The Spatial Spectrum of Tangential Skin Displacement Can Encode Tactual Texture

Abstract

Abstract-The tactual scanning of five naturalistic textures was recorded with an apparatus capable of measuring the tangential interaction force with a high degree of temporal and spatial resolution. The resulting signal showed that the transformation from the geometry of a surface to the force of traction, and hence to the skin deformation experienced by a finger is a highly nonlinear process. Participants were asked to identify simulated textures reproduced by stimulating their fingers with rapid, imposed lateral skin displacements as a function of net position. They performed the identification task with a high degree of success, yet not perfectly. The fact that the experimental conditions eliminated many aspects of the interaction, including low-frequency finger deformation, distributed information, as well as normal skin movements, shows that the nervous system is able to rely on only two cues: amplitude and spectral information. The examination of the "spatial spectrograms" of the imposed lateral skin displacement revealed that texture could be represented spatially despite being sensed through time and that these spectrograms were distinctively organized into what could be called "spatial formants". This finding led us to speculate that the mechanical properties of the finger enables spatial information to be used for perceptual purposes in humans without any distributed sensing, a principle that could be applied to robots.

Natural scenes in tactile texture

“…Our methods to measure and analyze textureelicited vibrations will help guide attempts to render virtual textures (e.g., Chubb et al 2010;Romano and Kuchenbecker 2012;Wiertlewski et al 2011b). Furthermore, our results suggest that the biomechanical properties of the skin and the geometry of individual fingerprints, rather than texture properties alone, need to be taken into account when attempting to replicate textures that feel natural.…”

Wearable finger pad deformation sensor for tactile textures in frequency domain by using accelerometer on finger side

“…The skin deformation includes the wide range of frequency components as observed in another study [13]. The deformation for the grating scales, which have a surface roughness that is larger than both the cloth and aluminum, is greater than those for the cloth and aluminum.…”

“…Many researchers measured the interaction force between the fingertip and material surfaces as reliable information related to the finger pad's deformation because the forces cause the skin to deform [13][14][15][16][17][18][19]. For example, Wiertlewski et al [13] precisely measured the interaction forces when a material slid beneath a fingertip.…”

“…For example, Wiertlewski et al [13] precisely measured the interaction forces when a material slid beneath a fingertip. However, they all measured interaction forces that were distinct from the skin deformations.…”

Compressibility and Crushability Reproduction through an Amorphous Haptic Interface

“…While the reproduction of the oscillatory components alone via hard surfaces may be sufficient to determine vivid perceptual outcomes [8,9], another haptic simulation approach, proposed here, involves the artificial reproduction of the sensory experiences resulting from squeezing actions performed via a deformable haptic interface. This can reproduce a range of mechanical responses, e.g.…”