Abstract
The aim of this study is to derive a design index for a tactile perception of covexoconcave. We hypothesized that interval between convex patterns affects the perception of covexoconcave as well as its height. In addition to surface texture, we assumed that touching conditions such as contact pressure, and relative velocity between a fingertip and a surface force have an influence on the tactile perception. It is known that the vibrations generated from a combination of relative velocity and the intervals between convex patterns affect roughness perception. To verify the hypothesis, we conducted a set of experiment with participants. We prepared a set of plastic plates having vertical grooves on their surfaces. Each sample differs in terms of the groove depth and intervals. The experiment consists of two phases. In the first phase, we asked participants to assess the degree of convexoconcave using their index fingers for each sample under a condition of back-and-forth motion with different contact pressures and relative speeds. We used a belt conveyor to move the sample under certain speed. From the results of experiment, we found significant effects of intervals of the convex patterns, groove depth height, and the fingertip force on the perception of covexoconcave. This results imply that a designer can manipulate tactile sense of convexoconcave not only by groove depth but groove width. In the second phase, we investigated the effects of frequency band of vibration occurred between the fingertip and the surface. To achieve low-pass and high-pass filters during a reciprocating finger movement, we masked certain parts of the sample's surface. For example, we masked the middle part for low-pass and both end for high-pass. From the result of participants' assessments, we found that the effect of less than 70 Hz vibrations on the covexoconcave perception was prominence.
