Compliant multi-layer tactile sensing for enhanced identification of human touch

Tactile sensing is of interest for facilitating interactions between robots and humans. To aid the robot's interpretation of human contact, the use of a multi-layer cutaneous tactile sensing architecture that can provide more information and an expanded force sensing range was explored, revealing differences in the signal generated by a machine versus a human. The multi-layer system consisted of two stretchable sensing skins alternating with two foam layers of different stiffness. When human touch was compared with machine indentation, a large variability in human touch was found. Thus, although the topmost skin, placed over a soft foam, was able to better recognize light contacts, a second underlying skin, placed over a harder foam, was required to gauge stronger human contacts. Out-of-plane touch modalities, such as tapping and punching, could be identified using strip-shaped skins having just two electrodes. To provide distributed sensing, the technique of electrical impedance tomography was employed with the multi-layer architecture using larger-area skins having electrodes around the perimeter. Distributed touch modalities, such as multi-point finger presses and sliding, were distinguished from single-point pressing. The distributed multi-layer sensing system also had the ability to assess higher-force touches.