CapTac: Robust Capacitive Sensing for Distributed Force Mapping in Parallel Robotic Grasping

For reliably grasping sensitive and delicate objects, measuring the distribution of normal and shear forces across contact areas is crucial-particularly for slip detection and preventing damage of delicate objects. This necessitates sensors that are easily integrated into robotic fingers (small form factor), durable and/or easily replaceable, adaptable to various gripper designs, and suitable for low-cost, high-volume production. We propose addressing these challenges with interchangeable, wireless capacitive tactile sensor arrays capable of measuring both normal and shear force distribution within a robotic finger. These sensors utilize an affordable manufacturing process based on conductive textile electrodes. We analyze a triangular electrode pattern design and compare the impact of three different types of electromagnetic shielding, which is essential for minimizing the influence of external disturbances. Experimental evaluation, including bench testing and robotic grasping experiments alongside using commercially available reference sensors, demonstrates that these sensors-despite their simplicity-achieve good correlation between applied forces and sensor response, exhibiting low hysteresis and minimal degradation over repeated use. Consequently, we anticipate these sensors will enable adaptive grasp control for improved stability.