Stable robotic grasping requires continuous contact force monitoring to prevent slippage or damage during tasks like pick-and-place. Variations in grasp points, object dynamics, and harsh environments challenge existing tactile sensors, which often lack sensitivity or durability. While force and form closure ensure object stability, adaptable solutions remain limited. The HARTU project develops modular, high-sensitivity, low-latency Fiber Bragg Grating (FBG)-based sensors for industrial grippers, enabling real-time grasp quality control.

FBG sensors employ optical fibers with tiny patterns that reflect specific light wavelengths. Shifts in these wavelengths, caused by strain or temperature changes, provide precise measurements. Lightweight, interference-resistant, and suited for tough industrial settings, FBGs deliver reliable data for repetitive tasks like object manipulation, enhancing safety and efficiency.

The HARTU project designs reconfigurable robotic systems to optimise production lines. By studying five industrial use cases, it advances object manipulation across diverse shapes, materials, and sizes using AI-driven solutions. This versatility demands innovative grasping technologies, such as vacuum and finger grippers, with a focus on contact material selection, sensor architecture, and integration into existing or new grippers.

HARTU is developing three FBG-integrated grippers: vacuum grippers for TCA, TOFAS, and ULMA order preparation, and two finger gripper variants, silicone patches and embedded structures, for PCL, TOFAS kitting, and INFAR. Below, we discuss material selection and vacuum gripper test results.

• Material selection: experimental tests evaluated materials for FBG sensor integration. Shore 55 material outperformed Shore 28, offering higher resolution, consistent force profiles over eight cycles, and similar settling noise upon object contact. Sensors showed uniform recovery times and consistent performance across force levels. Hardness significantly affects sensitivity and coverage, with sensors detecting both local and global forces. Strong linearity between applied forces and wavelength shifts was observed. Future work will explore global sensor localisation, cost reduction, and temperature effect mitigation.
• Integrated vacuum gripper: a silicone vacuum gripper with embedded FBG sensors was tested for grasp quality monitoring. It tracks forces based on vacuum levels and object weight, detecting instability – especially for weights above 750 grams – with clear signal changes. The sensor’s response is linear with vacuum level but nonlinear with weight, varying by vacuum setting. This technology enables simpler grippers to perform precise tasks.

Ongoing tests will continue refining these systems for HARTU’s final demonstrators, advancing robotic grasping for industrial applications.