Haptic Perception of 2D Equilateral Geometric Shapes via Electrovibration on Touch Screen

Haptic feedback is a potential technology to convey spatial, graphical, or pictorial information to visually impaired people that is difficult to be transmitted verbally. In this study, we investigated the effects of edge number (N) and rendering technique on haptic recognition of two-dimensional (2D) equilateral geometric shapes displayed by electrovibration on touch screens. We conducted experiments with 9 subjects using 5 shapes (triangle, square, pentagon, hexagon, and octagon) under 3 different experimental conditions; 1) electrovibration was displayed inside the shapes (INSIDE condition), 2) on their edges (EDGE condition), and 3) at the outside of the shapes (OUTSIDE condition). We observed that haptic recognition accuracy of the subjects decreased as the number of edges was increased from N=3 (triangle) to N=6 (hexagon). Surprisingly, the recognition accuracy for the octagon (N=8) was significantly higher than that of the hexagon. The results also showed that there was no significant difference in rendering techniques in terms of the recognition rates, but displaying electro vibration inside the shapes (INSIDE condition) led to the shortest duration of haptic recognition.