compact, manufacturable epidermis for robotic fingers that enhances dexterity without adding substantial control complexity, and lays the groundwork for closed-loop control and tactile sensing integration in future work.

Abstract

While the grasping capability of robotic grippers has shown significant development, the ability to manipulate objects within the hand is still limited. One explanation for this limitation is the lack of controlled contact variation between the grasped object and the gripper. For instance, human hands have the ability to firmly grip object surfaces, as well as slide over object faces, an aspect that aids the enhanced manipulation of objects within the hand without losing contact. In this letter, we present a parametric, origami-inspired thin surface capable of transitioning between a high friction and a low friction state, suitable for implementation as an epidermis in robotic fingers. A numerical analysis of the proposed surface based on its design parameters, force analysis, and performance in in-hand manipulation tasks is presented. Through the development of a simple two-fingered two-degree-of-freedom gripper utilizing the proposed variable-friction surfaces with different parameters, we experimentally demonstrate the improved manipulation capabilities of the hand when compared to the same gripper without changeable friction. Results show that the pattern density and valley gap are the main parameters that effect the in-hand manipulation performance. The origami-inspired thin surface with a higher pattern density generated a smaller valley gap and smaller height change, producing a more stable improvement of the manipulation capabilities of the hand.

Figures (11)

• Figure 1: Two-fingered two-degree-of-freedom gripper with fingers using the proposed origami-inspired variable friction (O-VF) surface. The controlled states of low friction (left finger) and high friction (right finger) are depicted, demonstrating the varying contact surfaces (black arrows).
• Figure 2: Specifications of the folding pattern, defining the area ratio of variable friction surfaces and change in thickness between modes: (a) high friction and (b) low friction.
• Figure 3: Surface plot showing the relationship between the length of low friction area (l), the folding angle ($\alpha$), and change in thickness of the overall structure between friction modes ($\Delta$h).
• Figure 4: Static simulation of the deformation required to fully fold each design with $\alpha$ at values (a) 10° , (b) 20° , and (c) 30° . The resultant force (N) required to fully fold each specification is also shown. Simulation surface colours indicate the observed stress on the thermoplastic polyurethane (TPU) material.
• Figure 5: Section view of the CAD model finger showing the actuation method and tendon routing on the rear of the O-VF surface.