Sanal dokuların ultrasonik eyleme tekniği ile titretilen bir ekranda dokunsal görüntülenmesi

To render tactile cues on a touchscreen by friction modulation, it is important to understand how human perceive a change in friction. This thesis aims to explore the tactile perception of changes in friction (called edges), and underlying perceptual mechanism. We first estimated the perceptual thresholds to detect a virtual edge, rendered by rising friction (RF) and falling friction (FF), while finger is sliding on the touch surface. Then, we conducted intensity scaling experiments and investigated the effect of finger sliding velocity, normal force, and rise/fall time of vibration amplitude (transition time) on the perceived intensity of a virtual edge. In order to better understand the role of contact mechanics, we also looked into the correlations between the perceived intensities of subjects and several parameters involved in contact. The results of our experiments showed that the contrast and rate of change in tangential force were best correlated with the perceived intensity. The subjects perceived RF more strongly than FF, particularly at higher tangential force contrast. The results also showed that transition time and normal force have significant effect on our tactile perception. In the second part, we investigated our ability to discriminate two consecutive edges, followed by discrimination and roughness perception of multiple edges (called periodic gratings). The results showed that discrimination of two consecutive edges was significantly influenced by edge sequence: FF followed by RF was discriminated more easily than the reverse order. On the other hand, periodic gratings generated by displaying consecutive edge sequence of FF followed by RF were perceived with the same acuity as compared to vice versa. We found that a relative difference of 14% in spatial period was required to discriminate two periodic gratings independent of the edge sequence. Moreover, the roughness perception of periodic gratings decreased with increasing spatial period for the range that we have investigated (spatial period > 2 mm), despite the lack of spatial cues on texture height. We also observed that rate of change in friction coefficient was better correlated with the roughness perception than the friction coefficient itself. These results will further help to understand and design of virtual textures for touch surfaces.