A Robotic Skin Using Low-density FBGs for Human-robot Interaction

In collaborative robotic arms, tactile sensing is crucial for enhancing interaction accuracy and safety. Robotic skins play an vital role in tactile sensing by mimicking the human sense of touch, enabling robots to detect and respond to physical interactions. Fiber Bragg gratings (FBGs), with their high sensitivity, environmental adaptability, and real-time response are increasingly adopted in the design of robotic skin systems. However, current FBG-based research has not resolved the issue of the high-density FBG usage and the large number of optical fibers required, limiting their widespread application in practical scenarios. In this work, we present a design of a soft robotic skin with efficient use of FBGs to estimate the location and magnitude of external forces. Our prototype features a cylindrical shape with a total area of 720 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and incorporates one optical fiber with 16 evenly spaced FBGs. We optimized the structure through finite element analysis (FEA) and designed experiments to characterize its properties. Using data-driven methods, we achieved root mean square errors (RMSEs) of 4.29 mm and 4.05 degrees in estimating locations along the axial and radial directions, respectively, and 0.17 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$N$</tex> for force magnitude. By achieving high sensitivity and an effective area per unit of 50 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>, this approach shows promise for future applications in robotic skin.