Relationship Between Fabric Surface Properties And Friction-Induced Vibrations Of Human Finger Sliding Across Fabric

With the rapid development of mobile phones with touch screen and internet shopping, there has a great demand in the market for tactile rendering technology of fabrics. The fabric tactile rendering technology is able to meet consumer’s touch experience of fabrics during internet shopping. The existing tactile rendering system uses the tactile feedback device, which exerts vibration and force signals to human skin. The properties of the feedback stimulus are the key to achieve the real interactive experience by the operator in the virtual environments. To achieve fabric tactile rendering technology, it must identify the physical stimulus which can represent fabric properties and the interaction between fabric and skin.Previous studies show that the tactile perception of surface texture relies on temporal coding mechanism and spatial encoding mechanism, and these two mechanisms work on different frequency bandwidth of vibration signals. Existing research mainly focus on hard objects, particularly on the relationship between surface roughness and friction-induced vibrations. On textiles, the effect of structural parameters on the friction coefficient between fabric and skin has been investigated, but there has been little research about the relationship between friction-induced vibration and fabric properties, constructional and material.Fabric is a typical kind of deformable materials with rich textures. The interaction between human skin and fabric deforms the fabric, and the deformation is complex. Only the coefficient of friction is insufficient to characterize the material properties of fabric. Different vibration signals will be generated by human fingertip touching fabric surface with different properties, and evoke different tactile properties. Considering the virtual feedback stimulus of tactile feedback device must contain unique properties of fabric, which depend on structure parameters and materials, the reproduction of fabric tactile sensation needs to find virtual stimulus which can characterize structure parameters and materials. Once the vibration signals have been determined, the generated virtual feedback stimulus make human feel the unique tactile of fabric.From the above analysis, this study has explored the vibration signals characterizing fabric properties accurately, and the details are followed.(1) This study has used friction-induced vibrations of human finger sliding across fabric, calculated vibration frequency and vibration amplitude, and explored the relationship between the fabric structure parameters and the friction-induced vibrations. The results showed that fabric structure parameters can be characterized by different vibration features.To identify the relationship between the fabric structure parameters and the friction-induced vibrations, the accelerometer was used to measure the vibrations induced by the relative motion between fingertip and fabric surfaces. Firstly, the Fast Fourier transformation was used to analyze the friction-induced vibration signal and extracted several spectral components. Secondly, the Lin’s consistency coefficients with the constructional parameters were calculated. Finally, the analysis of variance was used to scope the effect of fabric structure parameters on vibration indicators. The results showed that the relative motion between fingerpad and fabrics generated full vibration signals, and the vibration spectral components can be used to represent the fabric structure parameters.(2) Vibration energy of multi-harmonic components from vibration spectrum was extracted to identify the relationship between fabric material and the friction-induced vibrations. The results showed that vibration energy of multi-harmonic components can represent the changes in the textile material, but cannot distinguish subtle changes of similar materials.To identify the relationship between fabric material and the friction-induced vibrations, we use cotton, modal, polyester, silk and T/R to design five fabric samples which have the same constructional parameters. The vibration energy of multi-harmonic components from vibration spectrum induced by fabric/skin frictions was extracted. Then the analysis of variance was used to judge whether the vibration energy of multi-harmonic components can reflect textile material changes. The results showed that the area covered by three harmonics can distinguish fabrics made of cellulose fibers from fabrics made of other fibers, but it cannot distinguish fabrics made of fibers with similar friction properties.In conclusion, the vibration spectral components can be used to represent the design parameters and textile material changes. However, the extracted spectral indicators in this study cannot distinguish the structure or material properties of all fabrics.