Two-layer sensor enables robotic fingertips to detect shear and slip
Layered e-skin for Shear Sensing
Robotics
Summary
Robots need to feel not just how hard they press but also when something slips or pushes sideways against their fingertips. The authors created a sensor with two stacked layers that can sense both pressure and sideways forces by measuring how the top and bottom layers move relative to each other. They used a special physics formula and a neural network to translate these movements into accurate sideways force readings. This sensor can also tell when an object is slipping, helping robots handle things more carefully.
What this means in practice
- •For robotics engineers: Enhance robotic fingertips to detect and track three-axis forces and slip events for improved manipulation.
- •For prosthetics designers: Develop prosthetic hands with improved tactile sensing that can recognize both pressure and shear forces for natural touch feedback.
Authors
Qingzheng Cong, Alexis W. M. Devillard, Abu Bakar Dawood, Xinxin Zhang, Wen Fan, Neri Niccolò Dei, Cem Suulker, Kaspar Althoefer, Etienne Burdet, Dandan Zhang
Abstract
This paper presents a stacked two-layer force-sensing resistor (FSR) array designed for robotic fingertips that combines high-resolution pressure mapping with shear-force estimation. A compliant lattice elastomer spacer converts shear loading into a measurable inter-layer displacement, producing relative center-of-pressure (CoP) shifts between layers. A physics-based moment balance links inter-layer CoP displacement to shear force, while an end-to-end CNN--GRU model captures nonlinear effects from load-dependent compression and contact redistribution. This model, with both layers as input, achieves coefficients of determination $R^2 = 0.914$ for $F_x$ and $R^2 = 0.944$ for $F_y$, consistently outperforming single-layer baselines for shear-force estimation. Robotic manipulation experiments show that, for contact-motion tracking, the deep layer tracks the translation and rotation imposed by the robot arm, whereas the superficial layer tracks the slip at the contact surface. Transient changes in the difference between the total pressure responses of the two layers provide the best slip-event detection performance among the tested cues. These results demonstrate that two-layer FSR arrays can provide three-axis force estimation, contact-motion tracking, and slip-event detection beyond conventional normal-force sensing.