Pile Surface Tactile Simulation: Role of the Slider Shape, Texture Close to Fingerprints, and the Joint Stiffness

Stimulating the human hand with a tactile device in order to simulate pile fabric touch is a challenge. The stimulation has to be designed from the friction characteristics of the investigated pile surfaces, i.e. velvet fabrics. The tactile illusion of pile is given when touching the smooth plate of the tactile stimulator STIMTAC by modulating the coefficient of friction between the plate and the finger during an active movement. In a preliminary study, five tribological features as velvet fabric characteristics were identified, used for the design of the stimulator’s control signal, and validated via psychophysical studies where real and simulated fabrics were compared. But a specific tribological feature described and expected by individuals was missing. Then, a tribological investigation has been done in order to obtain this tribological feature, with the five previous ones, by changing experimental conditions: slider shape, texture, and joint stiffness. The obtained results show that a rounded shape of the slider has an influence only on the friction force level, but a texture of the slider close to fingerprints and a joint stiffness is crucial to obtain the missing characteristic and therefore for the pile surface tribological characterization. The role of the fingerprints in touching grooved surfaces has been published before but not for pile surfaces.