On the Role of Friction Vibrations for Tactile Perception of Periodic and Complex Surfaces

Tactile perception originates from the scanning of the fingertip on object surfaces (haptic sensing). Vibrations induced by the sliding contact activate the receptors (mechanoreceptors) located in the skin, allowing the brain to identify objects and perceive information about their surfaces. While the correlation between surface roughness and tactile sensation has often been investigated in literature, the spectra of the vibrations induced by the finger-surface scanning are rarely mentioned. The aim of this work is to focus on such induced vibrations, which are hold to be responsible of the tactile perception. An experimental set-up, named TRIBOTOUCH, is developed to recover the vibration dynamics by detecting the contact force and the induced vibrations at the finger nail; the test bench, based on a compliant kinematical system, has been designed and validated to guarantee the measurements of low amplitude of the vibrations of interest, and to perform measurements without introducing external noise. Experimental campaigns characterizing the vibration spectra with respect to scanning speed and surface roughness are presented and the role of fingerprints on the duplex model of tactile perception is highlighted. The spectra of the induced vibrations generated by the touching of a textile is presented and linked to the textile features.