Contact forces and skin deformation induced during tactile exploration have been investigated in the frequency domain to understand finger–material interaction. Their power spectra are one of the representative feature quantities that have been associated with the surface properties of materials. However, thus far, the phase information of these quantities has not been studied. Furthermore, most previous studies focused on uni-dimensional signals such as forces in either the normal or tangential directions. We investigated the phase differences between normal and shear forces induced during tactile exploration. The results showed that the phase differences between these two axial forces differ among materials and that they exhibit features different from their power spectra. These results indicate that the phase difference between two axial forces should be taken into account to understand the finger–material interactions during tactile exploration.

中文翻译：

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触觉探索过程中法向力和剪切力之间的相位差代表了纹理特征

已经在频域中研究了触觉探索过程中引起的接触力和皮肤变形，以了解手指与材料的相互作用。它们的功率谱是与材料表面特性相关的代表性特征量之一。然而，到目前为止，还没有研究这些量的相位信息。此外，以前的大多数研究都集中在单维信号上，例如法向或切线方向的力。我们研究了触觉探索过程中引起的法向力和剪切力之间的相位差异。结果表明，这两种轴向力之间的相位差因材料而异，并且它们表现出与其功率谱不同的特征。