Flexible and Wireless Normal‐Tangential Force Sensor Based on Resonant Mechanism for Robotic Gripping Applications

Abstract The ability to detect both normal and tangential forces is essential for robotic tactile systems, while most available sensors implement this function at the cost of complex electrode structure and wiring. Here a fully flexible sensor for wireless detection of normal and tangential force based on resonant mechanism is reported. The components of the sensor are designed and optimized to meet the requirement, and the sensor shows good sensitivity, hysteresis characteristics, response time, and stability in the wired test. Wireless operation is carried out through inductive coupling, and the collected spectrum of reflection coefficient can reflect both normal force and tangential force information. In the case of individual input, the sensitivity is −0.19 MHz kPa −1 to normal force in the range of 0–200 kPa, and −0.031 dB kPa −1 to tangential force in the range of 0–50 kPa. As proofs of concept, maximum static friction coefficient tests and robotic gripping experiments are demonstrated for preliminary determination of surface roughness and material identification respectively. In particular, a total recognition accuracy of 92.5% is achieved by random forest‐based machine learning for balls with different materials in the gripping experiment.