Teacher-Informed Tactile Sensing Upgrade for Child–Robot Physical Interaction: A Comparison of Velostat and FBG Sensors
Social robots designed to engage with children require additional co-designed features that reflect authentic interactions. Physical human robot interaction (pHRI) in this application requires tactile sensors that are reliable and safe for natural children’s touch. This work reports on the design and assessment of two tactile sensing systems—one using Velostat and the other based on optical sensing—developed in line with teacher feedback to enhance the integration of the CASTOR robot into educational activities. Both sensors were characterized under controlled forces representative of human touch. The Velostat sensor exhibited a nonlinear force response, higher spatial resolution, and lower hysteresis, while the optical sensor demonstrated a highly linear response and greater sensitivity. The sensing systems were subsequently evaluated with 5 participants (25.73 ± 8.32 years) in a hand-shaking pHRI task. A heatmap-based analysis revealed that both sensors effectively captured the temporal and spatial distribution of contact forces, while also highlighting qualitative differences in localized forces among participants, with a maximum exerted force of 1.30 N. Overall, the results indicate that the Velostat-based sensor is advantageous for the educational scenario, as it provides detailed contact localization, exhibits low hysteresis, is more robust, and is replicable.